lib/getpass.c

   1 /* Copyright (C) 1992,93,94,95,96,97,98,99,2000, 2001 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 not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #if HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 #include <stdio.h>
  24 #include <termios.h>
  25 #include <unistd.h>
  26 #include "getline.h"
  27 #include "unlocked-io.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 char *
  39 getpass (const char *prompt)
  40 {
  41   FILE *in, *out;
  42   struct termios s, t;
  43   int tty_changed;
  44   static char *buf;
  45   static size_t bufsize;
  46   ssize_t nread;
  47
  48   /* Try to write to and read from the terminal if we can.
  49      If we can't open the terminal, use stderr and stdin.  */
  50
  51   in = fopen ("/dev/tty", "w+");
  52   if (in == NULL)
  53     {
  54       in = stdin;
  55       out = stderr;
  56     }
  57   else
  58     out = in;
  59
  60   /* Turn echoing off if it is on now.  */
  61
  62   if (tcgetattr (fileno (in), &t) == 0)
  63     {
  64       /* Save the old one. */
  65       s = t;
  66       /* Tricky, tricky. */
  67       t.c_lflag &= ~(ECHO|ISIG);
  68       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  69     }
  70   else
  71     tty_changed = 0;
  72
  73   /* Write the prompt.  */
  74   fputs (prompt, out);
  75   fflush (out);
  76
  77   /* Read the password.  */
  78   nread = getline (&buf, &bufsize, in);
  79   if (buf != NULL)
  80     {
  81       if (nread < 0)
  82         buf[0] = '\0';
  83       else if (buf[nread - 1] == '\n')
  84         {
  85           /* Remove the newline.  */
  86           buf[nread - 1] = '\0';
  87           if (tty_changed)
  88             /* Write the newline that was not echoed.  */
  89             putc ('\n', out);
  90         }
  91     }
  92
  93   /* Restore the original setting.  */
  94   if (tty_changed)
  95     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
  96
  97   if (in != stdin)
  98     /* We opened the terminal; now close it.  */
  99     fclose (in);
 100
 101   return buf;
 102 }