smtpconnection.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ Net / Net / 3.5.50727.3053 / DEVDIV / depot / DevDiv / releases / whidbey / netfxsp / ndp / fx / src / Net / System / Net / Mail / smtpconnection.cs / 5 / smtpconnection.cs

                            namespace System.Net.Mail 
{
    using System;
    using System.Net;
    using System.Security.Cryptography.X509Certificates; 
    using System.IO;
    using System.Threading; 
    using System.Globalization; 
    using System.Security.Principal;
    using System.Security.Permissions; 



    class SmtpConnection 
    {
 
        private static PooledStream CreateSmtpPooledStream(ConnectionPool pool) { 
            return (PooledStream) new SmtpPooledStream(pool, TimeSpan.MaxValue, false);
        } 


        private static readonly CreateConnectionDelegate m_CreateConnectionCallback = new CreateConnectionDelegate(CreateSmtpPooledStream);
        private static readonly ContextCallback s_AuthenticateCallback = new ContextCallback(AuthenticateCallback); 

        BufferBuilder bufferBuilder = new BufferBuilder(); 
        bool isConnected; 
        bool isClosed;
        bool isStreamOpen; 
        bool sawNegotiate;
        EventHandler onCloseHandler;
        internal SmtpTransport parent;
        internal SmtpClient client; 
        SmtpReplyReaderFactory responseReader;
 
        PooledStream pooledStream; 
        ConnectionPool connectionPool;
        SupportedAuth supportedAuth = SupportedAuth.None; 
        bool serverSupportsStartTls = false;
        ISmtpAuthenticationModule[] authenticationModules;
        ICredentialsByHost credentials;
        int timeout = 100000; 
        string[] extensions;
 
        bool    enableSsl; 
        X509CertificateCollection clientCertificates;
 
        internal SmtpConnection(SmtpTransport parent, SmtpClient client, ICredentialsByHost credentials, ISmtpAuthenticationModule[] authenticationModules)
        {
            this.client = client;
            this.credentials = credentials; 
            this.authenticationModules = authenticationModules;
            this.parent = parent; 
            onCloseHandler = new EventHandler(OnClose); 
        }
 
        internal BufferBuilder BufferBuilder
        {
            get
            { 
                return bufferBuilder;
            } 
        } 

        internal bool IsConnected 
        {
            get
            {
                return isConnected; 
            }
        } 
 
        internal bool IsStreamOpen
        { 
            get
            {
                return isStreamOpen;
            } 
        }
 
        internal bool DSNEnabled 
        {
            get 
            {
                if (pooledStream != null)
                    return ((SmtpPooledStream)pooledStream).dsnEnabled;
                else 
                    return false;
            } 
        } 

        internal SmtpReplyReaderFactory Reader 
        {
            get
            {
                return responseReader; 
            }
        } 
 
        internal bool EnableSsl
        { 
            get
            {
                return enableSsl;
            } 
            set
            { 
#if !FEATURE_PAL 
                enableSsl = value;
#else 
                throw new NotImplementedException("ROTORTODO");
#endif
            }
        } 

        internal int Timeout 
        { 
            get
            { 
                return timeout;
            }
            set
            { 
                timeout = value;
            } 
        } 

 
        internal X509CertificateCollection ClientCertificates
        {
            get
            { 
                return clientCertificates;
            } 
            set 
            {
                clientCertificates = value; 
            }
        }

 
        internal IAsyncResult BeginGetConnection(string host, int port, ContextAwareResult outerResult, AsyncCallback callback, object state)
        { 
            ServicePoint servicePoint = ServicePointManager.FindServicePoint(host,port); 
            if(Logging.On)Logging.Associate(Logging.Web, this, servicePoint);
 
            if (EnableSsl && ClientCertificates != null && ClientCertificates.Count > 0)
                connectionPool = ConnectionPoolManager.GetConnectionPool(servicePoint, ClientCertificates.GetHashCode().ToString(NumberFormatInfo.InvariantInfo), m_CreateConnectionCallback);
            else
                connectionPool = ConnectionPoolManager.GetConnectionPool(servicePoint, "", m_CreateConnectionCallback); 

            ConnectAndHandshakeAsyncResult result = new ConnectAndHandshakeAsyncResult(this, host, port, outerResult, callback, state); 
            result.GetConnection(false); 
            return result;
        } 


        internal IAsyncResult BeginFlush(AsyncCallback callback, object state)
        { 
            return pooledStream.UnsafeBeginWrite(bufferBuilder.GetBuffer(), 0, bufferBuilder.Length, callback, state);
        } 
 
        internal void EndFlush(IAsyncResult result)
        { 
            pooledStream.EndWrite(result);
            bufferBuilder.Reset();
        }
 
        internal void Flush()
        { 
            pooledStream.Write(bufferBuilder.GetBuffer(), 0, bufferBuilder.Length); 
            bufferBuilder.Reset();
        } 

        internal void ReleaseConnection()
        {
            if (!isClosed) { 
                lock (this) {
                    if (!isClosed && pooledStream != null){ 
                        GlobalLog.Print("SmtpConnectiont#" + ValidationHelper.HashString(this) + "::Close Transport#"+ValidationHelper.HashString(parent)+"putting back pooledStream#"+ValidationHelper.HashString(pooledStream)); 
                        ((SmtpPooledStream)pooledStream).previouslyUsed = true;
                        connectionPool.PutConnection(pooledStream, pooledStream.Owner, Timeout); 
                    }
                    isClosed = true;
                }
            } 
            isConnected = false;
        } 
 
        internal void Abort()
        { 
            if (!isClosed) {
                lock (this) {
                    if (!isClosed && pooledStream != null){
                        GlobalLog.Print("SmtpConnectiont#" + ValidationHelper.HashString(this) + "::Close Transport#"+ValidationHelper.HashString(parent)+"closing and putting back pooledStream#"+ValidationHelper.HashString(pooledStream)); 
                        pooledStream.Close(0);
                        connectionPool.PutConnection(pooledStream, pooledStream.Owner, Timeout); 
                    } 
                    isClosed = true;
                } 
            }
            isConnected = false;
        }
 
        internal void ParseExtensions(string[] extensions) {
            supportedAuth = SupportedAuth.None; 
            foreach (string extension in extensions) { 
                if (String.Compare(extension, 0, "auth ", 0, 5, StringComparison.OrdinalIgnoreCase) == 0) {
                    string[] authTypes = extension.Split(' '); 
                    foreach (string authType in authTypes){
                        if (String.Compare(authType, "login", StringComparison.OrdinalIgnoreCase) == 0) {
                            supportedAuth |= SupportedAuth.Login;
                        } 
#if !FEATURE_PAL
                        else if (String.Compare(authType, "ntlm", StringComparison.OrdinalIgnoreCase) == 0) { 
                            supportedAuth|=SupportedAuth.NTLM; 
                        }
                        else if (String.Compare(authType, "gssapi", StringComparison.OrdinalIgnoreCase) == 0) { 
                            supportedAuth |= SupportedAuth.GGSAPI;
                        }
                        else if (String.Compare(authType, "wdigest", StringComparison.OrdinalIgnoreCase) == 0) {
                            supportedAuth |= SupportedAuth.WDigest; 
                        }
#endif // FEATURE_PAL 
                    } 
                }
                else if (String.Compare(extension, 0, "dsn ", 0, 3, StringComparison.OrdinalIgnoreCase) == 0) { 
                    ((SmtpPooledStream)pooledStream).dsnEnabled = true;
                }
                else if (String.Compare(extension, 0, "STARTTLS", 0, 8, StringComparison.OrdinalIgnoreCase) == 0) {
                    serverSupportsStartTls = true; 
                }
            } 
        } 

        internal bool AuthSupported(ISmtpAuthenticationModule module){ 
            if (module is SmtpLoginAuthenticationModule) {
                if ((supportedAuth & SupportedAuth.Login) > 0) {
                    return true;
                } 
            }
#if !FEATURE_PAL 
            else if (module is SmtpNegotiateAuthenticationModule) { 
                if ((supportedAuth & SupportedAuth.GGSAPI) > 0) {
                    sawNegotiate = true; 
                    return true;
                }
            }
            else if (module is SmtpNtlmAuthenticationModule) { 
                //don't try ntlm if negotiate has been tried
                if ((!sawNegotiate && (supportedAuth & SupportedAuth.NTLM) > 0)) { 
                    return true; 
                }
            } 
            else if (module is SmtpDigestAuthenticationModule) {
                if ((supportedAuth & SupportedAuth.WDigest) > 0) {
                    return true;
                } 
            }
#endif // FEATURE_PAL 
 
            return false;
        } 


        internal void GetConnection(string host, int port)
        { 
            if (isConnected)
            { 
                throw new InvalidOperationException(SR.GetString(SR.SmtpAlreadyConnected)); 
            }
 
            ServicePoint servicePoint = ServicePointManager.FindServicePoint(host,port);
            if(Logging.On)Logging.Associate(Logging.Web, this, servicePoint);
            connectionPool = ConnectionPoolManager.GetConnectionPool(servicePoint, "", m_CreateConnectionCallback);
 
            PooledStream pooledStream =  connectionPool.GetConnection((object)this, null, Timeout);
 
            while (((SmtpPooledStream)pooledStream).creds != null && ((SmtpPooledStream)pooledStream).creds != credentials) { 
                pooledStream.Close();
                connectionPool.PutConnection(pooledStream, pooledStream.Owner, Timeout); 
                pooledStream =  connectionPool.GetConnection((object)this, null, Timeout);
            }
            if(Logging.On)Logging.Associate(Logging.Web, this, pooledStream);
 
            lock(this){
                this.pooledStream = pooledStream; 
            } 

            ((SmtpPooledStream)pooledStream).creds = credentials; 

            responseReader = new SmtpReplyReaderFactory(pooledStream.NetworkStream);

            //set connectionlease 
            pooledStream.UpdateLifetime();
 
            //if the stream was already used, then we've already done the handshake 
            if (((SmtpPooledStream)pooledStream).previouslyUsed == true){
                isConnected = true; 
                return;
            }

            LineInfo info = responseReader.GetNextReplyReader().ReadLine(); 

            switch (info.StatusCode) 
            { 
                case SmtpStatusCode.ServiceReady:
                { 
                    break;
                }
                default:
                { 
                    throw new SmtpException(info.StatusCode, info.Line, true);
                } 
            } 

            try 
            {
                extensions = EHelloCommand.Send(this, client.localHostName);
                ParseExtensions(extensions);
            } 
            catch (SmtpException e)
            { 
                if ((e.StatusCode != SmtpStatusCode.CommandUnrecognized) 
                    && (e.StatusCode != SmtpStatusCode.CommandNotImplemented)){
                    throw e; 
                }

                HelloCommand.Send(this, client.localHostName);
                //if ehello isn't supported, assume basic login 
                supportedAuth = SupportedAuth.Login;
            } 
 
#if !FEATURE_PAL
            // Establish TLS 
            if (enableSsl)
            {
                if (!serverSupportsStartTls)
                { 
                    // Either TLS is already established or server does not support TLS
                    if (!(pooledStream.NetworkStream is TlsStream)) 
                    { 
                        throw new SmtpException(SR.GetString(SR.MailServerDoesNotSupportStartTls));
                    } 
                }
                StartTlsCommand.Send(this);
                TlsStream TlsStream = new TlsStream(servicePoint.Host, pooledStream.NetworkStream, clientCertificates, servicePoint, client, null);
                pooledStream.NetworkStream= TlsStream; 
                responseReader = new SmtpReplyReaderFactory(pooledStream.NetworkStream);
 
                // According to RFC 3207: The client SHOULD send an EHLO command 
                // as the first command after a successful TLS negotiation.
                extensions = EHelloCommand.Send(this, client.localHostName); 
                ParseExtensions(extensions);
            }
#endif // !FEATURE_PAL
 
            //if no credentials were supplied, try anonymous
            //servers don't appear to anounce that they support anonymous login. 
            if (credentials != null) { 

                for (int i = 0; i < authenticationModules.Length; i++) 
                {

                    //only authenticate if the auth protocol is supported  - [....]
                    if (!AuthSupported(authenticationModules[i])) { 
                        continue;
                    } 
 
                    NetworkCredential credential = credentials.GetCredential(host, port, authenticationModules[i].AuthenticationType);
                    if (credential == null) 
                        continue;

                    Authorization auth = SetContextAndTryAuthenticate(authenticationModules[i], credential, null);
 
                    if (auth != null && auth.Message != null)
                    { 
                        info = AuthCommand.Send(this, authenticationModules[i].AuthenticationType, auth.Message); 

                        if (info.StatusCode == SmtpStatusCode.CommandParameterNotImplemented) 
                        {
                            continue;
                        }
 
                        while ((int)info.StatusCode == 334)
                        { 
                            auth = authenticationModules[i].Authenticate(info.Line, null, this); 
                            if (auth == null)
                            { 
                                throw new SmtpException(SR.GetString(SR.SmtpAuthenticationFailed));
                            }
                            info = AuthCommand.Send(this, auth.Message);
 
                            if ((int)info.StatusCode == 235)
                            { 
                                authenticationModules[i].CloseContext(this); 
                                isConnected = true;
                                return; 
                            }
                        }
                    }
                } 
            }
            isConnected = true; 
        } 
        //
        // We may need to impersonate in this method 
        //
        [SecurityPermission(SecurityAction.Assert, Flags=SecurityPermissionFlag.ControlPrincipal)]
        private Authorization SetContextAndTryAuthenticate(ISmtpAuthenticationModule module, NetworkCredential credential, ContextAwareResult context)
        { 
#if !FEATURE_PAL
            // We may need to restore user thread token here 
            if (credential is SystemNetworkCredential && ComNetOS.IsWinNt) 
            {
                // 
#if DEBUG
                GlobalLog.Assert(context == null || context.IdentityRequested, "SmtpConnection#{0}::SetContextAndTryAuthenticate|Authentication required when it wasn't expected.  (Maybe Credentials was changed on another thread?)", ValidationHelper.HashString(this));
#endif
 
                WindowsIdentity w = context == null ? null : context.Identity;
                try 
                { 
                    IDisposable ctx = w == null ? null : w.Impersonate();
                    if (ctx != null) 
                    {
                        using (ctx)
                        {
                            return module.Authenticate(null, credential, this); 
                        }
                    } 
                    else 
                    {
                        ExecutionContext x = context == null ? null : context.ContextCopy; 
                        if (x != null)
                        {
                            ExecutionContext.Run(x, s_AuthenticateCallback, new AuthenticateCallbackContext(this, module, credential));
                        } 
                        else
                        { 
                            return module.Authenticate(null, credential, this); 
                        }
                    } 
                }
                catch
                {
                    // Prevent the impersonation from leaking to upstack exception filters. 
                    throw;
                } 
            } 
#endif // !FEATURE_PAL
            return module.Authenticate(null, credential, this); 
        }

        private static void AuthenticateCallback(object state)
        { 
            AuthenticateCallbackContext context = (AuthenticateCallbackContext) state;
            context.module.Authenticate(null, context.credential, context.thisPtr); 
        } 

        private class AuthenticateCallbackContext 
        {
            internal AuthenticateCallbackContext(SmtpConnection thisPtr, ISmtpAuthenticationModule module, NetworkCredential credential)
            {
                this.thisPtr = thisPtr; 
                this.module = module;
                this.credential = credential; 
            } 

            internal readonly SmtpConnection thisPtr; 
            internal readonly ISmtpAuthenticationModule module;
            internal readonly NetworkCredential credential;
        }
 
        internal void EndGetConnection(IAsyncResult result)
        { 
            ConnectAndHandshakeAsyncResult.End(result); 
        }
 
        internal Stream GetClosableStream()
        {
            ClosableStream cs = new ClosableStream(pooledStream.NetworkStream, onCloseHandler);
            isStreamOpen = true; 
            return cs;
        } 
 
        void OnClose(object sender, EventArgs args)
        { 
            isStreamOpen = false;

            DataStopCommand.Send(this);
        } 

        class ConnectAndHandshakeAsyncResult : LazyAsyncResult 
        { 

            private static readonly GeneralAsyncDelegate m_ConnectionCreatedCallback = new GeneralAsyncDelegate(ConnectionCreatedCallback); 
            string authResponse;
            SmtpConnection connection;
            int currentModule = -1;
            int port; 
            static AsyncCallback handshakeCallback = new AsyncCallback(HandshakeCallback);
            static AsyncCallback sendEHelloCallback = new AsyncCallback(SendEHelloCallback); 
            static AsyncCallback sendHelloCallback = new AsyncCallback(SendHelloCallback); 
            static AsyncCallback authenticateCallback = new AsyncCallback(AuthenticateCallback);
            static AsyncCallback authenticateContinueCallback = new AsyncCallback(AuthenticateContinueCallback); 
            string host;

            private readonly ContextAwareResult m_OuterResult;
 

            internal ConnectAndHandshakeAsyncResult(SmtpConnection connection, string host, int port, ContextAwareResult outerResult, AsyncCallback callback, object state) : 
                base(null, state, callback) 
            {
                this.connection = connection; 
                this.host = host;
                this.port = port;

                m_OuterResult = outerResult; 
            }
 
 
            private static void ConnectionCreatedCallback(object request, object state) {
                GlobalLog.Enter("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::ConnectionCreatedCallback"); 
                ConnectAndHandshakeAsyncResult ConnectAndHandshakeAsyncResult = (ConnectAndHandshakeAsyncResult) request;
                if (state is Exception) {
                    ConnectAndHandshakeAsyncResult.InvokeCallback((Exception)state);
                    return; 
                }
                SmtpPooledStream pooledStream = (SmtpPooledStream)(PooledStream)state; 
 

                try 
                {
                    while (pooledStream.creds != null && pooledStream.creds != ConnectAndHandshakeAsyncResult.connection.credentials) {
                        GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::Connect pooledStream has wrong creds "+ValidationHelper.HashString(pooledStream));
                        pooledStream.Close(); 
                        ConnectAndHandshakeAsyncResult.connection.connectionPool.PutConnection(pooledStream, pooledStream.Owner, ConnectAndHandshakeAsyncResult.connection.Timeout);
                        pooledStream =  (SmtpPooledStream)ConnectAndHandshakeAsyncResult.connection.connectionPool.GetConnection((object)ConnectAndHandshakeAsyncResult,ConnectAndHandshakeAsyncResult.m_ConnectionCreatedCallback, ConnectAndHandshakeAsyncResult.connection.Timeout); 
                        if (pooledStream == null) { 
                            GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::Connect returning asynchronously");
                            return; 
                        }
                    }
                    if(Logging.On)Logging.Associate(Logging.Web, ConnectAndHandshakeAsyncResult.connection, pooledStream);
                    pooledStream.Owner = ConnectAndHandshakeAsyncResult.connection; //needs to be updated for gc reasons 
                    pooledStream.creds = ConnectAndHandshakeAsyncResult.connection.credentials;
 
 
                    lock(ConnectAndHandshakeAsyncResult.connection){
 
                        //if we were cancelled while getting the connection, we should close and return
                        if(ConnectAndHandshakeAsyncResult.connection.isClosed){
                            pooledStream.Close();
                            ConnectAndHandshakeAsyncResult.connection.connectionPool.PutConnection(pooledStream, pooledStream.Owner, ConnectAndHandshakeAsyncResult.connection.Timeout); 
                            GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::ConnectionCreatedCallback Connect was aborted "+ValidationHelper.HashString(pooledStream));
                            ConnectAndHandshakeAsyncResult.InvokeCallback(null); 
                            return; 
                        }
                        ConnectAndHandshakeAsyncResult.connection.pooledStream = pooledStream; 
                    }

                    ConnectAndHandshakeAsyncResult.Handshake();
                } 
                catch (Exception e)
                { 
                    ConnectAndHandshakeAsyncResult.InvokeCallback(e); 
                }
                GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::ConnectionCreatedCallback pooledStream#"+ValidationHelper.HashString(pooledStream)); 
            }


            internal static void End(IAsyncResult result) 
            {
                ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result; 
                object connectResult = thisPtr.InternalWaitForCompletion(); 
                if(connectResult is Exception){
                    throw (Exception)connectResult; 
                }
            }

            internal void GetConnection(bool synchronous) 
            {
 
                GlobalLog.Enter("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect: [....]=" + (synchronous?"true":"false")); 
                if (connection.isConnected)
                { 
                    throw new InvalidOperationException(SR.GetString(SR.SmtpAlreadyConnected));
                }

 
                SmtpPooledStream pooledStream =  (SmtpPooledStream)connection.connectionPool.GetConnection((object)this, (synchronous?null:m_ConnectionCreatedCallback), connection.Timeout);
                GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect returned" + ValidationHelper.HashString(this)); 
 
                if (pooledStream != null) {
                    try 
                    {
                        while (pooledStream.creds != null && pooledStream.creds != connection.credentials) {
                            GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect pooledStream has wrong creds "+ValidationHelper.HashString(pooledStream));
                            pooledStream.Close(); 
                            connection.connectionPool.PutConnection(pooledStream, pooledStream.Owner, connection.Timeout);
                            pooledStream =  (SmtpPooledStream)connection.connectionPool.GetConnection((object)this,(synchronous?null:m_ConnectionCreatedCallback), connection.Timeout); 
                            if (pooledStream == null) { 
                                GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect returning asynchronously");
                                return; 
                            }
                        }
                        pooledStream.creds = connection.credentials;
                        pooledStream.Owner = this.connection; //needs to be updated for gc reasons 

                        lock(connection){ 
                            connection.pooledStream = pooledStream; 
                        }
                        Handshake(); 
                    }
                    catch (Exception e)
                    {
                        InvokeCallback(e); 
                    }
                } 
                GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect pooledStream#"+ValidationHelper.HashString(pooledStream)); 
            }
 

            void Handshake()
            {
                connection.responseReader = new SmtpReplyReaderFactory(connection.pooledStream.NetworkStream); 

 
                 //if we've already used this stream, then we've already done the handshake 

                //set connectionlease 
                connection.pooledStream.UpdateLifetime();

                if(((SmtpPooledStream)connection.pooledStream).previouslyUsed == true){
                    connection.isConnected = true; 
                    InvokeCallback();
                    return; 
                } 

 
                SmtpReplyReader reader = connection.Reader.GetNextReplyReader();
                IAsyncResult result = reader.BeginReadLine(handshakeCallback, this);
                if (!result.CompletedSynchronously)
                { 
                    return;
                } 
 
                LineInfo info = reader.EndReadLine(result);
 
                if (info.StatusCode != SmtpStatusCode.ServiceReady)
                {
                    throw new SmtpException(info.StatusCode, info.Line, true);
                } 
                try
                { 
                    if (!SendEHello()) 
                    {
                        return; 
                    }
                }
                catch
                { 
                    if (!SendHello())
                    { 
                        return; 
                    }
                } 
            }

            static void HandshakeCallback(IAsyncResult result)   //3
            { 
                if (!result.CompletedSynchronously)
                { 
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState; 
                    try
                    { 
                        try
                        {
                            LineInfo info = thisPtr.connection.Reader.CurrentReader.EndReadLine(result);
                            if (info.StatusCode != SmtpStatusCode.ServiceReady) 
                            {
                                thisPtr.InvokeCallback(new SmtpException(info.StatusCode,info.Line,true)); 
                                return; 
                            }
                            if (!thisPtr.SendEHello()) 
                            {
                                return;
                            }
                        } 
                        catch (SmtpException)
                        { 
                            if (!thisPtr.SendHello()) 
                            {
                                return; 
                            }
                        }
                    }
                    catch (Exception e) 
                    {
                        thisPtr.InvokeCallback(e); 
                    } 
                }
            } 

            bool SendEHello()//4
            {
                IAsyncResult result = EHelloCommand.BeginSend(connection, connection.client.localHostName, sendEHelloCallback, this); 
                if (result.CompletedSynchronously)
                { 
                    connection.extensions = EHelloCommand.EndSend(result); 
                    connection.ParseExtensions(connection.extensions);
                    // If we already have a TlsStream, this is the second EHLO cmd 
                    // that we sent after TLS handshake compelted. So skip TLS and
                    // continue with Authenticate.
                    if (connection.pooledStream.NetworkStream is TlsStream)
                    { 
                        Authenticate();
                        return true; 
                    } 

                    if (connection.EnableSsl) { 
#if !FEATURE_PAL
                        if (!connection.serverSupportsStartTls)
                        {
                            // Either TLS is already established or server does not support TLS 
                            if (!(connection.pooledStream.NetworkStream is TlsStream))
                            { 
                                throw new SmtpException(SR.GetString(SR.MailServerDoesNotSupportStartTls)); 
                            }
                        } 

                        SendStartTls();
#else // FEATURE_PAL
                        throw new NotSupportedException("ROTORTODO"); 
#endif // !FEATURE_PAL
                    } 
                    else { 
                        Authenticate();
                    } 
                    return true;
                }
                return false;
            } 

            static void SendEHelloCallback(IAsyncResult result)//5 
            { 
                if (!result.CompletedSynchronously)
                { 
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try
                    {
                        try 
                        {
                            thisPtr.connection.extensions = EHelloCommand.EndSend(result); 
                            thisPtr.connection.ParseExtensions(thisPtr.connection.extensions); 

                            // If we already have a TlsStream, this is the second EHLO cmd 
                            // that we sent after TLS handshake compelted. So skip TLS and
                            // continue with Authenticate.
                            if (thisPtr.connection.pooledStream.NetworkStream is TlsStream)
                            { 
                                thisPtr.Authenticate();
                                return; 
                            } 
                        }
 
                        catch (SmtpException e)
                        {
                            if ((e.StatusCode != SmtpStatusCode.CommandUnrecognized)
                                && (e.StatusCode != SmtpStatusCode.CommandNotImplemented)){ 
                                throw e;
                            } 
 
                            if (!thisPtr.SendHello()) {
                                return; 
                            }
                        }

 
                        if (thisPtr.connection.EnableSsl) {
#if !FEATURE_PAL 
                            if (!thisPtr.connection.serverSupportsStartTls) 
                            {
                                // Either TLS is already established or server does not support TLS 
                                if (!(thisPtr.connection.pooledStream.NetworkStream is TlsStream))
                                {
                                    throw new SmtpException(SR.GetString(SR.MailServerDoesNotSupportStartTls));
                                } 
                            }
 
                            thisPtr.SendStartTls(); 
#else // FEATURE_PAL
                            throw new NotSupportedException("ROTORTODO"); 
#endif // !FEATURE_PAL
                        }
                        else {
                            thisPtr.Authenticate(); 
                        }
                    } 
                    catch (Exception e) 
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                }
            }
 
            bool SendHello()//6
            { 
                IAsyncResult result = HelloCommand.BeginSend(connection, connection.client.localHostName, sendHelloCallback, this); 
                //if ehello isn't supported, assume basic auth
                if (result.CompletedSynchronously) 
                {
                    connection.supportedAuth = SupportedAuth.Login;
                    HelloCommand.EndSend(result);
                    Authenticate(); 
                    return true;
                } 
                return false; 
            }
 
            static void SendHelloCallback(IAsyncResult result)     //7
            {
                if (!result.CompletedSynchronously)
                { 
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try 
                    { 
                        HelloCommand.EndSend(result);
                        thisPtr.Authenticate(); 
                    }
                    catch (Exception e)
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            } 

#if !FEATURE_PAL 
            bool SendStartTls()//6
            {
                IAsyncResult result = StartTlsCommand.BeginSend(connection, SendStartTlsCallback, this);
                if (result.CompletedSynchronously) 
                {
                    StartTlsCommand.EndSend(result); 
                    TlsStream TlsStream = new TlsStream(connection.pooledStream.ServicePoint.Host, connection.pooledStream.NetworkStream, connection.ClientCertificates, connection.pooledStream.ServicePoint, connection.client, m_OuterResult.ContextCopy); 
                    connection.pooledStream.NetworkStream= TlsStream;
                    connection.responseReader = new SmtpReplyReaderFactory(connection.pooledStream.NetworkStream); 
                    SendEHello();
                    return true;
                }
                return false; 
            }
 
            static void SendStartTlsCallback(IAsyncResult result)     //7 
            {
                if (!result.CompletedSynchronously) 
                {
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try
                    { 
                        StartTlsCommand.EndSend(result);
                        TlsStream TlsStream = new TlsStream(thisPtr.connection.pooledStream.ServicePoint.Host, thisPtr.connection.pooledStream.NetworkStream, thisPtr.connection.ClientCertificates, thisPtr.connection.pooledStream.ServicePoint, thisPtr.connection.client, thisPtr.m_OuterResult.ContextCopy); 
                        thisPtr.connection.pooledStream.NetworkStream= TlsStream; 
                        thisPtr.connection.responseReader = new SmtpReplyReaderFactory(thisPtr.connection.pooledStream.NetworkStream);
                        thisPtr.SendEHello(); 
                    }
                    catch (Exception e)
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            } 
#endif // !FEATURE_PAL
 
            void Authenticate() //8
            {
                //if no credentials were supplied, try anonymous
                //servers don't appear to anounce that they support anonymous login. 
                if (connection.credentials != null) {
                    while (++currentModule < connection.authenticationModules.Length) 
                    { 
                        //only authenticate if the auth protocol is supported
                        ISmtpAuthenticationModule module = connection.authenticationModules[currentModule]; 
                        if (!connection.AuthSupported(module)) {
                            continue;
                        }
 
                        NetworkCredential credential = connection.credentials.GetCredential(host, port, module.AuthenticationType);
                        if (credential ==null) 
                            continue; 
                        Authorization auth = connection.SetContextAndTryAuthenticate(module, credential, m_OuterResult);
 
                        if (auth != null && auth.Message != null)
                        {
                            IAsyncResult result = AuthCommand.BeginSend(connection, connection.authenticationModules[currentModule].AuthenticationType, auth.Message, authenticateCallback, this);
                            if (!result.CompletedSynchronously) 
                            {
                                return; 
                            } 

                            LineInfo info = AuthCommand.EndSend(result); 

                            if ((int)info.StatusCode == 334)
                            {
                                authResponse = info.Line; 
                                if (!AuthenticateContinue())
                                { 
                                    return; 
                                }
                            } 
                            else if ((int)info.StatusCode == 235)
                            {
                                module.CloseContext(connection);
                                connection.isConnected = true; 
                                break;
                            } 
                        } 
                    }
 
                    //try anonymous if didn't authenticate
                    //if (!connection.isConnected) {
                    //    throw new SmtpException(SR.GetString(SR.SmtpAuthenticationFailed));
                   // } 
                }
 
                connection.isConnected = true; 
                InvokeCallback();
            } 

            static void AuthenticateCallback(IAsyncResult result) //9
            {
                if (!result.CompletedSynchronously) 
                {
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState; 
                    try 
                    {
                        LineInfo info = AuthCommand.EndSend(result); 

                        if ((int)info.StatusCode == 334)
                        {
                            thisPtr.authResponse = info.Line; 
                            if (!thisPtr.AuthenticateContinue())
                            { 
                                return; 
                            }
                        } 
                        else if ((int)info.StatusCode == 235)
                        {
                            thisPtr.connection.authenticationModules[thisPtr.currentModule].CloseContext(thisPtr.connection);
                            thisPtr.connection.isConnected = true; 
                            thisPtr.InvokeCallback();
                            return; 
                        } 

                        thisPtr.Authenticate(); 
                    }
                    catch (Exception e)
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            } 

            bool AuthenticateContinue()        //10 
            {
                for (;;)
                {
                    // We don't need credential on the continued auth assuming they were captured on the first call. 
                    // That should always work, otherwise what if a new credential has been returned?
                    Authorization auth = connection.authenticationModules[currentModule].Authenticate(authResponse, null, connection); 
                    if (auth == null) 
                    {
                        throw new SmtpException(SR.GetString(SR.SmtpAuthenticationFailed)); 
                    }

                    IAsyncResult result = AuthCommand.BeginSend(connection, auth.Message, authenticateContinueCallback, this);
                    if (!result.CompletedSynchronously) 
                    {
                        return false; 
                    } 

                    LineInfo info = AuthCommand.EndSend(result); 
                    if ((int)info.StatusCode == 235)
                    {
                        connection.authenticationModules[currentModule].CloseContext(connection);
                        connection.isConnected = true; 
                        InvokeCallback();
                        return false; 
                    } 
                    else if ((int)info.StatusCode != 334)
                    { 
                        return true;
                    }
                    authResponse = info.Line;
                } 
            }
 
            static void AuthenticateContinueCallback(IAsyncResult result)     //11 
            {
                if (!result.CompletedSynchronously) 
                {
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try
                    { 
                        LineInfo info = AuthCommand.EndSend(result);
                        if ((int)info.StatusCode == 235) 
                        { 
                            thisPtr.connection.authenticationModules[thisPtr.currentModule].CloseContext(thisPtr.connection);
                            thisPtr.connection.isConnected = true; 
                            thisPtr.InvokeCallback();
                            return;
                        }
                        else if ((int)info.StatusCode == 334) 
                        {
                            thisPtr.authResponse = info.Line; 
                            if (!thisPtr.AuthenticateContinue()) 
                            {
                                return; 
                            }
                        }
                        thisPtr.Authenticate();
                    } 
                    catch (Exception e)
                    { 
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            }

        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
namespace System.Net.Mail 
{
    using System;
    using System.Net;
    using System.Security.Cryptography.X509Certificates; 
    using System.IO;
    using System.Threading; 
    using System.Globalization; 
    using System.Security.Principal;
    using System.Security.Permissions; 



    class SmtpConnection 
    {
 
        private static PooledStream CreateSmtpPooledStream(ConnectionPool pool) { 
            return (PooledStream) new SmtpPooledStream(pool, TimeSpan.MaxValue, false);
        } 


        private static readonly CreateConnectionDelegate m_CreateConnectionCallback = new CreateConnectionDelegate(CreateSmtpPooledStream);
        private static readonly ContextCallback s_AuthenticateCallback = new ContextCallback(AuthenticateCallback); 

        BufferBuilder bufferBuilder = new BufferBuilder(); 
        bool isConnected; 
        bool isClosed;
        bool isStreamOpen; 
        bool sawNegotiate;
        EventHandler onCloseHandler;
        internal SmtpTransport parent;
        internal SmtpClient client; 
        SmtpReplyReaderFactory responseReader;
 
        PooledStream pooledStream; 
        ConnectionPool connectionPool;
        SupportedAuth supportedAuth = SupportedAuth.None; 
        bool serverSupportsStartTls = false;
        ISmtpAuthenticationModule[] authenticationModules;
        ICredentialsByHost credentials;
        int timeout = 100000; 
        string[] extensions;
 
        bool    enableSsl; 
        X509CertificateCollection clientCertificates;
 
        internal SmtpConnection(SmtpTransport parent, SmtpClient client, ICredentialsByHost credentials, ISmtpAuthenticationModule[] authenticationModules)
        {
            this.client = client;
            this.credentials = credentials; 
            this.authenticationModules = authenticationModules;
            this.parent = parent; 
            onCloseHandler = new EventHandler(OnClose); 
        }
 
        internal BufferBuilder BufferBuilder
        {
            get
            { 
                return bufferBuilder;
            } 
        } 

        internal bool IsConnected 
        {
            get
            {
                return isConnected; 
            }
        } 
 
        internal bool IsStreamOpen
        { 
            get
            {
                return isStreamOpen;
            } 
        }
 
        internal bool DSNEnabled 
        {
            get 
            {
                if (pooledStream != null)
                    return ((SmtpPooledStream)pooledStream).dsnEnabled;
                else 
                    return false;
            } 
        } 

        internal SmtpReplyReaderFactory Reader 
        {
            get
            {
                return responseReader; 
            }
        } 
 
        internal bool EnableSsl
        { 
            get
            {
                return enableSsl;
            } 
            set
            { 
#if !FEATURE_PAL 
                enableSsl = value;
#else 
                throw new NotImplementedException("ROTORTODO");
#endif
            }
        } 

        internal int Timeout 
        { 
            get
            { 
                return timeout;
            }
            set
            { 
                timeout = value;
            } 
        } 

 
        internal X509CertificateCollection ClientCertificates
        {
            get
            { 
                return clientCertificates;
            } 
            set 
            {
                clientCertificates = value; 
            }
        }

 
        internal IAsyncResult BeginGetConnection(string host, int port, ContextAwareResult outerResult, AsyncCallback callback, object state)
        { 
            ServicePoint servicePoint = ServicePointManager.FindServicePoint(host,port); 
            if(Logging.On)Logging.Associate(Logging.Web, this, servicePoint);
 
            if (EnableSsl && ClientCertificates != null && ClientCertificates.Count > 0)
                connectionPool = ConnectionPoolManager.GetConnectionPool(servicePoint, ClientCertificates.GetHashCode().ToString(NumberFormatInfo.InvariantInfo), m_CreateConnectionCallback);
            else
                connectionPool = ConnectionPoolManager.GetConnectionPool(servicePoint, "", m_CreateConnectionCallback); 

            ConnectAndHandshakeAsyncResult result = new ConnectAndHandshakeAsyncResult(this, host, port, outerResult, callback, state); 
            result.GetConnection(false); 
            return result;
        } 


        internal IAsyncResult BeginFlush(AsyncCallback callback, object state)
        { 
            return pooledStream.UnsafeBeginWrite(bufferBuilder.GetBuffer(), 0, bufferBuilder.Length, callback, state);
        } 
 
        internal void EndFlush(IAsyncResult result)
        { 
            pooledStream.EndWrite(result);
            bufferBuilder.Reset();
        }
 
        internal void Flush()
        { 
            pooledStream.Write(bufferBuilder.GetBuffer(), 0, bufferBuilder.Length); 
            bufferBuilder.Reset();
        } 

        internal void ReleaseConnection()
        {
            if (!isClosed) { 
                lock (this) {
                    if (!isClosed && pooledStream != null){ 
                        GlobalLog.Print("SmtpConnectiont#" + ValidationHelper.HashString(this) + "::Close Transport#"+ValidationHelper.HashString(parent)+"putting back pooledStream#"+ValidationHelper.HashString(pooledStream)); 
                        ((SmtpPooledStream)pooledStream).previouslyUsed = true;
                        connectionPool.PutConnection(pooledStream, pooledStream.Owner, Timeout); 
                    }
                    isClosed = true;
                }
            } 
            isConnected = false;
        } 
 
        internal void Abort()
        { 
            if (!isClosed) {
                lock (this) {
                    if (!isClosed && pooledStream != null){
                        GlobalLog.Print("SmtpConnectiont#" + ValidationHelper.HashString(this) + "::Close Transport#"+ValidationHelper.HashString(parent)+"closing and putting back pooledStream#"+ValidationHelper.HashString(pooledStream)); 
                        pooledStream.Close(0);
                        connectionPool.PutConnection(pooledStream, pooledStream.Owner, Timeout); 
                    } 
                    isClosed = true;
                } 
            }
            isConnected = false;
        }
 
        internal void ParseExtensions(string[] extensions) {
            supportedAuth = SupportedAuth.None; 
            foreach (string extension in extensions) { 
                if (String.Compare(extension, 0, "auth ", 0, 5, StringComparison.OrdinalIgnoreCase) == 0) {
                    string[] authTypes = extension.Split(' '); 
                    foreach (string authType in authTypes){
                        if (String.Compare(authType, "login", StringComparison.OrdinalIgnoreCase) == 0) {
                            supportedAuth |= SupportedAuth.Login;
                        } 
#if !FEATURE_PAL
                        else if (String.Compare(authType, "ntlm", StringComparison.OrdinalIgnoreCase) == 0) { 
                            supportedAuth|=SupportedAuth.NTLM; 
                        }
                        else if (String.Compare(authType, "gssapi", StringComparison.OrdinalIgnoreCase) == 0) { 
                            supportedAuth |= SupportedAuth.GGSAPI;
                        }
                        else if (String.Compare(authType, "wdigest", StringComparison.OrdinalIgnoreCase) == 0) {
                            supportedAuth |= SupportedAuth.WDigest; 
                        }
#endif // FEATURE_PAL 
                    } 
                }
                else if (String.Compare(extension, 0, "dsn ", 0, 3, StringComparison.OrdinalIgnoreCase) == 0) { 
                    ((SmtpPooledStream)pooledStream).dsnEnabled = true;
                }
                else if (String.Compare(extension, 0, "STARTTLS", 0, 8, StringComparison.OrdinalIgnoreCase) == 0) {
                    serverSupportsStartTls = true; 
                }
            } 
        } 

        internal bool AuthSupported(ISmtpAuthenticationModule module){ 
            if (module is SmtpLoginAuthenticationModule) {
                if ((supportedAuth & SupportedAuth.Login) > 0) {
                    return true;
                } 
            }
#if !FEATURE_PAL 
            else if (module is SmtpNegotiateAuthenticationModule) { 
                if ((supportedAuth & SupportedAuth.GGSAPI) > 0) {
                    sawNegotiate = true; 
                    return true;
                }
            }
            else if (module is SmtpNtlmAuthenticationModule) { 
                //don't try ntlm if negotiate has been tried
                if ((!sawNegotiate && (supportedAuth & SupportedAuth.NTLM) > 0)) { 
                    return true; 
                }
            } 
            else if (module is SmtpDigestAuthenticationModule) {
                if ((supportedAuth & SupportedAuth.WDigest) > 0) {
                    return true;
                } 
            }
#endif // FEATURE_PAL 
 
            return false;
        } 


        internal void GetConnection(string host, int port)
        { 
            if (isConnected)
            { 
                throw new InvalidOperationException(SR.GetString(SR.SmtpAlreadyConnected)); 
            }
 
            ServicePoint servicePoint = ServicePointManager.FindServicePoint(host,port);
            if(Logging.On)Logging.Associate(Logging.Web, this, servicePoint);
            connectionPool = ConnectionPoolManager.GetConnectionPool(servicePoint, "", m_CreateConnectionCallback);
 
            PooledStream pooledStream =  connectionPool.GetConnection((object)this, null, Timeout);
 
            while (((SmtpPooledStream)pooledStream).creds != null && ((SmtpPooledStream)pooledStream).creds != credentials) { 
                pooledStream.Close();
                connectionPool.PutConnection(pooledStream, pooledStream.Owner, Timeout); 
                pooledStream =  connectionPool.GetConnection((object)this, null, Timeout);
            }
            if(Logging.On)Logging.Associate(Logging.Web, this, pooledStream);
 
            lock(this){
                this.pooledStream = pooledStream; 
            } 

            ((SmtpPooledStream)pooledStream).creds = credentials; 

            responseReader = new SmtpReplyReaderFactory(pooledStream.NetworkStream);

            //set connectionlease 
            pooledStream.UpdateLifetime();
 
            //if the stream was already used, then we've already done the handshake 
            if (((SmtpPooledStream)pooledStream).previouslyUsed == true){
                isConnected = true; 
                return;
            }

            LineInfo info = responseReader.GetNextReplyReader().ReadLine(); 

            switch (info.StatusCode) 
            { 
                case SmtpStatusCode.ServiceReady:
                { 
                    break;
                }
                default:
                { 
                    throw new SmtpException(info.StatusCode, info.Line, true);
                } 
            } 

            try 
            {
                extensions = EHelloCommand.Send(this, client.localHostName);
                ParseExtensions(extensions);
            } 
            catch (SmtpException e)
            { 
                if ((e.StatusCode != SmtpStatusCode.CommandUnrecognized) 
                    && (e.StatusCode != SmtpStatusCode.CommandNotImplemented)){
                    throw e; 
                }

                HelloCommand.Send(this, client.localHostName);
                //if ehello isn't supported, assume basic login 
                supportedAuth = SupportedAuth.Login;
            } 
 
#if !FEATURE_PAL
            // Establish TLS 
            if (enableSsl)
            {
                if (!serverSupportsStartTls)
                { 
                    // Either TLS is already established or server does not support TLS
                    if (!(pooledStream.NetworkStream is TlsStream)) 
                    { 
                        throw new SmtpException(SR.GetString(SR.MailServerDoesNotSupportStartTls));
                    } 
                }
                StartTlsCommand.Send(this);
                TlsStream TlsStream = new TlsStream(servicePoint.Host, pooledStream.NetworkStream, clientCertificates, servicePoint, client, null);
                pooledStream.NetworkStream= TlsStream; 
                responseReader = new SmtpReplyReaderFactory(pooledStream.NetworkStream);
 
                // According to RFC 3207: The client SHOULD send an EHLO command 
                // as the first command after a successful TLS negotiation.
                extensions = EHelloCommand.Send(this, client.localHostName); 
                ParseExtensions(extensions);
            }
#endif // !FEATURE_PAL
 
            //if no credentials were supplied, try anonymous
            //servers don't appear to anounce that they support anonymous login. 
            if (credentials != null) { 

                for (int i = 0; i < authenticationModules.Length; i++) 
                {

                    //only authenticate if the auth protocol is supported  - [....]
                    if (!AuthSupported(authenticationModules[i])) { 
                        continue;
                    } 
 
                    NetworkCredential credential = credentials.GetCredential(host, port, authenticationModules[i].AuthenticationType);
                    if (credential == null) 
                        continue;

                    Authorization auth = SetContextAndTryAuthenticate(authenticationModules[i], credential, null);
 
                    if (auth != null && auth.Message != null)
                    { 
                        info = AuthCommand.Send(this, authenticationModules[i].AuthenticationType, auth.Message); 

                        if (info.StatusCode == SmtpStatusCode.CommandParameterNotImplemented) 
                        {
                            continue;
                        }
 
                        while ((int)info.StatusCode == 334)
                        { 
                            auth = authenticationModules[i].Authenticate(info.Line, null, this); 
                            if (auth == null)
                            { 
                                throw new SmtpException(SR.GetString(SR.SmtpAuthenticationFailed));
                            }
                            info = AuthCommand.Send(this, auth.Message);
 
                            if ((int)info.StatusCode == 235)
                            { 
                                authenticationModules[i].CloseContext(this); 
                                isConnected = true;
                                return; 
                            }
                        }
                    }
                } 
            }
            isConnected = true; 
        } 
        //
        // We may need to impersonate in this method 
        //
        [SecurityPermission(SecurityAction.Assert, Flags=SecurityPermissionFlag.ControlPrincipal)]
        private Authorization SetContextAndTryAuthenticate(ISmtpAuthenticationModule module, NetworkCredential credential, ContextAwareResult context)
        { 
#if !FEATURE_PAL
            // We may need to restore user thread token here 
            if (credential is SystemNetworkCredential && ComNetOS.IsWinNt) 
            {
                // 
#if DEBUG
                GlobalLog.Assert(context == null || context.IdentityRequested, "SmtpConnection#{0}::SetContextAndTryAuthenticate|Authentication required when it wasn't expected.  (Maybe Credentials was changed on another thread?)", ValidationHelper.HashString(this));
#endif
 
                WindowsIdentity w = context == null ? null : context.Identity;
                try 
                { 
                    IDisposable ctx = w == null ? null : w.Impersonate();
                    if (ctx != null) 
                    {
                        using (ctx)
                        {
                            return module.Authenticate(null, credential, this); 
                        }
                    } 
                    else 
                    {
                        ExecutionContext x = context == null ? null : context.ContextCopy; 
                        if (x != null)
                        {
                            ExecutionContext.Run(x, s_AuthenticateCallback, new AuthenticateCallbackContext(this, module, credential));
                        } 
                        else
                        { 
                            return module.Authenticate(null, credential, this); 
                        }
                    } 
                }
                catch
                {
                    // Prevent the impersonation from leaking to upstack exception filters. 
                    throw;
                } 
            } 
#endif // !FEATURE_PAL
            return module.Authenticate(null, credential, this); 
        }

        private static void AuthenticateCallback(object state)
        { 
            AuthenticateCallbackContext context = (AuthenticateCallbackContext) state;
            context.module.Authenticate(null, context.credential, context.thisPtr); 
        } 

        private class AuthenticateCallbackContext 
        {
            internal AuthenticateCallbackContext(SmtpConnection thisPtr, ISmtpAuthenticationModule module, NetworkCredential credential)
            {
                this.thisPtr = thisPtr; 
                this.module = module;
                this.credential = credential; 
            } 

            internal readonly SmtpConnection thisPtr; 
            internal readonly ISmtpAuthenticationModule module;
            internal readonly NetworkCredential credential;
        }
 
        internal void EndGetConnection(IAsyncResult result)
        { 
            ConnectAndHandshakeAsyncResult.End(result); 
        }
 
        internal Stream GetClosableStream()
        {
            ClosableStream cs = new ClosableStream(pooledStream.NetworkStream, onCloseHandler);
            isStreamOpen = true; 
            return cs;
        } 
 
        void OnClose(object sender, EventArgs args)
        { 
            isStreamOpen = false;

            DataStopCommand.Send(this);
        } 

        class ConnectAndHandshakeAsyncResult : LazyAsyncResult 
        { 

            private static readonly GeneralAsyncDelegate m_ConnectionCreatedCallback = new GeneralAsyncDelegate(ConnectionCreatedCallback); 
            string authResponse;
            SmtpConnection connection;
            int currentModule = -1;
            int port; 
            static AsyncCallback handshakeCallback = new AsyncCallback(HandshakeCallback);
            static AsyncCallback sendEHelloCallback = new AsyncCallback(SendEHelloCallback); 
            static AsyncCallback sendHelloCallback = new AsyncCallback(SendHelloCallback); 
            static AsyncCallback authenticateCallback = new AsyncCallback(AuthenticateCallback);
            static AsyncCallback authenticateContinueCallback = new AsyncCallback(AuthenticateContinueCallback); 
            string host;

            private readonly ContextAwareResult m_OuterResult;
 

            internal ConnectAndHandshakeAsyncResult(SmtpConnection connection, string host, int port, ContextAwareResult outerResult, AsyncCallback callback, object state) : 
                base(null, state, callback) 
            {
                this.connection = connection; 
                this.host = host;
                this.port = port;

                m_OuterResult = outerResult; 
            }
 
 
            private static void ConnectionCreatedCallback(object request, object state) {
                GlobalLog.Enter("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::ConnectionCreatedCallback"); 
                ConnectAndHandshakeAsyncResult ConnectAndHandshakeAsyncResult = (ConnectAndHandshakeAsyncResult) request;
                if (state is Exception) {
                    ConnectAndHandshakeAsyncResult.InvokeCallback((Exception)state);
                    return; 
                }
                SmtpPooledStream pooledStream = (SmtpPooledStream)(PooledStream)state; 
 

                try 
                {
                    while (pooledStream.creds != null && pooledStream.creds != ConnectAndHandshakeAsyncResult.connection.credentials) {
                        GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::Connect pooledStream has wrong creds "+ValidationHelper.HashString(pooledStream));
                        pooledStream.Close(); 
                        ConnectAndHandshakeAsyncResult.connection.connectionPool.PutConnection(pooledStream, pooledStream.Owner, ConnectAndHandshakeAsyncResult.connection.Timeout);
                        pooledStream =  (SmtpPooledStream)ConnectAndHandshakeAsyncResult.connection.connectionPool.GetConnection((object)ConnectAndHandshakeAsyncResult,ConnectAndHandshakeAsyncResult.m_ConnectionCreatedCallback, ConnectAndHandshakeAsyncResult.connection.Timeout); 
                        if (pooledStream == null) { 
                            GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::Connect returning asynchronously");
                            return; 
                        }
                    }
                    if(Logging.On)Logging.Associate(Logging.Web, ConnectAndHandshakeAsyncResult.connection, pooledStream);
                    pooledStream.Owner = ConnectAndHandshakeAsyncResult.connection; //needs to be updated for gc reasons 
                    pooledStream.creds = ConnectAndHandshakeAsyncResult.connection.credentials;
 
 
                    lock(ConnectAndHandshakeAsyncResult.connection){
 
                        //if we were cancelled while getting the connection, we should close and return
                        if(ConnectAndHandshakeAsyncResult.connection.isClosed){
                            pooledStream.Close();
                            ConnectAndHandshakeAsyncResult.connection.connectionPool.PutConnection(pooledStream, pooledStream.Owner, ConnectAndHandshakeAsyncResult.connection.Timeout); 
                            GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::ConnectionCreatedCallback Connect was aborted "+ValidationHelper.HashString(pooledStream));
                            ConnectAndHandshakeAsyncResult.InvokeCallback(null); 
                            return; 
                        }
                        ConnectAndHandshakeAsyncResult.connection.pooledStream = pooledStream; 
                    }

                    ConnectAndHandshakeAsyncResult.Handshake();
                } 
                catch (Exception e)
                { 
                    ConnectAndHandshakeAsyncResult.InvokeCallback(e); 
                }
                GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(request) + "::ConnectionCreatedCallback pooledStream#"+ValidationHelper.HashString(pooledStream)); 
            }


            internal static void End(IAsyncResult result) 
            {
                ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result; 
                object connectResult = thisPtr.InternalWaitForCompletion(); 
                if(connectResult is Exception){
                    throw (Exception)connectResult; 
                }
            }

            internal void GetConnection(bool synchronous) 
            {
 
                GlobalLog.Enter("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect: [....]=" + (synchronous?"true":"false")); 
                if (connection.isConnected)
                { 
                    throw new InvalidOperationException(SR.GetString(SR.SmtpAlreadyConnected));
                }

 
                SmtpPooledStream pooledStream =  (SmtpPooledStream)connection.connectionPool.GetConnection((object)this, (synchronous?null:m_ConnectionCreatedCallback), connection.Timeout);
                GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect returned" + ValidationHelper.HashString(this)); 
 
                if (pooledStream != null) {
                    try 
                    {
                        while (pooledStream.creds != null && pooledStream.creds != connection.credentials) {
                            GlobalLog.Print("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect pooledStream has wrong creds "+ValidationHelper.HashString(pooledStream));
                            pooledStream.Close(); 
                            connection.connectionPool.PutConnection(pooledStream, pooledStream.Owner, connection.Timeout);
                            pooledStream =  (SmtpPooledStream)connection.connectionPool.GetConnection((object)this,(synchronous?null:m_ConnectionCreatedCallback), connection.Timeout); 
                            if (pooledStream == null) { 
                                GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect returning asynchronously");
                                return; 
                            }
                        }
                        pooledStream.creds = connection.credentials;
                        pooledStream.Owner = this.connection; //needs to be updated for gc reasons 

                        lock(connection){ 
                            connection.pooledStream = pooledStream; 
                        }
                        Handshake(); 
                    }
                    catch (Exception e)
                    {
                        InvokeCallback(e); 
                    }
                } 
                GlobalLog.Leave("ConnectAndHandshakeAsyncResult#" + ValidationHelper.HashString(this) + "::Connect pooledStream#"+ValidationHelper.HashString(pooledStream)); 
            }
 

            void Handshake()
            {
                connection.responseReader = new SmtpReplyReaderFactory(connection.pooledStream.NetworkStream); 

 
                 //if we've already used this stream, then we've already done the handshake 

                //set connectionlease 
                connection.pooledStream.UpdateLifetime();

                if(((SmtpPooledStream)connection.pooledStream).previouslyUsed == true){
                    connection.isConnected = true; 
                    InvokeCallback();
                    return; 
                } 

 
                SmtpReplyReader reader = connection.Reader.GetNextReplyReader();
                IAsyncResult result = reader.BeginReadLine(handshakeCallback, this);
                if (!result.CompletedSynchronously)
                { 
                    return;
                } 
 
                LineInfo info = reader.EndReadLine(result);
 
                if (info.StatusCode != SmtpStatusCode.ServiceReady)
                {
                    throw new SmtpException(info.StatusCode, info.Line, true);
                } 
                try
                { 
                    if (!SendEHello()) 
                    {
                        return; 
                    }
                }
                catch
                { 
                    if (!SendHello())
                    { 
                        return; 
                    }
                } 
            }

            static void HandshakeCallback(IAsyncResult result)   //3
            { 
                if (!result.CompletedSynchronously)
                { 
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState; 
                    try
                    { 
                        try
                        {
                            LineInfo info = thisPtr.connection.Reader.CurrentReader.EndReadLine(result);
                            if (info.StatusCode != SmtpStatusCode.ServiceReady) 
                            {
                                thisPtr.InvokeCallback(new SmtpException(info.StatusCode,info.Line,true)); 
                                return; 
                            }
                            if (!thisPtr.SendEHello()) 
                            {
                                return;
                            }
                        } 
                        catch (SmtpException)
                        { 
                            if (!thisPtr.SendHello()) 
                            {
                                return; 
                            }
                        }
                    }
                    catch (Exception e) 
                    {
                        thisPtr.InvokeCallback(e); 
                    } 
                }
            } 

            bool SendEHello()//4
            {
                IAsyncResult result = EHelloCommand.BeginSend(connection, connection.client.localHostName, sendEHelloCallback, this); 
                if (result.CompletedSynchronously)
                { 
                    connection.extensions = EHelloCommand.EndSend(result); 
                    connection.ParseExtensions(connection.extensions);
                    // If we already have a TlsStream, this is the second EHLO cmd 
                    // that we sent after TLS handshake compelted. So skip TLS and
                    // continue with Authenticate.
                    if (connection.pooledStream.NetworkStream is TlsStream)
                    { 
                        Authenticate();
                        return true; 
                    } 

                    if (connection.EnableSsl) { 
#if !FEATURE_PAL
                        if (!connection.serverSupportsStartTls)
                        {
                            // Either TLS is already established or server does not support TLS 
                            if (!(connection.pooledStream.NetworkStream is TlsStream))
                            { 
                                throw new SmtpException(SR.GetString(SR.MailServerDoesNotSupportStartTls)); 
                            }
                        } 

                        SendStartTls();
#else // FEATURE_PAL
                        throw new NotSupportedException("ROTORTODO"); 
#endif // !FEATURE_PAL
                    } 
                    else { 
                        Authenticate();
                    } 
                    return true;
                }
                return false;
            } 

            static void SendEHelloCallback(IAsyncResult result)//5 
            { 
                if (!result.CompletedSynchronously)
                { 
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try
                    {
                        try 
                        {
                            thisPtr.connection.extensions = EHelloCommand.EndSend(result); 
                            thisPtr.connection.ParseExtensions(thisPtr.connection.extensions); 

                            // If we already have a TlsStream, this is the second EHLO cmd 
                            // that we sent after TLS handshake compelted. So skip TLS and
                            // continue with Authenticate.
                            if (thisPtr.connection.pooledStream.NetworkStream is TlsStream)
                            { 
                                thisPtr.Authenticate();
                                return; 
                            } 
                        }
 
                        catch (SmtpException e)
                        {
                            if ((e.StatusCode != SmtpStatusCode.CommandUnrecognized)
                                && (e.StatusCode != SmtpStatusCode.CommandNotImplemented)){ 
                                throw e;
                            } 
 
                            if (!thisPtr.SendHello()) {
                                return; 
                            }
                        }

 
                        if (thisPtr.connection.EnableSsl) {
#if !FEATURE_PAL 
                            if (!thisPtr.connection.serverSupportsStartTls) 
                            {
                                // Either TLS is already established or server does not support TLS 
                                if (!(thisPtr.connection.pooledStream.NetworkStream is TlsStream))
                                {
                                    throw new SmtpException(SR.GetString(SR.MailServerDoesNotSupportStartTls));
                                } 
                            }
 
                            thisPtr.SendStartTls(); 
#else // FEATURE_PAL
                            throw new NotSupportedException("ROTORTODO"); 
#endif // !FEATURE_PAL
                        }
                        else {
                            thisPtr.Authenticate(); 
                        }
                    } 
                    catch (Exception e) 
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                }
            }
 
            bool SendHello()//6
            { 
                IAsyncResult result = HelloCommand.BeginSend(connection, connection.client.localHostName, sendHelloCallback, this); 
                //if ehello isn't supported, assume basic auth
                if (result.CompletedSynchronously) 
                {
                    connection.supportedAuth = SupportedAuth.Login;
                    HelloCommand.EndSend(result);
                    Authenticate(); 
                    return true;
                } 
                return false; 
            }
 
            static void SendHelloCallback(IAsyncResult result)     //7
            {
                if (!result.CompletedSynchronously)
                { 
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try 
                    { 
                        HelloCommand.EndSend(result);
                        thisPtr.Authenticate(); 
                    }
                    catch (Exception e)
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            } 

#if !FEATURE_PAL 
            bool SendStartTls()//6
            {
                IAsyncResult result = StartTlsCommand.BeginSend(connection, SendStartTlsCallback, this);
                if (result.CompletedSynchronously) 
                {
                    StartTlsCommand.EndSend(result); 
                    TlsStream TlsStream = new TlsStream(connection.pooledStream.ServicePoint.Host, connection.pooledStream.NetworkStream, connection.ClientCertificates, connection.pooledStream.ServicePoint, connection.client, m_OuterResult.ContextCopy); 
                    connection.pooledStream.NetworkStream= TlsStream;
                    connection.responseReader = new SmtpReplyReaderFactory(connection.pooledStream.NetworkStream); 
                    SendEHello();
                    return true;
                }
                return false; 
            }
 
            static void SendStartTlsCallback(IAsyncResult result)     //7 
            {
                if (!result.CompletedSynchronously) 
                {
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try
                    { 
                        StartTlsCommand.EndSend(result);
                        TlsStream TlsStream = new TlsStream(thisPtr.connection.pooledStream.ServicePoint.Host, thisPtr.connection.pooledStream.NetworkStream, thisPtr.connection.ClientCertificates, thisPtr.connection.pooledStream.ServicePoint, thisPtr.connection.client, thisPtr.m_OuterResult.ContextCopy); 
                        thisPtr.connection.pooledStream.NetworkStream= TlsStream; 
                        thisPtr.connection.responseReader = new SmtpReplyReaderFactory(thisPtr.connection.pooledStream.NetworkStream);
                        thisPtr.SendEHello(); 
                    }
                    catch (Exception e)
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            } 
#endif // !FEATURE_PAL
 
            void Authenticate() //8
            {
                //if no credentials were supplied, try anonymous
                //servers don't appear to anounce that they support anonymous login. 
                if (connection.credentials != null) {
                    while (++currentModule < connection.authenticationModules.Length) 
                    { 
                        //only authenticate if the auth protocol is supported
                        ISmtpAuthenticationModule module = connection.authenticationModules[currentModule]; 
                        if (!connection.AuthSupported(module)) {
                            continue;
                        }
 
                        NetworkCredential credential = connection.credentials.GetCredential(host, port, module.AuthenticationType);
                        if (credential ==null) 
                            continue; 
                        Authorization auth = connection.SetContextAndTryAuthenticate(module, credential, m_OuterResult);
 
                        if (auth != null && auth.Message != null)
                        {
                            IAsyncResult result = AuthCommand.BeginSend(connection, connection.authenticationModules[currentModule].AuthenticationType, auth.Message, authenticateCallback, this);
                            if (!result.CompletedSynchronously) 
                            {
                                return; 
                            } 

                            LineInfo info = AuthCommand.EndSend(result); 

                            if ((int)info.StatusCode == 334)
                            {
                                authResponse = info.Line; 
                                if (!AuthenticateContinue())
                                { 
                                    return; 
                                }
                            } 
                            else if ((int)info.StatusCode == 235)
                            {
                                module.CloseContext(connection);
                                connection.isConnected = true; 
                                break;
                            } 
                        } 
                    }
 
                    //try anonymous if didn't authenticate
                    //if (!connection.isConnected) {
                    //    throw new SmtpException(SR.GetString(SR.SmtpAuthenticationFailed));
                   // } 
                }
 
                connection.isConnected = true; 
                InvokeCallback();
            } 

            static void AuthenticateCallback(IAsyncResult result) //9
            {
                if (!result.CompletedSynchronously) 
                {
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState; 
                    try 
                    {
                        LineInfo info = AuthCommand.EndSend(result); 

                        if ((int)info.StatusCode == 334)
                        {
                            thisPtr.authResponse = info.Line; 
                            if (!thisPtr.AuthenticateContinue())
                            { 
                                return; 
                            }
                        } 
                        else if ((int)info.StatusCode == 235)
                        {
                            thisPtr.connection.authenticationModules[thisPtr.currentModule].CloseContext(thisPtr.connection);
                            thisPtr.connection.isConnected = true; 
                            thisPtr.InvokeCallback();
                            return; 
                        } 

                        thisPtr.Authenticate(); 
                    }
                    catch (Exception e)
                    {
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            } 

            bool AuthenticateContinue()        //10 
            {
                for (;;)
                {
                    // We don't need credential on the continued auth assuming they were captured on the first call. 
                    // That should always work, otherwise what if a new credential has been returned?
                    Authorization auth = connection.authenticationModules[currentModule].Authenticate(authResponse, null, connection); 
                    if (auth == null) 
                    {
                        throw new SmtpException(SR.GetString(SR.SmtpAuthenticationFailed)); 
                    }

                    IAsyncResult result = AuthCommand.BeginSend(connection, auth.Message, authenticateContinueCallback, this);
                    if (!result.CompletedSynchronously) 
                    {
                        return false; 
                    } 

                    LineInfo info = AuthCommand.EndSend(result); 
                    if ((int)info.StatusCode == 235)
                    {
                        connection.authenticationModules[currentModule].CloseContext(connection);
                        connection.isConnected = true; 
                        InvokeCallback();
                        return false; 
                    } 
                    else if ((int)info.StatusCode != 334)
                    { 
                        return true;
                    }
                    authResponse = info.Line;
                } 
            }
 
            static void AuthenticateContinueCallback(IAsyncResult result)     //11 
            {
                if (!result.CompletedSynchronously) 
                {
                    ConnectAndHandshakeAsyncResult thisPtr = (ConnectAndHandshakeAsyncResult)result.AsyncState;
                    try
                    { 
                        LineInfo info = AuthCommand.EndSend(result);
                        if ((int)info.StatusCode == 235) 
                        { 
                            thisPtr.connection.authenticationModules[thisPtr.currentModule].CloseContext(thisPtr.connection);
                            thisPtr.connection.isConnected = true; 
                            thisPtr.InvokeCallback();
                            return;
                        }
                        else if ((int)info.StatusCode == 334) 
                        {
                            thisPtr.authResponse = info.Line; 
                            if (!thisPtr.AuthenticateContinue()) 
                            {
                                return; 
                            }
                        }
                        thisPtr.Authenticate();
                    } 
                    catch (Exception e)
                    { 
                        thisPtr.InvokeCallback(e); 
                    }
                } 
            }

        }
    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.
                        

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