c# RijndaelManaged 加密和解密有时会失败

Question

编辑：已解决 - 问题是解密功能。更正的解密函数可以在下面的答案中找到。

我在工作的最后一天试图弄清楚我在这个 AES 实现中出了什么问题。我们需要能够 encrypt/decrypt 大文件，所以我使用文件流并将每个块写入磁盘。 AES 是一项要求，因为这需要与使用 java 编写的现有系统一起使用，该系统使用 AES/CBC/PKCS5Padding（据我所知相当于 PKCS7/CBC）

此实现适用于大多数 文件。但是，有一些文件缺少原始数据的最后 5 个字节。该文件将解密而不会出现错误，但哈希值不匹配，丢失的字节是真实数据和尾随零的组合。

需要注意的是，这些流在加密前后都进行了 gzip 压缩（代码在底部）。

加密

    public static void AesEncrypt(byte[] keyBytes, byte[] ivBytes, Stream dataStream, FileStream outStream)
    {
        RijndaelManaged symmetricKey = new RijndaelManaged();
        symmetricKey.Mode = CipherMode.CBC;
        symmetricKey.Padding = PaddingMode.PKCS7;
        symmetricKey.BlockSize = 128;
        symmetricKey.KeySize = 256;

        const int chunkSize = 4096;//1024 * 1024 * 10;

        using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, ivBytes))
        {
            using (CryptoStream cryptoStream = new CryptoStream(outStream, encryptor, CryptoStreamMode.Write))
            {
                while (dataStream.Position != dataStream.Length)
                {
                    long remainingBytes = dataStream.Length - dataStream.Position;
                    var buffer = chunkSize > remainingBytes ? new byte[(int)remainingBytes] : new byte[chunkSize];

                    dataStream.Read(buffer, 0, buffer.Length);
                    cryptoStream.Write(buffer, 0, buffer.Length);
                    cryptoStream.Flush();
                }
                cryptoStream.FlushFinalBlock();
            }
        }
        symmetricKey.Clear();
    }

解密

    public static void AesDecrypt(byte[] keyBytes, byte[] ivBytes, Stream dataStream, FileStream outStream)
    {
        RijndaelManaged symmetricKey = new RijndaelManaged();
        symmetricKey.Mode = CipherMode.CBC;
        symmetricKey.Padding = PaddingMode.PKCS7;
        symmetricKey.BlockSize = 128;
        symmetricKey.KeySize = keyBytes.Length == 32 ? 256 : 128;

        const int chunkSize = 4096;

        using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, ivBytes))
        {
            using (CryptoStream cryptoStream = new CryptoStream(dataStream, decryptor, CryptoStreamMode.Read))
            {
                while (dataStream.Position != dataStream.Length)
                {
                    long remainingBytes = dataStream.Length - dataStream.Position;
                    var buffer = chunkSize > remainingBytes
                        ? new byte[(int) remainingBytes]
                        : new byte[chunkSize];

                    cryptoStream.Read(buffer, 0, buffer.Length);
                    outStream.Write(buffer, 0, buffer.Length);
                    outStream.Flush();
                }
                //cryptoStream.FlushFinalBlock(); // Was throwing an exception
            }
        }
        symmetricKey.Clear();
    }

压缩（加密前）

    public static void StreamCompress(Stream dataStream, FileStream outStream)
    {
        dataStream.Position = 0;
        outStream.Position = 0;

        const int chunkSize = 4096;
        using (GZipStream gzs = new GZipStream(outStream, CompressionMode.Compress))
        {
            while (dataStream.Position != dataStream.Length)
            {
                long remainingBytes = dataStream.Length - dataStream.Position;
                var buffer = chunkSize > remainingBytes ? new byte[(int)remainingBytes] : new byte[chunkSize];
                dataStream.Read(buffer, 0, buffer.Length);
                gzs.Write(buffer, 0, buffer.Length);
                gzs.Flush();
            }
        }
    }

解压（解密后）

    public static void StreamDecompress(Stream dataStream, FileStream outStream)
    {
        byte[] buffer = new byte[4096];
        dataStream.Position = 0;
        using (GZipStream gzs = new GZipStream(dataStream, CompressionMode.Decompress))
        {
            for (int r = -1; r != 0; r = gzs.Read(buffer, 0, buffer.Length))
                if (r > 0) outStream.Write(buffer, 0, r);
        }
}

我已经回答了一些其他问题，但无法弄清楚为什么这只发生在某些文件上。失败的文件大小为 46,854,144 字节。不过，这似乎适用于更大和更小的文件。

如有任何帮助，我们将不胜感激。

Answer 1

问题出在我解密数据的方式上。我错误地使用了 CryptoStream。如果有人感兴趣，更新后的解密函数如下。

    public static void AesDecrypt(byte[] keyBytes, byte[] ivBytes, Stream dataStream, FileStream outStream)
    {
        dataStream.Position = 0;
        outStream.Position = 0;

        RijndaelManaged symmetricKey = new RijndaelManaged();
        symmetricKey.Mode = CipherMode.CBC;
        symmetricKey.Padding = PaddingMode.PKCS7;
        symmetricKey.BlockSize = 128;
        symmetricKey.KeySize = keyBytes.Length == 32 ? 256 : 128;

        const int chunkSize = 4096;

        using (ICryptoTransform decryptor = symmetricKey.CreateDecryptor(keyBytes, ivBytes))
        {
            using (CryptoStream cryptoStream = new CryptoStream(outStream, decryptor, CryptoStreamMode.Write))
            {

                while (dataStream.Position != dataStream.Length)
                {
                    long remainingBytes = dataStream.Length - dataStream.Position;
                    var buffer = chunkSize > remainingBytes
                        ? new byte[(int) remainingBytes]
                        : new byte[chunkSize];

                    var bytesRead = dataStream.Read(buffer, 0, buffer.Length);
                    cryptoStream.Write(buffer, 0, bytesRead);   
                }
                cryptoStream.FlushFinalBlock();
            }
        }
        symmetricKey.Clear();
    }

c# RijndaelManaged 加密和解密有时会失败

c# RijndaelManaged encryption & decryption sometimes fails

c#

encryption

cryptography

padding

missing-data