misc/getpass.c

   1 /* Copyright (C) 1992, 1993, 1994, 1995 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <stdio.h>
  20 #include <termios.h>
  21 #include <unistd.h>
  22
  23 /* It is desireable to use this bit on systems that have it.
  24    The only bit of terminal state we want to twiddle is echoing, which is
  25    done in software; there is no need to change the state of the terminal
  26    hardware.  */
  27
  28 #ifndef TCSASOFT
  29 #define TCSASOFT 0
  30 #endif
  31
  32 char *
  33 getpass (prompt)
  34      const char *prompt;
  35 {
  36   FILE *in, *out;
  37   struct termios t;
  38   int echo_off;
  39   static char *buf = NULL;
  40   static size_t bufsize = 0;
  41   ssize_t nread;
  42
  43   /* Try to write to and read from the terminal if we can.
  44      If we can't open the terminal, use stderr and stdin.  */
  45
  46   in = fopen ("/dev/tty", "w+");
  47   if (in == NULL)
  48     {
  49       in = stdin;
  50       out = stderr;
  51     }
  52   else
  53     out = in;
  54
  55   /* Turn echoing off if it is on now.  */
  56
  57   if (tcgetattr (fileno (in), &t) == 0)
  58     {
  59       if (t.c_lflag & ECHO)
  60         {
  61           t.c_lflag &= ~ECHO;
  62           echo_off = tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0;
  63           t.c_lflag |= ECHO;
  64         }
  65       else
  66         echo_off = 0;
  67     }
  68   else
  69     echo_off = 0;
  70
  71   /* Write the prompt.  */
  72   fputs (prompt, out);
  73   fflush (out);
  74
  75   /* Read the password.  */
  76   nread = __getline (&buf, &bufsize, in);
  77   if (buf != NULL)
  78     if (nread < 0)
  79       buf[0] = '\0';
  80     else if (buf[nread - 1] == '\n')
  81       {
  82         /* Remove the newline.  */
  83         buf[nread - 1] = '\0';
  84         if (echo_off)
  85           /* Write the newline that was not echoed.  */
  86           putc ('\n', out);
  87       }
  88
  89   /* Restore echoing.  */
  90   if (echo_off)
  91     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t);
  92
  93   if (in != stdin)
  94     /* We opened the terminal; now close it.  */
  95     fclose (in);
  96
  97   return buf;
  98 }