SmtpNegotiateAuthenticationModule.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / Net / System / Net / Mail / SmtpNegotiateAuthenticationModule.cs / 2 / SmtpNegotiateAuthenticationModule.cs
                        

                        
                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Net.Mail 
{ 
    using System;
    using System.Collections; 
    using System.IO;
    using System.Net;
    using System.Security.Permissions;
    using System.ComponentModel; 

 
    internal class SmtpNegotiateAuthenticationModule : ISmtpAuthenticationModule 
    {
        Hashtable sessions = new Hashtable(); 

        internal SmtpNegotiateAuthenticationModule()
        {
        } 

        #region ISmtpAuthenticationModule Members 
 
        // Security this method will access NetworkCredential properties that demand UnmanagedCode and Environment Permission
        [EnvironmentPermission(SecurityAction.Assert, Unrestricted=true)] 
        [SecurityPermission(SecurityAction.Assert, Flags=SecurityPermissionFlag.UnmanagedCode)]
        public Authorization Authenticate(string challenge, NetworkCredential credential, object sessionCookie)
        {
            if(Logging.On)Logging.Enter(Logging.Web, this, "Authenticate", null); 
            try {
                lock (this.sessions) 
                { 

                    NTAuthentication clientContext = this.sessions[sessionCookie] as NTAuthentication; 
                    if (clientContext == null)
                    {
                        if(credential == null){
                            return null; 
                        }
 
                        this.sessions[sessionCookie] = clientContext = new NTAuthentication(false,"Negotiate",credential,null,ContextFlags.Connection | ContextFlags.InitIntegrity); 
                    }
                    byte[] byteResp; 
                    string resp = null;

                    if (!clientContext.IsCompleted) {
 
                        // If auth is not yet completed keep producing
                        // challenge responses with GetOutgoingBlob 
 
                        SecurityStatus statusCode;
                        byte[] decodedChallenge = null; 
                        if (challenge != null) {
                            decodedChallenge =
                                Convert.FromBase64String(challenge);
                        } 
                        byteResp = clientContext.GetOutgoingBlob(
                                                    decodedChallenge, 
                                                    false, 
                                                    out statusCode);
                        // Note sure why this is here...keeping it. 
                        if (clientContext.IsCompleted && byteResp == null) {
                            resp = "\r\n";
                        }
                        if (byteResp != null) { 
                            resp = Convert.ToBase64String(byteResp);
                        } 
                    } else { 

                        // If auth completed and still have a challenge then 
                        // server may be doing "correct" form of GSSAPI SASL.
                        // Validate incoming and produce outgoing SASL security
                        // layer negotiate message.
 
                        resp = GetSecurityLayerOutgoingBlob(
                                    challenge, 
                                    clientContext); 
                    }
 
                    return new Authorization(resp, clientContext.IsCompleted);
                }
            }
            finally { 
                if(Logging.On)Logging.Exit(Logging.Web, this, "Authenticate", null);
            } 
        } 

        public string AuthenticationType 
        {
            get
            {
                return "gssapi"; 
            }
        } 
 
        public void CloseContext(object sessionCookie) {
            NTAuthentication clientContext = null; 
            lock (sessions) {
                clientContext = sessions[sessionCookie] as NTAuthentication;
                if (clientContext != null) {
                    sessions.Remove(sessionCookie); 
                }
            } 
            if (clientContext != null) { 
                clientContext.CloseContext();
            } 
        }

        #endregion
 
        // Function for SASL security layer negotiation after
        // authorization completes. 
        // 
        // Returns null for failure, Base64 encoded string on
        // success. 
        private string GetSecurityLayerOutgoingBlob(
                            string challenge,
                            NTAuthentication clientContext) {
 
            // must have a security layer challenge
 
            if (challenge == null) 
                return null;
 
            // "unwrap" challenge

            byte[] input = Convert.FromBase64String(challenge);
 
            int len;
 
            try { 
                len = clientContext.VerifySignature(input, 0, input.Length);
            } 
            catch (Win32Exception) {
                // any decrypt failure is an auth failure
                return null;
            } 

            // Per RFC 2222 Section 7.2.2: 
            //   the client should then expect the server to issue a 
            //   token in a subsequent challenge.  The client passes
            //   this token to GSS_Unwrap and interprets the first 
            //   octet of cleartext as a bit-mask specifying the
            //   security layers supported by the server and the
            //   second through fourth octets as the maximum size
            //   output_message to send to the server. 
            // Section 7.2.3
            //   The security layer and their corresponding bit-masks 
            //   are as follows: 
            //     1 No security layer
            //     2 Integrity protection 
            //       Sender calls GSS_Wrap with conf_flag set to FALSE
            //     4 Privacy protection
            //       Sender calls GSS_Wrap with conf_flag set to TRUE
            // 
            // Exchange 2007 and our client only support
            // "No security layer". Therefore verify first byte is value 1 
            // and the 2nd-4th bytes are value zero since token size is not 
            // applicable when there is no security layer.
 
            if (len < 4 ||          // expect 4 bytes
                input[0] != 1 ||    // first value 1
                input[1] != 0 ||    // rest value 0
                input[2] != 0 || 
                input[3] != 0) {
                return null; 
            } 

            // Continuing with RFC 2222 section 7.2.2: 
            //   The client then constructs data, with the first octet
            //   containing the bit-mask specifying the selected security
            //   layer, the second through fourth octets containing in
            //   network byte order the maximum size output_message the client 
            //   is able to receive, and the remaining octets containing the
            //   authorization identity. 
            // 
            // So now this contructs the "wrapped" response.  The response is
            // payload is identical to the received server payload and the 
            // "authorization identity" is not supplied as it is unnecessary.

            // let MakeSignature figure out length of output
            byte[] output = null; 
            try {
                len = clientContext.MakeSignature(input, 0, 4, ref output); 
            } 
            catch (Win32Exception) {
                // any decrypt failure is an auth failure 
                return null;
            }

            // return Base64 encoded string of signed payload 
            return Convert.ToBase64String(output, 0, len);
        } 
    } 
}

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