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[原创]羊城杯 re wp
2天前 1471

[原创]羊城杯 re wp

2天前
1471

羊城杯 re wp

题的质量还是可以,有些题因为遇到一些问题,没解出来。花时间来写wp一是巩固一些知识点,还有让更多的人可以互相学习。

BabySmc

看题目就知道代码肯定被smc处理过了,所以直接动调就ok,也没有反调试。

 

先看前面部分。

看看base64加密过程

密文和比较。

解密脚本

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import base64
 
t=[]
encstr = 'H>oQn6aqLr{DH6odhdm0dMe`MBo?lRglHtGPOdobDlknejmGI|ghDb<4'
xor = [0xa6, 0xa3, 0xa9, 0xac]
for i in range(len(encstr)):
    t.append(ord(encstr[i]) ^ xor[i % 4])
t[-1]=0xE4#由于最后一个是4,是补的,直接改为表中的一个就行。
base1 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
 
base = [0xE4, 0xC4, 0xE7, 0xC7, 0xE6, 0xC6, 0xE1, 0xC1, 0xE0, 0xC0,
        0xE3, 0xC3, 0xE2, 0xC2, 0xED, 0xCD, 0xEC, 0xCC, 0xEF, 0xCF,
        0xEE, 0xCE, 0xE9, 0xC9, 0xE8, 0xC8, 0xEB, 0xCB, 0xEA, 0xCA,
        0xF5, 0xD5, 0xF4, 0xD4, 0xF7, 0xD7, 0xF6, 0xD6, 0xF1, 0xD1,
        0xF0, 0xD0, 0xF3, 0xD3, 0xF2, 0xD2, 0xFD, 0xDD, 0xFC, 0xDC,
        0xFF, 0xDF, 0x95, 0x9C, 0x9D, 0x92, 0x93, 0x90, 0x91, 0x96,
        0x97, 0x94, 0x8A, 0x8E]
ans = ''
for i in t:
    ans += base1[base.index(i)]
print(ans)
print(base64.b64decode(ans))
#SangFor{XSAYT0u5DQhaxveIR50X1U13M-pZK5A0}

DeltX

这道题,流程很乱,通过动调看内存会使分析变的简单。但是也有坑,就是flag的大小写的问题,多试吧。

 

前面部分。

中间数据处理。

脚本

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#include<stdio.h>
 
int main()
{
    int a,b;
 
    for(a=0;a<=0xffff;a++)
    {
        b=0;
        b=(a-0x9393)&0xffff;
        if(a*b== 0xE5FD104)
        {
            printf("%X %X",a,b);
 
        }
    }
 }

解出所有数据,拼接起来得到,SangFor{2C7BD2BF862564BAED0B6B6EA94F15BC},但是不对,然后又一组一组的试,看看哪出了问题,发现是某一组大小写问题,得到SangFor{2C7BD2BF862564baED0B6B6EA94F15BC}

EasyVM

elf文件,代码也被加密了,也有自解密函数。

 

先看看main函数

然后vm内部就只有自己去慢慢调试分析大概逻辑了。

 

大概有3中方式加密,前32个字符是异或,然后后面4个是一些运算的加密,后面8个字符又分为两组进行同一种运算方式方式加密。

 

写了个c来打印其过程。

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#include<stdio.h>
 
int main()
{
    int opcode[]={ 0xA1, 0xC1, 0x00, 0xB1, 0x77, 0xC2, 0x4A, 0x01, 0x00, 0x00,
  0xC1, 0x01, 0xB2, 0x77, 0xC2, 0x19, 0x01, 0x00, 0x00, 0xC1,
  0x02, 0xB4, 0x77, 0xC2, 0xDD, 0x01, 0x00, 0x00, 0xC1, 0x03,
  0xB3, 0x77, 0xC2, 0x0F, 0x01, 0x00, 0x00, 0xC1, 0x04, 0xB2,
  0x77, 0xC2, 0x1B, 0x01, 0x00, 0x00, 0xC1, 0x05, 0xB4, 0x77,
  0xC2, 0x89, 0x01, 0x00, 0x00, 0xC1, 0x06, 0xB1, 0x77, 0xC2,
  0x19, 0x01, 0x00, 0x00, 0xC1, 0x07, 0xB3, 0x77, 0xC2, 0x54,
  0x01, 0x00, 0x00, 0xC1, 0x08, 0xB1, 0x77, 0xC2, 0x4F, 0x01,
  0x00, 0x00, 0xC1, 0x09, 0xB1, 0x77, 0xC2, 0x4E, 0x01, 0x00,
  0x00, 0xC1, 0x0A, 0xB3, 0x77, 0xC2, 0x55, 0x01, 0x00, 0x00,
  0xC1, 0x0B, 0xB3, 0x77, 0xC2, 0x56, 0x01, 0x00, 0x00, 0xC1,
  0x0C, 0xB4, 0x77, 0xC2, 0x8E, 0x00, 0x00, 0x00, 0xC1, 0x0D,
  0xB2, 0x77, 0xC2, 0x49, 0x00, 0x00, 0x00, 0xC1, 0x0E, 0xB3,
  0x77, 0xC2, 0x0E, 0x01, 0x00, 0x00, 0xC1, 0x0F, 0xB1, 0x77,
  0xC2, 0x4B, 0x01, 0x00, 0x00, 0xC1, 0x10, 0xB3, 0x77, 0xC2,
  0x06, 0x01, 0x00, 0x00, 0xC1, 0x11, 0xB3, 0x77, 0xC2, 0x54,
  0x01, 0x00, 0x00, 0xC1, 0x12, 0xB2, 0x77, 0xC2, 0x1A, 0x00,
  0x00, 0x00, 0xC1, 0x13, 0xB1, 0x77, 0xC2, 0x42, 0x01, 0x00,
  0x00, 0xC1, 0x14, 0xB3, 0x77, 0xC2, 0x53, 0x01, 0x00, 0x00,
  0xC1, 0x15, 0xB1, 0x77, 0xC2, 0x1F, 0x01, 0x00, 0x00, 0xC1,
  0x16, 0xB3, 0x77, 0xC2, 0x52, 0x01, 0x00, 0x00, 0xC1, 0x17,
  0xB4, 0x77, 0xC2, 0xDB, 0x00, 0x00, 0x00, 0xC1, 0x18, 0xB1,
  0x77, 0xC2, 0x19, 0x01, 0x00, 0x00, 0xC1, 0x19, 0xB4, 0x77,
  0xC2, 0xD9, 0x00, 0x00, 0x00, 0xC1, 0x1A, 0xB1, 0x77, 0xC2,
  0x19, 0x01, 0x00, 0x00, 0xC1, 0x1B, 0xB3, 0x77, 0xC2, 0x55,
  0x01, 0x00, 0x00, 0xC1, 0x1C, 0xB2, 0x77, 0xC2, 0x19, 0x00,
  0x00, 0x00, 0xC1, 0x1D, 0xB3, 0x77, 0xC2, 0x00, 0x01, 0x00,
  0x00, 0xC1, 0x1E, 0xB1, 0x77, 0xC2, 0x4B, 0x01, 0x00, 0x00,
  0xC1, 0x1F, 0xB2, 0x77, 0xC2, 0x1E, 0x00, 0x00, 0x00, 0xC1,
  0x20, 0x80, 0x02, 0x18, 0x00, 0x00, 0x00, 0x23, 0x10, 0xC1,
  0x21, 0x80, 0x02, 0x10, 0x00, 0x00, 0x00, 0x23, 0xF7, 0xC1,
  0x22, 0x80, 0x02, 0x08, 0x00, 0x00, 0x00, 0x23, 0xF7, 0xC1,
  0x23, 0xF7, 0xFE, 0x80, 0x02, 0x05, 0x00, 0x00, 0x00, 0x22,
  0x77, 0x10, 0x80, 0x02, 0x07, 0x00, 0x00, 0x00, 0x23, 0x80,
  0x02, 0x23, 0x77, 0xF1, 0x98, 0x31, 0x77, 0x10, 0x80, 0x02,
  0x18, 0x00, 0x00, 0x00, 0x23, 0x80, 0x02, 0x20, 0xB9, 0xE4,
  0x35, 0x31, 0x77, 0x10, 0x80, 0x02, 0x12, 0x00, 0x00, 0x00,
  0x22, 0x77, 0xA0, 0xC1, 0x24, 0x80, 0x02, 0x18, 0x00, 0x00,
  0x00, 0x23, 0x10, 0xC1, 0x25, 0x80, 0x02, 0x10, 0x00, 0x00,
  0x00, 0x23, 0xF7, 0xC1, 0x26, 0x80, 0x02, 0x08, 0x00, 0x00,
  0x00, 0x23, 0xF7, 0xC1, 0x27, 0xF7, 0xFE, 0x32, 0x20, 0x43,
  0x33, 0x77, 0x80, 0x02, 0x11, 0x00, 0x00, 0x00, 0x22, 0x35,
  0x37, 0x38, 0x77, 0x80, 0x02, 0x0D, 0x00, 0x00, 0x00, 0x23,
  0x77, 0x38, 0x39, 0x10, 0x32, 0x20, 0x43, 0x33, 0x77, 0x80,
  0x02, 0x11, 0x00, 0x00, 0x00, 0x22, 0x35, 0x37, 0x38, 0x77,
  0x80, 0x02, 0x0D, 0x00, 0x00, 0x00, 0x23, 0x77, 0x38, 0x39,
  0xC7, 0xC1, 0x28, 0x80, 0x02, 0x18, 0x00, 0x00, 0x00, 0x23,
  0x10, 0xC1, 0x29, 0x80, 0x02, 0x10, 0x00, 0x00, 0x00, 0x23,
  0xF7, 0xC1, 0x2A, 0x80, 0x02, 0x08, 0x00, 0x00, 0x00, 0x23,
  0xF7, 0xC1, 0x2B, 0xF7, 0xFE, 0x32, 0x20, 0x43, 0x33, 0x77,
  0x80, 0x02, 0x11, 0x00, 0x00, 0x00, 0x22, 0x35, 0x37, 0x38,
  0x77, 0x80, 0x02, 0x0D, 0x00, 0x00, 0x00, 0x23, 0x77, 0x38,
  0x39, 0x10, 0x32, 0x20, 0x43, 0x33, 0x77, 0x80, 0x02, 0x11,
  0x00, 0x00, 0x00, 0x22, 0x35, 0x37, 0x38, 0x77, 0x80, 0x02,
  0x0D, 0x00, 0x00, 0x00, 0x23, 0x77, 0x38, 0x39, 0xC8, 0x99};
  int i=0;
  while ( 1 )
  {
    if ( opcode[i] == 0x71 )
    {
      printf("table[6] -= 4\n");
      printf("*table[6] = 0x%x\n",opcode[i+1]);
      i += 5;
    }
    if ( opcode[i]  == 0x41 )
    {
      printf("table[1] += table[2]\n");
      ++i;
    }
    if ( opcode[i]  == 0x42 )
    {
      printf("table[1] -= table[4];\n");
      ++i;
    }
    if ( opcode[i]  == 0x43 )
    {
      printf("table[1] *= table[3];\n");
      ++i;
    }
    if ( opcode[i]  == 0x37 )
    {
 
      printf("table[1] = table[5];\n");
      ++i;
    }
    if ( opcode[i]  == 0x38 )
    {
      printf("table[1] ^= table[4];\n");
      ++i;
    }
    if ( opcode[i]  == 0x39 )
    {
      printf("table[1] ^= table[5];\n");
      ++i;
    }
    if ( opcode[i]  == 0x35 )
    {
      printf("table[5] = table[1];\n");
      ++i;
    }
    if ( opcode[i]  == 0xF7 )
    {
     printf("table[9] += table[1];\n");
      ++i;
    }
    if ( opcode[i]  == 0x44 )
    {
      printf("table[1] /= table[5];\n");
      ++i;
    }
    if ( opcode[i]  == 0x80 )
    {
      printf("table[2] = 0x%x\n",*((unsigned int*)(&opcode[i+2])));
      i += 6;
    }
    if ( opcode[i]  == 0x77 )
    {
      printf("table[1] ^= table[9];\n");
      ++i;
    }
    if ( opcode[i]  == 0x53 )
    {
      printf("(sub_8048580)(*table[3]);\n");
      i += 2;
    }
    if ( opcode[i]  == 0x22 )
    {
      printf("table[1] >>= table[2];\n");
      ++i;
    }
    if ( opcode[i]  == 0x23 )
    {
         printf("table[1] <<= table[2];\n");
      ++i;
    }
    if ( opcode[i]  == 0x99 )
    {
        printf("out\n");
        break;
    }
 
    if ( opcode[i]  == 0x76 )
    {
      printf("table[3] = *table[6];\n");
      printf("*table[6] = 0;\n");
      printf("table[6] += 4;\n");
      i += 5;
    }
    if ( opcode[i]  == 0x54 )
    {
      printf("v6 = table[3];\n");
      printf("*v6 = sub_8048520();\n");
      i += 2;
    }
    if ( opcode[i]  == 0x30 )
    {
      printf("table[1] |= table[2];\n");
      ++i;
    }
    if ( opcode[i] == 0x31 )
    {
      printf("table[1] &= table[2];\n");
      ++i;
    }
    if ( opcode[i]  == 0x32 )
    {
      printf("table[3] = 0x%x\n",opcode[i+1]) ;
      i += 2;
    }
    if ( opcode[i]  == 9 )
    {
      printf("table[1] = 1877735783;\n");
      ++i;
    }
    if ( opcode[i]  == 0x10 )
    {
      printf("table[9] = table[1];\n");
      ++i;
    }
    if ( opcode[i]  == 0x33 )
    {
      printf("table[4] = table[1]\n");
      ++i;
    }
    if ( opcode[i]  == 0x34 )
    {
      printf("table[2] = 0x%x;",opcode[i+1]);
      i += 2;
    }
    if ( opcode[i]  == 0xFE )
    {
      printf("table[1] = table[9];\n");
      ++i;
    }
    if ( opcode[i]  == 0x11 )
    {
      printf("(sub_8048510)(&unk_8049340, table[1])\n");
      ++i;
    }
    if ( opcode[i]  == 0xA0 )
    {
      printf("if ( table[1] != 1877735783 )\nexit\n\n");
      ++i;
    }
    if ( opcode[i]  == 0xA1 )
    {
        printf("read\n");
      ++i;
    }
    if ( opcode[i]  == 0xB1 )
    {
      printf("table[9] = xor[0]\n");
      ++i;
    }
    if ( opcode[i]  == 0xB2 )
    {
      printf("table[9] = xor[1];\n");
      ++i;
    }
    if ( opcode[i]  == 0xA4 )
    {
      printf("xor[*(table[8] + 1)] = table[1];\n");
      i += 4;
    }
    if ( opcode[i]  == 0xB3 )
    {
     printf("table[9] = xor[2];\n");
      ++i;
    }
    if ( opcode[i] == 0xB4 )
    {
      printf("table[9] = xor[3];\n");
      ++i;
    }
    if ( opcode[i]  == 0xC1 )
    {
      printf("table[1] = flag[%d];\n",opcode[i+1]);
      i += 2;
    }
    if ( opcode[i]  == 0xC7 )
    {
         printf("dword_804B060 != table[1]\n\n");
      ++i;
    }
    if ( opcode[i]  == 0xC8 )
    {
         printf("dword_804B064 != table[1]\n\n");
      ++i;
    }
    if ( opcode[i]  == 0xC2 )
    {
      printf("if ( %d != table[1] )\n\n",opcode[i+1]);
      i+= 5;
    }
  }
}

前面32个字符如下结构,就是一个异或

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table[1] = flag[0];
table[9] = xor[0]
table[1] ^= table[9];
if ( 74 != table[1] )
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#里面的数据都是从opcode提出来的。
index=[0xb1,0xb2,0xb4,0xb3,0xb2,0xb4,0xb1,0xb3,0xb1,0xb1,0xb3,0xb3,0xb4,0xb2,0xb3,0xb1,0xb3,0xb3,0xb2,0xb1,0xb3,0xb1,0xb3,0xb4,0xb1,0xb4,0xb1,0xb3,0xb2,0xb3,0xb1,0xb2]
table={0xb1:0x7b,0xb2:0x2f,0xb3:0x37,0xb4:0xe8}
 
xor=[]
for i in index:
  xor.append(table[i])
print(xor)
enc=[0x4a,0x19,0xdd,0xf,0x1b,0x89,0x19,0x54,0x4f,0x4e,0x55,0x56,0x8e,0x49,0xe,0x4b,0x6,0x54,0x1a,0x42,0x53,0x1f,0x52,0xdb,0x19,0xd9,0x19,0x55,0x19,0x0,0x4b,0x1e]
for i in range(len(enc)):
  print(chr(enc[i]^xor[i]),end='')
#16584abc45baff901c59dde3b1bb6701

后4个字符逻辑如下

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table[1] = flag[32];
table[2] = 0x18
table[1] <<= table[2];
table[9] = table[1];
table[1] = flag[33];
table[2] = 0x10
table[1] <<= table[2];
table[9] += table[1];
table[1] = flag[34];
table[2] = 0x8
table[1] <<= table[2];
table[9] += table[1];
table[1] = flag[35];
table[9] += table[1];
table[1] = table[9];
table[2] = 0x5
table[1] >>= table[2];
table[1] ^= table[9];
table[9] = table[1];
table[2] = 0x7
table[1] <<= table[2];
table[2] = 0x98f17723
table[1] &= table[2];
table[1] ^= table[9];
table[9] = table[1];
table[2] = 0x18
table[1] <<= table[2];
table[2] = 0x35e4b920
table[1] &= table[2];
table[1] ^= table[9];
table[9] = table[1];
table[2] = 0x12
table[1] >>= table[2];
table[1] ^= table[9];
if ( table[1] != 1877735783 )
exit

需要特别注意的是里面的0x80对应的指令,比赛时就是在这花了很多时间,还好一步步调,最后找到了。

解法可以考虑爆破,4个字符,也不是很多。

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str="abcdefghijklmnopqrstuvwxyz0123456789"
 
for a in str:
  for b in str:
    for c in str:
      for d in str:
        table=[0]*10
        table[1] = ord(a)
        table[2] = 0x18
        table[1] <<= table[2]
        table[9] = table[1]
        table[1] =ord(b)
        table[2] = 0x10
        table[1] <<= table[2]
        table[9] += table[1]
        table[1] = ord(c)
        table[2] = 0x8
        table[1] <<= table[2]
        table[9] += table[1]
        table[1] = ord(d)
        table[9] = (table[9]+table[1])&0xffffffff
 
        table[1] = table[9]
        table[2] = 0x5
        table[1] >>= table[2]
        table[1] ^= table[9]
        table[9] = table[1]
        table[2] = 0x7
        table[1] <<= table[2]
        table[2] = 0x98f17723
        table[1] &= table[2]
        table[1] ^= table[9]
        table[9] = table[1]
        table[2] = 0x18
        table[1] <<= table[2]
        table[2] = 0x35e4b920
        table[1] &= table[2]
        table[1] ^= table[9]
        table[9] = table[1]
        table[2] = 0x12
        table[1] >>= table[2]
        table[1] ^= table[9]
        if(table[1]&0xffffffff==1877735783):
          print(a,b,c,d)
          break
#a 2 5 4

后面8个字符,加密过程也有坑,就是*和<<会产生溢出。也是考虑爆破解。

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str="abcdefghijklmnopqrstuvwxyz0123456789"
 
for a in str:
  for b in str:
    for c in str:
      for d in str:
        table=[0]*10
        table[1] = ord(a)
        table[2] = 0x18
        table[1] <<= table[2]
        table[9] = table[1]
        table[1] =ord(b)
        table[2] = 0x10
        table[1] <<= table[2]
        table[9] += table[1]
        table[1] = ord(c)
        table[2] = 0x8
        table[1] <<= table[2]
        table[9] += table[1]
        table[1] = ord(d)
        table[9] += table[1]
 
        table[1] = table[9]
        table[3] = 0x20
        table[1] = (table[1] *table[3])&0xffffffff
        table[4] = table[1]
        table[1] ^= table[9]
        table[2] = 0x11
        table[1] >>= table[2]
        table[5] = table[1]
        table[1] = table[5]
        table[1] ^= table[4]
        table[1] ^= table[9]
        table[2] = 0xd
        table[1]= (table[1] <<table[2])&0xffffffff
        table[1] ^= table[9]
        table[1] ^= table[4]
        table[1] ^= table[5]
        table[9] = table[1]
        table[3] = 0x20
        table[1] = (table[1] *table[3])&0xffffffff
        table[4] = table[1]
        table[1] ^= table[9]
        table[2] = 0x11
        table[1] >>= table[2]
        table[5] = table[1]
        table[1] = table[5]
        table[1] ^= table[4]
        table[1] ^= table[9]
        table[2] = 0xd
        table[1] =(table[1] <<table[2])&0xffffffff
        table[1] ^= table[9]
        table[1] ^= table[4]
        table[1] ^= table[5]
 
        if(table[1]&0xffffffff==0x283B8E84):
          print(a,b,c,d)
          break
        # table[1] = table[9]
        # table[3] = 0x20
        # table[1] *= table[3]
        # table[4] = table[1]
        # table[1] ^= table[9]
        # table[2] = 0x11
        # table[1] >>= table[2]
        # table[5] = table[1]
        # table[1] = table[5]
        # table[1] ^= table[4]
        # table[1] ^= table[9]
        # table[2] = 0xd
        # table[1] <<= table[2]
        # table[1] ^= table[9]
        # table[1] ^= table[4]
        # table[1] ^= table[5]
        # table[9] = table[1]
        # table[3] = 0x20
        # table[1] *= table[3]
        # table[4] = table[1]
        # table[1] ^= table[9]
        # table[2] = 0x11
        # table[1] >>= table[2]
        # table[5] = table[1]
        # table[1] = table[5]
        # table[1] ^= table[4]
        # table[1] ^= table[9]
        # table[2] = 0xd
        # table[1] <<= table[2]
        # table[1] ^= table[9]
        # table[1] ^= table[4]
        # table[1] ^= table[5]
#b06c dc23

得到SangFor{16584abc45baff901c59dde3b1bb6701a254b06cdc23}

ez_android

对apk的分析确实比较少,有点可惜,当时不知道为什么md5去网上解,没解出来,看来得多用几个网站。

 

拖到jeb看流程。

去看md5解密,现在网站解密又可以解出来了。。。654321

看看key怎么生成的

得到key

去看加密encode函数。

 

解密

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enc_md5 = bytearray.fromhex('c232666f1410b3f5010dc51cec341f58')
for i in enc_md5:
  print(hex(i+1).replace("0x",''),end='')
print("\n")
 
import base64
base1 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
t='3lkHi9iZNK87qw0p6U391t92qlC5rwn5iFqyMFDl1t92qUnL6FQjqln76l-P'
base = 'TGtUnkaJD0frq61uCQYw3-FxMiRvNOB/EWjgVcpKSzbs8yHZ257X9LldIeh4APom '
ans = ''
for i in t:
    ans += base1[base.index(i)]
print(ans)
print(base64.b64decode(ans))
#c33367701511b4f62ec61ded352059
#SangFor{212f4548-03d1-11ec-ab68-00155db3a27e}

safe box

Debug Blocker,这种技术还可以用来hookAPI,还是挺有意思,逆向工程核心原理中也有讲解,之前mrctf也遇到过,流程分析起还是不难,就是解的时候总是各种细节问题。。。。,后面看了师傅的wp来看看出现的问题。

 

浏览过整体框架可以知道,需要输入3个password。

 

先看看第一个,太大了 爆出来要等太久,用z3确实会快很多。

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from z3 import *
s = Solver()
Seed = BitVec('passwd', 64)
v2 = (Seed % 0x2540BE3FF)&0xff
v3 = ((Seed % 0x2540BE3FF) >> 8) & 0xF
v4 = ((Seed % 0x2540BE3FF) >> 20) & 0xFFF
v5 = v2 + 1
v6 = ((Seed % 0x2540BE3FF) >> 12)&0xff
v7 = v3 + 1
v8 = v4 + ~v2
v9 = v4
v10 = 21 * v6
for i in range(16):
  v3 += v3 ^ v8
  v2 += v4 | v2 & v7
  v9 += (v10 + v9) % v5
  v6 += v6 / v7
 
s.add(v3 == 0x38006F1)
s.add(v2 == 0x7291)
s.add(v9 == 0x8B3)
s.add(v6 == 0x80)
s.add(Seed > 0, Seed <= 0xffffffff)
 
if s.check() == sat:
  print(s.model())
else:
  print('Not Found!')
#0x72335f31
#r3_1

输入完password1后就会触发一个int3异常,动调看看,注意main函数中的IsDebuggerPresent(),断点打在sub_140001270()中,也就是程序自己的异常处理函数。

然后去新exe查看该函数,0014000187F处p键

所以password2就是10个字符分5组进行xtea加密,xtea解密如下

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#include<stdio.h>
 
void decrypt(unsigned int r ,unsigned int *code ,unsigned int *key)
{
    unsigned int v0,v1,i,delta=0x12345678;
    unsigned int sum=delta*32;
 
    v0=code[0];
    v1=code[1];
    for(i=0;i<32;i++)
    {
 
        v1-=( ((v0<<5) ^(v0>>6)) +v0 ) ^ ( sum + key[ (sum>>11)&3 ]);
        sum-=delta;
        v0-=( ((v1<<5) ^ (v1>>6)) +v1 ) ^ ( sum + key[sum&3] );
 
    }
    code[0]=v0;
    code[1]=v1;
    printf("%c%c",code[0],code[1]);
}
 
 
 
int main()
{
    unsigned int key[4]={0x47,0x57,0x48,0x54};
    unsigned int r=32;
    unsigned int code[10]={0x36C128C5, 0x0C4799A63, 0x0E8013E6C, 0x0A9F49003, 0x607EF54A,0x542C2DDF, 0x558BD01C, 0x65512CA2, 0x0BE1E3D05, 0x3C467DAD};
    int i;
 
    for(i=0;i<5;i++)
    {
        decrypt(32,&code[i*2],key);
    }
 
}
//S_s0_fuNny

password3,引发异常,伪随机数。

然后直接set,ip动调,得到rand()产生的数,虽然生成了32个,实际上只用了前16个。

然后看看乱序函数,通过看比较部分就行了。

问题就来了怎么逆回去,yyds的bxb师傅用了一个小技巧,rand()产生的数有两个字节,我们的字符只有一个字节,xor不会改变高字节的数,所以我们可以通过高字节的数来还原顺序,确实是比较妙,然后我是想直接自己输入假的字符串,然后得到假密文,从而知道乱序规律,然后逆回去,但是好像不可取,顺序还是乱的。

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# fake_flag=[0x00004126,0x00002f64,0x00005074,0x00007d08,0x000015e6,0x0000378c,0x00006fbb,0x00000d6b,0x00003f2a,0x0000413c,0x00000ebc,0x000010f8,0x00005c22,0x00001751,0x00001955,0x00001327]
# fake_enc=[0x00000029,0x00005074,0x00006fbb,0x0000378c,0x00004823,0x0000413c,0x00007d08,0x00000d6b,0x00003f2a,0x00006784,0x00006df1,0x00005af1,0x00001649,0x000041bb,0x000026e9,0x000001eb,0x00004126,0x00000ebc,0x00001955,0x00001327,0x00002f64,0x000015e6,0x000010f8,0x00005c22,0x00001751,0x000018be,0x00004ae1,0x00003d6c,0x00002cd6,0x000072ae,0x00006952,0x00005f90]
# print(hex(fake_enc[22]))
# index=[]
# for i in fake_flag:
#   index.append(fake_enc.index(i))
# print(index)
#这种不得行,得到的index是错误的。
enc=[0x10a7,0x3f72,0x413f,0x2f62,0x15da,0x5c10,0x174b,
     0x6c6b,0x37da,0x3653,0x1204,0x1d0,0x19e3,0x349e,
     0x60e2,0x40bf,0x1b1d,0x6f89,0xd5c,0x7d33,0x3785,
     0xebc,0x4118,0x5027,0x190a,0x1338,0x74f7,0x4350,
     0x3797,0x1dbb,0x2457,0x1f98]
 
enc1=[0x4118, 0x2F62, 0x5027, 0x7D33, 0x15DA, 0x3785,
0x6F89, 0x0D5C, 0x3F72, 0x413F, 0x0EBC, 0x10A7,
0x5C10, 0x174B, 0x190A, 0x1338]
rand=[0x4147, 0x2f06, 0x5017, 0x7d6c, 0x1583, 0x37ea, 0x6fdc, 0xd03, 0x3f43,
0x4156, 0xed7, 0x1094, 0x5c4f, 0x173f, 0x193a, 0x1357]
s=''
for i in range(16):
  s+=chr((enc1[i]^rand[i])&0xff)
print(s)
#_d0_YoU_1ik3_t0o

拼接一下GWHT{r3_1S_s0_fuNny_d0_YoU_1ik3_t0o}

OddCode

流下太菜了的泪水,有师傅已经发了详细的wp了,https://bbs.pediy.com/thread-269328.htm,tql,tql,也该学习一下高级一点的东西了。


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这虚拟机直接angr一把梭就行了
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