misc/getpass.c

   1 /* Copyright (C) 1992-2015 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <stdio.h>
  19 #include <stdio_ext.h>
  20 #include <string.h>             /* For string function builtin redirect.  */
  21 #include <termios.h>
  22 #include <unistd.h>
  23
  24 #include <wchar.h>
  25 #define flockfile(s) _IO_flockfile (s)
  26 #define funlockfile(s) _IO_funlockfile (s)
  27 #include <bits/libc-lock.h>
  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 static void
  39 call_fclose (void *arg)
  40 {
  41   if (arg != NULL)
  42     fclose (arg);
  43 }
  44
  45 char *
  46 getpass (prompt)
  47      const char *prompt;
  48 {
  49   FILE *in, *out;
  50   struct termios s, t;
  51   int tty_changed;
  52   static char *buf;
  53   static size_t bufsize;
  54   ssize_t nread;
  55
  56   /* Try to write to and read from the terminal if we can.
  57      If we can't open the terminal, use stderr and stdin.  */
  58
  59   in = fopen ("/dev/tty", "w+ce");
  60   if (in == NULL)
  61     {
  62       in = stdin;
  63       out = stderr;
  64     }
  65   else
  66     {
  67       /* We do the locking ourselves.  */
  68       __fsetlocking (in, FSETLOCKING_BYCALLER);
  69
  70       out = in;
  71     }
  72
  73   /* Make sure the stream we opened is closed even if the thread is
  74      canceled.  */
  75   __libc_cleanup_push (call_fclose, in == out ? in : NULL);
  76
  77   flockfile (out);
  78
  79   /* Turn echoing off if it is on now.  */
  80
  81   if (__tcgetattr (fileno (in), &t) == 0)
  82     {
  83       /* Save the old one. */
  84       s = t;
  85       /* Tricky, tricky. */
  86       t.c_lflag &= ~(ECHO|ISIG);
  87       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
  88     }
  89   else
  90     tty_changed = 0;
  91
  92   /* Write the prompt.  */
  93   __fxprintf (out, "%s", prompt);
  94   fflush_unlocked (out);
  95
  96   /* Read the password.  */
  97   nread = __getline (&buf, &bufsize, in);
  98   if (buf != NULL)
  99     {
 100       if (nread < 0)
 101         buf[0] = '\0';
 102       else if (buf[nread - 1] == '\n')
 103         {
 104           /* Remove the newline.  */
 105           buf[nread - 1] = '\0';
 106           if (tty_changed)
 107             /* Write the newline that was not echoed.  */
 108             __fxprintf (out, "\n");
 109         }
 110     }
 111
 112   /* Restore the original setting.  */
 113   if (tty_changed)
 114     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
 115
 116   funlockfile (out);
 117
 118   __libc_cleanup_pop (0);
 119
 120   if (in != stdin)
 121     /* We opened the terminal; now close it.  */
 122     fclose (in);
 123
 124   return buf;
 125 }