lib/getpass.c

   1 /* Copyright (C) 1992-2001, 2003-2007, 2009-2025 Free Software Foundation, Inc.
   2
   3    This file is part of the GNU C Library.
   4
   5    This file is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    This file 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 Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along 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 # if HAVE_DECL___FSETLOCKING && HAVE___FSETLOCKING
  32 #  if HAVE_STDIO_EXT_H
  33 #   include <stdio_ext.h>
  34 #  endif
  35 # else
  36 #  define __fsetlocking(stream, type)    /* empty */
  37 # endif
  38
  39 # if HAVE_TERMIOS_H
  40 #  include <termios.h>
  41 # endif
  42
  43 # if USE_UNLOCKED_IO
  44 #  include "unlocked-io.h"
  45 # else
  46 #  if !HAVE_DECL_FFLUSH_UNLOCKED
  47 #   undef fflush_unlocked
  48 #   define fflush_unlocked(x) fflush (x)
  49 #  endif
  50 #  if !HAVE_DECL_FLOCKFILE
  51 #   undef flockfile
  52 #   define flockfile(x) ((void) 0)
  53 #  endif
  54 #  if !HAVE_DECL_FUNLOCKFILE
  55 #   undef funlockfile
  56 #   define funlockfile(x) ((void) 0)
  57 #  endif
  58 #  if !HAVE_DECL_FPUTS_UNLOCKED
  59 #   undef fputs_unlocked
  60 #   define fputs_unlocked(str,stream) fputs (str, stream)
  61 #  endif
  62 #  if !HAVE_DECL_PUTC_UNLOCKED
  63 #   undef putc_unlocked
  64 #   define putc_unlocked(c,stream) putc (c, stream)
  65 #  endif
  66 # endif
  67
  68 /* It is desirable to use this bit on systems that have it.
  69    The only bit of terminal state we want to twiddle is echoing, which is
  70    done in software; there is no need to change the state of the terminal
  71    hardware.  */
  72
  73 # ifndef TCSASOFT
  74 #  define TCSASOFT 0
  75 # endif
  76
  77 static void
  78 call_fclose (void *arg)
  79 {
  80   if (arg != NULL)
  81     fclose (arg);
  82 }
  83
  84 char *
  85 getpass (const char *prompt)
  86 {
  87   FILE *tty;
  88   FILE *in, *out;
  89 # if HAVE_TCGETATTR
  90   struct termios s, t;
  91 # endif
  92   bool tty_changed = false;
  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+e");
 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   flockfile (out);
 115
 116   /* Turn echoing off if it is on now.  */
 117 # if HAVE_TCGETATTR
 118   if (tcgetattr (fileno (in), &t) == 0)
 119     {
 120       /* Save the old one. */
 121       s = t;
 122       /* Tricky, tricky. */
 123       t.c_lflag &= ~(ECHO | ISIG);
 124       tty_changed = (tcsetattr (fileno (in), TCSAFLUSH | TCSASOFT, &t) == 0);
 125     }
 126 # endif
 127
 128   if (prompt)
 129     {
 130       /* Write the prompt.  */
 131       fputs_unlocked (prompt, out);
 132       fflush_unlocked (out);
 133     }
 134
 135   /* Read the password.  */
 136   nread = getline (&buf, &bufsize, in);
 137
 138   /* According to the C standard, input may not be followed by output
 139      on the same stream without an intervening call to a file
 140      positioning function.  Suppose in == out; then without this fseek
 141      call, on Solaris, HP-UX, AIX, OSF/1, the previous input gets
 142      echoed, whereas on IRIX, the following newline is not output as
 143      it should be.  POSIX imposes similar restrictions if fileno (in)
 144      == fileno (out).  The POSIX restrictions are tricky and change
 145      from POSIX version to POSIX version, so play it safe and invoke
 146      fseek even if in != out.  */
 147   fseeko (out, 0, SEEK_CUR);
 148
 149   if (buf != NULL)
 150     {
 151       if (nread < 0)
 152         buf[0] = '\0';
 153       else if (buf[nread - 1] == '\n')
 154         {
 155           /* Remove the newline.  */
 156           buf[nread - 1] = '\0';
 157           if (tty_changed)
 158             {
 159               /* Write the newline that was not echoed.  */
 160               putc_unlocked ('\n', out);
 161             }
 162         }
 163     }
 164
 165   /* Restore the original setting.  */
 166 # if HAVE_TCSETATTR
 167   if (tty_changed)
 168     tcsetattr (fileno (in), TCSAFLUSH | TCSASOFT, &s);
 169 # endif
 170
 171   funlockfile (out);
 172
 173   call_fclose (tty);
 174
 175   return buf;
 176 }
 177
 178 #else /* W32 native */
 179
 180 /* Windows implementation by Martin Lambers <marlam@marlam.de>,
 181    improved by Simon Josefsson. */
 182
 183 /* For PASS_MAX. */
 184 # include <limits.h>
 185 /* For _getch(). */
 186 # include <conio.h>
 187 /* For strdup(). */
 188 # include <string.h>
 189
 190 # ifndef PASS_MAX
 191 #  define PASS_MAX 512
 192 # endif
 193
 194 char *
 195 getpass (const char *prompt)
 196 {
 197   char getpassbuf[PASS_MAX + 1];
 198   size_t i = 0;
 199   int c;
 200
 201   if (prompt)
 202     {
 203       fputs (prompt, stderr);
 204       fflush (stderr);
 205     }
 206
 207   for (;;)
 208     {
 209       c = _getch ();
 210       if (c == '\r')
 211         {
 212           getpassbuf[i] = '\0';
 213           break;
 214         }
 215       else if (i < PASS_MAX)
 216         {
 217           getpassbuf[i++] = c;
 218         }
 219
 220       if (i >= PASS_MAX)
 221         {
 222           getpassbuf[i] = '\0';
 223           break;
 224         }
 225     }
 226
 227   if (prompt)
 228     {
 229       fputs ("\r\n", stderr);
 230       fflush (stderr);
 231     }
 232
 233   return strdup (getpassbuf);
 234 }
 235 #endif