getprocaddress.c

#include <windows.h>

typedef unsigned char byte;
typedef unsigned short uint16;
typedef unsigned int uint32;

void* get_proc_addr(byte *base, byte *name)
{
	byte *pe_header = base+*(uint32*)(base+0x3c);
	byte *exports = base+*(uint32*)(pe_header+0x78);
	uint32 entries = *(uint32*)(exports+0x18);
	uint32 *addr = (uint32*)(base+*(uint32*)(exports+0x1c));
	uint32 *names = (uint32*)(base+*(uint32*)(exports+0x20));
	uint16 *ordinals = (uint16*)(base+*(uint32*)(exports+0x24));
	uint32 i;
	for (i=0; i<entries; i++) {
		byte *s = base+names[i];
		if (!strcmp(name, s)) break;
	}
	if (i == entries) return 0;
	return base+addr[ordinals[i]];
}

int main(void) {
	HANDLE hUser32 = LoadLibrary("user32.dll");
	void* proc = get_proc_addr(hUser32, "MessageBoxA");
	int r;
	char *msg = "綺麗なお姉さんは好きですか？", *title = "質問";
	_asm {
		push 4
		push title
		push msg
		push 0
		call proc
		mov r, eax
	}
	puts(r == 6 ? "はい！" : "いいえ！");
	return 0;
}