feat: add --alpn <proto-list> (for h2, ssh, etc)

.goreleaser.yml

@@ -3,7 +3,7 @@ before:
     - go mod download
     - go generate ./...
 builds:
-  - main: ./cmd/sclient/main.go
+  - main: ./cmd/sclient/
     env:
       - CGO_ENABLED=0
     goos:

README.md

@@ -70,10 +70,11 @@ sclient [flags] <remote> <local>
 ```
 
 - flags
-  - -s, --silent less verbose logging
-  - -k, --insecure ignore invalid TLS (SSL/HTTPS) certificates
-  - --servername <string> spoof SNI (to disable use IP as &lt;remote&gt; and do
+  - `-s`, `--silent` less verbose logging
+  - `-k`, `--insecure` ignore invalid TLS (SSL/HTTPS) certificates
+  - `--servername <domain>` spoof SNI (to disable use IP as &lt;remote&gt; and do
     not use this option)
+  - `--alpn <protocol-list>`
 - remote
   - must have servername (i.e. example.com)
   - port is optional (default is 443)
@@ -81,6 +82,17 @@ sclient [flags] <remote> <local>
   - address is optional (default is localhost)
   - must have port (i.e. 3000)
 
+  -alpn string
+    	acceptable protocols, ex: 'h2,http/1.1' 'http/1.1' (default) 'ssh' (default "http/1.1")
+  -insecure
+    	ignore bad TLS/SSL/HTTPS certificates
+  -k	alias for --insecure
+  -s	alias of --silent
+  -servername string
+    	specify a servername different from <remote> (to disable SNI use an IP as <remote> and do use this option)
+  -silent
+    	less verbose output
+
 # Examples
 
 Bridge between `telebit.cloud` and local port `3000`.

cmd/sclient/main.go

@@ -40,20 +40,30 @@ func usage() {
 
 func main() {
 	if len(os.Args) >= 2 {
-		if "version" == strings.TrimLeft(os.Args[1], "-") {
+		if os.Args[1] == "-V" || strings.TrimLeft(os.Args[1], "-") == "version" {
 			fmt.Printf("%s\n", ver())
 			os.Exit(0)
 			return
 		}
 	}
 
+	var alpnList string
+	var insecure bool
+	var servername string
+	var silent bool
+
 	flag.Usage = usage
-	insecure := flag.Bool("k", false, "alias for --insecure")
-	silent := flag.Bool("s", false, "alias of --silent")
-	servername := flag.String("servername", "", "specify a servername different from <remote> (to disable SNI use an IP as <remote> and do not use this option)")
-	flag.BoolVar(insecure, "insecure", false, "ignore bad TLS/SSL/HTTPS certificates")
-	flag.BoolVar(silent, "silent", false, "less verbose output")
+
+	flag.StringVar(&alpnList, "alpn", "", "acceptable protocols, ex: 'h2,http/1.1' 'http/1.1' 'ssh'")
+	flag.BoolVar(&insecure, "k", false, "alias for --insecure")
+	flag.BoolVar(&silent, "s", false, "alias of --silent")
+	flag.StringVar(&servername, "servername", "", "specify a servername different from <remote> (to disable SNI use an IP as <remote> and do not use this option)")
+	flag.BoolVar(&insecure, "insecure", false, "ignore bad TLS/SSL/HTTPS certificates")
+	flag.BoolVar(&silent, "silent", false, "less verbose output")
+
 	flag.Parse()
+
+	alpns := parseOptionList(alpnList)
 	remotestr := flag.Arg(0)
 	localstr := flag.Arg(1)
 
@@ -71,9 +81,10 @@ func main() {
 	sclient := &sclient.Tunnel{
 		RemotePort:         443,
 		LocalAddress:       "localhost",
-		InsecureSkipVerify: *insecure,
-		ServerName:         *servername,
-		Silent:             *silent,
+		InsecureSkipVerify: insecure,
+		ServerName:         servername,
+		Silent:             silent,
+		NextProtos:         alpns,
 	}
 
 	remote := strings.Split(remotestr, ":")
@@ -124,3 +135,18 @@ func main() {
 		//os.Exit(6)
 	}
 }
+
+// parsers "a,b,c" "a b c" and "a, b, c" all the same
+func parseOptionList(optionList string) []string {
+	optionList = strings.TrimSpace(optionList)
+
+	if len(optionList) == 0 {
+		return nil
+	}
+
+	options := []string{}
+	optionList = strings.ReplaceAll(optionList, ",", " ")
+	options = strings.Fields(optionList)
+
+	return options
+}

sclient.go

@@ -17,6 +17,7 @@ type Tunnel struct {
 	LocalAddress       string
 	LocalPort          int
 	InsecureSkipVerify bool
+	NextProtos         []string
 	ServerName         string
 	Silent             bool
 }
@@ -29,6 +30,7 @@ func (t *Tunnel) DialAndListen() error {
 		&tls.Config{
 			ServerName:         t.ServerName,
 			InsecureSkipVerify: t.InsecureSkipVerify,
+			NextProtos:         t.NextProtos,
 		})
 
 	if err != nil {