Log when server sees alert record from tlsmasq origin (#495)

go.mod

@@ -46,7 +46,8 @@ require (
 	github.com/getlantern/ring v0.0.0-20181206150603-dd46ce8faa01 // indirect
 	github.com/getlantern/tinywss v0.0.0-20200121221108-851921f95ad7
 	github.com/getlantern/tlsdefaults v0.0.0-20171004213447-cf35cfd0b1b4
-	github.com/getlantern/tlsmasq v0.4.5
+	github.com/getlantern/tlsmasq v0.4.6
+	github.com/getlantern/tlsutil v0.5.1
 	github.com/getlantern/waitforserver v1.0.1
 	github.com/getlantern/withtimeout v0.0.0-20160829163843-511f017cd913
 	github.com/go-redis/redis/v8 v8.10.0

go.sum

@@ -290,11 +290,11 @@ github.com/getlantern/tinywss v0.0.0-20200121221108-851921f95ad7 h1:wVcJbQS7pf4h
 github.com/getlantern/tinywss v0.0.0-20200121221108-851921f95ad7/go.mod h1:ZLyPOKtNWU4vWnAiRiNQ7hbfLMqCEuj1DgQWBtHp7tQ=
 github.com/getlantern/tlsdefaults v0.0.0-20171004213447-cf35cfd0b1b4 h1:73U3J4msGw3cXeKtCEbY7hbOdD6aX8gJv8BOu+VagF8=
 github.com/getlantern/tlsdefaults v0.0.0-20171004213447-cf35cfd0b1b4/go.mod h1:f8WmDYKFOaC5/y0d3GWl6UKf1ZbSlIoMzkuC8x7pUhg=
-github.com/getlantern/tlsmasq v0.4.5 h1:dFh3AxZdicyo8Sqy1/iZLpWiGuJGew43SKaVSL7o6QA=
-github.com/getlantern/tlsmasq v0.4.5/go.mod h1:qgXekW+O2Eag1/hsAndpV/xdY1XXZaoIj7FhXskbxdY=
+github.com/getlantern/tlsmasq v0.4.6 h1:yk+XnAgB9XofhJ9leFR/SotRlLLtS2vElvjB43Xjn7E=
+github.com/getlantern/tlsmasq v0.4.6/go.mod h1:If80SpH0K1QvlZ5xeLlp3Vba73s8r1aCZzSmQNKN/pY=
 github.com/getlantern/tlsredis v0.0.0-20180308045249-5d4ed6dd3836/go.mod h1:1ZJE0mXEdPyyuF1daUTDBo2nVWB/6nuZy7IcNmRnHrc=
-github.com/getlantern/tlsutil v0.5.0 h1:VNQMXW3oMtPDSNyeTLk+MaU8FGkusNxwARJ30sR7yPw=
-github.com/getlantern/tlsutil v0.5.0/go.mod h1:lVgvr4nxuQ1ocOho90UB6LnHFlpP16TXAGpHR8Z0QnI=
+github.com/getlantern/tlsutil v0.5.1 h1:Cn19aDidw4+yufrQaCAYjZir3g1QaObs1xf4qzez3CA=
+github.com/getlantern/tlsutil v0.5.1/go.mod h1:lVgvr4nxuQ1ocOho90UB6LnHFlpP16TXAGpHR8Z0QnI=
 github.com/getlantern/utls v0.0.0-20200903013459-0c02248f7ce1 h1:+Egmu6VMMPm8/FHz8TOtQ1Usn3zg0gkS7ZHrLFycyok=
 github.com/getlantern/utls v0.0.0-20200903013459-0c02248f7ce1/go.mod h1:81/JblRrFcHdL/b50CIN3OuJmkt41KbgnjQu+mBSbgQ=
 github.com/getlantern/uuid v1.1.2-0.20190507182000-5c9436b8c718/go.mod h1:uX10hOzZUUDR+oYNSIks+RcozOEiwTNC/K2rw9SUi1k=

tlsmasq/tlsmasq.go

@@ -4,13 +4,19 @@ import (
 	"context"
 	"crypto/tls"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"net"
+	"sync"
 
+	"github.com/getlantern/golog"
 	"github.com/getlantern/tlsmasq"
 	"github.com/getlantern/tlsmasq/ptlshs"
+	"github.com/getlantern/tlsutil"
 )
 
+var log = golog.LoggerFor("tlsmasq-listener")
+
 func Wrap(ll net.Listener, certFile string, keyFile string, originAddr string, secret string,
 	tlsMinVersion uint16, tlsCipherSuites []uint16, onNonFatalErrors func(error)) (net.Listener, error) {
 
@@ -51,5 +57,45 @@ func Wrap(ll net.Listener, certFile string, keyFile string, originAddr string, s
 		},
 	}
 
-	return tlsmasq.WrapListener(ll, listenerCfg), nil
+	return wrapListener(ll, listenerCfg), nil
+}
+
+type loggingListener struct {
+	tlsmasqListener net.Listener
+}
+
+func wrapListener(transportListener net.Listener, cfg tlsmasq.ListenerConfig) net.Listener {
+	return loggingListener{tlsmasq.WrapListener(transportListener, cfg)}
+}
+
+func (l loggingListener) Accept() (net.Conn, error) {
+	conn, err := l.tlsmasqListener.Accept()
+	if err != nil {
+		return nil, err
+	}
+	return loggingConn{Conn: conn.(tlsmasq.Conn)}, nil
+}
+
+func (l loggingListener) Addr() net.Addr { return l.tlsmasqListener.Addr() }
+func (l loggingListener) Close() error   { return l.tlsmasqListener.Close() }
+
+type loggingConn struct {
+	tlsmasq.Conn
+	handshakeOnce sync.Once
+}
+
+func (conn loggingConn) Read(b []byte) (n int, err error)  { return conn.doIO(b, conn.Conn.Read) }
+func (conn loggingConn) Write(b []byte) (n int, err error) { return conn.doIO(b, conn.Conn.Write) }
+
+func (conn loggingConn) doIO(b []byte, io func([]byte) (int, error)) (n int, err error) {
+	conn.handshakeOnce.Do(func() {
+		var alertErr tlsutil.UnexpectedAlertError
+		if err = conn.Handshake(); err != nil && errors.As(err, &alertErr) {
+			log.Debugf("received alert from origin in tlsmasq handshake: %v", alertErr.Alert)
+		}
+	})
+	if err != nil {
+		return 0, err
+	}
+	return io(b)
 }