Add tests for various SMTP authentication methods

Implemented new test cases for different SMTP authentication methods including PLAIN, LOGIN, XOAUTH2, and various SCRAM mechanisms. These tests ensure that the client can correctly handle both successful and failing authentication scenarios, as well as unsupported authentication types.

client_test.go

@@ -1821,10 +1821,27 @@ func TestClient_DialWithContext(t *testing.T) {
 		}
 	})
 	t.Run("connect with failing auth", func(t *testing.T) {
+		ctxAuth, cancelAuth := context.WithCancel(context.Background())
+		defer cancelAuth()
+		PortAdder.Add(1)
+		authServerPort := int(TestServerPortBase + PortAdder.Load())
+		authFeatureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250-STARTTLS\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctxAuth, t, &serverProps{
+				FailOnAuth: true,
+				FeatureSet: authFeatureSet,
+				ListenPort: authServerPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 300)
+
 		ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
 		t.Cleanup(cancelDial)
 
-		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS),
+		client, err := NewClient(DefaultHost, WithPort(authServerPort), WithTLSPolicy(NoTLS),
 			WithSMTPAuth(SMTPAuthPlain), WithUsername("invalid"), WithPassword("invalid"))
 		if err != nil {
 			t.Fatalf("failed to create new client: %s", err)
@@ -1863,6 +1880,67 @@ func TestClient_DialWithContext(t *testing.T) {
 			t.Fatalf("failed to connect to the test server: %s", err)
 		}
 	})
+	t.Run("connect with STARTTLS Opportunisticly", func(t *testing.T) {
+		ctxTLS, cancelTLS := context.WithCancel(context.Background())
+		defer cancelTLS()
+		PortAdder.Add(1)
+		tlsServerPort := int(TestServerPortBase + PortAdder.Load())
+		tlsFeatureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250-STARTTLS\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctxTLS, t, &serverProps{
+				FeatureSet: tlsFeatureSet,
+				ListenPort: tlsServerPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 300)
+		ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+		t.Cleanup(cancelDial)
+
+		tlsConfig := &tls.Config{InsecureSkipVerify: true}
+		client, err := NewClient(DefaultHost, WithPort(tlsServerPort), WithTLSPolicy(TLSOpportunistic),
+			WithTLSConfig(tlsConfig), WithSMTPAuth(SMTPAuthPlain), WithUsername(TestUserValid),
+			WithPassword(TestPasswordValid))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+		if err = client.DialWithContext(ctxDial); err != nil {
+			t.Fatalf("failed to connect to the test server: %s", err)
+		}
+	})
+	t.Run("connect with STARTTLS but fail", func(t *testing.T) {
+		ctxTLS, cancelTLS := context.WithCancel(context.Background())
+		defer cancelTLS()
+		PortAdder.Add(1)
+		tlsServerPort := int(TestServerPortBase + PortAdder.Load())
+		tlsFeatureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250-STARTTLS\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctxTLS, t, &serverProps{
+				FailOnSTARTTLS: true,
+				FeatureSet:     tlsFeatureSet,
+				ListenPort:     tlsServerPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 300)
+		ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+		t.Cleanup(cancelDial)
+
+		tlsConfig := &tls.Config{InsecureSkipVerify: true}
+		client, err := NewClient(DefaultHost, WithPort(tlsServerPort), WithTLSPolicy(TLSMandatory),
+			WithTLSConfig(tlsConfig), WithSMTPAuth(SMTPAuthPlain), WithUsername(TestUserValid),
+			WithPassword(TestPasswordValid))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+		if err = client.DialWithContext(ctxDial); err == nil {
+			t.Fatalf("connection was supposed to fail, but didn't")
+		}
+	})
 	t.Run("want STARTTLS, but server does not support it", func(t *testing.T) {
 		ctxTLS, cancelTLS := context.WithCancel(context.Background())
 		defer cancelTLS()
@@ -2186,6 +2264,123 @@ func TestClient_DialAndSendWithContext(t *testing.T) {
 	})
 }
 
+func TestClient_auth(t *testing.T) {
+	tests := []struct {
+		name     string
+		authType SMTPAuthType
+	}{
+		{"CRAM-MD5", SMTPAuthCramMD5},
+		{"LOGIN", SMTPAuthLogin},
+		{"LOGIN-NOENC", SMTPAuthLoginNoEnc},
+		{"PLAIN", SMTPAuthPlain},
+		{"PLAIN-NOENC", SMTPAuthPlainNoEnc},
+		{"SCRAM-SHA-1", SMTPAuthSCRAMSHA1},
+		{"SCRAM-SHA-1-PLUS", SMTPAuthSCRAMSHA1PLUS},
+		{"SCRAM-SHA-256", SMTPAuthSCRAMSHA256},
+		{"SCRAM-SHA-256-PLUS", SMTPAuthSCRAMSHA256PLUS},
+		{"XOAUTH2", SMTPAuthXOAUTH2},
+	}
+
+	tlsConfig := tls.Config{InsecureSkipVerify: true}
+	for _, tt := range tests {
+		t.Run(tt.name+" should succeed", func(t *testing.T) {
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+			PortAdder.Add(1)
+			serverPort := int(TestServerPortBase + PortAdder.Load())
+			featureSet := "250-AUTH " + tt.name + "\r\n250-STARTTLS\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+			go func() {
+				if err := simpleSMTPServer(ctx, t, &serverProps{
+					FeatureSet: featureSet,
+					ListenPort: serverPort,
+				}); err != nil {
+					t.Errorf("failed to start test server: %s", err)
+					return
+				}
+			}()
+			time.Sleep(time.Millisecond * 300)
+
+			ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+			t.Cleanup(cancelDial)
+
+			client, err := NewClient(DefaultHost, WithTLSPolicy(NoTLS), WithPort(serverPort),
+				WithTLSPolicy(TLSMandatory), WithSMTPAuth(tt.authType), WithTLSConfig(&tlsConfig),
+				WithUsername("test"), WithPassword("password"))
+			if err != nil {
+				t.Fatalf("failed to create new client: %s", err)
+			}
+			if err = client.DialWithContext(ctxDial); err != nil {
+				t.Fatalf("failed to connect to test service: %s", err)
+			}
+			if err := client.Close(); err != nil {
+				t.Errorf("failed to close client connection: %s", err)
+			}
+
+		})
+		t.Run(tt.name+" should fail", func(t *testing.T) {
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+			PortAdder.Add(1)
+			serverPort := int(TestServerPortBase + PortAdder.Load())
+			featureSet := "250-AUTH " + tt.name + "\r\n250-STARTTLS\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+			go func() {
+				if err := simpleSMTPServer(ctx, t, &serverProps{
+					FailOnAuth: true,
+					FeatureSet: featureSet,
+					ListenPort: serverPort,
+				}); err != nil {
+					t.Errorf("failed to start test server: %s", err)
+					return
+				}
+			}()
+			time.Sleep(time.Millisecond * 300)
+
+			ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+			t.Cleanup(cancelDial)
+
+			client, err := NewClient(DefaultHost, WithTLSPolicy(NoTLS), WithPort(serverPort),
+				WithTLSPolicy(TLSMandatory), WithSMTPAuth(tt.authType), WithTLSConfig(&tlsConfig),
+				WithUsername("test"), WithPassword("password"))
+			if err != nil {
+				t.Fatalf("failed to create new client: %s", err)
+			}
+			if err = client.DialWithContext(ctxDial); err == nil {
+				t.Fatalf("client should have failed to connect")
+			}
+		})
+		t.Run(tt.name+" should fail as unspported", func(t *testing.T) {
+			ctx, cancel := context.WithCancel(context.Background())
+			defer cancel()
+			PortAdder.Add(1)
+			serverPort := int(TestServerPortBase + PortAdder.Load())
+			featureSet := "250-AUTH UNKNOWN\r\n250-8BITMIME\r\n250-STARTTLS\r\n250-DSN\r\n250 SMTPUTF8"
+			go func() {
+				if err := simpleSMTPServer(ctx, t, &serverProps{
+					FeatureSet: featureSet,
+					ListenPort: serverPort,
+				}); err != nil {
+					t.Errorf("failed to start test server: %s", err)
+					return
+				}
+			}()
+			time.Sleep(time.Millisecond * 300)
+
+			ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+			t.Cleanup(cancelDial)
+
+			client, err := NewClient(DefaultHost, WithTLSPolicy(NoTLS), WithPort(serverPort),
+				WithTLSPolicy(TLSMandatory), WithSMTPAuth(tt.authType), WithTLSConfig(&tlsConfig),
+				WithUsername("test"), WithPassword("password"))
+			if err != nil {
+				t.Fatalf("failed to create new client: %s", err)
+			}
+			if err = client.DialWithContext(ctxDial); err == nil {
+				t.Fatalf("client should have failed to connect")
+			}
+		})
+	}
+}
+
 /*
 
 
@@ -2202,55 +2397,6 @@ func TestClient_checkConn(t *testing.T) {
 	}
 }
 
-// TestClient_DiealWithContextOptions tests the DialWithContext method plus different options
-// for the Client object
-func TestClient_DialWithContextOptions(t *testing.T) {
-	tests := []struct {
-		name    string
-		wantssl bool
-		wanttls TLSPolicy
-		sf      bool
-	}{
-		{"Want SSL (should fail)", true, NoTLS, true},
-		{"Want Mandatory TLS", false, TLSMandatory, false},
-	}
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			c, err := getTestConnection(true)
-			if err != nil {
-				t.Skipf("failed to create test client: %s. Skipping tests", err)
-			}
-			if tt.wantssl {
-				c.SetSSL(true)
-			}
-			if tt.wanttls != NoTLS {
-				c.SetTLSPolicy(tt.wanttls)
-			}
-
-			ctx := context.Background()
-			if err = c.DialWithContext(ctx); err != nil && !tt.sf {
-				t.Errorf("failed to dial with context: %s", err)
-				return
-			}
-			if !tt.sf {
-				if c.smtpClient == nil && !tt.sf {
-					t.Errorf("DialWithContext didn't fail but no SMTP client found.")
-					return
-				}
-				if !c.smtpClient.HasConnection() && !tt.sf {
-					t.Errorf("DialWithContext didn't fail but no connection found.")
-					return
-				}
-				if err = c.Reset(); err != nil {
-					t.Errorf("failed to reset connection: %s", err)
-				}
-				if err = c.Close(); err != nil {
-					t.Errorf("failed to close connection: %s", err)
-				}
-			}
-		})
-	}
-}
 
 // TestClient_DialWithContextOptionDialContextFunc tests the DialWithContext method plus
 // use dialContextFunc option for the Client object
@@ -4019,6 +4165,7 @@ func testingKey(s string) string { return strings.ReplaceAll(s, "TESTING KEY", "
 
 // serverProps represents the configuration properties for the SMTP server.
 type serverProps struct {
+	FailOnAuth     bool
 	FailOnData     bool
 	FailOnHelo     bool
 	FailOnQuit     bool
@@ -4083,11 +4230,13 @@ func simpleSMTPServer(ctx context.Context, t *testing.T, props *serverProps) err
 
 func handleTestServerConnection(connection net.Conn, t *testing.T, props *serverProps) {
 	t.Helper()
-	t.Cleanup(func() {
+	if !props.IsTLS {
-		if err := connection.Close(); err != nil {
+		t.Cleanup(func() {
-			t.Logf("failed to close connection: %s", err)
+			if err := connection.Close(); err != nil {
-		}
+				t.Logf("failed to close connection: %s", err)
-	})
+			}
+		})
+	}
 
 	reader := bufio.NewReader(connection)
 	writer := bufio.NewWriter(connection)
@@ -4097,9 +4246,7 @@ func handleTestServerConnection(connection net.Conn, t *testing.T, props *server
 		if err != nil {
 			t.Logf("failed to write line: %s", err)
 		}
-		if err = writer.Flush(); err != nil {
+		_ = writer.Flush()
-			t.Logf("failed to flush line: %s", err)
-		}
 	}
 	writeOK := func() {
 		writeLine("250 2.0.0 OK")
@@ -4148,61 +4295,8 @@ func handleTestServerConnection(connection net.Conn, t *testing.T, props *server
 				break
 			}
 			writeOK()
-		case strings.HasPrefix(data, "AUTH XOAUTH2"):
+		case strings.HasPrefix(data, "AUTH"):
-			auth := strings.TrimPrefix(data, "AUTH XOAUTH2 ")
+			if props.FailOnAuth {
-			if !strings.EqualFold(auth, "dXNlcj11c2VyAWF1dGg9QmVhcmVyIHRva2VuAQE=") {
-				writeLine("535 5.7.8 Error: authentication failed")
-				break
-			}
-			writeLine("235 2.7.0 Authentication successful")
-		case strings.HasPrefix(data, "AUTH PLAIN"):
-			auth := strings.TrimPrefix(data, "AUTH PLAIN ")
-			if !strings.EqualFold(auth, "AHRvbmlAdGVzdGVyLmNvbQBWM3J5UzNjcjN0Kw==") {
-				writeLine("535 5.7.8 Error: authentication failed")
-				break
-			}
-			writeLine("235 2.7.0 Authentication successful")
-		case strings.HasPrefix(data, "AUTH LOGIN"):
-			var username, password string
-			userResp := "VXNlcm5hbWU6"
-			passResp := "UGFzc3dvcmQ6"
-			if strings.Contains(props.FeatureSet, "250-X-MOX-LOGIN") {
-				userResp = ""
-				passResp = "UGFzc3dvcmQ="
-			}
-			if strings.Contains(props.FeatureSet, "250-X-NULLBYTE-LOGIN") {
-				userResp = "VXNlciBuYW1lAA=="
-				passResp = "UGFzc3dvcmQA"
-			}
-			if strings.Contains(props.FeatureSet, "250-X-BOGUS-LOGIN") {
-				userResp = "Qm9ndXM="
-				passResp = "Qm9ndXM="
-			}
-			if strings.Contains(props.FeatureSet, "250-X-EMPTY-LOGIN") {
-				userResp = ""
-				passResp = ""
-			}
-			writeLine("334 " + userResp)
-
-			ddata, derr := reader.ReadString('\n')
-			if derr != nil {
-				fmt.Printf("failed to read username data from connection: %s\n", derr)
-				break
-			}
-			ddata = strings.TrimSpace(ddata)
-			username = ddata
-			writeLine("334 " + passResp)
-
-			ddata, derr = reader.ReadString('\n')
-			if derr != nil {
-				fmt.Printf("failed to read password data from connection: %s\n", derr)
-				break
-			}
-			ddata = strings.TrimSpace(ddata)
-			password = ddata
-
-			if !strings.EqualFold(username, "dG9uaUB0ZXN0ZXIuY29t") ||
-				!strings.EqualFold(password, "VjNyeVMzY3IzdCs=") {
 				writeLine("535 5.7.8 Error: authentication failed")
 				break
 			}