lib/euidaccess.c

   1 /* euidaccess -- check if effective user id can access file
   2
   3    Copyright (C) 1990, 1991, 1995, 1998, 2000, 2003 Free Software
   4    Foundation, Inc.
   5
   6    This file is part of the GNU C Library.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2, or (at your option)
  11    any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License along
  19    with this program; if not, write to the Free Software Foundation,
  20    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  21
  22 /* Written by David MacKenzie and Torbjorn Granlund.
  23    Adapted for GNU C library by Roland McGrath.  */
  24
  25 #if HAVE_CONFIG_H
  26 # include <config.h>
  27 #endif
  28
  29 #ifndef _LIBC
  30 # include "euidaccess.h"
  31 #endif
  32
  33 #include <sys/types.h>
  34 #include <sys/stat.h>
  35
  36 #ifdef S_IEXEC
  37 # ifndef S_IXUSR
  38 #  define S_IXUSR S_IEXEC
  39 # endif
  40 # ifndef S_IXGRP
  41 #  define S_IXGRP (S_IEXEC >> 3)
  42 # endif
  43 # ifndef S_IXOTH
  44 #  define S_IXOTH (S_IEXEC >> 6)
  45 # endif
  46 #endif /* S_IEXEC */
  47
  48 #if defined (HAVE_UNISTD_H) || defined (_LIBC)
  49 # include <unistd.h>
  50 #endif
  51
  52 #ifdef _POSIX_VERSION
  53 # include <limits.h>
  54 # if !defined(NGROUPS_MAX) || NGROUPS_MAX < 1
  55 #  undef NGROUPS_MAX
  56 #  define NGROUPS_MAX sysconf (_SC_NGROUPS_MAX)
  57 # endif /* NGROUPS_MAX */
  58
  59 #else /* not _POSIX_VERSION */
  60 uid_t getuid ();
  61 gid_t getgid ();
  62 uid_t geteuid ();
  63 gid_t getegid ();
  64 # include <sys/param.h>
  65 # if !defined(NGROUPS_MAX) && defined(NGROUPS)
  66 #  define NGROUPS_MAX NGROUPS
  67 # endif /* not NGROUPS_MAX and NGROUPS */
  68 #endif /* not POSIX_VERSION */
  69
  70 #include <errno.h>
  71 #ifndef errno
  72 extern int errno;
  73 #endif
  74 #ifndef __set_errno
  75 # define __set_errno(val) errno = (val)
  76 #endif
  77
  78 #if defined(EACCES) && !defined(EACCESS)
  79 # define EACCESS EACCES
  80 #endif
  81
  82 #ifndef F_OK
  83 # define F_OK 0
  84 # define X_OK 1
  85 # define W_OK 2
  86 # define R_OK 4
  87 #endif
  88
  89 #if !defined (S_IROTH) && defined (R_OK)
  90 # define S_IROTH R_OK
  91 #endif
  92
  93 #if !defined (S_IWOTH) && defined (W_OK)
  94 # define S_IWOTH W_OK
  95 #endif
  96
  97 #if !defined (S_IXOTH) && defined (X_OK)
  98 # define S_IXOTH X_OK
  99 #endif
 100
 101 #ifdef _LIBC
 102
 103 # define group_member __group_member
 104 # define euidaccess __euidaccess
 105
 106 #else
 107
 108 /* The user's real user id. */
 109 static uid_t uid;
 110
 111 /* The user's real group id. */
 112 static gid_t gid;
 113
 114 # if HAVE_GETGROUPS
 115 int group_member ();
 116 # else
 117 #  define group_member(gid)     0
 118 # endif
 119
 120 #endif
 121
 122 /* The user's effective user id. */
 123 static uid_t euid;
 124
 125 /* The user's effective group id. */
 126 static gid_t egid;
 127
 128 /* Nonzero if UID, GID, EUID, and EGID have valid values. */
 129 static int have_ids;
 130
 131
 132 /* Return 0 if the user has permission of type MODE on file PATH;
 133    otherwise, return -1 and set `errno' to EACCESS.
 134    Like access, except that it uses the effective user and group
 135    id's instead of the real ones, and it does not check for read-only
 136    filesystem, text busy, etc. */
 137
 138 int
 139 euidaccess (const char *path, int mode)
 140 {
 141   struct stat stats;
 142   int granted;
 143
 144 #ifdef  _LIBC
 145   if (! __libc_enable_secure)
 146     /* If we are not set-uid or set-gid, access does the same.  */
 147     return __access (path, mode);
 148 #else
 149   if (have_ids == 0)
 150     {
 151       have_ids = 1;
 152       uid = getuid ();
 153       gid = getgid ();
 154       euid = geteuid ();
 155       egid = getegid ();
 156     }
 157
 158   if (uid == euid && gid == egid)
 159     /* If we are not set-uid or set-gid, access does the same.  */
 160     return access (path, mode);
 161 #endif
 162
 163   if (stat (path, &stats))
 164     return -1;
 165
 166   mode &= (X_OK | W_OK | R_OK); /* Clear any bogus bits. */
 167 #if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
 168   ?error Oops, portability assumptions incorrect.
 169 #endif
 170
 171   if (mode == F_OK)
 172     return 0;                   /* The file exists. */
 173
 174 #ifdef  _LIBC
 175   /* Now we need the IDs.  */
 176   if (have_ids == 0)
 177     {
 178       have_ids = 1;
 179       euid = __geteuid ();
 180       egid = __getegid ();
 181     }
 182 #endif
 183
 184   /* The super-user can read and write any file, and execute any file
 185      that anyone can execute. */
 186   if (euid == 0 && ((mode & X_OK) == 0
 187                     || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
 188     return 0;
 189
 190   if (euid == stats.st_uid)
 191     granted = (unsigned) (stats.st_mode & (mode << 6)) >> 6;
 192   else if (egid == stats.st_gid || group_member (stats.st_gid))
 193     granted = (unsigned) (stats.st_mode & (mode << 3)) >> 3;
 194   else
 195     granted = (stats.st_mode & mode);
 196   if (granted == mode)
 197     return 0;
 198   __set_errno (EACCESS);
 199   return -1;
 200 }
 201 #undef euidaccess
 202 #ifdef weak_alias
 203 weak_alias (__euidaccess, euidaccess)
 204 #endif
 205 \f
 206 #ifdef TEST
 207 # include <stdio.h>
 208 # include <errno.h>
 209 # include "error.h"
 210
 211 char *program_name;
 212
 213 int
 214 main (int argc, char **argv)
 215 {
 216   char *file;
 217   int mode;
 218   int err;
 219
 220   program_name = argv[0];
 221   if (argc < 3)
 222     abort ();
 223   file = argv[1];
 224   mode = atoi (argv[2]);
 225
 226   err = euidaccess (file, mode);
 227   printf ("%d\n", err);
 228   if (err != 0)
 229     error (0, errno, "%s", file);
 230   exit (0);
 231 }
 232 #endif