added MaxAuthenticationAttempts and support for IPv6 literals

Src/SampleApp/Program.cs

@@ -14,41 +14,40 @@ namespace SampleApp
 {
     class Program
     {
-        static Task Main(string[] args)
+        static async Task Main(string[] args)
         {
-            CustomEndpointListenerExample.Run();
+            //CustomEndpointListenerExample.Run();
 
-            //ServicePointManager.ServerCertificateValidationCallback = SmtpServerTests.IgnoreCertificateValidationFailureForTestingOnly;
+            ServicePointManager.ServerCertificateValidationCallback = SmtpServerTests.IgnoreCertificateValidationFailureForTestingOnly;
 
             //var options = new SmtpServerOptionsBuilder()
             //    .ServerName("SmtpServer SampleApp")
             //    .Port(587, false)
-            //    .Certificate(SmtpServerTests.CreateCertificate())
+            //    //.Certificate(SmtpServerTests.CreateCertificate())
             //    .Build();
 
-            ////var options = new SmtpServerOptionsBuilder()
-            ////    .ServerName("SmtpServer SampleApp")
-            ////    .Endpoint(endpoint =>
-            ////        endpoint
-            ////            .Port(587, true)
-            ////            .AllowUnsecureAuthentication(false)
-            ////            .AuthenticationRequired(false))
-            ////    .Certificate(SmtpServerTests.CreateCertificate())
-            ////    .Build();
+            var options = new SmtpServerOptionsBuilder()
+                .ServerName("SmtpServer SampleApp")
+                .Endpoint(endpoint =>
+                    endpoint
+                        .Port(587)
+                        .AllowUnsecureAuthentication(true)
+                        .AuthenticationRequired(false))
+                .UserAuthenticator(new SampleUserAuthenticator())
+                //.Certificate(SmtpServerTests.CreateCertificate())
+                .Build();
 
-            //var server = new SmtpServer.SmtpServer(options);
+            var server = new SmtpServer.SmtpServer(options);
 
-            //server.SessionCreated += OnSessionCreated;
-            //server.SessionCompleted += OnSessionCompleted;
-            //server.SessionFaulted += OnSessionFaulted;
+            server.SessionCreated += OnSessionCreated;
+            server.SessionCompleted += OnSessionCompleted;
+            server.SessionFaulted += OnSessionFaulted;
 
-            //var serverTask = server.StartAsync(CancellationToken.None);
+            var serverTask = server.StartAsync(CancellationToken.None);
 
-            //Console.ReadKey();
+            Console.ReadKey();
 
-            //await serverTask.ConfigureAwait(false);
-
-            return Task.CompletedTask;
+            await serverTask.ConfigureAwait(false);
         }
 
         static void OnSessionFaulted(object sender, SessionFaultedEventArgs e)

Src/SmtpServer/ISmtpServerOptions.cs

@@ -20,6 +20,11 @@ public interface ISmtpServerOptions
         /// </summary>
         int MaxRetryCount { get; }
 
+        /// <summary>
+        /// The maximum number of authentication attempts.
+        /// </summary>
+        int MaxAuthenticationAttempts { get; }
+
         /// <summary>
         /// Gets the SMTP server name.
         /// </summary>

Src/SmtpServer/Protocol/AuthCommand.cs

@@ -62,7 +62,16 @@ internal override async Task<bool> ExecuteAsync(SmtpSessionContext context, Canc
             {
                 if (await container.Instance.AuthenticateAsync(context, _user, _password, cancellationToken).ConfigureAwait(false) == false)
                 {
-                    await context.NetworkClient.ReplyAsync(SmtpResponse.AuthenticationFailed, cancellationToken).ConfigureAwait(false);
+                    var remaining = context.ServerOptions.MaxAuthenticationAttempts - ++context.AuthenticationAttempts;
+                    var response = new SmtpResponse(SmtpReplyCode.AuthenticationFailed, $"authentication failed, {remaining} attempt(s) remaining.");
+
+                    await context.NetworkClient.ReplyAsync(response, cancellationToken).ConfigureAwait(false);
+
+                    if (remaining <= 0)
+                    {
+                        throw new SmtpResponseException(SmtpResponse.ServiceClosingTransmissionChannel, true);
+                    }
+
                     return false;
                 }
             }

Src/SmtpServer/Protocol/SmtpParser.cs

@@ -657,56 +657,77 @@ public bool TryMakeSnum(out int snum)
         /// Try to make Ip version from ip version tag which is a formatted text IPv[Version]:
         /// </summary>
         /// <param name="version">IP version. IPv6 is supported atm.</param>
-        /// <returns>true if ip version tag can be extracted</returns>
+        /// <returns>true if ip version tag can be extracted.</returns>
         public bool TryMakeIpVersion(out int version)
         {
             version = default;
-            var tag = Enumerator.Peek();
-            if (tag != Tokens.Text.IpVersionTag)
+
+            if (Enumerator.Take() != Tokens.Text.IpVersionTag)
+            { 
                 return false;
-            Enumerator.Take();
-            var versionToken = Enumerator.Take();
-            if (versionToken.Kind == TokenKind.Number && int.TryParse(versionToken.Text, out var v))
+            }
+
+            var token = Enumerator.Take();
+
+            if (token.Kind == TokenKind.Number && int.TryParse(token.Text, out var v))
             {
                 version = v;
                 return Enumerator.Take() == Tokens.Colon;
             }
+
             return false;
         }
 
         /// <summary>
-        /// Try to make 16 bits hex number
+        /// Try to make 16 bits hex number.
         /// </summary>
-        /// <param name="hexNumber">Extracted hex number</param>
-        /// <returns>true if valid hex number can be extracted</returns>
+        /// <param name="hexNumber">Extracted hex number.</param>
+        /// <returns>true if valid hex number can be extracted.</returns>
         public bool TryMake16BitsHexNumber(out string hexNumber)
         {
             hexNumber = null;
+
             var token = Enumerator.Peek();
             while (token.Kind == TokenKind.Number || token.Kind == TokenKind.Text)
             {
                 if (hexNumber != null && (hexNumber.Length + token.Text.Length) > 4)
+                { 
                     return false;
-                // Validate hex chars
-                if (token.Kind == TokenKind.Text && !token.Text.ToUpperInvariant().All(c => c >= 'A' && c <= 'F'))
+                }
+
+                if (token.Kind == TokenKind.Text && IsHex(token.Text) == false)
+                {
                     return false;
+                }
+
                 hexNumber = string.Concat(hexNumber ?? string.Empty, token.Text);
+
                 Enumerator.Take();
                 token = Enumerator.Peek();
             }
+
             return true;
+
+            bool IsHex(string text)
+            {
+                return text.ToUpperInvariant().All(c => c >= 'A' && c <= 'F');
+            }
         }
 
         /// <summary>
         /// Try to extract IPv6 address. https://tools.ietf.org/html/rfc4291 section 2.2 used for specification.
         /// </summary>
-        /// <param name="address">Extracted Ipv6 address</param>
-        /// <returns>true if a valid Ipv6 address can be extracted</returns>
+        /// <param name="address">Extracted Ipv6 address.</param>
+        /// <returns>true if a valid Ipv6 address can be extracted.</returns>
         public bool TryMakeIpv6AddressLiteral(out string address)
         {
             address = null;
-            if ((TryMake(TryMakeIpVersion, out int ipVersion) == false) || ipVersion != 6)
+
+            if (TryMake(TryMakeIpVersion, out int ipVersion) == false || ipVersion != 6)
+            { 
                 return false;
+            }
+
             var hasDoubleColumn = false;
             var hexPartCount = 0;
             var hasIpv4Part = false;
@@ -729,15 +750,11 @@ public bool TryMakeIpv6AddressLiteral(out string address)
                             builder.Append(ipv4);
                             break;
                         }
-                        else
-                        {
-                            return false;
-                        }
-                    }
-                    else
-                    {
-                        cp.Rollback();
+
+                        return false;
                     }
+
+                    cp.Rollback();
                 }
 
                 if (token == Tokens.Colon)
@@ -746,7 +763,9 @@ public bool TryMakeIpv6AddressLiteral(out string address)
                     {
                         // Double column is allowed only once
                         if (hasDoubleColumn)
+                        { 
                             return false;
+                        }
                         hasDoubleColumn = true;
                     }
                     builder.Append(token.Text);
@@ -756,7 +775,10 @@ public bool TryMakeIpv6AddressLiteral(out string address)
                 else
                 {
                     if (wasColon == false && builder.Length > 0)
+                    { 
                         return false;
+                    }
+
                     wasColon = false;
                     if (TryMake(TryMake16BitsHexNumber, out string hexNumber))
                     {
@@ -775,7 +797,9 @@ public bool TryMakeIpv6AddressLiteral(out string address)
 
             var maxAllowedParts = (hasIpv4Part ? 6 : 8) - Math.Sign(hasDoubleColumn ? 1 : 0);
             if ((hasDoubleColumn && hexPartCount > maxAllowedParts) || (!hasDoubleColumn && hexPartCount != maxAllowedParts))
+            { 
                 return false;
+            }
 
             return true;
         }

Src/SmtpServer/SmtpServer.csproj

@@ -5,7 +5,7 @@
     <LangVersion>7.2</LangVersion>
     <AssemblyName>SmtpServer</AssemblyName>
     <RootNamespace>SmtpServer</RootNamespace>
-    <Version>6.4.1-RC1</Version>
+    <Version>6.5.0</Version>
     <Description>.NET SmtpServer</Description>
     <Authors>Cain O'Sullivan</Authors>
     <Company />
@@ -15,9 +15,9 @@
     <PackageTags>smtp smtpserver smtp server</PackageTags>
     <PackageLicenseUrl></PackageLicenseUrl>
     <PackageRequireLicenseAcceptance>True</PackageRequireLicenseAcceptance>
-    <AssemblyVersion>6.4.1.0</AssemblyVersion>
-    <FileVersion>6.4.1.0</FileVersion>
-    <PackageReleaseNotes>Added the SessionFaulted event to the SmtpServer.</PackageReleaseNotes>
+    <AssemblyVersion>6.5.0.0</AssemblyVersion>
+    <FileVersion>6.5.0.0</FileVersion>
+    <PackageReleaseNotes>Added MaxAuthenticationAttempts and support for IPv6 addresses.</PackageReleaseNotes>
     <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
     <PackageLicenseFile>LICENSE</PackageLicenseFile>
   </PropertyGroup>

Src/SmtpServer/SmtpServerOptionsBuilder.cs

@@ -26,6 +26,7 @@ public ISmtpServerOptions Build()
                 MailboxFilterFactory = DoNothingMailboxFilter.Instance,
                 UserAuthenticatorFactory = DoNothingUserAuthenticator.Instance,
                 MaxRetryCount = 5,
+                MaxAuthenticationAttempts = 3,
                 SupportedSslProtocols = SslProtocols.Tls12,
                 NetworkBufferSize = 128,
                 NetworkBufferReadTimeout = TimeSpan.FromMinutes(2),
@@ -187,6 +188,18 @@ public SmtpServerOptionsBuilder MaxRetryCount(int value)
             return this;
         }
 
+        /// <summary>
+        /// Sets the maximum number of authentication attempts.
+        /// </summary>
+        /// <param name="value">The maximum number of authentication attempts for a failed authentication.</param>
+        /// <returns>A OptionsBuilder to continue building on.</returns>
+        public SmtpServerOptionsBuilder MaxAuthenticationAttempts(int value)
+        {
+            _setters.Add(options => options.MaxAuthenticationAttempts = value);
+
+            return this;
+        }
+
         /// <summary>
         /// Sets the supported SSL protocols.
         /// </summary>
@@ -261,6 +274,11 @@ class SmtpServerOptions : ISmtpServerOptions
             /// </summary>
             public int MaxRetryCount { get; set; }
 
+            /// <summary>
+            /// The maximum number of authentication attempts.
+            /// </summary>
+            public int MaxAuthenticationAttempts { get; set; }
+
             /// <summary>
             /// Gets or sets the SMTP server name.
             /// </summary>

Src/SmtpServer/SmtpSession.cs

@@ -84,33 +84,37 @@ async Task ExecuteAsync(SmtpSessionContext context, CancellationToken cancellati
                     return;
                 }
 
-                if (TryMake(context, text, out var command, out var response))
+                if (TryMake(context, text, out var command, out var response) == false)
                 {
-                    try
+                    await context.NetworkClient.ReplyAsync(CreateErrorResponse(response, retries), cancellationToken).ConfigureAwait(false);
+                    continue;
+                }
+
+                try
+                {
+                    if (await ExecuteAsync(command, context, cancellationToken).ConfigureAwait(false))
                     {
-                        if (await ExecuteAsync(command, context, cancellationToken).ConfigureAwait(false))
-                        {
-                            _stateMachine.Transition(context);
-                        }
-
-                        retries = _context.ServerOptions.MaxRetryCount;
-
-                        continue;
+                        _stateMachine.Transition(context);
                     }
-                    catch (SmtpResponseException responseException)
-                    {
-                        context.IsQuitRequested = responseException.IsQuitRequested;
 
-                        response = responseException.Response;
-                    }
-                    catch (OperationCanceledException)
-                    {
-                        await context.NetworkClient.ReplyAsync(new SmtpResponse(SmtpReplyCode.ServiceClosingTransmissionChannel, "The session has be cancelled."), cancellationToken).ConfigureAwait(false);
-                        return;
-                    }
+                    retries = _context.ServerOptions.MaxRetryCount;
                 }
+                catch (SmtpResponseException responseException) when (responseException.IsQuitRequested)
+                {
+                    await context.NetworkClient.ReplyAsync(responseException.Response, cancellationToken).ConfigureAwait(false);
+                    return;
+                }
+                catch (SmtpResponseException responseException)
+                {
+                    response = CreateErrorResponse(responseException.Response, retries);
 
-                await context.NetworkClient.ReplyAsync(CreateErrorResponse(response, retries), cancellationToken).ConfigureAwait(false);
+                    await context.NetworkClient.ReplyAsync(response, cancellationToken).ConfigureAwait(false);
+                }
+                catch (OperationCanceledException)
+                {
+                    await context.NetworkClient.ReplyAsync(new SmtpResponse(SmtpReplyCode.ServiceClosingTransmissionChannel, "The session has be cancelled."), cancellationToken).ConfigureAwait(false);
+                    return;
+                }
             }
         }
 

Src/SmtpServer/SmtpSessionContext.cs

@@ -78,6 +78,11 @@ internal void RaiseSessionAuthenticated()
         /// </summary>
         public AuthenticationContext Authentication { get; internal set; } = AuthenticationContext.Unauthenticated;
 
+        /// <summary>
+        /// Returns the number of athentication attempts.
+        /// </summary>
+        public int AuthenticationAttempts { get; internal set; }
+
         /// <summary>
         /// Gets a value indicating whether a quit has been requested.
         /// </summary>

Src/SmtpServer/Text/ITokenEnumerator.cs

@@ -12,7 +12,7 @@ public interface ITokenEnumerator
         Token Peek();
 
         /// <summary>
-        /// Take the given number of tokens.
+        /// Take the next token.
         /// </summary>
         /// <returns>The last token that was consumed.</returns>
         Token Take();

Src/SmtpServer/Text/TokenEnumerator.cs

@@ -31,7 +31,7 @@ public Token Peek()
         }
 
         /// <summary>
-        /// Take the given number of tokens.
+        /// Take the next token.
         /// </summary>
         /// <returns>The last token that was consumed.</returns>
         public Token Take()
@@ -40,7 +40,7 @@ public Token Take()
         }
 
         /// <summary>
-        /// Take the given number of tokens.
+        /// Returns the token at the given index.
         /// </summary>
         /// <returns>The last token that was consumed.</returns>
         Token At(int index)