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[原创]KCTF2020秋季赛 第四题 突破重围 WP
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2020-11-24 09:29
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[使用反射调用com.kanxue.crackme.Crack :: boolean check(String)完成验证操作]
验证逻辑:
seri(序列化)长度应该为0x10.
seri = Crack::crypt("kaokaonio" ,seri)
seri = MyCrack::crackjni(seri)
seri = Crack::crypt("keepGoing" ,seri)
seri = base64(seri)
如果seri ==MyCrack:: crypt, 提示成功, 否则失败. //在crackjni里面会对MyCrack::crypt字段进行赋值为: "l+x7fKd2FBaaEY4NV4309A=="
流程还是很清晰的, 核心算法是一个native调用, MyCrack::crackjni(seri):
(IDA的分析数据没有保存, 就直接上逆向后的C++代码了)
#include <iomanip>
#include <iostream>
#include <cassert>
#define BLOCK_SIZE 0x10
using namespace std;
//java算法
void crypt(const char* key, unsigned char* buf, unsigned len)
{
unsigned char key_[256] = { 0 };
for (size_t i = 0; i < sizeof key_; i++)
{
key_[i] = i & 0xff;
}
int m = 0, n = 0;
for (size_t i = 0; i < sizeof key_; i++)
{
n = (key[m] & 0xFF) + (key_[i] & 0xFF) + n & 0xFF;
swap(key_[n], key_[i]);
m += 1;
m %= strlen(key);
}
int i = 0, j = 0;
m = 0, n = 0;
for (size_t c = 0; c < len; c++)
{
n = n + 1 & 0xFF;
m = (key_[n] & 0xFF) + m & 0xFF;
swap(key_[n], key_[m]);
i = key_[n];
j = key_[m];
auto idx = ((i & 0xFF) + (j & 0xFF) & 0xFF);
buf[c] = (buf[c] ^ key_[idx]);
}
}
void java_crypt(const char* key, unsigned char buf[BLOCK_SIZE])
{
crypt(key, buf, BLOCK_SIZE);
}
//native算法
void xor_block(int idx, unsigned char buf[BLOCK_SIZE])
{
const unsigned char key[192] =
{
0x6B, 0x61, 0x6F, 0x6B, 0x61, 0x6F, 0x6E, 0x69, 0x6B, 0x61, 0x6F, 0x6B, 0x61, 0x6F, 0x6E, 0x69,
0xC2, 0xFE, 0x96, 0x84, 0xA3, 0x91, 0xF8, 0xED, 0xC8, 0xF0, 0x97, 0x86, 0xA9, 0x9F, 0xF9, 0xEF,
0x1B, 0x67, 0x49, 0x57, 0xB8, 0xF6, 0xB1, 0xBA, 0x70, 0x06, 0x26, 0x3C, 0xD9, 0x99, 0xDF, 0xD3,
0xF1, 0xF9, 0x2F, 0x62, 0x49, 0x0F, 0x9E, 0xD8, 0x39, 0x09, 0xB8, 0xE4, 0xE0, 0x90, 0x67, 0x37,
0x99, 0x7C, 0xB5, 0x83, 0xD0, 0x73, 0x2B, 0x5B, 0xE9, 0x7A, 0x93, 0xBF, 0x09, 0xEA, 0xF4, 0x88,
0x0E, 0xC3, 0x71, 0x82, 0xDE, 0xB0, 0x5A, 0xD9, 0x37, 0xCA, 0xC9, 0x66, 0x3E, 0x20, 0x3D, 0xEE,
0x99, 0xE4, 0x59, 0x30, 0x47, 0x54, 0x03, 0xE9, 0x70, 0x9E, 0xCA, 0x8F, 0x4E, 0xBE, 0xF7, 0x61,
0x77, 0x8C, 0xB6, 0x1F, 0x30, 0xD8, 0xB5, 0xF6, 0x40, 0x46, 0x7F, 0x79, 0x0E, 0xF8, 0x88, 0x18,
0xB6, 0x48, 0x1B, 0xB4, 0x86, 0x90, 0xAE, 0x42, 0xC6, 0xD6, 0xD1, 0x3B, 0xC8, 0x2E, 0x59, 0x23,
0x9C, 0x83, 0x3D, 0x5C, 0x1A, 0x13, 0x93, 0x1E, 0xDC, 0xC5, 0x42, 0x25, 0x14, 0xEB, 0x1B, 0x06,
0x43, 0x2C, 0x52, 0xA6, 0x59, 0x3F, 0xC1, 0xB8, 0x85, 0xFA, 0x83, 0x9D, 0x91, 0x11, 0x98, 0x9B,
0xB0, 0x0C, 0x55, 0xF3, 0xC7, 0x17, 0x8A, 0xD7, 0xCC, 0x63, 0x8D, 0xD7, 0xD0, 0x79, 0x01, 0xE7,
};
for (size_t i = 0; i < BLOCK_SIZE; i++)
{
buf[i] ^= key[idx * BLOCK_SIZE + i];
}
}
void transform(unsigned char buf[BLOCK_SIZE])
{
const unsigned char s_box[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,
};
for (size_t i = 0; i < BLOCK_SIZE; i++)
{
buf[i] = s_box[buf[i]];
}
}
void untransform(unsigned char buf[BLOCK_SIZE])
{
const unsigned char s_box[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,
};
for (size_t i = 0; i < BLOCK_SIZE; i++)
{
bool found = false;
for (size_t j = 0; j < 256; j++)
{
if (s_box[j] == buf[i])
{
buf[i] = (unsigned char)j;
found = true;
break;
}
}
assert(found);
}
}
void xchange_byte(unsigned char buf[BLOCK_SIZE])
{
auto c = buf[1];
buf[1] = buf[5];
buf[5] = buf[9];
buf[9] = buf[0xd];
buf[0xd] = c;
swap(buf[2], buf[0xa]);
swap(buf[6], buf[0xe]);
c = buf[3];
buf[3] = buf[0xf];
buf[0xf] = buf[0xb];
buf[0xb] = buf[7];
buf[7] = c;
}
void unxchange_byte(unsigned char buf[BLOCK_SIZE])
{
auto c = buf[1];
buf[1] = buf[0xd];
buf[0xd] = buf[9];
buf[9] = buf[5];
buf[5] = c;
swap(buf[2], buf[0xa]);
swap(buf[6], buf[0xe]);
c = buf[3];
buf[3] = buf[7];
buf[7] = buf[0xb];
buf[0xb] = buf[0xf];
buf[0xf] = c;
}
void xor_scroll(unsigned char buf[BLOCK_SIZE])
{
for (size_t i = 0; i < 4; i++)
{
auto buf_ = buf + i * 4;
auto o = buf_[0]; //save
auto x = buf_[0] ^ buf_[1] ^ buf_[2] ^ buf_[3];
auto c = buf_[0] ^ buf_[1];
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[0] ^= c;
c = buf_[1] ^ buf_[2];
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[1] ^= c;
c = buf_[2] ^ buf_[3];
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[2] ^= c;
c = buf_[3] ^ o;
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[3] ^= c;
}
}
void unxor_scroll(unsigned char buf[BLOCK_SIZE])
{
for (size_t i = 0; i < 4; i++)
{
auto buf_ = buf + i * 4;
for (size_t m = 0; m < 3; m++)
{
auto o = buf_[0]; //save
auto x = buf_[0] ^ buf_[1] ^ buf_[2] ^ buf_[3];
auto c = buf_[0] ^ buf_[1];
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[0] ^= c;
c = buf_[1] ^ buf_[2];
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[1] ^= c;
c = buf_[2] ^ buf_[3];
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[2] ^= c;
c = buf_[3] ^ o;
c = ((c >> 7) * 0x1b) ^ (c << 1);
c ^= x;
buf_[3] ^= c;
}
}
}
void encode(unsigned char buf[BLOCK_SIZE])
{
xor_block(0, buf);
for (size_t i = 1; i <= 9; i++)
{
transform(buf);
xchange_byte(buf);
xor_scroll(buf);
xor_block(i, buf);
}
transform(buf);
xchange_byte(buf);
xor_block(10, buf);
}
void decode(unsigned char buf[BLOCK_SIZE])
{
xor_block(10, buf);
unxchange_byte(buf);
untransform(buf);
for (size_t i = 9; i >= 1; i--)
{
xor_block(i, buf);
unxor_scroll(buf);
unxchange_byte(buf);
untransform(buf);
}
xor_block(0, buf);
}
int main()
{
unsigned char seri[] = { 151,236,123,124,167,118,20,22,154,17,142,13,87,141,244,244 }; //"l+x7fKd2FBaaEY4NV4309A==" Base64解码
java_crypt("keepGoing", seri);
decode(seri);
java_crypt("kaokaonio", seri);
cout << "seri: " << seri << endl;
return 0;
}
[CTF入门培训]顶尖高校博士及硕士团队亲授《30小时教你玩转CTF》，视频+靶场+题目！助力进入CTF世界
最后于 2020-11-24 09:37
被Anakin Stone编辑
，原因：
