misc/getpass.c

   1 /* Copyright (C) 1992, 93, 94, 95, 96, 97 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 #include <stdio.h>
  20 #include <termios.h>
  21 #include <unistd.h>
  22
  23 /* It is desirable 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 s, t;
  38   int tty_changed;
  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       /* Save the old one. */
  60       s = t;
  61       /* Tricky, tricky. */
  62       t.c_lflag &= ~(ECHO|ISIG);
  63       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  64     }
  65   else
  66     tty_changed = 0;
  67
  68   /* Write the prompt.  */
  69   fputs (prompt, out);
  70   fflush (out);
  71
  72   /* Read the password.  */
  73   nread = __getline (&buf, &bufsize, in);
  74   if (buf != NULL)
  75     if (nread < 0)
  76       buf[0] = '\0';
  77     else if (buf[nread - 1] == '\n')
  78       {
  79         /* Remove the newline.  */
  80         buf[nread - 1] = '\0';
  81         if (tty_changed)
  82           /* Write the newline that was not echoed.  */
  83           putc ('\n', out);
  84       }
  85
  86   /* Restore the original setting.  */
  87   if (tty_changed)
  88     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
  89
  90   if (in != stdin)
  91     /* We opened the terminal; now close it.  */
  92     fclose (in);
  93
  94   return buf;
  95 }