[RealWorld] AES_BABY - Cew

xp0int Posted on Apr 29 2021

首先穷举通过pow，然后上传elf至服务器运行，elf成功爆破并输出后四位密钥服务器就打印flag
```
// elf
// aarch64-linux-gnu-gcc exp.c -I /openssl_path/openssl-aarch64/install/include/  -L /openssl_path/openssl-aarch64/install/lib -lssl -lcrypto -o exparm
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "openssl/aes.h"

#define BLOCK_SIZE 16

void print_data(const char *tittle, const void* data, int len);

int main( )
{
	unsigned char dic[62] = {97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57};
	unsigned char aes_key[16] = {0};
	unsigned char cmp[32] = {0};
	unsigned char cmp_unhex[16] = {0};
	unsigned char input[44] = {0};
	scanf("%s", &input);
	for(int i=0;i<12;i++){
		aes_key[i] = input[i];
	}
	for(int i=0;i<32;i++){
		cmp[i] = input[12+i];
	}
	for(int i=0;i<16;i++){
		unsigned char a = cmp[2*i] >= 'a' ? cmp[2*i] - 'a' + 10: cmp[2*i] - '0';
		unsigned char b = cmp[2*i+1] >= 'a' ? cmp[2*i+1] - 'a' + 10: cmp[2*i+1] - '0';
		cmp_unhex[i] = a << 4 | b;
	}

unsigned char aes_input[] = {75, 85, 78, 80, 69, 78, 71, 95, 72, 80, 67, 95, 65, 69, 83, 33};
	unsigned char enc_out[BLOCK_SIZE];

AES_KEY enc_key;
	//print_data("key", aes_key, 16);
	//print_data("enc", cmp_unhex, 16);
	for(int i=0;i<62;i++){
		for(int j=0;j<62;j++){
			for(int n=0;n<62;n++){
				for(int m=0;m<62;m++){
					aes_key[12] = dic[i];
					aes_key[13] = dic[j];
					aes_key[14] = dic[n];
					aes_key[15] = dic[m];
					
					AES_set_encrypt_key(aes_key, sizeof(aes_key)*8, &enc_key);
					AES_ecb_encrypt(aes_input, enc_out, &enc_key, AES_ENCRYPT);

if(!memcmp(enc_out, cmp_unhex, 16)){
						//printf("find!\n");
						printf("%c%c%c%c", dic[i], dic[j], dic[n], dic[m]);
					}
				}
			}
		}
	}

return 0;
}

void print_data(const char *tittle, const void* data, int len)
{
	printf("%s : ",tittle);
	const unsigned char * p = (const unsigned char*)data;
	int i = 0;
	
	for (; i<len; ++i)
		printf("%02X ", *p++);
	
	printf("\n");
}
```
```
# exp.py
from pwn import *
from hashlib import md5
import string

context.log_level='debug'

conn = remote("139.159.190.149", 10000)
conn.recvuntil("md5(")
content = conn.recvuntil("))", drop=True)
known = content.split(b'+')[0]
log.info("known: {}".format(known))

dic = string.ascii_letters+string.digits
crack = None
for a in dic:
    for b in dic:
        for c in dic:
            for d in dic:
                t = (a+b+c+d).encode()
                res = md5(known+t).hexdigest()
                if res[:6] == '000000':
                    crack = t
                    break
            if crack:
                break
        if crack:
            break
    if crack:
        break

log.info("crack: {}".format(crack))    
conn.sendline(crack)

from base64 import b64encode
elf = b64encode(open("exparm", "rb").read())
conn.sendlineafter("base64: ", elf)
conn.interactive()
```
flag{F4st_AES_Ad9A4cB2E4}

打赏还是打残，这是个问题