github.com/glycerine/xcryptossh@v7.0.4+incompatible/terminal/util.go (about)

     1  // Copyright 2011 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // +build darwin dragonfly freebsd linux,!appengine netbsd openbsd
     6  
     7  // Package terminal provides support functions for dealing with terminals, as
     8  // commonly found on UNIX systems.
     9  //
    10  // Putting a terminal into raw mode is the most common requirement:
    11  //
    12  // 	oldState, err := terminal.MakeRaw(0)
    13  // 	if err != nil {
    14  // 	        panic(err)
    15  // 	}
    16  // 	defer terminal.Restore(0, oldState)
    17  package terminal
    18  
    19  import (
    20  	"syscall"
    21  	"unsafe"
    22  )
    23  
    24  // State contains the state of a terminal.
    25  type State struct {
    26  	termios syscall.Termios
    27  }
    28  
    29  // IsTerminal returns true if the given file descriptor is a terminal.
    30  func IsTerminal(fd int) bool {
    31  	var termios syscall.Termios
    32  	_, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlReadTermios, uintptr(unsafe.Pointer(&termios)), 0, 0, 0)
    33  	return err == 0
    34  }
    35  
    36  // MakeRaw put the terminal connected to the given file descriptor into raw
    37  // mode and returns the previous state of the terminal so that it can be
    38  // restored.
    39  func MakeRaw(fd int) (*State, error) {
    40  	var oldState State
    41  	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlReadTermios, uintptr(unsafe.Pointer(&oldState.termios)), 0, 0, 0); err != 0 {
    42  		return nil, err
    43  	}
    44  
    45  	newState := oldState.termios
    46  	// This attempts to replicate the behaviour documented for cfmakeraw in
    47  	// the termios(3) manpage.
    48  	newState.Iflag &^= syscall.IGNBRK | syscall.BRKINT | syscall.PARMRK | syscall.ISTRIP | syscall.INLCR | syscall.IGNCR | syscall.ICRNL | syscall.IXON
    49  	newState.Oflag &^= syscall.OPOST
    50  	newState.Lflag &^= syscall.ECHO | syscall.ECHONL | syscall.ICANON | syscall.ISIG | syscall.IEXTEN
    51  	newState.Cflag &^= syscall.CSIZE | syscall.PARENB
    52  	newState.Cflag |= syscall.CS8
    53  	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlWriteTermios, uintptr(unsafe.Pointer(&newState)), 0, 0, 0); err != 0 {
    54  		return nil, err
    55  	}
    56  
    57  	return &oldState, nil
    58  }
    59  
    60  // GetState returns the current state of a terminal which may be useful to
    61  // restore the terminal after a signal.
    62  func GetState(fd int) (*State, error) {
    63  	var oldState State
    64  	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlReadTermios, uintptr(unsafe.Pointer(&oldState.termios)), 0, 0, 0); err != 0 {
    65  		return nil, err
    66  	}
    67  
    68  	return &oldState, nil
    69  }
    70  
    71  // Restore restores the terminal connected to the given file descriptor to a
    72  // previous state.
    73  func Restore(fd int, state *State) error {
    74  	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlWriteTermios, uintptr(unsafe.Pointer(&state.termios)), 0, 0, 0); err != 0 {
    75  		return err
    76  	}
    77  	return nil
    78  }
    79  
    80  // GetSize returns the dimensions of the given terminal.
    81  func GetSize(fd int) (width, height int, err error) {
    82  	var dimensions [4]uint16
    83  
    84  	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), uintptr(syscall.TIOCGWINSZ), uintptr(unsafe.Pointer(&dimensions)), 0, 0, 0); err != 0 {
    85  		return -1, -1, err
    86  	}
    87  	return int(dimensions[1]), int(dimensions[0]), nil
    88  }
    89  
    90  // passwordReader is an io.Reader that reads from a specific file descriptor.
    91  type passwordReader int
    92  
    93  func (r passwordReader) Read(buf []byte) (int, error) {
    94  	return syscall.Read(int(r), buf)
    95  }
    96  
    97  // ReadPassword reads a line of input from a terminal without local echo.  This
    98  // is commonly used for inputting passwords and other sensitive data. The slice
    99  // returned does not include the \n.
   100  func ReadPassword(fd int) ([]byte, error) {
   101  	var oldState syscall.Termios
   102  	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlReadTermios, uintptr(unsafe.Pointer(&oldState)), 0, 0, 0); err != 0 {
   103  		return nil, err
   104  	}
   105  
   106  	newState := oldState
   107  	newState.Lflag &^= syscall.ECHO
   108  	newState.Lflag |= syscall.ICANON | syscall.ISIG
   109  	newState.Iflag |= syscall.ICRNL
   110  	if _, _, err := syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlWriteTermios, uintptr(unsafe.Pointer(&newState)), 0, 0, 0); err != 0 {
   111  		return nil, err
   112  	}
   113  
   114  	defer func() {
   115  		syscall.Syscall6(syscall.SYS_IOCTL, uintptr(fd), ioctlWriteTermios, uintptr(unsafe.Pointer(&oldState)), 0, 0, 0)
   116  	}()
   117  
   118  	return readPasswordLine(passwordReader(fd))
   119  }