NimlineWhispers

A very proof-of-concept port of Outflank's InlineWhispers tool, adapted to output inline assembly for Nim projects.

This uses the same process of taking output from SysWhispers, but also parses the Syscalls.h file to include function return types and arguments in the outputted inline assembly.

How do I set this up?

This is basically the same as InlineWhispers, but including for completeness.

• (Optionally) Install SysWhispers
  • git clone https://github.com/jthuraisamy/SysWhispers.git
  • cd SysWhispers
  • pip3 install -r .\requirements.txt
  • py .\syswhispers.py --versions 7,8,10 -o syscalls was used to generate the included syscalls.asm and syscalls.h.
• Clone this repository.
• Update which functions are required in functions.txt to include only necessary functions from syscalls.asm.
• Run the python3 NimlineWhispers.py command (additional flags listed below) to generate the inline assembly (syscalls.nim) file - example in the repo.
• Add include syscalls to your Nim project.

An example of integrating NimlineWhispers output with your project can be seen in this blog.

Randomised Function Names

To evade detection based on the presence of function names in our Nim executables (as outlined in @ShitSecure's blog here), NimlineWhispers can be run with a --randomise flag, as follows:

python3 NimlineWhispers.py --randomise


             %              ..%%%%%#               %/.                  
           /%%%%%,.%%%%%%%%%%%%%%%%%%%%%%%%%%%%.%%%%%%                  
       . #%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%.               
  %%*.%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% ,%%         
   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%.         
    #%%%%%%%%%%%%%%.                         %%%%%%%%%%%%%%%%           
      %%%%%%%(                                     %%%%%%%%%            
    &   %%#                                           .%%  ..           
     &&.                          .                     . #&            
      &&&&.               . %&&&&&&&&.                 &&&&             
       &&&&&&&.. .   . (&&&&&&&&&&&&&&&&&%. .     .&&&&&&&              
       .%&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&               
         #&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&                
           ,&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&                  
               &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&                     
                   &&&&&&&&&&&&&&&&&&&&&&&&&&&                          
                            %&&&&&&&&.                                  
                                                NimlineWhispers
                                                @ajpc500 2021

[i] in  syscalls.asm
[i] out syscalls.nim
[i] Function filter file "functions.txt" contains 10 functions.
[i] Found return types for 10 functions.
[i] Producing randomised function mapping...
        GetTEBAsm64 -> SFvaGcZvCStqpimm
        NtQuerySystemInformation -> ubyRCpOytBpCkrgW
        NtOpenProcess -> sjGfpzWwEqIMryMW
        NtOpenProcessToken -> nZFSjOMSXlJYIfGF
        NtAdjustPrivilegesToken -> KDbJZsqcZWqlAZpm
        NtAllocateVirtualMemory -> xANRBkMmvNMFvMkf
        NtFreeVirtualMemory -> yZhhnBMbyifaYyWA
        NtReadVirtualMemory -> VHlCcYwobYwUwxqH
        NtWriteVirtualMemory -> VVkixCSJcidoBZgM
        NtClose -> CXmzjWrWwTeuSBjT
[+] Success! Outputted to syscalls.nim

For easy of integration, the mapping shown in the command-line is added a comment to the top of the outputted syscalls.nim file. As below (including the first function to demonstrate the output):

{.passC:"-masm=intel".}

# GetTEBAsm64 -> SFvaGcZvCStqpimm
# NtQuerySystemInformation -> ubyRCpOytBpCkrgW
# NtOpenProcess -> sjGfpzWwEqIMryMW
# NtOpenProcessToken -> nZFSjOMSXlJYIfGF
# NtAdjustPrivilegesToken -> KDbJZsqcZWqlAZpm
# NtAllocateVirtualMemory -> xANRBkMmvNMFvMkf
# NtFreeVirtualMemory -> yZhhnBMbyifaYyWA
# NtReadVirtualMemory -> VHlCcYwobYwUwxqH
# NtWriteVirtualMemory -> VVkixCSJcidoBZgM
# NtClose -> CXmzjWrWwTeuSBjT

proc SFvaGcZvCStqpimm*(): LPVOID {.asmNoStackFrame.} =
    asm """
	mov rax, qword ptr gs:[0x30]
	ret
    """

Notably your function definitions such the below will need to be updated with the randomised names too.

EXTERN_C NTSTATUS NtOpenProcess(
	OUT PHANDLE ProcessHandle,
	IN ACCESS_MASK DesiredAccess,
	IN POBJECT_ATTRIBUTES ObjectAttributes,
	IN PCLIENT_ID ClientId OPTIONAL);

Should become:

EXTERN_C NTSTATUS sjGfpzWwEqIMryMW(
	OUT PHANDLE ProcessHandle,
	IN ACCESS_MASK DesiredAccess,
	IN POBJECT_ATTRIBUTES ObjectAttributes,
	IN PCLIENT_ID ClientId OPTIONAL);

syscalls_rand.nim is included as an example output of this randomisation function.

Limitations

• 64-bit only.

Credits

• @Outflank and @_DaWouw for InlineWhispers
• @byt3bl33d3r for his incredibly informative OffensiveNim repository
• The assembly code used within this tool is based on the assembly output from the SysWhispers tool from @Jackson_T.
• All people credited for SysWhispers