Implement MT-PRIORITY (RFC 6710)

Author: qugu2427

client.go

@@ -544,6 +544,12 @@ func (c *Client) Rcpt(to string, opts *RcptOptions) error {
 		}
 		sb.WriteString(arg)
 	}
+	if _, ok := c.ext["MT-PRIORITY"]; ok && opts != nil && opts.MTPriority != nil {
+		if *opts.MTPriority < -9 || *opts.MTPriority > 9 {
+			return errors.New("smtp: MT-PRIORITY must be between -9 and 9")
+		}
+		sb.WriteString(fmt.Sprintf(" MT-PRIORITY=%d", *opts.MTPriority))
+	}
 	if _, _, err := c.cmd(25, "%s", sb.String()); err != nil {
 		return err
 	}

client_test.go

@@ -1115,3 +1115,36 @@ func TestClientDELIVERBY(t *testing.T) {
 		t.Errorf("wrote %q; want %q", actualcmds, client)
 	}
 }
+
+var mtPriorityServer = `220 hello world
+250 ok
+`
+
+var mtPriorityClient = `RCPT TO:<root@nsa.gov> MT-PRIORITY=6
+`
+
+func TestClientMTPRIORITY(t *testing.T) {
+	server := strings.Join(strings.Split(mtPriorityServer, "\n"), "\r\n")
+	client := strings.Join(strings.Split(mtPriorityClient, "\n"), "\r\n")
+
+	var wrote bytes.Buffer
+	var fake faker
+	fake.ReadWriter = struct {
+		io.Reader
+		io.Writer
+	}{
+		strings.NewReader(server),
+		&wrote,
+	}
+	c := NewClient(fake)
+	c.didHello = true
+	c.ext = map[string]string{"MT-PRIORITY": ""}
+	priority := 6
+	c.Rcpt("root@nsa.gov", &RcptOptions{
+		MTPriority: &priority,
+	})
+	c.Close()
+	if actualcmds := wrote.String(); client != actualcmds {
+		t.Errorf("wrote %q; want %q", actualcmds, client)
+	}
+}

conn.go

@@ -301,6 +301,13 @@ func (c *Conn) handleGreet(enhanced bool, arg string) {
 			caps = append(caps, fmt.Sprintf("DELIVERBY %d", int(c.server.MinimumDeliverByTime.Seconds())))
 		}
 	}
+	if c.server.EnableMTPRIORITY {
+		if c.server.MtPriorityProfile == PriorityUnspecified {
+			caps = append(caps, "MT-PRIORITY")
+		} else {
+			caps = append(caps, fmt.Sprintf("MT-PRIORITY %s", c.server.MtPriorityProfile))
+		}
+	}
 
 	args := []string{"Hello " + domain}
 	args = append(args, caps...)
@@ -755,6 +762,21 @@ func (c *Conn) handleRcpt(arg string) {
 				return
 			}
 			opts.DeliverBy = deliverBy
+		case "MT-PRIORITY":
+			if !c.server.EnableMTPRIORITY {
+				c.writeResponse(504, EnhancedCode{5, 5, 4}, "MT-PRIORITY is not implemented")
+				return
+			}
+			mtPriority, err := strconv.Atoi(value)
+			if err != nil {
+				c.writeResponse(501, EnhancedCode{5, 5, 4}, "Malformed MT-PRIORITY parameter value")
+				return
+			}
+			if mtPriority < -9 || mtPriority > 9 {
+				c.writeResponse(501, EnhancedCode{5, 5, 4}, "MT-PRIORITY is outside valid range")
+				return
+			}
+			opts.MTPriority = &mtPriority
 		default:
 			c.writeResponse(500, EnhancedCode{5, 5, 4}, "Unknown RCPT TO argument")
 			return

server.go

@@ -70,6 +70,15 @@ type Server struct {
 	// Only use if DELIVERBY is enabled.
 	MinimumDeliverByTime time.Duration
 
+	// Advertise MT-PRIORITY (RFC 6710) capability.
+	// Should only be used if backend supports it.
+	EnableMTPRIORITY bool
+	// The priority profile mapping as defined
+	// in RFC 6710 section 10.2.
+	//
+	// Default value of NONE to advertise no specific profile.
+	MtPriorityProfile PriorityProfile
+
 	// The server backend.
 	Backend Backend
 

server_test.go

@@ -1650,3 +1650,65 @@ func TestServerDELIVERBY(t *testing.T) {
 		t.Fatal("Incorrect BY parameter value:", fmt.Sprintf("expected %#v, got %#v", expectedDeliverByOpts, deliverByOpts))
 	}
 }
+
+func TestServerMTPRIORITY(t *testing.T) {
+	be, s, c, scanner, caps := testServerEhlo(t,
+		func(s *smtp.Server) {
+			s.EnableMTPRIORITY = true
+		})
+	defer s.Close()
+	defer c.Close()
+
+	if _, ok := caps["MT-PRIORITY"]; !ok {
+		t.Fatal("Missing capability: MT-PRIORITY")
+	}
+
+	io.WriteString(c, "MAIL FROM:<root@nsa.gov>\r\n")
+	scanner.Scan()
+
+	malformedMsgs := []string{
+		"RCPT TO:<root@gchq.gov.uk> MT-PRIORITY=",
+		"RCPT TO:<root@gchq.gov.uk> MT-PRIORITY=foo",
+		"RCPT TO:<root@gchq.gov.uk> MT-PRIORITY=-10",
+		"RCPT TO:<root@gchq.gov.uk> MT-PRIORITY=10",
+	}
+
+	for _, msg := range malformedMsgs {
+		io.WriteString(c, msg+"\r\n")
+		scanner.Scan()
+		if !strings.HasPrefix(scanner.Text(), "501 5.5.4") {
+			t.Fatal("Unexpected res on malformed MT-PRIORITY parameter value:", scanner.Text())
+		}
+	}
+
+	expectedPriority := -2
+
+	io.WriteString(c, fmt.Sprintf("RCPT TO:<root@gchq.gov.uk> MT-PRIORITY=%d\r\n", expectedPriority))
+	scanner.Scan()
+
+	if !strings.HasPrefix(scanner.Text(), "250 ") {
+		t.Fatal("Invalid MT-PRIORITY parameter value:", scanner.Text())
+	}
+
+	// complete the transaction
+	io.WriteString(c, "DATA\r\n")
+	scanner.Scan()
+	io.WriteString(c, "Hey <3\r\n")
+	io.WriteString(c, ".\r\n")
+	scanner.Scan()
+
+	opts := be.anonmsgs[0].RcptOpts
+	if opts == nil || len(opts) != 1 {
+		t.Fatal("Invalid number of recipients:", opts)
+	}
+
+	priority := opts[0].MTPriority
+
+	if priority == nil {
+		t.Fatal("MtPriority is nil:", opts)
+	}
+
+	if *priority != expectedPriority {
+		t.Fatal("Incorrect MtPriority parameter value:", fmt.Sprintf("expected %d, got %d", expectedPriority, *priority))
+	}
+}

smtp.go

@@ -11,6 +11,7 @@
 //   - STARTTLS (RFC 3207)
 //   - DSN (RFC 3461, RFC 6533)
 //   - SMTPUTF8 (RFC 6531)
+//   - MT-PRIORITY (RFC 6710)
 //   - RRVS (RFC 7293)
 //   - REQUIRETLS (RFC 8689)
 //
@@ -101,6 +102,15 @@ type DeliverByOptions struct {
 	Trace bool
 }
 
+type PriorityProfile string
+
+const (
+	PriorityUnspecified PriorityProfile = ""
+	PriorityMIXER       PriorityProfile = "MIXER"
+	PrioritySTANAG4406  PriorityProfile = "STANAG4406"
+	PriorityNSEP        PriorityProfile = "NSEP"
+)
+
 // RcptOptions contains parameters for the RCPT command.
 type RcptOptions struct {
 	// Value of NOTIFY= argument, NEVER or a combination of either of
@@ -117,4 +127,7 @@ type RcptOptions struct {
 
 	// Value of BY= argument or nil if unset.
 	DeliverBy *DeliverByOptions
+
+	// Value of MT-PRIORITY= or nil if unset.
+	MTPriority *int
 }