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(220, 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.writeReply(221, "Goodbye")
  62                         conn.tp.Close()
  63                         break
  64                 case "HELO":
  65                         fallthrough
  66                 case "EHLO":
  67                         conn.doEHLO()
  68                 case "MAIL":
  69                         conn.doMAIL()
  70                 case "RCPT":
  71                         conn.doRCPT()
  72                 case "DATA":
  73                         conn.doDATA()
  74                 case "RSET":
  75                         conn.doRSET()
  76                 case "VRFY":
  77                         conn.writeReply(252, "I'll do my best")
  78                 case "EXPN":
  79                         conn.writeReply(550, "access denied")
  80                 case "NOOP":
  81                         conn.reply(ReplyOK)
  82                 case "HELP":
  83                         conn.writeReply(250, "https://tools.ietf.org/html/rfc5321")
  84                 default:
  85                         conn.writeReply(500, "unrecognized command")
  86                 }
  87         }
  88
  89         return err
  90 }
  91
  92 func (conn *connection) reply(reply ReplyLine) {
  93         conn.writeReply(reply.Code, reply.Message)
  94 }
  95
  96 func (conn *connection) writeReply(code int, msg string) {
  97         if len(msg) > 0 {
  98                 conn.tp.PrintfLine("%d %s", code, msg)
  99         } else {
 100                 conn.tp.PrintfLine("%d", code)
 101         }
 102 }
 103
 104 func (conn *connection) doEHLO() {
 105         conn.resetBuffers()
 106
 107         var cmd string
 108         _, err := fmt.Sscanf(conn.line, "%s %s", &cmd, &conn.ehlo)
 109         if err != nil {
 110                 conn.reply(ReplyBadSyntax)
 111                 return
 112         }
 113
 114         if cmd == "HELO" {
 115                 conn.writeReply(250, fmt.Sprintf("Hello %s [%s]", conn.ehlo, conn.remoteAddr))
 116         } else {
 117                 conn.tp.PrintfLine("250-Hello %s [%s]", conn.ehlo, conn.remoteAddr)
 118                 if conn.server.TLSConfig() != nil {
 119                         conn.tp.PrintfLine("250-STARTTLS")
 120                 }
 121                 conn.tp.PrintfLine("250 SIZE %d", 40960000)
 122         }
 123
 124         conn.state = stateInitial
 125 }
 126
 127 func (conn *connection) doMAIL() {
 128         if conn.state != stateInitial {
 129                 conn.reply(ReplyBadSequence)
 130                 return
 131         }
 132
 133         var mailFrom string
 134         _, err := fmt.Sscanf(conn.line, "MAIL FROM:%s", &mailFrom)
 135         if err != nil {
 136                 conn.reply(ReplyBadSyntax)
 137                 return
 138         }
 139
 140         conn.mailFrom, err = mail.ParseAddress(mailFrom)
 141         if err != nil {
 142                 conn.reply(ReplyBadSyntax)
 143                 return
 144         }
 145
 146         conn.state = stateMail
 147         conn.reply(ReplyOK)
 148 }
 149
 150 func (conn *connection) doRCPT() {
 151         if conn.state != stateMail && conn.state != stateRecipient {
 152                 conn.reply(ReplyBadSequence)
 153                 return
 154         }
 155
 156         var rcptTo string
 157         _, err := fmt.Sscanf(conn.line, "RCPT TO:%s", &rcptTo)
 158         if err != nil {
 159                 conn.reply(ReplyBadSyntax)
 160                 return
 161         }
 162
 163         address, err := mail.ParseAddress(rcptTo)
 164         if err != nil {
 165                 conn.reply(ReplyBadSyntax)
 166         }
 167
 168         if reply := conn.server.VerifyAddress(*address); reply != ReplyOK {
 169                 conn.reply(reply)
 170                 return
 171         }
 172
 173         conn.rcptTo = append(conn.rcptTo, *address)
 174
 175         conn.state = stateRecipient
 176         conn.reply(ReplyOK)
 177 }
 178
 179 func (conn *connection) doDATA() {
 180         if conn.state != stateRecipient {
 181                 conn.reply(ReplyBadSequence)
 182                 return
 183         }
 184
 185         conn.writeReply(354, "Start mail input; end with <CRLF>.<CRLF>")
 186
 187         data, err := conn.tp.ReadDotBytes()
 188         if err != nil {
 189                 // TODO: log error
 190                 conn.writeReply(552, "transaction failed")
 191                 return
 192         }
 193
 194         env := Envelope{
 195                 RemoteAddr: conn.remoteAddr,
 196                 EHLO:       conn.ehlo,
 197                 MailFrom:   *conn.mailFrom,
 198                 RcptTo:     conn.rcptTo,
 199                 Data:       data,
 200         }
 201
 202         if reply := conn.server.OnMessageDelivered(env); reply != nil {
 203                 conn.reply(*reply)
 204                 return
 205         }
 206
 207         conn.state = stateInitial
 208         conn.reply(ReplyOK)
 209 }
 210
 211 func (conn *connection) doRSET() {
 212         conn.state = stateInitial
 213         conn.resetBuffers()
 214         conn.reply(ReplyOK)
 215 }
 216
 217 func (conn *connection) resetBuffers() {
 218         conn.mailFrom = nil
 219         conn.rcptTo = make([]mail.Address, 0)
 220 }