WIP

server/smtp_server.go

@@ -0,0 +1,108 @@
+package server
+
+import (
+	"bytes"
+	"errors"
+	"github.com/emersion/go-smtp"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/mail"
+	"strings"
+	"sync"
+)
+
+// smtpBackend implements SMTP server methods.
+type smtpBackend struct {
+	config *Config
+	sub    subscriber
+}
+
+func newMailBackend(conf *Config, sub subscriber) *smtpBackend {
+	return &smtpBackend{
+		config: conf,
+		sub:    sub,
+	}
+}
+
+func (b *smtpBackend) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
+	return &smtpSession{config: b.config, sub: b.sub}, nil
+}
+
+func (b *smtpBackend) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
+	return &smtpSession{config: b.config, sub: b.sub}, nil
+}
+
+// smtpSession is returned after EHLO.
+type smtpSession struct {
+	config   *Config
+	sub      subscriber
+	from, to string
+	mu       sync.Mutex
+}
+
+func (s *smtpSession) AuthPlain(username, password string) error {
+	return nil
+}
+
+func (s *smtpSession) Mail(from string, opts smtp.MailOptions) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.from = from
+	return nil
+}
+
+func (s *smtpSession) Rcpt(to string) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	addressList, err := mail.ParseAddressList(to)
+	if err != nil {
+		return err
+	} else if len(addressList) != 1 {
+		return errors.New("only one recipient supported")
+	} else if !strings.HasSuffix(addressList[0].Address, "@"+s.config.SMTPServerDomain) {
+		return errors.New("invalid domain")
+	} else if s.config.SMTPServerAddrPrefix != "" && !strings.HasPrefix(addressList[0].Address, s.config.SMTPServerAddrPrefix) {
+		return errors.New("invalid address")
+	}
+	// FIXME check topic format
+	s.to = addressList[0].Address
+	return nil
+}
+
+func (s *smtpSession) Data(r io.Reader) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return err
+	}
+
+	log.Println("Data:", string(b))
+	msg, err := mail.ReadMessage(bytes.NewReader(b))
+	if err != nil {
+		return err
+	}
+	body, err := io.ReadAll(msg.Body)
+	if err != nil {
+		return err
+	}
+	topic := strings.TrimSuffix(s.to, "@"+s.config.SMTPServerDomain)
+	m := newDefaultMessage(topic, string(body))
+	subject := msg.Header.Get("Subject")
+	if subject != "" {
+		m.Title = subject
+	}
+	return s.sub(m)
+}
+
+func (s *smtpSession) Reset() {
+	s.mu.Lock()
+	s.from = ""
+	s.to = ""
+	s.mu.Unlock()
+}
+
+func (s *smtpSession) Logout() error {
+	return nil
+}