Add -tls-proxy-outbound-port flag to jafar (useful for non-HTTPS protocols)

Edit README to make it explicit that tlsproxy has nothing to do with HTTP and can be
used with any TCP protocol that does TLS handshakes.

internal/cmd/jafar/README.md

@@ -156,14 +156,16 @@ response for every request whose `Host` contains the specified string.
 
 ### tls-proxy
 
-TLS proxy is a proxy that routes traffic to specific servers depending
+TLS proxy is a TCP proxy that routes traffic to specific servers depending
 on their SNI value. It is controlled by the following flags:
 
 ```bash
   -tls-proxy-address string
-        Address where the HTTP proxy should listen (default "127.0.0.1:443")
+        Address where the TCP+TLS proxy should listen (default "127.0.0.1:443")
   -tls-proxy-block value
-        Register keyword triggering TLS censorship
+        Register SNI header keyword triggering TLS censorship
+  -tls-proxy-outbound-port
+        Define the outbound port requests are proxied to (default "443 for HTTPS)
 ```
 
 The `-tls-proxy-address` flags has the same semantics it has for the DNS

internal/cmd/jafar/main.go

@@ -58,8 +58,9 @@ var (
 
 	tag *string
 
-	tlsProxyAddress *string
-	tlsProxyBlock   flagx.StringArray
+	tlsProxyAddress      *string
+	tlsProxyBlock        flagx.StringArray
+	tlsProxyOutboundPort *string
 
 	uncensoredResolverDoH *string
 )
@@ -159,12 +160,16 @@ func init() {
 	// tlsProxy
 	tlsProxyAddress = flag.String(
 		"tls-proxy-address", "127.0.0.1:443",
-		"Address where the HTTP proxy should listen",
+		"Address where the TCP+TLS proxy should listen",
 	)
 	flag.Var(
 		&tlsProxyBlock, "tls-proxy-block",
 		"Register keyword triggering TLS censorship",
 	)
+	tlsProxyOutboundPort = flag.String(
+		"tls-proxy-outbound-port", "443",
+		"The outbound port where requests should be proxied",
+	)
 
 	// uncensored
 	uncensoredResolverDoH = flag.String(
@@ -227,7 +232,7 @@ func iptablesStart() *iptables.CensoringPolicy {
 }
 
 func tlsProxyStart(uncensored *uncensored.Client) net.Listener {
-	proxy := tlsproxy.NewCensoringProxy(tlsProxyBlock, uncensored)
+	proxy := tlsproxy.NewCensoringProxy(tlsProxyBlock, uncensored, tlsProxyOutboundPort)
 	listener, err := proxy.Start(*tlsProxyAddress)
 	runtimex.PanicOnError(err, "proxy.Start failed")
 	return listener

internal/cmd/jafar/tlsproxy/tlsproxy.go

@@ -21,8 +21,9 @@ type Dialer interface {
 
 // CensoringProxy is a censoring TLS proxy
 type CensoringProxy struct {
-	keywords []string
-	dial     func(network, address string) (net.Conn, error)
+	keywords     []string
+	dial         func(network, address string) (net.Conn, error)
+	outboundPort string
 }
 
 // NewCensoringProxy creates a new CensoringProxy instance using
@@ -31,13 +32,18 @@ type CensoringProxy struct {
 // the SNII record of a ClientHello. dnsNetwork and dnsAddress are
 // settings to configure the upstream, non censored DNS.
 func NewCensoringProxy(
-	keywords []string, uncensored Dialer,
+	keywords []string, uncensored Dialer, outboundPort *string,
 ) *CensoringProxy {
+	defaultPort := "443"
+	if outboundPort == nil {
+		outboundPort = &defaultPort
+	}
 	return &CensoringProxy{
 		keywords: keywords,
 		dial: func(network, address string) (net.Conn, error) {
 			return uncensored.DialContext(context.Background(), network, address)
 		},
+		outboundPort: *outboundPort,
 	}
 }
 
@@ -146,7 +152,7 @@ func (p *CensoringProxy) handle(clientconn net.Conn) {
 			return
 		}
 	}
-	serverconn, err := p.dial("tcp", net.JoinHostPort(sni, "443"))
+	serverconn, err := p.dial("tcp", net.JoinHostPort(sni, p.outboundPort))
 	if err != nil {
 		log.WithError(err).Warn("tlsproxy: p.dial failed")
 		alertclose(clientconn)

internal/cmd/jafar/tlsproxy/tlsproxy_test.go

@@ -94,7 +94,7 @@ func TestFailWriteAfterConnect(t *testing.T) {
 
 func TestListenError(t *testing.T) {
 	proxy := NewCensoringProxy(
-		[]string{""}, uncensored.NewClient("https://1.1.1.1/dns-query"),
+		[]string{""}, uncensored.NewClient("https://1.1.1.1/dns-query"), nil,
 	)
 	listener, err := proxy.Start("8.8.8.8:80")
 	if err == nil {
@@ -107,7 +107,7 @@ func TestListenError(t *testing.T) {
 
 func newproxy(t *testing.T, blocked string) net.Listener {
 	proxy := NewCensoringProxy(
-		[]string{blocked}, uncensored.NewClient("https://1.1.1.1/dns-query"),
+		[]string{blocked}, uncensored.NewClient("https://1.1.1.1/dns-query"), nil,
 	)
 	listener, err := proxy.Start("127.0.0.1:0")
 	if err != nil {