pop3/conn.go

   1 package pop3
   2
   3 import (
   4         "fmt"
   5         "io"
   6         "net"
   7         "net/textproto"
   8         "strings"
   9
  10         "github.com/uber-go/zap"
  11 )
  12
  13 type state int
  14
  15 const (
  16         stateAuth state = iota
  17         stateTxn
  18         stateUpdate
  19 )
  20
  21 const (
  22         errStateAuth  = "not in AUTHORIZATION"
  23         errStateTxn   = "not in TRANSACTION"
  24         errSyntax     = "syntax error"
  25         errDeletedMsg = "no such message - deleted"
  26 )
  27
  28 type connection struct {
  29         po PostOffice
  30         mb Mailbox
  31
  32         tp         *textproto.Conn
  33         remoteAddr net.Addr
  34
  35         log zap.Logger
  36
  37         state
  38         line string
  39
  40         user string
  41 }
  42
  43 func AcceptConnection(netConn net.Conn, po PostOffice, log zap.Logger) {
  44         conn := connection{
  45                 po:    po,
  46                 tp:    textproto.NewConn(netConn),
  47                 state: stateAuth,
  48                 log:   log.With(zap.Stringer("client", netConn.RemoteAddr())),
  49         }
  50
  51         var err error
  52         conn.ok(fmt.Sprintf("POP3 (mailpopbox) server %s", po.Name()))
  53
  54         for {
  55                 conn.line, err = conn.tp.ReadLine()
  56                 if err != nil {
  57                         conn.log.Error("ReadLine()", zap.Error(err))
  58                         conn.tp.Close()
  59                         return
  60                 }
  61
  62                 var cmd string
  63                 if _, err := fmt.Sscanf(conn.line, "%s", &cmd); err != nil {
  64                         conn.err("invalid command")
  65                         continue
  66                 }
  67
  68                 switch strings.ToUpper(cmd) {
  69                 case "QUIT":
  70                         conn.doQUIT()
  71                         return
  72                 case "USER":
  73                         conn.doUSER()
  74                 case "PASS":
  75                         conn.doPASS()
  76                 case "STAT":
  77                         conn.doSTAT()
  78                 case "LIST":
  79                         conn.doLIST()
  80                 case "RETR":
  81                         conn.doRETR()
  82                 case "DELE":
  83                         conn.doDELE()
  84                 case "NOOP":
  85                         conn.ok("")
  86                 case "RSET":
  87                         conn.doRSET()
  88                 default:
  89                         conn.err("unknown command")
  90                 }
  91         }
  92 }
  93
  94 func (conn *connection) ok(msg string) {
  95         if len(msg) > 0 {
  96                 msg = " " + msg
  97         }
  98         conn.tp.PrintfLine("+OK%s", msg)
  99 }
 100
 101 func (conn *connection) err(msg string) {
 102         if len(msg) > 0 {
 103                 msg = " " + msg
 104                 conn.tp.PrintfLine("-ERR%s", msg)
 105         }
 106 }
 107
 108 func (conn *connection) doQUIT() {
 109         defer conn.tp.Close()
 110
 111         if conn.mb != nil {
 112                 err := conn.mb.Close()
 113                 if err != nil {
 114                         conn.err("failed to remove some messages")
 115                         return
 116                 }
 117         }
 118         conn.ok("goodbye")
 119 }
 120
 121 func (conn *connection) doUSER() {
 122         if conn.state != stateAuth {
 123                 conn.err(errStateAuth)
 124                 return
 125         }
 126
 127         conn.user = conn.line[len("USER "):]
 128         conn.ok("")
 129 }
 130
 131 func (conn *connection) doPASS() {
 132         if conn.state != stateAuth {
 133                 conn.err(errStateAuth)
 134                 return
 135         }
 136
 137         if len(conn.user) == 0 {
 138                 conn.err("no USER")
 139                 return
 140         }
 141
 142         pass := conn.line[len("PASS "):]
 143         if mbox, err := conn.po.OpenMailbox(conn.user, pass); err == nil {
 144                 conn.log.Info("authenticated", zap.String("user", conn.user))
 145                 conn.state = stateTxn
 146                 conn.mb = mbox
 147                 conn.ok("")
 148         } else {
 149                 conn.log.Error("PASS", zap.Error(err))
 150                 conn.err(err.Error())
 151         }
 152 }
 153
 154 func (conn *connection) doSTAT() {
 155         if conn.state != stateTxn {
 156                 conn.err(errStateTxn)
 157                 return
 158         }
 159
 160         msgs, err := conn.mb.ListMessages()
 161         if err != nil {
 162                 conn.log.Error("STAT", zap.Error(err))
 163                 conn.err(err.Error())
 164                 return
 165         }
 166
 167         size := 0
 168         num := 0
 169         for _, msg := range msgs {
 170                 if msg.Deleted() {
 171                         continue
 172                 }
 173                 size += msg.Size()
 174                 num++
 175         }
 176
 177         conn.ok(fmt.Sprintf("%d %d", num, size))
 178 }
 179
 180 func (conn *connection) doLIST() {
 181         if conn.state != stateTxn {
 182                 conn.err(errStateTxn)
 183                 return
 184         }
 185
 186         msgs, err := conn.mb.ListMessages()
 187         if err != nil {
 188                 conn.log.Error("LIST", zap.Error(err))
 189                 conn.err(err.Error())
 190                 return
 191         }
 192
 193         conn.ok("scan listing")
 194         for _, msg := range msgs {
 195                 conn.tp.PrintfLine("%d %d", msg.ID(), msg.Size())
 196         }
 197         conn.tp.PrintfLine(".")
 198 }
 199
 200 func (conn *connection) doRETR() {
 201         if conn.state != stateTxn {
 202                 conn.err(errStateTxn)
 203                 return
 204         }
 205
 206         msg := conn.getRequestedMessage()
 207         if msg == nil {
 208                 return
 209         }
 210
 211         if msg.Deleted() {
 212                 conn.err(errDeletedMsg)
 213                 return
 214         }
 215
 216         rc, err := conn.mb.Retrieve(msg)
 217         if err != nil {
 218                 conn.log.Error("RETR", zap.Error(err))
 219                 conn.err(err.Error())
 220                 return
 221         }
 222
 223         conn.ok(fmt.Sprintf("%d", msg.Size()))
 224
 225         w := conn.tp.DotWriter()
 226         io.Copy(w, rc)
 227         w.Close()
 228 }
 229
 230 func (conn *connection) doDELE() {
 231         if conn.state != stateTxn {
 232                 conn.err(errStateTxn)
 233                 return
 234         }
 235
 236         msg := conn.getRequestedMessage()
 237         if msg == nil {
 238                 return
 239         }
 240
 241         if msg.Deleted() {
 242                 conn.err(errDeletedMsg)
 243                 return
 244         }
 245
 246         if err := conn.mb.Delete(msg); err != nil {
 247                 conn.log.Error("DELE", zap.Error(err))
 248                 conn.err(err.Error())
 249         } else {
 250                 conn.ok("")
 251         }
 252 }
 253
 254 func (conn *connection) doRSET() {
 255         if conn.state != stateTxn {
 256                 conn.err(errStateTxn)
 257                 return
 258         }
 259         conn.mb.Reset()
 260         conn.ok("")
 261 }
 262
 263 func (conn *connection) getRequestedMessage() Message {
 264         var cmd string
 265         var idx int
 266         if _, err := fmt.Sscanf(conn.line, "%s %d", &cmd, &idx); err != nil {
 267                 conn.err(errSyntax)
 268                 return nil
 269         }
 270
 271         if idx < 1 {
 272                 conn.err("invalid message-number")
 273                 return nil
 274         }
 275
 276         msg := conn.mb.GetMessage(idx)
 277         if msg == nil {
 278                 conn.err("no such message")
 279                 return nil
 280         }
 281         return msg
 282 }