use postmoogle as general purpose SMTP server and allow other apps or scripts to send emails through it

smtp/msa.go

@@ -2,10 +2,13 @@ package smtp
 
 import (
 	"context"
+	"errors"
 
 	"github.com/emersion/go-smtp"
 	"github.com/getsentry/sentry-go"
 	"gitlab.com/etke.cc/go/logger"
+
+	"gitlab.com/etke.cc/postmoogle/utils"
 )
 
 // msa is mail submission agent, implements smtp.Backend
@@ -13,11 +16,15 @@ type msa struct {
 	log    *logger.Logger
 	domain string
 	bot    Bot
+	mta    utils.MTA
 }
 
-func (m *msa) newSession() *msasession {
+func (m *msa) newSession(from string, local bool) *msasession {
 	return &msasession{
 		ctx:    sentry.SetHubOnContext(context.Background(), sentry.CurrentHub().Clone()),
+		mta:    m.mta,
+		from:   from,
+		local:  local,
 		log:    m.log,
 		bot:    m.bot,
 		domain: m.domain,
@@ -25,9 +32,18 @@ func (m *msa) newSession() *msasession {
 }
 
 func (m *msa) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
-	return nil, smtp.ErrAuthUnsupported
+	if !utils.AddressValid(username) {
+		return nil, errors.New("please, provide email address")
+	}
+
+	mailbox := utils.Mailbox(username)
+	if !m.bot.AllowAuth(mailbox, password) {
+		return nil, errors.New("email or password is invalid")
+	}
+
+	return m.newSession(username, false), nil
 }
 
 func (m *msa) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
-	return m.newSession(), nil
+	return m.newSession("", true), nil
 }

smtp/msasession.go

@@ -2,6 +2,7 @@ package smtp
 
 import (
 	"context"
+	"errors"
 	"io"
 
 	"github.com/emersion/go-smtp"
@@ -15,32 +16,41 @@ import (
 type msasession struct {
 	log    *logger.Logger
 	bot    Bot
+	mta    utils.MTA
 	domain string
 
-	ctx  context.Context
-	to   string
-	from string
+	ctx   context.Context
+	local bool
+	to    string
+	from  string
 }
 
 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)
+	if !utils.AddressValid(from) {
+		return errors.New("please, provide email address")
+	}
+	if s.local {
+		s.from = from
+		s.log.Debug("mail from %s, options: %+v", from, opts)
+	}
 	return nil
 }
 
 func (s *msasession) Rcpt(to string) error {
 	sentry.GetHubFromContext(s.ctx).Scope().SetTag("to", to)
 
-	if utils.Hostname(to) != s.domain {
-		s.log.Debug("wrong domain of %s", to)
-		return smtp.ErrAuthRequired
-	}
+	if s.local {
+		if utils.Hostname(to) != s.domain {
+			s.log.Debug("wrong domain of %s", to)
+			return smtp.ErrAuthRequired
+		}
 
-	_, ok := s.bot.GetMapping(utils.Mailbox(to))
-	if !ok {
-		s.log.Debug("mapping for %s not found", to)
-		return smtp.ErrAuthRequired
+		_, ok := s.bot.GetMapping(utils.Mailbox(to))
+		if !ok {
+			s.log.Debug("mapping for %s not found", to)
+			return smtp.ErrAuthRequired
+		}
 	}
 
 	s.to = to
@@ -80,7 +90,7 @@ func (s *msasession) Data(r io.Reader) error {
 		eml.HTML,
 		files)
 
-	return s.bot.Send2Matrix(s.ctx, email)
+	return s.bot.Send2Matrix(s.ctx, email, s.local)
 }
 
 func (s *msasession) Reset() {}

smtp/mta.go

@@ -17,8 +17,9 @@ import (
 
 // Bot interface to send emails into matrix
 type Bot interface {
+	AllowAuth(string, string) bool
 	GetMapping(string) (id.RoomID, bool)
-	Send2Matrix(ctx context.Context, email *utils.Email) error
+	Send2Matrix(ctx context.Context, email *utils.Email, local bool) error
 	SetMTA(mta utils.MTA)
 }
 

smtp/server.go

@@ -40,6 +40,7 @@ func NewServer(cfg *Config) *Server {
 	sender := NewMTA(cfg.LogLevel)
 	receiver := &msa{
 		log:    log,
+		mta:    sender,
 		bot:    cfg.Bot,
 		domain: cfg.Domain,
 	}
@@ -51,6 +52,7 @@ func NewServer(cfg *Config) *Server {
 	s.WriteTimeout = 10 * time.Second
 	s.MaxMessageBytes = cfg.MaxSize * 1024 * 1024
 	s.EnableREQUIRETLS = cfg.TLSRequired
+	s.AllowInsecureAuth = !cfg.TLSRequired
 	if log.GetLevel() == "DEBUG" || log.GetLevel() == "TRACE" {
 		s.Debug = os.Stdout
 	}