feat: Implement Deno-native STARTTLS handler and connection wrapper

- Refactored STARTTLS implementation to use Deno's native TLS via Deno.startTls().
- Introduced ConnectionWrapper to provide a Node.js net.Socket-compatible interface for Deno.Conn and Deno.TlsConn.
- Updated TlsHandler to utilize the new STARTTLS implementation.
- Added comprehensive SMTP authentication tests for PLAIN and LOGIN mechanisms.
- Implemented rate limiting tests for SMTP server connections and commands.
- Enhanced error handling and logging throughout the STARTTLS and connection upgrade processes.

ts/mail/delivery/smtpserver/tls-handler.ts

@@ -110,100 +110,84 @@ export class TlsHandler implements ITlsHandler {
   }
   
   /**
-   * Upgrade a connection to TLS
+   * Upgrade a connection to TLS using Deno-native implementation
    * @param socket - Client socket
    */
-  public async startTLS(socket: plugins.net.Socket): Promise<plugins.tls.TLSSocket> {
+  public async startTLS(socket: plugins.net.Socket): Promise<plugins.tls.TLSSocket | any> {
     // Get the session for this socket
     const session = this.smtpServer.getSessionManager().getSession(socket);
-    
+
     try {
-      // Import the enhanced STARTTLS handler
-      // This uses a more robust approach to TLS upgrades
+      // Use the unified STARTTLS implementation (Deno-native)
       const { performStartTLS } = await import('./starttls-handler.ts');
-      
-      SmtpLogger.info('Using enhanced STARTTLS implementation');
-      
-      // Use the enhanced STARTTLS handler with better error handling and socket management
+
+      SmtpLogger.info('Starting STARTTLS upgrade', {
+        remoteAddress: socket.remoteAddress,
+        remotePort: socket.remotePort
+      });
+
       const serverOptions = this.smtpServer.getOptions();
       const tlsSocket = await performStartTLS(socket, {
         key: serverOptions.key,
         cert: serverOptions.cert,
         ca: serverOptions.ca,
-        session: session,
+        session,
         sessionManager: this.smtpServer.getSessionManager(),
         connectionManager: this.smtpServer.getConnectionManager(),
-        // Callback for successful upgrade
         onSuccess: (secureSocket) => {
-          SmtpLogger.info('TLS connection successfully established via enhanced STARTTLS', {
+          SmtpLogger.info('TLS connection successfully established', {
             remoteAddress: secureSocket.remoteAddress,
-            remotePort: secureSocket.remotePort,
-            protocol: secureSocket.getProtocol() || 'unknown',
-            cipher: secureSocket.getCipher()?.name || 'unknown'
+            remotePort: secureSocket.remotePort
           });
-          
-          // Log security event
+
           SmtpLogger.logSecurityEvent(
             SecurityLogLevel.INFO,
             SecurityEventType.TLS_NEGOTIATION,
-            'STARTTLS successful with enhanced implementation',
-            { 
-              protocol: secureSocket.getProtocol(),
-              cipher: secureSocket.getCipher()?.name
-            },
+            'STARTTLS successful',
+            {},
             secureSocket.remoteAddress,
             undefined,
             true
           );
         },
-        // Callback for failed upgrade
         onFailure: (error) => {
-          SmtpLogger.error(`Enhanced STARTTLS failed: ${error.message}`, {
+          SmtpLogger.error(`STARTTLS failed: ${error.message}`, {
             sessionId: session?.id,
             remoteAddress: socket.remoteAddress,
             error
           });
-          
-          // Log security event
+
           SmtpLogger.logSecurityEvent(
             SecurityLogLevel.ERROR,
             SecurityEventType.TLS_NEGOTIATION,
-            'Enhanced STARTTLS failed',
+            'STARTTLS failed',
             { error: error.message },
             socket.remoteAddress,
             undefined,
             false
           );
         },
-        // Function to update session state
         updateSessionState: this.smtpServer.getSessionManager().updateSessionState?.bind(this.smtpServer.getSessionManager())
       });
-      
-      // If STARTTLS failed with the enhanced implementation, log the error
+
       if (!tlsSocket) {
-        SmtpLogger.warn('Enhanced STARTTLS implementation failed to create TLS socket', {
-          sessionId: session?.id,
-          remoteAddress: socket.remoteAddress
-        });
         throw new Error('Failed to create TLS socket');
       }
-      
+
       return tlsSocket;
     } catch (error) {
-      // Log STARTTLS failure
       SmtpLogger.error(`Failed to upgrade connection to TLS: ${error instanceof Error ? error.message : String(error)}`, {
         remoteAddress: socket.remoteAddress,
         remotePort: socket.remotePort,
         error: error instanceof Error ? error : new Error(String(error)),
         stack: error instanceof Error ? error.stack : 'No stack trace available'
       });
-      
-      // Log security event
+
       SmtpLogger.logSecurityEvent(
         SecurityLogLevel.ERROR,
         SecurityEventType.TLS_NEGOTIATION,
         'Failed to upgrade connection to TLS',
-        { 
+        {
           error: error instanceof Error ? error.message : String(error),
           stack: error instanceof Error ? error.stack : 'No stack trace available'
         },
@@ -211,8 +195,7 @@ export class TlsHandler implements ITlsHandler {
         undefined,
         false
       );
-      
-      // Destroy the socket on error
+
       socket.destroy();
       throw error;
     }