added relay

internal/smtp/submission.go

@@ -47,11 +47,12 @@ func (b *SubmissionBackend) NewSession(c *gosmtp.Conn) (gosmtp.Session, error) {
 
 // SubmissionSession handles one authenticated submission connection.
 type SubmissionSession struct {
-	deps     *Deps
-	clientIP string
-	user     *models.User   // set after AUTH
-	from     string
-	rcpts    []string
+	deps        *Deps
+	clientIP    string
+	user        *models.User // set after AUTH
+	ipRelayMode bool         // set when IP relay authorization succeeds (no AUTH)
+	from        string
+	rcpts       []string
 }
 
 func (s *SubmissionSession) AuthPlain(username, password string) error {
@@ -81,19 +82,49 @@ func (s *SubmissionSession) AuthPlain(username, password string) error {
 }
 
 func (s *SubmissionSession) Mail(from string, opts *gosmtp.MailOptions) error {
-	if s.user == nil {
-		return &gosmtp.SMTPError{Code: 530, Message: "authentication required"}
-	}
-
 	addr, err := mail.ParseAddress(from)
 	if err != nil {
 		return &gosmtp.SMTPError{Code: 501, EnhancedCode: gosmtp.EnhancedCode{5, 1, 7}, Message: "invalid sender"}
 	}
-
-	// Sender must be user's own address or an alias they own.
 	fromEmail := strings.ToLower(addr.Address)
+
+	if s.user == nil {
+		// Unauthenticated — check IP relay rules.
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+
+		allowed, err := s.deps.DB.CheckIPRelay(ctx, s.clientIP, fromEmail)
+		if err != nil {
+			log.Printf("[smtp/submission] ip relay check error from %s: %v", s.clientIP, err)
+			return &gosmtp.SMTPError{Code: 451, EnhancedCode: gosmtp.EnhancedCode{4, 3, 0}, Message: "temporary error"}
+		}
+		if !allowed {
+			return &gosmtp.SMTPError{Code: 530, Message: "authentication required"}
+		}
+		s.ipRelayMode = true
+		s.from = addr.Address
+		return nil
+	}
+
+	if s.user.IsRelay {
+		// Relay account — validate sender against allowed patterns.
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+
+		allowed, err := s.deps.DB.IsRelaySenderAllowed(ctx, s.user.ID, fromEmail)
+		if err != nil {
+			log.Printf("[smtp/submission] relay sender check error for %s: %v", s.user.Email, err)
+			return &gosmtp.SMTPError{Code: 451, EnhancedCode: gosmtp.EnhancedCode{4, 3, 0}, Message: "temporary error"}
+		}
+		if !allowed {
+			return &gosmtp.SMTPError{Code: 553, EnhancedCode: gosmtp.EnhancedCode{5, 1, 8}, Message: "sender not permitted for this relay account"}
+		}
+		s.from = addr.Address
+		return nil
+	}
+
+	// Regular user — sender must be own email or an alias.
 	if !strings.EqualFold(fromEmail, s.user.Email) {
-		// Check aliases.
 		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 		defer cancel()
 
@@ -108,7 +139,7 @@ func (s *SubmissionSession) Mail(from string, opts *gosmtp.MailOptions) error {
 }
 
 func (s *SubmissionSession) Rcpt(to string, opts *gosmtp.RcptOptions) error {
-	if s.user == nil {
+	if s.user == nil && !s.ipRelayMode {
 		return &gosmtp.SMTPError{Code: 530, Message: "authentication required"}
 	}
 
@@ -122,7 +153,7 @@ func (s *SubmissionSession) Rcpt(to string, opts *gosmtp.RcptOptions) error {
 }
 
 func (s *SubmissionSession) Data(r io.Reader) error {
-	if s.user == nil {
+	if s.user == nil && !s.ipRelayMode {
 		return &gosmtp.SMTPError{Code: 530, Message: "authentication required"}
 	}
 	if len(s.rcpts) == 0 {
@@ -137,7 +168,6 @@ func (s *SubmissionSession) Data(r io.Reader) error {
 		return &gosmtp.SMTPError{Code: 552, EnhancedCode: gosmtp.EnhancedCode{5, 3, 4}, Message: "message too large"}
 	}
 
-	// Parse for basic header validation.
 	_, err = mail.ReadMessage(bytes.NewReader(raw))
 	if err != nil {
 		return &gosmtp.SMTPError{Code: 550, EnhancedCode: gosmtp.EnhancedCode{5, 6, 0}, Message: "malformed message"}
@@ -146,22 +176,17 @@ func (s *SubmissionSession) Data(r io.Reader) error {
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
-	// DKIM-sign the message if the sender's domain has keys configured.
 	senderDomain := domainOf(s.from)
 	raw = s.signDKIM(ctx, raw, senderDomain)
 
 	msgID := extractMsgID(raw)
 
-	// Queue each recipient for delivery.
-	// For local recipients we could deliver directly, but queuing is simpler and
-	// provides a consistent audit trail.
 	dom, err := s.deps.DB.GetDomain(ctx, senderDomain)
 	var domainID int64
 	if err == nil && dom != nil {
 		domainID = dom.ID
 	}
 
-	// Encrypt raw for queue storage using a global (non-user) key.
 	queueKey, err := s.deps.Crypt.DeriveKeyGlobal("queue")
 	if err != nil {
 		return fmt.Errorf("queue key: %w", err)
@@ -180,8 +205,10 @@ func (s *SubmissionSession) Data(r io.Reader) error {
 		log.Printf("[smtp/submission] queued %s → %s", s.from, rcpt)
 	}
 
-	// Also save a copy in sender's Sent folder.
-	s.saveSentCopy(ctx, raw)
+	// Save a Sent copy only for regular (non-relay) authenticated users.
+	if s.user != nil && !s.user.IsRelay {
+		s.saveSentCopy(ctx, raw)
+	}
 
 	return nil
 }
@@ -189,6 +216,7 @@ func (s *SubmissionSession) Data(r io.Reader) error {
 func (s *SubmissionSession) Reset() {
 	s.from = ""
 	s.rcpts = s.rcpts[:0]
+	s.ipRelayMode = false
 }
 
 func (s *SubmissionSession) Logout() error { return nil }