碎碎念
这次比赛让我知道了AES密钥长度除了可以等于16还可以等于32...不要看到AES256的时候脑子里只有AES没有256==
DaShen Decode AES
白给题，sqlite直接查询出来iv和key然后AES解密即可
#!/usr/bin/env python
from Crypto.Util.number import *
from Crypto.Cipher import AES
import sqlite3
fileName = "db.db"
conn = sqlite3.connect(fileName)
c =conn.cursor()
ret = c.execute("SELECT * FROM config1 WHERE a=1")
for i in ret:
print(i)
enc = "db6427960a6622ffac27ef5437acf1459a592d1a96b73e75490c8badb0ed294c1e9232213e63461dd2d9f6d327e51641"
iv = b"a5efdbd57b84ca88"
key = b"37eaae0141f1a3adf8a1dee655853766"
key = long_to_bytes(int(key,16))
cipher = AES.new(key,AES.MODE_CBC,iv)
enc = long_to_bytes(int(enc,16))
dec = cipher.decrypt(enc)
print(dec)
# ByteCTF{fl-ag-IS-to-ng-xu-el-ih-ai}
QIAO
main函数的ollvm去掉以后可以看到大致逻辑
_int64 __fastcall main(int a1, char **a2, char **a3, __m128i a4)
{
void *v5; // [rsp+60h] [rbp-30h]
unsigned int v6; // [rsp+78h] [rbp-18h]
if ( a1 == 2 && strlen(a2[1]) == 32 && (v5 = sub_401180(a2[1]), (unsigned int)sub_4018C0((__int64)v5, a4)) )
{
printf("[*]ByteCTF{%s}.\n", a2[1]);
v6 = 0;
}
else
{
v6 = -1;
printf("[*]ByteCTF{d2h5IG5vdCBnbyBob21l}.\n");
}
return v6;
}
sub_401180将输入转16进制数，sub_4018C0调用了sub_401E90是个很大的vm，调试了一会儿发现没啥用，最后面动态调用了一个函数((void (__fastcall *)(_QWORD, _QWORD))v149)(*inputStr, *v136);,在这个地方下断点然后对输入下读写断点以后，断了几次发现了下面这个：
image
尝试输入了一下发现真的就是flag...
CrackMe
sha256算法经过了更改，在输入长度超过32个字节的时候只有前四个字节参与了运算，直接爆破前四个字节
sha256我在github上找了一个很相似的项目改了一下：https://github.com/monkeyDemon/Blockchain-programming-exercises/blob/master/1.Blockchain%20basic%20exercises/2.Cryptography%20and%20security%20technology/SHA256/C%20Code/sha256.c
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <stdlib.h>
#include <memory.h>
#include <string.h>
#include "sha256.h"
#define BLOCKSIZE 16
typedef struct{
uint32_t eK[44],dK[44];
int rounds;
} AESKEY;
#define ROF32(x,n) ((x << n) | (x >> (32-n)))
#define ROR32(x,n) ((x >> n) | (x << (32-n)))
#define BYTE(x,n) (((x)>>((n)*8)) & 0xff)
#define MIX(x) (((S[BYTE((x),2)] << 24) & 0xff000000) ^ \
((S[BYTE((x),1)] << 16) & 0xff0000) ^ \
((S[BYTE((x),0)] << 8) & 0xff00) ^ \
((S[BYTE((x),3)]) & 0xff))
#define LOAD32(x,y) do{ (x) = \
((uint32_t)((y)[0]&0xff)<<24) |\
((uint32_t)((y)[1]&0xff)<<16) |\
((uint32_t)((y)[2]&0xff)<<8 ) |\
((uint32_t)((y)[3]&0xff));\
}while(0)
#define STORE32(x,y) do{ \
(y)[0] = (uint8_t)(((x)>>24) & 0xff) ; \
(y)[1] = (uint8_t)(((x)>>16) & 0xff) ; \
(y)[2] = (uint8_t)(((x)>>8) & 0xff) ; \
(y)[3] = (uint8_t)((x) & 0xff) ; \
}while(0)
unsigned char S[256] = {
0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5, 0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0, 0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC, 0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A, 0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0, 0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B, 0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85, 0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5, 0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17, 0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88, 0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C, 0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9, 0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6, 0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E, 0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94, 0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68, 0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16};
unsigned char inv_S[256] = {
0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38, 0xBF, 0x40, 0xA3, 0x9E, 0x81, 0xF3, 0xD7, 0xFB,
0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87, 0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB,
0x54, 0x7B, 0x94, 0x32, 0xA6, 0xC2, 0x23, 0x3D, 0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,
0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2, 0x76, 0x5B, 0xA2, 0x49, 0x6D, 0x8B, 0xD1, 0x25,
0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92,
0x6C, 0x70, 0x48, 0x50, 0xFD, 0xED, 0xB9, 0xDA, 0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,
0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A, 0xF7, 0xE4, 0x58, 0x05, 0xB8, 0xB3, 0x45, 0x06,
0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02, 0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B,
0x3A, 0x91, 0x11, 0x41, 0x4F, 0x67, 0xDC, 0xEA, 0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,
0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85, 0xE2, 0xF9, 0x37, 0xE8, 0x1C, 0x75, 0xDF, 0x6E,
0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89, 0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B,
0xFC, 0x56, 0x3E, 0x4B, 0xC6, 0xD2, 0x79, 0x20, 0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,
0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31, 0xB1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xEC, 0x5F,
0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D, 0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF,
0xA0, 0xE0, 0x3B, 0x4D, 0xAE, 0x2A, 0xF5, 0xB0, 0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,
0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26, 0xE1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D};
uint8_t M[4][4] = {
{0x02, 0x03, 0x01, 0x01},
{0x01, 0x02, 0x03, 0x01},
{0x01, 0x01, 0x02, 0x03},
{0x03, 0x01, 0x01, 0x02}
};
uint8_t inv_M[4][4] = {
{0x0E, 0x0B, 0x0D, 0x09},
{0x09, 0x0E, 0x0B, 0x0D},
{0x0D, 0x09, 0x0E, 0x0B},
{0x0B, 0x0D, 0x09, 0x0E}
};
static const uint32_t rcon[10] = {
0x01000000UL, 0x02000000UL, 0x04000000UL, 0x08000000UL, 0x10000000UL,
0x20000000UL, 0x40000000UL, 0x80000000UL, 0x1B000000UL, 0x36000000UL
};
int KeyExpansion(uint8_t * key,AESKEY * aeskey){
uint32_t * w = aeskey ->eK;
uint32_t * v = aeskey ->dK;
for(int i=0 ; i<4 ; i++ ){
LOAD32(w[i], key+i*4);
}
for(int i=0;i<10;i++){
w[4]=w[0]^MIX(w[3])^rcon[i];
w[5]=w[1]^w[4];
w[6]=w[2]^w[5];
w[7]=w[3]^w[6];
w+=4;
}
w = (aeskey -> eK) + 40;
for(int j=0 ;j<11;j++){
for(int i = 0 ; i<4;i++){
v[i]=w[i];
}
v+=4;
w-=4;
}
return 0;
}
void loadStateArray(uint8_t (*state)[4],uint8_t *in){
for(int i=0;i<4;i++){
for(int j=0;j<4;j++){
state[j][i]=*in++;
}
}
}
void storeStateArray(uint8_t (*state)[4],uint8_t *out){
for(int i=0;i<4;i++){
for(int j=0;j<4;j++){
*out++=state[j][i];
}
}
}
void shiftRows(uint8_t (*state)[4]){
uint32_t temp[4]={0};
for(int i=0;i<4;i++){
LOAD32(temp[i], state[i]);
temp[i]=ROF32(temp[i], i*8);
STORE32(temp[i], state[i]);
}
}
void invShiftRows(uint8_t (*state)[4]) {
uint32_t temp[4] = {0};
for (int i = 0; i < 4; i++) {
LOAD32(temp[i], state[i]);
temp[i] = ROR32(temp[i], i*8);
STORE32(temp[i], state[i]);
}
}
uint8_t GMul(uint8_t u, uint8_t v) {
uint8_t p = 0;
for (int i = 0; i < 8; ++i) {
if (u & 0x01) { //
p ^= v;
}
int flag = (v & 0x80);
v <<= 1;
if (flag) {
v ^= 0x1B;
}
u >>= 1;
}
return p;
}
void mixColumns(uint8_t (*state)[4]){
uint8_t tmp[4][4];
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j){
tmp[i][j] = state[i][j];
}
}
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
state[i][j] = GMul(M[i][0], tmp[0][j]) ^
GMul(M[i][1], tmp[1][j]) ^
GMul(M[i][2], tmp[2][j]) ^
GMul(M[i][3], tmp[3][j]) ;
}
}
}
void invMixColumns(uint8_t (*state)[4]){
uint8_t tmp[4][4];
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j){
tmp[i][j] = state[i][j];
}
}
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
state[i][j] = GMul(inv_M[i][0], tmp[0][j]) ^
GMul(inv_M[i][1], tmp[1][j]) ^
GMul(inv_M[i][2], tmp[2][j]) ^
GMul(inv_M[i][3], tmp[3][j]) ;
}
}
}
int addRoundKey(uint8_t (*state)[4], const uint32_t *key) {
uint8_t k[4][4];
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
k[j][i] = (uint8_t) BYTE(key[i], 3 - j); //按列异或秘钥
state[j][i] ^= k[j][i];
}
}
return 0;
}
int subBytes(uint8_t (*state)[4]) {
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
state[i][j] = S[state[i][j]];
}
}
return 0;
}
int invSubBytes(uint8_t (*state)[4]) {
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
state[i][j] = inv_S[state[i][j]];
}
}
return 0;
}
void aesEncryptBlock(uint8_t * mblock,uint8_t * cblock,uint8_t * key){
AESKEY aeskey;
uint8_t state[4][4]={0};
KeyExpansion(key, &aeskey);
loadStateArray(state, mblock);
uint32_t * ekPointer = aeskey.eK;
addRoundKey(state, ekPointer);
for(int i=1;i<10;i++){
ekPointer += 4;
subBytes(state);
shiftRows(state);
mixColumns(state);
addRoundKey(state, ekPointer);
}
ekPointer += 4;
subBytes(state);
shiftRows(state);
addRoundKey(state, ekPointer);
storeStateArray(state, cblock);
}
void aesDecryptBlock(uint8_t * mblock,uint8_t * cblock,uint8_t * key){
AESKEY aeskey;
uint8_t state[4][4]={0};
KeyExpansion(key, &aeskey);
loadStateArray(state, cblock);
uint32_t * dkPointer = aeskey.dK;
addRoundKey(state, dkPointer);
for(int i=1;i<10;i++){
dkPointer += 4;
invShiftRows(state);
invSubBytes(state);
addRoundKey(state, dkPointer);
invMixColumns(state);
}
dkPointer += 4;
invSubBytes(state);
invShiftRows(state);
addRoundKey(state, dkPointer);
storeStateArray(state, mblock);
}
int splitBlock(char * message,uint8_t ** blocks){
int len = (int)strlen(message);
int block_num = 2;
*blocks = (uint8_t *)malloc(block_num*16);
memcpy(*blocks, message, len);
//memset(*blocks+len,0,16-mod);
return block_num;
}
uint8_t * aesEncryptCBC(uint8_t * blocks,uint8_t * key,int block_num,uint8_t * iv){
uint8_t * tmp = iv;
for(int i = 0;i<block_num;i++){
for(int j = 0;j<16;j++){
blocks[16*i+j] ^= tmp[j];
}
aesEncryptBlock(blocks+16*i, blocks+16*i, key);
tmp = blocks+16*i;
}
return blocks;
}
void aesDecryptCBC(uint8_t * blocks,uint8_t * key,int block_num,uint8_t * iv){
uint8_t * tmp = blocks+(16*(block_num-2));
for(int i = block_num-1;i > -1;i--){
aesDecryptBlock(blocks+16*i, blocks+16*i, key);
for(int j = 0;j<16;j++){
blocks[16*i+j] ^= tmp[j];
}
if(i==1){
tmp = iv;
}else{
tmp -= 16;
}
}
}
void print(BYTE *s, int n)
{
for(int i = 0; i < n; i++)
printf("0x%x, ", s[i]);
printf("\n");
}
int main()
{
char message[]="\x2d\x18\x6a\x3e\x17\x2a\x14\x67\x37\x89\xf4\x99\xcd\x6c\xfb\xcd\x29\xb6\xc7\x3f\x4b\x4a\x27\xc2\x34\x64\x77\x68\x25\xaf\x90\xb2";
for(char a = 0x20; a < 0x7f; a++){
for(char b = 0x20; b < 0x7f; b++){
for(char c = 0x20; c < 0x7f; c++){
for(char d = 0x20; d < 0x7f; d++){
BYTE text1[5] = {a,b,c,d};
BYTE buf[SHA256_BLOCK_SIZE];
SHA256_CTX ctx;
sha256_init(&ctx);
sha256_update(&ctx, text1, strlen(text1));
sha256_final(&ctx, buf);
char key[16];
char iv[16];
for(int i = 0; i < 16; i++)
key[i] = buf[i];
for(int i = 16; i < 32; i++)
iv[i-16] = buf[i];
uint8_t * blocks = NULL;
int block_num = splitBlock(message,&blocks);
aesDecryptCBC(blocks,key,block_num,iv);
if(strstr(blocks, "ByteCTF") != NULL){
printf("flag: %s\n", blocks);
print(text1, 4);
return 0;
}
}
}
}
printf("%c\n", a);
}
return(0);
}
求出来输入good(填充到32+)可以获取flag
App1c
解压出来的二进制文件中有一个check函数，显示需要读取sandbox/secret文件，读取出来的字符串做md5后Aes256ECB解密MnRC6I9E0BbJ7LxLfrKhP6Xv5+c41AORjmG66eQxQks=即可获取flag。在run函数中可以看到调用了lua脚本，解压出来存在一个叫AppIcon.lua的脚本，可以直接编辑模式打开看到上面一段可读的脚本内容：
input = tostring(arg[1])
sanboxPath = tostring(arg[2]).."/secret"
debase64 = from_base64(input)
secret = "0"
if debase64 ~= nil then
secret = string.app1c(debase64)
end
file = io.open(sanboxPath, "w")
io.output(file)
io.write(tostring(secret))
io.close(file)
本来我没注意到string.app1c这个函数的时候我觉得下面不可读的内容也是有用的，但是没办法反编译，我用这个反汇编了一下发现其实就是base64的包，我码一下用到的几个lua相关的链接
基本知识与010Editor解析脚本：https://github.com/feicong/lua_re
luadec: https://github.com/viruscamp/luadec
还有个工具是unlua
调用时arg[1]是用户输入的字符串，arg[2]是sandbox的路径。将输入解base64后经过string.app1c的处理写入sandbox/secret文件。这个string.app1c猜测是对lua的string包做了扩展，然后找到了下面这个例子：
#include <stdio.h>
#include <stdlib.h>
#include "lua.h"
#include "lualib.h"
#include "lauxlib.h"
#import <objc/runtime.h>
#import <Foundation/Foundation.h>
#import <UIKit/UIDevice.h>
/* 库 open 函数的前置声明 */
int luaopen_mt(lua_State *L);
/* Function mt_get_device_name
* @return string device name
*/
static int mt_get_device_name(lua_State *L)
{
NSString *name = [[UIDevice currentDevice] name];
const char * name_str = [name UTF8String];
lua_pushstring(L, name_str);
return 1;
}
//注册函数库
static const luaL_Reg mt_lib[] = {
{"device_name", mt_get_device_name}, //获取设备名称
{NULL, NULL}
};
int luaopen_mt(lua_State *L)//注意, mt为扩展库的文件名
{
luaL_newlib(L, mt_lib);//暴露给lua脚本的接口
return 1;
}
// PWNlua层里的调用方法为:
local mt = require "mt"
print(mt.device_name())
所以需要找一下app1c这个字符串指向的函数：
__const:000246FC DCD aReverse ; "reverse"
__const:00024700 DCD sub_19146+1
__const:00024704 DCD aSub_1 ; "sub"
__const:00024708 DCD sub_191BA+1
__const:0002470C DCD aUpper ; "upper"
__const:00024710 DCD sub_1923E+1
__const:00024714 DCD aApp1c_0 ; "app1c"
__const:00024718 DCD sub_192B4+1
sub_192B4这个函数要求输入字符串长度是4，且可转10进制数。所以直接爆破4位的十进制数。注意是AES256...不是128
if __name__ == "__main__":
from Crypto.Cipher import AES
s = "MnRC6I9E0BbJ7LxLfrKhP6Xv5+c41AORjmG66eQxQks="
import base64, hashlib
enc = base64.decodestring(s)
for a in range(ord('0'), ord('9')+1, 1):
for b in range(ord('0'), ord('9')+1, 1):
for c in range(ord('0'), ord('9')+1, 1):
for d in range(ord('0'), ord('9')+1, 1):
ss = chr(a)+chr(b)+chr(c)+chr(d)
key = hashlib.md5(ss).hexdigest() # 就是这里，我还decode了一下所以一直不对，气死我了
ci = AES.new(key,AES.MODE_ECB)
strs = ci.decrypt(enc)
if strs.find("ByteCTF") >= 0:
print strs
print chr(a)+chr(b)+chr(c)+chr(d)
exit(0)
