adjust auto-retry, fix banned response code, rewrite email composing to enmime, add more logs

bot/email.go

@@ -39,7 +39,7 @@ func (b *Bot) SetSendmail(sendmail func(string, string, string) error) {
 func (b *Bot) Sendmail(eventID id.EventID, from, to, data string) (bool, error) {
 	err := b.sendmail(from, to, data)
 	if err != nil {
-		if strings.HasPrefix(err.Error(), "45") {
+		if strings.HasPrefix(err.Error(), "4") {
 			b.log.Debug("email %s (from=%s to=%s) was added to the queue: %v", eventID, from, to, err)
 			return true, b.enqueueEmail(eventID.String(), from, to, data)
 		}

smtp/server.go

@@ -2,7 +2,6 @@ package smtp
 
 import (
 	"context"
-	"errors"
 	"io"
 	"strings"
 
@@ -14,6 +13,13 @@ import (
 	"gitlab.com/etke.cc/postmoogle/utils"
 )
 
+// ErrBanned returned to banned hosts
+var ErrBanned = &smtp.SMTPError{
+	Code:         554,
+	EnhancedCode: smtp.EnhancedCode{5, 5, 4},
+	Message:      "please, don't bother me anymore, kupo.",
+}
+
 type mailServer struct {
 	bot     matrixbot
 	log     *logger.Logger
@@ -24,17 +30,19 @@ type mailServer struct {
 func (m *mailServer) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
 	m.log.Debug("Login state=%+v username=%+v", state, username)
 	if m.bot.IsBanned(state.RemoteAddr) {
-		return nil, errors.New("please, don't bother me anymore")
+		return nil, ErrBanned
 	}
 
 	if !utils.AddressValid(username) {
+		m.log.Debug("address %s is invalid", username)
 		m.bot.Ban(state.RemoteAddr)
-		return nil, errors.New("please, provide an email address")
+		return nil, ErrBanned
 	}
 
 	if !m.bot.AllowAuth(username, password) {
+		m.log.Debug("username=%s or password=<redacted> is invalid", username)
 		m.bot.Ban(state.RemoteAddr)
-		return nil, errors.New("email or password is invalid")
+		return nil, ErrBanned
 	}
 
 	return &outgoingSession{
@@ -51,7 +59,7 @@ func (m *mailServer) Login(state *smtp.ConnectionState, username, password strin
 func (m *mailServer) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
 	m.log.Debug("AnonymousLogin state=%+v", state)
 	if m.bot.IsBanned(state.RemoteAddr) {
-		return nil, errors.New("please, don't bother me anymore")
+		return nil, ErrBanned
 	}
 
 	return &incomingSession{

smtp/session.go

@@ -35,8 +35,9 @@ type incomingSession struct {
 func (s *incomingSession) Mail(from string, opts smtp.MailOptions) error {
 	sentry.GetHubFromContext(s.ctx).Scope().SetTag("from", from)
 	if !utils.AddressValid(from) {
+		s.log.Debug("address %s is invalid", from)
 		s.ban(s.addr)
-		return errors.New("please, provide email address")
+		return ErrBanned
 	}
 	s.from = from
 	s.log.Debug("mail from %s, options: %+v", from, opts)
@@ -56,20 +57,20 @@ func (s *incomingSession) Rcpt(to string) error {
 	if !domainok {
 		s.log.Debug("wrong domain of %s", to)
 		s.ban(s.addr)
-		return smtp.ErrAuthRequired
+		return ErrBanned
 	}
 
 	roomID, ok := s.getRoomID(utils.Mailbox(to))
 	if !ok {
 		s.log.Debug("mapping for %s not found", to)
 		s.ban(s.addr)
-		return smtp.ErrAuthRequired
+		return ErrBanned
 	}
 
 	validations := s.getFilters(roomID)
 	if !validateEmail(s.from, s.to, s.log, validations) {
 		s.ban(s.addr)
-		return smtp.ErrAuthRequired
+		return ErrBanned
 	}
 
 	s.log.Debug("mail to %s", to)

utils/email.go

@@ -10,7 +10,7 @@ import (
 	"time"
 
 	"github.com/emersion/go-msgauth/dkim"
-	"gitlab.com/etke.cc/go/secgen"
+	"github.com/jhillyerd/enmime"
 	"maunium.net/go/mautrix/event"
 	"maunium.net/go/mautrix/format"
 	"maunium.net/go/mautrix/id"
@@ -143,75 +143,33 @@ func (e *Email) Content(threadID id.EventID, options *ContentOptions) *event.Con
 
 // Compose converts the email object to a string (to be used for delivery via SMTP) and possibly DKIM-signs it
 func (e *Email) Compose(privkey string) string {
+	mail := enmime.Builder().
+		From("", e.From).
+		To("", e.To).
+		Header("Message-Id", e.MessageID).
+		Subject(e.Subject).
+		Text([]byte(e.Text)).
+		HTML([]byte(e.HTML))
+	if e.InReplyTo != "" {
+		mail = mail.Header("In-Reply-To", e.InReplyTo)
+	}
+	if e.References != "" {
+		mail = mail.Header("References", e.References)
+	}
+
+	root, err := mail.Build()
+	if err != nil {
+		log.Error("cannot compose email: %v", err)
+		return ""
+	}
 	var data strings.Builder
+	err = root.Encode(&data)
+	if err != nil {
+		log.Error("cannot encode email: %v", err)
+		return ""
+	}
 
 	domain := strings.SplitN(e.From, "@", 2)[1]
-	boundaryName := "postmoogle" + secgen.Password(32)
-	boundary := "--" + boundaryName
-
-	data.WriteString("MIME-Version: 1.0")
-	data.WriteString("\r\n")
-
-	data.WriteString("Content-Type: multipart/alternative; boundary=")
-	data.WriteString(boundaryName)
-	data.WriteString("\r\n")
-
-	data.WriteString("Content-Transfer-Encoding: 8BIT")
-	data.WriteString("\r\n")
-
-	data.WriteString("From: ")
-	data.WriteString(e.From)
-	data.WriteString("\r\n")
-
-	data.WriteString("To: ")
-	data.WriteString(e.To)
-	data.WriteString("\r\n")
-
-	data.WriteString("Message-Id: ")
-	data.WriteString(e.MessageID)
-	data.WriteString("\r\n")
-
-	data.WriteString("Date: ")
-	data.WriteString(e.Date)
-	data.WriteString("\r\n")
-
-	if e.InReplyTo != "" {
-		data.WriteString("In-Reply-To: ")
-		data.WriteString(e.InReplyTo)
-		data.WriteString("\r\n")
-	}
-
-	if e.References != "" {
-		data.WriteString("References: ")
-		data.WriteString(e.References)
-		data.WriteString("\r\n")
-	}
-
-	data.WriteString("Subject: ")
-	data.WriteString(e.Subject)
-	data.WriteString("\r\n")
-	data.WriteString("\r\n")
-
-	data.WriteString(boundary)
-	data.WriteString("\r\n")
-	data.WriteString("Content-Type: text/html; charset=\"UTF-8\"")
-	data.WriteString("\r\n")
-	data.WriteString(e.HTML)
-	data.WriteString("\r\n")
-	data.WriteString("\r\n")
-
-	data.WriteString(boundary)
-	data.WriteString("\r\n")
-	data.WriteString("Content-Type: text/plain; charset=\"UTF-8\"")
-	data.WriteString("\r\n")
-	data.WriteString(e.Text)
-	data.WriteString("\r\n")
-	data.WriteString("\r\n")
-
-	data.WriteString(boundary)
-	data.WriteString("--")
-	data.WriteString("\r\n")
-
 	return e.sign(domain, privkey, data)
 }