使用 python-rsa 加密消息时出现溢出异常

Question

我正在使用 Python 3 和 Python-rsa (https://stuvel.eu/rsa)，并且在加密消息时不断收到相同的错误：

> Traceback (most recent call last):
``File "client.py", line 65, in <module>
msgg = encrypt_text(pubkey, msg)
File "client.py", line 54, in encrypt_text
return rsa.encrypt(msg.encode(), pubkey)
File "C:\Users\N0t_an_admin\AppData\Local\Programs\Python\Python36-32\lib\s
-packages\rsa\pkcs1.py", line 170, in encrypt
padded = _pad_for_encryption(message, keylength)
File "C:\Users\N0t_an_admin\AppData\Local\Programs\Python\Python36-32\lib\s
-packages\rsa\pkcs1.py", line 87, in _pad_for_encryption
' space for %i' % (msglength, max_msglength))
OverflowError: 1 bytes needed for message, but there is only space for -10

代码：

def get_server_pub():
    pubkey = listener("serverpub").decode("utf-8")
    pubkey = pubkey.strip(";")
    xd = rsa.PublicKey(n= int(pubkey[0]), e= int(pubkey[1]))
    return xd

def encrypt_text(pubkey, msg):
    return rsa.encrypt(msg.encode(), pubkey)


if __name__ == '__main__':
    print("Hello")
    if os.path.isfile('ckeys.json') == False:
        keys = createkeys()
        write_to_json_file('ckeys.json', keys)
    pubkey = get_server_pub()
    while True:
        msg = input("Message: ")
        msgg = encrypt_text(pubkey, msg)
        recived = listener(msgg)
        if not recived:
            continue
        print(recived)

文档说：

OverflowError – 当消息太大而无法放入填充块时。

Answer 1

检查该库的代码，应该归咎于这个部分

def _pad_for_encryption(message, target_length):
    r"""Pads the message for encryption, returning the padded message.
    :return: 00 02 RANDOM_DATA 00 MESSAGE
    >>> block = _pad_for_encryption(b'hello', 16)
    >>> len(block)
    16
    >>> block[0:2]
    b'\x00\x02'
    >>> block[-6:]
    b'\x00hello'
    """

    max_msglength = target_length - 11
    msglength = len(message)

    if msglength > max_msglength:
        raise OverflowError('%i bytes needed for message, but there is only'
' space for %i' % (msglength, max_msglength))

这里调用了那个方法

keylength = common.byte_size(pub_key.n)
padded = _pad_for_encryption(message, keylength)

似乎密钥长度计算不正确，因此 maxlength 为 -10。检查您是否获得了公钥。