Some cleanup in prep for possible io.ReadFull() fixed-block session-cmd header to resolve the eaten-byte issue handing Accept off to cmdRunner

demo/client/client.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 
 	hkex "blitter.com/herradurakex"
+	isatty "github.com/mattn/go-isatty"
 	"golang.org/x/sys/unix"
 )
 
@@ -31,6 +32,7 @@ func main() {
 	var cAlg string
 	var hAlg string
 	var server string
+	isInteractive := false
 
 	flag.StringVar(&cAlg, "c", "C_AES_256", "cipher [\"C_AES_256\" | \"C_TWOFISH_128\" | \"C_BLOWFISH_64\"]")
 	flag.StringVar(&hAlg, "h", "H_SHA256", "hmac [\"H_SHA256\"]")
@@ -46,20 +48,27 @@ func main() {
 	}
 	defer conn.Close()
 
-	// Set stdin in raw mode.
+	// Set stdin in raw mode if it's an interactive session
+	if isatty.IsTerminal(os.Stdin.Fd()) {
+		isInteractive = true
 		oldState, err := MakeRaw(int(os.Stdin.Fd()))
 		if err != nil {
 			panic(err)
 		}
 		defer func() { _ = Restore(int(os.Stdin.Fd()), oldState) }() // Best effort.
+	} else {
+		fmt.Println("NOT A TTY")
+	}
 
 	wg.Add(1)
 	go func() {
-		// This will guarantee the side that closes first
+		// By deferring a call to wg.Done(),
-		// marks its direction's goroutine as finished.
+		// each goroutine guarantees that it marks
+		// its direction's stream as finished.
+		//
 		// Whichever direction's goroutine finishes first
-		// will call wg.Done() once more explicitly to
+		// will call wg.Done() once more, explicitly, to
-		// hang up on the other side so the client
+		// hang up on the other side, so that this client
 		// exits immediately on an EOF from either side.
 		defer wg.Done()
 
@@ -72,8 +81,10 @@ func main() {
 				os.Exit(1)
 			}
 		}
+		if isInteractive {
 			log.Println("[Got Write EOF]")
-		wg.Done() // client hanging up, close server read goroutine
+			wg.Done() // client hanging up, close WaitGroup to exit client
+		}
 	}()
 
 	wg.Add(1)
@@ -90,7 +101,7 @@ func main() {
 			}
 		}
 		log.Println("[Got Read EOF]")
-		wg.Done() // server hung up, close client write goroutine
+		wg.Done() // server hung up, close WaitGroup to exit client
 	}()
 
 	// Wait until both stdin and stdout goroutines finish
@@ -99,13 +110,16 @@ func main() {
 
 /* ------------- minimal terminal APIs brought in from ssh/terminal
  * (they have no real business being there as they aren't specific to
- * ssh.)
+ * ssh, but as of v1.10, early 2018, core go stdlib hasn't yet done
+ * the planned terminal lib reorgs.)
  * -------------
  */
 
+// From github.com/golang/crypto/blob/master/ssh/terminal/util_linux.go
 const ioctlReadTermios = unix.TCGETS
 const ioctlWriteTermios = unix.TCSETS
 
+// From github.com/golang/crypto/blob/master/ssh/terminal/util.go
 // State contains the state of a terminal.
 type State struct {
 	termios unix.Termios

demo/server/server.go

@@ -16,6 +16,9 @@ import (
 	"github.com/kr/pty"
 )
 
+// Unused, probably obsolete. Once interactive session
+// and piped I/O one-shot commands are working reconsider
+// how Op might be used
 const (
 	OpR   = 'r' // read(file) (binary mode)
 	OpW   = 'w' // (over)write
@@ -39,78 +42,11 @@ type cmdRunner struct {
 	status     int
 }
 
-/* ------------- minimal terminal APIs brought in from ssh/terminal
- * (they have no real business being there as they aren't specific to
- * ssh.)
- * -------------
- */
-
-/*
-// MakeRaw put the terminal connected to the given file descriptor into raw
-// mode and returns the previous state of the terminal so that it can be
-// restored.
-func MakeRaw(fd int) (*State, error) {
-	termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
-	if err != nil {
-		return nil, err
-	}
-
-	oldState := State{termios: *termios}
-
-	// This attempts to replicate the behaviour documented for cfmakeraw in
-	// the termios(3) manpage.
-	termios.Iflag &^= unix.IGNBRK | unix.BRKINT | unix.PARMRK | unix.ISTRIP | unix.INLCR | unix.IGNCR | unix.ICRNL | unix.IXON
-	termios.Oflag &^= unix.OPOST
-	termios.Lflag &^= unix.ECHO | unix.ECHONL | unix.ICANON | unix.ISIG | unix.IEXTEN
-	termios.Cflag &^= unix.CSIZE | unix.PARENB
-	termios.Cflag |= unix.CS8
-	termios.Cc[unix.VMIN] = 1
-	termios.Cc[unix.VTIME] = 0
-	if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, termios); err != nil {
-		return nil, err
-	}
-
-	return &oldState, nil
-}
-
-// GetState returns the current state of a terminal which may be useful to
-// restore the terminal after a signal.
-func GetState(fd int) (*State, error) {
-	termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
-	if err != nil {
-		return nil, err
-	}
-
-	return &State{termios: *termios}, nil
-}
-
-// Restore restores the terminal connected to the given file descriptor to a
-// previous state.
-func Restore(fd int, state *State) error {
-	return unix.IoctlSetTermios(fd, ioctlWriteTermios, &state.termios)
-}
-*/
-
 /* -------------------------------------------------------------- */
 
-/*
- func cmd(r *cmdRunner) {
-	switch r.op {
-	case OpR:
-		//Clean up r.cmd beforehand
-		r.arg = strings.TrimSpace(r.arg)
-		fmt.Printf("[cmd was:'%s']\n", r.arg)
-		runCmdAs(r.who, r.arg, nil)
-		fmt.Println(r.arg)
-		break
-	default:
-		fmt.Printf("[cmd %d ignored:%d]\n", int(r.op))
-		break
-	}
-}
-*/
-
 // Run a command (via os.exec) as a specific user
+//
+// Uses ptys to support commands which expect a terminal.
 func runCmdAs(who string, cmd string, conn hkex.Conn) (err error) {
 	u, _ := user.Lookup(who)
 	var uid, gid uint32
@@ -183,6 +119,7 @@ func main() {
 		// multiple connections may be served concurrently.
 		go func(c hkex.Conn) (e error) {
 			defer c.Close()
+			var connOp *byte = nil
 			ch := make(chan []byte)
 			chN := 0
 			eCh := make(chan error)
@@ -204,8 +141,6 @@ func main() {
 			}(ch, eCh)
 
 			ticker := time.Tick(time.Second / 100)
-			//var r cmdRunner
-			var connOp *byte = nil
 		Term:
 			// continuously read from the connection
 			for {
@@ -216,27 +151,21 @@ func main() {
 					fmt.Printf("Client sent %+v\n", data[0:chN])
 					if connOp == nil {
 						// Initial xmit - get op byte
-						// (TODO: determine valid ops
+						// Have op here and first block of data[]
-						//  for now 'e' (echo), 'i' (interactive), 'x' (exec), ... ?)
 						connOp = new(byte)
 						*connOp = data[0]
+						fmt.Printf("[* connOp '%c']\n", *connOp)
+					}
+					if len(data) > 1 {
 						data = data[1:chN]
 						chN -= 1
-						// Have op here and first block of data[]
-
-						fmt.Printf("[* connOp '%c']\n", *connOp)
-						// The CloseHandler typically handles the
-						// accumulated command data
-						//r = cmdRunner{op: Op(*connOp),
-						//	who: "larissa", arg: string(data),
-						//	authCookie:   "c00ki3",
-						//	status:       0}
 					}
 
+					if len(data) > 0 {
 						// From here, one could pass all subsequent data
 						// between client/server attached to an exec.Cmd,
 						// as data to/from a file, etc.
-					if *connOp == 's' {
+						if connOp != nil && *connOp == 's' {
 							fmt.Println("[Running shell]")
 							runCmdAs("larissa", "bash -l -i", conn)
 							// Returned hopefully via an EOF or exit/logout;
@@ -248,7 +177,7 @@ func main() {
 						if strings.Trim(string(data), "\r\n") == "exit" {
 							conn.Close()
 						}
-
+					}
 					//fmt.Printf("Client sent %s\n", string(data))
 				// This case means we got an error and the goroutine has finished
 				case err := <-eCh: