c# - 能否返回 CryptoStream 并仍然正确处理所有内容？

Question

如果我有一个 CryptoStream 我想传回给用户，天真的方法是

public Stream GetDecryptedFileStream(string inputFile, byte[] key, byte[] iv)
{
    var fsCrypt = new FileStream(inputFile, FileMode.Open, FileAccess.Read, FileShare.Read);
    var rmCrypto = new RijndaelManaged();
    var transform = rmCrypto.CreateDecryptor(key, iv);
    var cs = new CryptoStream(fsCrypt, transform, CryptoStreamMode.Read);

    return cs;
}

我知道当我处理 CryptoStream 时，底层的 FileStream will also be disposed .我遇到的问题是如何处理 rmCrypto 和 transform？ RijndaelManaged 和 ICryptoTransform 是一次性类，但处理流不会处理这两个对象。

处理这种情况的正确方法是什么？

Answer 1

Ian 在基本概念 (go upvote him) 上先于我，但 CryptoStream 本身不是密封的，因此创建一个派生类来包装需要处理的东西是微不足道的。

/// <summary>
/// Creates a class that creates a <see cref="CryptoStream"/> and wraps the disposing action of all the associated objects 
/// </summary>
class ReturnableCryptoStream : CryptoStream
{
    private readonly ICryptoTransform _transform;
    private readonly IDisposable _algorithm;

    public ReturnableCryptoStream(Stream stream, ICryptoTransform transform, CryptoStreamMode mode) 
        : this(stream, transform, mode, null)
    {
    }

    public ReturnableCryptoStream(Stream stream, ICryptoTransform transform, CryptoStreamMode mode, IDisposable algorithm) 
        : base(stream, transform, mode)
    {
        _transform = transform;
        _algorithm = algorithm;
    }

    protected override void Dispose(bool disposing)
    {
        base.Dispose(disposing);
        if (disposing)
        {
            if (_transform != null)
                _transform.Dispose();

            if (_algorithm != null)
                _algorithm.Dispose();
        }
    }
}

像这样使用

public Stream GetDecryptedFileStream(string inputFile, byte[] key, byte[] iv)
{
    var fsCrypt = new FileStream(inputFile, FileMode.Open, FileAccess.Read, FileShare.Read);
    var rmCrypto = new RijndaelManaged();
    var transform = rmCrypto.CreateDecryptor(key, iv);
    var cs = new ReturnableCryptoStream(fsCrypt, transform, CryptoStreamMode.Read, rmCrypto);

    return cs;
}