Initial commit with Dockerfile and Go code

.github/workflows/build-and-push.yml

@@ -0,0 +1,27 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v3
+
+    - name: Log in to Docker Hub
+      uses: docker/login-action@v2
+      with:
+        username: ${{ secrets.DOCKER_HUB_USERNAME }}
+        password: ${{ secrets.DOCKER_HUB_TOKEN }}
+
+    - name: Build and push Docker image
+      uses: docker/build-push-action@v4
+      with:
+        context: .
+        push: true
+        tags: dcorral/ssh-remote:latest

Dockerfile

@@ -0,0 +1,19 @@
+FROM golang:1.21-alpine AS builder
+
+WORKDIR /app
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY main.go ./
+RUN go build -o sshserver main.go
+
+FROM alpine:latest
+
+RUN apk add --no-cache ca-certificates
+
+COPY --from=builder /app/sshserver /usr/local/bin/sshserver
+
+EXPOSE 22
+
+CMD ["/usr/local/bin/sshserver"]

docker-compose.yml

@@ -0,0 +1,11 @@
+services:
+  ssh-server:
+    image: ssh-server
+    build: .
+    ports:
+      - "22:22"
+    volumes:
+      - ../tui:/app/tui:ro
+    cap_add:
+      - SYS_CHROOT
+    restart: unless-stopped

go.mod

@@ -0,0 +1,10 @@
+module sshserver
+
+go 1.21
+
+require (
+	github.com/creack/pty/v2 v2.0.1
+	golang.org/x/crypto v0.0.0-20220427172511-eb4f295cb31f
+)
+
+require golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1 // indirect

go.sum

@@ -0,0 +1,8 @@
+github.com/creack/pty/v2 v2.0.1 h1:RDY1VY5b+7m2mfPsugucOYPIxMp+xal5ZheSyVzUA+k=
+github.com/creack/pty/v2 v2.0.1/go.mod h1:2dSssKp3b86qYEMwA/FPwc3ff+kYpDdQI8osU8J7gxQ=
+golang.org/x/crypto v0.0.0-20220427172511-eb4f295cb31f h1:OeJjE6G4dgCY4PIXvIRQbE8+RX+uXZyGhUy/ksMGJoc=
+golang.org/x/crypto v0.0.0-20220427172511-eb4f295cb31f/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1 h1:SrN+KX8Art/Sf4HNj6Zcz06G7VEz+7w9tdXTPOZ7+l4=
+golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1 h1:v+OssWQX+hTHEmOBgwxdZxK4zHq3yOs8F9J7mk0PY8E=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=

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()
+}