Initial commit with Dockerfile and Go code

main.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"crypto/ed25519"
+	"crypto/rand"
+	"encoding/binary"
+	"io"
+	"log"
+	"net"
+	"os"
+	"os/exec"
+	"golang.org/x/crypto/ssh"
+	"github.com/creack/pty/v2"
+)
+
+func main() {
+	config := &ssh.ServerConfig{
+		NoClientAuth: true,
+	}
+	_, key, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		log.Fatal(err)
+	}
+	signer, err := ssh.NewSignerFromKey(key)
+	if err != nil {
+		log.Fatal(err)
+	}
+	config.AddHostKey(signer)
+	listener, err := net.Listen("tcp", ":22")
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println("SSH server listening on :22")
+	for {
+		conn, err := listener.Accept()
+		if err != nil {
+			log.Println("Accept error:", err)
+			continue
+		}
+		go handleConn(conn, config)
+	}
+}
+
+func handleConn(conn net.Conn, config *ssh.ServerConfig) {
+	sshConn, chans, reqs, err := ssh.NewServerConn(conn, config)
+	if err != nil {
+		log.Println("ServerConn error:", err)
+		conn.Close()
+		return
+	}
+	log.Println("New connection from", sshConn.RemoteAddr(), "user", sshConn.User())
+	go ssh.DiscardRequests(reqs)
+	for newChannel := range chans {
+		if newChannel.ChannelType() != "session" {
+			newChannel.Reject(ssh.UnknownChannelType, "unknown channel type")
+			continue
+		}
+		channel, requests, err := newChannel.Accept()
+		if err != nil {
+			log.Println("Channel accept error:", err)
+			continue
+		}
+		go handleChannel(channel, requests)
+	}
+	sshConn.Wait()
+}
+
+func handleChannel(channel ssh.Channel, requests <-chan *ssh.Request) {
+	defer channel.Close()
+	var ptmx *os.File
+	for req := range requests {
+		switch req.Type {
+		case "pty-req":
+			req.Reply(true, nil)
+		case "window-change":
+			if ptmx != nil {
+				width := binary.BigEndian.Uint32(req.Payload)
+				height := binary.BigEndian.Uint32(req.Payload[4:])
+				pty.Setsize(ptmx, &pty.Winsize{Cols: uint16(width), Rows: uint16(height)})
+			}
+			req.Reply(true, nil)
+		case "shell":
+			req.Reply(true, nil)
+			cmd := exec.Command("/app/tui")
+			cmd.Env = []string{"PATH=/bin"}
+			cmd.Dir = "/"
+			var err error
+			ptmx, err = pty.Start(cmd)
+			if err != nil {
+				log.Println("PTY start error:", err)
+				return
+			}
+			go func() {
+				defer ptmx.Close()
+				go io.Copy(channel, ptmx)
+				go io.Copy(ptmx, channel)
+				cmd.Wait()
+				channel.Close()
+			}()
+		case "exec":
+			req.Reply(true, nil)
+			command := string(req.Payload[4:])
+			runCommand(channel, command)
+			return
+		default:
+			req.Reply(false, nil)
+		}
+	}
+}
+
+func runCommand(channel ssh.Channel, command string) {
+	cmd := exec.Command("/bin/bash", "-c", command)
+	cmd.Env = []string{"PATH=/bin"}
+	cmd.Dir = "/"
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		log.Println("StdinPipe error:", err)
+		return
+	}
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		log.Println("StdoutPipe error:", err)
+		return
+	}
+	stderr, err := cmd.StderrPipe()
+	if err != nil {
+		log.Println("StderrPipe error:", err)
+		return
+	}
+	if err := cmd.Start(); err != nil {
+		log.Println("Start error:", err)
+		return
+	}
+	go io.Copy(stdin, channel)
+	go io.Copy(channel, stdout)
+	go io.Copy(channel, stderr)
+	cmd.Wait()
+}