Merge pull request #170 from SenseUnit/cmd_dialer

External command dialer

Author: Snawoot

README.md

@@ -432,6 +432,9 @@ Supported proxy schemes are:
 * `chain` - pseudo-proxy assembling a chain from other proxy specifications. Query string parameters are:
   * `next` - specification of the next proxy in chain. This query string parameter can be specified more than once. Example: `chain://?next=http%3A%2F%2F127.0.0.1%3A57800&next=force-resolve%3A%2F%2F`.
 * `set-dst` - pseudo-proxy replacing connection destination address with the one specified in hostname part of URI. It is mostly intended for programmatic usage from within routing JS script. Example: `set-dst://localhost:9999`.
+* `cmd` - wrapper which redirects connection into stdin/stdout of external program. Destination address and network are passed to subprocess via `DUMBPROXY_DST_ADDR` and `DUMBPROXY_DST_NET` environment variables. Example: `cmd://?cmd=openssl&arg=s_client&arg=-connect&arg=google.com%3A443`. Parameters:
+  * `cmd` - program to execute.
+  * `arg` - optional command line argument passed to a program. This parameter may be repeated more than once.
 
 ## Configuration files
 

dialer/command.go

@@ -0,0 +1,83 @@
+package dialer
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net"
+	"net/url"
+	"os"
+	"os/exec"
+	"time"
+
+	xproxy "golang.org/x/net/proxy"
+)
+
+type CommandDialer struct {
+	command   []string
+	waitDelay time.Duration
+}
+
+func CommandDialerFromURL(u *url.URL, _ xproxy.Dialer) (xproxy.Dialer, error) {
+	params, err := url.ParseQuery(u.RawQuery)
+	if err != nil {
+		return nil, err
+	}
+	cmd := params.Get("cmd")
+	if cmd == "" {
+		return nil, errors.New("command is not specified")
+	}
+	args := params["arg"]
+	waitDelay := 5 * time.Second
+	if wd := params.Get("wait_delay"); wd != "" {
+		waitDelay, err = time.ParseDuration(wd)
+		if err != nil {
+			return nil, fmt.Errorf("unable to parse wait_delay parameter: %w", err)
+		}
+	}
+	command := make([]string, 0, len(args)+1)
+	command = append(command, cmd)
+	command = append(command, args...)
+	return &CommandDialer{
+		command:   command,
+		waitDelay: waitDelay,
+	}, nil
+}
+
+func (d *CommandDialer) Dial(network, address string) (net.Conn, error) {
+	return d.DialContext(context.Background(), network, address)
+}
+
+func (d *CommandDialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	cmd := exec.CommandContext(ctx, d.command[0], d.command[1:]...)
+	cmd.Env = append(os.Environ(),
+		"DUMBPROXY_DST_ADDR="+address,
+		"DUMBPROXY_DST_NET="+network,
+	)
+	cmdIn, err := cmd.StdinPipe()
+	if err != nil {
+		return nil, fmt.Errorf("can't create stdin pipe for subprocess: %w", err)
+	}
+	cmdOut, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, fmt.Errorf("can't create stdout pipe for subprocess: %w", err)
+	}
+	cmd.Stderr = os.Stderr
+	cmd.WaitDelay = d.waitDelay
+	if err := cmd.Start(); err != nil {
+		return nil, fmt.Errorf("unable to start subprocess: %w", err)
+	}
+	go func() {
+		cmd.Wait()
+		cmdIn.Close()
+		cmdOut.Close()
+	}()
+	return NewPipeConn(cmdOut.(ReadPipe), cmdIn.(WritePipe)), nil
+}
+
+func (d *CommandDialer) WantsHostname(_ context.Context, _, _ string) bool {
+	return true
+}
+
+var _ Dialer = new(CommandDialer)
+var _ HostnameWanter = new(CommandDialer)

dialer/dialer.go

@@ -29,6 +29,7 @@ func init() {
 		return NeverRequireHostname(MaybeWrapWithContextDialer(d)), nil
 	})
 	xproxy.RegisterDialerType("chain", ChainFromURL)
+	xproxy.RegisterDialerType("cmd", CommandDialerFromURL)
 }
 
 type LegacyDialer interface {