root/lib/euidaccess.c

DEFINITIONS

1. euidaccess
2. weak_alias

     1 /* euidaccess -- check if effective user id can access file
     2 
     3    Copyright (C) 1990-1991, 1995, 1998, 2000, 2003-2006, 2008-2023 Free
     4    Software Foundation, Inc.
     5 
     6    This file is part of the GNU C Library.
     7 
     8    This file is free software: you can redistribute it and/or modify
     9    it under the terms of the GNU Lesser General Public License as
    10    published by the Free Software Foundation; either version 2.1 of the
    11    License, or (at your option) any later version.
    12 
    13    This file 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 Lesser General Public License for more details.
    17 
    18    You should have received a copy of the GNU Lesser General Public License
    19    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
    20 
    21 /* Written by David MacKenzie and Torbjorn Granlund.
    22    Adapted for GNU C library by Roland McGrath.  */
    23 
    24 #ifndef _LIBC
    25 # include <config.h>
    26 #endif
    27 
    28 #include <fcntl.h>
    29 #include <sys/types.h>
    30 #include <sys/stat.h>
    31 #include <unistd.h>
    32 #if defined _WIN32 && ! defined __CYGWIN__
    33 # include <io.h>
    34 #else
    35 # include "root-uid.h"
    36 #endif
    37 
    38 #if HAVE_LIBGEN_H
    39 # include <libgen.h>
    40 #endif
    41 
    42 #include <errno.h>
    43 #ifndef __set_errno
    44 # define __set_errno(val) errno = (val)
    45 #endif
    46 
    47 #if defined EACCES && !defined EACCESS
    48 # define EACCESS EACCES
    49 #endif
    50 
    51 #ifndef F_OK
    52 # define F_OK 0
    53 # define X_OK 1
    54 # define W_OK 2
    55 # define R_OK 4
    56 #endif
    57 
    58 
    59 #ifdef _LIBC
    60 
    61 # define access __access
    62 # define getuid __getuid
    63 # define getgid __getgid
    64 # define geteuid __geteuid
    65 # define getegid __getegid
    66 # define group_member __group_member
    67 # define euidaccess __euidaccess
    68 # undef stat
    69 # define stat stat64
    70 
    71 #endif
    72 
    73 /* Return 0 if the user has permission of type MODE on FILE;
    74    otherwise, return -1 and set 'errno'.
    75    Like access, except that it uses the effective user and group
    76    id's instead of the real ones, and it does not always check for read-only
    77    file system, text busy, etc.  */
    78 
    79 int
    80 euidaccess (const char *file, int mode)
    81 {
    82 #if HAVE_FACCESSAT                   /* glibc, AIX 7, Solaris 11, Cygwin 1.7 */
    83   return faccessat (AT_FDCWD, file, mode, AT_EACCESS);
    84 #elif defined EFF_ONLY_OK               /* IRIX, OSF/1, Interix */
    85   return access (file, mode | EFF_ONLY_OK);
    86 #elif defined ACC_SELF                  /* AIX */
    87   return accessx (file, mode, ACC_SELF);
    88 #elif HAVE_EACCESS                      /* FreeBSD */
    89   return eaccess (file, mode);
    90 #elif defined _WIN32 && ! defined __CYGWIN__  /* mingw */
    91   return _access (file, mode);
    92 #else              /* Mac OS X, NetBSD, OpenBSD, HP-UX, Solaris, Cygwin, BeOS */
    93 
    94   uid_t uid = getuid ();
    95   gid_t gid = getgid ();
    96   uid_t euid = geteuid ();
    97   gid_t egid = getegid ();
    98   struct stat stats;
    99 
   100 # if HAVE_DECL_SETREGID && PREFER_NONREENTRANT_EUIDACCESS
   101 
   102   /* Define PREFER_NONREENTRANT_EUIDACCESS if you prefer euidaccess to
   103      return the correct result even if this would make it
   104      nonreentrant.  Define this only if your entire application is
   105      safe even if the uid or gid might temporarily change.  If your
   106      application uses signal handlers or threads it is probably not
   107      safe.  */
   108 
   109   if (mode == F_OK)
   110     {
   111       int result = stat (file, &stats);
   112       return result != 0 && errno == EOVERFLOW ? 0 : result;
   113     }
   114   else
   115     {
   116       int result;
   117       int saved_errno;
   118 
   119       if (uid != euid)
   120         setreuid (euid, uid);
   121       if (gid != egid)
   122         setregid (egid, gid);
   123 
   124       result = access (file, mode);
   125       saved_errno = errno;
   126 
   127       /* Restore them.  */
   128       if (uid != euid)
   129         setreuid (uid, euid);
   130       if (gid != egid)
   131         setregid (gid, egid);
   132 
   133       errno = saved_errno;
   134       return result;
   135     }
   136 
   137 # else
   138 
   139   /* The following code assumes the traditional Unix model, and is not
   140      correct on systems that have ACLs or the like.  However, it's
   141      better than nothing, and it is reentrant.  */
   142 
   143   unsigned int granted;
   144   if (uid == euid && gid == egid)
   145     /* If we are not set-uid or set-gid, access does the same.  */
   146     return access (file, mode);
   147 
   148   if (stat (file, &stats) == -1)
   149     return mode == F_OK && errno == EOVERFLOW ? 0 : -1;
   150 
   151   /* The super-user can read and write any file, and execute any file
   152      that anyone can execute.  */
   153   if (euid == ROOT_UID
   154       && ((mode & X_OK) == 0
   155           || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
   156     return 0;
   157 
   158   /* Convert the mode to traditional form, clearing any bogus bits.  */
   159   if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
   160     mode &= 7;
   161   else
   162     mode = ((mode & R_OK ? 4 : 0)
   163             + (mode & W_OK ? 2 : 0)
   164             + (mode & X_OK ? 1 : 0));
   165 
   166   if (mode == 0)
   167     return 0;                   /* The file exists.  */
   168 
   169   /* Convert the file's permission bits to traditional form.  */
   170   if (S_IRUSR == (4 << 6) && S_IWUSR == (2 << 6) && S_IXUSR == (1 << 6)
   171       && S_IRGRP == (4 << 3) && S_IWGRP == (2 << 3) && S_IXGRP == (1 << 3)
   172       && S_IROTH == (4 << 0) && S_IWOTH == (2 << 0) && S_IXOTH == (1 << 0))
   173     granted = stats.st_mode;
   174   else
   175     granted = ((stats.st_mode & S_IRUSR ? 4 << 6 : 0)
   176                + (stats.st_mode & S_IWUSR ? 2 << 6 : 0)
   177                + (stats.st_mode & S_IXUSR ? 1 << 6 : 0)
   178                + (stats.st_mode & S_IRGRP ? 4 << 3 : 0)
   179                + (stats.st_mode & S_IWGRP ? 2 << 3 : 0)
   180                + (stats.st_mode & S_IXGRP ? 1 << 3 : 0)
   181                + (stats.st_mode & S_IROTH ? 4 << 0 : 0)
   182                + (stats.st_mode & S_IWOTH ? 2 << 0 : 0)
   183                + (stats.st_mode & S_IXOTH ? 1 << 0 : 0));
   184 
   185   if (euid == stats.st_uid)
   186     granted >>= 6;
   187   else if (egid == stats.st_gid || group_member (stats.st_gid))
   188     granted >>= 3;
   189 
   190   if ((mode & ~granted) == 0)
   191     return 0;
   192   __set_errno (EACCESS);
   193   return -1;
   194 
   195 # endif
   196 #endif
   197 }
   198 #undef euidaccess
   199 #ifdef weak_alias
   200 weak_alias (__euidaccess, euidaccess)
   201 #endif
   202 
   203 #ifdef TEST
   204 # include <error.h>
   205 # include <stdio.h>
   206 # include <stdlib.h>
   207 
   208 int
   209 main (int argc, char **argv)
   210 {
   211   char *file;
   212   int mode;
   213   int err;
   214 
   215   if (argc < 3)
   216     abort ();
   217   file = argv[1];
   218   mode = atoi (argv[2]);
   219 
   220   err = euidaccess (file, mode);
   221   printf ("%d\n", err);
   222   if (err != 0)
   223     error (0, errno, "%s", file);
   224   exit (0);
   225 }
   226 #endif