C# 建立TCP连接时平台不支持异常

升级到Visual Studio 2019后，我发现我现有的Xamarin应用程序无法再建立TCP连接

            var pkcs12Store = new Pkcs12Store();
            var certEntry = new X509CertificateEntry(BouncyCert);

            pkcs12Store.SetCertificateEntry(BouncyCert.SerialNumber.ToString(), certEntry);
            pkcs12Store.SetKeyEntry(BouncyCert.SerialNumber.ToString(),
                new AsymmetricKeyEntry(KeyPair.Private), new[] { certEntry });

            X509Certificate2 keyedCert;

            using (MemoryStream pfxStream = new MemoryStream()) {
                pkcs12Store.Save(pfxStream, null, new SecureRandom());
                pfxStream.Seek(0, SeekOrigin.Begin);
                keyedCert = new X509Certificate2(pfxStream.ToArray(), "", X509KeyStorageFlags.Exportable);
            }

            return keyedCert;

经过一些研究，我发现VisualStudio2019附带了MSBuild 16，而VS2017附带了MSBuild 15

            var pkcs12Store = new Pkcs12Store();
            var certEntry = new X509CertificateEntry(BouncyCert);

            pkcs12Store.SetCertificateEntry(BouncyCert.SerialNumber.ToString(), certEntry);
            pkcs12Store.SetKeyEntry(BouncyCert.SerialNumber.ToString(),
                new AsymmetricKeyEntry(KeyPair.Private), new[] { certEntry });

            X509Certificate2 keyedCert;

            using (MemoryStream pfxStream = new MemoryStream()) {
                pkcs12Store.Save(pfxStream, null, new SecureRandom());
                pfxStream.Seek(0, SeekOrigin.Begin);
                keyedCert = new X509Certificate2(pfxStream.ToArray(), "", X509KeyStorageFlags.Exportable);
            }

            return keyedCert;

在为我的RSA系统加密生成证书和密钥对后使用这段代码之前：

var cert = new X509Certificate2(DotNetUtilities.ToX509Certificate(bcCert)) 
    { PrivateKey = DotNetUtilities.ToRSA((RsaPrivateCrtKeyParameters)keyPair.Private) };

            var pkcs12Store = new Pkcs12Store();
            var certEntry = new X509CertificateEntry(BouncyCert);

            pkcs12Store.SetCertificateEntry(BouncyCert.SerialNumber.ToString(), certEntry);
            pkcs12Store.SetKeyEntry(BouncyCert.SerialNumber.ToString(),
                new AsymmetricKeyEntry(KeyPair.Private), new[] { certEntry });

            X509Certificate2 keyedCert;

            using (MemoryStream pfxStream = new MemoryStream()) {
                pkcs12Store.Save(pfxStream, null, new SecureRandom());
                pfxStream.Seek(0, SeekOrigin.Begin);
                keyedCert = new X509Certificate2(pfxStream.ToArray(), "", X509KeyStorageFlags.Exportable);
            }

            return keyedCert;

使用Visual Studio 2019，您无法设置私钥。这可以在中的反编译X509Certificate2.cs中看到

C:\ProgramFiles（x86）\MicrosoftVisualStudio\2019\Professional\Common7\IDE\ReferenceAssembly\Microsoft\Framework\MonoAndroid\v1.0\System.dll

            var pkcs12Store = new Pkcs12Store();
            var certEntry = new X509CertificateEntry(BouncyCert);

            pkcs12Store.SetCertificateEntry(BouncyCert.SerialNumber.ToString(), certEntry);
            pkcs12Store.SetKeyEntry(BouncyCert.SerialNumber.ToString(),
                new AsymmetricKeyEntry(KeyPair.Private), new[] { certEntry });

            X509Certificate2 keyedCert;

            using (MemoryStream pfxStream = new MemoryStream()) {
                pkcs12Store.Save(pfxStream, null, new SecureRandom());
                pfxStream.Seek(0, SeekOrigin.Begin);
                keyedCert = new X509Certificate2(pfxStream.ToArray(), "", X509KeyStorageFlags.Exportable);
            }

            return keyedCert;

---

在此之后，我发现了一个

ConvertBouncyCert

方法，该方法将返回一个

X509Certificate2

包装器，该包装器将在生成的X509Certificate周围附加私钥，但我仍然收到一个

无法解码的
异常。
Jeremy的库包含用于转换X509Certificate的代码进入X509Certificate2：

            var pkcs12Store = new Pkcs12Store();
            var certEntry = new X509CertificateEntry(BouncyCert);

            pkcs12Store.SetCertificateEntry(BouncyCert.SerialNumber.ToString(), certEntry);
            pkcs12Store.SetKeyEntry(BouncyCert.SerialNumber.ToString(),
                new AsymmetricKeyEntry(KeyPair.Private), new[] { certEntry });

            X509Certificate2 keyedCert;

            using (MemoryStream pfxStream = new MemoryStream()) {
                pkcs12Store.Save(pfxStream, null, new SecureRandom());
                pfxStream.Seek(0, SeekOrigin.Begin);
                keyedCert = new X509Certificate2(pfxStream.ToArray(), "", X509KeyStorageFlags.Exportable);
            }

            return keyedCert;

您需要创建Pkcs12StoreBuilder对象并将DER编码设置为true

            var pkcs12Store = new Pkcs12Store();
            var certEntry = new X509CertificateEntry(BouncyCert);

            pkcs12Store.SetCertificateEntry(BouncyCert.SerialNumber.ToString(), certEntry);
            pkcs12Store.SetKeyEntry(BouncyCert.SerialNumber.ToString(),
                new AsymmetricKeyEntry(KeyPair.Private), new[] { certEntry });

            X509Certificate2 keyedCert;

            using (MemoryStream pfxStream = new MemoryStream()) {
                pkcs12Store.Save(pfxStream, null, new SecureRandom());
                pfxStream.Seek(0, SeekOrigin.Begin);
                keyedCert = new X509Certificate2(pfxStream.ToArray(), "", X509KeyStorageFlags.Exportable);
            }

            return keyedCert;

            var pkcs12StoreBuilder = new Pkcs12StoreBuilder();

            pkcs12StoreBuilder.SetUseDerEncoding(true);
            var pkcs12Store = pkcs12StoreBuilder.Build();

            var certificateEntry = new X509CertificateEntry(bouncyCert);

这在解释DER及其在密码学和RSA系统中的所有组件方面做得非常好

            var pkcs12Store = new Pkcs12Store();
            var certEntry = new X509CertificateEntry(BouncyCert);

            pkcs12Store.SetCertificateEntry(BouncyCert.SerialNumber.ToString(), certEntry);
            pkcs12Store.SetKeyEntry(BouncyCert.SerialNumber.ToString(),
                new AsymmetricKeyEntry(KeyPair.Private), new[] { certEntry });

            X509Certificate2 keyedCert;

            using (MemoryStream pfxStream = new MemoryStream()) {
                pkcs12Store.Save(pfxStream, null, new SecureRandom());
                pfxStream.Seek(0, SeekOrigin.Begin);
                keyedCert = new X509Certificate2(pfxStream.ToArray(), "", X509KeyStorageFlags.Exportable);
            }

            return keyedCert;