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 # include <wchar.h>
  26 # define flockfile(s) _IO_flockfile (s)
  27 # define funlockfile(s) _IO_funlockfile (s)
  28 #endif
  29
  30 /* It is desirable to use this bit on systems that have it.
  31    The only bit of terminal state we want to twiddle is echoing, which is
  32    done in software; there is no need to change the state of the terminal
  33    hardware.  */
  34
  35 #ifndef TCSASOFT
  36 #define TCSASOFT 0
  37 #endif
  38
  39 char *
  40 getpass (prompt)
  41      const char *prompt;
  42 {
  43   FILE *in, *out;
  44   struct termios s, t;
  45   int tty_changed;
  46   static char *buf;
  47   static size_t bufsize;
  48   ssize_t nread;
  49
  50   /* Try to write to and read from the terminal if we can.
  51      If we can't open the terminal, use stderr and stdin.  */
  52
  53   in = fopen ("/dev/tty", "w+");
  54   if (in == NULL)
  55     {
  56       in = stdin;
  57       out = stderr;
  58     }
  59   else
  60     {
  61       /* We do the locking ourselves.  */
  62       __fsetlocking (in, FSETLOCKING_BYCALLER);
  63
  64       out = in;
  65     }
  66
  67   flockfile (out);
  68
  69   /* Turn echoing off if it is on now.  */
  70
  71   if (__tcgetattr (fileno (in), &t) == 0)
  72     {
  73       /* Save the old one. */
  74       s = t;
  75       /* Tricky, tricky. */
  76       t.c_lflag &= ~(ECHO|ISIG);
  77       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  78     }
  79   else
  80     tty_changed = 0;
  81
  82   /* Write the prompt.  */
  83 #ifdef USE_IN_LIBIO
  84   if (_IO_fwide (out, 0) > 0)
  85     __fwprintf (out, L"%s", prompt);
  86   else
  87 #endif
  88     fputs_unlocked (prompt, out);
  89   fflush_unlocked (out);
  90
  91   /* Read the password.  */
  92   nread = __getline (&buf, &bufsize, in);
  93   if (buf != NULL)
  94     {
  95       if (nread < 0)
  96         buf[0] = '\0';
  97       else if (buf[nread - 1] == '\n')
  98         {
  99           /* Remove the newline.  */
 100           buf[nread - 1] = '\0';
 101           if (tty_changed)
 102             {
 103               /* Write the newline that was not echoed.  */
 104 #ifdef USE_IN_LIBIO
 105               if (_IO_fwide (out, 0) > 0)
 106                 putwc_unlocked (L'\n', out);
 107               else
 108 #endif
 109                 putc_unlocked ('\n', out);
 110             }
 111         }
 112     }
 113
 114   /* Restore the original setting.  */
 115   if (tty_changed)
 116     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
 117
 118   funlockfile (out);
 119
 120   if (in != stdin)
 121     /* We opened the terminal; now close it.  */
 122     fclose (in);
 123
 124   return buf;
 125 }