February 7, 2023

西湖论剑 逆向

BabyRe

tips：
_initterm, _initterm_e
atexit：简单来说，就是程序正常退出之前，会调用atexit注册的函数，调用顺序是栈式的，即先注册后调用。

函数调用顺序：sub_401000（初始化，注册sub_405770） -> sub_401170（初始化，检查输入全为数字） -> sub_401050（调用sub_401230，注册sub_4057B0） -> sub_401230（处理后续使用的表） -> sub_4010A0（调用hook函数，注册sub_4057F0） -> sub_4012B0（将GetLastError函数hook为sub_4019D0，此函数修改了哈希常量） -> sub_401670（调用base加密并cmp） -> sub_4015C0（调用hash并cmp） -> sub_405770（RC4并cmp，最终输出结果）

整个加密流程为：将输入base8编码，然后取[16:112]与密文对比（即前6字节和后面的不可知），base8后的前16字节哈希后与密文对比，最后取输入的最后6字节作为RC4密钥加密[:112]
可以根据RC4爆破6字节密钥，获得base8后的密文

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#include<stdio.h>
#include<string.h>
#include<stdlib.h>

void rc4_init(unsigned char*s,unsigned char*key, unsigned long Len)
{
    int i=0,j=0;
    unsigned char k[256]={0};
    unsigned char tmp=0;
    for(i=0;i<256;i++) {
        s[i]=i;
        k[i]=key[i%Len];
    }
    for(i=0;i<256;i++) {
        j=(j+s[i]+k[i])%256;
        tmp=s[i];
        s[i]=s[j];
        s[j]=tmp;
    }
}

void rc4_crypt(unsigned char*s,unsigned char*Data,unsigned char*enc,unsigned long Len)
{
    int i=0,j=0,t=0;
    unsigned long k=0;
    unsigned char tmp;
    for(k=0;k<Len;k++)
    {
        i=(i+1)%256;
        j=(j+s[i])%256;
        tmp=s[i];
        s[i]=s[j];
        s[j]=tmp;
        t=(s[i]+s[j])%256;
        Data[k]=s[t]^enc[k];
    }
}

int main()
{
    unsigned char enc[] =
        {
        0x3F, 0x95, 0xBB, 0xF2, 0x57, 0xF1, 0x7A, 0x5A, 0x22, 0x61, 
        0x51, 0x43, 0xA2, 0xFA, 0x9B, 0x6F, 0x44, 0x63, 0xC0, 0x08, 
        0x12, 0x65, 0x5C, 0x8A, 0x8C, 0x4C, 0xED, 0x5E, 0xCA, 0x76, 
        0xB9, 0x85, 0xAF, 0x05, 0x38, 0xED, 0x42, 0x3E, 0x42, 0xDF, 
        0x5D, 0xBE, 0x05, 0x8B, 0x35, 0x6D, 0xF3, 0x1C, 0xCF, 0xF8, 
        0x6A, 0x73, 0x25, 0xE4, 0xB7, 0xB9, 0x36, 0xFB, 0x02, 0x11, 
        0xA0, 0xF0, 0x57, 0xAB, 0x21, 0xC6, 0xC7, 0x46, 0x99, 0xBD, 
        0x1E, 0x61, 0x5E, 0xEE, 0x55, 0x18, 0xEE, 0x03, 0x29, 0x84, 
        0x7F, 0x94, 0x5F, 0xB4, 0x6A, 0x29, 0xD8, 0x6C, 0xE4, 0xC0, 
        0x9D, 0x6B, 0xCC, 0xD5, 0x94, 0x5C, 0xDD, 0xCC, 0xD5, 0x3D, 
        0xC0, 0xEF, 0x0C, 0x29, 0xE5, 0xB0, 0x93, 0xF1, 0xB3, 0xDE, 
        0xB0, 0x70, 0
        };

    char key[8];
    unsigned char box[256], dec[150];
    int flag = 0;
    for(int i = 100000; i < 1000000; i++)
    {
        int len = 0;
        itoa(i, key, 10);
        rc4_init(box, key, strlen(key));
        rc4_crypt(box, dec, enc, strlen(enc));
        for(int k = 0; dec[k]; k++)
        {
            if(dec[k]<'0'||dec[k]>'9')
                break;
            len++;
        }
        if(len == strlen(enc))
        {
            printf("%s\n",dec);
            printf("%d",i);
            break;
        }
    }
    
    return 0;
}
/*
1523306115230466162304651523346214431471150310701503207116032063140334661543446114434066142304661563446615430464
807391
*/

对输出base8解码，打表或者直接逆都可以，得到明文561516915572239428449843076691286116796614，再接上key，得到561516915572239428449843076691286116796614807391，即为flag。

Berkeley

ebpf程序

strings得源码（在1.8k+行的地方）：

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for(int i=0; i<256; i++)
    unsigned char uc1 = flag[i/8];
    unsigned char uc2 = ~(flag[i/8] + arr[i%8]);
    output[i] = key[uc1 ^ uc2];
	output[i] = key[output[i] ^ key[i]];
	for(int i=0; i<256; i++)
	    if(output[i] != cipher[i])
	bpf_map_delete_elem(&execs, &pid);
int BPF_KRETPROBE(LBB0_2)
cipher

逆向得exp：

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key = [0xC1, 0xD1, 0x02, 0x61, 0xD6, 0xF7, 0x13, 0xA2, 0x9B, 0x20, 0xD0, 0x4A, 0x8F, 0x7F, 0xEE, 0xB9, 0x00, 0x63, 0x34, 0xB0, 0x33, 0xB7, 0x8A, 0x8B, 0x94, 0x60, 0x2E, 0x8E, 0x21, 0xFF, 0x90, 0x82, 0xD5, 0x87, 0x96, 0x78, 0x22, 0xB6, 0x48, 0x6C, 0x45, 0xC7, 0x5A, 0x16, 0x80, 0xFD, 0xE4, 0x8C, 0xBF, 0x01, 0x1F, 0x4B, 0x79, 0x24, 0xA0, 0xB4, 0x23, 0x4D, 0x3B, 0xC5, 0x5D, 0x6F, 0x0D, 0xC9, 0xD4, 0xCA, 0x55, 0xE0, 0x39, 0xAD, 0x2B, 0xCD, 0x2C, 0xEC, 0xC2, 0x6B, 0x30, 0xE6, 0x0C, 0xA8, 0x9A, 0x2F, 0xF6, 0xE8, 0xBB, 0x32, 0x57, 0xFB, 0x0B, 0x9D, 0xF2, 0x3F, 0xB5, 0xF9, 0x59, 0xE5, 0x10, 0xCF, 0x51, 0x41, 0xE9, 0x50, 0xDF, 0x26, 0x74, 0x58, 0xCB, 0x64, 0x54, 0x73, 0xAB, 0xF4, 0xB2, 0x9F, 0x18, 0xF8, 0x4E, 0xFE, 0x08, 0x1D, 0x4F, 0x49, 0xD3, 0xAC, 0x38, 0x12, 0x77, 0x11,
       0x69, 0x07, 0x1C, 0x99, 0xB3, 0xE7, 0x3D, 0x05, 0xD8, 0xFC, 0x70, 0x46, 0x93, 0x09, 0x65, 0x89, 0xB1, 0xC6, 0x52, 0xFA, 0xD2, 0x0E, 0xA9, 0x17, 0xE3, 0x91, 0xA1, 0x68, 0x5B, 0x2A, 0xF0, 0xC3, 0x42, 0xCC, 0x29, 0xDE, 0xDC, 0x85, 0x98, 0x31, 0x5C, 0xBC, 0x2D, 0xEF, 0x5E, 0x7E, 0xAF, 0x67, 0x62, 0xA7, 0x56, 0x88, 0xA4, 0x43, 0x40, 0xE1, 0x37, 0x9E, 0x36, 0x76, 0x71, 0x84, 0xBD, 0x06, 0x8D, 0x47, 0x7D, 0x53, 0xD7, 0xC8, 0xCE, 0x15, 0x92, 0x95, 0x4C, 0x28, 0x6D, 0x75, 0xEB, 0x7C, 0xF3, 0xBE, 0xAA, 0xB8, 0xED, 0x03, 0x3C, 0x27, 0x3E, 0x19, 0xDD, 0xA6, 0x66, 0x25, 0x1E, 0xC4, 0x6E, 0xC0, 0xE2, 0xDB, 0x3A, 0xD9, 0x81, 0xA5, 0x1B, 0xF5, 0x04, 0xAE, 0xBA, 0xEA, 0x97, 0x83, 0x35, 0x44, 0xA3, 0x7A, 0x1A, 0xF1, 0x86, 0xDA, 0x7B, 0x14, 0x72, 0x9C, 0x6A, 0x0F, 0x5F, 0x0A, ]
cipher = [0xF3, 0x27, 0x47, 0x1B, 0x8F, 0x09, 0xFB, 0x17, 0x70, 0x48, 0xB0, 0x53, 0x32, 0xDB, 0xC0, 0xB8, 0x63, 0x2D, 0x40, 0x4B, 0xF5, 0x16, 0xF0, 0x35, 0xE7, 0xDF, 0xEA, 0xA2, 0x9C, 0x41, 0xB3, 0x25, 0xD7, 0x0C, 0x33, 0x9C, 0x7B, 0x5A, 0xCD, 0x13, 0xBB, 0xEE, 0x3E, 0x0E, 0xF2, 0xCF, 0x35, 0xDA, 0xAF, 0xA2, 0x66, 0x7D, 0x38, 0x37, 0x67, 0x1E, 0x1F, 0x6B, 0x7B, 0x30, 0x0B, 0x7A, 0x02, 0xA9, 0xC8, 0x61, 0x27, 0x41, 0xDB, 0x01, 0x22, 0x31, 0x6F, 0xB6, 0xD4, 0x1B, 0x04, 0xD3, 0x94, 0xB8, 0x46, 0xC7, 0x24, 0xCF, 0xBD, 0xAF, 0x0B, 0xDC, 0x2E, 0xBB, 0xB2, 0x71, 0xF4, 0x99, 0x57, 0x36, 0xD1, 0x95, 0x52, 0x92, 0xBA, 0x6D, 0xF3, 0x30, 0x50, 0x59, 0x9B, 0xEA, 0x2F, 0x83, 0xDC, 0xF0, 0xDE, 0x57, 0xA1, 0xAC, 0xD2, 0x51, 0xA2, 0x1D, 0x59, 0xA8, 0x00, 0xB6, 0xE2, 0x65, 0x41,
          0x0C, 0x4F, 0xEB, 0xF0, 0x2E, 0x58, 0x2A, 0x1F, 0xF4, 0x95, 0x72, 0x88, 0x7C, 0xA9, 0x0E, 0xCB, 0x3C, 0x42, 0xB9, 0xF3, 0x49, 0x9B, 0x52, 0x98, 0x12, 0xA3, 0x17, 0x51, 0xC0, 0x59, 0x40, 0x0A, 0xBC, 0xE8, 0x4C, 0x04, 0xFB, 0x13, 0x0A, 0x17, 0x3F, 0xE6, 0x36, 0x97, 0xDF, 0xB3, 0xE2, 0x42, 0x7F, 0xF8, 0xCC, 0x0E, 0xD1, 0x77, 0xC4, 0xA8, 0x46, 0x48, 0xE3, 0xF1, 0x0A, 0xEF, 0x94, 0x56, 0x54, 0x5B, 0xCA, 0xBD, 0xDD, 0x7F, 0x56, 0x47, 0xC2, 0x99, 0xFA, 0x89, 0xCC, 0xE1, 0xB9, 0x3A, 0x78, 0xE2, 0x37, 0x58, 0x01, 0x1B, 0xC3, 0x4B, 0xE6, 0x8C, 0xF3, 0xE5, 0xB6, 0x71, 0x9E, 0x63, 0xAF, 0x11, 0xCE, 0x87, 0xF6, 0x6E, 0xDE, 0xC8, 0xB1, 0xD0, 0x7A, 0x15, 0x6C, 0x10, 0x08, 0x99, 0x7B, 0x22, 0x55, 0x10, 0x7A, 0x82, 0x73, 0xFC, 0x62, 0xCB, 0x34, 0xA7, 0xB7, 0x62, 0xFA, 0x6B, 0x9F]
arry = [0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01]
tmp = []
for i in range(256):
    tmp.append(key.index(cipher[i])^key[i])
for i in range(0,256,8):
    for j in range(0x20,0x7f):
        for k in range(8):
            if((j^(j+arry[k])^0xff)&0xff!=key.index(tmp[i+k])):
                break
        else:
            print(chr(j),end='')
#71c2ac98ac8d99a2e8a95111449a7393

被打

看到一个提取ir的方法，根据Lu1u师傅的博客操作即可

Dual personality

天堂之门 (Heaven’s Gate)

简而言之就是在32位程序里执行64位代码。sub_401120用于做出这种转换。
自己patch程序的32位标志为64位标志即可用64位IDA打开反汇编。

结合两个程序的代码自己看流程即可，数据可以调试取得，注意反调试的地方。（好吧！我调不对，我硬看的x）
加密一共有3段，第一段是加，第二段是移位，第三段是异或，但是我明明改了反调试的地方，最后一段取的异或数据还是不对啊啊啊啊啊，不知道哪里有问题（可能是后面改了，但是断点断不到64位代码里所以有点问题）
只能patch输出用交互取加密后的密文，然后跟前两段加密后的结果异或，得到用于异或的数据。

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#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<stdint.h>

#define rol(x,i) ((x<<i)|(x>>(64-i)))&0xffffffffffffffff
#define ror(x,i) ((x>>i)|(x<<(64-i)))&0xffffffffffffffff

int main()
{
    unsigned char enc[] = {0xAA, 0x4F, 0xF, 0xE2, 0xE4, 0x41, 0x99, 0x54, 0x2C, 0x2B, 0x84, 0x7E, 0xBC, 0x8F, 0x8B, 0x78, 0xD3, 0x73, 0x88, 0x5E, 0xAE, 0x47, 0x85, 0x70, 0x31, 0xB3, 0x9, 0xCE, 0x13, 0xF5, 0xD, 0xCA, 0};
    unsigned char my_enc[] = {37, 39, 98, 178, 84, 125, 194, 91, 4, 119, 146, 106, 4, 215, 13, 10, 90, 4, 127, 130, 74, 4, 119, 130, 74, 4, 119, 130, 74, 4, 119, 130, 74, 13, 10};
    unsigned char my_dec[32];
/*
x = 0x5DF966AE - 0x21524111
for(i = 0; i < 8; i++)
{
    (dword)input[i] += x;
    x ^= input[i];
}
rol8(input[0], 12)
rol8(input[1], 34)
rol8(input[2], 56)
rol8(input[3], 14)

^????
*/
    uint32_t x = 0x5DF966AE - 0x21524111;
    uint32_t* t32_d = (uint32_t*)my_dec;
    uint32_t* t32_e = (uint32_t*)my_enc;
    uint64_t* t64_d = (uint64_t*)my_dec;
    uint64_t* t64_e = (uint64_t*)my_enc;
    int i;

    //encrypt
    for(i = 0; i < 32; i++)
        my_dec[i] = 'h';

    for(i = 0; i < 8; i++)
    {
        t32_d[i]+=x;
        x^=t32_d[i];
    }

    t64_d[0] = rol(t64_d[0], 12);

    //printf("%#x,", t64_d[0]^t64_e[0]);
    //0x4a827704

    //decrypt
    uint32_t* t32 = (uint32_t*)enc;
    uint64_t* t64 = (uint64_t*)enc;

    for(i = 0; i < 8; i++)
        t32[i]^=0x4a827704;

    t64[0] = ror(t64[0], 12);
    t64[1] = ror(t64[1], 34);
    t64[2] = ror(t64[2], 56);
    t64[3] = ror(t64[3], 14);

    x = 0x5DF966AE - 0x21524111;
    uint32_t t;
    for(i = 0; i < 8; i++)
    {
        t = t32[i];
        t32[i]-=x;
        x^=t;
    }

    for(i = 0; i < 32; i++)
    {
        printf("%c", enc[i]);
    }

    return 0;
}
//6cc1e44811647d38a15017e389b3f704

EasyVT

每次都会因为很傻逼的问题卡半年。。。

根据main函数里的指令对比常量表即可，wp很多我就不抄一遍了……
啊，我真是越来越懒了

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#include <stdio.h>
#include <stdint.h>
#include <string.h>

void decrypt (uint32_t* v, uint32_t* k) {
    uint32_t v0 = v[0], v1 = v[1];
    uint32_t delta = 0xC95D6ABF;
    uint32_t sum = 0x20000000;
    uint32_t k0 = k[0], k1 = k[1], k2 = k[2], k3 = k[3];
    for (int i=0; i<32; i++)  sum -= delta;
    for (int i=0; i<32; i++) {
        sum += delta;
        v1 -= (k2 + (v0 >> 5)) ^ (sum + v0) ^ (k3 + 16 * v0);
        v0 += (k0 + (v1 >> 5)) ^ (sum + v1) ^ (k1 + 16 * v1);
    }

    v[0]=v1; 
    v[1]=v0;
}


void rc4_init(unsigned char*s,unsigned char*key, unsigned long Len)
{
    int i=0,j=0;
    unsigned char k[256]={0};
    unsigned char tmp=0;
    for(i=0;i<256;i++) {
        s[i]=i;
        k[i]=key[i%Len];
    }
    for(i=0;i<256;i++) {
        j=(j+s[i]+k[i])%256;
        tmp=s[i];
        s[i]=s[j];
        s[j]=tmp;
    }
}

void rc4_crypt(unsigned char*s,unsigned char*Data,unsigned long Len)
{
    int i=0,j=0,t=0;
    unsigned long k=0;
    unsigned char tmp;
    for(k=0;k<Len;k++)
    {
        i=(i+1)%256;
        j=(j+s[i])%256;
        tmp=s[i];
        s[i]=s[j];
        s[j]=tmp;
        t=(s[i]+s[j])%256;
        Data[k]=s[t];
    }
}
/*
op: 27,19,21,25,20,23,18,22,24,26
rc4_key: '04e52c7e31022b0b'
5,1,3,4,2,swap,rc4,swap,TEA
  k1_ = key_tea[1];  // 102030h, 40506070h, 8090A0B0h, 0C0D0E0F0h
  k0_ = key_tea[3];
  k3_ = key_tea[2];
  k2_ = key_tea[0];
*/
int main()
{
    unsigned char enc[] =
    {
        0x94, 0x39, 0x07, 0x5C, 0xB3, 0x5C, 0x80, 0x0D, 0x86, 0xA5, 
        0xDD, 0x87, 0x8E, 0xFB, 0x17, 0x03, 0x29, 0xEF, 0x20, 0x65, 
        0xAF, 0x87, 0x49, 0x5A, 0xA4, 0xC2, 0x2D, 0xEB, 0x0E, 0x47, 
        0xCF, 0x38, 0
    };

    uint32_t k[4]= {0xC0D0E0F0, 0x40506070, 0x102030, 0x8090A0B0};
    int i;

    for(i = 0; i < 8; i+=2)
        decrypt((uint32_t*)enc+i, k);

    unsigned char key[]={"04e52c7e31022b0b"};
    unsigned char s[256], box[8];

    rc4_init(s,key,strlen(key));
    rc4_crypt(s,box,8);
    for(i = 0; i < 32; i++)
        enc[i]^=box[i%8];

    uint32_t *enc32 = (uint32_t*)enc;
    for(i = 0; i < 8; i+=2)
    {
        uint32_t tmp = enc32[i];
        enc32[i] = enc32[i+1];
        enc32[i+1] = tmp;
    }
    printf("%s",enc);
    return 0;
}
//81920c3758be43705ba154bb8f599846

关于本文

本文作者 云之君, 许可由 CC BY-NC 4.0.