lib/getpass.c

   1 /* Copyright (C) 1992-2001, 2003-2007, 2009-2018 Free Software Foundation, Inc.
   2
   3    This file is part of the GNU C Library.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License along
  16    with this program; if not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _LIBC
  19 # include <config.h>
  20 #endif
  21
  22 #include "getpass.h"
  23
  24 #include <stdio.h>
  25
  26 #if !(defined _WIN32 && !defined __CYGWIN__)
  27
  28 # include <stdbool.h>
  29
  30 # if HAVE_DECL___FSETLOCKING && HAVE___FSETLOCKING
  31 #  if HAVE_STDIO_EXT_H
  32 #   include <stdio_ext.h>
  33 #  endif
  34 # else
  35 #  define __fsetlocking(stream, type)    /* empty */
  36 # endif
  37
  38 # if HAVE_TERMIOS_H
  39 #  include <termios.h>
  40 # endif
  41
  42 # if USE_UNLOCKED_IO
  43 #  include "unlocked-io.h"
  44 # else
  45 #  if !HAVE_DECL_FFLUSH_UNLOCKED
  46 #   undef fflush_unlocked
  47 #   define fflush_unlocked(x) fflush (x)
  48 #  endif
  49 #  if !HAVE_DECL_FLOCKFILE
  50 #   undef flockfile
  51 #   define flockfile(x) ((void) 0)
  52 #  endif
  53 #  if !HAVE_DECL_FUNLOCKFILE
  54 #   undef funlockfile
  55 #   define funlockfile(x) ((void) 0)
  56 #  endif
  57 #  if !HAVE_DECL_FPUTS_UNLOCKED
  58 #   undef fputs_unlocked
  59 #   define fputs_unlocked(str,stream) fputs (str, stream)
  60 #  endif
  61 #  if !HAVE_DECL_PUTC_UNLOCKED
  62 #   undef putc_unlocked
  63 #   define putc_unlocked(c,stream) putc (c, stream)
  64 #  endif
  65 # endif
  66
  67 /* It is desirable to use this bit on systems that have it.
  68    The only bit of terminal state we want to twiddle is echoing, which is
  69    done in software; there is no need to change the state of the terminal
  70    hardware.  */
  71
  72 # ifndef TCSASOFT
  73 #  define TCSASOFT 0
  74 # endif
  75
  76 static void
  77 call_fclose (void *arg)
  78 {
  79   if (arg != NULL)
  80     fclose (arg);
  81 }
  82
  83 char *
  84 getpass (const char *prompt)
  85 {
  86   FILE *tty;
  87   FILE *in, *out;
  88 # if HAVE_TCGETATTR
  89   struct termios s, t;
  90 # endif
  91   bool tty_changed = false;
  92   static char *buf;
  93   static size_t bufsize;
  94   ssize_t nread;
  95
  96   /* Try to write to and read from the terminal if we can.
  97      If we can't open the terminal, use stderr and stdin.  */
  98
  99   tty = fopen ("/dev/tty", "w+");
 100   if (tty == NULL)
 101     {
 102       in = stdin;
 103       out = stderr;
 104     }
 105   else
 106     {
 107       /* We do the locking ourselves.  */
 108       __fsetlocking (tty, FSETLOCKING_BYCALLER);
 109
 110       out = in = tty;
 111     }
 112
 113   flockfile (out);
 114
 115   /* Turn echoing off if it is on now.  */
 116 # if HAVE_TCGETATTR
 117   if (tcgetattr (fileno (in), &t) == 0)
 118     {
 119       /* Save the old one. */
 120       s = t;
 121       /* Tricky, tricky. */
 122       t.c_lflag &= ~(ECHO | ISIG);
 123       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH | TCSASOFT, &t) == 0);
 124     }
 125 # endif
 126
 127   /* Write the prompt.  */
 128   fputs_unlocked (prompt, out);
 129   fflush_unlocked (out);
 130
 131   /* Read the password.  */
 132   nread = getline (&buf, &bufsize, in);
 133
 134   /* According to the C standard, input may not be followed by output
 135      on the same stream without an intervening call to a file
 136      positioning function.  Suppose in == out; then without this fseek
 137      call, on Solaris, HP-UX, AIX, OSF/1, the previous input gets
 138      echoed, whereas on IRIX, the following newline is not output as
 139      it should be.  POSIX imposes similar restrictions if fileno (in)
 140      == fileno (out).  The POSIX restrictions are tricky and change
 141      from POSIX version to POSIX version, so play it safe and invoke
 142      fseek even if in != out.  */
 143   fseeko (out, 0, SEEK_CUR);
 144
 145   if (buf != NULL)
 146     {
 147       if (nread < 0)
 148         buf[0] = '\0';
 149       else if (buf[nread - 1] == '\n')
 150         {
 151           /* Remove the newline.  */
 152           buf[nread - 1] = '\0';
 153           if (tty_changed)
 154             {
 155               /* Write the newline that was not echoed.  */
 156               putc_unlocked ('\n', out);
 157             }
 158         }
 159     }
 160
 161   /* Restore the original setting.  */
 162 # if HAVE_TCSETATTR
 163   if (tty_changed)
 164     tcsetattr (fileno (in), TCSAFLUSH | TCSASOFT, &s);
 165 # endif
 166
 167   funlockfile (out);
 168
 169   call_fclose (tty);
 170
 171   return buf;
 172 }
 173
 174 #else /* W32 native */
 175
 176 /* Windows implementation by Martin Lambers <marlam@marlam.de>,
 177    improved by Simon Josefsson. */
 178
 179 /* For PASS_MAX. */
 180 # include <limits.h>
 181 /* For _getch(). */
 182 # include <conio.h>
 183 /* For strdup(). */
 184 # include <string.h>
 185
 186 # ifndef PASS_MAX
 187 #  define PASS_MAX 512
 188 # endif
 189
 190 char *
 191 getpass (const char *prompt)
 192 {
 193   char getpassbuf[PASS_MAX + 1];
 194   size_t i = 0;
 195   int c;
 196
 197   if (prompt)
 198     {
 199       fputs (prompt, stderr);
 200       fflush (stderr);
 201     }
 202
 203   for (;;)
 204     {
 205       c = _getch ();
 206       if (c == '\r')
 207         {
 208           getpassbuf[i] = '\0';
 209           break;
 210         }
 211       else if (i < PASS_MAX)
 212         {
 213           getpassbuf[i++] = c;
 214         }
 215
 216       if (i >= PASS_MAX)
 217         {
 218           getpassbuf[i] = '\0';
 219           break;
 220         }
 221     }
 222
 223   if (prompt)
 224     {
 225       fputs ("\r\n", stderr);
 226       fflush (stderr);
 227     }
 228
 229   return strdup (getpassbuf);
 230 }
 231 #endif