C# 使用X509密钥进行文件加密

我对这个问题已经束手无策了。 背景：实现通过NetCore API中的数据流对所有文件进行加密的功能

该实现通过了我在NetFULL和NetCore下对其进行的所有测试。我抛出了数百种不同的文件类型，包括纯文本、Word、Excel、PDF，每个文件都进行加密和解密。然而，当从一个角度前端从API调用时，流程就会崩溃

调查发现，正是在加密过程中，文件最终被破坏，因为当我用另一个单元测试加密的文件替换上传的“加密”文件时，解密和下载工作完美无瑕

我用bouncy castle来完成真正的工作。下面是我用来加密和解密的方法。任何指导都会有帮助

        public virtual void EncryptFileStream(Stream stream, X509Certificate2 encryptingCertificate, Stream encryptedStream)
    {
        if (!encryptingCertificate.HasPrivateKey || encryptingCertificate.PrivateKey == null)
        {
            throw new ArgumentException(nameof(encryptingCertificate) + " Does not have a private key");
        }
        if (!IsFileEncrypted(stream))
        {
            var dataGenerator = new CmsEnvelopedDataStreamGenerator();
            dataGenerator.AddKeyTransRecipient(DotNetUtilities.FromX509Certificate(encryptingCertificate));
            var cryptoStream = dataGenerator.Open(encryptedStream, CmsEnvelopedGenerator.Aes128Cbc);
            using (var fs = new BinaryWriter(cryptoStream))
            {
                stream.CopyTo(fs.BaseStream);
            }
            cryptoStream.Close();
        }
    }


        public virtual void DecryptFileStream(Stream encryptedStream, X509Certificate2 encryptingCertificate, Stream decryptedStream)
    {
        if (!encryptingCertificate.HasPrivateKey || encryptingCertificate.PrivateKey == null)
        {
            throw new ArgumentException(nameof(encryptingCertificate) + " Does not have a private key");
        }

        if (IsFileEncrypted(encryptedStream))
        {
            CmsEnvelopedDataParser ep = new CmsEnvelopedDataParser(encryptedStream);
            RecipientInformationStore recipients = ep.GetRecipientInfos();

            var cert = DotNetUtilities.FromX509Certificate(encryptingCertificate);
            var keyPair = DotNetUtilities.GetKeyPair(encryptingCertificate.PrivateKey);
            RecipientID recSel = new RecipientID
            {
                Issuer = PrincipalUtilities.GetIssuerX509Principal(cert), SerialNumber = cert.SerialNumber
            };

            RecipientInformation recipient = recipients.GetFirstRecipient(recSel);
            CmsTypedStream recData = recipient.GetContentStream(keyPair.Private);
            recData.ContentStream.CopyTo(decryptedStream);
        }
    }

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问题是void IsFileEncrypted（）在检查后将流位置设置回0，但是上载文件在内容处置中的位置不是0，因此目标文件格式不正确。修复方法是固定蒸汽的起始位置，而不是将蒸汽重置回其原始位置

        public virtual bool IsFileEncrypted(Stream stream)
        {
            var currentStreamPosition = stream.Position;
            try
            {
                CmsEnvelopedDataParser ep = new CmsEnvelopedDataParser(stream);
                RecipientInformationStore recipients = ep.GetRecipientInfos();
                return recipients != null;
            }
            catch
            {
                return false;
            }
            finally
            {
                stream.Position = currentStreamPosition;
            }
        }

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和往常一样，一些说明问题的测试输入和输出将大有帮助。