pop3/conn.go

   1 package pop3
   2
   3 import (
   4         "fmt"
   5         "net"
   6         "net/textproto"
   7         "strings"
   8 )
   9
  10 type state int
  11
  12 const (
  13         stateAuth state = iota
  14         stateTxn
  15         stateUpdate
  16 )
  17
  18 const (
  19         errStateAuth = "not in AUTHORIZATION"
  20         errStateTxn  = "not in TRANSACTION"
  21         errSyntax    = "syntax error"
  22 )
  23
  24 type connection struct {
  25         po PostOffice
  26         mb Mailbox
  27
  28         tp         *textproto.Conn
  29         remoteAddr net.Addr
  30
  31         state
  32         line string
  33
  34         user string
  35 }
  36
  37 func AcceptConnection(netConn net.Conn, po PostOffice) {
  38         conn := connection{
  39                 po:    po,
  40                 tp:    textproto.NewConn(netConn),
  41                 state: stateAuth,
  42         }
  43
  44         var err error
  45         conn.ok(fmt.Sprintf("POP3 (mailpopbox) server %s", po.Name()))
  46
  47         for {
  48                 conn.line, err = conn.tp.ReadLine()
  49                 if err != nil {
  50                         conn.err("did't catch that")
  51                         continue
  52                 }
  53
  54                 var cmd string
  55                 if _, err := fmt.Sscanf(conn.line, "%s", &cmd); err != nil {
  56                         conn.err("invalid command")
  57                         continue
  58                 }
  59
  60                 switch cmd {
  61                 case "QUIT":
  62                         conn.doQUIT()
  63                         break
  64                 case "USER":
  65                         conn.doUSER()
  66                 case "PASS":
  67                         conn.doPASS()
  68                 case "STAT":
  69                         conn.doSTAT()
  70                 case "LIST":
  71                         conn.doLIST()
  72                 case "RETR":
  73                         conn.doRETR()
  74                 case "DELE":
  75                         conn.doDELE()
  76                 case "NOOP":
  77                         conn.ok("")
  78                 case "RSET":
  79                         conn.doRSET()
  80                 default:
  81                         conn.err("unknown command")
  82                 }
  83         }
  84 }
  85
  86 func (conn *connection) ok(msg string) {
  87         if len(msg) > 0 {
  88                 msg = " " + msg
  89         }
  90         conn.tp.PrintfLine("+OK%s", msg)
  91 }
  92
  93 func (conn *connection) err(msg string) {
  94         if len(msg) > 0 {
  95                 msg = " " + msg
  96                 conn.tp.PrintfLine("-ERR%s", msg)
  97         }
  98 }
  99
 100 func (conn *connection) doQUIT() {
 101         defer conn.tp.Close()
 102
 103         if conn.mb != nil {
 104                 err := conn.mb.Close()
 105                 if err != nil {
 106                         conn.err("failed to remove some messages")
 107                         return
 108                 }
 109         }
 110         conn.ok("goodbye")
 111 }
 112
 113 func (conn *connection) doUSER() {
 114         if conn.state != stateAuth {
 115                 conn.err(errStateAuth)
 116                 return
 117         }
 118
 119         if _, err := fmt.Sscanf(conn.line, "USER %s", &conn.user); err != nil {
 120                 conn.err(errSyntax)
 121                 return
 122         }
 123
 124         conn.ok("")
 125 }
 126
 127 func (conn *connection) doPASS() {
 128         if conn.state != stateAuth {
 129                 conn.err(errStateAuth)
 130                 return
 131         }
 132
 133         if len(conn.user) == 0 {
 134                 conn.err("no USER")
 135                 return
 136         }
 137
 138         pass := strings.TrimPrefix(conn.line, "PASS ")
 139         if mbox, err := conn.po.OpenMailbox(conn.user, pass); err == nil {
 140                 conn.state = stateTxn
 141                 conn.mb = mbox
 142                 conn.ok("")
 143         } else {
 144                 conn.err(err.Error())
 145         }
 146 }
 147
 148 func (conn *connection) doSTAT() {
 149         if conn.state != stateTxn {
 150                 conn.err(errStateTxn)
 151                 return
 152         }
 153 }
 154
 155 func (conn *connection) doLIST() {
 156         if conn.state != stateTxn {
 157                 conn.err(errStateTxn)
 158                 return
 159         }
 160 }
 161
 162 func (conn *connection) doRETR() {
 163         if conn.state != stateTxn {
 164                 conn.err(errStateTxn)
 165                 return
 166         }
 167 }
 168
 169 func (conn *connection) doDELE() {
 170         if conn.state != stateTxn {
 171                 conn.err(errStateTxn)
 172                 return
 173         }
 174 }
 175
 176 func (conn *connection) doRSET() {
 177         if conn.state != stateTxn {
 178                 conn.err(errStateTxn)
 179                 return
 180         }
 181         conn.mb.Reset()
 182         conn.ok("")
 183 }