sysdeps/posix/euidaccess.c

   1 /* Check if effective user id can access file
   2    Copyright (C) 1990, 1991, 1995, 1996, 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 /* Written by David MacKenzie and Torbjorn Granlund.
  21    Adapted for GNU C library by Roland McGrath.  */
  22
  23 #ifdef HAVE_CONFIG_H
  24 #include <config.h>
  25 #endif
  26
  27 #include <sys/types.h>
  28 #include <sys/stat.h>
  29
  30 #ifdef S_IEXEC
  31 #ifndef S_IXUSR
  32 #define S_IXUSR S_IEXEC
  33 #endif
  34 #ifndef S_IXGRP
  35 #define S_IXGRP (S_IEXEC >> 3)
  36 #endif
  37 #ifndef S_IXOTH
  38 #define S_IXOTH (S_IEXEC >> 6)
  39 #endif
  40 #endif /* S_IEXEC */
  41
  42 #if defined (HAVE_UNISTD_H) || defined (_LIBC)
  43 #include <unistd.h>
  44 #endif
  45
  46 #ifdef _POSIX_VERSION
  47 #include <limits.h>
  48 #if !defined(NGROUPS_MAX) || NGROUPS_MAX < 1
  49 #undef NGROUPS_MAX
  50 #define NGROUPS_MAX sysconf (_SC_NGROUPS_MAX)
  51 #endif /* NGROUPS_MAX */
  52
  53 #else /* not _POSIX_VERSION */
  54 uid_t getuid ();
  55 gid_t getgid ();
  56 uid_t geteuid ();
  57 gid_t getegid ();
  58 #include <sys/param.h>
  59 #if !defined(NGROUPS_MAX) && defined(NGROUPS)
  60 #define NGROUPS_MAX NGROUPS
  61 #endif /* not NGROUPS_MAX and NGROUPS */
  62 #endif /* not POSIX_VERSION */
  63
  64 #include <errno.h>
  65 #ifndef errno
  66 extern int errno;
  67 #endif
  68 #ifndef __set_errno
  69 #define __set_errno(val) errno = (val)
  70 #endif
  71
  72 #if defined(EACCES) && !defined(EACCESS)
  73 #define EACCESS EACCES
  74 #endif
  75
  76 #ifndef F_OK
  77 #define F_OK 0
  78 #define X_OK 1
  79 #define W_OK 2
  80 #define R_OK 4
  81 #endif
  82
  83 #if !defined (S_IROTH) && defined (R_OK)
  84 # define S_IROTH R_OK
  85 #endif
  86 #if !defined (S_IWOTH) && defined (W_OK)
  87 # define S_IWOTH W_OK
  88 #endif
  89 #if !defined (S_IXOTH) && defined (X_OK)
  90 # define S_IXOTH X_OK
  91 #endif
  92
  93
  94 #ifdef _LIBC
  95
  96 #define group_member __group_member
  97 #define euidaccess __euidaccess
  98
  99 #else
 100
 101 /* The user's real user id. */
 102 static uid_t uid;
 103
 104 /* The user's real group id. */
 105 static gid_t gid;
 106
 107 #ifdef HAVE_GETGROUPS
 108 int group_member ();
 109 #else
 110 #define group_member(gid)       0
 111 #endif
 112
 113 #endif
 114
 115 /* The user's effective user id. */
 116 static uid_t euid;
 117
 118 /* The user's effective group id. */
 119 static gid_t egid;
 120
 121 /* Nonzero if UID, GID, EUID, and EGID have valid values. */
 122 static int have_ids = 0;
 123
 124
 125 /* Return 0 if the user has permission of type MODE on file PATH;
 126    otherwise, return -1 and set `errno' to EACCESS.
 127    Like access, except that it uses the effective user and group
 128    id's instead of the real ones, and it does not check for read-only
 129    filesystem, text busy, etc. */
 130
 131 int
 132 euidaccess (path, mode)
 133      const char *path;
 134      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