misc/getpass.c

   1 /* Copyright (C) 1992,93,94,95,96,97,98,99,2001 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 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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <stdio.h>
  20 #include <stdio_ext.h>
  21 #include <termios.h>
  22 #include <unistd.h>
  23
  24 #ifdef USE_IN_LIBIO
  25 # define flockfile(s) _IO_flockfile (s)
  26 # define funlockfile(s) _IO_funlockfile (s)
  27 #endif
  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 (prompt)
  40      const char *prompt;
  41 {
  42   FILE *in, *out;
  43   struct termios s, t;
  44   int tty_changed;
  45   static char *buf;
  46   static size_t bufsize;
  47   ssize_t nread;
  48
  49   /* Try to write to and read from the terminal if we can.
  50      If we can't open the terminal, use stderr and stdin.  */
  51
  52   in = fopen ("/dev/tty", "w+");
  53   if (in == NULL)
  54     {
  55       in = stdin;
  56       out = stderr;
  57     }
  58   else
  59     {
  60       /* We do the locking ourselves.  */
  61       __fsetlocking (in, FSETLOCKING_BYCALLER);
  62
  63       out = in;
  64     }
  65
  66   flockfile (out);
  67
  68   /* Turn echoing off if it is on now.  */
  69
  70   if (__tcgetattr (fileno (in), &t) == 0)
  71     {
  72       /* Save the old one. */
  73       s = t;
  74       /* Tricky, tricky. */
  75       t.c_lflag &= ~(ECHO|ISIG);
  76       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  77     }
  78   else
  79     tty_changed = 0;
  80
  81   /* Write the prompt.  */
  82   fputs_unlocked (prompt, out);
  83   fflush_unlocked (out);
  84
  85   /* Read the password.  */
  86   nread = __getline (&buf, &bufsize, in);
  87   if (buf != NULL)
  88     {
  89       if (nread < 0)
  90         buf[0] = '\0';
  91       else if (buf[nread - 1] == '\n')
  92         {
  93           /* Remove the newline.  */
  94           buf[nread - 1] = '\0';
  95           if (tty_changed)
  96             /* Write the newline that was not echoed.  */
  97             putc_unlocked ('\n', out);
  98         }
  99     }
 100
 101   /* Restore the original setting.  */
 102   if (tty_changed)
 103     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
 104
 105   funlockfile (out);
 106
 107   if (in != stdin)
 108     /* We opened the terminal; now close it.  */
 109     fclose (in);
 110
 111   return buf;
 112 }