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 EHOL.
  14         stateInitial
  15         stateMail
  16         stateRecipient
  17         stateData
  18 )
  19
  20 type connection struct {
  21         tp         *textproto.Conn
  22         remoteAddr net.Addr
  23
  24         state
  25         line string
  26
  27         ehlo     string
  28         mailFrom *mail.Address
  29         rcptTo   []mail.Address
  30 }
  31
  32 func AcceptConnection(netConn net.Conn, server Server) error {
  33         conn := connection{
  34                 tp:         textproto.NewConn(netConn),
  35                 remoteAddr: netConn.RemoteAddr(),
  36                 state:      stateNew,
  37         }
  38
  39         var err error
  40
  41         conn.writeReply(250, fmt.Sprintf("%s ESMTP [%s] mailpopbox", server.Name(), netConn.LocalAddr().String()))
  42
  43         for {
  44                 conn.line, err = conn.tp.ReadLine()
  45                 if err != nil {
  46                         conn.writeReply(500, "line too long")
  47                         continue
  48                 }
  49
  50                 var cmd string
  51                 if _, err = fmt.Sscanf(conn.line, "%s", &cmd); err != nil {
  52                         conn.writeBadSyntax()
  53                         continue
  54                 }
  55
  56                 switch cmd {
  57                 case "QUIT":
  58                         conn.tp.Close()
  59                         break
  60                 case "HELO":
  61                         fallthrough
  62                 case "EHLO":
  63                         conn.doEHLO()
  64                 case "MAIL":
  65                         conn.doMAIL()
  66                 case "RCPT":
  67                         conn.doRCPT()
  68                 case "DATA":
  69                         conn.doDATA()
  70                 case "RSET":
  71                         conn.doRSET()
  72                 case "VRFY":
  73                         conn.doVRFY()
  74                 case "EXPN":
  75                         conn.writeReply(550, "access denied")
  76                 case "NOOP":
  77                         conn.writeOK()
  78                 case "HELP":
  79                         conn.writeReply(250, "https://tools.ietf.org/html/rfc5321")
  80                 default:
  81                         conn.writeReply(500, "unrecognized command")
  82                 }
  83         }
  84
  85         return err
  86 }
  87
  88 func (conn *connection) writeReply(code int, msg string) {
  89         if len(msg) > 0 {
  90                 conn.tp.PrintfLine("%d %s", code, msg)
  91         } else {
  92                 conn.tp.PrintfLine("%d", code)
  93         }
  94 }
  95
  96 func (conn *connection) writeOK() {
  97         conn.writeReply(250, "OK")
  98 }
  99
 100 func (conn *connection) writeBadSyntax() {
 101         conn.writeReply(501, "syntax error")
 102 }
 103
 104 func (conn *connection) writeBadSequence() {
 105         conn.writeReply(503, "bad sequence of commands")
 106 }
 107
 108 func (conn *connection) doEHLO() {
 109         conn.resetBuffers()
 110
 111         var cmd string
 112         _, err := fmt.Sscanf(conn.line, "%s %s", &cmd, &conn.ehlo)
 113         if err != nil {
 114                 conn.writeBadSyntax()
 115                 return
 116         }
 117
 118         conn.writeReply(250, fmt.Sprintf("Hello %s, I am glad to meet you", conn.ehlo))
 119
 120         conn.state = stateInitial
 121 }
 122
 123 func (conn *connection) doMAIL() {
 124         if conn.state != stateInitial {
 125                 conn.writeBadSequence()
 126                 return
 127         }
 128
 129         var mailFrom string
 130         _, err := fmt.Sscanf(conn.line, "MAIL FROM:%s", &mailFrom)
 131         if err != nil {
 132                 conn.writeBadSyntax()
 133                 return
 134         }
 135
 136         conn.mailFrom, err = mail.ParseAddress(mailFrom)
 137         if err != nil {
 138                 conn.writeBadSyntax()
 139                 return
 140         }
 141
 142         conn.state = stateMail
 143         conn.writeOK()
 144 }
 145
 146 func (conn *connection) doRCPT() {
 147         if conn.state != stateMail && conn.state != stateRecipient {
 148                 conn.writeBadSequence()
 149                 return
 150         }
 151
 152         var rcptTo string
 153         _, err := fmt.Sscanf(conn.line, "RCPT TO:%s", &rcptTo)
 154         if err != nil {
 155                 conn.writeBadSyntax()
 156                 return
 157         }
 158
 159         address, err := mail.ParseAddress(rcptTo)
 160         if err != nil {
 161                 conn.writeBadSyntax()
 162         }
 163
 164         conn.rcptTo = append(conn.rcptTo, *address)
 165
 166         conn.state = stateRecipient
 167         conn.writeOK()
 168 }
 169
 170 func (conn *connection) doDATA() {
 171         if conn.state != stateRecipient {
 172                 conn.writeBadSequence()
 173                 return
 174         }
 175
 176         conn.writeReply(354, "Start mail input; end with <CRLF>.<CRLF>")
 177
 178         data, err := conn.tp.ReadDotBytes()
 179         if err != nil {
 180                 // TODO: log error
 181                 conn.writeReply(552, "transaction failed")
 182                 return
 183         }
 184
 185         fmt.Println(string(data))
 186
 187         conn.state = stateInitial
 188         conn.writeOK()
 189 }
 190
 191 func (conn *connection) doVRFY() {
 192 }
 193
 194 func (conn *connection) doRSET() {
 195         conn.state = stateInitial
 196         conn.resetBuffers()
 197         conn.writeOK()
 198 }
 199
 200 func (conn *connection) resetBuffers() {
 201         conn.mailFrom = nil
 202         conn.rcptTo = make([]mail.Address, 0)
 203 }