send emails

smtp/msa.go

@@ -10,14 +10,15 @@ import (
 	"gitlab.com/etke.cc/go/logger"
 )
 
-type backend struct {
+// msa is mail submission agent
+type msa struct {
 	log    *logger.Logger
 	domain string
 	client Client
 }
 
-func (b *backend) newSession() *session {
-	return &session{
+func (b *msa) newSession() *msasession {
+	return &msasession{
 		ctx:    sentry.SetHubOnContext(context.Background(), sentry.CurrentHub().Clone()),
 		log:    b.log,
 		domain: b.domain,
@@ -25,28 +26,30 @@ func (b *backend) newSession() *session {
 	}
 }
 
-func (b *backend) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
+func (b *msa) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
 	return nil, smtp.ErrAuthUnsupported
 }
 
-func (b *backend) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
+func (b *msa) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
 	return b.newSession(), nil
 }
 
 func Start(domain, port, loglevel string, maxSize int, client Client) error {
 	log := logger.New("smtp.", loglevel)
-	be := &backend{
+	sender := NewMTA(loglevel)
+	receiver := &msa{
 		log:    log,
 		domain: domain,
 		client: client,
 	}
-	s := smtp.NewServer(be)
+	receiver.client.SetMTA(sender)
+	s := smtp.NewServer(receiver)
 	s.Addr = ":" + port
 	s.Domain = domain
-	s.AuthDisabled = true
 	s.ReadTimeout = 10 * time.Second
 	s.WriteTimeout = 10 * time.Second
 	s.MaxMessageBytes = maxSize * 1024 * 1024
+	s.AllowInsecureAuth = true
 	if log.GetLevel() == "DEBUG" || log.GetLevel() == "TRACE" {
 		s.Debug = os.Stdout
 	}

smtp/msasession.go

@@ -12,7 +12,7 @@ import (
 	"gitlab.com/etke.cc/postmoogle/utils"
 )
 
-type session struct {
+type msasession struct {
 	log    *logger.Logger
 	domain string
 	client Client
@@ -22,14 +22,14 @@ type session struct {
 	from string
 }
 
-func (s *session) Mail(from string, opts smtp.MailOptions) error {
+func (s *msasession) Mail(from string, opts smtp.MailOptions) error {
 	sentry.GetHubFromContext(s.ctx).Scope().SetTag("from", from)
 	s.from = from
 	s.log.Debug("mail from %s, options: %+v", from, opts)
 	return nil
 }
 
-func (s *session) Rcpt(to string) error {
+func (s *msasession) Rcpt(to string) error {
 	sentry.GetHubFromContext(s.ctx).Scope().SetTag("to", to)
 
 	if utils.Hostname(to) != s.domain {
@@ -48,7 +48,7 @@ func (s *session) Rcpt(to string) error {
 	return nil
 }
 
-func (s *session) parseAttachments(parts []*enmime.Part) []*utils.File {
+func (s *msasession) parseAttachments(parts []*enmime.Part) []*utils.File {
 	files := make([]*utils.File, 0, len(parts))
 	for _, attachment := range parts {
 		for _, err := range attachment.Errors {
@@ -61,7 +61,7 @@ func (s *session) parseAttachments(parts []*enmime.Part) []*utils.File {
 	return files
 }
 
-func (s *session) Data(r io.Reader) error {
+func (s *msasession) Data(r io.Reader) error {
 	parser := enmime.NewParser()
 	eml, err := parser.ReadEnvelope(r)
 	if err != nil {
@@ -84,11 +84,11 @@ func (s *session) Data(r io.Reader) error {
 		eml.HTML,
 		files)
 
-	return s.client.Send(s.ctx, email)
+	return s.client.Send2Matrix(s.ctx, email)
 }
 
-func (s *session) Reset() {}
+func (s *msasession) Reset() {}
 
-func (s *session) Logout() error {
+func (s *msasession) Logout() error {
 	return nil
 }

smtp/mta.go

@@ -0,0 +1,116 @@
+package smtp
+
+import (
+	"context"
+	"crypto/tls"
+	"fmt"
+	"io"
+	"net"
+	"net/smtp"
+	"strings"
+
+	"gitlab.com/etke.cc/go/logger"
+	"maunium.net/go/mautrix/id"
+
+	"gitlab.com/etke.cc/postmoogle/utils"
+)
+
+// Client interface to send emails into matrix
+type Client interface {
+	GetMapping(string) (id.RoomID, bool)
+	Send2Matrix(ctx context.Context, email *utils.Email) error
+	SetMTA(mta utils.MTA)
+}
+
+// mta is Mail Transfer Agent
+type mta struct {
+	log *logger.Logger
+}
+
+func NewMTA(loglevel string) utils.MTA {
+	return &mta{
+		log: logger.New("smtp/mta.", loglevel),
+	}
+}
+
+func (m *mta) Send(from, to, data string) error {
+	m.log.Debug("Sending email from %s to %s", from, to)
+	conn, err := m.connect(from, to)
+	if err != nil {
+		m.log.Error("cannot connect to SMTP server of %s: %v", to, err)
+		return err
+	}
+	defer conn.Close()
+	err = conn.Mail(from)
+	if err != nil {
+		m.log.Error("cannot call MAIL command: %v", err)
+		return err
+	}
+	err = conn.Rcpt(to)
+	if err != nil {
+		m.log.Error("cannot send RCPT command: %v", err)
+		return err
+	}
+
+	var w io.WriteCloser
+	w, err = conn.Data()
+	if err != nil {
+		m.log.Error("cannot send DATA command: %v", err)
+		return err
+	}
+	defer w.Close()
+	m.log.Debug("sending DATA:\n%s", data)
+	_, err = strings.NewReader(data).WriteTo(w)
+	if err != nil {
+		m.log.Debug("cannot write DATA: %v", err)
+		return err
+	}
+
+	m.log.Debug("email has been sent")
+	return nil
+}
+
+func (m *mta) tryServer(localname, mxhost string) *smtp.Client {
+	m.log.Debug("trying SMTP connection to %s", mxhost)
+	conn, err := smtp.Dial(mxhost + ":smtp")
+	if err != nil {
+		m.log.Warn("cannot connect to the %s: %v", mxhost, err)
+		return nil
+	}
+	err = conn.Hello(localname)
+	if err != nil {
+		m.log.Warn("cannot call HELLO command of the %s: %v", mxhost, err)
+		return nil
+	}
+	if ok, _ := conn.Extension("STARTTLS"); ok {
+		m.log.Debug("%s supports STARTTLS", mxhost)
+		config := &tls.Config{ServerName: mxhost}
+		err = conn.StartTLS(config)
+		if err != nil {
+			m.log.Warn("STARTTLS connection to the %s failed: %v", mxhost, err)
+		}
+	}
+
+	return conn
+}
+
+func (m *mta) connect(from, to string) (*smtp.Client, error) {
+	localname := strings.SplitN(from, "@", 2)[1]
+	hostname := strings.SplitN(to, "@", 2)[1]
+
+	m.log.Debug("performing MX lookup of %s", hostname)
+	mxs, err := net.LookupMX(hostname)
+	if err != nil {
+		m.log.Error("cannot perform MX lookup: %v", err)
+		return nil, err
+	}
+
+	for _, mx := range mxs {
+		client := m.tryServer(localname, mx.Host)
+		if client != nil {
+			return client, nil
+		}
+	}
+
+	return nil, fmt.Errorf("target SMTP server not found")
+}

smtp/smtp.go

@@ -1,15 +0,0 @@
-package smtp
-
-import (
-	"context"
-
-	"maunium.net/go/mautrix/id"
-
-	"gitlab.com/etke.cc/postmoogle/utils"
-)
-
-// Client interface to send emails
-type Client interface {
-	GetMapping(string) (id.RoomID, bool)
-	Send(ctx context.Context, email *utils.Email) error
-}