在 c# 上生成 x509 证书未返回预期结果

Question

I am using .net 6.0 with .net core and I'd like to create x509 certificate and use this with k8s c# client.

For creating x509 certificate I have method like this:

public static byte[] GenerateCertificate(string name)
{
    var sanBuilder = new SubjectAlternativeNameBuilder();
    sanBuilder.AddIpAddress(IPAddress.Loopback);
    sanBuilder.AddIpAddress(IPAddress.IPv6Loopback);
    sanBuilder.AddDnsName("localhost");
    sanBuilder.AddDnsName(Environment.MachineName);

    var distinguishedName = new X500DistinguishedName(name);

    using var rsa = RSA.Create(4096);
    var request = new CertificateRequest(distinguishedName, rsa, HashAlgorithmName.SHA256,RSASignaturePadding.Pkcs1);

    request.CertificateExtensions.Add(new X509KeyUsageExtension(X509KeyUsageFlags.DataEncipherment | X509KeyUsageFlags.KeyEncipherment | X509KeyUsageFlags.DigitalSignature , false));
    request.CertificateExtensions.Add(new X509EnhancedKeyUsageExtension(new OidCollection { new ("1.3.6.1.5.5.7.3.1") }, false));
    request.CertificateExtensions.Add(sanBuilder.Build());
    request.CreateSelfSigned(new DateTimeOffset(DateTime.UtcNow.AddDays(-1)), new DateTimeOffset(DateTime.UtcNow.AddDays(3650)));
    var csr = request.CreateSigningRequest();
    return csr;
}

And I am expecting result like this for generating certificate on k8s:

-----BEGIN CERTIFICATE REQUEST-----
    certificate code long code
-----END CERTIFICATE REQUEST-----

How to manage to get result like this?

Answer 1

You are looking for the PEM format, but the function provides DER.

From the docs:

"To convert the return value to PEM format, make a string consisting of -----BEGIN CERTIFICATE REQUEST----- , a newline, the Base-64-encoded representation of the request (by convention, linewrapped at 64 characters), a newline, and -----END CERTIFICATE REQUEST----- ."

So what you need is

return
    "-----BEGIN CERTIFICATE REQUEST-----\r\n" +
    Convert.ToBase64String(csr) +
    "\r\n-----END CERTIFICATE REQUEST-----";

You also need to change your function to return string . If you want to return it as byte you need to decide an encoding. For example, you could do return Encoding.UTF8.GetBytes(base64Request);