Spawn

SPAWN - Cobalt Strike BOF

Cobalt Strike BOF that spawns a sacrificial process, injects it with shellcode, and executes payload. Built to evade EDR/UserLand hooks by spawning sacrificial process with Arbitrary Code Guard (ACG), BlockDll, and PPID spoofing.

• Due to ACG, this does not support shellcode which is dependent on these fuctionalities:
  • Toggling memory permissions between RW/RX.
  • RWX memory
• To inject shellcode into a spawned process that is dependent on the above functionilities please see the Hollow BOF project
• For an awesome explaination on ACG please see Adam Chestner's blog below.

New Features (08/01/2021)

• Spawn sacrificial process with Arbitrary Code Guard (ACG) to prevent EDR solutions from hooking into sacrificial process DLL's.
  • See Adam Chester's "Protecting Your Malware" blog for full details. This part of the BOF is derived from his work.
• Inject & Execute shellcode.

Popin' Calc from ACG Protected Process

beacon> spawn notepad.exe 6248 /Users/bobby.cooke/git/boku7/SPAWN/popCalc.bin
[*] SPAWN (Bobby Cooke//SpiderLabs|@0xBoku|github.com/boku7)
[+] Opened handle 0x534 to process 6248(PID)
[+] Spawned process: notepad.exe | PID: 8404 | PPID: 6248
[+] Allocated RE memory in remote process 8404 (PID) at: 0x00000177A72C0000
[+] Wrote 280 bytes to memory in remote process 8404 (PID) at 0x00000177A72C0000
[+] APC queued for main thread of 8404 (PID) to shellcode address 0x00000177A72C0000

New Features (07/19/2021)

• CNA Agressor Script interface

beacon> help
    spawn                     Spawn a process with a spoofed PPID and blockDll
beacon> help spawn
Synopsis: spawn /path/to/exe PPID
beacon> ps
8264  5536  OneDrive.exe                 x86   1           DESKTOP-KOSR2NO\boku 
beacon> spawn cmd.exe 8264
[*] SPAWN (@0xBoku|github.com/boku7)
Opened handle 0x634 to process 8264(PID)
Success! Spawned process: cmd.exe | PID: 5384 | PPID: 8264

• PPID Spoofing
• Cobalt Strike "like" blockdll functionality

Compile with x64 MinGW:

x86_64-w64-mingw32-gcc -c spawn.x64.c -o spawn.x64.o

Run from Cobalt Strike Beacon Console

• After compile import the spawn.cna script into Cobalt Strikes Script Manager

beacon> spawn /path/to/exe PPID /local/path/to/shellcode.bin

To Do List

• ~Agressor script for better end user experience~
  
• ~PPID spoofing for better parent-child process relation OPSEC~
  
  • Here we can see our cmd.exe process being spawned with the PPID as OneDrive.exe
• ~implement Cobalt Strike blockdll functionality to prevent non-MS signed DLLs from loading into the spawned processes memory~
  
  • We see the parent-child process relationship, and that our spawned process has been created with the Signatures restricted (Microsoft only)
  • The Signatures restricted (Microsoft only) makes it so DLL's not signed by Microsoft cannot be loaded into our spawned process
• ~~Do not crash the beacon process when the PE file does not exist~~
  
  • No longer crashes on process creation failure!
• ~Return the PID to the Cobalt Strike console when the new process is spawned~
  
• ~Build out different methods of remote process injection~ (08/01/21)
• Build out different methods of remote process patching
  • NTDLL.DLL remote process Unhooking
  • ETW remote process Patching/Bypass
  • AMSI remote process Patching/Bypass
  • CLR Loading & .Net assembly injection

Why did I build this?

1. To learn more about Cobalt Strike BOFs

2. I want flexibility in choosing my sacraficial processes.

• Spawning the same process for every fork-and-run seems like bad/predictable OPSEC to me.
• There are probably methods for this out there or built into CS already. Either way, I wanted to build my own.

3. I have allot of cool BOF ideas that I want to build on this.

Credits / References

PPID Spoofing & blockDll functionality

• Credit/shoutout to: Adam Chester @_xpn_ + @SEKTOR7net + Raphael Mudge
• Thank you for the amazing work that you've contributed. I would not be able to publish this without your blogs, videos, and awesome content!
• Main References for PPID Spoofing & blockdll
  • https://blog.xpnsec.com/protecting-your-malware/
  • https://blog.cobaltstrike.com/2021/01/13/pushing-back-on-userland-hooks-with-cobalt-strike/
  • https://institute.sektor7.net/ (Courses)

Raphael Mudge - Beacon Object Files - Luser Demo

• https://www.youtube.com/watch?v=gfYswA_Ronw

Cobalt Strike - Beacon Object Files

• https://www.cobaltstrike.com/help-beacon-object-files

BOF Code References

anthemtotheego/InlineExecute-Assembly

• https://github.com/anthemtotheego/InlineExecute-Assembly/blob/main/inlineExecuteAssembly/inlineExecute-Assembly.cna

ajpc500/BOFs

• https://github.com/ajpc500/BOFs/

trustedsec/CS-Situational-Awareness-BOF

• https://github.com/trustedsec/CS-Situational-Awareness-BOF

Sektor7 Malware Dev Essentials course - learned how to do the early bird injection technique

• https://institute.sektor7.net/red-team-operator-malware-development-essentials