sshd/terminal: Import fork of x/crypto/ssh

sshd/terminal/NOTICE

@@ -0,0 +1,32 @@
+This directory contains a fork of https://github.com/golang/crypto/tree/master/ssh/terminal
+
+Original license applies:
+
+
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

sshd/terminal/terminal.go

@@ -0,0 +1,955 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package terminal
+
+import (
+	"bytes"
+	"io"
+	"sync"
+	"unicode/utf8"
+)
+
+// EscapeCodes contains escape sequences that can be written to the terminal in
+// order to achieve different styles of text.
+type EscapeCodes struct {
+	// Foreground colors
+	Black, Red, Green, Yellow, Blue, Magenta, Cyan, White []byte
+
+	// Reset all attributes
+	Reset []byte
+}
+
+var vt100EscapeCodes = EscapeCodes{
+	Black:   []byte{keyEscape, '[', '3', '0', 'm'},
+	Red:     []byte{keyEscape, '[', '3', '1', 'm'},
+	Green:   []byte{keyEscape, '[', '3', '2', 'm'},
+	Yellow:  []byte{keyEscape, '[', '3', '3', 'm'},
+	Blue:    []byte{keyEscape, '[', '3', '4', 'm'},
+	Magenta: []byte{keyEscape, '[', '3', '5', 'm'},
+	Cyan:    []byte{keyEscape, '[', '3', '6', 'm'},
+	White:   []byte{keyEscape, '[', '3', '7', 'm'},
+
+	Reset: []byte{keyEscape, '[', '0', 'm'},
+}
+
+// Terminal contains the state for running a VT100 terminal that is capable of
+// reading lines of input.
+type Terminal struct {
+	// AutoCompleteCallback, if non-null, is called for each keypress with
+	// the full input line and the current position of the cursor (in
+	// bytes, as an index into |line|). If it returns ok=false, the key
+	// press is processed normally. Otherwise it returns a replacement line
+	// and the new cursor position.
+	AutoCompleteCallback func(line string, pos int, key rune) (newLine string, newPos int, ok bool)
+
+	// Escape contains a pointer to the escape codes for this terminal.
+	// It's always a valid pointer, although the escape codes themselves
+	// may be empty if the terminal doesn't support them.
+	Escape *EscapeCodes
+
+	// lock protects the terminal and the state in this object from
+	// concurrent processing of a key press and a Write() call.
+	lock sync.Mutex
+
+	c      io.ReadWriter
+	prompt []rune
+
+	// line is the current line being entered.
+	line []rune
+	// pos is the logical position of the cursor in line
+	pos int
+	// echo is true if local echo is enabled
+	echo bool
+	// pasteActive is true iff there is a bracketed paste operation in
+	// progress.
+	pasteActive bool
+
+	// cursorX contains the current X value of the cursor where the left
+	// edge is 0. cursorY contains the row number where the first row of
+	// the current line is 0.
+	cursorX, cursorY int
+	// maxLine is the greatest value of cursorY so far.
+	maxLine int
+
+	termWidth, termHeight int
+
+	// outBuf contains the terminal data to be sent.
+	outBuf []byte
+	// remainder contains the remainder of any partial key sequences after
+	// a read. It aliases into inBuf.
+	remainder []byte
+	inBuf     [256]byte
+
+	// history contains previously entered commands so that they can be
+	// accessed with the up and down keys.
+	history stRingBuffer
+	// historyIndex stores the currently accessed history entry, where zero
+	// means the immediately previous entry.
+	historyIndex int
+	// When navigating up and down the history it's possible to return to
+	// the incomplete, initial line. That value is stored in
+	// historyPending.
+	historyPending string
+}
+
+// NewTerminal runs a VT100 terminal on the given ReadWriter. If the ReadWriter is
+// a local terminal, that terminal must first have been put into raw mode.
+// prompt is a string that is written at the start of each input line (i.e.
+// "> ").
+func NewTerminal(c io.ReadWriter, prompt string) *Terminal {
+	return &Terminal{
+		Escape:       &vt100EscapeCodes,
+		c:            c,
+		prompt:       []rune(prompt),
+		termWidth:    80,
+		termHeight:   24,
+		echo:         true,
+		historyIndex: -1,
+	}
+}
+
+const (
+	keyCtrlD     = 4
+	keyCtrlU     = 21
+	keyEnter     = '\r'
+	keyEscape    = 27
+	keyBackspace = 127
+	keyUnknown   = 0xd800 /* UTF-16 surrogate area */ + iota
+	keyUp
+	keyDown
+	keyLeft
+	keyRight
+	keyAltLeft
+	keyAltRight
+	keyHome
+	keyEnd
+	keyDeleteWord
+	keyDeleteLine
+	keyClearScreen
+	keyPasteStart
+	keyPasteEnd
+)
+
+var (
+	crlf       = []byte{'\r', '\n'}
+	pasteStart = []byte{keyEscape, '[', '2', '0', '0', '~'}
+	pasteEnd   = []byte{keyEscape, '[', '2', '0', '1', '~'}
+)
+
+// bytesToKey tries to parse a key sequence from b. If successful, it returns
+// the key and the remainder of the input. Otherwise it returns utf8.RuneError.
+func bytesToKey(b []byte, pasteActive bool) (rune, []byte) {
+	if len(b) == 0 {
+		return utf8.RuneError, nil
+	}
+
+	if !pasteActive {
+		switch b[0] {
+		case 1: // ^A
+			return keyHome, b[1:]
+		case 5: // ^E
+			return keyEnd, b[1:]
+		case 8: // ^H
+			return keyBackspace, b[1:]
+		case 11: // ^K
+			return keyDeleteLine, b[1:]
+		case 12: // ^L
+			return keyClearScreen, b[1:]
+		case 23: // ^W
+			return keyDeleteWord, b[1:]
+		case 14: // ^N
+			return keyDown, b[1:]
+		case 16: // ^P
+			return keyUp, b[1:]
+		}
+	}
+
+	if b[0] != keyEscape {
+		if !utf8.FullRune(b) {
+			return utf8.RuneError, b
+		}
+		r, l := utf8.DecodeRune(b)
+		return r, b[l:]
+	}
+
+	if !pasteActive && len(b) >= 3 && b[0] == keyEscape && b[1] == '[' {
+		switch b[2] {
+		case 'A':
+			return keyUp, b[3:]
+		case 'B':
+			return keyDown, b[3:]
+		case 'C':
+			return keyRight, b[3:]
+		case 'D':
+			return keyLeft, b[3:]
+		case 'H':
+			return keyHome, b[3:]
+		case 'F':
+			return keyEnd, b[3:]
+		}
+	}
+
+	if !pasteActive && len(b) >= 6 && b[0] == keyEscape && b[1] == '[' && b[2] == '1' && b[3] == ';' && b[4] == '3' {
+		switch b[5] {
+		case 'C':
+			return keyAltRight, b[6:]
+		case 'D':
+			return keyAltLeft, b[6:]
+		}
+	}
+
+	if !pasteActive && len(b) >= 6 && bytes.Equal(b[:6], pasteStart) {
+		return keyPasteStart, b[6:]
+	}
+
+	if pasteActive && len(b) >= 6 && bytes.Equal(b[:6], pasteEnd) {
+		return keyPasteEnd, b[6:]
+	}
+
+	// If we get here then we have a key that we don't recognise, or a
+	// partial sequence. It's not clear how one should find the end of a
+	// sequence without knowing them all, but it seems that [a-zA-Z~] only
+	// appears at the end of a sequence.
+	for i, c := range b[0:] {
+		if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c == '~' {
+			return keyUnknown, b[i+1:]
+		}
+	}
+
+	return utf8.RuneError, b
+}
+
+// queue appends data to the end of t.outBuf
+func (t *Terminal) queue(data []rune) {
+	t.outBuf = append(t.outBuf, []byte(string(data))...)
+}
+
+var eraseUnderCursor = []rune{' ', keyEscape, '[', 'D'}
+var space = []rune{' '}
+
+func isPrintable(key rune) bool {
+	isInSurrogateArea := key >= 0xd800 && key <= 0xdbff
+	return key >= 32 && !isInSurrogateArea
+}
+
+// moveCursorToPos appends data to t.outBuf which will move the cursor to the
+// given, logical position in the text.
+func (t *Terminal) moveCursorToPos(pos int) {
+	if !t.echo {
+		return
+	}
+
+	x := visualLength(t.prompt) + pos
+	y := x / t.termWidth
+	x = x % t.termWidth
+
+	up := 0
+	if y < t.cursorY {
+		up = t.cursorY - y
+	}
+
+	down := 0
+	if y > t.cursorY {
+		down = y - t.cursorY
+	}
+
+	left := 0
+	if x < t.cursorX {
+		left = t.cursorX - x
+	}
+
+	right := 0
+	if x > t.cursorX {
+		right = x - t.cursorX
+	}
+
+	t.cursorX = x
+	t.cursorY = y
+	t.move(up, down, left, right)
+}
+
+func (t *Terminal) move(up, down, left, right int) {
+	movement := make([]rune, 3*(up+down+left+right))
+	m := movement
+	for i := 0; i < up; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'A'
+		m = m[3:]
+	}
+	for i := 0; i < down; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'B'
+		m = m[3:]
+	}
+	for i := 0; i < left; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'D'
+		m = m[3:]
+	}
+	for i := 0; i < right; i++ {
+		m[0] = keyEscape
+		m[1] = '['
+		m[2] = 'C'
+		m = m[3:]
+	}
+
+	t.queue(movement)
+}
+
+func (t *Terminal) clearLineToRight() {
+	op := []rune{keyEscape, '[', 'K'}
+	t.queue(op)
+}
+
+const maxLineLength = 4096
+
+func (t *Terminal) setLine(newLine []rune, newPos int) {
+	if t.echo {
+		t.moveCursorToPos(0)
+		t.writeLine(newLine)
+		for i := len(newLine); i < len(t.line); i++ {
+			t.writeLine(space)
+		}
+		t.moveCursorToPos(newPos)
+	}
+	t.line = newLine
+	t.pos = newPos
+}
+
+func (t *Terminal) advanceCursor(places int) {
+	t.cursorX += places
+	t.cursorY += t.cursorX / t.termWidth
+	if t.cursorY > t.maxLine {
+		t.maxLine = t.cursorY
+	}
+	t.cursorX = t.cursorX % t.termWidth
+
+	if places > 0 && t.cursorX == 0 {
+		// Normally terminals will advance the current position
+		// when writing a character. But that doesn't happen
+		// for the last character in a line. However, when
+		// writing a character (except a new line) that causes
+		// a line wrap, the position will be advanced two
+		// places.
+		//
+		// So, if we are stopping at the end of a line, we
+		// need to write a newline so that our cursor can be
+		// advanced to the next line.
+		t.outBuf = append(t.outBuf, '\r', '\n')
+	}
+}
+
+func (t *Terminal) eraseNPreviousChars(n int) {
+	if n == 0 {
+		return
+	}
+
+	if t.pos < n {
+		n = t.pos
+	}
+	t.pos -= n
+	t.moveCursorToPos(t.pos)
+
+	copy(t.line[t.pos:], t.line[n+t.pos:])
+	t.line = t.line[:len(t.line)-n]
+	if t.echo {
+		t.writeLine(t.line[t.pos:])
+		for i := 0; i < n; i++ {
+			t.queue(space)
+		}
+		t.advanceCursor(n)
+		t.moveCursorToPos(t.pos)
+	}
+}
+
+// countToLeftWord returns then number of characters from the cursor to the
+// start of the previous word.
+func (t *Terminal) countToLeftWord() int {
+	if t.pos == 0 {
+		return 0
+	}
+
+	pos := t.pos - 1
+	for pos > 0 {
+		if t.line[pos] != ' ' {
+			break
+		}
+		pos--
+	}
+	for pos > 0 {
+		if t.line[pos] == ' ' {
+			pos++
+			break
+		}
+		pos--
+	}
+
+	return t.pos - pos
+}
+
+// countToRightWord returns then number of characters from the cursor to the
+// start of the next word.
+func (t *Terminal) countToRightWord() int {
+	pos := t.pos
+	for pos < len(t.line) {
+		if t.line[pos] == ' ' {
+			break
+		}
+		pos++
+	}
+	for pos < len(t.line) {
+		if t.line[pos] != ' ' {
+			break
+		}
+		pos++
+	}
+	return pos - t.pos
+}
+
+// visualLength returns the number of visible glyphs in s.
+func visualLength(runes []rune) int {
+	inEscapeSeq := false
+	length := 0
+
+	for _, r := range runes {
+		switch {
+		case inEscapeSeq:
+			if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') {
+				inEscapeSeq = false
+			}
+		case r == '\x1b':
+			inEscapeSeq = true
+		default:
+			length++
+		}
+	}
+
+	return length
+}
+
+// handleKey processes the given key and, optionally, returns a line of text
+// that the user has entered.
+func (t *Terminal) handleKey(key rune) (line string, ok bool) {
+	if t.pasteActive && key != keyEnter {
+		t.addKeyToLine(key)
+		return
+	}
+
+	switch key {
+	case keyBackspace:
+		if t.pos == 0 {
+			return
+		}
+		t.eraseNPreviousChars(1)
+	case keyAltLeft:
+		// move left by a word.
+		t.pos -= t.countToLeftWord()
+		t.moveCursorToPos(t.pos)
+	case keyAltRight:
+		// move right by a word.
+		t.pos += t.countToRightWord()
+		t.moveCursorToPos(t.pos)
+	case keyLeft:
+		if t.pos == 0 {
+			return
+		}
+		t.pos--
+		t.moveCursorToPos(t.pos)
+	case keyRight:
+		if t.pos == len(t.line) {
+			return
+		}
+		t.pos++
+		t.moveCursorToPos(t.pos)
+	case keyHome:
+		if t.pos == 0 {
+			return
+		}
+		t.pos = 0
+		t.moveCursorToPos(t.pos)
+	case keyEnd:
+		if t.pos == len(t.line) {
+			return
+		}
+		t.pos = len(t.line)
+		t.moveCursorToPos(t.pos)
+	case keyUp:
+		entry, ok := t.history.NthPreviousEntry(t.historyIndex + 1)
+		if !ok {
+			return "", false
+		}
+		if t.historyIndex == -1 {
+			t.historyPending = string(t.line)
+		}
+		t.historyIndex++
+		runes := []rune(entry)
+		t.setLine(runes, len(runes))
+	case keyDown:
+		switch t.historyIndex {
+		case -1:
+			return
+		case 0:
+			runes := []rune(t.historyPending)
+			t.setLine(runes, len(runes))
+			t.historyIndex--
+		default:
+			entry, ok := t.history.NthPreviousEntry(t.historyIndex - 1)
+			if ok {
+				t.historyIndex--
+				runes := []rune(entry)
+				t.setLine(runes, len(runes))
+			}
+		}
+	case keyEnter:
+		t.moveCursorToPos(len(t.line))
+		t.queue([]rune("\r\n"))
+		line = string(t.line)
+		ok = true
+		t.line = t.line[:0]
+		t.pos = 0
+		t.cursorX = 0
+		t.cursorY = 0
+		t.maxLine = 0
+	case keyDeleteWord:
+		// Delete zero or more spaces and then one or more characters.
+		t.eraseNPreviousChars(t.countToLeftWord())
+	case keyDeleteLine:
+		// Delete everything from the current cursor position to the
+		// end of line.
+		for i := t.pos; i < len(t.line); i++ {
+			t.queue(space)
+			t.advanceCursor(1)
+		}
+		t.line = t.line[:t.pos]
+		t.moveCursorToPos(t.pos)
+	case keyCtrlD:
+		// Erase the character under the current position.
+		// The EOF case when the line is empty is handled in
+		// readLine().
+		if t.pos < len(t.line) {
+			t.pos++
+			t.eraseNPreviousChars(1)
+		}
+	case keyCtrlU:
+		t.eraseNPreviousChars(t.pos)
+	case keyClearScreen:
+		// Erases the screen and moves the cursor to the home position.
+		t.queue([]rune("\x1b[2J\x1b[H"))
+		t.queue(t.prompt)
+		t.cursorX, t.cursorY = 0, 0
+		t.advanceCursor(visualLength(t.prompt))
+		t.setLine(t.line, t.pos)
+	default:
+		if t.AutoCompleteCallback != nil {
+			prefix := string(t.line[:t.pos])
+			suffix := string(t.line[t.pos:])
+
+			t.lock.Unlock()
+			newLine, newPos, completeOk := t.AutoCompleteCallback(prefix+suffix, len(prefix), key)
+			t.lock.Lock()
+
+			if completeOk {
+				t.setLine([]rune(newLine), utf8.RuneCount([]byte(newLine)[:newPos]))
+				return
+			}
+		}
+		if !isPrintable(key) {
+			return
+		}
+		if len(t.line) == maxLineLength {
+			return
+		}
+		t.addKeyToLine(key)
+	}
+	return
+}
+
+// addKeyToLine inserts the given key at the current position in the current
+// line.
+func (t *Terminal) addKeyToLine(key rune) {
+	if len(t.line) == cap(t.line) {
+		newLine := make([]rune, len(t.line), 2*(1+len(t.line)))
+		copy(newLine, t.line)
+		t.line = newLine
+	}
+	t.line = t.line[:len(t.line)+1]
+	copy(t.line[t.pos+1:], t.line[t.pos:])
+	t.line[t.pos] = key
+	if t.echo {
+		t.writeLine(t.line[t.pos:])
+	}
+	t.pos++
+	t.moveCursorToPos(t.pos)
+}
+
+func (t *Terminal) writeLine(line []rune) {
+	for len(line) != 0 {
+		remainingOnLine := t.termWidth - t.cursorX
+		todo := len(line)
+		if todo > remainingOnLine {
+			todo = remainingOnLine
+		}
+		t.queue(line[:todo])
+		t.advanceCursor(visualLength(line[:todo]))
+		line = line[todo:]
+	}
+}
+
+// writeWithCRLF writes buf to w but replaces all occurrences of \n with \r\n.
+func writeWithCRLF(w io.Writer, buf []byte) (n int, err error) {
+	for len(buf) > 0 {
+		i := bytes.IndexByte(buf, '\n')
+		todo := len(buf)
+		if i >= 0 {
+			todo = i
+		}
+
+		var nn int
+		nn, err = w.Write(buf[:todo])
+		n += nn
+		if err != nil {
+			return n, err
+		}
+		buf = buf[todo:]
+
+		if i >= 0 {
+			if _, err = w.Write(crlf); err != nil {
+				return n, err
+			}
+			n++
+			buf = buf[1:]
+		}
+	}
+
+	return n, nil
+}
+
+func (t *Terminal) Write(buf []byte) (n int, err error) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	if t.cursorX == 0 && t.cursorY == 0 {
+		// This is the easy case: there's nothing on the screen that we
+		// have to move out of the way.
+		return writeWithCRLF(t.c, buf)
+	}
+
+	// We have a prompt and possibly user input on the screen. We
+	// have to clear it first.
+	t.move(0 /* up */, 0 /* down */, t.cursorX /* left */, 0 /* right */)
+	t.cursorX = 0
+	t.clearLineToRight()
+
+	for t.cursorY > 0 {
+		t.move(1 /* up */, 0, 0, 0)
+		t.cursorY--
+		t.clearLineToRight()
+	}
+
+	if _, err = t.c.Write(t.outBuf); err != nil {
+		return
+	}
+	t.outBuf = t.outBuf[:0]
+
+	if n, err = writeWithCRLF(t.c, buf); err != nil {
+		return
+	}
+
+	t.writeLine(t.prompt)
+	if t.echo {
+		t.writeLine(t.line)
+	}
+
+	t.moveCursorToPos(t.pos)
+
+	if _, err = t.c.Write(t.outBuf); err != nil {
+		return
+	}
+	t.outBuf = t.outBuf[:0]
+	return
+}
+
+// ReadPassword temporarily changes the prompt and reads a password, without
+// echo, from the terminal.
+func (t *Terminal) ReadPassword(prompt string) (line string, err error) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	oldPrompt := t.prompt
+	t.prompt = []rune(prompt)
+	t.echo = false
+
+	line, err = t.readLine()
+
+	t.prompt = oldPrompt
+	t.echo = true
+
+	return
+}
+
+// ReadLine returns a line of input from the terminal.
+func (t *Terminal) ReadLine() (line string, err error) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	return t.readLine()
+}
+
+func (t *Terminal) readLine() (line string, err error) {
+	// t.lock must be held at this point
+
+	if t.cursorX == 0 && t.cursorY == 0 {
+		t.writeLine(t.prompt)
+		t.c.Write(t.outBuf)
+		t.outBuf = t.outBuf[:0]
+	}
+
+	lineIsPasted := t.pasteActive
+
+	for {
+		rest := t.remainder
+		lineOk := false
+		for !lineOk {
+			var key rune
+			key, rest = bytesToKey(rest, t.pasteActive)
+			if key == utf8.RuneError {
+				break
+			}
+			if !t.pasteActive {
+				if key == keyCtrlD {
+					if len(t.line) == 0 {
+						return "", io.EOF
+					}
+				}
+				if key == keyPasteStart {
+					t.pasteActive = true
+					if len(t.line) == 0 {
+						lineIsPasted = true
+					}
+					continue
+				}
+			} else if key == keyPasteEnd {
+				t.pasteActive = false
+				continue
+			}
+			if !t.pasteActive {
+				lineIsPasted = false
+			}
+			line, lineOk = t.handleKey(key)
+		}
+		if len(rest) > 0 {
+			n := copy(t.inBuf[:], rest)
+			t.remainder = t.inBuf[:n]
+		} else {
+			t.remainder = nil
+		}
+		t.c.Write(t.outBuf)
+		t.outBuf = t.outBuf[:0]
+		if lineOk {
+			if t.echo {
+				t.historyIndex = -1
+				t.history.Add(line)
+			}
+			if lineIsPasted {
+				err = ErrPasteIndicator
+			}
+			return
+		}
+
+		// t.remainder is a slice at the beginning of t.inBuf
+		// containing a partial key sequence
+		readBuf := t.inBuf[len(t.remainder):]
+		var n int
+
+		t.lock.Unlock()
+		n, err = t.c.Read(readBuf)
+		t.lock.Lock()
+
+		if err != nil {
+			return
+		}
+
+		t.remainder = t.inBuf[:n+len(t.remainder)]
+	}
+}
+
+// SetPrompt sets the prompt to be used when reading subsequent lines.
+func (t *Terminal) SetPrompt(prompt string) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	t.prompt = []rune(prompt)
+}
+
+func (t *Terminal) clearAndRepaintLinePlusNPrevious(numPrevLines int) {
+	// Move cursor to column zero at the start of the line.
+	t.move(t.cursorY, 0, t.cursorX, 0)
+	t.cursorX, t.cursorY = 0, 0
+	t.clearLineToRight()
+	for t.cursorY < numPrevLines {
+		// Move down a line
+		t.move(0, 1, 0, 0)
+		t.cursorY++
+		t.clearLineToRight()
+	}
+	// Move back to beginning.
+	t.move(t.cursorY, 0, 0, 0)
+	t.cursorX, t.cursorY = 0, 0
+
+	t.queue(t.prompt)
+	t.advanceCursor(visualLength(t.prompt))
+	t.writeLine(t.line)
+	t.moveCursorToPos(t.pos)
+}
+
+func (t *Terminal) SetSize(width, height int) error {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
+	if width == 0 {
+		width = 1
+	}
+
+	oldWidth := t.termWidth
+	t.termWidth, t.termHeight = width, height
+
+	switch {
+	case width == oldWidth:
+		// If the width didn't change then nothing else needs to be
+		// done.
+		return nil
+	case len(t.line) == 0 && t.cursorX == 0 && t.cursorY == 0:
+		// If there is nothing on current line and no prompt printed,
+		// just do nothing
+		return nil
+	case width < oldWidth:
+		// Some terminals (e.g. xterm) will truncate lines that were
+		// too long when shinking. Others, (e.g. gnome-terminal) will
+		// attempt to wrap them. For the former, repainting t.maxLine
+		// works great, but that behaviour goes badly wrong in the case
+		// of the latter because they have doubled every full line.
+
+		// We assume that we are working on a terminal that wraps lines
+		// and adjust the cursor position based on every previous line
+		// wrapping and turning into two. This causes the prompt on
+		// xterms to move upwards, which isn't great, but it avoids a
+		// huge mess with gnome-terminal.
+		if t.cursorX >= t.termWidth {
+			t.cursorX = t.termWidth - 1
+		}
+		t.cursorY *= 2
+		t.clearAndRepaintLinePlusNPrevious(t.maxLine * 2)
+	case width > oldWidth:
+		// If the terminal expands then our position calculations will
+		// be wrong in the future because we think the cursor is
+		// |t.pos| chars into the string, but there will be a gap at
+		// the end of any wrapped line.
+		//
+		// But the position will actually be correct until we move, so
+		// we can move back to the beginning and repaint everything.
+		t.clearAndRepaintLinePlusNPrevious(t.maxLine)
+	}
+
+	_, err := t.c.Write(t.outBuf)
+	t.outBuf = t.outBuf[:0]
+	return err
+}
+
+type pasteIndicatorError struct{}
+
+func (pasteIndicatorError) Error() string {
+	return "terminal: ErrPasteIndicator not correctly handled"
+}
+
+// ErrPasteIndicator may be returned from ReadLine as the error, in addition
+// to valid line data. It indicates that bracketed paste mode is enabled and
+// that the returned line consists only of pasted data. Programs may wish to
+// interpret pasted data more literally than typed data.
+var ErrPasteIndicator = pasteIndicatorError{}
+
+// SetBracketedPasteMode requests that the terminal bracket paste operations
+// with markers. Not all terminals support this but, if it is supported, then
+// enabling this mode will stop any autocomplete callback from running due to
+// pastes. Additionally, any lines that are completely pasted will be returned
+// from ReadLine with the error set to ErrPasteIndicator.
+func (t *Terminal) SetBracketedPasteMode(on bool) {
+	if on {
+		io.WriteString(t.c, "\x1b[?2004h")
+	} else {
+		io.WriteString(t.c, "\x1b[?2004l")
+	}
+}
+
+// stRingBuffer is a ring buffer of strings.
+type stRingBuffer struct {
+	// entries contains max elements.
+	entries []string
+	max     int
+	// head contains the index of the element most recently added to the ring.
+	head int
+	// size contains the number of elements in the ring.
+	size int
+}
+
+func (s *stRingBuffer) Add(a string) {
+	if s.entries == nil {
+		const defaultNumEntries = 100
+		s.entries = make([]string, defaultNumEntries)
+		s.max = defaultNumEntries
+	}
+
+	s.head = (s.head + 1) % s.max
+	s.entries[s.head] = a
+	if s.size < s.max {
+		s.size++
+	}
+}
+
+// NthPreviousEntry returns the value passed to the nth previous call to Add.
+// If n is zero then the immediately prior value is returned, if one, then the
+// next most recent, and so on. If such an element doesn't exist then ok is
+// false.
+func (s *stRingBuffer) NthPreviousEntry(n int) (value string, ok bool) {
+	if n >= s.size {
+		return "", false
+	}
+	index := s.head - n
+	if index < 0 {
+		index += s.max
+	}
+	return s.entries[index], true
+}
+
+// readPasswordLine reads from reader until it finds \n or io.EOF.
+// The slice returned does not include the \n.
+// readPasswordLine also ignores any \r it finds.
+func readPasswordLine(reader io.Reader) ([]byte, error) {
+	var buf [1]byte
+	var ret []byte
+
+	for {
+		n, err := reader.Read(buf[:])
+		if n > 0 {
+			switch buf[0] {
+			case '\n':
+				return ret, nil
+			case '\r':
+				// remove \r from passwords on Windows
+			default:
+				ret = append(ret, buf[0])
+			}
+			continue
+		}
+		if err != nil {
+			if err == io.EOF && len(ret) > 0 {
+				return ret, nil
+			}
+			return ret, err
+		}
+	}
+}

sshd/terminal/terminal_test.go

@@ -0,0 +1,364 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build aix darwin dragonfly freebsd linux,!appengine netbsd openbsd windows plan9 solaris
+
+package terminal
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"runtime"
+	"testing"
+)
+
+type MockTerminal struct {
+	toSend       []byte
+	bytesPerRead int
+	received     []byte
+}
+
+func (c *MockTerminal) Read(data []byte) (n int, err error) {
+	n = len(data)
+	if n == 0 {
+		return
+	}
+	if n > len(c.toSend) {
+		n = len(c.toSend)
+	}
+	if n == 0 {
+		return 0, io.EOF
+	}
+	if c.bytesPerRead > 0 && n > c.bytesPerRead {
+		n = c.bytesPerRead
+	}
+	copy(data, c.toSend[:n])
+	c.toSend = c.toSend[n:]
+	return
+}
+
+func (c *MockTerminal) Write(data []byte) (n int, err error) {
+	c.received = append(c.received, data...)
+	return len(data), nil
+}
+
+func TestClose(t *testing.T) {
+	c := &MockTerminal{}
+	ss := NewTerminal(c, "> ")
+	line, err := ss.ReadLine()
+	if line != "" {
+		t.Errorf("Expected empty line but got: %s", line)
+	}
+	if err != io.EOF {
+		t.Errorf("Error should have been EOF but got: %s", err)
+	}
+}
+
+var keyPressTests = []struct {
+	in             string
+	line           string
+	err            error
+	throwAwayLines int
+}{
+	{
+		err: io.EOF,
+	},
+	{
+		in:   "\r",
+		line: "",
+	},
+	{
+		in:   "foo\r",
+		line: "foo",
+	},
+	{
+		in:   "a\x1b[Cb\r", // right
+		line: "ab",
+	},
+	{
+		in:   "a\x1b[Db\r", // left
+		line: "ba",
+	},
+	{
+		in:   "a\177b\r", // backspace
+		line: "b",
+	},
+	{
+		in: "\x1b[A\r", // up
+	},
+	{
+		in: "\x1b[B\r", // down
+	},
+	{
+		in: "\016\r", // ^P
+	},
+	{
+		in: "\014\r", // ^N
+	},
+	{
+		in:   "line\x1b[A\x1b[B\r", // up then down
+		line: "line",
+	},
+	{
+		in:             "line1\rline2\x1b[A\r", // recall previous line.
+		line:           "line1",
+		throwAwayLines: 1,
+	},
+	{
+		// recall two previous lines and append.
+		in:             "line1\rline2\rline3\x1b[A\x1b[Axxx\r",
+		line:           "line1xxx",
+		throwAwayLines: 2,
+	},
+	{
+		// Ctrl-A to move to beginning of line followed by ^K to kill
+		// line.
+		in:   "a b \001\013\r",
+		line: "",
+	},
+	{
+		// Ctrl-A to move to beginning of line, Ctrl-E to move to end,
+		// finally ^K to kill nothing.
+		in:   "a b \001\005\013\r",
+		line: "a b ",
+	},
+	{
+		in:   "\027\r",
+		line: "",
+	},
+	{
+		in:   "a\027\r",
+		line: "",
+	},
+	{
+		in:   "a \027\r",
+		line: "",
+	},
+	{
+		in:   "a b\027\r",
+		line: "a ",
+	},
+	{
+		in:   "a b \027\r",
+		line: "a ",
+	},
+	{
+		in:   "one two thr\x1b[D\027\r",
+		line: "one two r",
+	},
+	{
+		in:   "\013\r",
+		line: "",
+	},
+	{
+		in:   "a\013\r",
+		line: "a",
+	},
+	{
+		in:   "ab\x1b[D\013\r",
+		line: "a",
+	},
+	{
+		in:   "Ξεσκεπάζω\r",
+		line: "Ξεσκεπάζω",
+	},
+	{
+		in:             "£\r\x1b[A\177\r", // non-ASCII char, enter, up, backspace.
+		line:           "",
+		throwAwayLines: 1,
+	},
+	{
+		in:             "£\r££\x1b[A\x1b[B\177\r", // non-ASCII char, enter, 2x non-ASCII, up, down, backspace, enter.
+		line:           "£",
+		throwAwayLines: 1,
+	},
+	{
+		// Ctrl-D at the end of the line should be ignored.
+		in:   "a\004\r",
+		line: "a",
+	},
+	{
+		// a, b, left, Ctrl-D should erase the b.
+		in:   "ab\x1b[D\004\r",
+		line: "a",
+	},
+	{
+		// a, b, c, d, left, left, ^U should erase to the beginning of
+		// the line.
+		in:   "abcd\x1b[D\x1b[D\025\r",
+		line: "cd",
+	},
+	{
+		// Bracketed paste mode: control sequences should be returned
+		// verbatim in paste mode.
+		in:   "abc\x1b[200~de\177f\x1b[201~\177\r",
+		line: "abcde\177",
+	},
+	{
+		// Enter in bracketed paste mode should still work.
+		in:             "abc\x1b[200~d\refg\x1b[201~h\r",
+		line:           "efgh",
+		throwAwayLines: 1,
+	},
+	{
+		// Lines consisting entirely of pasted data should be indicated as such.
+		in:   "\x1b[200~a\r",
+		line: "a",
+		err:  ErrPasteIndicator,
+	},
+}
+
+func TestKeyPresses(t *testing.T) {
+	for i, test := range keyPressTests {
+		for j := 1; j < len(test.in); j++ {
+			c := &MockTerminal{
+				toSend:       []byte(test.in),
+				bytesPerRead: j,
+			}
+			ss := NewTerminal(c, "> ")
+			for k := 0; k < test.throwAwayLines; k++ {
+				_, err := ss.ReadLine()
+				if err != nil {
+					t.Errorf("Throwaway line %d from test %d resulted in error: %s", k, i, err)
+				}
+			}
+			line, err := ss.ReadLine()
+			if line != test.line {
+				t.Errorf("Line resulting from test %d (%d bytes per read) was '%s', expected '%s'", i, j, line, test.line)
+				break
+			}
+			if err != test.err {
+				t.Errorf("Error resulting from test %d (%d bytes per read) was '%v', expected '%v'", i, j, err, test.err)
+				break
+			}
+		}
+	}
+}
+
+func TestPasswordNotSaved(t *testing.T) {
+	c := &MockTerminal{
+		toSend:       []byte("password\r\x1b[A\r"),
+		bytesPerRead: 1,
+	}
+	ss := NewTerminal(c, "> ")
+	pw, _ := ss.ReadPassword("> ")
+	if pw != "password" {
+		t.Fatalf("failed to read password, got %s", pw)
+	}
+	line, _ := ss.ReadLine()
+	if len(line) > 0 {
+		t.Fatalf("password was saved in history")
+	}
+}
+
+var setSizeTests = []struct {
+	width, height int
+}{
+	{40, 13},
+	{80, 24},
+	{132, 43},
+}
+
+func TestTerminalSetSize(t *testing.T) {
+	for _, setSize := range setSizeTests {
+		c := &MockTerminal{
+			toSend:       []byte("password\r\x1b[A\r"),
+			bytesPerRead: 1,
+		}
+		ss := NewTerminal(c, "> ")
+		ss.SetSize(setSize.width, setSize.height)
+		pw, _ := ss.ReadPassword("Password: ")
+		if pw != "password" {
+			t.Fatalf("failed to read password, got %s", pw)
+		}
+		if string(c.received) != "Password: \r\n" {
+			t.Errorf("failed to set the temporary prompt expected %q, got %q", "Password: ", c.received)
+		}
+	}
+}
+
+func TestReadPasswordLineEnd(t *testing.T) {
+	var tests = []struct {
+		input string
+		want  string
+	}{
+		{"\n", ""},
+		{"\r\n", ""},
+		{"test\r\n", "test"},
+		{"testtesttesttes\n", "testtesttesttes"},
+		{"testtesttesttes\r\n", "testtesttesttes"},
+		{"testtesttesttesttest\n", "testtesttesttesttest"},
+		{"testtesttesttesttest\r\n", "testtesttesttesttest"},
+	}
+	for _, test := range tests {
+		buf := new(bytes.Buffer)
+		if _, err := buf.WriteString(test.input); err != nil {
+			t.Fatal(err)
+		}
+
+		have, err := readPasswordLine(buf)
+		if err != nil {
+			t.Errorf("readPasswordLine(%q) failed: %v", test.input, err)
+			continue
+		}
+		if string(have) != test.want {
+			t.Errorf("readPasswordLine(%q) returns %q, but %q is expected", test.input, string(have), test.want)
+			continue
+		}
+
+		if _, err = buf.WriteString(test.input); err != nil {
+			t.Fatal(err)
+		}
+		have, err = readPasswordLine(buf)
+		if err != nil {
+			t.Errorf("readPasswordLine(%q) failed: %v", test.input, err)
+			continue
+		}
+		if string(have) != test.want {
+			t.Errorf("readPasswordLine(%q) returns %q, but %q is expected", test.input, string(have), test.want)
+			continue
+		}
+	}
+}
+
+func TestMakeRawState(t *testing.T) {
+	fd := int(os.Stdout.Fd())
+	if !IsTerminal(fd) {
+		t.Skip("stdout is not a terminal; skipping test")
+	}
+
+	st, err := GetState(fd)
+	if err != nil {
+		t.Fatalf("failed to get terminal state from GetState: %s", err)
+	}
+
+	if runtime.GOOS == "darwin" && (runtime.GOARCH == "arm" || runtime.GOARCH == "arm64") {
+		t.Skip("MakeRaw not allowed on iOS; skipping test")
+	}
+
+	defer Restore(fd, st)
+	raw, err := MakeRaw(fd)
+	if err != nil {
+		t.Fatalf("failed to get terminal state from MakeRaw: %s", err)
+	}
+
+	if *st != *raw {
+		t.Errorf("states do not match; was %v, expected %v", raw, st)
+	}
+}
+
+func TestOutputNewlines(t *testing.T) {
+	// \n should be changed to \r\n in terminal output.
+	buf := new(bytes.Buffer)
+	term := NewTerminal(buf, ">")
+
+	term.Write([]byte("1\n2\n"))
+	output := string(buf.Bytes())
+	const expected = "1\r\n2\r\n"
+
+	if output != expected {
+		t.Errorf("incorrect output: was %q, expected %q", output, expected)
+	}
+}

sshd/terminal/util.go

@@ -0,0 +1,114 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build aix darwin dragonfly freebsd linux,!appengine netbsd openbsd
+
+// Package terminal provides support functions for dealing with terminals, as
+// commonly found on UNIX systems.
+//
+// Putting a terminal into raw mode is the most common requirement:
+//
+// 	oldState, err := terminal.MakeRaw(0)
+// 	if err != nil {
+// 	        panic(err)
+// 	}
+// 	defer terminal.Restore(0, oldState)
+package terminal // import "golang.org/x/crypto/ssh/terminal"
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+// State contains the state of a terminal.
+type State struct {
+	termios unix.Termios
+}
+
+// IsTerminal returns whether the given file descriptor is a terminal.
+func IsTerminal(fd int) bool {
+	_, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
+	return err == nil
+}
+
+// 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)
+}
+
+// GetSize returns the dimensions of the given terminal.
+func GetSize(fd int) (width, height int, err error) {
+	ws, err := unix.IoctlGetWinsize(fd, unix.TIOCGWINSZ)
+	if err != nil {
+		return -1, -1, err
+	}
+	return int(ws.Col), int(ws.Row), nil
+}
+
+// passwordReader is an io.Reader that reads from a specific file descriptor.
+type passwordReader int
+
+func (r passwordReader) Read(buf []byte) (int, error) {
+	return unix.Read(int(r), buf)
+}
+
+// ReadPassword reads a line of input from a terminal without local echo.  This
+// is commonly used for inputting passwords and other sensitive data. The slice
+// returned does not include the \n.
+func ReadPassword(fd int) ([]byte, error) {
+	termios, err := unix.IoctlGetTermios(fd, ioctlReadTermios)
+	if err != nil {
+		return nil, err
+	}
+
+	newState := *termios
+	newState.Lflag &^= unix.ECHO
+	newState.Lflag |= unix.ICANON | unix.ISIG
+	newState.Iflag |= unix.ICRNL
+	if err := unix.IoctlSetTermios(fd, ioctlWriteTermios, &newState); err != nil {
+		return nil, err
+	}
+
+	defer unix.IoctlSetTermios(fd, ioctlWriteTermios, termios)
+
+	return readPasswordLine(passwordReader(fd))
+}

sshd/terminal/util_aix.go

@@ -0,0 +1,12 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build aix
+
+package terminal
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TCGETS
+const ioctlWriteTermios = unix.TCSETS

sshd/terminal/util_bsd.go

@@ -0,0 +1,12 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build darwin dragonfly freebsd netbsd openbsd
+
+package terminal
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TIOCGETA
+const ioctlWriteTermios = unix.TIOCSETA

sshd/terminal/util_linux.go

@@ -0,0 +1,10 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package terminal
+
+import "golang.org/x/sys/unix"
+
+const ioctlReadTermios = unix.TCGETS
+const ioctlWriteTermios = unix.TCSETS

sshd/terminal/util_plan9.go

@@ -0,0 +1,58 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package terminal provides support functions for dealing with terminals, as
+// commonly found on UNIX systems.
+//
+// Putting a terminal into raw mode is the most common requirement:
+//
+// 	oldState, err := terminal.MakeRaw(0)
+// 	if err != nil {
+// 	        panic(err)
+// 	}
+// 	defer terminal.Restore(0, oldState)
+package terminal
+
+import (
+	"fmt"
+	"runtime"
+)
+
+type State struct{}
+
+// IsTerminal returns whether the given file descriptor is a terminal.
+func IsTerminal(fd int) bool {
+	return false
+}
+
+// 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) {
+	return nil, fmt.Errorf("terminal: MakeRaw not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}
+
+// 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) {
+	return nil, fmt.Errorf("terminal: GetState not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}
+
+// Restore restores the terminal connected to the given file descriptor to a
+// previous state.
+func Restore(fd int, state *State) error {
+	return fmt.Errorf("terminal: Restore not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}
+
+// GetSize returns the dimensions of the given terminal.
+func GetSize(fd int) (width, height int, err error) {
+	return 0, 0, fmt.Errorf("terminal: GetSize not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}
+
+// ReadPassword reads a line of input from a terminal without local echo.  This
+// is commonly used for inputting passwords and other sensitive data. The slice
+// returned does not include the \n.
+func ReadPassword(fd int) ([]byte, error) {
+	return nil, fmt.Errorf("terminal: ReadPassword not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}

sshd/terminal/util_solaris.go

@@ -0,0 +1,124 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build solaris
+
+package terminal // import "golang.org/x/crypto/ssh/terminal"
+
+import (
+	"golang.org/x/sys/unix"
+	"io"
+	"syscall"
+)
+
+// State contains the state of a terminal.
+type State struct {
+	termios unix.Termios
+}
+
+// IsTerminal returns whether the given file descriptor is a terminal.
+func IsTerminal(fd int) bool {
+	_, err := unix.IoctlGetTermio(fd, unix.TCGETA)
+	return err == nil
+}
+
+// ReadPassword reads a line of input from a terminal without local echo.  This
+// is commonly used for inputting passwords and other sensitive data. The slice
+// returned does not include the \n.
+func ReadPassword(fd int) ([]byte, error) {
+	// see also: http://src.illumos.org/source/xref/illumos-gate/usr/src/lib/libast/common/uwin/getpass.c
+	val, err := unix.IoctlGetTermios(fd, unix.TCGETS)
+	if err != nil {
+		return nil, err
+	}
+	oldState := *val
+
+	newState := oldState
+	newState.Lflag &^= syscall.ECHO
+	newState.Lflag |= syscall.ICANON | syscall.ISIG
+	newState.Iflag |= syscall.ICRNL
+	err = unix.IoctlSetTermios(fd, unix.TCSETS, &newState)
+	if err != nil {
+		return nil, err
+	}
+
+	defer unix.IoctlSetTermios(fd, unix.TCSETS, &oldState)
+
+	var buf [16]byte
+	var ret []byte
+	for {
+		n, err := syscall.Read(fd, buf[:])
+		if err != nil {
+			return nil, err
+		}
+		if n == 0 {
+			if len(ret) == 0 {
+				return nil, io.EOF
+			}
+			break
+		}
+		if buf[n-1] == '\n' {
+			n--
+		}
+		ret = append(ret, buf[:n]...)
+		if n < len(buf) {
+			break
+		}
+	}
+
+	return ret, nil
+}
+
+// MakeRaw puts 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.
+// see http://cr.illumos.org/~webrev/andy_js/1060/
+func MakeRaw(fd int) (*State, error) {
+	termios, err := unix.IoctlGetTermios(fd, unix.TCGETS)
+	if err != nil {
+		return nil, err
+	}
+
+	oldState := State{termios: *termios}
+
+	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, unix.TCSETS, termios); err != nil {
+		return nil, err
+	}
+
+	return &oldState, nil
+}
+
+// Restore restores the terminal connected to the given file descriptor to a
+// previous state.
+func Restore(fd int, oldState *State) error {
+	return unix.IoctlSetTermios(fd, unix.TCSETS, &oldState.termios)
+}
+
+// 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, unix.TCGETS)
+	if err != nil {
+		return nil, err
+	}
+
+	return &State{termios: *termios}, nil
+}
+
+// GetSize returns the dimensions of the given terminal.
+func GetSize(fd int) (width, height int, err error) {
+	ws, err := unix.IoctlGetWinsize(fd, unix.TIOCGWINSZ)
+	if err != nil {
+		return 0, 0, err
+	}
+	return int(ws.Col), int(ws.Row), nil
+}

sshd/terminal/util_windows.go

@@ -0,0 +1,103 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows
+
+// Package terminal provides support functions for dealing with terminals, as
+// commonly found on UNIX systems.
+//
+// Putting a terminal into raw mode is the most common requirement:
+//
+// 	oldState, err := terminal.MakeRaw(0)
+// 	if err != nil {
+// 	        panic(err)
+// 	}
+// 	defer terminal.Restore(0, oldState)
+package terminal
+
+import (
+	"os"
+
+	"golang.org/x/sys/windows"
+)
+
+type State struct {
+	mode uint32
+}
+
+// IsTerminal returns whether the given file descriptor is a terminal.
+func IsTerminal(fd int) bool {
+	var st uint32
+	err := windows.GetConsoleMode(windows.Handle(fd), &st)
+	return err == nil
+}
+
+// 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) {
+	var st uint32
+	if err := windows.GetConsoleMode(windows.Handle(fd), &st); err != nil {
+		return nil, err
+	}
+	raw := st &^ (windows.ENABLE_ECHO_INPUT | windows.ENABLE_PROCESSED_INPUT | windows.ENABLE_LINE_INPUT | windows.ENABLE_PROCESSED_OUTPUT)
+	if err := windows.SetConsoleMode(windows.Handle(fd), raw); err != nil {
+		return nil, err
+	}
+	return &State{st}, 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) {
+	var st uint32
+	if err := windows.GetConsoleMode(windows.Handle(fd), &st); err != nil {
+		return nil, err
+	}
+	return &State{st}, nil
+}
+
+// Restore restores the terminal connected to the given file descriptor to a
+// previous state.
+func Restore(fd int, state *State) error {
+	return windows.SetConsoleMode(windows.Handle(fd), state.mode)
+}
+
+// GetSize returns the dimensions of the given terminal.
+func GetSize(fd int) (width, height int, err error) {
+	var info windows.ConsoleScreenBufferInfo
+	if err := windows.GetConsoleScreenBufferInfo(windows.Handle(fd), &info); err != nil {
+		return 0, 0, err
+	}
+	return int(info.Size.X), int(info.Size.Y), nil
+}
+
+// ReadPassword reads a line of input from a terminal without local echo.  This
+// is commonly used for inputting passwords and other sensitive data. The slice
+// returned does not include the \n.
+func ReadPassword(fd int) ([]byte, error) {
+	var st uint32
+	if err := windows.GetConsoleMode(windows.Handle(fd), &st); err != nil {
+		return nil, err
+	}
+	old := st
+
+	st &^= (windows.ENABLE_ECHO_INPUT)
+	st |= (windows.ENABLE_PROCESSED_INPUT | windows.ENABLE_LINE_INPUT | windows.ENABLE_PROCESSED_OUTPUT)
+	if err := windows.SetConsoleMode(windows.Handle(fd), st); err != nil {
+		return nil, err
+	}
+
+	defer windows.SetConsoleMode(windows.Handle(fd), old)
+
+	var h windows.Handle
+	p, _ := windows.GetCurrentProcess()
+	if err := windows.DuplicateHandle(p, windows.Handle(fd), p, &h, 0, false, windows.DUPLICATE_SAME_ACCESS); err != nil {
+		return nil, err
+	}
+
+	f := os.NewFile(uintptr(h), "stdin")
+	defer f.Close()
+	return readPasswordLine(f)
+}