lib/euidaccess.c

   1 /* euidaccess -- check if effective user id can access file
   2    Copyright (C) 1990, 1991, 1995, 1998, 2000 Free Software Foundation, Inc.
   3
   4 This file is part of the GNU C Library.
   5
   6 The GNU C Library is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU Library General Public License as
   8 published by the Free Software Foundation; either version 2 of the
   9 License, or (at your option) any later version.
  10
  11 The GNU C Library is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 Library General Public License for more details.
  15
  16 You should have received a copy of the GNU Library General Public
  17 License along with the GNU C Library; see the file COPYING.LIB.  If
  18 not, write to the Free Software Foundation, Inc., 59 Temple Place -
  19 Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 /* Written by David MacKenzie and Torbjorn Granlund.
  22    Adapted for GNU C library by Roland McGrath.  */
  23
  24 #if HAVE_CONFIG_H
  25 # include <config.h>
  26 #endif
  27
  28 #include <sys/types.h>
  29 #include <sys/stat.h>
  30
  31 #ifdef S_IEXEC
  32 # ifndef S_IXUSR
  33 #  define S_IXUSR S_IEXEC
  34 # endif
  35 # ifndef S_IXGRP
  36 #  define S_IXGRP (S_IEXEC >> 3)
  37 # endif
  38 # ifndef S_IXOTH
  39 #  define S_IXOTH (S_IEXEC >> 6)
  40 # endif
  41 #endif /* S_IEXEC */
  42
  43 #if defined (HAVE_UNISTD_H) || defined (_LIBC)
  44 # include <unistd.h>
  45 #endif
  46
  47 #ifdef _POSIX_VERSION
  48 # include <limits.h>
  49 # if !defined(NGROUPS_MAX) || NGROUPS_MAX < 1
  50 #  undef NGROUPS_MAX
  51 #  define NGROUPS_MAX sysconf (_SC_NGROUPS_MAX)
  52 # endif /* NGROUPS_MAX */
  53
  54 #else /* not _POSIX_VERSION */
  55 uid_t getuid ();
  56 gid_t getgid ();
  57 uid_t geteuid ();
  58 gid_t getegid ();
  59 # include <sys/param.h>
  60 # if !defined(NGROUPS_MAX) && defined(NGROUPS)
  61 #  define NGROUPS_MAX NGROUPS
  62 # endif /* not NGROUPS_MAX and NGROUPS */
  63 #endif /* not POSIX_VERSION */
  64
  65 #include <errno.h>
  66 #ifndef errno
  67 extern int errno;
  68 #endif
  69 #ifndef __set_errno
  70 # define __set_errno(val) errno = (val)
  71 #endif
  72
  73 #if defined(EACCES) && !defined(EACCESS)
  74 # define EACCESS EACCES
  75 #endif
  76
  77 #ifndef F_OK
  78 # define F_OK 0
  79 # define X_OK 1
  80 # define W_OK 2
  81 # define R_OK 4
  82 #endif
  83
  84 #if !defined (S_IROTH) && defined (R_OK)
  85 # define S_IROTH R_OK
  86 #endif
  87
  88 #if !defined (S_IWOTH) && defined (W_OK)
  89 # define S_IWOTH W_OK
  90 #endif
  91
  92 #if !defined (S_IXOTH) && defined (X_OK)
  93 # define S_IXOTH X_OK
  94 #endif
  95
  96 #ifdef _LIBC
  97
  98 # define group_member __group_member
  99 # define euidaccess __euidaccess
 100
 101 #else
 102
 103 /* The user's real user id. */
 104 static uid_t uid;
 105
 106 /* The user's real group id. */
 107 static gid_t gid;
 108
 109 # if HAVE_GETGROUPS
 110 int group_member ();
 111 # else
 112 #  define group_member(gid)     0
 113 # endif
 114
 115 #endif
 116
 117 /* The user's effective user id. */
 118 static uid_t euid;
 119
 120 /* The user's effective group id. */
 121 static gid_t egid;
 122
 123 /* Nonzero if UID, GID, EUID, and EGID have valid values. */
 124 static int have_ids;
 125
 126
 127 /* Return 0 if the user has permission of type MODE on file PATH;
 128    otherwise, return -1 and set `errno' to EACCESS.
 129    Like access, except that it uses the effective user and group
 130    id's instead of the real ones, and it does not check for read-only
 131    filesystem, text busy, etc. */
 132
 133 int
 134 euidaccess (const char *path, int mode)
 135 {
 136   struct stat stats;
 137   int granted;
 138
 139 #ifdef  _LIBC
 140   if (! __libc_enable_secure)
 141     /* If we are not set-uid or set-gid, access does the same.  */
 142     return __access (path, mode);
 143 #else
 144   if (have_ids == 0)
 145     {
 146       have_ids = 1;
 147       uid = getuid ();
 148       gid = getgid ();
 149       euid = geteuid ();
 150       egid = getegid ();
 151     }
 152
 153   if (uid == euid && gid == egid)
 154     /* If we are not set-uid or set-gid, access does the same.  */
 155     return access (path, mode);
 156 #endif
 157
 158   if (stat (path, &stats))
 159     return -1;
 160
 161   mode &= (X_OK | W_OK | R_OK); /* Clear any bogus bits. */
 162 #if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
 163   ?error Oops, portability assumptions incorrect.
 164 #endif
 165
 166   if (mode == F_OK)
 167     return 0;                   /* The file exists. */
 168
 169 #ifdef  _LIBC
 170   /* Now we need the IDs.  */
 171   if (have_ids == 0)
 172     {
 173       have_ids = 1;
 174       euid = __geteuid ();
 175       egid = __getegid ();
 176     }
 177 #endif
 178
 179   /* The super-user can read and write any file, and execute any file
 180      that anyone can execute. */
 181   if (euid == 0 && ((mode & X_OK) == 0
 182                     || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
 183     return 0;
 184
 185   if (euid == stats.st_uid)
 186     granted = (unsigned) (stats.st_mode & (mode << 6)) >> 6;
 187   else if (egid == stats.st_gid || group_member (stats.st_gid))
 188     granted = (unsigned) (stats.st_mode & (mode << 3)) >> 3;
 189   else
 190     granted = (stats.st_mode & mode);
 191   if (granted == mode)
 192     return 0;
 193   __set_errno (EACCESS);
 194   return -1;
 195 }
 196 #undef euidaccess
 197 #ifdef weak_alias
 198 weak_alias (__euidaccess, euidaccess)
 199 #endif
 200 \f
 201 #ifdef TEST
 202 # include <stdio.h>
 203 # include <errno.h>
 204 # include "error.h"
 205
 206 char *program_name;
 207
 208 int
 209 main (argc, argv)
 210      int argc;
 211      char **argv;
 212 {
 213   char *file;
 214   int mode;
 215   int err;
 216
 217   program_name = argv[0];
 218   if (argc < 3)
 219     abort ();
 220   file = argv[1];
 221   mode = atoi (argv[2]);
 222
 223   err = euidaccess (file, mode);
 224   printf ("%d\n", err);
 225   if (err != 0)
 226     error (0, errno, "%s", file);
 227   exit (0);
 228 }
 229 #endif