sysdeps/posix/euidaccess.c

   1 /* euidaccess -- check if effective user id can access file
   2    Copyright (C) 1990, 1991, 1995 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., 675 Mass Ave,
  19 Cambridge, MA 02139, USA.  */
  20
  21 /* Written by David MacKenzie and Torbjorn Granlund.
  22    Adapted for GNU C library by Roland McGrath.  */
  23
  24 #ifdef 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
  70 #if defined(EACCES) && !defined(EACCESS)
  71 #define EACCESS EACCES
  72 #endif
  73
  74 #ifndef F_OK
  75 #define F_OK 0
  76 #define X_OK 1
  77 #define W_OK 2
  78 #define R_OK 4
  79 #endif
  80
  81 #if !defined (S_IROTH) && defined (R_OK)
  82 # define S_IROTH R_OK
  83 #endif
  84 #if !defined (S_IWOTH) && defined (W_OK)
  85 # define S_IWOTH W_OK
  86 #endif
  87 #if !defined (S_IXOTH) && defined (X_OK)
  88 # define S_IXOTH X_OK
  89 #endif
  90
  91
  92 #ifdef _LIBC
  93
  94 #define group_member __group_member
  95
  96 #else
  97
  98 /* The user's real user id. */
  99 static uid_t uid;
 100
 101 /* The user's real group id. */
 102 static gid_t gid;
 103
 104 /* The user's effective user id. */
 105 static uid_t euid;
 106
 107 /* The user's effective group id. */
 108 static gid_t egid;
 109
 110 /* Nonzero if UID, GID, EUID, and EGID have valid values. */
 111 static int have_ids = 0;
 112
 113 #ifdef HAVE_GETGROUPS
 114 int group_member ();
 115 #else
 116 #define group_member(gid)       0
 117 #endif
 118
 119 #endif
 120
 121
 122 /* Return 0 if the user has permission of type MODE on file PATH;
 123    otherwise, return -1 and set `errno' to EACCESS.
 124    Like access, except that it uses the effective user and group
 125    id's instead of the real ones, and it does not check for read-only
 126    filesystem, text busy, etc. */
 127
 128 int
 129 euidaccess (path, mode)
 130      const char *path;
 131      int mode;
 132 {
 133   struct stat stats;
 134   int granted;
 135
 136 #ifdef  _LIBC
 137   uid_t uid = getuid (), euid = geteuid ();
 138   gid_t gid = getgid (), egid = getegid ();
 139 #else
 140   if (have_ids == 0)
 141     {
 142       have_ids = 1;
 143       uid = getuid ();
 144       gid = getgid ();
 145       euid = geteuid ();
 146       egid = getegid ();
 147     }
 148 #endif
 149
 150   if (uid == euid && gid == egid)
 151     /* If we are not set-uid or set-gid, access does the same.  */
 152     return access (path, mode);
 153
 154   if (stat (path, &stats))
 155     return -1;
 156
 157   mode &= (X_OK | W_OK | R_OK); /* Clear any bogus bits. */
 158 #if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
 159   ?error Oops, portability assumptions incorrect.
 160 #endif
 161
 162   if (mode == F_OK)
 163     return 0;                   /* The file exists. */
 164
 165   /* The super-user can read and write any file, and execute any file
 166      that anyone can execute. */
 167   if (euid == 0 && ((mode & X_OK) == 0
 168                     || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
 169     return 0;
 170
 171   if (euid == stats.st_uid)
 172     granted = (unsigned) (stats.st_mode & (mode << 6)) >> 6;
 173   else if (egid == stats.st_gid || group_member (stats.st_gid))
 174     granted = (unsigned) (stats.st_mode & (mode << 3)) >> 3;
 175   else
 176     granted = (stats.st_mode & mode);
 177   if (granted == mode)
 178     return 0;
 179   errno = EACCESS;
 180   return -1;
 181 }
 182 \f
 183 #ifdef TEST
 184 #include <stdio.h>
 185 #include <errno.h>
 186 #include "error.h"
 187
 188 char *program_name;
 189
 190 int
 191 main (argc, argv)
 192      int argc;
 193      char **argv;
 194 {
 195   char *file;
 196   int mode;
 197   int err;
 198
 199   program_name = argv[0];
 200   if (argc < 3)
 201     abort ();
 202   file = argv[1];
 203   mode = atoi (argv[2]);
 204
 205   err = euidaccess (file, mode);
 206   printf ("%d\n", err);
 207   if (err != 0)
 208     error (0, errno, "%s", file);
 209   exit (0);
 210 }
 211 #endif