0x01 簡單Python

題目給了一個pyc文件，在線反編譯可以得到源碼

#!/usr/bin/env python
# encoding: utf-8
import base64

def encode(message):
    s = ''
    for i in message:
        x = ord(i) ^ 32
        x = x + 16
        s += chr(x)
    
    return base64.b64encode(s)

correct = 'eYNzc2tjWV1gXFWPYGlTbQ=='
flag = ''
print 'Input flag:'
flag = raw_input()
if encode(flag) == correct:
    print 'correct'
else:
    print 'wrong'

encode很簡單憔四，逐個字符與32異或然后在base64encode
由此直接寫decode

correct = 'eYNzc2tjWV1gXFWPYGlTbQ=='
def decode(correct):
    message = base64.b64decode(correct)
    print message
    flag = ''
    for i in message:
        x = ord(i) - 16
        print x
        x ^= 32
        flag += chr(x)
    return flag

print decode(correct)

得到flag ISCC{simple_pyc}

0x02 Rev02

送分題闰靴，直接用ida32載入可以看到check函數(shù)角溃，發(fā)現(xiàn)直接明文比對杠愧？利朵？律想？

  .method private hidebysig instance bool checkUsername()
                                        // CODE XREF: Employee_Payroll.employee_payroll__btnLogin_Click+1↑p
                                        // Employee_Payroll.employee_payroll__btnLogin_Click+5A2↑p
  {
    .maxstack 8
    ldarg.0
    ldfld    class [System.Windows.Forms]System.Windows.Forms.TextBox Employee_Payroll.employee_payroll::txtUsername
    callvirt instance string [System.Windows.Forms]System.Windows.Forms.Control::get_Text()
    ldstr    aAdmin                     // "admin"
    call     bool [mscorlib]System.String::op_Equality(string, string)
    brfalse.s loc_839
    ldc.i4.1
    ret
}
 .method private hidebysig instance bool checkPassword()
                                        // CODE XREF: Employee_Payroll.employee_payroll__btnLogin_Click+C↑p
                                        // Employee_Payroll.employee_payroll__btnLogin_Click+5AA↑p
  {
    .maxstack 8
    ldarg.0
    ldfld    class [System.Windows.Forms]System.Windows.Forms.TextBox Employee_Payroll.employee_payroll::txtPassword
    callvirt instance string [System.Windows.Forms]System.Windows.Forms.Control::get_Text()
    ldstr    aDghpc19pc19ub3            // "dGhpc19pc19ub3RfdGhlX2ZsYWdfeW91X3NlZWt"...
    call     bool [mscorlib]System.String::op_Equality(string, string)
    brfalse.s loc_859
    ldc.i4.1
    ret
}

明文如下

aAdmin:                                 // DATA XREF: Employee_Payroll.employee_payroll__checkUsername+B↑o
    text "UTF-16LE", "admin",0
aDghpc19pc19ub3:                        // DATA XREF: Employee_Payroll.employee_payroll__checkPassword+B↑o
    text "UTF-16LE", "dGhpc19pc19ub3RfdGhlX2ZsYWdfeW91X3NlZWtfa2VlcF9sb29"
    text "UTF-16LE", "raW5n",0

輸入username和password得到flag

3.PNG

？绍弟？技即？300分！

0x03 Rev1

這是一道rust逆向樟遣，也是第一次接觸而叼，機緣巧合看到入口函數(shù)
void beginer_reverse::main::h80fa15281f646bc1()

void beginer_reverse::main::h80fa15281f646bc1()
{
  __int64 v0; // rax
  volatile signed __int64 *v1; // rax
  __int64 v2; // r13
  signed __int64 v3; // rax
  __int64 v4; // rcx
  char v5; // dl
  signed __int64 v6; // r8
  char v7; // si
  char v8; // di
  int v9; // ebp
  int v10; // esi
  int v11; // edi
  unsigned int v12; // edx
  __int64 v13; // rcx
  unsigned __int64 v14; // rsi
  signed __int64 v15; // r14
  unsigned __int64 v16; // rbp
  int v17; // er12
  unsigned __int64 v18; // rbx
  signed __int64 v19; // rax
  signed __int64 v20; // rax
  __int64 v21; // rcx
  unsigned int tag; // edx
  __int64 v23; // rdx
  unsigned __int64 v24; // rsi
  __int64 v25; // rcx
  bool v26; // zf
  volatile signed __int64 *v27; // [rsp+0h] [rbp-B8h]
  __int64 v28; // [rsp+8h] [rbp-B0h]
  __int128 cin; // [rsp+10h] [rbp-A8h]
  __int128 v30; // [rsp+20h] [rbp-98h]
  unsigned __int64 v31; // [rsp+30h] [rbp-88h]
  __int64 v32; // [rsp+38h] [rbp-80h]
  __int64 v33; // [rsp+40h] [rbp-78h]
  __int128 v34; // [rsp+48h] [rbp-70h]
  void **v35; // [rsp+58h] [rbp-60h]
  __int128 v36; // [rsp+60h] [rbp-58h]
  void *v37; // [rsp+78h] [rbp-40h]
  __int64 v38; // [rsp+80h] [rbp-38h]

  _rust_alloc();
  if ( !v0 )
    alloc::alloc::handle_alloc_error::h9e3787e5722c870d();
  *(_OWORD *)v0 = xmmword_51000;
  *(_OWORD *)(v0 + 16) = xmmword_51010;
  *(_OWORD *)(v0 + 32) = xmmword_51020;
  *(_OWORD *)(v0 + 48) = xmmword_51030;
  *(_OWORD *)(v0 + 64) = xmmword_51040;
  *(_OWORD *)(v0 + 80) = xmmword_51050;
  *(_OWORD *)(v0 + 96) = xmmword_51060;
  *(_OWORD *)(v0 + 112) = xmmword_51070;
  *(_QWORD *)(v0 + 128) = 618475290964LL;
  v33 = v0;
  v34 = xmmword_51080;
  v28 = 1LL;
  cin = 0LL;
  std::io::stdio::stdin::hcd3fd1740d5196a7();
  v27 = v1;
  std::io::stdio::Stdin::read_line::h85c3421ca914511e();
  if ( v35 == (void **)&bitselm )               // check
  {
    v30 = v36;
    core::result::unwrap_failed::h2bf42cb74d1e7d4b(&unk_510D3, 19LL, &v30);
  }
  if ( !_InterlockedSub64(v27, 1uLL) )
    _$LT$alloc..sync..Arc$LT$T$GT$$GT$::drop_slow::h82dbb96617da66a0(&v27, &v27);
  v2 = v28;
  v3 = *((_QWORD *)&cin + 1);
  if ( *((_QWORD *)&cin + 1) )
  {
    v4 = *((_QWORD *)&cin + 1) + v28;
    v5 = *(_BYTE *)(*((_QWORD *)&cin + 1) + v28 - 1);
    v6 = 1LL;
    if ( v5 >= 0 )
    {
LABEL_7:
      v3 = *((_QWORD *)&cin + 1) - v6;
      *((_QWORD *)&cin + 1) = v3;
      v4 = v3 + v28;
      goto LABEL_23;
    }
    if ( v28 == v4 - 1 )
    {
      v10 = 0;
    }
    else
    {
      v7 = *(_BYTE *)(v4 - 2);
      if ( (*(_BYTE *)(v4 - 2) & 0xC0) == -128 )
      {
        if ( v28 == v4 - 2 )
        {
          v11 = 0;
        }
        else
        {
          v8 = *(_BYTE *)(v4 - 3);
          if ( (*(_BYTE *)(v4 - 3) & 0xC0) == -128 )
          {
            if ( v28 == v4 - 3 )
              v9 = 0;
            else
              v9 = (*(_BYTE *)(*((_QWORD *)&cin + 1) + v28 - 4) & 7) << 6;
            v11 = v9 | v8 & 0x3F;
          }
          else
          {
            v11 = v8 & 0xF;
          }
        }
        v10 = (v11 << 6) | v7 & 0x3F;
      }
      else
      {
        v10 = v7 & 0x1F;
      }
    }
    v12 = (v10 << 6) | v5 & 0x3F;
    if ( v12 != 1114112 )
    {
      if ( v12 >= 0x80 )
      {
        v6 = 2LL;
        if ( v12 >= 0x800 )
          v6 = 4LL - (v12 < 0x10000);
      }
      goto LABEL_7;
    }
  }
  else
  {
    v3 = 0LL;
    v4 = v28;
  }
LABEL_23:
  *(_QWORD *)&v30 = 4LL;
  *(__int128 *)((char *)&v30 + 8) = 0LL;
  if ( v3 )
  {
    v13 = v4 - v28;
    v14 = 0LL;
    v15 = 4LL;
    v16 = 0LL;
    v32 = v13;
    do
    {
      v17 = *(unsigned __int8 *)(v2 + v16);
      v18 = v14;
      if ( v16 == v14 )
      {
        v18 = v14 + 1;
        if ( v14 >= 0xFFFFFFFFFFFFFFFFLL )
          goto LABEL_68;
        if ( v18 < 2 * v14 )
          v18 = 2 * v14;
        if ( !is_mul_ok(4uLL, v18) )
LABEL_68:
          alloc::raw_vec::capacity_overflow::hbc659f170a622eae();
        if ( v14 )
        {
          _rust_realloc();
          v15 = v19;
          v13 = v32;
          if ( !v19 )
            goto LABEL_63;
        }
        else
        {
          _rust_alloc();
          v15 = v20;
          v13 = v32;
          if ( !v20 )
LABEL_63:
            alloc::alloc::handle_alloc_error::h9e3787e5722c870d();
        }
        *(_QWORD *)&v30 = v15;
        *((_QWORD *)&v30 + 1) = v18;
        v14 = v18;
      }
      *(_DWORD *)(v15 + 4 * v16++) = v17;
      v31 = v16;
    }
    while ( v13 != v16 );
  }
  else
  {
    v15 = 4LL;
    v18 = 0LL;
    v16 = 0LL;
  }
  v21 = 0LL;
  while ( 4 * v16 != v21 )
  {
    tag = *(_DWORD *)(v15 + v21) - 32;
    v21 += 4LL;
    if ( tag >= 0x5F )
      std::panicking::begin_panic::h770c088eb8f42530();
  }
  if ( v16 > *((_QWORD *)&v34 + 1) )
    v16 = *((_QWORD *)&v34 + 1);
  if ( !v16 )
  {
    if ( *((_QWORD *)&v34 + 1) )
      goto LABEL_52;
    goto LABEL_51;
  }
  v23 = 0LL;
  v24 = 0LL;
  v25 = 0LL;
  do
  {
    if ( v15 == v23 )
      break;
    v26 = ((*(_DWORD *)(v33 + 4 * v24) >> 2) ^ 0xA) == *(_DWORD *)(v15 + 4 * v24);
    ++v24;
    v25 += v26;
    v23 -= 4LL;
  }
  while ( v24 < v16 );
  if ( v25 == *((_QWORD *)&v34 + 1) )
  {
LABEL_51:
    v35 = &off_64F00;
    v36 = 1uLL;
    v37 = &unk_510C8;
    v38 = 0LL;
    std::io::stdio::_print::h77f73d11755d3bb8();
  }
LABEL_52:
  if ( v18 )
    _rust_dealloc();
  if ( (_QWORD)cin )
    _rust_dealloc();
  if ( (_QWORD)v34 )
    _rust_dealloc();
}

開頭寫入一堆密文，然后加密函數(shù)就一條
v26 = ((*(_DWORD *)(v33 + 4 * v24) >> 2) ^ 0xA) == *(_DWORD *)(v15 + 4 * v24);
所以直接寫腳本(注意小端序)

cipher = [0x00000154,0x00000180,0x000001FC,0x000001E4,
          0x000001F8,0x00000154,0x00000190,0x000001BC,
          0x000001BC,0x000001B8,0x00000154,0x000001F8,
          0x00000194,0x00000154,0x000001B4,0x000001BC,
          0x000001F8,0x00000154,0x000001F4,0x00000188,
          0x000001AC,0x000001F8,0x00000154,0x0000018C,
          0x000001E4,0x00000154,0x00000190,0x000001BC,
          0x000001BC,0x000001B8,0x000001BC,0x000001B8,
          0x00000154,0x00000090]

flag = ''
for i in cipher:
    flag += chr((i >> 2)  ^ 0xa)

print flag

#_just_need_to_get_what_is_needed_.

然后這是INS2019原題來著豹悬，更詳細的題解可以看

0x04 dig dig dig

終于看到一道像樣的逆向了葵陵，strings搜下字符串發(fā)現(xiàn)

ABCDEFGHH 
IJKLMNOPH 
QRSTUVWXH 
YZabcdefH
ghijklmnH 
opqrstuvH 
wxyz0123H 
456789+/H 

猜測常規(guī)base64 encode
繼續(xù)分析，ida64載入查看main函數(shù)偽代碼

__int64 __fastcall main(int a1, char **a2, char **a3)
{
  size_t v3; // rax
  char *flag; // ST18_8
  size_t flaglen; // rax
  const char *flagbase64; // rax
  const char *kaisa; // rax
  char *third; // ST18_8

  if ( a1 != 2 )
  {
    puts("./dec_dec_dec flag_string_is_here ");
    exit(0);
  }
  v3 = strlen(a2[1]);
  flag = (char *)malloc(v3 + 1);
  flaglen = strlen(a2[1]);
  strncpy(flag, a2[1], flaglen);
  flagbase64 = sub_860(flag);                   // base64 ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/
  kaisa = sub_F59(flagbase64);                  // 凱撒移位13瞻佛，特殊字符不移位
  third = (char *)sub_BE7(kaisa);
  if ( !strcmp(third, s2) )                     // '@1DE!440S9W9,2T%Y07=%<W!Z.3!:1T%S2S-),7-$/3T '
    puts("correct  :)");
  else
    puts("incorrect :(");
  return 0LL;
}

代碼就是將輸入也就是flag進行三輪變換之后與'@1DE!440S9W9,2T%Y07=%<W!Z.3!:1T%S2S-),7-$/3T '比對(注意末尾還有個空格)
依次分析sub_860 sub_F59 sub_BE7函數(shù)
大概看了一眼發(fā)現(xiàn)sub860很可能是base64 encode再仔細看來一下幾個特征位發(fā)現(xiàn)就是常規(guī)的base64 encode
接下來看sub_F59函數(shù)脱篙，發(fā)現(xiàn)也是常規(guī)的凱撒移位（移13位)
最后就剩下sub_BE7這個函數(shù)了，看不出是什么算法伤柄，只能手動逆之绊困，偽代碼如下

void *__fastcall sub_BE7(const char *second)
{
  unsigned int len; // ST1C_4
  _BYTE *v2; // rax
  _BYTE *ch1; // rax
  char v4; // dl
  _BYTE *ch2; // rax
  char v6; // cl
  _BYTE *ch3; // rax
  char v8; // cl
  _BYTE *ch4; // rax
  char v10; // dl
  _BYTE *v11; // rax
  char v12; // dl
  char *v13; // rax
  char v14; // dl
  _BYTE *v15; // rax
  char v16; // cl
  _BYTE *v17; // rax
  char v18; // cl
  _BYTE *v19; // rax
  char v20; // dl
  char *s; // [rsp+8h] [rbp-88h]
  unsigned int i; // [rsp+10h] [rbp-80h]
  signed int v24; // [rsp+14h] [rbp-7Ch]
  unsigned int v25; // [rsp+18h] [rbp-78h]
  signed __int64 v27; // [rsp+20h] [rbp-70h]
  signed __int64 ch2_0; // [rsp+20h] [rbp-70h]
  signed __int64 ch3_0; // [rsp+20h] [rbp-70h]
  signed __int64 ch4_0; // [rsp+20h] [rbp-70h]
  char *v27d; // [rsp+20h] [rbp-70h]
  signed __int64 v27e; // [rsp+20h] [rbp-70h]
  signed __int64 v27f; // [rsp+20h] [rbp-70h]
  signed __int64 v27g; // [rsp+20h] [rbp-70h]
  void *third; // [rsp+28h] [rbp-68h]

  s = (char *)second;
  len = strlen(second);
  third = malloc(4 * len / 3 + 1);
  v27 = (signed __int64)third;
  for ( i = len; i > 0x2D; i -= 45 )
  {
    v2 = (_BYTE *)v27++;
    *v2 = 77;
    v24 = 0;
    while ( v24 <= 44 )                         // last 44char//rank11
    {
      ch1 = (_BYTE *)v27;
      ch2_0 = v27 + 1;
      if ( *s >> 2 )
        v4 = ((unsigned __int8)*s >> 2) + 32;
      else
        v4 = 32;
      *ch1 = v4;
      ch2 = (_BYTE *)ch2_0;
      ch3_0 = ch2_0 + 1;
      if ( 16 * *s & 0x30 )
        v6 = (16 * *s & 0x30) + 32;
      else
        v6 = 32;
      *ch2 = v6 | ((unsigned __int8)s[1] >> 4);
      ch3 = (_BYTE *)ch3_0;
      ch4_0 = ch3_0 + 1;
      if ( 4 * s[1] & 0x3C )
        v8 = (4 * s[1] & 0x3C) + 32;
      else
        v8 = 32;
      *ch3 = v8 | ((unsigned __int8)s[2] >> 6);
      ch4 = (_BYTE *)ch4_0;
      v27 = ch4_0 + 1;
      if ( s[2] & 0x3F )
        v10 = (s[2] & 0x3F) + 32;
      else
        v10 = 32;
      *ch4 = v10;
      v24 += 3;
      s += 3;
    }
  }
  v11 = (_BYTE *)v27;
  v27d = (char *)(v27 + 1);
  if ( i )
    v12 = (i & 0x3F) + 32;
  else
    v12 = 32;
  *v11 = v12;
  v25 = 0;
  while ( v25 < i )
  {
    v13 = v27d;
    v27e = (signed __int64)(v27d + 1);
    if ( *s >> 2 )
      v14 = ((unsigned __int8)*s >> 2) + 32;
    else
      v14 = 32;
    *v13 = v14;
    v15 = (_BYTE *)v27e;
    v27f = v27e + 1;
    if ( 16 * *s & 0x30 )
      v16 = (16 * *s & 0x30) + 32;
    else
      v16 = 32;
    *v15 = v16 | ((unsigned __int8)s[1] >> 4);
    v17 = (_BYTE *)v27f;
    v27g = v27f + 1;
    if ( 4 * s[1] & 0x3C )
      v18 = (4 * s[1] & 0x3C) + 32;
    else
      v18 = 32;
    *v17 = v18 | ((unsigned __int8)s[2] >> 6);
    v19 = (_BYTE *)v27g;
    v27d = (char *)(v27g + 1);
    if ( s[2] & 0x3F )
      v20 = (s[2] & 0x3F) + 32;
    else
      v20 = 32;
    *v19 = v20;
    v25 += 3;
    s += 3;
  }
  *v27d = 0;
  return third;
}

由于最終的字符串只有45位再去掉第一位‘@’故只剩44位，所以這個函數(shù)有一半是無用代碼(雖然算法一樣适刀，但是可以不用看)秤朗，只需看第一個循環(huán)即可
加密算法不算很復(fù)雜，主要是一些移位操作有點煩蔗彤，容易出錯
算法主要就是將每3個字符24位分為一組依次取6位然后將之加上32轉(zhuǎn)換成字符川梅，即3個字符轉(zhuǎn)換成4個字符

由此可以得到總體的加密算法

#encode
#flag=base64.b64encode(flag)
#flag>>=13(kaisa)
#result='@'+message(len(message)==33)
#rank11
#rank
#res[0*rank] = mes[0*rank] >> 2 + 32
#res[1*rank] = mes[0*rank] & 0x03 + 32 | mes[1*rank] >> 4
#res[2*rank] = mes[1*rank] & 0x0f + 32 | mes[2*rank] >> 6
#res[3*rank] = mes[2*rank] & 0x3f + 32

由此可以寫出解密算法了

#!/usr/bin/env python
# encoding: utf-8

import base64

result = '@1DE!440S9W9,2T%Y07=%<W!Z.3!:1T%S2S-),7-$/3T '
rank3 = '1DE!440S9W9,2T%Y07=%<W!Z.3!:1T%S2S-),7-$/3T '

print 'rank3'
print rank3

rank2 = ''
for i in range(0,44,4):
    ch = ((ord(rank3[0+i]) - 32) << 2) + ((ord(rank3[1+i]) - 32 ) >> 4)
    rank2 += chr(ch&0xff)
    ch = ((ord(rank3[1+i]) - 32) << 4) + ((ord(rank3[2+i]) - 32 ) >> 2)
    rank2 += chr(ch&0xff)
    ch = ((ord(rank3[2+i]) - 32) << 6) + ((ord(rank3[3+i]) - 32 ) >> 0)
    rank2 += chr(ch&0xff)

print 'rank2'
print rank2

rank1 = ''
for i in rank2:
    if ord(i) >= ord('a') and ord(i) <= ord('z'):
        rank1 += chr((ord(i) - 0x61 + 13) % 26 + 0x61)
    elif ord(i) >= ord('A') and ord(i) <= ord('Z'):
        rank1 += chr((ord(i) - 0x41 + 13) % 26 + 0x41)
    else:
        rank1 += i

print 'rank1'
print rank1

flag = base64.b64decode(rank1)

print 'flag'
print flag

#flag 'ISCC{base64_rot13__uu}'
#rank1 'SVNDQ3tiYXNlNjRfcm90MTNfX3V1fQ=='
#rank2 'FIAQD3gvLKAyAwEspz90ZGAsK3I1sD=='
#rank3 '1DE!440S9W9,2T%Y07=%<W!Z.3!:1T%S2S-),7-$/3T '

得到flag ISCC{base64_rot13__uu}
看到flag才后知后覺發(fā)現(xiàn)最后一層加密算法是uuencode疯兼，還是too naive

0x05 rev3

rev3.exe: PE32 executable (GUI) Intel 80386 Mono/.Net assembly, for MS Windows
關(guān)于MSIL指令
https://www.cnblogs.com/lbq1221119/archive/2007/10/17/926919.html
.ctor定義了一段字符串"ABCDEFGHIJKLMNOPQRSTUVWXYZ{}_"
check函數(shù)在Button_Click

 ldfld    char[] FirstWPFApp.MainWindow::Letters
    ldc.i4.5
    ldelem.u2
    stelem.i2
    dup
    ldc.i4.1
    ldarg.0
    ldfld    char[] FirstWPFApp.MainWindow::Letters
    ldc.i4.s 0xE
    ldelem.u2
    stelem.i2
    dup
    ldc.i4.2
    ldarg.0
    ldfld    char[] FirstWPFApp.MainWindow::Letters
    ldc.i4.s 0xD
……
……

大致就是取字符串的第*位生成一個flag與輸入對比
手工匯編得到flag
Python>flag
FLAG{I_LOVE_FONZY}