Cobaltstrike UDRL
Feature :
- Redirect all WININET call over callstack crafting
- Encrypt beacon during sleep
- Encrypt beacon heap during sleep
- Self delete of loader
Callstack exemple :
CreateThread :
InternetOpenA :
WaitForSingleObject :
1 - Create heap for beacon usage
2 - Allocation of RWX area with beacon size + UDRL size
3 - Copy the UDRL at the end of beacon in allocated area
| 0x00 | beacon | 0xBEACON_SIZE | UDRL | 0xEND_Alloc
4 - Copy the ODIN structure (heap handle, beacon addr, alloc size) to the start of allocated area (no pe header is present)
5 - Copy beacon section
6 - Resolve beacon import and patch IAT (also set hook)
7 - Patch relocation table
8 - Init the beacon
9 - Create thread on TpReleaseCleanupGroupMembers+0x450 to spoof the thread start addr & beacon run
10 - Self delete the loader
-
All WININET function is hooked and use callstack crafting for all wininet call
-
Sleep is hooked :
1 - XOR the heap (random key for each sleep)
2 - Encrypt the beacon + udrl (remember he was copied at the end of beacon) with KrakenMask (ropchain, rwx->rw, encrypt, sleep, rw->rwx)
3 - XOR the heap
-
ExitThread is hooked :
1 - Destroy the beacon heap
2 - Free the memory region with the beacon
3 - Exit thread
Compile the loader and load the cna script (odin.cna)
About the cna, you need to edit path of variable $loader_path at line 11 & 38
http-beacon {
set library "wininet";
}
stage {
set smartinject "false";
set sleep_mask "false";
}
It's a POC, be carreful is you use this UDRL
If you have crash, you can dm on twitter or open github issues, please send :
- Cobaltstrike profil
- Debugger screen with callstack
You need to have python on you're windows machine, you have post-ex build to run python script.
Python script use sys and pefile
Moneta :
Pe-Sieve :
HuntSleepingBeacons :
For code :
- Callstack craffting : https://github.com/susMdT/LoudSunRun
- Some parts of code : https://www.cobaltstrike.com/product/features/user-defined-reflective-loader
For idea :
- AceLdr : https://github.com/kyleavery/AceLdr
- BokuLdr : https://github.com/boku7/BokuLoader
- KaynStrike : https://github.com/Cracked5pider/KaynStrike
Thanks to :
- chatGPT, Bakki, Caracal & CobaltAD : For debug and somes help