MQTTnet/Source/MQTTnet/Client/Options/MqttClientDefaultCertificateValidationHandler.cs

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

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

namespace MQTTnet.Client
{
    public sealed class MqttClientDefaultCertificateValidationHandler
    {
        public static bool Handle(MqttClientCertificateValidationEventArgs eventArgs)
        {
            var sslPolicyErrors = eventArgs.SslPolicyErrors;
            
            if (eventArgs.ClientOptions?.TlsOptions?.IgnoreCertificateChainErrors ?? false)
            {
                sslPolicyErrors &= ~SslPolicyErrors.RemoteCertificateChainErrors;
            }
            
            if (sslPolicyErrors == SslPolicyErrors.None)
            {
                return true;
            }
            
            if (eventArgs.Chain.ChainStatus.Any(c =>
                    c.Status == X509ChainStatusFlags.RevocationStatusUnknown || c.Status == X509ChainStatusFlags.Revoked || c.Status == X509ChainStatusFlags.OfflineRevocation))
            {
                if (eventArgs.ClientOptions?.TlsOptions?.IgnoreCertificateRevocationErrors != true)
                {
                    return false;
                }
            }

            if (eventArgs.Chain.ChainStatus.Any(c => c.Status == X509ChainStatusFlags.PartialChain))
            {
                if (eventArgs.ClientOptions?.TlsOptions?.IgnoreCertificateChainErrors != true)
                {
                    return false;
                }
            }

            return eventArgs.ClientOptions?.TlsOptions?.AllowUntrustedCertificates == true;
        }
    }
}