Fix the broken SMTP sending

examples/main.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"fmt"
+	"net"
+
+	"net/textproto"
+
+	"git.ailur.dev/ailur/smtp"
+)
+
+// DatabaseBackend is a smtp.DatabaseBackend implementation that always returns true for CheckUser and prints the mail data to stdout.
+var DatabaseBackend = smtp.DatabaseBackend{
+	CheckUser: func(address *smtp.Address) (bool, error) {
+		return true, nil
+	},
+	WriteMail: func(mail *smtp.Mail) error {
+		fmt.Println(string(mail.Data))
+		return nil
+	},
+}
+
+// AuthenticationBackend is a smtp.AuthenticationBackend implementation that always returns a fixed address for Authenticate.
+var AuthenticationBackend = smtp.AuthenticationBackend{
+	Authenticate: func(initial string, conn *textproto.Conn) (smtp.CheckAddress, error) {
+		return func(address *smtp.Address) (bool, error) {
+			return true, nil
+		}, nil
+	},
+}
+
+func main() {
+	go func() {
+		// Serve on the server-to-server port
+		listener, err := net.Listen("tcp", ":25")
+		if err != nil {
+			panic(err)
+		}
+		receiver := smtp.NewReceiver(listener, "localhost", []string{"localhost", "127.0.0.1", "0.0.0.0", "example.org", "192.168.1.253"}, false, DatabaseBackend, AuthenticationBackend, nil)
+		err = receiver.Serve()
+		panic(err)
+	}()
+	go func() {
+		// Serve on the submission port
+		listener, err := net.Listen("tcp", ":587")
+		if err != nil {
+			panic(err)
+		}
+		receiver := smtp.NewReceiver(listener, "localhost", []string{"localhost", "127.0.0.1", "0.0.0.0", "cta.social"}, false, DatabaseBackend, AuthenticationBackend, nil)
+		err = receiver.Serve()
+		panic(err)
+	}()
+
+	// Block forever
+	select {}
+}

go.mod

@@ -1,4 +1,4 @@
-module smtp
+module git.ailur.dev/ailur/smtp
 
 go 1.23
 

smtp.go

@@ -7,12 +7,12 @@ import (
 	"net"
 	"strconv"
 	"strings"
+	"time"
 
 	"crypto/tls"
 	"net/textproto"
 
 	"git.ailur.dev/ailur/spf"
-	"github.com/google/uuid"
 )
 
 var (
@@ -22,7 +22,7 @@ var (
 		"250-SMTPUTF8",
 		"250 BINARYMIME",
 	}
-	queue = make(map[uuid.UUID]*MailQueueItem)
+	queue = make(map[time.Time]*MailQueueItem)
 )
 
 // MailQueueItem is a struct that represents an item in the mail queue
@@ -33,7 +33,7 @@ type MailQueueItem struct {
 }
 
 // ViewMailQueue returns the current mail queue
-func ViewMailQueue() map[uuid.UUID]*MailQueueItem {
+func ViewMailQueue() map[time.Time]*MailQueueItem {
 	return queue
 }
 
@@ -53,14 +53,17 @@ type Mail struct {
 // DatabaseBackend is a struct that represents a database backend
 type DatabaseBackend struct {
 	CheckUser func(*Address) (bool, error)
-	WriteMail func(*Mail) (uuid.UUID, error)
+	WriteMail func(*Mail) error
 }
 
 // AuthenticationBackend is a struct that represents an authentication backend
 type AuthenticationBackend struct {
-	Authenticate func(string) (*Address, error)
+	Authenticate        func(initial string, conn *textproto.Conn) (CheckAddress, error)
+	SupportedMechanisms []string
 }
 
+type CheckAddress func(*Address) (bool, error)
+
 func readMultilineCodeResponse(conn *textproto.Conn) (int, string, error) {
 	var lines strings.Builder
 	for {
@@ -83,7 +86,7 @@ func readMultilineCodeResponse(conn *textproto.Conn) (int, string, error) {
 }
 
 func systemError(err error, receiver *Address, database DatabaseBackend) {
-	_, _ = database.WriteMail(&Mail{
+	_ = database.WriteMail(&Mail{
 		From: &Address{
 			Name:    "EMail System",
 			Address: "system",
@@ -93,7 +96,7 @@ func systemError(err error, receiver *Address, database DatabaseBackend) {
 	})
 }
 
-func sendEmail(args SenderArgs, mail *Mail, database DatabaseBackend, queueID uuid.UUID) {
+func sendEmail(args SenderArgs, mail *Mail, database DatabaseBackend, queueID time.Time) {
 	mxs, err := net.LookupMX(mail.To[0].Address)
 	if err != nil {
 		systemError(err, queue[queueID].From, database)
@@ -147,7 +150,7 @@ func speakMultiLine(conn *textproto.Conn, lines []string) error {
 type Receiver struct {
 	underlyingListener net.Listener
 	hostname           string
-	ownedDomains       map[string]any
+	ownedDomains       map[string]struct{}
 	enforceTLS         bool
 	tlsConfig          *tls.Config
 	database           DatabaseBackend
@@ -156,9 +159,9 @@ type Receiver struct {
 
 // NewReceiver creates a new Receiver
 func NewReceiver(conn net.Listener, hostname string, ownedDomains []string, enforceTLS bool, database DatabaseBackend, authentication AuthenticationBackend, tlsConfig *tls.Config) *Receiver {
-	var ownedDomainsMap = make(map[string]any)
+	var ownedDomainsMap = make(map[string]struct{})
 	for _, domain := range ownedDomains {
-		ownedDomainsMap[domain] = nil
+		ownedDomainsMap[domain] = struct{}{}
 	}
 	return &Receiver{
 		underlyingListener: conn,
@@ -191,7 +194,7 @@ func (fr *Receiver) Serve() error {
 func (fr *Receiver) handleConnection(conn net.Conn) {
 	var state struct {
 		HELO bool
-		AUTH *Address
+		AUTH CheckAddress
 		TLS  bool
 		FROM *Address
 		RCPT []*Address
@@ -209,8 +212,6 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 		return
 	}
 
-	fmt.Println("Connection from", conn.RemoteAddr().String())
-
 	for {
 		line, err := textProto.ReadLine()
 		if err != nil {
@@ -281,6 +282,9 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 				if fr.enforceTLS {
 					capabilities = append(capabilities, "250-REQUIRETLS")
 				}
+				if fr.auth.SupportedMechanisms != nil {
+					capabilities = append(capabilities, "250-AUTH "+strings.Join(fr.auth.SupportedMechanisms, " "))
+				}
 				capabilities = append(capabilities, defaultCapabilities...)
 				state.HELO = true
 				err = speakMultiLine(textProto, capabilities)
@@ -320,14 +324,14 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 				}
 				continue
 			} else {
-				address, err := fr.auth.Authenticate(line)
+				checkAddress, err := fr.auth.Authenticate(strings.TrimPrefix(line, "AUTH "), textProto)
 				if err != nil {
-					_ = textProto.PrintfLine("421 4.7.0 Temporary server error")
+					_ = textProto.PrintfLine(err.Error())
 					_ = conn.Close()
 					return
 				}
 
-				if address == nil {
+				if checkAddress == nil {
 					err = textProto.PrintfLine("535 5.7.8 Authentication failed")
 					if err != nil {
 						_ = textProto.PrintfLine("421 4.7.0 Temporary server error")
@@ -335,7 +339,7 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 						return
 					}
 				} else {
-					state.AUTH = address
+					state.AUTH = checkAddress
 					err = textProto.PrintfLine("235 2.7.0 Authentication successful")
 					if err != nil {
 						_ = textProto.PrintfLine("421 4.7.0 Temporary server error")
@@ -410,7 +414,14 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 					continue
 				}
 
-				if *address != *state.AUTH {
+				ok, err := state.AUTH(address)
+				if err != nil {
+					_ = textProto.PrintfLine("421 4.7.0 Temporary server error")
+					_ = conn.Close()
+					return
+				}
+
+				if !ok {
 					err = textProto.PrintfLine("535 5.7.8 Authenticated wrong user")
 					if err != nil {
 						_ = textProto.PrintfLine("421 4.7.0 Temporary server error")
@@ -557,7 +568,7 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 			}
 
 			if !isSubmission {
-				_, err := fr.database.WriteMail(mail)
+				err := fr.database.WriteMail(mail)
 				if err != nil {
 					_ = textProto.PrintfLine(err.Error())
 					_ = conn.Close()
@@ -571,7 +582,7 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 					return
 				}
 			} else {
-				queueID := uuid.New()
+				queueID := time.Now()
 
 				queue[queueID] = &MailQueueItem{
 					From: state.FROM,
@@ -579,7 +590,6 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 					Host: strings.Split(conn.RemoteAddr().String(), ":")[0],
 				}
 				go sendEmail(SenderArgs{
-					Hostname:   fr.hostname,
 					EnforceTLS: fr.enforceTLS,
 				}, mail, fr.database, queueID)
 
@@ -608,7 +618,6 @@ func (fr *Receiver) handleConnection(conn net.Conn) {
 
 // SenderArgs is a struct that represents the arguments for the Sender
 type SenderArgs struct {
-	Hostname   string
 	EnforceTLS bool
 }
 
@@ -639,7 +648,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 		return errors.New("unexpected greeting - " + line)
 	}
 
-	err = textConn.PrintfLine("EHLO %s", args.Hostname)
+	err = textConn.PrintfLine("EHLO %s", mxHost)
 	if err != nil {
 		return err
 	}
@@ -673,16 +682,11 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 			InsecureSkipVerify: false,
 		})
 
-		err = tlsConn.Handshake()
-		if err != nil {
-			return err
-		}
-
 		textConn = textproto.NewConn(tlsConn)
 
 		// Just use HELO, no point using EHLO when we already have all the capabilities
 		// This also gets us out of using readMultilineCodeResponse
-		err = textConn.PrintfLine("HELO %s", args.Hostname)
+		err = textConn.PrintfLine("HELO %s", mxHost)
 		if err != nil {
 			return err
 		}
@@ -705,10 +709,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		// For some reason the EHLO stuff ends up here
-		fmt.Println("5")
 		return err
 	}
 
@@ -723,9 +724,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 		}
 
 		code, line, err = textConn.ReadCodeLine(0)
-		fmt.Println(code, line, err)
 		if err != nil {
-			fmt.Println("6")
 			return err
 		}
 
@@ -740,9 +739,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		fmt.Println("7")
 		return err
 	}
 
@@ -762,9 +759,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		fmt.Println("8")
 		return err
 	}
 
@@ -778,9 +773,7 @@ func Send(args SenderArgs, mail *Mail, conn net.Conn, mxHost string) (err error)
 	}
 
 	code, line, err = textConn.ReadCodeLine(0)
-	fmt.Println(code, line, err)
 	if err != nil {
-		fmt.Println("9")
 		return err
 	}