bugku 的“一段Base64”是洋葱

bugku_crypto_onion.py

#!/usr/bin/env python3
# -*- encoding: utf-8 -*-

'''
	https://ctf.bugku.com/challenges#%E4%B8%80%E6%AE%B5Base64
'''

import base64
import html
from urllib import parse

# 打开文件
with open('1.txt') as f:
    cipher_base64 = f.read()

# base64 解密
cipher_oct = base64.b64decode(cipher_base64.encode()).decode()

# 8 进制分割成列表
list_oct = cipher_oct.split('\\')
list_oct.pop(0)
# 连接 8 进制数成 bytes 再成 str
cipher_hex = bytes([int(i, 8) for i in list_oct]).decode()

# 解析 16 进制数成 bytes
cipher_unicode = bytes.fromhex(cipher_hex.replace('\\x', ''))

# 解析 unicode_escape
# cipher_charcode = bytes.fromhex(cipher_unicode.replace('\\u00', '')).decode()
cipher_charcode = cipher_unicode.decode('unicode_escape')

# 取出括号中内容并分割 ascii 码
list_charcode = cipher_charcode[20:-1].split(',')

# 连接 ascii 码并转成 str
cipher_html_1 = bytes([int(i) for i in list_charcode]).decode()

# 解析 html 转义符两次
cipher_html_2 = html.unescape(cipher_html_1)
cipher_url = html.unescape(cipher_html_2)

# 解析 url 转义符
flag = parse.unquote(cipher_url)

print(flag)