Add tuntls command

When used in conjunction with raw Client TLS termination, allows
wrapping plain TCP in TLS with SNI routing. Supports both
stdin/stdout (useful for things like ssh ProxyCommand) and
listening on a local port and forwarding all connections to that
port.

cmd/boringproxy/main.go

@@ -2,9 +2,13 @@ package main
 
 import (
 	"context"
+	"crypto/tls"
 	"flag"
 	"fmt"
+	"io"
+	"net"
 	"os"
+	"sync"
 
 	"github.com/boringproxy/boringproxy"
 )
@@ -15,6 +19,7 @@ Commands:
     version      Prints version information.
     server       Start a new server.
     client       Connect to a server.
+    tuntls       Tunnel a raw TLS connection.
 
 Use "%[1]s command -h" for a list of flags for the command.
 `
@@ -25,7 +30,6 @@ func fail(msg string) {
 	fmt.Fprintln(os.Stderr, msg)
 	os.Exit(1)
 }
-
 func main() {
 	if len(os.Args) < 2 {
 		fmt.Fprintln(os.Stderr, os.Args[0]+": Need a command")
@@ -40,6 +44,44 @@ func main() {
 		fmt.Println(Version)
 	case "help", "-h", "--help", "-help":
 		fmt.Printf(usage, os.Args[0])
+	case "tuntls":
+		// This command is a direct port of https://github.com/anderspitman/tuntls
+		flagSet := flag.NewFlagSet(os.Args[0], flag.ExitOnError)
+		server := flagSet.String("server", "", "boringproxy server")
+		port := flagSet.Int("port", 0, "Local port to bind to")
+		err := flagSet.Parse(os.Args[2:])
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%s: parsing flags: %s\n", os.Args[0], err)
+			os.Exit(1)
+		}
+
+		if *server == "" {
+			fmt.Fprintf(os.Stderr, "server argument is required\n")
+			os.Exit(1)
+		}
+
+		if *port == 0 {
+			// one-time tunnel over stdin/stdout
+			doTlsTunnel(*server, os.Stdin, os.Stdout)
+		} else {
+			// listen on a port and create tunnels for each connection
+			fmt.Fprintf(os.Stderr, "Listening on port %d\n", *port)
+			listener, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
+			if err != nil {
+				fmt.Fprintf(os.Stderr, err.Error())
+				os.Exit(1)
+			}
+
+			for {
+				conn, err := listener.Accept()
+				if err != nil {
+					fmt.Fprintf(os.Stderr, err.Error())
+					os.Exit(1)
+				}
+
+				go doTlsTunnel(*server, conn, conn)
+			}
+		}
 	case "server":
 		boringproxy.Listen()
 	case "client":
@@ -97,3 +139,32 @@ func main() {
 		fail(os.Args[0] + ": Invalid command " + command)
 	}
 }
+
+func doTlsTunnel(server string, in io.Reader, out io.Writer) {
+	fmt.Fprintf(os.Stderr, "tuntls connecting to server: %s\n", server)
+
+	conn, err := tls.Dial("tcp", fmt.Sprintf("%s:443", server), &tls.Config{
+		//RootCAs: roots,
+	})
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Failed to connect: "+err.Error())
+		os.Exit(1)
+	}
+
+	var wg sync.WaitGroup
+	wg.Add(2)
+
+	go func() {
+		io.Copy(conn, in)
+		wg.Done()
+	}()
+
+	go func() {
+		io.Copy(out, conn)
+		wg.Done()
+	}()
+
+	wg.Wait()
+
+	conn.Close()
+}