[NISACTF 2022]ezpython
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首先查壳
🆗 没有壳,然后反编译,没有发现任何有效信息【捂脸笑哭】
没办法了,去找大佬的wp
第一步先用pyinstxtractor解包
先去github下载pyinstxtractor,然后解压将它与要解包的文件放在同一目录下(需要安装 Python 环境。)打开终端运行 :
python pyinstxtractor.py ez_python.exe
然后将提取出的src.pyc反编译
(建议用uncompyle6 :pip install uncompyle6)
得到一段python代码:
# uncompyle6 version 3.9.3
# Python bytecode version base 3.4 (3310)
# Decompiled from: Python 3.13.0 (tags/v3.13.0:60403a5, Oct 7 2024, 09:38:07) [MSC v.1941 64 bit (AMD64)]
# Embedded file name: src.py
import rsa, base64
key1 = rsa.PrivateKey.load_pkcs1(base64.b64decode("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"))
key2 = rsa.PublicKey.load_pkcs1(base64.b64decode("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"))
def encrypt1(message):
crypto_text = rsa.encrypt(message.encode(), key2)
return crypto_text
def decrypt1(message):
message_str = rsa.decrypt(message, key1).decode()
return message_str
def encrypt2(tips, key):
ltips = len(tips)
lkey = len(key)
secret = []
num = 0
for each in tips:
if num >= lkey:
num = num % lkey
secret.append(chr(ord(each) ^ ord(key[num])))
num += 1
return base64.b64encode("".join(secret).encode()).decode()
def decrypt2(secret, key):
tips = base64.b64decode(secret.encode()).decode()
ltips = len(tips)
lkey = len(key)
secret = []
num = 0
for each in tips:
if num >= lkey:
num = num % lkey
secret.append(chr(ord(each) ^ ord(key[num])))
num += 1
return "".join(secret)
flag = "IAMrG1EOPkM5NRI1cChQDxEcGDZMURptPzgHJHUiN0ASDgUYUB4LGQMUGAtLCQcJJywcFmddNno/PBtQbiMWNxsGLiFuLwpiFlkyP084Ng0lKj8GUBMXcwEXPTJrRDMdNwMiHVkCBFklHgIAWQwgCz8YQhp6E1xUHgUELxMtSh0xXzxBEisbUyYGOx1DBBZWPg1CXFkvJEcxO0ADeBwzChIOQkdwXQRpQCJHCQsaFE4CIjMDcwswTBw4BS9mLVMLLDs8HVgeQkscGBEBFSpQFQQgPTVRAUpvHyAiV1oPE0kyADpDbF8AbyErBjNkPh9PHiY7O1ZaGBADMB0PEVwdCxI+MCcXARZiPhwfH1IfKitGOF42FV8FTxwqPzBPAVUUOAEKAHEEP2QZGjQVV1oIS0QBJgBDLx1jEAsWKGk5Nw03MVgmWSE4Qy5LEghoHDY+OQ9dXE44Th0="
key = "this is key"
try:
result = input("please input key: ")
if result == decrypt2("AAAAAAAAAAAfFwwRSAIWWQ==", key):
print(decrypt1(base64.b64decode(decrypt2(flag, result))))
elif result == key:
print("flag{0e26d898-b454-43de-9c87-eb3d122186bc}")
else:
print("key is error.")
except Exception as e:
pass
# okay decompiling src.pyc
分析代码,这段代码是 RSA + 异或加密 的验证脚本,但我们无需借助爆破手段或探寻复杂的漏洞,只需剖析其逻辑,便能获取Flag。
看下面的两个if分支
首先我注意到第2个分支直接给出了flag
elif result == key:
print("flag{0e26d898-b454-43de-9c87-eb3d122186bc}")
先提交试一下,
flag不正确,那么看第1个分支
if result == decrypt2("AAAAAAAAAAAfFwwRSAIWWQ==", key):
print(decrypt1(base64.b64decode(decrypt2(flag, result))))
这个分支的逻辑是:
用 key 解密一个固定的密文 "AAAAAAAAAAAfFwwRSAIWWQ==",得到一个“正确的密钥”。
然后,检查你的输入 result 是否等于这个“正确的密钥”。
如果相等,就用你的输入 result 作为密钥,去解密那个很长的 flag 密文。
那么我们就可以直接求出密钥,然后直接在python运行这个程序输入求出的密钥就可以得到正确的flag
密钥解密代码:
import base64
def decrypt2(secret, key):
# 1. Base64 解码
tips = base64.b64decode(secret.encode()).decode()
ltips = len(tips)
lkey = len(key)
secret_list = []
num = 0
# 2. 异或解密
for each in tips:
if num >= lkey:
num = num % lkey
secret_list.append(chr(ord(each) ^ ord(key[num])))
num += 1
return "".join(secret_list)
# 题目中的固定 Key
key = "this is key"
# 分支 1 的密文
target_secret = "AAAAAAAAAAAfFwwRSAIWWQ=="
# 计算分支 1 需要的真实密码
real_password = decrypt2(target_secret, key)
print(f"分支 1 需要的密钥是: [{real_password}]")
得到正确的密钥为:
this is true key
在python中运行这个程序输入this is true key得到flag

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