Merge pull request #1 from haccht/auto-login

Auto login

README.md

@@ -1,20 +1,24 @@
 # ssh2telnet
 Proxy ssh connection into telnet.
 
-## Usage
+## Options
 
 ```
 $ ssh2telnet -h
 Usage:
   ssh2telnet [OPTIONS]
 
 Application Options:
-  -a, --addr= Address to listen on (default: :2222)
-  -k, --key=  Path to the host key
+  -a, --addr=            Address to listen (default: localhost:2222)
+  -k, --key=             Path to the host key
+  -l, --login            Enable auto login
+      --login-prompt=    Login prompt (default: "login: ")
+      --password-prompt= Password prompt (default: "Password: ")
 
 Help Options:
   -h, --help  Show this help message
 ```
+## Basic Usage
 
 Start a ssh server.
 
@@ -23,18 +27,44 @@ $ ssh2telnet -a :2222
 Starting ssh server on :2222
 ```
 
-Connect the ssh server from the other terminal.
-The given username will be interpeted into the hostname you want to access.
+Connect the server from another terminal.
+The specified username will be interpeted into the hostname.
+Now the proxied telnet session is attached to the target host.
 
 ```
 $ ssh localhost -p 2222 -l 192.168.1.1
 
 
-User Access Verification
+RP/0/RSP0/CPU0:R1#show clock
+Thu Nov 11 00:00:00.000 JST
+00:00:00:000 JST Thu Nov 11 2021
+
+RP/0/RSP0/CPU0:R1#exit
+Connection to localhost closed.
+```
+
+## Auto Login
+
+ssh2telnet also comes with the auto login feature.
+Start a ssh server with the `--login` option and specify `--login-prompt` and/or `--password-prompt` if necessary.
+
+```
+$ ssh2telnet -a :2222 -l --login-prompt 'Username: '
+Starting ssh server on :2222
+```
+
+Connect the server from another terminal.
+The specified username will be interpeted into 'username@hostname'.
+Login password for the target host is also prompted afterward.
+
+```
+$ ssh localhost -p 2222 -l [email protected]
+[email protected]@localhost's password:
 
-Username: vagrant
-Password:
 
+RP/0/RSP0/CPU0:R1#show clock
+Thu Nov 11 00:00:00.000 JST
+00:00:00:000 JST Thu Nov 11 2021
 
 RP/0/RSP0/CPU0:R1#exit
 Connection to localhost closed.

main.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"net"
 	"os"
+	"strings"
 
 	"github.com/gliderlabs/ssh"
 	"github.com/ziutek/telnet"
@@ -14,8 +15,11 @@ import (
 )
 
 type options struct {
-	Addr    string `short:"a" long:"addr" description:"Address to listen on" default:":2222"`
-	HostKey string `short:"k" long:"key"  description:"Path to the host key"`
+	Addr           string `short:"a" long:"addr"  description:"Address to listen" default:"localhost:2222"`
+	HostKey        string `short:"k" long:"key"   description:"Path to the host key"`
+	AutoLogin      bool   `short:"l" long:"login" description:"Enable auto login"`
+	LoginPrompt    string `long:"login-prompt"    description:"Login prompt (default: \"login: \")" default:"login: " default-mask:"-"`
+	PasswordPrompt string `long:"password-prompt" description:"Password prompt (default: \"Password: \")" default:"Password: " default-mask:"-"`
 }
 
 func start(opts options) error {
@@ -26,19 +30,44 @@ func start(opts options) error {
 		server.SetOption(hostKeyFile)
 	}
 
+	var username, password, host string
+	if opts.AutoLogin {
+		passwordAuth := ssh.PasswordAuth(func(ctx ssh.Context, s string) bool {
+			t := strings.SplitN(ctx.User(), "@", 2)
+			if len(t) != 2 {
+				return false
+			}
+
+			username, host = t[0], t[1]
+			password = s
+			return true
+		})
+		server.SetOption(passwordAuth)
+	}
+
 	server.Handle(func(s ssh.Session) {
 		_, _, isPty := s.Pty()
 		if isPty {
-			addr := net.JoinHostPort(s.User(), "23")
+			if host == "" {
+				host = s.User()
+			}
+
+			addr := net.JoinHostPort(host, "23")
 			fmt.Printf("Connecting to %s\n", addr)
 
 			conn, err := telnet.Dial("tcp", addr)
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "Unable to connect to %s.\n", addr)
 				s.Exit(1)
 			} else {
-				sigChan := make(chan struct{}, 1)
+				if opts.AutoLogin {
+					_, err = conn.ReadUntil(opts.LoginPrompt)
+					conn.Write([]byte(fmt.Sprintf("%s\n", username)))
+					_, err = conn.ReadUntil(opts.PasswordPrompt)
+					conn.Write([]byte(fmt.Sprintf("%s\n", password)))
+				}
 
+				sigChan := make(chan struct{}, 1)
 				go func() {
 					_, _ = io.Copy(s, conn)
 					sigChan <- struct{}{}