smtp/conn.go

   1 package smtp
   2
   3 import (
   4         "fmt"
   5         "net"
   6         "net/mail"
   7         "net/textproto"
   8 )
   9
  10 type state int
  11
  12 const (
  13         stateNew state = iota // Before EHLO.
  14         stateInitial
  15         stateMail
  16         stateRecipient
  17         stateData
  18 )
  19
  20 type connection struct {
  21         server Server
  22
  23         tp         *textproto.Conn
  24         remoteAddr net.Addr
  25
  26         state
  27         line string
  28
  29         ehlo     string
  30         mailFrom *mail.Address
  31         rcptTo   []mail.Address
  32 }
  33
  34 func AcceptConnection(netConn net.Conn, server Server) error {
  35         conn := connection{
  36                 server:     server,
  37                 tp:         textproto.NewConn(netConn),
  38                 remoteAddr: netConn.RemoteAddr(),
  39                 state:      stateNew,
  40         }
  41
  42         var err error
  43
  44         conn.writeReply(250, fmt.Sprintf("%s ESMTP [%s] (mailpopbox)", server.Name(), netConn.LocalAddr()))
  45
  46         for {
  47                 conn.line, err = conn.tp.ReadLine()
  48                 if err != nil {
  49                         conn.writeReply(500, "line too long")
  50                         continue
  51                 }
  52
  53                 var cmd string
  54                 if _, err = fmt.Sscanf(conn.line, "%s", &cmd); err != nil {
  55                         conn.reply(ReplyBadSyntax)
  56                         continue
  57                 }
  58
  59                 switch cmd {
  60                 case "QUIT":
  61                         conn.tp.Close()
  62                         break
  63                 case "HELO":
  64                         fallthrough
  65                 case "EHLO":
  66                         conn.doEHLO()
  67                 case "MAIL":
  68                         conn.doMAIL()
  69                 case "RCPT":
  70                         conn.doRCPT()
  71                 case "DATA":
  72                         conn.doDATA()
  73                 case "RSET":
  74                         conn.doRSET()
  75                 case "VRFY":
  76                         conn.doVRFY()
  77                 case "EXPN":
  78                         conn.writeReply(550, "access denied")
  79                 case "NOOP":
  80                         conn.reply(ReplyOK)
  81                 case "HELP":
  82                         conn.writeReply(250, "https://tools.ietf.org/html/rfc5321")
  83                 default:
  84                         conn.writeReply(500, "unrecognized command")
  85                 }
  86         }
  87
  88         return err
  89 }
  90
  91 func (conn *connection) reply(reply ReplyLine) {
  92         conn.writeReply(reply.Code, reply.Message)
  93 }
  94
  95 func (conn *connection) writeReply(code int, msg string) {
  96         if len(msg) > 0 {
  97                 conn.tp.PrintfLine("%d %s", code, msg)
  98         } else {
  99                 conn.tp.PrintfLine("%d", code)
 100         }
 101 }
 102
 103 func (conn *connection) doEHLO() {
 104         conn.resetBuffers()
 105
 106         var cmd string
 107         _, err := fmt.Sscanf(conn.line, "%s %s", &cmd, &conn.ehlo)
 108         if err != nil {
 109                 conn.reply(ReplyBadSyntax)
 110                 return
 111         }
 112
 113         if cmd == "HELO" {
 114                 conn.writeReply(250, fmt.Sprintf("Hello %s [%s]", conn.ehlo, conn.remoteAddr))
 115         } else {
 116                 conn.tp.PrintfLine("250-Hello %s [%s]", conn.ehlo, conn.remoteAddr)
 117                 if conn.server.TLSConfig() != nil {
 118                         conn.tp.PrintfLine("250-STARTTLS")
 119                 }
 120                 conn.tp.PrintfLine("250 SIZE %d", 40960000)
 121         }
 122
 123         conn.state = stateInitial
 124 }
 125
 126 func (conn *connection) doMAIL() {
 127         if conn.state != stateInitial {
 128                 conn.reply(ReplyBadSequence)
 129                 return
 130         }
 131
 132         var mailFrom string
 133         _, err := fmt.Sscanf(conn.line, "MAIL FROM:%s", &mailFrom)
 134         if err != nil {
 135                 conn.reply(ReplyBadSyntax)
 136                 return
 137         }
 138
 139         conn.mailFrom, err = mail.ParseAddress(mailFrom)
 140         if err != nil {
 141                 conn.reply(ReplyBadSyntax)
 142                 return
 143         }
 144
 145         conn.state = stateMail
 146         conn.reply(ReplyOK)
 147 }
 148
 149 func (conn *connection) doRCPT() {
 150         if conn.state != stateMail && conn.state != stateRecipient {
 151                 conn.reply(ReplyBadSequence)
 152                 return
 153         }
 154
 155         var rcptTo string
 156         _, err := fmt.Sscanf(conn.line, "RCPT TO:%s", &rcptTo)
 157         if err != nil {
 158                 conn.reply(ReplyBadSyntax)
 159                 return
 160         }
 161
 162         address, err := mail.ParseAddress(rcptTo)
 163         if err != nil {
 164                 conn.reply(ReplyBadSyntax)
 165         }
 166
 167         conn.rcptTo = append(conn.rcptTo, *address)
 168
 169         conn.state = stateRecipient
 170         conn.reply(ReplyOK)
 171 }
 172
 173 func (conn *connection) doDATA() {
 174         if conn.state != stateRecipient {
 175                 conn.reply(ReplyBadSequence)
 176                 return
 177         }
 178
 179         conn.writeReply(354, "Start mail input; end with <CRLF>.<CRLF>")
 180
 181         data, err := conn.tp.ReadDotBytes()
 182         if err != nil {
 183                 // TODO: log error
 184                 conn.writeReply(552, "transaction failed")
 185                 return
 186         }
 187
 188         env := Envelope{
 189                 RemoteAddr: conn.remoteAddr,
 190                 EHLO:       conn.ehlo,
 191                 MailFrom:   *conn.mailFrom,
 192                 RcptTo:     conn.rcptTo,
 193                 Data:       data,
 194         }
 195
 196         if reply := conn.server.OnMessageDelivered(env); reply != nil {
 197                 conn.reply(*reply)
 198                 return
 199         }
 200
 201         conn.state = stateInitial
 202         conn.reply(ReplyOK)
 203 }
 204
 205 func (conn *connection) doVRFY() {
 206 }
 207
 208 func (conn *connection) doRSET() {
 209         conn.state = stateInitial
 210         conn.resetBuffers()
 211         conn.reply(ReplyOK)
 212 }
 213
 214 func (conn *connection) resetBuffers() {
 215         conn.mailFrom = nil
 216         conn.rcptTo = make([]mail.Address, 0)
 217 }