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add two new log levels for tracing sensitive auth protocol messages, and bulk data messages

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named "traceauth" and "tracedata".

with this, you can (almost) enable trace logging without fear of logging
sensitive data or ddos'ing your log server.

the caveat is that the imap login command has already printed the line as
regular trace before we can decide it should not be. can be fixed soon.
This commit is contained in:
Mechiel Lukkien
2023-02-03 20:33:19 +01:00
parent ae60cdac7e
commit ffb2a10a4e
10 changed files with 173 additions and 61 deletions
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37
smtpserver/server.go
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@ -203,6 +203,8 @@ type conn struct {
resolver dns.Resolver
r *bufio.Reader
w *bufio.Writer
tr *moxio.TraceReader // Kept for changing trace level during cmd/auth/data.
tw *moxio.TraceWriter
lastlog time.Time // Used for printing the delta time since the previous logging for this connection.
submission bool // ../rfc/6409:19 applies
tlsConfig *tls.Config
@ -292,6 +294,17 @@ func (c *conn) xcheckAuth() {
}
}
func (c *conn) xtrace(level mlog.Level) func() {
c.xflush()
c.tr.SetTrace(level)
c.tw.SetTrace(level)
return func() {
c.xflush()
c.tr.SetTrace(mlog.LevelTrace)
c.tw.SetTrace(mlog.LevelTrace)
}
}
// Write writes to the connection. It panics on i/o errors, which is handled by the
// connection command loop.
func (c *conn) Write(buf []byte) (int, error) {
@ -447,8 +460,10 @@ func serve(listenerName string, cid int64, hostname dns.Domain, tlsConfig *tls.C
}
return l
})
c.r = bufio.NewReader(moxio.NewTraceReader(c.log, "RC: ", c))
c.w = bufio.NewWriter(moxio.NewTraceWriter(c.log, "LS: ", c))
c.tr = moxio.NewTraceReader(c.log, "RC: ", c)
c.tw = moxio.NewTraceWriter(c.log, "LS: ", c)
c.r = bufio.NewReader(c.tr)
c.w = bufio.NewWriter(c.tw)
metricConnection.WithLabelValues(c.kind()).Inc()
c.log.Info("new connection", mlog.Field("remote", c.conn.RemoteAddr()), mlog.Field("local", c.conn.LocalAddr()), mlog.Field("submission", submission), mlog.Field("tls", tls), mlog.Field("listener", listenerName))
@ -714,8 +729,10 @@ func (c *conn) cmdStarttls(p *parser) {
tlsversion, ciphersuite := mox.TLSInfo(tlsConn)
c.log.Debug("tls server handshake done", mlog.Field("tls", tlsversion), mlog.Field("ciphersuite", ciphersuite))
c.conn = tlsConn
c.r = bufio.NewReader(moxio.NewTraceReader(c.log, "RC: ", c))
c.w = bufio.NewWriter(moxio.NewTraceWriter(c.log, "LS: ", c))
c.tr = moxio.NewTraceReader(c.log, "RC: ", c)
c.tw = moxio.NewTraceWriter(c.log, "LS: ", c)
c.r = bufio.NewReader(c.tr)
c.w = bufio.NewWriter(c.tw)
c.reset() // ../rfc/3207:210
c.tls = true
@ -814,7 +831,10 @@ func (c *conn) cmdAuth(p *parser) {
xsmtpUserErrorf(smtp.C538EncReqForAuth, smtp.SePol7EncReqForAuth11, "authentication requires tls")
}
// Password is in line in plain text, so hide it.
defer c.xtrace(mlog.LevelTraceauth)()
buf := xreadInitial()
c.xtrace(mlog.LevelTrace) // Restore.
plain := bytes.Split(buf, []byte{0})
if len(plain) != 3 {
xsmtpUserErrorf(smtp.C501BadParamSyntax, smtp.SeProto5BadParams4, "auth data should have 3 nul-separated tokens, got %d", len(plain))
@ -847,6 +867,8 @@ func (c *conn) cmdAuth(p *parser) {
authVariant = "scram-sha-256"
// Passwords cannot be retrieved or replayed from the trace.
c0 := xreadInitial()
ss, err := scram.NewServer(c0)
xcheckf(err, "starting scram")
@ -1208,6 +1230,9 @@ func (c *conn) cmdData(p *parser) {
// ../rfc/5321:1994
c.writelinef("354 see you at the bare dot")
// Mark as tracedata.
defer c.xtrace(mlog.LevelTracedata)()
// We read the data into a temporary file. We limit the size and do basic analysis while reading.
dataFile, err := store.CreateMessageTemp("smtp-deliver")
if err != nil {
@ -1223,7 +1248,9 @@ func (c *conn) cmdData(p *parser) {
}()
msgWriter := &message.Writer{Writer: dataFile}
dr := smtp.NewDataReader(c.r)
if n, err := io.Copy(&limitWriter{maxSize: c.maxMessageSize, w: msgWriter}, dr); err != nil {
n, err := io.Copy(&limitWriter{maxSize: c.maxMessageSize, w: msgWriter}, dr)
c.xtrace(mlog.LevelTrace) // Restore.
if err != nil {
if errors.Is(err, errMessageTooLarge) {
// ../rfc/1870:136 and ../rfc/3463:382
ecode := smtp.SeSys3MsgLimitExceeded4