1. Classic Shellcode Injection

#shellcodeinjection #golang #maldev #malwaredevelopment

This technique is very similar to the Shellcode Runner technique. The only difference is that the shellcode will be injected in a remote process rather than the current process.

The Windows APIs required to perfrom this technique are the following:

Get a handle on a remote Process

To get a handle on a remote process the OpenProcess winapi will be used.

HANDLE OpenProcess(
  [in] DWORD dwDesiredAccess,
  [in] BOOL  bInheritHandle,
  [in] DWORD dwProcessId
);

  • dwDesiredAccess: This is defined by the rest of the APIs that we will use.

    • VirtualAllocEX -> PROCESS_VM_OPERATION

    • WriteProcessMemory -> PROCESS_VM_WRITE and PROCESS_VM_OPERATION

    • CreateRemoteThread -> PROCESS_CREATE_THREAD, PROCESS_QUERY_INFORMATION, PROCESS_VM_OPERATION, PROCESS_VM_WRITE, and PROCESS_VM_READ

    • Alternatively we can use PROCESS_ALL_ACCESS for convenience

    • More information on process security and access rights

  • bInheritHandle: Will be set to false

  • dwProcessId: Will be the ID of the process to get a handle on

Luckily the OpenProcess API is part of the windows package

Allocating memory on remote process

VirtuallAllocEx will be used for allocating memory for our shellcode in the remote memory.

  • hProcess: Process Handle returned by the OpenProcess API

  • lpAddress: We will let the API decide where to allocate the memory, therefore this value will be set to 0

  • dwSize: Will be the size of our shellcode

  • flAllocationType: We need to reserve and commit memory

  • flProtect: This can be done in a number of ways. To write and execute shellcode we will need rwx permissions. It is however unusual for legitimate programs to allocate memory with rwx permissions and it is usually flagged my AV engines. Another option is to assign rx or rw and then change permissions as needed for writing and executing with VirtualProtectEx.

NOTE: WriteProcessMemory that is used later on will temporarily assign WRITE permissions if they are missing from the memory page using VirtualAllocEx. It might be a good idea to manually manage permissions to avoid additional calls to VirtualAllocEx.

Writing shellcode to remote process

WriteProcessMemory winapi will be used to write shellcode to the remote memory

  • hProcess: Process Handle returned by the OpenProcess API

  • lpBaseAddress: Value returned from VirtualAllocEx

  • lpBuffer: A pointer to the beginning of our shellcode byte array

  • nSize: Size of our shellcode

  • lpNumberOfBytesWritten: Ouputs the number of bytes written to the destination address

Change Memory Permissions

Since the memory permissions were set to PAGE_READWRITE we now need to set them to PAGE_EXECUTE_READ. This can be achieved with VirtualProtectEx.

  • hProcess: Process Handle returned by the OpenProcess API

  • lpAddress: is the target address return from VirtualAlloc

  • dwSize: is the size of our shellcode

  • flNewProtect: is the new permissions we would like to assign PAGE_EXECUTE_READ

  • lpflOldProtect: will store the old permissions in case we want to restore them later on.

Create Remote Thread

CreateRemoteThread API will be used to create a thread and run the shellcode.

Only three parameters will be used and the rest will be set to null

  • hProcess: Process Handle returned by the OpenProcess API

  • lpStartAddress: The address returned by the VirtualAllocEX API

  • lpThreadId: Returns the newly created threadID

Execute Code:

Calculator successfully popped up.

Complete Code

Last updated

Was this helpful?