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      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 
     11 """
     12 
     13 # Authors: Piers Lauder (original)
     14 #          Guido van Rossum (Windows support and cleanup)
     15 #          Gregory P. Smith (tty support & GetPassWarning)
     16 
     17 import contextlib
     18 import io
     19 import os
     20 import sys
     21 import warnings
     22 
     23 __all__ = ["getpass","getuser","GetPassWarning"]
     24 
     25 
     26 class GetPassWarning(UserWarning): pass
     27 
     28 
     29 def unix_getpass(prompt='Password: ', stream=None):
     30     """Prompt for a password, with echo turned off.
     31 
     32     Args:
     33       prompt: Written on stream to ask for the input.  Default: 'Password: '
     34       stream: A writable file object to display the prompt.  Defaults to
     35               the tty.  If no tty is available defaults to sys.stderr.
     36     Returns:
     37       The seKr3t input.
     38     Raises:
     39       EOFError: If our input tty or stdin was closed.
     40       GetPassWarning: When we were unable to turn echo off on the input.
     41 
     42     Always restores terminal settings before returning.
     43     """
     44     passwd = None
     45     with contextlib.ExitStack() as stack:
     46         try:
     47             # Always try reading and writing directly on the tty first.
     48             fd = os.open('/dev/tty', os.O_RDWR|os.O_NOCTTY)
     49             tty = io.FileIO(fd, 'w+')
     50             stack.enter_context(tty)
     51             input = io.TextIOWrapper(tty)
     52             stack.enter_context(input)
     53             if not stream:
     54                 stream = input
     55         except OSError as e:
     56             # If that fails, see if stdin can be controlled.
     57             stack.close()
     58             try:
     59                 fd = sys.stdin.fileno()
     60             except (AttributeError, ValueError):
     61                 fd = None
     62                 passwd = fallback_getpass(prompt, stream)
     63             input = sys.stdin
     64             if not stream:
     65                 stream = sys.stderr
     66 
     67         if fd is not None:
     68             try:
     69                 old = termios.tcgetattr(fd)     # a copy to save
     70                 new = old[:]
     71                 new[3] &= ~termios.ECHO  # 3 == 'lflags'
     72                 tcsetattr_flags = termios.TCSAFLUSH
     73                 if hasattr(termios, 'TCSASOFT'):
     74                     tcsetattr_flags |= termios.TCSASOFT
     75                 try:
     76                     termios.tcsetattr(fd, tcsetattr_flags, new)
     77                     passwd = _raw_input(prompt, stream, input=input)
     78                 finally:
     79                     termios.tcsetattr(fd, tcsetattr_flags, old)
     80                     stream.flush()  # issue7208
     81             except termios.error:
     82                 if passwd is not None:
     83                     # _raw_input succeeded.  The final tcsetattr failed.  Reraise
     84                     # instead of leaving the terminal in an unknown state.
     85                     raise
     86                 # We can't control the tty or stdin.  Give up and use normal IO.
     87                 # fallback_getpass() raises an appropriate warning.
     88                 if stream is not input:
     89                     # clean up unused file objects before blocking
     90                     stack.close()
     91                 passwd = fallback_getpass(prompt, stream)
     92 
     93         stream.write('\n')
     94         return passwd
     95 
     96 
     97 def win_getpass(prompt='Password: ', stream=None):
     98     """Prompt for password with echo off, using Windows getch()."""
     99     if sys.stdin is not sys.__stdin__:
    100         return fallback_getpass(prompt, stream)
    101 
    102     for c in prompt:
    103         msvcrt.putwch(c)
    104     pw = ""
    105     while 1:
    106         c = msvcrt.getwch()
    107         if c == '\r' or c == '\n':
    108             break
    109         if c == '\003':
    110             raise KeyboardInterrupt
    111         if c == '\b':
    112             pw = pw[:-1]
    113         else:
    114             pw = pw + c
    115     msvcrt.putwch('\r')
    116     msvcrt.putwch('\n')
    117     return pw
    118 
    119 
    120 def fallback_getpass(prompt='Password: ', stream=None):
    121     warnings.warn("Can not control echo on the terminal.", GetPassWarning,
    122                   stacklevel=2)
    123     if not stream:
    124         stream = sys.stderr
    125     print("Warning: Password input may be echoed.", file=stream)
    126     return _raw_input(prompt, stream)
    127 
    128 
    129 def _raw_input(prompt="", stream=None, input=None):
    130     # This doesn't save the string in the GNU readline history.
    131     if not stream:
    132         stream = sys.stderr
    133     if not input:
    134         input = sys.stdin
    135     prompt = str(prompt)
    136     if prompt:
    137         try:
    138             stream.write(prompt)
    139         except UnicodeEncodeError:
    140             # Use replace error handler to get as much as possible printed.
    141             prompt = prompt.encode(stream.encoding, 'replace')
    142             prompt = prompt.decode(stream.encoding)
    143             stream.write(prompt)
    144         stream.flush()
    145     # NOTE: The Python C API calls flockfile() (and unlock) during readline.
    146     line = input.readline()
    147     if not line:
    148         raise EOFError
    149     if line[-1] == '\n':
    150         line = line[:-1]
    151     return line
    152 
    153 
    154 def getuser():
    155     """Get the username from the environment or password database.
    156 
    157     First try various environment variables, then the password
    158     database.  This works on Windows as long as USERNAME is set.
    159 
    160     """
    161 
    162     for name in ('LOGNAME', 'USER', 'LNAME', 'USERNAME'):
    163         user = os.environ.get(name)
    164         if user:
    165             return user
    166 
    167     # If this fails, the exception will "explain" why
    168     import pwd
    169     return pwd.getpwuid(os.getuid())[0]
    170 
    171 # Bind the name getpass to the appropriate function
    172 try:
    173     import termios
    174     # it's possible there is an incompatible termios from the
    175     # McMillan Installer, make sure we have a UNIX-compatible termios
    176     termios.tcgetattr, termios.tcsetattr
    177 except (ImportError, AttributeError):
    178     try:
    179         import msvcrt
    180     except ImportError:
    181         getpass = fallback_getpass
    182     else:
    183         getpass = win_getpass
    184 else:
    185     getpass = unix_getpass
    186