ICertificateProvider Interface

public interface ICertificateProvider

Provides a mechanism for accessing custom certificate providers.

Summary

The ICertificateProvider interface is designed to allow developers to integrate their own custom certificate management solutions within the .NET security framework. This is particularly useful in scenarios where standard certificate stores are not sufficient or when specific certificate retrieval or validation logic is required.

Members

Methods

GetCertificate

X509Certificate2 GetCertificate(string targetHost, X509CertificateCollection localCertificates, X509Certificate2 remoteCertificate, string[] acceptableIssuers, X509CertificateContextSelectionContext context);

Retrieves a certificate based on the provided criteria. This method allows for custom logic in selecting the appropriate client certificate for authentication.

Parameters:

targetHost: The target host for which the certificate is being requested.
localCertificates: A collection of locally available certificates that can be used for authentication.
remoteCertificate: The certificate provided by the remote party.
acceptableIssuers: An array of distinguished names of acceptable certificate issuers.
context: Additional context for certificate selection.

Returns:

An X509Certificate2 object representing the selected client certificate, or null if no suitable certificate is found.

Remarks

When using SSL/TLS connections, the client often needs to present a certificate to the server for authentication. The ICertificateProvider interface provides an extensibility point for customizing this process.

Implement this interface to create a custom certificate selection mechanism.
Register your custom provider with the security framework when establishing an SSL/TLS connection.
The GetCertificate method is the core of the provider, where you implement your logic to choose the best certificate from the available options.

Example

C# Example: Custom Certificate Provider


using System;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;

public class MyCustomCertificateProvider : ICertificateProvider
{
    public X509Certificate2 GetCertificate(
        string targetHost,
        X509CertificateCollection localCertificates,
        X509Certificate2 remoteCertificate,
        string[] acceptableIssuers,
        X509CertificateContextSelectionContext context)
    {
        Console.WriteLine($"Selecting certificate for host: {targetHost}");

        // Example logic: Prefer a certificate issued by a specific issuer
        if (acceptableIssuers != null)
        {
            foreach (var issuer in acceptableIssuers)
            {
                Console.WriteLine($"Acceptable issuer: {issuer}");
            }
        }

        // In a real scenario, you would search localCertificates based on criteria.
        // For simplicity, let's return the first available certificate if any.
        if (localCertificates != null && localCertificates.Count > 0)
        {
            Console.WriteLine($"Found {localCertificates.Count} local certificates. Returning the first one.");
            return (X509Certificate2)localCertificates[0];
        }

        Console.WriteLine("No suitable local certificate found.");
        return null;
    }
}

// How to use it (conceptual):
// SslClientAuthenticationOptions options = new SslClientAuthenticationOptions();
// options.ClientCertificateContext = new MyCustomCertificateProvider();
// SslStream sslStream = new SslStream(innerStream, false, ...);
// await sslStream.AuthenticateAsClientAsync(targetHost, options, cancellationToken);