- got term resizing working (client SIGWINCH signals -> server_pty(rows,cols)

hkexnet.go

@@ -29,19 +29,28 @@ import (
 )
 
 const (
-	csoNone        = iota // No error, normal packet
-	csoHmacInvalid        // HMAC mismatch detect on remote end
-	csoChaff              // This packet is a dummy, do not process beyond decryption
+	CSONone        = iota // No error, normal packet
+	CSOHmacInvalid        // HMAC mismatch detected on remote end
+	CSOTermSize           // set term size (rows:cols)
+	CSOChaff              // Dummy packet, do not pass beyond decryption
 )
 
 /*---------------------------------------------------------------------*/
 
+type WinSize struct {
+	Rows uint16
+	Cols uint16
+}
+
 // Conn is a HKex connection - a drop-in replacement for net.Conn
 type Conn struct {
 	c          net.Conn // which also implements io.Reader, io.Writer, ...
 	h          *HerraduraKEx
-	cipheropts uint32        // post-KEx cipher/hmac options
-	opts       uint32        // post-KEx protocol options (caller-defined)
+	cipheropts uint32 // post-KEx cipher/hmac options
+	opts       uint32 // post-KEx protocol options (caller-defined)
+	WinCh      chan WinSize
+	Rows       uint16
+	Cols       uint16
 	r          cipher.Stream //read cipherStream
 	rm         hash.Hash
 	w          cipher.Stream //write cipherStream
@@ -262,7 +271,8 @@ func (hl HKExListener) Accept() (hc Conn, err error) {
 	}
 	log.Println("[Accepted]")
 
-	hc = Conn{c: c, h: New(0, 0), dBuf: new(bytes.Buffer)}
+	hc = Conn{c: c, h: New(0, 0), WinCh: make(chan WinSize, 1),
+		dBuf: new(bytes.Buffer)}
 
 	// Read in hkexnet.Conn parameters over raw Conn c
 	// d is value for Herradura key exchange
@@ -311,9 +321,10 @@ func (c Conn) Read(b []byte) (n int, err error) {
 		var hmacIn [4]uint8
 		var payloadLen uint32
 
-		// Read ctrl/status opcode (csoHmacInvalid on hmac mismatch)
+		// Read ctrl/status opcode (CSOHmacInvalid on hmac mismatch)
 		err = binary.Read(c.c, binary.BigEndian, &ctrlStatOp)
-		if ctrlStatOp == csoHmacInvalid {
+		log.Printf("[ctrlStatOp: %v]\n", ctrlStatOp)
+		if ctrlStatOp == CSOHmacInvalid {
 			// Other side indicated channel tampering, close channel
 			c.Close()
 			return 1, errors.New("** ALERT - remote end detected HMAC mismatch - possible channel tampering **")
@@ -379,8 +390,12 @@ func (c Conn) Read(b []byte) (n int, err error) {
 		}
 
 		// Throw away pkt if it's chaff (ie., caller to Read() won't see this data)
-		if ctrlStatOp == csoChaff {
+		if ctrlStatOp == CSOChaff {
 			log.Printf("[Chaff pkt]\n")
+		} else if ctrlStatOp == CSOTermSize {
+			fmt.Sscanf(string(payloadBytes), "%d %d", &c.Rows, &c.Cols)
+			log.Printf("[TermSize pkt: rows %v cols %v]\n", c.Rows, c.Cols)
+			c.WinCh <- WinSize{c.Rows, c.Cols}
 		} else {
 			c.dBuf.Write(payloadBytes)
 			//log.Printf("c.dBuf: %s\n", hex.Dump(c.dBuf.Bytes()))
@@ -394,7 +409,7 @@ func (c Conn) Read(b []byte) (n int, err error) {
 		// Log alert if hmac didn't match, corrupted channel
 		if !bytes.Equal(hTmp, []byte(hmacIn[0:])) /*|| hmacIn[0] > 0xf8*/ {
 			fmt.Println("** ALERT - detected HMAC mismatch, possible channel tampering **")
-			_, _ = c.c.Write([]byte{csoHmacInvalid})
+			_, _ = c.c.Write([]byte{CSOHmacInvalid})
 		}
 	}
 
@@ -413,6 +428,11 @@ func (c Conn) Read(b []byte) (n int, err error) {
 //
 // See go doc io.Writer
 func (c Conn) Write(b []byte) (n int, err error) {
+	return c.WritePacket(b, CSONone)
+}
+
+// Write a byte slice with specified ctrlStatusOp byte
+func (c Conn) WritePacket(b []byte, op byte) (n int, err error) {
 	//log.Printf("[Encrypting...]\r\n")
 	var hmacOut []uint8
 	var payloadLen uint32
@@ -437,8 +457,7 @@ func (c Conn) Write(b []byte) (n int, err error) {
 	}
 	log.Printf("  ->ctext:\r\n%s\r\n", hex.Dump(wb.Bytes()))
 
-	var ctrlStatOp byte
-	ctrlStatOp = csoNone
+	ctrlStatOp := op
 	_ = binary.Write(c.c, binary.BigEndian, &ctrlStatOp)
 
 	// Write hmac LSB, payloadLen followed by payload

hkexsh/hkexsh.go

@@ -14,9 +14,12 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"os/exec"
+	"os/signal"
 	"os/user"
 	"strings"
 	"sync"
+	"syscall"
 
 	hkexsh "blitter.com/go/hkexsh"
 	isatty "github.com/mattn/go-isatty"
@@ -30,6 +33,23 @@ type cmdSpec struct {
 	status     int
 }
 
+// get terminal size using 'stty' command
+// (Most portable btwn Linux and MSYS/win32, but
+//  TODO: remove external dep on 'stty' utility)
+func getTermSize() (rows int, cols int, err error) {
+	cmd := exec.Command("stty", "size")
+	cmd.Stdin = os.Stdin
+	out, err := cmd.Output()
+	//fmt.Printf("out: %#v\n", string(out))
+	//fmt.Printf("err: %#v\n", err)
+
+	fmt.Sscanf(string(out), "%d %d\n", &rows, &cols)
+	if err != nil {
+		log.Fatal(err)
+	}
+	return
+}
+
 // Demo of a simple client that dials up to a simple test server to
 // send data.
 //
@@ -77,6 +97,9 @@ func main() {
 	defer conn.Close()
 	// From this point on, conn is a secure encrypted channel
 
+	rows := 0
+	cols := 0
+
 	// Set stdin in raw mode if it's an interactive session
 	// TODO: send flag to server side indicating this
 	//  affects shell command used
@@ -131,7 +154,9 @@ func main() {
 		authCookie: []byte(authCookie),
 		status:     0}
 
-	_, err = fmt.Fprintf(conn, "%d %d %d %d\n", len(rec.op), len(rec.who), len(rec.cmd), len(rec.authCookie))
+	_, err = fmt.Fprintf(conn, "%d %d %d %d\n",
+		len(rec.op), len(rec.who), len(rec.cmd), len(rec.authCookie))
+
 	_, err = conn.Write(rec.op)
 	_, err = conn.Write(rec.who)
 	_, err = conn.Write(rec.cmd)
@@ -168,6 +193,27 @@ func main() {
 	}()
 
 	if isInteractive {
+		// Handle pty resizes (notify server side)
+		ch := make(chan os.Signal, 1)
+		signal.Notify(ch, syscall.SIGWINCH)
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+
+			for range ch {
+				// Query client's term size so we can communicate it to server
+				// pty after interactive session starts
+				rows, cols, err = getTermSize()
+				log.Printf("[rows %v cols %v]\n", rows, cols)
+				if err != nil {
+					panic(err)
+				}
+				termSzPacket := fmt.Sprintf("%d %d", rows, cols)
+				conn.WritePacket([]byte(termSzPacket), hkexsh.CSOTermSize)
+			}
+		}()
+		ch <- syscall.SIGWINCH // Initial resize.
+
 		// client writer (to server) goroutine
 		wg.Add(1)
 		go func() {

hkexshd/hkexshd.go

@@ -28,6 +28,8 @@ type cmdSpec struct {
 	who        []byte
 	cmd        []byte
 	authCookie []byte
+	termRows   []byte
+	termCols   []byte
 	status     int
 }
 
@@ -119,6 +121,15 @@ func runShellAs(who string, cmd string, interactive bool, conn hkexsh.Conn) (err
 	}
 	// Make sure to close the pty at the end.
 	defer func() { _ = ptmx.Close() }() // Best effort.
+
+	// Watch for term resizes
+	go func() {
+		for sz := range conn.WinCh {
+			log.Printf("[Setting term size to: %v %v]\n", sz.Rows, sz.Cols)
+			pty.Setsize(ptmx, &pty.Winsize{Rows: sz.Rows, Cols: sz.Cols})
+		}
+	}()
+
 	// Copy stdin to the pty.. (bgnd goroutine)
 	go func() {
 		_, _ = io.Copy(ptmx, conn)
@@ -171,8 +182,8 @@ func main() {
 		// Wait for a connection.
 		conn, err := l.Accept()
 		if err != nil {
-				log.Printf("Accept() got error(%v), hanging up.\n", err)
-				conn.Close()
+			log.Printf("Accept() got error(%v), hanging up.\n", err)
+			conn.Close()
 			//log.Fatal(err)
 		} else {
 			log.Println("Accepted client")