smtp.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 main
   8
   9 import (
  10         "crypto/tls"
  11         "fmt"
  12         "net"
  13         "net/mail"
  14         "os"
  15         "path"
  16         "strings"
  17
  18         "github.com/uber-go/zap"
  19
  20         "src.bluestatic.org/mailpopbox/smtp"
  21 )
  22
  23 func runSMTPServer(config Config, log zap.Logger) <-chan ServerControlMessage {
  24         server := smtpServer{
  25                 config:      config,
  26                 controlChan: make(chan ServerControlMessage),
  27                 log:         log.With(zap.String("server", "smtp")),
  28         }
  29         go server.run()
  30         return server.controlChan
  31 }
  32
  33 type smtpServer struct {
  34         config    Config
  35         tlsConfig *tls.Config
  36
  37         log zap.Logger
  38
  39         controlChan chan ServerControlMessage
  40 }
  41
  42 func (server *smtpServer) run() {
  43         if !server.loadTLSConfig() {
  44                 return
  45         }
  46
  47         addr := fmt.Sprintf(":%d", server.config.SMTPPort)
  48         server.log.Info("starting server", zap.String("address", addr))
  49
  50         l, err := net.Listen("tcp", addr)
  51         if err != nil {
  52                 server.log.Error("listen", zap.Error(err))
  53                 server.controlChan <- ServerControlFatalError
  54                 return
  55         }
  56
  57         connChan := make(chan net.Conn)
  58         go RunAcceptLoop(l, connChan, server.log)
  59
  60         reloadChan := CreateReloadSignal()
  61
  62         for {
  63                 select {
  64                 case <-reloadChan:
  65                         if !server.loadTLSConfig() {
  66                                 return
  67                         }
  68                 case conn, ok := <-connChan:
  69                         if ok {
  70                                 go smtp.AcceptConnection(conn, server, server.log)
  71                         } else {
  72                                 break
  73                         }
  74                 }
  75         }
  76 }
  77
  78 func (server *smtpServer) loadTLSConfig() bool {
  79         var err error
  80         server.tlsConfig, err = server.config.GetTLSConfig()
  81         if err != nil {
  82                 server.log.Error("failed to configure TLS", zap.Error(err))
  83                 server.controlChan <- ServerControlFatalError
  84                 return false
  85         }
  86         server.log.Info("loaded TLS config")
  87         return true
  88 }
  89
  90 func (server *smtpServer) Name() string {
  91         return server.config.Hostname
  92 }
  93
  94 func (server *smtpServer) TLSConfig() *tls.Config {
  95         return server.tlsConfig
  96 }
  97
  98 func (server *smtpServer) VerifyAddress(addr mail.Address) smtp.ReplyLine {
  99         if server.maildropForAddress(addr) == "" {
 100                 return smtp.ReplyBadMailbox
 101         }
 102         return smtp.ReplyOK
 103 }
 104
 105 func (server *smtpServer) OnEHLO() *smtp.ReplyLine {
 106         return nil
 107 }
 108
 109 func (server *smtpServer) OnMessageDelivered(en smtp.Envelope) *smtp.ReplyLine {
 110         maildrop := server.maildropForAddress(en.RcptTo[0])
 111         if maildrop == "" {
 112                 // TODO: log error
 113                 return &smtp.ReplyBadMailbox
 114         }
 115
 116         f, err := os.Create(path.Join(maildrop, en.ID+".msg"))
 117         if err != nil {
 118                 // TODO: log error
 119                 return &smtp.ReplyBadMailbox
 120         }
 121
 122         smtp.WriteEnvelopeForDelivery(f, en)
 123         f.Close()
 124         return nil
 125 }
 126
 127 func (server *smtpServer) maildropForAddress(addr mail.Address) string {
 128         domainIdx := strings.LastIndex(addr.Address, "@")
 129         if domainIdx == -1 {
 130                 return ""
 131         }
 132
 133         domain := addr.Address[domainIdx+1:]
 134
 135         for _, s := range server.config.Servers {
 136                 if domain == s.Domain {
 137                         return s.MaildropPath
 138                 }
 139         }
 140
 141         return ""
 142 }