mirror of
https://github.com/jhillyerd/inbucket.git
synced 2025-12-17 17:47:03 +00:00
362 lines
8.9 KiB
Go
362 lines
8.9 KiB
Go
package smtpd
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import (
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"bufio"
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"container/list"
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"fmt"
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"net"
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"strings"
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"time"
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)
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type State int
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const (
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GREET State = iota // Waiting for HELO
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READY // Got HELO, waiting for MAIL
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MAIL // Got MAIL, accepting RCPTs
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DATA // Got DATA, waiting for "."
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QUIT // Close session
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)
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func (s State) String() string {
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switch s {
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case GREET:
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return "GREET"
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case READY:
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return "READY"
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case MAIL:
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return "MAIL"
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case DATA:
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return "DATA"
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case QUIT:
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return "QUIT"
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}
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return "Unknown"
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}
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var commands = map[string] bool {
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"HELO": true,
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"MAIL": true,
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"RCPT": true,
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"DATA": true,
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"RSET": true,
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"SEND": true,
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"SOML": true,
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"SAML": true,
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"VRFY": true,
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"EXPN": true,
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"HELP": true,
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"NOOP": true,
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"QUIT": true,
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"TURN": true,
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}
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type Session struct {
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server *Server
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id int
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conn net.Conn
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sendError error
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state State
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reader *bufio.Reader
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from string
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recipients *list.List
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}
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func NewSession(server *Server, id int, conn net.Conn) *Session {
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reader := bufio.NewReader(conn)
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return &Session{server: server, id: id, conn: conn, state: GREET, reader: reader}
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}
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func (ss *Session) String() string {
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return fmt.Sprintf("Session{id: %v, state: %v}", ss.id, ss.state)
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}
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/* Session flow:
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* 1. Send initial greeting
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* 2. Receive cmd
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* 3. If good cmd, respond, optionally change state
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* 4. If bad cmd, respond error
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* 5. Goto 2
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*/
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func (s *Server) startSession(id int, conn net.Conn) {
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s.trace("Starting session <%v>", id)
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defer conn.Close()
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ss := NewSession(s, id, conn)
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ss.greet()
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// This is our command reading loop
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for ss.state != QUIT && ss.sendError == nil {
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if ss.state == DATA {
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// Special case, does not use SMTP command format
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ss.dataHandler()
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continue
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}
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line, err := ss.readLine()
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if err == nil {
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if cmd, arg, ok := ss.parseCmd(line); ok {
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// Check against valid SMTP commands
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if cmd == "" {
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ss.send("500 Speak up")
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continue
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}
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if !commands[cmd] {
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ss.send(fmt.Sprintf("500 Syntax error, %v command unrecognized", cmd))
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continue
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}
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// Commands we handle in any state
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switch cmd {
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case "SEND", "SOML", "SAML", "VRFY", "EXPN", "HELP", "TURN":
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// These commands are not implemented in any state
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ss.send(fmt.Sprintf("502 %v command not implemented", cmd))
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ss.warn("Command %v not implemented by Inbucket", cmd)
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continue
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case "NOOP":
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ss.send("250 I have sucessfully done nothing")
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continue
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case "RSET":
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// Reset session
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ss.reset()
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continue
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case "QUIT":
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ss.send("221 Goodnight and good luck")
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ss.enterState(QUIT)
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continue
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}
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// Send command to handler for current state
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switch ss.state {
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case GREET:
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ss.greetHandler(cmd, arg)
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continue
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case READY:
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ss.readyHandler(cmd, arg)
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continue
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case MAIL:
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ss.mailHandler(cmd, arg)
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continue
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}
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ss.error("Session entered unexpected state %v", ss.state)
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break
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} else {
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ss.send("500 Syntax error, command garbled")
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}
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} else {
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// readLine() returned an error
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ss.error("Connection error: %v", err)
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if netErr, ok := err.(net.Error); ok {
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if netErr.Timeout() {
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ss.send("221 Idle timeout, bye bye")
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break
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}
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}
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ss.send("221 Connection error, sorry")
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break
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}
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}
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if ss.sendError != nil {
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ss.error("Network send error: %v", ss.sendError)
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}
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ss.info("Closing connection")
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}
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// GREET state -> waiting for HELO
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func (ss *Session) greetHandler(cmd string, arg string) {
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if cmd == "HELO" {
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ss.send("250 Great, let's get this show on the road")
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ss.enterState(READY)
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} else {
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ss.ooSeq(cmd)
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}
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}
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// READY state -> waiting for MAIL
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func (ss *Session) readyHandler(cmd string, arg string) {
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if cmd == "MAIL" {
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if (len(arg) < 6) || (strings.ToUpper(arg[0:5]) != "FROM:") {
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ss.send("501 Was expecting MAIL arg syntax of FROM:<address>")
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ss.warn("Bad MAIL argument: \"%v\"", arg)
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return
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}
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// This trim is probably too forgiving
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from := strings.Trim(arg[5:], "<> ")
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ss.from = from
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ss.recipients = list.New()
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ss.info("Mail from: %v", from)
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ss.send(fmt.Sprintf("250 Roger, accepting mail from <%v>", from))
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ss.enterState(MAIL)
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} else {
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ss.ooSeq(cmd)
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}
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}
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// MAIL state -> waiting for RCPTs followed by DATA
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func (ss *Session) mailHandler(cmd string, arg string) {
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switch cmd {
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case "RCPT":
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if (len(arg) < 4) || (strings.ToUpper(arg[0:3]) != "TO:") {
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ss.send("501 Was expecting RCPT arg syntax of TO:<address>")
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ss.warn("Bad RCPT argument: \"%v\"", arg)
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return
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}
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// This trim is probably too forgiving
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recip := strings.Trim(arg[3:], "<> ")
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if ss.recipients.Len() >= ss.server.maxRecips {
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ss.warn("Maximum limit of %v recipients reached", ss.server.maxRecips)
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ss.send(fmt.Sprintf("552 Maximum limit of %v recipients reached", ss.server.maxRecips))
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return
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}
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ss.recipients.PushBack(recip)
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ss.info("Recipient: %v", recip)
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ss.send(fmt.Sprintf("250 I'll make sure <%v> gets this", recip))
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return
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case "DATA":
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if arg != "" {
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ss.send("501 DATA command should not have any arguments")
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ss.warn("Got unexpected args on DATA: \"%v\"", arg)
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return
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}
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if ss.recipients.Len() > 0 {
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// We have recipients, go to accept data
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ss.enterState(DATA)
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return
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} else {
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// DATA out of sequence
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ss.ooSeq(cmd)
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return
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}
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}
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ss.ooSeq(cmd)
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}
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// DATA
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func (ss *Session) dataHandler() {
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var msgSize uint64 = 0
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ss.send("354 Start mail input; end with <CRLF>.<CRLF>")
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for {
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line, err := ss.readLine()
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if err != nil {
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if netErr, ok := err.(net.Error); ok {
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if netErr.Timeout() {
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ss.send("221 Idle timeout, bye bye")
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}
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}
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ss.error("Error: %v while reading", err)
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ss.enterState(QUIT)
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return
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}
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if line == ".\r\n" || line == ".\n" {
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// Mail data complete
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ss.send("250 Mail accepted for delivery")
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ss.info("Message size %v bytes", msgSize)
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ss.enterState(READY)
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return
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}
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if line != "" && line[0] == '.' {
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line = line[1:]
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}
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msgSize += uint64(len(line))
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// TODO: Add variable line to something!
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}
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}
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func (ss *Session) enterState(state State) {
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ss.state = state
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ss.trace("Entering state %v", state)
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}
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func (ss *Session) greet() {
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ss.send(fmt.Sprintf("220 %v Inbucket SMTP ready", ss.server.domain))
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}
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// Calculate the next read or write deadline based on maxIdleSeconds
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func (ss *Session) nextDeadline() time.Time {
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return time.Now().Add(time.Duration(ss.server.maxIdleSeconds)*time.Second)
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}
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// Send requested message, store errors in Session.sendError
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func (ss *Session) send(msg string) {
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if err := ss.conn.SetWriteDeadline(ss.nextDeadline()); err != nil {
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ss.sendError = err
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return
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}
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if _, err := fmt.Fprint(ss.conn, msg + "\r\n"); err != nil {
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ss.sendError = err
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ss.error("Failed to send: \"%v\"", msg)
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return
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}
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ss.trace("Sent: \"%v\"", msg)
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}
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// Reads a line of input
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func (ss *Session) readLine() (line string, err error) {
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if err = ss.conn.SetReadDeadline(ss.nextDeadline()); err != nil {
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return "", err
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}
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line, err = ss.reader.ReadString('\n')
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if err != nil {
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return "", err
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}
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ss.trace("Read: \"%v\"", strings.TrimRight(line, "\r\n"))
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return line, nil
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}
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func (ss *Session) parseCmd(line string) (cmd string, arg string, ok bool) {
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line = strings.TrimRight(line, "\r\n")
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l := len(line)
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switch {
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case l == 0:
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return "", "", true
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case l < 4:
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ss.error("Command too short: \"%v\"", line)
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return "", "", false
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case l == 4:
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return strings.ToUpper(line), "", true
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case l == 5:
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// Too long to be only command, too short to have args
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ss.error("Mangled command: \"%v\"", line)
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return "", "", false
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}
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// If we made it here, command is long enough to have args
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if line[4] != ' ' {
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// There wasn't a space after the command?
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ss.error("Mangled command: \"%v\"", line)
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return "", "", false
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}
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// I'm not sure if we should trim the args or not, but we will for now
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return strings.ToUpper(line[0:4]), strings.Trim(line[5:], " "), true
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}
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func (ss *Session) reset() {
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ss.info("Resetting session state on RSET request")
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ss.enterState(READY)
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ss.from = ""
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ss.recipients = nil
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}
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func (ss *Session) ooSeq(cmd string) {
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ss.send(fmt.Sprintf("503 Command %v is out of sequence", cmd))
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ss.warn("Wasn't expecting %v here", cmd)
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}
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// Session specific logging methods
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func (ss *Session) trace(msg string, args ...interface {}) {
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ss.server.trace("<%v> %v", ss.id, fmt.Sprintf(msg, args...))
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}
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func (ss *Session) info(msg string, args ...interface {}) {
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ss.server.info("<%v> %v", ss.id, fmt.Sprintf(msg, args...))
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}
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func (ss *Session) warn(msg string, args ...interface {}) {
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ss.server.warn("<%v> %v", ss.id, fmt.Sprintf(msg, args...))
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}
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func (ss *Session) error(msg string, args ...interface {}) {
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ss.server.error("<%v> %v", ss.id, fmt.Sprintf(msg, args...))
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}
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