add reject from origin domain feature (#375)

Add a new feature to be able to reject email *from* specific domains.

Co-authored-by: Cyril DUPONT <cyd@9bis.com>

pkg/server/smtp/handler.go

@@ -106,7 +106,7 @@ type Session struct {
 	sendError    error               // Last network send error.
 	state        State               // Session state machine.
 	reader       *bufio.Reader       // Buffered reading for TCP conn.
-	from         string              // Sender from MAIL command.
+	from         *policy.Origin      // Sender from MAIL command.
 	recipients   []*policy.Recipient // Recipients from RCPT commands.
 	logger       zerolog.Logger      // Session specific logger.
 	debug        bool                // Print network traffic to stdout.
@@ -384,7 +384,10 @@ func (s *Session) readyHandler(cmd string, arg string) {
 			return
 		}
 		from := m[1]
+		s.logger.Debug().Msgf("Mail sender is %v", from)
 		localpart, domain, err := policy.ParseEmailAddress(from)
+		s.logger.Debug().Msgf("Origin domain is %v", domain)
+
 		if from != "" && err != nil {
 			s.send("501 Bad sender address syntax")
 			s.logger.Warn().Msgf("Bad address as MAIL arg: %q, %s", from, err)
@@ -424,7 +427,19 @@ func (s *Session) readyHandler(cmd string, arg string) {
 
 		if extResult == nil || *extResult {
 			// Permitted by extension, or none had an opinion.
-			s.from = from
+			origin, err := s.addrPolicy.ParseOrigin(from)
+			if err != nil {
+				s.send("501 Bad origin address syntax")
+				s.logger.Warn().Str("from", from).Err(err).Msg("Bad address as MAIL arg")
+				return
+			}
+			s.from = origin
+			if !s.from.ShouldAccept() {
+				s.send("501 Unauthorized domain")
+				s.logger.Warn().Msgf("Bad domain sender %s", domain)
+				return
+			}
+
 			s.logger.Info().Msgf("Mail from: %v", from)
 			s.send(fmt.Sprintf("250 Roger, accepting mail from <%v>", from))
 			s.enterState(MAIL)
@@ -601,6 +616,7 @@ func (s *Session) readLine() (line string, err error) {
 
 func (s *Session) parseCmd(line string) (cmd string, arg string, ok bool) {
 	line = strings.TrimRight(line, "\r\n")
+	s.logger.Debug().Msgf("Line received: %v", line)
 
 	// Find length of command or entire line.
 	hasArg := true
@@ -649,7 +665,7 @@ func (s *Session) parseArgs(arg string) (args map[string]string, ok bool) {
 
 func (s *Session) reset() {
 	s.enterState(READY)
-	s.from = ""
+	s.from = nil
 	s.recipients = nil
 }