feat(muxterm): WebSocket server with HMAC token auth and PTY relay

2026-05-28 06:15:05 +00:00
parent 29aabcfd4f
commit 10b57c8f60
6 changed files with 364 additions and 8 deletions
@@ -0,0 +1,188 @@
+package main
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/hex"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/gorilla/websocket"
+)
+
+// ValidateToken checks an HMAC-SHA256 signed token of the form "signature.timestamp".
+// It validates the timestamp is within ttl seconds (not too old) and within 5 seconds
+// of clock skew (not too far in the future), then verifies the HMAC signature.
+func ValidateToken(token, secret string, ttl int64) bool {
+	parts := strings.SplitN(token, ".", 2)
+	if len(parts) != 2 {
+		return false
+	}
+	sig := parts[0]
+	tsStr := parts[1]
+
+	ts, err := strconv.ParseInt(tsStr, 10, 64)
+	if err != nil {
+		return false
+	}
+
+	now := time.Now().Unix()
+	if now-ts > ttl {
+		return false
+	}
+	if ts-now > 5 {
+		return false
+	}
+
+	mac := hmac.New(sha256.New, []byte(secret))
+	mac.Write([]byte(tsStr))
+	expected := hex.EncodeToString(mac.Sum(nil))
+
+	return hmac.Equal([]byte(sig), []byte(expected))
+}
+
+var upgrader = websocket.Upgrader{
+	CheckOrigin: func(r *http.Request) bool {
+		host := r.Host
+		if strings.Contains(host, ":") {
+			host = strings.Split(host, ":")[0]
+		}
+		return host == "localhost" || host == "127.0.0.1"
+	},
+}
+
+// HandleWebSocket validates the token query parameter and upgrades the connection
+// to a WebSocket, then runs the main read loop for control and binary messages.
+func HandleWebSocket(pool *Pool, secret string, w http.ResponseWriter, r *http.Request) {
+	token := r.URL.Query().Get("token")
+	if !ValidateToken(token, secret, 30) {
+		http.Error(w, "forbidden", http.StatusForbidden)
+		return
+	}
+
+	conn, err := upgrader.Upgrade(w, r, nil)
+	if err != nil {
+		log.Printf("ws upgrade: %v", err)
+		return
+	}
+	defer conn.Close()
+
+	var (
+		mu            sync.Mutex
+		activeSession string
+		activePTY     *os.File
+		ptyCancel     chan struct{}
+	)
+
+	startRelay := func(sess *Session, name string) {
+		cancel := make(chan struct{})
+		mu.Lock()
+		ptyCancel = cancel
+		mu.Unlock()
+
+		go func() {
+			buf := make([]byte, 32*1024)
+			for {
+				select {
+				case <-cancel:
+					return
+				default:
+				}
+				n, err := sess.PTY.Read(buf)
+				if n > 0 {
+					if writeErr := conn.WriteMessage(websocket.BinaryMessage, buf[:n]); writeErr != nil {
+						return
+					}
+				}
+				if err != nil {
+					if err == io.EOF || strings.Contains(err.Error(), "input/output error") {
+						conn.WriteMessage(websocket.TextMessage, MarshalExited(name))
+					}
+					return
+				}
+			}
+		}()
+	}
+
+	stopRelay := func() {
+		mu.Lock()
+		defer mu.Unlock()
+		if ptyCancel != nil {
+			close(ptyCancel)
+			ptyCancel = nil
+		}
+	}
+
+	defer stopRelay()
+
+	for {
+		msgType, data, err := conn.ReadMessage()
+		if err != nil {
+			return
+		}
+
+		switch msgType {
+		case websocket.TextMessage:
+			kind, msg := ParseControlMessage(data)
+			switch kind {
+			case "attach":
+				attach := msg.(*AttachMsg)
+				stopRelay()
+
+				sess, err := pool.Attach(attach.Attach, 80, 24)
+				if err != nil {
+					conn.WriteMessage(websocket.TextMessage, MarshalError(err.Error()))
+					continue
+				}
+
+				mu.Lock()
+				activeSession = attach.Attach
+				activePTY = sess.PTY
+				mu.Unlock()
+
+				sendSIGWINCH(sess)
+				startRelay(sess, attach.Attach)
+				conn.WriteMessage(websocket.TextMessage, MarshalAttached(attach.Attach))
+
+			case "resize":
+				resize := msg.(*ResizeMsg)
+				mu.Lock()
+				name := activeSession
+				mu.Unlock()
+				if name != "" {
+					pool.Resize(name, uint16(resize.Resize.Cols), uint16(resize.Resize.Rows))
+				}
+
+			case "detach":
+				stopRelay()
+				mu.Lock()
+				activeSession = ""
+				activePTY = nil
+				mu.Unlock()
+			}
+
+		case websocket.BinaryMessage:
+			mu.Lock()
+			pty := activePTY
+			mu.Unlock()
+			if pty != nil {
+				pty.Write(data)
+			}
+		}
+	}
+}
+
+// sendSIGWINCH sends SIGWINCH to the session's process to trigger tmux repaint.
+func sendSIGWINCH(s *Session) {
+	if s == nil || s.Cmd == nil || s.Cmd.Process == nil {
+		return
+	}
+	s.Cmd.Process.Signal(syscall.SIGWINCH)
+}