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// SPDX-License-Identifier: AGPL-3.0-only
// SPDX-FileCopyrightText: Copyright (c) 2025 Runxi Yu <https://runxiyu.org>
// SPDX-FileCopyrightText: Copyright (c) 2024 Robin Jarry <robin@jarry.cc>
package forge
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"log/slog"
"net"
"strings"
"time"
"github.com/emersion/go-message"
"github.com/emersion/go-smtp"
"go.lindenii.runxiyu.org/forge/internal/misc"
)
type lmtpHandler struct{}
type lmtpSession struct {
from string
to []string
ctx context.Context
cancel context.CancelFunc
s Server
}
func (session *lmtpSession) Reset() {
session.from = ""
session.to = nil
}
func (session *lmtpSession) Logout() error {
session.cancel()
return nil
}
func (session *lmtpSession) AuthPlain(_, _ string) error {
return nil
}
func (session *lmtpSession) Mail(from string, _ *smtp.MailOptions) error {
session.from = from
return nil
}
func (session *lmtpSession) Rcpt(to string, _ *smtp.RcptOptions) error {
session.to = append(session.to, to)
return nil
}
func (*lmtpHandler) NewSession(_ *smtp.Conn) (smtp.Session, error) {
ctx, cancel := context.WithCancel(context.Background())
session := &lmtpSession{
ctx: ctx,
cancel: cancel,
}
return session, nil
}
func (s *Server) serveLMTP(listener net.Listener) error {
smtpServer := smtp.NewServer(&lmtpHandler{})
smtpServer.LMTP = true
smtpServer.Domain = s.config.LMTP.Domain
smtpServer.Addr = s.config.LMTP.Socket
smtpServer.WriteTimeout = time.Duration(s.config.LMTP.WriteTimeout) * time.Second
smtpServer.ReadTimeout = time.Duration(s.config.LMTP.ReadTimeout) * time.Second
smtpServer.EnableSMTPUTF8 = true
return smtpServer.Serve(listener)
}
func (session *lmtpSession) Data(r io.Reader) error {
var (
email *message.Entity
from string
to []string
err error
buf bytes.Buffer
data []byte
n int64
)
n, err = io.CopyN(&buf, r, session.s.config.LMTP.MaxSize)
switch {
case n == session.s.config.LMTP.MaxSize:
err = errors.New("Message too big.")
// drain whatever is left in the pipe
_, _ = io.Copy(io.Discard, r)
goto end
case errors.Is(err, io.EOF):
// message was smaller than max size
break
case err != nil:
goto end
}
data = buf.Bytes()
email, err = message.Read(bytes.NewReader(data))
if err != nil && message.IsUnknownCharset(err) {
goto end
}
switch strings.ToLower(email.Header.Get("Auto-Submitted")) {
case "auto-generated", "auto-replied":
// Disregard automatic emails like OOO repliesession.s.
slog.Info("ignoring automatic message",
"from", session.from,
"to", strings.Join(session.to, ","),
"message-id", email.Header.Get("Message-Id"),
"subject", email.Header.Get("Subject"),
)
goto end
}
slog.Info("message received",
"from", session.from,
"to", strings.Join(session.to, ","),
"message-id", email.Header.Get("Message-Id"),
"subject", email.Header.Get("Subject"),
)
// Make local copies of the values before to ensure the references will
// still be valid when the task is run.
from = session.from
to = session.to
_ = from
for _, to := range to {
if !strings.HasSuffix(to, "@"+session.s.config.LMTP.Domain) {
continue
}
localPart := to[:len(to)-len("@"+session.s.config.LMTP.Domain)]
var segments []string
segments, err = misc.PathToSegments(localPart)
if err != nil {
// TODO: Should the entire email fail or should we just
// notify them out of band?
err = fmt.Errorf("cannot parse path: %w", err)
goto end
}
sepIndex := -1
for i, part := range segments {
if part == "-" {
sepIndex = i
break
}
}
if segments[len(segments)-1] == "" {
segments = segments[:len(segments)-1] // We don't care about dir or not.
}
if sepIndex == -1 || len(segments) <= sepIndex+2 {
err = errors.New("illegal path")
goto end
}
mbox := bytes.Buffer{}
if _, err = fmt.Fprint(&mbox, "From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001\r\n"); err != nil {
slog.Error("error handling patch... malloc???", "error", err)
goto end
}
data = bytes.ReplaceAll(data, []byte("\r\n"), []byte("\n"))
if _, err = mbox.Write(data); err != nil {
slog.Error("error handling patch... malloc???", "error", err)
goto end
}
// TODO: Is mbox's From escaping necessary here?
groupPath := segments[:sepIndex]
moduleType := segments[sepIndex+1]
moduleName := segments[sepIndex+2]
switch moduleType {
case "repos":
err = session.s.lmtpHandlePatch(session, groupPath, moduleName, &mbox)
if err != nil {
slog.Error("error handling patch", "error", err)
goto end
}
default:
err = errors.New("Emailing any endpoint other than repositories, is not supported yet.") // TODO
goto end
}
}
end:
session.to = nil
session.from = ""
switch err {
case nil:
return nil
default:
return &smtp.SMTPError{
Code: 550,
Message: "Permanent failure: " + err.Error(),
EnhancedCode: [3]int{5, 7, 1},
}
}
}
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