C# 流读取器 ReadToEnd() 缺少最后一个字符

Question

我正在尝试使用 AES 解密 C# 中的字符串:

public static string AesDecrypt(byte[] cipherText, byte[] Key, byte[] IV)
{
    string plaintext = null;

    // Create an Aes object with the specified key and IV
    using Aes aesAlg = Aes.Create();
    aesAlg.Padding = PaddingMode.Zeros;
    aesAlg.Key = Key;
    aesAlg.IV = IV;

    // Create a decryptor to perform the stream transform
    ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

    // Create the streams used for decryption
    using MemoryStream msDecrypt = new MemoryStream(cipherText);
    using CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read);
    using StreamReader srDecrypt = new StreamReader(csDecrypt);

    // Read the decrypted bytes from the decrypting stream and place them in a string
    plaintext = srDecrypt.ReadToEnd();
    return plaintext;
}

编码数据是 JSON，但是当我解密它时，我得到了所有正确的数据，除了 JSON 内容的结束 } 丢失。

我认为 AES 本身不是我的问题。我有疑问

plaintext = srDecrypt.ReadToEnd();

因为只缺少最后一个字符。

我不知道我是否应该显式刷新任何流，但无论如何，这是一个非常奇怪的问题。

这是加密的完整代码:

public static string AesEncrypt(string plainText, byte[] Key, byte[] IV)
{
    // Create an Aes object with the specified key and IV
    using Aes aesAlg = Aes.Create();
    aesAlg.Padding = PaddingMode.Zeros;
    aesAlg.Key = Key;
    aesAlg.IV = IV;

    // Create an encryptor to perform the stream transform
    ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

    // Create the streams used for encryption
    using MemoryStream msEncrypt = new MemoryStream();
    using CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write);
    using StreamWriter swEncrypt = new StreamWriter(csEncrypt);

    // Write all data to the stream
    swEncrypt.Write(plainText);
    swEncrypt.Flush();

    return Convert.ToBase64String(msEncrypt.ToArray());
}

这就是我调用解密方法的方式:

public static AuthenticationData ParseAuthenticationToken(string token)
{
    byte[] tokenBytes = Convert.FromBase64String(token);
    string json = AesEncryption.AesDecrypt(tokenBytes, aes.Key, aes.IV);
    return JsonConvert.DeserializeObject<AuthenticationData>(json);
}

Answer 1

问题出在您的加密代码中。尽管您正在调用 seEncrypt.Flush()，但您并未调用 csEncrypt.FlushFinalBlock()。当流被释放时，这种情况会自动发生，但直到调用 msEncrypt.ToArray() 后才执行此操作。我会将该代码重写为:

MemoryStream msEncrypt = new MemoryStream();
using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
{
    using StreamWriter swEncrypt = new StreamWriter(csEncrypt);
    swEncrypt.Write(plainText);
    // swEncrypt is disposed here, flushing it. Then csEncrypt is disposed,
    // flushing the final block.
}
return msEncrypt.ToArray();