1  /* Copyright (C) 1992-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <stdio.h>
      19  #include <stdio_ext.h>
      20  #include <string.h>		/* For string function builtin redirect.  */
      21  #include <termios.h>
      22  #include <unistd.h>
      23  
      24  #include <wchar.h>
      25  #define flockfile(s) _IO_flockfile (s)
      26  #define funlockfile(s) _IO_funlockfile (s)
      27  #include <libc-lock.h>
      28  
      29  /* It is desirable to use this bit on systems that have it.
      30     The only bit of terminal state we want to twiddle is echoing, which is
      31     done in software; there is no need to change the state of the terminal
      32     hardware.  */
      33  
      34  #ifndef TCSASOFT
      35  #define TCSASOFT 0
      36  #endif
      37  
      38  static void
      39  call_fclose (void *arg)
      40  {
      41    if (arg != NULL)
      42      fclose (arg);
      43  }
      44  
      45  char *
      46  getpass (const char *prompt)
      47  {
      48    FILE *in, *out;
      49    struct termios s, t;
      50    int tty_changed;
      51    static char *buf;
      52    static size_t bufsize;
      53    ssize_t nread;
      54  
      55    /* Try to write to and read from the terminal if we can.
      56       If we can't open the terminal, use stderr and stdin.  */
      57  
      58    in = fopen ("/dev/tty", "w+ce");
      59    if (in == NULL)
      60      {
      61        in = stdin;
      62        out = stderr;
      63      }
      64    else
      65      {
      66        /* We do the locking ourselves.  */
      67        __fsetlocking (in, FSETLOCKING_BYCALLER);
      68  
      69        out = in;
      70      }
      71  
      72    /* Make sure the stream we opened is closed even if the thread is
      73       canceled.  */
      74    __libc_cleanup_push (call_fclose, in == out ? in : NULL);
      75  
      76    flockfile (out);
      77  
      78    /* Turn echoing off if it is on now.  */
      79  
      80    if (__tcgetattr (fileno (in), &t) == 0)
      81      {
      82        /* Save the old one. */
      83        s = t;
      84        /* Tricky, tricky. */
      85        t.c_lflag &= ~(ECHO|ISIG);
      86        tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
      87      }
      88    else
      89      tty_changed = 0;
      90  
      91    /* Write the prompt.  */
      92    __fxprintf (out, "%s", prompt);
      93    __fflush_unlocked (out);
      94  
      95    /* Read the password.  */
      96    nread = __getline (&buf, &bufsize, in);
      97    if (buf != NULL)
      98      {
      99        if (nread < 0)
     100  	buf[0] = '\0';
     101        else if (buf[nread - 1] == '\n')
     102  	{
     103  	  /* Remove the newline.  */
     104  	  buf[nread - 1] = '\0';
     105  	  if (tty_changed)
     106  	    /* Write the newline that was not echoed.  */
     107  	    __fxprintf (out, "\n");
     108  	}
     109      }
     110  
     111    /* Restore the original setting.  */
     112    if (tty_changed)
     113      (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
     114  
     115    funlockfile (out);
     116  
     117    __libc_cleanup_pop (0);
     118  
     119    if (in != stdin)
     120      /* We opened the terminal; now close it.  */
     121      fclose (in);
     122  
     123    return buf;
     124  }