lib/getpass.c

   1 /* Copyright (C) 1992-2001, 2003 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program 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
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #if _LIBC
  23 # define HAVE_STDIO_EXT_H 1
  24 #endif
  25
  26 #include <stdbool.h>
  27
  28 #include <stdio.h>
  29 #if HAVE_STDIO_EXT_H
  30 # include <stdio_ext.h>
  31 #else
  32 # define __fsetlocking(stream, type) /* empty */
  33 #endif
  34 #if !_LIBC
  35 # include "getline.h"
  36 #endif
  37
  38 #include <termios.h>
  39 #include <unistd.h>
  40
  41 #if _LIBC
  42 # include <wchar.h>
  43 #endif
  44
  45 #if _LIBC
  46 # define NOTCANCEL_MODE "c"
  47 #else
  48 # define NOTCANCEL_MODE
  49 #endif
  50
  51 #if _LIBC
  52 # define flockfile(s) _IO_flockfile (s)
  53 # define funlockfile(s) _IO_funlockfile (s)
  54 #else
  55 # include "unlocked-io.h"
  56 #endif
  57
  58 #if _LIBC
  59 # include <bits/libc-lock.h>
  60 #else
  61 # define __libc_cleanup_push(function, arg) /* empty */
  62 # define __libc_cleanup_pop(execute) /* empty */
  63 #endif
  64
  65 #if !_LIBC
  66 # define __getline getline
  67 # define __tcgetattr tcgetattr
  68 #endif
  69
  70 /* It is desirable to use this bit on systems that have it.
  71    The only bit of terminal state we want to twiddle is echoing, which is
  72    done in software; there is no need to change the state of the terminal
  73    hardware.  */
  74
  75 #ifndef TCSASOFT
  76 # define TCSASOFT 0
  77 #endif
  78
  79 static void
  80 call_fclose (void *arg)
  81 {
  82   if (arg != NULL)
  83     fclose (arg);
  84 }
  85
  86 char *
  87 getpass (const char *prompt)
  88 {
  89   FILE *tty;
  90   FILE *in, *out;
  91   struct termios s, t;
  92   bool tty_changed;
  93   static char *buf;
  94   static size_t bufsize;
  95   ssize_t nread;
  96
  97   /* Try to write to and read from the terminal if we can.
  98      If we can't open the terminal, use stderr and stdin.  */
  99
 100   tty = fopen ("/dev/tty", "w+" NOTCANCEL_MODE);
 101   if (tty == NULL)
 102     {
 103       in = stdin;
 104       out = stderr;
 105     }
 106   else
 107     {
 108       /* We do the locking ourselves.  */
 109       __fsetlocking (tty, FSETLOCKING_BYCALLER);
 110
 111       out = in = tty;
 112     }
 113
 114   /* Make sure the stream we opened is closed even if the thread is
 115      canceled.  */
 116   __libc_cleanup_push (call_fclose, tty);
 117
 118   flockfile (out);
 119
 120   /* Turn echoing off if it is on now.  */
 121
 122   if (__tcgetattr (fileno (in), &t) == 0)
 123     {
 124       /* Save the old one. */
 125       s = t;
 126       /* Tricky, tricky. */
 127       t.c_lflag &= ~(ECHO|ISIG);
 128       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &t) == 0);
 129     }
 130   else
 131     tty_changed = false;
 132
 133   /* Write the prompt.  */
 134 #ifdef USE_IN_LIBIO
 135   if (_IO_fwide (out, 0) > 0)
 136     __fwprintf (out, L"%s", prompt);
 137   else
 138 #endif
 139     fputs_unlocked (prompt, out);
 140   fflush_unlocked (out);
 141
 142   /* Read the password.  */
 143   nread = __getline (&buf, &bufsize, in);
 144
 145 #if !_LIBC
 146   /* As far as is known, glibc doesn't need this no-op fseek.  */
 147
 148   /* According to the C standard, input may not be followed by output
 149      on the same stream without an intervening call to a file
 150      positioning function.  Suppose in == out; then without this fseek
 151      call, on Solaris, HP-UX, AIX, OSF/1, the previous input gets
 152      echoed, whereas on IRIX, the following newline is not output as
 153      it should be.  POSIX imposes similar restrictions if fileno (in)
 154      == fileno (out).  The POSIX restrictions are tricky and change
 155      from POSIX version to POSIX version, so play it safe and invoke
 156      fseek even if in != out.  */
 157   fseek (out, 0, SEEK_CUR);
 158 #endif
 159
 160   if (buf != NULL)
 161     {
 162       if (nread < 0)
 163         buf[0] = '\0';
 164       else if (buf[nread - 1] == '\n')
 165         {
 166           /* Remove the newline.  */
 167           buf[nread - 1] = '\0';
 168           if (tty_changed)
 169             {
 170               /* Write the newline that was not echoed.  */
 171 #ifdef USE_IN_LIBIO
 172               if (_IO_fwide (out, 0) > 0)
 173                 putwc_unlocked (L'\n', out);
 174               else
 175 #endif
 176                 putc_unlocked ('\n', out);
 177             }
 178         }
 179     }
 180
 181   /* Restore the original setting.  */
 182   if (tty_changed)
 183     (void) tcsetattr (fileno (in), TCSAFLUSH|TCSASOFT, &s);
 184
 185   funlockfile (out);
 186
 187   __libc_cleanup_pop (0);
 188
 189   call_fclose (tty);
 190
 191   return buf;
 192 }