misc/getpass.c

   1 /* Copyright (C) 1992-1999,2001,2003-2005,2011 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 <string.h>             /* For string function builtin redirect.  */
  22 #include <termios.h>
  23 #include <unistd.h>
  24
  25 #include <wchar.h>
  26 #define flockfile(s) _IO_flockfile (s)
  27 #define funlockfile(s) _IO_funlockfile (s)
  28 #include <bits/libc-lock.h>
  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 static void
  40 call_fclose (void *arg)
  41 {
  42   if (arg != NULL)
  43     fclose (arg);
  44 }
  45
  46 char *
  47 getpass (prompt)
  48      const char *prompt;
  49 {
  50   FILE *in, *out;
  51   struct termios s, t;
  52   int tty_changed;
  53   static char *buf;
  54   static size_t bufsize;
  55   ssize_t nread;
  56
  57   /* Try to write to and read from the terminal if we can.
  58      If we can't open the terminal, use stderr and stdin.  */
  59
  60   in = fopen ("/dev/tty", "w+ce");
  61   if (in == NULL)
  62     {
  63       in = stdin;
  64       out = stderr;
  65     }
  66   else
  67     {
  68       /* We do the locking ourselves.  */
  69       __fsetlocking (in, FSETLOCKING_BYCALLER);
  70
  71       out = in;
  72     }
  73
  74   /* Make sure the stream we opened is closed even if the thread is
  75      canceled.  */
  76   __libc_cleanup_push (call_fclose, in == out ? in : NULL);
  77
  78   flockfile (out);
  79
  80   /* Turn echoing off if it is on now.  */
  81
  82   if (__tcgetattr (fileno (in), &t) == 0)
  83     {
  84       /* Save the old one. */
  85       s = t;
  86       /* Tricky, tricky. */
  87       t.c_lflag &= ~(ECHO|ISIG);
  88       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  89     }
  90   else
  91     tty_changed = 0;
  92
  93   /* Write the prompt.  */
  94   __fxprintf (out, "%s", prompt);
  95   fflush_unlocked (out);
  96
  97   /* Read the password.  */
  98   nread = __getline (&buf, &bufsize, in);
  99   if (buf != NULL)
 100     {
 101       if (nread < 0)
 102         buf[0] = '\0';
 103       else if (buf[nread - 1] == '\n')
 104         {
 105           /* Remove the newline.  */
 106           buf[nread - 1] = '\0';
 107           if (tty_changed)
 108             /* Write the newline that was not echoed.  */
 109             __fxprintf (out, "\n");
 110         }
 111     }
 112
 113   /* Restore the original setting.  */
 114   if (tty_changed)
 115     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
 116
 117   funlockfile (out);
 118
 119   __libc_cleanup_pop (0);
 120
 121   if (in != stdin)
 122     /* We opened the terminal; now close it.  */
 123     fclose (in);
 124
 125   return buf;
 126 }