SmtpNegotiateAuthenticationModule.cs

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using System.Collections.Generic;
using System.ComponentModel;
using System.Security.Authentication.ExtendedProtection;
 
namespace System.Net.Mail;
 
internal sealed class SmtpNegotiateAuthenticationModule : ISmtpAuthenticationModule
{
    private readonly Dictionary<object, System.Net.NTAuthentication> _sessions = new Dictionary<object, System.Net.NTAuthentication>();
 
    public string AuthenticationType => "gssapi";
 
    internal SmtpNegotiateAuthenticationModule()
    {
    }
 
    public Authorization Authenticate(string challenge, NetworkCredential credential, object sessionCookie, string spn, ChannelBinding channelBindingToken)
    {
        try
        {
            lock (_sessions)
            {
                if (!_sessions.TryGetValue(sessionCookie, out var value))
                {
                    if (credential == null)
                    {
                        return null;
                    }
                    value = (_sessions[sessionCookie] = new System.Net.NTAuthentication(isServer: false, "Negotiate", credential, spn, System.Net.ContextFlagsPal.Connection | System.Net.ContextFlagsPal.AcceptStream, channelBindingToken));
                }
                string token = null;
                if (!value.IsCompleted)
                {
                    byte[] incomingBlob = null;
                    if (challenge != null)
                    {
                        incomingBlob = Convert.FromBase64String(challenge);
                    }
                    byte[] outgoingBlob = value.GetOutgoingBlob(incomingBlob, thrownOnError: false);
                    if (value.IsCompleted && outgoingBlob == null)
                    {
                        token = "\r\n";
                    }
                    if (outgoingBlob != null)
                    {
                        token = Convert.ToBase64String(outgoingBlob);
                    }
                }
                else
                {
                    token = GetSecurityLayerOutgoingBlob(challenge, value);
                }
                return new Authorization(token, value.IsCompleted);
            }
        }
        catch (NullReferenceException)
        {
            return null;
        }
    }
 
    public void CloseContext(object sessionCookie)
    {
        System.Net.NTAuthentication value = null;
        lock (_sessions)
        {
            if (_sessions.TryGetValue(sessionCookie, out value))
            {
                _sessions.Remove(sessionCookie);
            }
        }
        value?.CloseContext();
    }
 
    private string GetSecurityLayerOutgoingBlob(string challenge, System.Net.NTAuthentication clientContext)
    {
        if (challenge == null)
        {
            return null;
        }
        byte[] array = Convert.FromBase64String(challenge);
        int num;
        try
        {
            num = clientContext.VerifySignature(array, 0, array.Length);
        }
        catch (Win32Exception)
        {
            return null;
        }
        if (num < 4 || array[0] != 1 || array[1] != 0 || array[2] != 0 || array[3] != 0)
        {
            return null;
        }
        byte[] output = null;
        try
        {
            num = clientContext.MakeSignature(array, 0, 4, ref output);
        }
        catch (Win32Exception)
        {
            return null;
        }
        return Convert.ToBase64String(output, 0, num);
    }
}