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package smtpsrv
import (
"context"
"fmt"
"log/slog"
"net"
"strings"
"time"
"github.com/emersion/go-smtp"
)
// SMTPLogger implements the smtp.Logger interface using the main app Logger.
type SMTPLogger struct {
logger *slog.Logger
}
// Printf adheres to smtp.Server's Logger interface.
func (l *SMTPLogger) Printf(format string, v ...interface{}) {
s := fmt.Sprintf(format, v...)
// TODO: Uses string compare to filter out errors caused by TCP health checks,
// remove once https://github.com/emersion/go-smtp/issues/236 has been fixed.
if strings.Contains(s, "read: connection reset by peer") {
return
}
l.logger.Error("SMTP error.", slog.String("error", s))
}
// Print adheres to smtp.Server's Logger interface.
func (l *SMTPLogger) Println(v ...interface{}) {
s := fmt.Sprint(v...)
// TODO: Uses string compare to filter out errors caused by TCP health checks,
// remove once https://github.com/emersion/go-smtp/issues/236 has been fixed.
if strings.Contains(s, "read: connection reset by peer") {
return
}
l.logger.Error("SMTP error.", slog.String("error", s))
}
// Server implements an SMTP server that creates alerts.
type Server struct {
cfg Config
srv *smtp.Server
}
// NewServer creates a new Server.
func NewServer(cfg Config) *Server {
s := &Server{cfg: cfg}
srv := smtp.NewServer(s)
srv.ErrorLog = &SMTPLogger{logger: cfg.Logger}
srv.Domain = cfg.Domain
srv.ReadTimeout = 10 * time.Second
srv.WriteTimeout = 10 * time.Second
srv.TLSConfig = cfg.TLSConfig
s.srv = srv
if cfg.MaxRecipients == 0 {
cfg.MaxRecipients = 1
}
if cfg.BackgroundContext == nil {
panic("smtpsrv: BackgroundContext is required")
}
if cfg.AuthorizeFunc == nil {
panic("smtpsrv: AuthorizeFunc is required")
}
if cfg.CreateAlertFunc == nil {
panic("smtpsrv: CreateAlertFunc is required")
}
return s
}
var _ smtp.Backend = &Server{}
// ServeSMTP starts the SMTP server on the given listener.
func (s *Server) ServeSMTP(l net.Listener) error { return s.srv.Serve(l) }
// NewSession implements the smtp.Backend interface.
func (s *Server) NewSession(_ *smtp.Conn) (smtp.Session, error) { return &Session{cfg: s.cfg}, nil }
// Shutdown gracefully shuts down the SMTP server.
func (s *Server) Shutdown(ctx context.Context) error { return s.srv.Shutdown(ctx) }
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