XCLIENT support.

protocol.go

@@ -8,7 +8,9 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"net"
 	"net/textproto"
+	"strconv"
 	"strings"
 	"time"
 )
@@ -84,6 +86,10 @@ func (session *session) handle(line string) {
 		session.handleAUTH(cmd)
 		return
 
+	case "XCLIENT":
+		session.handleXCLIENT(cmd)
+		return
+
 	}
 
 	session.reply(502, "Unsupported command.")
@@ -111,6 +117,7 @@ func (session *session) handleHELO(cmd command) {
 	}
 
 	session.peer.HeloName = cmd.fields[1]
+	session.peer.Protocol = SMTP
 	session.reply(250, "Go ahead")
 
 	return
@@ -138,6 +145,7 @@ func (session *session) handleEHLO(cmd command) {
 	}
 
 	session.peer.HeloName = cmd.fields[1]
+	session.peer.Protocol = ESMTP
 
 	extensions := session.extensions()
 
@@ -179,8 +187,10 @@ func (session *session) handleMAIL(cmd command) {
 
 	if session.server.SenderChecker != nil {
 		err = session.server.SenderChecker(session.peer, addr)
-		session.error(err)
+		if err != nil {
-		return
+			session.error(err)
+			return
+		}
 	}
 
 	session.envelope = &Envelope{
@@ -214,8 +224,10 @@ func (session *session) handleRCPT(cmd command) {
 
 	if session.server.RecipientChecker != nil {
 		err = session.server.RecipientChecker(session.peer, addr)
-		session.error(err)
+		if err != nil {
-		return
+			session.error(err)
+			return
+		}
 	}
 
 	session.envelope.Recipients = append(session.envelope.Recipients, addr)
@@ -445,3 +457,102 @@ func (session *session) handleAUTH(cmd command) {
 	session.reply(235, "OK, you are now authenticated")
 
 }
+
+func (session *session) handleXCLIENT(cmd command) {
+
+	if !session.server.EnableXCLIENT {
+		session.reply(550, "XCLIENT not enabled")
+		return
+	}
+
+	var (
+		newHeloName          = ""
+		newAddr     net.IP   = nil
+		newTCPPort  uint64   = 0
+		newUsername          = ""
+		newProto    Protocol = ""
+	)
+
+	for _, item := range cmd.fields[1:] {
+
+		parts := strings.Split(item, "=")
+
+		if len(parts) != 2 {
+			session.reply(502, "Couldn't decode the command.")
+			return
+		}
+
+		name := parts[0]
+		value := parts[1]
+
+		switch name {
+
+		case "NAME":
+			// Unused in smtpd package
+			continue
+
+		case "HELO":
+			newHeloName = value
+			continue
+
+		case "ADDR":
+			newAddr = net.ParseIP(value)
+			continue
+
+		case "PORT":
+			var err error
+			newTCPPort, err = strconv.ParseUint(value, 10, 16)
+			if err != nil {
+				session.reply(502, "Couldn't decode the command.")
+				return
+			}
+			continue
+
+		case "LOGIN":
+			newUsername = value
+			continue
+
+		case "PROTO":
+			if value == "SMTP" {
+				newProto = SMTP
+			} else if value == "ESMTP" {
+				newProto = ESMTP
+			}
+			continue
+
+		default:
+			session.reply(502, "Couldn't decode the command.")
+			return
+		}
+
+	}
+
+	tcpAddr, ok := session.peer.Addr.(*net.TCPAddr)
+	if !ok {
+		session.reply(502, "Unsupported network connection")
+		return
+	}
+
+	if newHeloName != "" {
+		session.peer.HeloName = newHeloName
+	}
+
+	if newAddr != nil {
+		tcpAddr.IP = newAddr
+	}
+
+	if newTCPPort != 0 {
+		tcpAddr.Port = int(newTCPPort)
+	}
+
+	if newUsername != "" {
+		session.peer.Username = newUsername
+	}
+
+	if newProto != "" {
+		session.peer.Protocol = newProto
+	}
+
+	session.welcome()
+
+}

smtpd.go

@@ -42,15 +42,26 @@ type Server struct {
 	// Can be left empty for no authentication support.
 	Authenticator func(peer Peer, username, password string) error
 
+	EnableXCLIENT bool // Enable XCLIENT support (default: false)
+
 	TLSConfig *tls.Config // Enable STARTTLS support.
 	ForceTLS  bool        // Force STARTTLS usage.
 }
 
+// Protocol represents the protocol used in the SMTP session
+type Protocol string
+
+const (
+	SMTP  Protocol = "SMTP"
+	ESMTP          = "ESMTP"
+)
+
 // Peer represents the client connecting to the server
 type Peer struct {
 	HeloName string   // Server name used in HELO/EHLO command
 	Username string   // Username from authentication, if authenticated
 	Password string   // Password from authentication, if authenticated
+	Protocol Protocol // Protocol used, SMTP or ESMTP
 	Addr     net.Addr // Network address
 }
 
@@ -294,6 +305,10 @@ func (session *session) extensions() []string {
 		"PIPELINING",
 	}
 
+	if session.server.EnableXCLIENT {
+		extensions = append(extensions, "XCLIENT")
+	}
+
 	if session.server.TLSConfig != nil && !session.tls {
 		extensions = append(extensions, "STARTTLS")
 	}

smtpd_test.go

@@ -1058,3 +1058,90 @@ func TestLongLine(t *testing.T) {
 	}
 
 }
+
+func TestXCLIENT(t *testing.T) {
+
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+
+	defer ln.Close()
+
+	server := &smtpd.Server{
+		EnableXCLIENT: true,
+		SenderChecker: func(peer smtpd.Peer, addr string) error {
+			if peer.HeloName != "new.example.net" {
+				t.Fatalf("Didn't override HELO name: %v", peer.HeloName)
+			}
+			if peer.Addr.String() != "42.42.42.42:4242" {
+				t.Fatalf("Didn't override IP/Port: %v", peer.Addr)
+			}
+			if peer.Username != "newusername" {
+				t.Fatalf("Didn't override username: %v", peer.Username)
+			}
+			if peer.Protocol != smtpd.SMTP {
+				t.Fatalf("Didn't override protocol: %v", peer.Protocol)
+			}
+			return nil
+		},
+	}
+
+	go func() {
+		server.Serve(ln)
+	}()
+
+	c, err := smtp.Dial(ln.Addr().String())
+	if err != nil {
+		t.Fatalf("Dial failed: %v", err)
+	}
+
+	if supported, _ := c.Extension("XCLIENT"); !supported {
+		t.Fatal("XCLIENT not supported")
+	}
+
+	id, err := c.Text.Cmd("XCLIENT NAME=ignored ADDR=42.42.42.42 PORT=4242 PROTO=SMTP HELO=new.example.net LOGIN=newusername")
+	if err != nil {
+		t.Fatalf("Cmd failed: %v", err)
+	}
+
+	c.Text.StartResponse(id)
+	_, _, err = c.Text.ReadResponse(220)
+	c.Text.EndResponse(id)
+
+	if err != nil {
+		t.Fatalf("XCLIENT failed: %v", err)
+	}
+
+	if err := c.Mail("sender@example.org"); err != nil {
+		t.Fatalf("Mail failed: %v", err)
+	}
+
+	if err := c.Rcpt("recipient@example.net"); err != nil {
+		t.Fatalf("Rcpt failed: %v", err)
+	}
+
+	if err := c.Rcpt("recipient2@example.net"); err != nil {
+		t.Fatalf("Rcpt2 failed: %v", err)
+	}
+
+	wc, err := c.Data()
+	if err != nil {
+		t.Fatalf("Data failed: %v", err)
+	}
+
+	_, err = fmt.Fprintf(wc, "This is the email body")
+	if err != nil {
+		t.Fatalf("Data body failed: %v", err)
+	}
+
+	err = wc.Close()
+	if err != nil {
+		t.Fatalf("Data close failed: %v", err)
+	}
+
+	if err := c.Quit(); err != nil {
+		t.Fatalf("Quit failed: %v", err)
+	}
+
+}