lib/getpass.c

   1 /* Copyright (C) 1992-2001, 2003-2007, 2009-2020 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 /* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
  20    warns for the null checks on 'prompt' below.  */
  21 # define _GL_ARG_NONNULL(params)
  22 # include <config.h>
  23 #endif
  24
  25 #include "getpass.h"
  26
  27 #include <stdio.h>
  28
  29 #if !(defined _WIN32 && !defined __CYGWIN__)
  30
  31 # include <stdbool.h>
  32
  33 # if HAVE_DECL___FSETLOCKING && HAVE___FSETLOCKING
  34 #  if HAVE_STDIO_EXT_H
  35 #   include <stdio_ext.h>
  36 #  endif
  37 # else
  38 #  define __fsetlocking(stream, type)    /* empty */
  39 # endif
  40
  41 # if HAVE_TERMIOS_H
  42 #  include <termios.h>
  43 # endif
  44
  45 # if USE_UNLOCKED_IO
  46 #  include "unlocked-io.h"
  47 # else
  48 #  if !HAVE_DECL_FFLUSH_UNLOCKED
  49 #   undef fflush_unlocked
  50 #   define fflush_unlocked(x) fflush (x)
  51 #  endif
  52 #  if !HAVE_DECL_FLOCKFILE
  53 #   undef flockfile
  54 #   define flockfile(x) ((void) 0)
  55 #  endif
  56 #  if !HAVE_DECL_FUNLOCKFILE
  57 #   undef funlockfile
  58 #   define funlockfile(x) ((void) 0)
  59 #  endif
  60 #  if !HAVE_DECL_FPUTS_UNLOCKED
  61 #   undef fputs_unlocked
  62 #   define fputs_unlocked(str,stream) fputs (str, stream)
  63 #  endif
  64 #  if !HAVE_DECL_PUTC_UNLOCKED
  65 #   undef putc_unlocked
  66 #   define putc_unlocked(c,stream) putc (c, stream)
  67 #  endif
  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 # if HAVE_TCGETATTR
  92   struct termios s, t;
  93 # endif
  94   bool tty_changed = false;
  95   static char *buf;
  96   static size_t bufsize;
  97   ssize_t nread;
  98
  99   /* Try to write to and read from the terminal if we can.
 100      If we can't open the terminal, use stderr and stdin.  */
 101
 102   tty = fopen ("/dev/tty", "w+e");
 103   if (tty == NULL)
 104     {
 105       in = stdin;
 106       out = stderr;
 107     }
 108   else
 109     {
 110       /* We do the locking ourselves.  */
 111       __fsetlocking (tty, FSETLOCKING_BYCALLER);
 112
 113       out = in = tty;
 114     }
 115
 116   flockfile (out);
 117
 118   /* Turn echoing off if it is on now.  */
 119 # if HAVE_TCGETATTR
 120   if (tcgetattr (fileno (in), &t) == 0)
 121     {
 122       /* Save the old one. */
 123       s = t;
 124       /* Tricky, tricky. */
 125       t.c_lflag &= ~(ECHO | ISIG);
 126       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH | TCSASOFT, &t) == 0);
 127     }
 128 # endif
 129
 130   if (prompt)
 131     {
 132       /* Write the prompt.  */
 133       fputs_unlocked (prompt, out);
 134       fflush_unlocked (out);
 135     }
 136
 137   /* Read the password.  */
 138   nread = getline (&buf, &bufsize, in);
 139
 140   /* According to the C standard, input may not be followed by output
 141      on the same stream without an intervening call to a file
 142      positioning function.  Suppose in == out; then without this fseek
 143      call, on Solaris, HP-UX, AIX, OSF/1, the previous input gets
 144      echoed, whereas on IRIX, the following newline is not output as
 145      it should be.  POSIX imposes similar restrictions if fileno (in)
 146      == fileno (out).  The POSIX restrictions are tricky and change
 147      from POSIX version to POSIX version, so play it safe and invoke
 148      fseek even if in != out.  */
 149   fseeko (out, 0, SEEK_CUR);
 150
 151   if (buf != NULL)
 152     {
 153       if (nread < 0)
 154         buf[0] = '\0';
 155       else if (buf[nread - 1] == '\n')
 156         {
 157           /* Remove the newline.  */
 158           buf[nread - 1] = '\0';
 159           if (tty_changed)
 160             {
 161               /* Write the newline that was not echoed.  */
 162               putc_unlocked ('\n', out);
 163             }
 164         }
 165     }
 166
 167   /* Restore the original setting.  */
 168 # if HAVE_TCSETATTR
 169   if (tty_changed)
 170     tcsetattr (fileno (in), TCSAFLUSH | TCSASOFT, &s);
 171 # endif
 172
 173   funlockfile (out);
 174
 175   call_fclose (tty);
 176
 177   return buf;
 178 }
 179
 180 #else /* W32 native */
 181
 182 /* Windows implementation by Martin Lambers <marlam@marlam.de>,
 183    improved by Simon Josefsson. */
 184
 185 /* For PASS_MAX. */
 186 # include <limits.h>
 187 /* For _getch(). */
 188 # include <conio.h>
 189 /* For strdup(). */
 190 # include <string.h>
 191
 192 # ifndef PASS_MAX
 193 #  define PASS_MAX 512
 194 # endif
 195
 196 char *
 197 getpass (const char *prompt)
 198 {
 199   char getpassbuf[PASS_MAX + 1];
 200   size_t i = 0;
 201   int c;
 202
 203   if (prompt)
 204     {
 205       fputs (prompt, stderr);
 206       fflush (stderr);
 207     }
 208
 209   for (;;)
 210     {
 211       c = _getch ();
 212       if (c == '\r')
 213         {
 214           getpassbuf[i] = '\0';
 215           break;
 216         }
 217       else if (i < PASS_MAX)
 218         {
 219           getpassbuf[i++] = c;
 220         }
 221
 222       if (i >= PASS_MAX)
 223         {
 224           getpassbuf[i] = '\0';
 225           break;
 226         }
 227     }
 228
 229   if (prompt)
 230     {
 231       fputs ("\r\n", stderr);
 232       fflush (stderr);
 233     }
 234
 235   return strdup (getpassbuf);
 236 }
 237 #endif