Loading PEM SSL certificates in Kestrel (Windows work-around)

loading-pem-ssl-windows-workaround.cs

// See https://github.com/dotnet/runtime/issues/23749

public static class CertHelper
{
    // To generate a self-signed cert:
    // dotnet dev-certs https -ep $pwd/selfsigned.pem --format Pem -np
    public static X509Certificate2 GetCertificate()
    {
        X509Certificate2 sslCert = CreateFromPublicPrivateKey("certs/selfsigned.pem", "certs/selfsigned.key");
        
        // work around for Windows (WinApi) problems with PEMS, still in .NET 5
        return new X509Certificate2(sslCert.Export(X509ContentType.Pkcs12));
    }
    
    public static X509Certificate2 CreateFromPublicPrivateKey(string publicCert="certs/public.pem", string privateCert="certs/private.pem")
    {
        byte[] publicPemBytes = File.ReadAllBytes(publicCert);
        using var publicX509 = new X509Certificate2(publicPemBytes);
        var privateKeyText = File.ReadAllText(privateCert);
        var privateKeyBlocks = privateKeyText.Split("-", StringSplitOptions.RemoveEmptyEntries);
        var privateKeyBytes = Convert.FromBase64String(privateKeyBlocks[1]);

        using RSA rsa = RSA.Create();
        if (privateKeyBlocks[0] == "BEGIN PRIVATE KEY")
        {
            rsa.ImportPkcs8PrivateKey(privateKeyBytes, out _);
        }
        else if (privateKeyBlocks[0] == "BEGIN RSA PRIVATE KEY")
        {
            rsa.ImportRSAPrivateKey(privateKeyBytes, out _);
        }
        X509Certificate2 keyPair = publicX509.CopyWithPrivateKey(rsa);
        return keyPair;
    }
}

// Your program.cs
public static IHostBuilder CreateHostBuilder(string[] args)
{
    return Host.CreateDefaultBuilder(args)
        .UseSerilog()
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.ConfigureKestrel(options =>
            {
                options.ConfigureHttpsDefaults(adapterOptions =>
                {
                    adapterOptions.ServerCertificate = CertHelper.GetCertificate();
                });
            });

            webBuilder.UseStartup<Startup>();
        });
}