tests/test-dup-safer.c

   1 /* Test that dup_safer leaves standard fds alone.
   2    Copyright (C) 2009-2024 Free Software Foundation, Inc.
   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 3 of the License, or
   7    (at your option) 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
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* Written by Eric Blake <ebb9@byu.net>, 2009.  */
  18
  19 #include <config.h>
  20
  21 #include "unistd--.h"
  22
  23 #include <fcntl.h>
  24 #include <errno.h>
  25 #include <stdio.h>
  26 #include <unistd.h>
  27
  28 #include "binary-io.h"
  29 #include "cloexec.h"
  30
  31 #if defined _WIN32 && ! defined __CYGWIN__
  32 /* Get declarations of the native Windows API functions.  */
  33 # define WIN32_LEAN_AND_MEAN
  34 # include <windows.h>
  35 /* Get _get_osfhandle.  */
  36 # if GNULIB_MSVC_NOTHROW
  37 #  include "msvc-nothrow.h"
  38 # else
  39 #  include <io.h>
  40 # endif
  41 #endif
  42
  43 #if !O_BINARY
  44 # define set_binary_mode my_set_binary_mode
  45 static int
  46 set_binary_mode (_GL_UNUSED int fd, _GL_UNUSED int mode)
  47 {
  48   return 0;
  49 }
  50 #endif
  51
  52 /* This test intentionally closes stderr.  So, we arrange to have fd 10
  53    (outside the range of interesting fd's during the test) set up to
  54    duplicate the original stderr.  */
  55
  56 #define BACKUP_STDERR_FILENO 10
  57 #define ASSERT_STREAM myerr
  58 #include "macros.h"
  59
  60 static FILE *myerr;
  61
  62 /* Return true if FD is open.  */
  63 static bool
  64 is_open (int fd)
  65 {
  66 #if defined _WIN32 && ! defined __CYGWIN__
  67   /* On native Windows, the initial state of unassigned standard file
  68      descriptors is that they are open but point to an
  69      INVALID_HANDLE_VALUE, and there is no fcntl.  */
  70   return (HANDLE) _get_osfhandle (fd) != INVALID_HANDLE_VALUE;
  71 #else
  72 # ifndef F_GETFL
  73 #  error Please port fcntl to your platform
  74 # endif
  75   return 0 <= fcntl (fd, F_GETFL);
  76 #endif
  77 }
  78
  79 /* Return true if FD is open and inheritable across exec/spawn.  */
  80 static bool
  81 is_inheritable (int fd)
  82 {
  83 #if defined _WIN32 && ! defined __CYGWIN__
  84   /* On native Windows, the initial state of unassigned standard file
  85      descriptors is that they are open but point to an
  86      INVALID_HANDLE_VALUE, and there is no fcntl.  */
  87   HANDLE h = (HANDLE) _get_osfhandle (fd);
  88   DWORD flags;
  89   if (h == INVALID_HANDLE_VALUE || GetHandleInformation (h, &flags) == 0)
  90     return 0;
  91   return (flags & HANDLE_FLAG_INHERIT) != 0;
  92 #else
  93 # ifndef F_GETFD
  94 #  error Please port fcntl to your platform
  95 # endif
  96   int i = fcntl (fd, F_GETFD);
  97   return 0 <= i && (i & FD_CLOEXEC) == 0;
  98 #endif
  99 }
 100
 101 /* Return true if FD is open in the given MODE, which is either
 102    O_TEXT or O_BINARY.  */
 103 static bool
 104 is_mode (int fd, int mode)
 105 {
 106   int value = set_binary_mode (fd, O_BINARY);
 107   set_binary_mode (fd, value);
 108   return mode == value;
 109 }
 110
 111 #define witness "test-dup-safer.txt"
 112
 113 int
 114 main (void)
 115 {
 116   int i;
 117   int fd;
 118   int bad_fd = getdtablesize ();
 119
 120   /* We close fd 2 later, so save it in fd 10.  */
 121   if (dup2 (STDERR_FILENO, BACKUP_STDERR_FILENO) != BACKUP_STDERR_FILENO
 122       || (myerr = fdopen (BACKUP_STDERR_FILENO, "w")) == NULL)
 123     return 2;
 124
 125   /* Create file for later checks.  */
 126   fd = creat (witness, 0600);
 127   ASSERT (STDERR_FILENO < fd);
 128
 129   /* Four iterations, with progressively more standard descriptors
 130      closed.  */
 131   for (i = -1; i <= STDERR_FILENO; i++)
 132     {
 133       if (0 <= i)
 134         ASSERT (close (i) == 0);
 135
 136       /* Detect errors.  */
 137       errno = 0;
 138       ASSERT (dup (-1) == -1);
 139       ASSERT (errno == EBADF);
 140       errno = 0;
 141       ASSERT (dup (bad_fd) == -1);
 142       ASSERT (errno == EBADF);
 143       close (fd + 1);
 144       errno = 0;
 145       ASSERT (dup (fd + 1) == -1);
 146       ASSERT (errno == EBADF);
 147
 148       /* Preserve text vs. binary.  */
 149       set_binary_mode (fd, O_BINARY);
 150       ASSERT (dup (fd) == fd + 1);
 151       ASSERT (is_open (fd + 1));
 152       ASSERT (is_inheritable (fd + 1));
 153       ASSERT (is_mode (fd + 1, O_BINARY));
 154
 155       ASSERT (close (fd + 1) == 0);
 156       set_binary_mode (fd, O_TEXT);
 157       ASSERT (dup (fd) == fd + 1);
 158       ASSERT (is_open (fd + 1));
 159       ASSERT (is_inheritable (fd + 1));
 160       ASSERT (is_mode (fd + 1, O_TEXT));
 161
 162       /* Create cloexec copy.  */
 163       ASSERT (close (fd + 1) == 0);
 164       ASSERT (fd_safer_flag (dup_cloexec (fd), O_CLOEXEC) == fd + 1);
 165       ASSERT (set_cloexec_flag (fd + 1, true) == 0);
 166       ASSERT (is_open (fd + 1));
 167       ASSERT (!is_inheritable (fd + 1));
 168       ASSERT (close (fd) == 0);
 169
 170       /* dup always creates inheritable copies.  Also, check that
 171          earliest slot past std fds is used.  */
 172       ASSERT (dup (fd + 1) == fd);
 173       ASSERT (is_open (fd));
 174       ASSERT (is_inheritable (fd));
 175       ASSERT (close (fd + 1) == 0);
 176     }
 177
 178   /* Cleanup.  */
 179   ASSERT (close (fd) == 0);
 180   ASSERT (unlink (witness) == 0);
 181
 182   return test_exit_status;
 183 }