The Metasploit C compiler has built-in support for Base64 encoding and decoding, which is implemented as base64.h
.
#include <Windows.h>
#include <String.h>
#include <base64.h>
// "Hello World" encoded by Rex::Text.encode_base64()
#define BASE64STR "aGVsbG8gd29ybGQ="
int main() {
int base64StrLen = strlen(BASE64STR);
LPVOID lpBuf = VirtualAlloc(NULL, sizeof(int) * base64StrLen, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
memset(lpBuf, '\0', base64StrLen);
base64decode(lpBuf, BASE64STR, base64StrLen);
MessageBox(NULL, (char*) lpBuf, "Base64 Test", MB_OK);
return 0;
}
To compile, use [[How to use Metasploit::Framework::Compiler::Windows to compile C code|How to use Metasploit Framework Compiler Windows to compile C code]]