misc/getpass.c

   1 /* Copyright (C) 1992,93,94,95,96,97,98,99 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 #ifdef USE_IN_LIBIO
  24 # define flockfile(s) _IO_flockfile (s)
  25 # define funlockfile(s) _IO_funlockfile (s)
  26 #endif
  27
  28 /* It is desirable to use this bit on systems that have it.
  29    The only bit of terminal state we want to twiddle is echoing, which is
  30    done in software; there is no need to change the state of the terminal
  31    hardware.  */
  32
  33 #ifndef TCSASOFT
  34 #define TCSASOFT 0
  35 #endif
  36
  37 char *
  38 getpass (prompt)
  39      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   flockfile (out);
  61
  62   /* Turn echoing off if it is on now.  */
  63
  64   if (__tcgetattr (fileno (in), &t) == 0)
  65     {
  66       /* Save the old one. */
  67       s = t;
  68       /* Tricky, tricky. */
  69       t.c_lflag &= ~(ECHO|ISIG);
  70       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  71     }
  72   else
  73     tty_changed = 0;
  74
  75   /* Write the prompt.  */
  76   fputs_unlocked (prompt, out);
  77   fflush_unlocked (out);
  78
  79   /* Read the password.  */
  80   nread = __getline (&buf, &bufsize, in);
  81   if (buf != NULL)
  82     {
  83       if (nread < 0)
  84         buf[0] = '\0';
  85       else if (buf[nread - 1] == '\n')
  86         {
  87           /* Remove the newline.  */
  88           buf[nread - 1] = '\0';
  89           if (tty_changed)
  90             /* Write the newline that was not echoed.  */
  91             putc_unlocked ('\n', out);
  92         }
  93     }
  94
  95   /* Restore the original setting.  */
  96   if (tty_changed)
  97     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
  98
  99   funlockfile (out);
 100
 101   if (in != stdin)
 102     /* We opened the terminal; now close it.  */
 103     fclose (in);
 104
 105   return buf;
 106 }