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conn.go
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package smtp
import (
"crypto/tls"
"encoding/base64"
"errors"
"fmt"
"io"
"io/ioutil"
"net"
"net/textproto"
"regexp"
"runtime/debug"
"strconv"
"strings"
"sync"
"time"
)
// Number of errors we'll tolerate per connection before closing. Defaults to 3.
const errThreshold = 3
type ConnectionState struct {
Hostname string
LocalAddr net.Addr
RemoteAddr net.Addr
TLS tls.ConnectionState
Original *ConnectionState
}
type Conn struct {
conn net.Conn
text *textproto.Conn
server *Server
helo string
nbrErrors int
// Number of errors witnessed on this connection
errCount int
session Session
locker sync.Mutex
binarymime bool
lineLimitReader *lineLimitReader
bdatPipe *io.PipeWriter
bdatStatus *statusCollector // used for BDAT on LMTP
dataResult chan error
bytesReceived int // counts total size of chunks when BDAT is used
fromReceived bool
recipients []string
// We store ConnectionState built from XCLIENT command as multiple commands can be sent with
// different fields.
xclientState *ConnectionState
// connection unique id
sid string
didAuth bool
}
func newConn(c net.Conn, s *Server) *Conn {
sc := &Conn{
server: s,
conn: c,
}
sc.init()
return sc
}
func (c *Conn) init() {
c.lineLimitReader = &lineLimitReader{
R: c.conn,
LineLimit: c.server.MaxLineLength,
}
rwc := struct {
io.Reader
io.Writer
io.Closer
}{
Reader: c.lineLimitReader,
Writer: c.conn,
Closer: c.conn,
}
if c.server.Debug != nil {
rwc = struct {
io.Reader
io.Writer
io.Closer
}{
io.TeeReader(rwc.Reader, c.server.Debug),
io.MultiWriter(rwc.Writer, c.server.Debug),
rwc.Closer,
}
}
c.text = textproto.NewConn(rwc)
}
func (c *Conn) unrecognizedCommand(cmd string) {
errMsg := fmt.Sprintf("Syntax error, %v command unrecognized", cmd)
c.WriteResponse(500, EnhancedCode{5, 5, 2}, errMsg)
c.server.Logger.Infof("smtp/server sid=%s reject: %s", c.sid, errMsg)
c.nbrErrors++
if c.nbrErrors > 3 {
c.WriteResponse(500, EnhancedCode{5, 5, 2}, "Too many unrecognized commands")
c.server.Logger.Infof("smtp/server sid=%s reject: too many unrecognized commands", c.sid)
c.Close()
}
}
// Commands are dispatched to the appropriate handler functions.
func (c *Conn) handle(cmd string, arg string) {
// If panic happens during command handling - send 421 response
// and close connection.
defer func() {
if err := recover(); err != nil {
c.WriteResponse(421, EnhancedCode{4, 0, 0}, "Internal server error")
c.Close()
stack := debug.Stack()
c.server.Logger.Errorf("smtp/server sid=%s panic: %v\n%s", c.sid, err, stack)
}
}()
if cmd == "" {
c.protocolError(500, EnhancedCode{5, 5, 2}, "Error: bad syntax")
c.server.Logger.Infof("smtp/server sid=%s reject: bad syntax", c.sid)
return
}
cmd = strings.ToUpper(cmd)
switch cmd {
case "SEND", "SOML", "SAML", "EXPN", "HELP", "TURN":
// These commands are not implemented in any state
errMsg := fmt.Sprintf("%v command not implemented", cmd)
c.server.Logger.Infof("smtp/server sid=%s reject: %s", c.sid, errMsg)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, errMsg)
case "HELO", "EHLO", "LHLO":
lmtp := cmd == "LHLO"
enhanced := lmtp || cmd == "EHLO"
if c.server.LMTP && !lmtp {
c.server.Logger.Infof("smtp/server sid=%s reject: this is a LMTP server, use LHLO", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 1}, "This is a LMTP server, use LHLO")
return
}
if !c.server.LMTP && lmtp {
c.server.Logger.Infof("smtp/server sid=%s reject: this is not a LMTP server", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 1}, "This is not a LMTP server")
return
}
c.handleGreet(enhanced, arg)
case "XCLIENT":
c.handleXclient(arg)
case "MAIL":
c.handleMail(arg)
case "RCPT":
c.handleRcpt(arg)
case "VRFY":
c.WriteResponse(252, EnhancedCode{2, 5, 0}, "Cannot VRFY user, but will accept message")
case "NOOP":
c.WriteResponse(250, EnhancedCode{2, 0, 0}, "I have sucessfully done nothing")
case "RSET": // Reset session
c.reset()
c.WriteResponse(250, EnhancedCode{2, 0, 0}, "Session reset")
case "BDAT":
c.handleBdat(arg)
case "DATA":
c.handleData(arg)
case "QUIT":
c.WriteResponse(221, EnhancedCode{2, 0, 0}, "Bye")
c.Close()
case "AUTH":
if c.server.AuthDisabled {
c.server.Logger.Infof("smtp/server sid=%s reject: syntax error, AUTH command unrecognized", c.sid)
c.protocolError(500, EnhancedCode{5, 5, 2}, "Syntax error, AUTH command unrecognized")
} else {
c.handleAuth(arg)
}
case "STARTTLS":
c.handleStartTLS()
default:
msg := fmt.Sprintf("Syntax errors, %v command unrecognized", cmd)
c.server.Logger.Infof("smtp/server sid=%s reject: %s", c.sid, msg)
c.protocolError(500, EnhancedCode{5, 5, 2}, msg)
}
}
func (c *Conn) Server() *Server {
return c.server
}
func (c *Conn) Session() Session {
c.locker.Lock()
defer c.locker.Unlock()
return c.session
}
// Setting the user resets any message being generated
func (c *Conn) SetSession(session Session) {
c.locker.Lock()
defer c.locker.Unlock()
c.session = session
}
func (c *Conn) Close() error {
c.locker.Lock()
defer c.locker.Unlock()
if c.bdatPipe != nil {
c.bdatPipe.CloseWithError(ErrDataReset)
c.bdatPipe = nil
}
if c.session != nil {
c.session.Logout()
c.session = nil
}
return c.conn.Close()
}
// TLSConnectionState returns the connection's TLS connection state.
// Zero values are returned if the connection doesn't use TLS.
func (c *Conn) TLSConnectionState() (state tls.ConnectionState, ok bool) {
tc, ok := c.conn.(*tls.Conn)
if !ok {
return
}
return tc.ConnectionState(), true
}
func (c *Conn) State() ConnectionState {
if c.xclientState != nil {
return *c.xclientState
}
state := ConnectionState{}
tlsState, ok := c.TLSConnectionState()
if ok {
state.TLS = tlsState
}
state.Hostname = c.helo
state.LocalAddr = c.conn.LocalAddr()
state.RemoteAddr = c.conn.RemoteAddr()
return state
}
func (c *Conn) authAllowed() bool {
_, isTLS := c.TLSConnectionState()
canAuthResult := !c.server.AuthDisabled && (isTLS || c.server.AllowInsecureAuth)
//check secure network
if !canAuthResult {
if addr, ok := c.State().RemoteAddr.(*net.TCPAddr); ok {
for _, ipNet := range c.server.SecureNet {
if ipNet.Contains(addr.IP) {
return true
}
}
}
}
return canAuthResult
}
// protocolError writes errors responses and closes the connection once too many
// have occurred.
func (c *Conn) protocolError(code int, ec EnhancedCode, msg string) {
c.WriteResponse(code, ec, msg)
c.errCount++
if c.errCount > errThreshold {
c.server.Logger.Infof("smtp/server sid=%s reject: too many errors, close connection", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 1}, "Too many errors. Quiting now")
c.Close()
}
}
// GREET state -> waiting for HELO
func (c *Conn) handleGreet(enhanced bool, arg string) {
domain, err := parseHelloArgument(arg)
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: HELO error", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 2}, "Domain/address argument required for HELO")
return
}
c.helo = domain
state := c.State()
sess, err := c.server.Backend.NewSession(&state, domain, c.sid)
if err != nil {
if smtpErr, ok := err.(*SMTPError); ok {
c.WriteResponse(smtpErr.Code, smtpErr.EnhancedCode, smtpErr.Message)
return
}
c.WriteResponse(451, EnhancedCode{4, 0, 0}, err.Error())
return
}
c.SetSession(sess)
if !enhanced {
c.WriteResponse(250, EnhancedCode{2, 0, 0}, fmt.Sprintf("Hello %s", domain))
return
}
caps := []string{}
caps = append(caps, c.server.caps...)
if _, isTLS := c.TLSConnectionState(); c.server.TLSConfig != nil && !isTLS {
caps = append(caps, "STARTTLS")
}
if c.authAllowed() {
authCap := "AUTH"
for name := range c.server.auths {
authCap += " " + name
}
caps = append(caps, authCap)
}
if c.server.EnableSMTPUTF8 {
caps = append(caps, "SMTPUTF8")
}
if _, isTLS := c.TLSConnectionState(); isTLS && c.server.EnableREQUIRETLS {
caps = append(caps, "REQUIRETLS")
}
if c.server.EnableBINARYMIME {
caps = append(caps, "BINARYMIME")
}
if c.server.EnableDSN {
caps = append(caps, "DSN")
}
if c.server.MaxMessageBytes > 0 {
caps = append(caps, fmt.Sprintf("SIZE %v", c.server.MaxMessageBytes))
} else {
caps = append(caps, "SIZE")
}
if _, ok := c.server.Backend.(ProxyBackend); ok {
// We list fields we can convert into ConnectionState plus PROTO that does not really matter in practice.
// Notable omission here is LOGIN for SASL username assertion and NAME which cannot be represented
// by ConnectionState fields.
caps = append(caps, "XCLIENT ADDR PORT DESTADDR DESTPORT HELO PROTO")
}
args := []string{"Hello " + domain}
args = append(args, caps...)
c.WriteResponse(250, NoEnhancedCode, args...)
}
// READY state -> waiting for MAIL
func (c *Conn) handleMail(arg string) {
if c.helo == "" {
c.server.Logger.Infof("smtp/server sid=%s reject: MAIL not allowed before HELO/EHLO", c.sid)
c.WriteResponse(502, EnhancedCode{2, 5, 1}, "Please introduce yourself first.")
return
}
if c.bdatPipe != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: MAIL not allowed during BDAT pipe", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "MAIL not allowed during message transfer")
return
}
if len(arg) < 6 || strings.ToUpper(arg[0:5]) != "FROM:" {
c.server.Logger.Infof("smtp/server sid=% reject: MAIL arg=%s syntax", c.sid, arg)
c.WriteResponse(501, EnhancedCode{5, 5, 2}, "Was expecting MAIL arg syntax of FROM:<address>")
return
}
fromArgs := strings.Split(strings.Trim(arg[5:], " "), " ")
if c.server.Strict {
if !strings.HasPrefix(fromArgs[0], "<") || !strings.HasSuffix(fromArgs[0], ">") {
c.server.Logger.Infof("smtp/server sid=%s reject: MAIL arg=%s syntax", c.sid, fromArgs)
c.WriteResponse(501, EnhancedCode{5, 5, 2}, "Was expecting MAIL arg syntax of FROM:<address>")
return
}
}
from := fromArgs[0]
if from == "" {
c.server.Logger.Infof("smtp/server sid=%s reject: MAIL FROM arg empty", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 2}, "Was expecting MAIL arg syntax of FROM:<address>")
return
}
from = strings.Trim(from, "<>")
opts := &MailOptions{}
c.binarymime = false
// This is where the Conn may put BODY=8BITMIME, but we already
// read the DATA as bytes, so it does not effect our processing.
if len(fromArgs) > 1 {
args, err := parseArgs(fromArgs[1:])
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: unable to parse MAIL ESMTP parameters", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Unable to parse MAIL ESMTP parameters")
return
}
for key, value := range args {
switch key {
case "SIZE":
size, err := strconv.ParseInt(value, 10, 32)
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: unable to parse SIZE as an integer", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Unable to parse SIZE as an integer")
return
}
if c.server.MaxMessageBytes > 0 && int(size) > c.server.MaxMessageBytes {
c.server.Logger.Infof("smtp/server sid=%s reject: max message size=%d exceeded", c.sid, size)
c.WriteResponse(552, EnhancedCode{5, 3, 4}, "Max message size exceeded")
return
}
opts.Size = int(size)
case "SMTPUTF8":
if !c.server.EnableSMTPUTF8 {
c.server.Logger.Infof("smtp/server sid=%s reject: SMTPUTF8 is not implemented", c.sid)
c.WriteResponse(504, EnhancedCode{5, 5, 4}, "SMTPUTF8 is not implemented")
return
}
opts.UTF8 = true
case "REQUIRETLS":
if !c.server.EnableREQUIRETLS {
c.server.Logger.Infof("smtp/server sid=%s reject: REQUIRETLS is not implemented", c.sid)
c.WriteResponse(504, EnhancedCode{5, 5, 4}, "REQUIRETLS is not implemented")
return
}
opts.RequireTLS = true
case "BODY":
switch value {
case "BINARYMIME":
if !c.server.EnableBINARYMIME {
c.server.Logger.Infof("smtp/server sid=%s reject: BINARYMIME is not implemented", c.sid)
c.WriteResponse(504, EnhancedCode{5, 5, 4}, "BINARYMIME is not implemented")
return
}
c.binarymime = true
case "7BIT", "8BITMIME":
default:
c.server.Logger.Infof("smtp/server sid=%s reject: Unknown BODY value", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 4}, "Unknown BODY value")
return
}
opts.Body = BodyType(value)
case "AUTH":
value, err := decodeXtext(value)
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: malformed AUTH parameter value", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 4}, "Malformed AUTH parameter value")
return
}
if !strings.HasPrefix(value, "<") {
c.server.Logger.Infof("smtp/server sid=%s reject: missing opening angle bracket", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 4}, "Missing opening angle bracket")
return
}
if !strings.HasSuffix(value, ">") {
c.server.Logger.Infof("smtp/server sid=%s reject: missing closing angle bracket", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 4}, "Missing closing angle bracket")
return
}
decodedMbox := value[1 : len(value)-1]
opts.Auth = &decodedMbox
case "RET":
value := DSNReturn(strings.ToUpper(value))
if value != ReturnFull && value != ReturnHeaders {
c.server.Logger.Infof("smtp/server sid=%s reject: missing closing angle bracket", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Unsupported RET value")
return
}
opts.Return = value
case "ENVID":
value, err := decodeXtext(value)
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: malformed xtext in ENVID", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Malformed xtext in ENVID")
return
}
if !checkPrintableASCII(value) {
c.server.Logger.Infof("smtp/server sid=%s reject: only printable ASCII allowed in ENVID", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Only printable ASCII allowed in ENVID")
return
}
opts.EnvelopeID = value
default:
c.server.Logger.Infof("smtp/server sid=%s reject: unknown MAIL FROM argument", c.sid)
c.WriteResponse(500, EnhancedCode{5, 5, 4}, "Unknown MAIL FROM argument")
return
}
}
}
if err := c.Session().Mail(from, opts); err != nil {
if smtpErr, ok := err.(*SMTPError); ok {
c.WriteResponse(smtpErr.Code, smtpErr.EnhancedCode, smtpErr.Message)
return
}
c.WriteResponse(451, EnhancedCode{4, 0, 0}, err.Error())
return
}
c.WriteResponse(250, EnhancedCode{2, 0, 0}, fmt.Sprintf("Roger, accepting mail from <%v>", from))
c.fromReceived = true
}
// This regexp matches 'hexchar' token defined in
// https://tools.ietf.org/html/rfc4954#section-8 however it is intentionally
// relaxed by requiring only '+' to be present. It allows us to detect
// malformed values such as +A or +HH and report them appropriately.
var hexcharRe = regexp.MustCompile(`\+[0-9A-F]?[0-9A-F]?`)
func decodeXtext(val string) (string, error) {
if !strings.Contains(val, "+") {
return val, nil
}
var replaceErr error
decoded := hexcharRe.ReplaceAllStringFunc(val, func(match string) string {
if len(match) != 3 {
replaceErr = errors.New("incomplete hexchar")
return ""
}
char, err := strconv.ParseInt(match, 16, 8)
if err != nil {
replaceErr = err
return ""
}
return string(rune(char))
})
if replaceErr != nil {
return "", replaceErr
}
return decoded, nil
}
func encodeXtext(raw string) string {
var out strings.Builder
out.Grow(len(raw))
for _, ch := range raw {
if ch == '+' || ch == '=' {
out.WriteRune('+')
out.WriteString(strings.ToUpper(strconv.FormatInt(int64(ch), 16)))
}
if ch > '!' && ch < '~' { // printable non-space US-ASCII
out.WriteRune(ch)
}
// Non-ASCII.
out.WriteRune('+')
out.WriteString(strings.ToUpper(strconv.FormatInt(int64(ch), 16)))
}
return out.String()
}
func checkPrintableASCII(s string) bool {
for _, c := range s {
if c < 32 && c > 127 {
return false
}
}
return true
}
// MAIL state -> waiting for RCPTs followed by DATA
func (c *Conn) handleRcpt(arg string) {
if !c.fromReceived {
c.server.Logger.Infof("smtp/server sid=%s reject: missing MAIL FROM command", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "Missing MAIL FROM command.")
return
}
if c.bdatPipe != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: RCPT not allowed during message transfer", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "RCPT not allowed during message transfer")
return
}
if len(arg) < 4 || strings.ToUpper(arg[0:3]) != "TO:" {
c.server.Logger.Infof("smtp/server sid=%s reject: RCPT TO arg=%s syntax error", c.sid, arg)
c.WriteResponse(501, EnhancedCode{5, 5, 1}, "Was expecting TO arg syntax of TO:<address>")
return
}
toArgs := strings.Split(strings.Trim(arg[3:], " "), " ")
if c.server.Strict {
if !strings.HasPrefix(toArgs[0], "<") || !strings.HasSuffix(toArgs[0], ">") {
c.server.Logger.Infof("smtp/server sid=%s reject: RCPT TO arg=%s syntax error", c.sid, arg)
c.WriteResponse(501, EnhancedCode{5, 5, 1}, "Was expecting TO arg syntax of TO:<address>")
return
}
}
recipient := toArgs[0]
if recipient == "" {
c.server.Logger.Infof("smtp/server sid=%s reject: missing RCPT TO parameter", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 2}, "Was expecting RCPT TO arg syntax of TO:<address>")
return
}
recipient = strings.Trim(recipient, "<>")
if c.server.MaxRecipients > 0 && len(c.recipients) >= c.server.MaxRecipients {
c.server.Logger.Infof("smtp/server sid=%s reject: recipients max-limit=%d reached", c.sid, c.server.MaxRecipients)
c.WriteResponse(552, EnhancedCode{5, 5, 3}, fmt.Sprintf("Maximum limit of %v recipients reached", c.server.MaxRecipients))
return
}
opts := RcptOptions{}
if len(toArgs) > 1 {
args, err := parseArgs(toArgs[1:])
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: unable to parse TO ESMTP parameters", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Unable to parse TO ESMTP parameters")
return
}
for key, value := range args {
switch key {
case "ORCPT":
case "NOTIFY":
notifyFlags := strings.Split(strings.ToUpper(value), ",")
seenFlags := make(map[string]struct{})
for _, f := range notifyFlags {
if _, ok := seenFlags[f]; ok {
c.server.Logger.Infof("smtp/server sid=%s reject: NOTIFY parameters cannot be specified multiple times", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "NOTIFY parameters cannot be specified multiple times")
return
}
switch DSNNotify(f) {
case NotifyNever:
if len(notifyFlags) != 1 {
c.server.Logger.Infof("smtp/server sid=%s reject: NOTIFY=NEVER cannot be combined with other options", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "NOTIFY=NEVER cannot be combined with other options")
return
}
case NotifyDelayed, NotifySuccess, NotifyFailure:
default:
c.server.Logger.Infof("smtp/server sid=%s reject: unknown NOTIFY parameter", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Unknown NOTIFY parameter")
return
}
seenFlags[f] = struct{}{}
opts.Notify = append(opts.Notify, DSNNotify(f))
}
}
}
}
if err := c.Session().Rcpt(recipient, RcptOptions{}); err != nil {
if smtpErr, ok := err.(*SMTPError); ok {
c.WriteResponse(smtpErr.Code, smtpErr.EnhancedCode, smtpErr.Message)
return
}
c.WriteResponse(451, EnhancedCode{4, 0, 0}, err.Error())
return
}
c.recipients = append(c.recipients, recipient)
c.WriteResponse(250, EnhancedCode{2, 0, 0}, fmt.Sprintf("I'll make sure <%v> gets this", recipient))
}
func (c *Conn) handleAuth(arg string) {
if c.helo == "" {
c.server.Logger.Infof("smtp/server sid=%s reject: AUTH not allowed before HELO/EHLO", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "Please introduce yourself first.")
return
}
if c.didAuth {
c.server.Logger.Infof("smtp/server sid=%s reject: already authenticated", c.sid)
c.WriteResponse(503, EnhancedCode{5, 5, 1}, "Already authenticated")
return
}
parts := strings.Fields(arg)
if len(parts) == 0 {
c.server.Logger.Infof("smtp/server sid=%s reject: missing AUTH parameter", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 4}, "Missing parameter")
return
}
if !c.authAllowed() {
c.server.Logger.Infof("smtp/server sid=%s reject: auth on insecure connection", c.sid)
c.WriteResponse(523, EnhancedCode{5, 7, 10}, "Secure connection is required")
return
}
mechanism := strings.ToUpper(parts[0])
// Parse client initial response if there is one
var ir []byte
if len(parts) > 1 {
var err error
ir, err = base64.StdEncoding.DecodeString(parts[1])
if err != nil {
return
}
}
newSasl, ok := c.server.auths[mechanism]
if !ok {
c.server.Logger.Infof("smtp/server sid=%s reject: unsupported authentication mechanism", c.sid)
c.WriteResponse(504, EnhancedCode{5, 7, 4}, "Unsupported authentication mechanism")
return
}
sasl := newSasl(c)
response := ir
for {
challenge, done, err := sasl.Next(response)
if err != nil {
if smtpErr, ok := err.(*SMTPError); ok {
c.WriteResponse(smtpErr.Code, smtpErr.EnhancedCode, smtpErr.Message)
return
}
c.WriteResponse(454, EnhancedCode{4, 7, 0}, err.Error())
return
}
if done {
break
}
encoded := ""
if len(challenge) > 0 {
encoded = base64.StdEncoding.EncodeToString(challenge)
}
c.WriteResponse(334, NoEnhancedCode, encoded)
encoded, err = c.ReadLine()
if err != nil {
return // TODO: error handling
}
if encoded == "*" {
c.server.Logger.Infof("smtp/server sid=%s reject: unsupported AUTH encoded", c.sid)
// https://tools.ietf.org/html/rfc4954#page-4
c.WriteResponse(501, EnhancedCode{5, 0, 0}, "Negotiation cancelled")
return
}
response, err = base64.StdEncoding.DecodeString(encoded)
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s softreject: invalid base64 data during AUTH", c.sid)
c.WriteResponse(454, EnhancedCode{4, 7, 0}, "Invalid base64 data")
return
}
}
c.WriteResponse(235, EnhancedCode{2, 0, 0}, "Authentication succeeded")
c.didAuth = true
}
func (c *Conn) handleStartTLS() {
if _, isTLS := c.TLSConnectionState(); isTLS {
c.server.Logger.Infof("smtp/server sid=%s reject: already running in TLS", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "Already running in TLS")
return
}
if c.server.TLSConfig == nil {
c.server.Logger.Infof("smtp/server sid=%s reject: STARTTLS not supported", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "TLS not supported")
return
}
c.WriteResponse(220, EnhancedCode{2, 0, 0}, "Ready to start TLS")
// Upgrade to TLS
tlsConn := tls.Server(c.conn, c.server.TLSConfig)
if err := tlsConn.Handshake(); err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: TLS handshake error %v", c.sid, err)
c.WriteResponse(550, EnhancedCode{5, 0, 0}, "Handshake error")
return
}
c.conn = tlsConn
c.init()
// Reset all state and close the previous Session.
// This is different from just calling reset() since we want the Backend to
// be able to see the information about TLS connection in the
// ConnectionState object passed to it.
if session := c.Session(); session != nil {
session.Logout()
c.SetSession(nil)
}
c.helo = ""
c.didAuth = false
c.reset()
}
// DATA
func (c *Conn) handleData(arg string) {
if arg != "" {
c.server.Logger.Infof("smtp/server sid=%s reject: DATA should not have any arguments", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "DATA command should not have any arguments")
return
}
if c.bdatPipe != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: DATA not allowed during message transfer", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "DATA not allowed during message transfer")
return
}
if c.binarymime {
c.server.Logger.Infof("smtp/server sid=%s reject: DATA not allowed for BINARYMIME messages", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "DATA not allowed for BINARYMIME messages")
return
}
if !c.fromReceived || len(c.recipients) == 0 {
c.server.Logger.Infof("smtp/server sid=%s reject: DATA missing RCPT TO command", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "Missing RCPT TO command")
return
}
// We have recipients, go to accept data
c.WriteResponse(354, EnhancedCode{2, 0, 0}, "Go ahead. End your data with <CR><LF>.<CR><LF>")
defer c.reset()
if c.server.LMTP {
c.handleDataLMTP()
return
}
r := newDataReader(c)
code, enhancedCode, msg := toSMTPStatus(c.Session().Data(r))
r.limited = false
io.Copy(ioutil.Discard, r) // Make sure all the data has been consumed
c.WriteResponse(code, enhancedCode, msg)
}
func (c *Conn) handleBdat(arg string) {
args := strings.Fields(arg)
if len(args) == 0 {
c.server.Logger.Infof("smtp/server sid=%s reject: BDAT missing chunk size argument", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Missing chunk size argument")
return
}
if len(args) > 2 {
c.server.Logger.Infof("smtp/server sid=%s reject: BDAT too many arguments", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Too many arguments")
return
}
if !c.fromReceived || len(c.recipients) == 0 {
c.server.Logger.Infof("smtp/server sid=%s reject: BDAT missing RCPT TO command", c.sid)
c.WriteResponse(502, EnhancedCode{5, 5, 1}, "Missing RCPT TO command")
return
}
last := false
if len(args) == 2 {
if !strings.EqualFold(args[1], "LAST") {
c.server.Logger.Infof("smtp/server sid=%s reject: unknown BDAT argument", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Unknown BDAT argument")
return
}
last = true
}
// ParseUint instead of Atoi so we will not accept negative values.
size, err := strconv.ParseUint(args[0], 10, 32)
if err != nil {
c.server.Logger.Infof("smtp/server sid=%s reject: BDAT malformed size argument", c.sid)
c.WriteResponse(501, EnhancedCode{5, 5, 4}, "Malformed size argument")
return
}
if c.server.MaxMessageBytes != 0 && c.bytesReceived+int(size) > c.server.MaxMessageBytes {
c.server.Logger.Infof("smtp/server sid=%s reject: BDAT message size=%d exceeded %d", c.sid, c.bytesReceived+int(size), c.server.MaxMessageBytes)
c.WriteResponse(552, EnhancedCode{5, 3, 4}, "Max message size exceeded")
// Discard chunk itself without passing it to backend.
io.Copy(ioutil.Discard, io.LimitReader(c.text.R, int64(size)))
c.reset()
return
}
if c.bdatStatus == nil && c.server.LMTP {
c.bdatStatus = c.createStatusCollector()
}
if c.bdatPipe == nil {
var r *io.PipeReader
r, c.bdatPipe = io.Pipe()
c.dataResult = make(chan error, 1)
go func() {
defer func() {
if err := recover(); err != nil {
c.handlePanic(err, c.bdatStatus)
c.dataResult <- errPanic
r.CloseWithError(errPanic)
}
}()
var err error
if !c.server.LMTP {
err = c.Session().Data(r)
} else {
lmtpSession, ok := c.Session().(LMTPSession)
if !ok {
err = c.Session().Data(r)
for _, rcpt := range c.recipients {
c.bdatStatus.SetStatus(rcpt, err)
}
} else {
err = lmtpSession.LMTPData(r, c.bdatStatus)
}
}
c.dataResult <- err
r.CloseWithError(err)
}()
}
c.lineLimitReader.LineLimit = 0
chunk := io.LimitReader(c.text.R, int64(size))
_, err = io.Copy(c.bdatPipe, chunk)
if err != nil {
// Backend might return an error early using CloseWithError without consuming
// the whole chunk.
io.Copy(ioutil.Discard, chunk)
c.server.Logger.Warnf("smtp/server sid=%s reject: BDAT %s", c.sid, err.Error())
c.WriteResponse(toSMTPStatus(err))
if err == errPanic {
c.Close()
}
c.reset()
c.lineLimitReader.LineLimit = c.server.MaxLineLength
return
}
c.bytesReceived += int(size)
if last {
c.lineLimitReader.LineLimit = c.server.MaxLineLength
c.bdatPipe.Close()
err := <-c.dataResult
if c.server.LMTP {
c.bdatStatus.fillRemaining(err)
for i, rcpt := range c.recipients {
code, enchCode, msg := toSMTPStatus(<-c.bdatStatus.status[i])
c.WriteResponse(code, enchCode, "<"+rcpt+"> "+msg)
}
} else {
c.WriteResponse(toSMTPStatus(err))
}
if err == errPanic {
c.Close()
return
}
c.reset()
} else {
c.WriteResponse(250, EnhancedCode{2, 0, 0}, "Continue")
}
}
// ErrDataReset is returned by Reader pased to Data function if client does not
// send another BDAT command and instead closes connection or issues RSET command.
var ErrDataReset = errors.New("smtp: message transmission aborted")
var errPanic = &SMTPError{
Code: 421,
EnhancedCode: EnhancedCode{4, 0, 0},
Message: "Internal server error",
}
func (c *Conn) handlePanic(err interface{}, status *statusCollector) {
if status != nil {
status.fillRemaining(errPanic)
}
stack := debug.Stack()
c.server.Logger.Errorf("smtp/server sid=%s panic: %v\n%s", c.sid, err, stack)
}
func (c *Conn) createStatusCollector() *statusCollector {
rcptCounts := make(map[string]int, len(c.recipients))
status := &statusCollector{
statusMap: make(map[string]chan error, len(c.recipients)),
status: make([]chan error, 0, len(c.recipients)),
}