实际P2P OTR客户端 - 技术分析与披露

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#!/usr/bin/python
# NSA P2P Chat Client
# -*- coding: utf-8 -*-
import sys
import socket
import base64
import random
import string
import hashlib
from Crypto.Cipher import AES
from Crypto import Random
from threading import Thread
import getpass

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class CryptoClient(object):
    def __init__(self):
        print("欢迎使用CryptoChat，一个安全的P2P聊天客户端")
        print("你想要加密吗？好的，小伙子，开始吧！！！")
        self.IP = input("请输入要聊天的IP地址: ")
        self.PORT = int(input("请输入通信端口: "))
        print()
        print("现在为不同的加密方法输入密钥，请确保它们不同")
        print("出于安全考虑，密钥不会显示")
        print()
        self.EncryptKeyXOR = getpass.getpass("输入XOR加密的密钥: ")
        self.EncryptKeyAES = hashlib.md5(getpass.getpass("输入AES的安全密码: ").encode()).hexdigest()
        print()
        input("当两个客户端都准备好时按回车")
        ### AES填充处理
        BS = 16
        self.pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
        self.unpad = lambda s: s[:-ord(s[len(s) - 1:])]
        ### 启动聊天服务器和客户端
        try:
            Thread(target=self.RecvMSG, args=()).start()
        except socket.error as e:
            print(self.IP + " 还没准备好！当 " + self.IP + " 准备好时按回车")
            input()
            Thread(target=self.RecvMSG, args=()).start()
        self.SendMSG()

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    def EncryptAES(self, raw):
        raw = self.pad(raw)
        iv = Random.new().read(AES.block_size)
        cipher = AES.new(self.EncryptKeyAES.encode(), AES.MODE_CBC, iv)
        return base64.b64encode(iv + cipher.encrypt(raw.encode())).decode()

    def DecryptAES(self, enc):
        enc = base64.b64decode(enc)
        iv = enc[:16]
        cipher = AES.new(self.EncryptKeyAES.encode(), AES.MODE_CBC, iv)
        return self.unpad(cipher.decrypt(enc[16:])).decode()

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    def XOR(self, securekey, data, mode):
        if mode == 1:
            securekey = securekey[::-1]
        temp = ''
        for char in securekey:
            for x in data:
                temp += chr(ord(x) ^ ord(char))
            data = temp
            temp = ''
        return data

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    def EncryptMSG(self, data):
        data = self.XOR(self.EncryptKeyXOR, data, 0)
        data = self.EncryptAES(data)
        return data

    def DecryptMSG(self, data):
        data = self.DecryptAES(data)
        data = self.XOR(self.EncryptKeyXOR, data, 1)
        return data

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    def SendMSG(self):
        clientsock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  # UDP
        print()
        print("你现在正在与 '" + self.IP + "' 对话")
        while True:
            message = input("")
            if message.startswith("/send"):  # 发送文件命令
                self.SendFILE(message.split(" ")[1])
                continue
            if message == "/leave":
                message = self.EncryptMSG("\x03")
                clientsock.sendto(message.encode(), (self.IP, self.PORT))
                sys.exit(0)
            if message.startswith("/msg"):
                self.IP = message.split(" ")[1]
                print("[CLIENT] 你现在正在与 '" + self.IP + "' 对话")
                continue
            else:
                message = self.EncryptMSG("\x01" + message)
                clientsock.sendto(message.encode(), (self.IP, self.PORT))

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    def SendFILE(self, file_):
        if file_.startswith(".") or file_.startswith("/"):  # 安全措施
            print("[CLIENT] 出于安全和保护原因，不会发送以 '.' 或 '/' 开头的文件名。中止操作")
        else:
            clientsock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  # UDP
            data = "\x02" + file_ + "\xFF"
            with open(file_, "rb") as f:
                data += f.read()
            data = self.EncryptMSG(data)
            clientsock.sendto(data.encode(), (self.IP, self.PORT))
            print("[CLIENT] 文件已发送！")

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    def RandStr(self, length):
        return ''.join(random.choice(string.ascii_letters) for _ in range(length))

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    def RecvMSG(self):
        serversocket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)  # UDP
        serversocket.bind(('', self.PORT))
        while True:
            data, addr = serversocket.recvfrom(1073741824)  # 缓冲区大小为1GB（用于大文件/图像）
            data = self.DecryptMSG(data.decode())
            if data.startswith("\x02"):
                filename = ''
                data = list(data)
                del data[0]
                for i in data:
                    if i == "\xFF":
                        break
                    else:
                        filename += i
                del data[0]  # 删除协议字符
                del data[:len(filename)]  # 删除文件结束字符
                if filename.startswith(".") or filename.startswith("/"):  # 尝试利用！
                    print("[!!!警报!!!] " + addr[0] + " 试图覆盖你的 " + filename)
                else:
                    print("[CLIENT] " + addr[0] + " 发送了 " + filename)
                    print("[CLIENT] 正在下载...")  # 下载那个东西
                    data = ''.join(data)
                    with open(filename, "wb") as f:
                        f.write(data.encode())
                    print("[CLIENT] 已保存")
            elif data.startswith("\x01"):  # 所有消息以"\x01"开头以防止文件垃圾邮件
                data = list(data)
                del data[0]
                data = ''.join(data)
                print("[" + addr[0] + "] >  |   " + data)
            elif data.startswith("\x03"):
                print("[CLIENT] " + addr[0] + " 已离开")
                sys.exit(0)

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if __name__ == "__main__":
    CryptoClient()