Lib/getpass.py

   1 """Utilities to get a password and/or the current user name.
   2
   3 getpass(prompt[, stream]) - Prompt for a password, with echo turned off.
   4 getuser() - Get the user name from the environment or password database.
   5
   6 GetPassWarning - This UserWarning is issued when getpass() cannot prevent
   7                  echoing of the password contents while reading.
   8
   9 On Windows, the msvcrt module will be used.
  10 On the Mac EasyDialogs.AskPassword is used, if available.
  11
  12 """
  13
  14 # Authors: Piers Lauder (original)
  15 #          Guido van Rossum (Windows support and cleanup)
  16 #          Gregory P. Smith (tty support & GetPassWarning)
  17
  18 import os, sys, warnings
  19
  20 __all__ = ["getpass","getuser","GetPassWarning"]
  21
  22
  23 class GetPassWarning(UserWarning): pass
  24
  25
  26 def unix_getpass(prompt='Password: ', stream=None):
  27     """Prompt for a password, with echo turned off.
  28
  29     Args:
  30       prompt: Written on stream to ask for the input.  Default: 'Password: '
  31       stream: A writable file object to display the prompt.  Defaults to
  32               the tty.  If no tty is available defaults to sys.stderr.
  33     Returns:
  34       The seKr3t input.
  35     Raises:
  36       EOFError: If our input tty or stdin was closed.
  37       GetPassWarning: When we were unable to turn echo off on the input.
  38
  39     Always restores terminal settings before returning.
  40     """
  41     fd = None
  42     tty = None
  43     try:
  44         # Always try reading and writing directly on the tty first.
  45         fd = os.open('/dev/tty', os.O_RDWR|os.O_NOCTTY)
  46         tty = os.fdopen(fd, 'w+', 1)
  47         input = tty
  48         if not stream:
  49             stream = tty
  50     except EnvironmentError as e:
  51         # If that fails, see if stdin can be controlled.
  52         try:
  53             fd = sys.stdin.fileno()
  54         except:
  55             passwd = fallback_getpass(prompt, stream)
  56         input = sys.stdin
  57         if not stream:
  58             stream = sys.stderr
  59
  60     if fd is not None:
  61         passwd = None
  62         try:
  63             old = termios.tcgetattr(fd)     # a copy to save
  64             new = old[:]
  65             new[3] &= ~termios.ECHO  # 3 == 'lflags'
  66             try:
  67                 termios.tcsetattr(fd, termios.TCSADRAIN, new)
  68                 passwd = _raw_input(prompt, stream, input=input)
  69             finally:
  70                 termios.tcsetattr(fd, termios.TCSADRAIN, old)
  71         except termios.error as e:
  72             if passwd is not None:
  73                 # _raw_input succeeded.  The final tcsetattr failed.  Reraise
  74                 # instead of leaving the terminal in an unknown state.
  75                 raise
  76             # We can't control the tty or stdin.  Give up and use normal IO.
  77             # fallback_getpass() raises an appropriate warning.
  78             del input, tty  # clean up unused file objects before blocking
  79             passwd = fallback_getpass(prompt, stream)
  80
  81     stream.write('\n')
  82     return passwd
  83
  84
  85 def win_getpass(prompt='Password: ', stream=None):
  86     """Prompt for password with echo off, using Windows getch()."""
  87     if sys.stdin is not sys.__stdin__:
  88         return fallback_getpass(prompt, stream)
  89     import msvcrt
  90     for c in prompt:
  91         msvcrt.putwch(c)
  92     pw = ""
  93     while 1:
  94         c = msvcrt.getwch()
  95         if c == '\r' or c == '\n':
  96             break
  97         if c == '\003':
  98             raise KeyboardInterrupt
  99         if c == '\b':
 100             pw = pw[:-1]
 101         else:
 102             pw = pw + c
 103     msvcrt.putwch('\r')
 104     msvcrt.putwch('\n')
 105     return pw
 106
 107
 108 def fallback_getpass(prompt='Password: ', stream=None):
 109     warnings.warn("Can not control echo on the terminal.", GetPassWarning,
 110                   stacklevel=2)
 111     if not stream:
 112         stream = sys.stderr
 113     print("Warning: Password input may be echoed.", file=stream)
 114     return _raw_input(prompt, stream)
 115
 116
 117 def _raw_input(prompt="", stream=None, input=None):
 118     # This doesn't save the string in the GNU readline history.
 119     if not stream:
 120         stream = sys.stderr
 121     if not input:
 122         input = sys.stdin
 123     prompt = str(prompt)
 124     if prompt:
 125         stream.write(prompt)
 126         stream.flush()
 127     line = input.readline()
 128     if not line:
 129         raise EOFError
 130     if line[-1] == '\n':
 131         line = line[:-1]
 132     return line
 133
 134
 135 def getuser():
 136     """Get the username from the environment or password database.
 137
 138     First try various environment variables, then the password
 139     database.  This works on Windows as long as USERNAME is set.
 140
 141     """
 142
 143     import os
 144
 145     for name in ('LOGNAME', 'USER', 'LNAME', 'USERNAME'):
 146         user = os.environ.get(name)
 147         if user:
 148             return user
 149
 150     # If this fails, the exception will "explain" why
 151     import pwd
 152     return pwd.getpwuid(os.getuid())[0]
 153
 154 # Bind the name getpass to the appropriate function
 155 try:
 156     import termios
 157     # it's possible there is an incompatible termios from the
 158     # McMillan Installer, make sure we have a UNIX-compatible termios
 159     termios.tcgetattr, termios.tcsetattr
 160 except (ImportError, AttributeError):
 161     try:
 162         import msvcrt
 163     except ImportError:
 164         try:
 165             from EasyDialogs import AskPassword
 166         except ImportError:
 167             getpass = fallback_getpass
 168         else:
 169             getpass = AskPassword
 170     else:
 171         getpass = win_getpass
 172 else:
 173     getpass = unix_getpass