DASCTF Oct X 吉林工师 逆向

魔法叠加

题目给了一个pyc和txt，先uncompyle6反编译一下，发现错误，那应该是pyc文件错误，修改文件头

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题目这是2.7的版本，修改一下，1个字节0x73为TYPE_CODE字段， 表示该字段为string格式，这段就是字节码的位置，7102这个多了，删除掉，修改34为32.

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修改好后可以正常反编译

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# uncompyle6 version 3.7.4
# Python bytecode 3.7 (3394)
# Decompiled from: Python 3.9.6 (tags/v3.9.6:db3ff76, Jun 28 2021, 15:26:21) [MSC v.1929 64 bit (AMD64)]
# Embedded file name: ./2.py
# Compiled at: 2021-10-20 11:56:04
# Size of source mod 2**32: 1928 bytes
import struct
O0O00O00O00O0O00O = [
 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', '#', '$', '%', '&', '(', ')', '*', '+', ',', '.', '/', ':', ';', '<', '=', '>', '?', '@', '[', ']', '^', '_', '`', '{', '|', '}', '~', '"']

def encode(O000O00000OO00OOO):
    """"""
    OOOO00OOO00O000OO = 0
    OOOOOOOOOO00O0OOO = 0
    OO0OOO000000OOOOO = ''
    for O0O0OO0OOOOOOOO00 in range(len(O000O00000OO00OOO)):
        O000O0OOOOO00O0O0 = O000O00000OO00OOO[O0O0OO0OOOOOOOO00:O0O0OO0OOOOOOOO00 + 1]
        OOOO00OOO00O000OO |= struct.unpack('B', O000O0OOOOO00O0O0)[0] << OOOOOOOOOO00O0OOO
        OOOOOOOOOO00O0OOO += 8
        if OOOOOOOOOO00O0OOO > 13:
            OO00O0OO00OOO000O = OOOO00OOO00O000OO & 8191
            if OO00O0OO00OOO000O > 88:
                OOOO00OOO00O000OO >>= 13
                OOOOOOOOOO00O0OOO -= 13
            else:
                OO00O0OO00OOO000O = OOOO00OOO00O000OO & 16383
                OOOO00OOO00O000OO >>= 14
                OOOOOOOOOO00O0OOO -= 14
            OO0OOO000000OOOOO += O0O00O00O00O0O0O0[(OO00O0OO00OOO000O % 91)] + O0O00O00O00O0O0O0[(OO00O0OO00OOO000O // 91)]

    if OOOOOOOOOO00O0OOO:
        OO0OOO000000OOOOO += O0O00O00O00O0O0O0[(OOOO00OOO00O000OO % 91)]
        if OOOOOOOOOO00O0OOO > 7 or OOOO00OOO00O000OO > 90:
            OO0OOO000000OOOOO += O0O00O00O00O0O0O0[(OOOO00OOO00O000OO // 91)]
    return OO0OOO000000OOOOO


O0O00O00O00O0O0O0 = []
OO000O00O00O0O0O0 = []
O0O0O0O0000O0O00O = input('plz input O0O0O0O0000O0O00O:\n')
for i in range(0, 52):
    O0O00O00O00O0O0O0 = O0O00O00O00O0O00O[i:] + O0O00O00O00O0O00O[0:i]
    O0O0O0O0000O0O00O = encode(O0O0O0O0000O0O00O.encode('utf-8'))

dic = open('./00.txt', 'a')
dic.write(O0O0O0O0000O0O00O)
dic.close

看着上面的加密像base，除91，应该是base91https://github.com/aberaud/base91-python

51次base91，每一次的表都做了一次移位，直接抄脚本解

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# -*- coding:utf-8 -*-

import struct

rawb91Maps = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',

           'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',

           'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',

           'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',

           '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '!', '#', '$',

           '%', '&', '(', ')', '*', '+', ',', '.', '/', ':', ';', '<', '=',

           '>', '?', '@', '[', ']', '^', '_', '`', '{', '|', '}', '~', '"']

def decode(encoded_str):

    ''' Decode Base91 string to a bytearray '''

    v = -1

    b = 0

    n = 0

    out = b''

    for strletter in encoded_str.decode():

        if not strletter in b91Table:

            continue

        c = b91Table[strletter]

        if v < 0:

            v = c

        else:

            v += c * 91

            b |= v << n

            n += 13 if (v & 8191) > 88 else 14

            while True:

                out += struct.pack('B', b & 255)

                b >>= 8

                n -= 8

                if not n > 7:

                    break

            v = -1

    if v + 1:

        out += struct.pack('B', (b | v << n) & 255)

    return out

 

b91MapArr = []

for i in range(0, 52):

    b91MapArr.append(rawb91Maps[i:] + rawb91Maps[0:i])

b91MapArr.reverse()

f= open("/home/giantbranch/桌面/wasm/00.txt", "rb")

strs = f.read()

 

for i in range(0, 52):

    b91Table = dict((v, k) for k, v in enumerate(b91MapArr[i]))

    strs = decode(strs).decode()

    print("round:", i)

 

print(strs)

3

马猴烧酒

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  strcpy(v12, "flag{this_is_fake_flag}");
  *(_OWORD *)v18 = 0i64;
  *(_OWORD *)Source = 0i64;
  v20 = 0i64;
  v21 = 0i64;
  *(_OWORD *)Destination = 0i64;
  *(__m128i *)v23 = _mm_load_si128((const __m128i *)&xmmword_140024A00);
  v12[31] = 0;
  v24 = _mm_load_si128((const __m128i *)&xmmword_1400249F0);
  v15 = 0;
  v22 = 0;
  v17 = 0;
  v9 = sub_14000B170(0i64);
  v3 = sub_14000B170(&v9);                      // 获取时间戳
  strcpy(Str2, "flag{");
  v4 = v3;
  *(_OWORD *)Str1 = 0i64;
  sub_140001020("please input your flag\n");
  sub_140001080("%s", Str1);
  if ( strncmp(Str1, Str2, 5ui64) || Str1[15] != 125 )
    goto LABEL_13;
  sub_1400040D0("You find it?");
  if ( IsDebuggerPresent() )
  {
LABEL_15:
    MessageBoxW(0i64, &Text, "-N璭", 0);
    exit(1);
  }
  if ( v4 != 1633831810 )
    goto LABEL_13;
  strcpy((char *)&base64, "abcdefghijklmnopqrstuvwxyz0123456789+/ABCDEFGHIJKLMNOPQRSTUVWXYZ");// base64
  sub_14000C3F8(1633831810, (__int64)Source, 10);// 赋值
  sub_1400010E0(Source);                        // 对时间戳base64加密
  v5 = -1i64;
  do
    ++v5;
  while ( Source[v5] );
  if ( v5 < 0x10 )
    goto LABEL_13;
  strncpy(Destination, Source, 0x10ui64);       // source赋值给Destination
  for ( i = 0i64; i < 16; ++i )
  {
    v12[i] ^= Destination[i];                   // 异或得到key
    if ( IsDebuggerPresent() )
      goto LABEL_15;
  }
  v10 = 1;
  sub_1400015F0((__int64)v11, (unsigned __int8 *)v12);
  sub_140001910(v11, Str1, v18);
  if ( !strncmp(v18, v23, 0x10ui64) )
    v7 = "Good job!\nyou get the flag.\n";
  else
LABEL_13:
    v7 = "You entered the wrong flag,please try again.\n";
  sub_140001020(v7);
  sub_140005864("pause");
  return 0;
}

先获取时间戳，如何base64变表，异或出key

魔改sm4

4

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// sm4.h
static const unsigned char SboxTable[16][16] =
{
    {0x48, 0x90, 0xE9, 0xFE, 0xCC, 0xE1, 0x3D, 0xB7, 0x16, 0xB6, 0x14, 0xC2, 0x28, 0xFB, 0x2C, 0x05},
    {0x2B, 0x67, 0x9A, 0x76, 0x2A, 0xBE, 0x04, 0xC3, 0xAA, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99},
    {0x9C, 0x42, 0x50, 0xF4, 0x91, 0xEF, 0x98, 0x7A, 0x33, 0x54, 0x0B, 0x43, 0xED, 0xCF, 0xAC, 0x62},
    {0xE4, 0xB3, 0x1C, 0xA9, 0xC9, 0x08, 0xE8, 0x95, 0x80, 0xDF, 0x94, 0xFA, 0x75, 0x8F, 0x3F, 0xA6},
    {0x47, 0x07, 0xA7, 0xFC, 0xF3, 0x73, 0x17, 0xBA, 0x83, 0x59, 0x3C, 0x19, 0xE6, 0x85, 0x4F, 0xA8},
    {0x68, 0x6B, 0x81, 0xB2, 0x71, 0x64, 0xDA, 0x8B, 0xF8, 0xEB, 0x0F, 0x4B, 0x70, 0x56, 0x9D, 0x35},
    {0x1E, 0x24, 0x0E, 0x5E, 0x63, 0x58, 0xD1, 0xA2, 0x25, 0x22, 0x7C, 0x3B, 0x01, 0x21, 0x78, 0x87},
    {0xD4, 0x00, 0x46, 0x57, 0x9F, 0xD3, 0x27, 0x52, 0x4C, 0x36, 0x02, 0xE7, 0xA0, 0xC4, 0xC8, 0x9E},
    {0xEA, 0xBF, 0x8A, 0xD2, 0x40, 0xC7, 0x38, 0xB5, 0xA3, 0xF7, 0xF2, 0xCE, 0xF9, 0x61, 0x15, 0xA1},
    {0xE0, 0xAE, 0x5D, 0xA4, 0x9B, 0x34, 0x1A, 0x55, 0xAD, 0x93, 0x32, 0x30, 0xF5, 0x8C, 0xB1, 0xE3},
    {0x1D, 0xF6, 0xE2, 0x2E, 0x82, 0x66, 0xCA, 0x60, 0xC0, 0x29, 0x23, 0xAB, 0x0D, 0x53, 0x4E, 0x6F},
    {0xD5, 0xDB, 0x37, 0x45, 0xDE, 0xFD, 0x8E, 0x2F, 0x03, 0xFF, 0x6A, 0x72, 0x6D, 0x6C, 0x5B, 0x51},
    {0x8D, 0x1B, 0xAF, 0x92, 0xBB, 0xDD, 0xBC, 0x7F, 0x11, 0xD9, 0x5C, 0x41, 0x1F, 0x10, 0x5A, 0xD8},
    {0x0A, 0xC1, 0x31, 0x88, 0xA5, 0xCD, 0x7B, 0xBD, 0x2D, 0x74, 0xD0, 0x12, 0xB8, 0xE5, 0xB4, 0xB0},
    {0x89, 0x69, 0x97, 0x4A, 0x0C, 0x96, 0x77, 0x7E, 0x65, 0xB9, 0xF1, 0x09, 0xC5, 0x6E, 0xC6, 0x84},
    {0x18, 0xF0, 0x7D, 0xEC, 0x3A, 0xDC, 0x4D, 0x20, 0x79, 0xEE, 0x5F, 0x3E, 0xD7, 0xCB, 0x39, 0xD6}
};
static const unsigned long CK[32] =
{
    0xF4BFE18F, 0xA8AA055C, 0x8B266D2B, 0xB3819D47, 0x0B1B3A85, 0xF7DB86B6, 0xC3279F82, 0x39D9C102,
    0xBEA224C9, 0xE75D4DAC, 0xAC61726C, 0x6F98AA6F, 0xFA2ADA4E, 0x6A7CFF92, 0xA8066E7B, 0x7BE32F9F,
    0x8CD0FED3, 0x4B98AF71, 0x790C2CBC, 0xBF880433, 0xAA46F582, 0x69C17A2C, 0x80BBD5E4, 0x24A02531,
    0x293D87B3, 0x75F159AD, 0xB750AE9D, 0x9886928C, 0x05577A22, 0xB425E19F, 0x124D4F63, 0xE26F66D1
};
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#include <stdio.h>
#include "sm4.h"
int main()
{
    sm4_context ctx;
    unsigned char key[16] = {0x0B, 0x18, 0x18, 0x29, 0x16, 0x3A, 0x5E, 0x27, 0x1E, 0x2B, 0x5F, 0x3F, 0x32, 0x07, 0x5C, 0x56};
    unsigned char enc[16] = {0xF7, 0xEB, 0x5E, 0x87, 0x17, 0x9C, 0x74, 0x94, 0x44, 0xB5, 0xF5, 0x12, 0xF9, 0x74, 0x15, 0x5F};
    unsigned char dec[16];
 
    sm4_setDecryptKey(&ctx, key);
    sm4_CryptoEcb(&ctx, 0, 16, enc, dec);
    for (int i = 0; i < 16; i++)
        printf("%c", dec[i]);
    printf("\n");
    return 0;
}