smtp/server.go

   1 // mailpopbox
   2 // Copyright 2020 Blue Static <https://www.bluestatic.org>
   3 // This program is free software licensed under the GNU General Public License,
   4 // version 3.0. The full text of the license can be found in LICENSE.txt.
   5 // SPDX-License-Identifier: GPL-3.0-only
   6
   7 package smtp
   8
   9 import (
  10         "crypto/tls"
  11         "regexp"
  12         "fmt"
  13         "io"
  14         "net"
  15         "net/mail"
  16         "strings"
  17         "time"
  18 )
  19
  20 type ReplyLine struct {
  21         Code    int
  22         Message string
  23 }
  24
  25 func (l ReplyLine) String() string {
  26         return fmt.Sprintf("%d %s", l.Code, l.Message)
  27 }
  28
  29 var SendAsSubject = regexp.MustCompile(`(?i)\[sendas:\s*([a-zA-Z0-9\.\-_]+)\]`)
  30
  31 var (
  32         ReplyOK               = ReplyLine{250, "OK"}
  33         ReplyBadSyntax        = ReplyLine{501, "syntax error"}
  34         ReplyBadSequence      = ReplyLine{503, "bad sequence of commands"}
  35         ReplyBadMailbox       = ReplyLine{550, "mailbox unavailable"}
  36         ReplyMailboxUnallowed = ReplyLine{553, "mailbox name not allowed"}
  37 )
  38
  39 func DomainForAddress(addr mail.Address) string {
  40         return DomainForAddressString(addr.Address)
  41 }
  42
  43 func DomainForAddressString(address string) string {
  44         domainIdx := strings.LastIndex(address, "@")
  45         if domainIdx == -1 {
  46                 return ""
  47         }
  48         return address[domainIdx+1:]
  49 }
  50
  51 type Envelope struct {
  52         RemoteAddr net.Addr
  53         EHLO       string
  54         MailFrom   mail.Address
  55         RcptTo     []mail.Address
  56         Data       []byte
  57         Received   time.Time
  58         ID         string
  59 }
  60
  61 func WriteEnvelopeForDelivery(w io.Writer, e Envelope) {
  62         fmt.Fprintf(w, "Delivered-To: <%s>\r\n", e.RcptTo[0].Address)
  63         fmt.Fprintf(w, "Return-Path: <%s>\r\n", e.MailFrom.Address)
  64         w.Write(e.Data)
  65 }
  66
  67 type Server interface {
  68         Name() string
  69         TLSConfig() *tls.Config
  70         VerifyAddress(mail.Address) ReplyLine
  71         // Verify that the authc+passwd identity can send mail as authz.
  72         Authenticate(authz, authc, passwd string) bool
  73         OnMessageDelivered(Envelope) *ReplyLine
  74
  75         // RelayMessage instructs the server to send the Envelope to another
  76         // MTA for outbound delivery.
  77         RelayMessage(Envelope)
  78 }
  79
  80 type EmptyServerCallbacks struct{}
  81
  82 func (*EmptyServerCallbacks) TLSConfig() *tls.Config {
  83         return nil
  84 }
  85
  86 func (*EmptyServerCallbacks) VerifyAddress(mail.Address) ReplyLine {
  87         return ReplyOK
  88 }
  89
  90 func (*EmptyServerCallbacks) Authenticate(authz, authc, passwd string) bool {
  91         return false
  92 }
  93
  94 func (*EmptyServerCallbacks) OnMessageDelivered(Envelope) *ReplyLine {
  95         return nil
  96 }
  97
  98 func (*EmptyServerCallbacks) RelayMessage(Envelope) {
  99 }