Pycrypto 不一致地无法验证从文件加载的签名

Question

我正在尝试让一个程序对文件的内容进行签名，然后再验证这些内容。不过，第一次验证总是返回真，但一旦数据写入文件后再加载回来，验证通常会失败，有时却又能成功。

即使在代码失败的时候，两个 print signature 和 print hash.hexdigest() 的输出看起来是完全一样的。

我的测试代码是：

from Crypto.Hash import SHA256
from Crypto.PublicKey import RSA
from Crypto.Signature import PKCS1_PSS
def generate():
    key_file = open("TestPrivateKey")
    private_key = RSA.importKey(key_file)
    public_key = private_key.publickey()

    seed_file = open("Seed")

    plaintext = seed_file.read()

    hash = SHA256.new(plaintext)
    signer = PKCS1_PSS.new(private_key)
    signature =  signer.sign(hash)

    plaintext_file = open("plaintext", 'w')
    plaintext_file.write(plaintext)
    signature_file = open("signature", 'w')
    signature_file.write(signature)
    print signature
    print hash.hexdigest()

    verifier = PKCS1_PSS.new(public_key)

    print verifier.verify(hash, signature)

def verification_test():
    plaintext_file = open("plaintext")
    signature_file = open("signature", 'rb')

    plaintext = plaintext_file.read()
    public_key = RSA.importKey(open("TestPublicKey"))
    signature = signature_file.read()
    print signature

    hash = SHA256.new(plaintext)
    print hash.hexdigest()

    verifier = PKCS1_PSS.new(public_key)
    return verifier.verify(hash, signature)


if __name__ == '__main__':
    generate()
    print verification_test()

有没有人知道我犯了什么错误？在签名写入文件后再读取时，一定发生了什么事情，但我就是搞不清楚是什么。

补充：在运行这个脚本之前，我先运行了初始化函数：

from Crypto.PublicKey import RSA

def create_keys():
    private_key = RSA.generate(4096)
    file = open("TestPrivateKey", 'w')
    file.write(private_key.exportKey())
    file = open("TestPublicKey", 'w')
    file.write(private_key.publickey().exportKey())

def create_seed():
    file = open("Seed", 'w')
    file.write("Test")

Answer 1

我注意到你的代码有两个问题。

首先，你把一些随意的二进制数据写入了一个以文本模式打开的文件：

signature_file = open("signature", 'w')  #bad
signature_file.write(signature)

应该改成：

signature_file = open("signature", 'wb')  #good
signature_file.write(signature)

第二，你从来没有关闭你的文件。试试这个：

with open("signature", 'wb') as signature_file:
    signature_file.write(signature)

其他打开的文件也要这样处理。

---

from Crypto.Hash import SHA256
from Crypto.PublicKey import RSA
from Crypto.Signature import PKCS1_PSS
def generate():
    with open("TestPrivateKey") as key_file:
        private_key = RSA.importKey(key_file)
    public_key = private_key.publickey()

    with open("Seed") as seed_file:
        plaintext = seed_file.read()

    hash = SHA256.new(plaintext)
    signer = PKCS1_PSS.new(private_key)
    signature =  signer.sign(hash)

    with open("plaintext", 'w') as plaintext_file:
        plaintext_file.write(plaintext)
    with open("signature", 'wb') as signature_file:
        signature_file.write(signature)
    #print signature
    print hash.hexdigest()

    verifier = PKCS1_PSS.new(public_key)

    print verifier.verify(hash, signature)

def verification_test():
    with open("plaintext") as plaintext_file:
        plaintext = plaintext_file.read()
    with open("signature", 'rb') as signature_file:
        signature = signature_file.read()

    with open("TestPublicKey") as public_key_file:
        public_key = RSA.importKey(public_key_file)
    #print signature

    hash = SHA256.new(plaintext)
    print hash.hexdigest()

    verifier = PKCS1_PSS.new(public_key)
    return verifier.verify(hash, signature)


if __name__ == '__main__':
    generate()
    print verification_test()