hellman/xortool用于分析多字节 XOR 密码的工具
一个用于进行异或（xor）分析的工具：
注意： xortool 现在仅支持 Python 3。旧的 Python 2 版本可在 py2 分支获取。pip 包已更新。
$ pip3 install xortool
开发或构建本仓库需要 poetry。
poetry build
pip install dist/xortool*.whl
xortool
A tool to do some xor analysis:
- guess the key length (based on count of equal chars)
- guess the key (base on knowledge of most frequent char)
Usage:
xortool [-x] [-m MAX-LEN] [-f] [-t CHARSET] [FILE]
xortool [-x] [-l LEN] [-c CHAR | -b | -o] [-f] [-t CHARSET] [-p PLAIN] [-r PERCENT] [FILE]
xortool [-x] [-m MAX-LEN| -l LEN] [-c CHAR | -b | -o] [-f] [-t CHARSET] [-p PLAIN] [-r PERCENT] [FILE]
xortool [-h | --help]
xortool --version
Options:
-x --hex input is hex-encoded str
-l LEN, --key-length=LEN length of the key
-m MAX-LEN, --max-keylen=MAX-LEN maximum key length to probe [default: 65]
-c CHAR, --char=CHAR most frequent char (one char or hex code)
-b --brute-chars brute force all possible most frequent chars
-o --brute-printable same as -b but will only check printable chars
-f --filter-output filter outputs based on the charset
-t CHARSET --text-charset=CHARSET target text character set [default: printable]
-p PLAIN --known-plaintext=PLAIN use known plaintext for decoding
-r PERCENT, --threshold=PERCENT threshold validity percentage [default: 95]
-h --help show this help
Notes:
Text character set:
* Pre-defined sets: printable, base32, base64
* Custom sets:
- a: lowercase chars
- A: uppercase chars
- 1: digits
- !: special chars
- *: printable chars
Examples:
xortool file.bin
xortool -l 11 -c 20 file.bin
xortool -x -c ' ' file.hex
xortool -b -f -l 23 -t base64 message.enc
xortool -b -p "xctf{" message.enc
xortool -r 80 -p "flag{" -c ' ' message.enc
# xor is xortool/xortool-xor
tests $ xor -f /bin/ls -s "secret_key" > binary_xored
tests $ xortool binary_xored
The most probable key lengths:
2: 5.0%
5: 8.7%
8: 4.9%
10: 15.4%
12: 4.8%
15: 8.5%
18: 4.8%
20: 15.1%
25: 8.4%
30: 14.9%
Key-length can be 5*n
Most possible char is needed to guess the key!
# 00 is the most frequent byte in binaries
tests $ xortool binary_xored -l 10 -c 00
...
1 possible key(s) of length 10:
secret_key
# decrypted ciphertexts are placed in ./xortool_out/Number_<key repr>
# ( have no better idea )
tests $ md5sum xortool_out/0_secret_key /bin/ls
29942e290876703169e1b614d0b4340a xortool_out/0_secret_key
29942e290876703169e1b614d0b4340a /bin/ls
最常见的用法是仅传入加密文件和最频繁字符（二进制文件通常为 00，文本文件通常为 20）——密钥长度将自动选择：
tests $ xortool tool_xored -c 20
The most probable key lengths:
2: 5.6%
5: 7.8%
8: 6.0%
10: 11.7%
12: 5.6%
15: 7.6%
20: 19.8%
25: 7.8%
28: 5.7%
30: 11.4%
Key-length can be 5*n
1 possible key(s) of length 20:
an0ther s3cret \xdd key
此处，密钥长度超过了默认的 32 限制：
tests $ xortool ls_xored -c 00 -m 64
The most probable key lengths:
3: 3.3%
6: 3.3%
9: 3.3%
11: 7.0%
22: 6.9%
24: 3.3%
27: 3.2%
33: 18.4%
44: 6.8%
55: 6.7%
Key-length can be 3*n
1 possible key(s) of length 33:
really long s3cr3t k3y... PADDING
因此，如果自动解密失败，你可以进行校准：
-m）最大长度，用于尝试更长的密钥-l）选定长度，用于查看一些有趣的密钥-c）最频繁字符，用于生成正确的明文我们得到一个经过 Base64 编码并与未知密钥进行 XOR 加密的消息。
# xortool message.enc
The most probable key lengths:
2: 12.3%
4: 13.8%
6: 10.5%
8: 11.5%
10: 8.6%
12: 9.4%
14: 7.1%
16: 7.8%
23: 10.4%
46: 8.7%
Key-length can be 4*n
Most possible char is needed to guess the key!
现在，我们可以一边过滤输出（仅保留符合 Base64 字符集的明文），一边测试密钥长度。在尝试若干长度后，我们找到了正确的长度，它只给出 1 个明文，且其中有效字符的百分比高于默认阈值 95%。
$ xortool message.enc -b -f -l 23 -t base64
256 possible key(s) of length 23:
\x01=\x121#"0\x17\x13\t\x7f ,&/\x12s\x114u\x170#
\x00<\x130"#1\x16\x12\x08~!-\'.\x13r\x105t\x161"
\x03?\x103! 2\x15\x11\x0b}".$-\x10q\x136w\x152!
\x02>\x112 !3\x14\x10\n|#/%,\x11p\x127v\x143
\x059\x165\'&4\x13\x17\r{$("+\x16w\x150q\x134\'
...
Found 1 plaintexts with 95.0%+ valid characters
See files filename-key.csv, filename-char_used-perc_valid.csv
通过按 Base64 字符集过滤输出，我们直接得到了唯一解。
作者：hellman
许可证：MIT License