Console esc seqs no longer affect in-band input

Signed-off-by: Russ Magee <rmagee@gmail.com>

hkexnet/hkexnet.go

@@ -42,6 +42,7 @@ import (
 	"math/big"
 	"math/rand"
 	"net"
+	"os"
 	"strings"
 	"sync"
 	"time"
@@ -122,11 +123,8 @@ type (
 		dBuf      *bytes.Buffer //decrypt buffer for Read()
 	}
 
-	EscSeqs struct {
-		idx    int
-		seqs   []byte
-		outstr []string
-	}
+	EscHandler func(io.Writer)
+	EscSeqs    map[byte]EscHandler
 )
 
 var (
@@ -1136,60 +1134,40 @@ func Copy(dst io.Writer, src io.Reader) (written int64, err error) {
 	return
 }
 
-func escSeqScanner(s *EscSeqs, dst io.Writer, b byte) (passthru bool) {
-	passthru = true
-	if s.idx > 0 {
-		switch b {
-		case '~':
-			return
-		case s.seqs[0]:
-			dst.Write([]byte(s.outstr[0]))
-			passthru = false
-			b = '~'
-		case s.seqs[1]:
-			dst.Write([]byte(s.outstr[1]))
-			passthru = false
-			b = '~'
-		case s.seqs[2]:
-			dst.Write([]byte(s.outstr[2]))
-			passthru = false
-			b = '~'
-		}
-	}
-
-	if b == '~' {
-		s.idx++
-	} else {
-		s.idx = 0
-	}
-	return
-}
-
 // copyBuffer is the actual implementation of Copy and CopyBuffer.
 // if buf is nil, one is allocated.
 func copyBuffer(dst io.Writer, src io.Reader, buf []byte) (written int64, err error) {
-	escs := &EscSeqs{idx: 0,
-		seqs: []byte{
-			'i',
-			't',
-			'B',
-		},
-		outstr: []string{
-			"\x1b[s\x1b[2;1H\x1b[1;31m[HKEXSH]\x1b[39;49m\x1b[u",
-			"\x1b[1;32m[HKEXSH]\x1b[39;49m",
-			"\x1b[1;32m" + Bob + "\x1b[39;49m",
-		},
+	// NOTE: using dst.Write() in these esc funcs will cause the output
+	// to function as a 'macro', outputting as if user typed the sequence.
+	//
+	// Using os.Stdout outputs to the client's term w/o it or the server
+	// 'seeing' the output.
+	//
+	// TODO: Devise a way to signal to main client thread that
+	// a goroutine should be spawned to do long-lived tasks for
+	// some esc sequences (eg., a time ticker in the corner of terminal,
+	// or tunnel traffic indicator - note we cannot just spawn a goroutine
+	// here, as copyBuffer() returns after each burst of data. Scope must
+	// outlive individual copyBuffer calls).
+	// (Note that since this custom copyBuffer func is used only by
+	// the hkexsh client, it should eventually be moved to client.)
+	escs := EscSeqs{
+		'i': func(io.Writer) { os.Stdout.Write([]byte("\x1b[s\x1b[2;1H\x1b[1;31m[HKEXSH]\x1b[39;49m\x1b[u")) },
+		't': func(io.Writer) { os.Stdout.Write([]byte("\x1b[1;32m[HKEXSH]\x1b[39;49m")) },
+		'B': func(io.Writer) { os.Stdout.Write([]byte("\x1b[1;32m" + Bob + "\x1b[39;49m")) },
 	}
 
-	// If the reader has a WriteTo method, use it to do the copy.
-	// Avoids an allocation and a copy.
-	if wt, ok := src.(io.WriterTo); ok {
-		return wt.WriteTo(dst)
-	}
-	// Similarly, if the writer has a ReadFrom method, use it to do the copy.
-	if rt, ok := dst.(io.ReaderFrom); ok {
-		return rt.ReadFrom(src)
-	}
+	/*
+		// If the reader has a WriteTo method, use it to do the copy.
+		// Avoids an allocation and a copy.
+		if wt, ok := src.(io.WriterTo); ok {
+			return wt.WriteTo(dst)
+		}
+		// Similarly, if the writer has a ReadFrom method, use it to do the copy.
+		if rt, ok := dst.(io.ReaderFrom); ok {
+			return rt.ReadFrom(src)
+		}
+	*/
 	if buf == nil {
 		size := 32 * 1024
 		if l, ok := src.(*io.LimitedReader); ok && int64(size) > l.N {
@@ -1201,23 +1179,39 @@ func copyBuffer(dst io.Writer, src io.Reader, buf []byte) (written int64, err er
 		}
 		buf = make([]byte, size)
 	}
+
+	var seqPos int
 	for {
 		nr, er := src.Read(buf)
 		if nr > 0 {
 			// Look for sequences to trigger client-side diags
-			if escSeqScanner(escs, dst, buf[0]) {
-				nw, ew := dst.Write(buf[0:nr])
-				if nw > 0 {
-					written += int64(nw)
+			// A repeat of 4 keys (conveniently 'dead' chars for most
+			// interactive shells; here CTRL-]) shall introduce
+			// some special responses or actions on the client side.
+			if seqPos < 4 {
+				if buf[0] == 0x1d {
+					seqPos++
 				}
-				if ew != nil {
-					err = ew
-					break
-				}
-				if nr != nw {
-					err = io.ErrShortWrite
-					break
+			} else /* seqPos > 0 */ {
+				if v, ok := escs[buf[0]]; ok {
+					v(dst)
+					nr--
+					buf = buf[1:]
 				}
+				seqPos = 0
+			}
+
+			nw, ew := dst.Write(buf[0:nr])
+			if nw > 0 {
+				written += int64(nw)
+			}
+			if ew != nil {
+				err = ew
+				break
+			}
+			if nr != nw {
+				err = io.ErrShortWrite
+				break
 			}
 		}
 		if er != nil {

hkexsh/hkexsh.go

@@ -249,7 +249,7 @@ func doShellMode(isInteractive bool, conn *hkexnet.Conn, oldState *hkexsh.State,
 
 		// pkg io/Copy expects EOF so normally this will
 		// exit with inerr == nil
-		_, inerr := hkexnet.Copy(os.Stdout, conn)
+		_, inerr := io.Copy(os.Stdout, conn)
 		if inerr != nil {
 			_ = hkexsh.Restore(int(os.Stdin.Fd()), oldState) // #nosec
 			// Copy operations and user logging off will cause
@@ -288,7 +288,7 @@ func doShellMode(isInteractive bool, conn *hkexnet.Conn, oldState *hkexsh.State,
 			_, outerr := func(conn *hkexnet.Conn, r io.Reader) (w int64, e error) {
 				// Copy() expects EOF so this will
 				// exit with outerr == nil
-				w, e = io.Copy(conn, r)
+				w, e = hkexnet.Copy(conn, r)
 				return w, e
 			}(conn, os.Stdin)