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[原创][庆祝建党]2021GKCTF-WP(NAN)
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发表于: 2021-6-29 16:07
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使用exeinforpe检查发现是用的Enigma Virtual Box打的包
下载工具EnigmaVBUnpacker将exe解包一下
得到QQQQT_unpacked.exe
拖入IDA分析
查找字符串得到比较数据和base58的码表：56fkoP8KhwCf3v7CEz和123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz
写一个脚本解一下即可
得到apk，直接拖入jadx，得到关键逻辑
其实很简单，就是MainActivity里面调用的check函数检测我们输入的flag，而check函数是System.loadLibrary("native-lib");
使用工具apk-tools获取一下apk的资源，然后将lib文件夹里面的so拖入IDA进行分析
shift+f12查找字符串，发现会检测是否被调试
交叉引用一下发现检测调试的函数是sub_738378DF3C
然后关键的check函数是Java_com_example_myapplication_MainActivity_check
里面是将我们输入的字符串进行TEA加密, 里面有比较数据
使用IDA和adb调试一下，可以发现key，即那四个数字被改变
然后写个C脚本解一下即可
最后将这得到的flag{md5(input)}一下即可,flag{77bca47fe645ca1bd1ac93733171c9c4}
拖入IDA分析，main函数在先检测了input的格式，然后传入man_check函数检测，可以从maincheck函数中发现，GKCTF{之后的24个字节被传入了main_encrypto函数进行加密，再后面四字节是sha_256，再后面四字节是sha_512，再后面四字节是md5，main_encrypto函数内部是Des3，最后base64加密一下，后面那些hash函数直接查一下就可以得到，这个DES是关键，
最后将后面的hash拼接一下，得到flag为：GKCTF{87f645e9-b628-412f-9d7a-e402f20af940}
在scanf输入函数下断点之后，交叉引用输入的变量，发现下方有个函数引用了输入，
进去之后根据XXTEA的加密逻辑对拍一下，交叉引用一下，这里是生成delta的逻辑，调试到这里得到delta为0x33445566, 同时对拍也会得到key
然后下方跟着调试下去，可以在内存里得到比较数据
得到flag为：9b34a61df773acf0e4dec25ea5fb0e29
C# 逆向，DLL做核心验证，DLL 里面有反调试，简单 patch 即可
然后有一个极其恶心的 AES 魔改算法
行移位
外层的也很恶心
解密目标数据得到: Meaningless_!$!%*@^%#%_Code 字符串
C#层还有一个 code 计算
最后组合得到flag
flag{ginkgoCX@Meaningless!$!%*@^%#%_Code}
checkin
这有个栈溢出，可以覆盖rbp
Pass是个md5加密，在线解一下就行
然后就是略微麻烦的栈迁移加ROP了
登入后台，简单审计发现有一个任意文件读
先是注册，注册后有一个简单的任意文件下载
看到是纯Servlet写的，加大了我做这道题的信心（哈哈哈）
发现uploadServlet并没有验证是不是admin，可以直接上传
baseDao
这里直接xmldecode反序列化了
registerServlet
这里写的非常奇怪啊，反正注册的时候还会加载一次
上传../../db/db.xml
然后随便注册一个用户就可以弹了
套娃题，第一层跟巅峰极客tryRSA基本一致，第二层$modq1$稍微变换一下，消去p1之后和n2做一次gcd就好了，具体看代码实现
打开wireshark，跟踪http流，复制最长的那段base64的
打开ipython，用ctfbox解几次编码，最后将双写去掉就能拿到flag
# _*_ coding: utf-8 _*_# editor: SYJ# function: Reversed By SYJ# describe:def b58encode(tmp:str) -> str:
tmp = list(map(ord,tmp))
temp = tmp[0]
base58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
for i in range(len(tmp)-1):
temp = temp * 256 + tmp[i+1]
tmp = []
while True:
tmp.insert(0,temp % 58)
temp = temp // 58
if temp == 0:
break temp = ""
for i in tmp:
temp += base58[i]
return temp
def b58decode(tmp:str) -> str:
import binascii
base58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
temp = []
for i in tmp:
temp.append(base58.index(i))
tmp = temp[0]
for i in range(len(temp)-1):
tmp = tmp * 58 + temp[i+1]
return binascii.unhexlify(hex(tmp)[2:].encode("utf-8")).decode("UTF-8")
cmp = "56fkoP8KhwCf3v7CEz"
print('flag{' + b58decode(cmp) + '}')
# 得到flag为：flag{12t4tww3r5e77}# _*_ coding: utf-8 _*_# editor: SYJ# function: Reversed By SYJ# describe:def b58encode(tmp:str) -> str:
tmp = list(map(ord,tmp))
temp = tmp[0]
base58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
for i in range(len(tmp)-1):
temp = temp * 256 + tmp[i+1]
tmp = []
while True:
tmp.insert(0,temp % 58)
temp = temp // 58
if temp == 0:
break temp = ""
for i in tmp:
temp += base58[i]
return temp
def b58decode(tmp:str) -> str:
import binascii
base58 = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
temp = []
for i in tmp:
temp.append(base58.index(i))
tmp = temp[0]
for i in range(len(temp)-1):
tmp = tmp * 58 + temp[i+1]
return binascii.unhexlify(hex(tmp)[2:].encode("utf-8")).decode("UTF-8")
cmp = "56fkoP8KhwCf3v7CEz"
print('flag{' + b58decode(cmp) + '}')
# 得到flag为：flag{12t4tww3r5e77}#include <stdio.h>#include <stdint.h>void encrypt (uint32_t* v, uint32_t* k) {
uint32_t v0=v[0], v1=v[1], sum=0, i; /* set up */
uint32_t delta=0x458BCD42; /* a key schedule constant */
uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */
for (i=0; i < 32; i++) { /* basic cycle start */
sum += delta;
v0 += ((v1<<4) + k0) ^ (v1 + sum) ^ ((v1>>5) + k1);
v1 += ((v0<<4) + k2) ^ (v0 + sum) ^ ((v0>>5) + k3);
} /* end cycle */
v[0]=v0; v[1]=v1;
}void decrypt (uint32_t* v, uint32_t* k) {
uint32_t delta=0x458BCD42; /* a key schedule constant */
uint32_t v0=v[0], v1=v[1], sum=(delta*32)&0xffffffff, i; /* set up */
uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */
for (i=0; i<32; i++) { /* basic cycle start */
v1 -= ((v0<<4) + k2) ^ (v0 + sum) ^ ((v0>>5) + k3);
v0 -= ((v1<<4) + k0) ^ (v1 + sum) ^ ((v1>>5) + k1);
sum -= delta;
} /* end cycle */
v[0]=v0; v[1]=v1;
}int main()
{ uint32_t array[] = {0xF5A98FF3,0xA21873A3};//{0xF5A98FF3,0xA21873A3};
uint32_t key[4] = {9,7,8,6};
//encrypt(array, key);
decrypt(array, key);
//printf("%x\n%x",array[0],array[1]);
printf("%c,%c,%c,%c,%c,%c,%c,%c",*((char*)&array[0]+0),*((char*)&array[0]+1),*((char*)&array[0]+2),*((char*)&array[0]+3),*((char*)&array[1]+0),*((char*)&array[1]+1),*((char*)&array[1]+2),*((char*)&array[1]+3));
return 0;
//GKcTFg0
}#include <stdio.h>#include <stdint.h>void encrypt (uint32_t* v, uint32_t* k) {
uint32_t v0=v[0], v1=v[1], sum=0, i; /* set up */
uint32_t delta=0x458BCD42; /* a key schedule constant */
uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */
for (i=0; i < 32; i++) { /* basic cycle start */
sum += delta;
v0 += ((v1<<4) + k0) ^ (v1 + sum) ^ ((v1>>5) + k1);
v1 += ((v0<<4) + k2) ^ (v0 + sum) ^ ((v0>>5) + k3);
} /* end cycle */
v[0]=v0; v[1]=v1;
}void decrypt (uint32_t* v, uint32_t* k) {
uint32_t delta=0x458BCD42; /* a key schedule constant */
uint32_t v0=v[0], v1=v[1], sum=(delta*32)&0xffffffff, i; /* set up */
uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */
for (i=0; i<32; i++) { /* basic cycle start */
v1 -= ((v0<<4) + k2) ^ (v0 + sum) ^ ((v0>>5) + k3);
v0 -= ((v1<<4) + k0) ^ (v1 + sum) ^ ((v1>>5) + k1);
sum -= delta;
} /* end cycle */
v[0]=v0; v[1]=v1;
}int main()
{ uint32_t array[] = {0xF5A98FF3,0xA21873A3};//{0xF5A98FF3,0xA21873A3};
uint32_t key[4] = {9,7,8,6};
//encrypt(array, key);
decrypt(array, key);
//printf("%x\n%x",array[0],array[1]);
printf("%c,%c,%c,%c,%c,%c,%c,%c",*((char*)&array[0]+0),*((char*)&array[0]+1),*((char*)&array[0]+2),*((char*)&array[0]+3),*((char*)&array[1]+0),*((char*)&array[1]+1),*((char*)&array[1]+2),*((char*)&array[1]+3));
return 0;
//GKcTFg0
}from Crypto.Cipher import DES3
ans = [163, 246, 150, 62, 51, 77, 196, 195, 217, 14, 114, 101, 54, 157, 51, 43, 159, 141, 44, 240, 184, 78, 254, 164, 169, 210, 106, 142, 66, 244, 94, 64] # 比较数据base64解码之后
c = bytes(ans)
key = b'WelcomeToTheGKCTF2021XXX'
iv1 = b'1Ssecret'
iv2 = b'wumansgy'
# key = b'00000000'# iv = b'00000000'des = DES3.new(key,DES3.MODE_CBC,iv1)
m = des.decrypt(c)
print(m)
from Crypto.Cipher import DES3
ans = [163, 246, 150, 62, 51, 77, 196, 195, 217, 14, 114, 101, 54, 157, 51, 43, 159, 141, 44, 240, 184, 78, 254, 164, 169, 210, 106, 142, 66, 244, 94, 64] # 比较数据base64解码之后
c = bytes(ans)
key = b'WelcomeToTheGKCTF2021XXX'
iv1 = b'1Ssecret'
iv2 = b'wumansgy'
# key = b'00000000'# iv = b'00000000'des = DES3.new(key,DES3.MODE_CBC,iv1)
m = des.decrypt(c)
print(m)
#include <stdio.h>#include <stdlib.h>#define DELTA 0x33445566int main()
{ unsigned int v[8] = {0x993CAB5C, 0x3F40E129, 0x777791DE, 0x737DFEA6, 0x0ECCF59E6, 0x0C9604CE3, 0x9682C0A5, 0x556F2A1E};
unsigned int key[4] = {0x000036B0, 0x00013816, 0x00000010, 0x0001E0F3};
unsigned int sum = 0;
unsigned int y,z,p,rounds,e;
int n = 8;
int i = 0;
rounds = 12;
y = v[0];
sum = (rounds*DELTA)&0xffffffff;
do //0x9E3779B9*(52/35)-0x4AB325AA，测试来要循环7次
{
e = sum >> 2 & 3;
for(p=n-1;p>0;p--) //34次循环
{
z = v[p-1];
v[p] = (v[p] - ((((z>>5)^(y<<2))+((y>>3)^(z<<4))) ^ ((key[(p^e)&3]^z)+(y ^ sum)))) & 0xffffffff;
y = v[p];
}
z = v[n-1];
v[0] = (v[0] - (((key[(p^e)&3]^z)+(y ^ sum)) ^ (((y<<2)^(z>>5))+((z<<4)^(y>>3))))) & 0xffffffff;
y = v[0];
sum = (sum-DELTA)&0xffffffff;
}while(--rounds);
for(i=0;i<8;i++)
{
printf("%c%c%c%c",*((char*)&v[i]+0),*((char*)&v[i]+1),*((char*)&v[i]+2),*((char*)&v[i]+3));
}
return 0;
}#include <stdio.h>#include <stdlib.h>#define DELTA 0x33445566int main()
{ unsigned int v[8] = {0x993CAB5C, 0x3F40E129, 0x777791DE, 0x737DFEA6, 0x0ECCF59E6, 0x0C9604CE3, 0x9682C0A5, 0x556F2A1E};
unsigned int key[4] = {0x000036B0, 0x00013816, 0x00000010, 0x0001E0F3};
unsigned int sum = 0;
unsigned int y,z,p,rounds,e;
int n = 8;
int i = 0;
rounds = 12;
y = v[0];
sum = (rounds*DELTA)&0xffffffff;
do //0x9E3779B9*(52/35)-0x4AB325AA，测试来要循环7次
{
e = sum >> 2 & 3;
for(p=n-1;p>0;p--) //34次循环
{
z = v[p-1];
v[p] = (v[p] - ((((z>>5)^(y<<2))+((y>>3)^(z<<4))) ^ ((key[(p^e)&3]^z)+(y ^ sum)))) & 0xffffffff;
y = v[p];
}
z = v[n-1];
v[0] = (v[0] - (((key[(p^e)&3]^z)+(y ^ sum)) ^ (((y<<2)^(z>>5))+((z<<4)^(y>>3))))) & 0xffffffff;
y = v[0];
sum = (sum-DELTA)&0xffffffff;
}while(--rounds);
for(i=0;i<8;i++)
{
printf("%c%c%c%c",*((char*)&v[i]+0),*((char*)&v[i]+1),*((char*)&v[i]+2),*((char*)&v[i]+3));
}
return 0;
}void myshift(int pArray[4][4]){
int tmpArr[4][4] = {0};
tmpArr[0][0] = pArray[0][0];
tmpArr[0][1] = pArray[1][1];
tmpArr[0][2] = pArray[2][2];
tmpArr[0][3] = pArray[3][3];
tmpArr[1][0] = pArray[1][0];
tmpArr[1][1] = pArray[2][1];
tmpArr[1][2] = pArray[3][2];
tmpArr[1][3] = pArray[0][3];
tmpArr[2][0] = pArray[2][0];
tmpArr[2][1] = pArray[3][1];
tmpArr[2][2] = pArray[0][2];
tmpArr[2][3] = pArray[1][3];
tmpArr[3][0] = pArray[3][0];
tmpArr[3][1] = pArray[0][1];
tmpArr[3][2] = pArray[1][2];
tmpArr[3][3] = pArray[2][3];
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
pArray[i][j] = tmpArr[i][j];
}
}
}void myshift(int pArray[4][4]){
int tmpArr[4][4] = {0};
tmpArr[0][0] = pArray[0][0];
tmpArr[0][1] = pArray[1][1];
tmpArr[0][2] = pArray[2][2];
tmpArr[0][3] = pArray[3][3];
tmpArr[1][0] = pArray[1][0];
tmpArr[1][1] = pArray[2][1];
tmpArr[1][2] = pArray[3][2];
tmpArr[1][3] = pArray[0][3];
tmpArr[2][0] = pArray[2][0];
tmpArr[2][1] = pArray[3][1];
tmpArr[2][2] = pArray[0][2];
tmpArr[2][3] = pArray[1][3];
tmpArr[3][0] = pArray[3][0];
tmpArr[3][1] = pArray[0][1];
tmpArr[3][2] = pArray[1][2];
tmpArr[3][3] = pArray[2][3];
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
pArray[i][j] = tmpArr[i][j];
}
}
}void mydeaes(char *p, char * iv,int plen, char *key){
int pArray0[4][4];
int pArray1[4][4];
int pIv[4][4];
int k=0;
char key_use[16];
convertToIntArray(iv, pIv);
for(int k1 = 31; k1 >= 0; k1 -= 1) {
memcpy(key_use, key, 16);
getRoundIvAndKey(k1, iv, key_use, pIv); // f8 82
extendKey(key_use);//扩展密钥
convertToIntArray(&p[16], pArray1);
convertToIntArray(&p[0], pArray0);
addRoundKey(pArray1, 10);
for(int i = 9; i >= 1; i--) {
mydeshift(pArray1);
deSubBytes(pArray1);
addRoundKey(pArray1, i);
myTranspose(pArray1);
deMixColumns(pArray1);//列混合
myTranspose(pArray1);
}
mydeshift(pArray1);//行移位
deSubBytes(pArray1);//字节代换
addRoundKey(pArray1, 0);//一开始的轮密钥加
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
pArray1[i][j] ^= pArray0[i][j];
}
}
addRoundKey(pArray0, 10);
for(int i = 9; i >= 1; i--) {
mydeshift(pArray0);
deSubBytes(pArray0);
addRoundKey(pArray0, i);
myTranspose(pArray0);
deMixColumns(pArray0);//列混合
myTranspose(pArray0);
}
mydeshift(pArray0);//行移位
deSubBytes(pArray0);//字节代换
addRoundKey(pArray0, 0);//一开始的轮密钥加
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
pArray0[i][j] ^= pIv[i][j];
}
}
convertArrayToStr(pArray0, &p[0]);
convertArrayToStr(pArray1, &p[16]);
}
}void mydeaes(char *p, char * iv,int plen, char *key){
int pArray0[4][4];
int pArray1[4][4];
int pIv[4][4];
int k=0;
char key_use[16];
convertToIntArray(iv, pIv);
for(int k1 = 31; k1 >= 0; k1 -= 1) {
memcpy(key_use, key, 16);
getRoundIvAndKey(k1, iv, key_use, pIv); // f8 82
extendKey(key_use);//扩展密钥
convertToIntArray(&p[16], pArray1);
convertToIntArray(&p[0], pArray0);
addRoundKey(pArray1, 10);
for(int i = 9; i >= 1; i--) {
mydeshift(pArray1);
deSubBytes(pArray1);
addRoundKey(pArray1, i);
myTranspose(pArray1);
deMixColumns(pArray1);//列混合
myTranspose(pArray1);
}
mydeshift(pArray1);//行移位
deSubBytes(pArray1);//字节代换
addRoundKey(pArray1, 0);//一开始的轮密钥加
for (int i = 0; i < 4; ++i) {
for (int j = 0; j < 4; ++j) {
pArray1[i][j] ^= pArray0[i][j];
}
}
[招生]科锐逆向工程师培训(2024年11月15日实地，远程教学同时开班, 第51期)
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