| 1 | /* euidaccess -- check if effective user id can access file |
| 2 | |
| 3 | Copyright (C) 1990-1991, 1995, 1998, 2000, 2003-2006, 2008-2014 Free |
| 4 | Software 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 3 of the License, or |
| 11 | (at your option) 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 |
| 19 | along with this program. If not, see <http://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 | |
| 33 | #include "root-uid.h" |
| 34 | |
| 35 | #if HAVE_LIBGEN_H |
| 36 | # include <libgen.h> |
| 37 | #endif |
| 38 | |
| 39 | #include <errno.h> |
| 40 | #ifndef __set_errno |
| 41 | # define __set_errno(val) errno = (val) |
| 42 | #endif |
| 43 | |
| 44 | #if defined EACCES && !defined EACCESS |
| 45 | # define EACCESS EACCES |
| 46 | #endif |
| 47 | |
| 48 | #ifndef F_OK |
| 49 | # define F_OK 0 |
| 50 | # define X_OK 1 |
| 51 | # define W_OK 2 |
| 52 | # define R_OK 4 |
| 53 | #endif |
| 54 | |
| 55 | |
| 56 | #ifdef _LIBC |
| 57 | |
| 58 | # define access __access |
| 59 | # define getuid __getuid |
| 60 | # define getgid __getgid |
| 61 | # define geteuid __geteuid |
| 62 | # define getegid __getegid |
| 63 | # define group_member __group_member |
| 64 | # define euidaccess __euidaccess |
| 65 | # undef stat |
| 66 | # define stat stat64 |
| 67 | |
| 68 | #endif |
| 69 | |
| 70 | /* Return 0 if the user has permission of type MODE on FILE; |
| 71 | otherwise, return -1 and set 'errno'. |
| 72 | Like access, except that it uses the effective user and group |
| 73 | id's instead of the real ones, and it does not always check for read-only |
| 74 | file system, text busy, etc. */ |
| 75 | |
| 76 | int |
| 77 | euidaccess (const char *file, int mode) |
| 78 | { |
| 79 | #if HAVE_FACCESSAT /* glibc, AIX 7, Solaris 11, Cygwin 1.7 */ |
| 80 | return faccessat (AT_FDCWD, file, mode, AT_EACCESS); |
| 81 | #elif defined EFF_ONLY_OK /* IRIX, OSF/1, Interix */ |
| 82 | return access (file, mode | EFF_ONLY_OK); |
| 83 | #elif defined ACC_SELF /* AIX */ |
| 84 | return accessx (file, mode, ACC_SELF); |
| 85 | #elif HAVE_EACCESS /* FreeBSD */ |
| 86 | return eaccess (file, mode); |
| 87 | #else /* Mac OS X, NetBSD, OpenBSD, HP-UX, Solaris, Cygwin, mingw, BeOS */ |
| 88 | |
| 89 | uid_t uid = getuid (); |
| 90 | gid_t gid = getgid (); |
| 91 | uid_t euid = geteuid (); |
| 92 | gid_t egid = getegid (); |
| 93 | struct stat stats; |
| 94 | |
| 95 | # if HAVE_DECL_SETREGID && PREFER_NONREENTRANT_EUIDACCESS |
| 96 | |
| 97 | /* Define PREFER_NONREENTRANT_EUIDACCESS if you prefer euidaccess to |
| 98 | return the correct result even if this would make it |
| 99 | nonreentrant. Define this only if your entire application is |
| 100 | safe even if the uid or gid might temporarily change. If your |
| 101 | application uses signal handlers or threads it is probably not |
| 102 | safe. */ |
| 103 | |
| 104 | if (mode == F_OK) |
| 105 | return stat (file, &stats); |
| 106 | else |
| 107 | { |
| 108 | int result; |
| 109 | int saved_errno; |
| 110 | |
| 111 | if (uid != euid) |
| 112 | setreuid (euid, uid); |
| 113 | if (gid != egid) |
| 114 | setregid (egid, gid); |
| 115 | |
| 116 | result = access (file, mode); |
| 117 | saved_errno = errno; |
| 118 | |
| 119 | /* Restore them. */ |
| 120 | if (uid != euid) |
| 121 | setreuid (uid, euid); |
| 122 | if (gid != egid) |
| 123 | setregid (gid, egid); |
| 124 | |
| 125 | errno = saved_errno; |
| 126 | return result; |
| 127 | } |
| 128 | |
| 129 | # else |
| 130 | |
| 131 | /* The following code assumes the traditional Unix model, and is not |
| 132 | correct on systems that have ACLs or the like. However, it's |
| 133 | better than nothing, and it is reentrant. */ |
| 134 | |
| 135 | unsigned int granted; |
| 136 | if (uid == euid && gid == egid) |
| 137 | /* If we are not set-uid or set-gid, access does the same. */ |
| 138 | return access (file, mode); |
| 139 | |
| 140 | if (stat (file, &stats) != 0) |
| 141 | return -1; |
| 142 | |
| 143 | /* The super-user can read and write any file, and execute any file |
| 144 | that anyone can execute. */ |
| 145 | if (euid == ROOT_UID |
| 146 | && ((mode & X_OK) == 0 |
| 147 | || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)))) |
| 148 | return 0; |
| 149 | |
| 150 | /* Convert the mode to traditional form, clearing any bogus bits. */ |
| 151 | if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0) |
| 152 | mode &= 7; |
| 153 | else |
| 154 | mode = ((mode & R_OK ? 4 : 0) |
| 155 | + (mode & W_OK ? 2 : 0) |
| 156 | + (mode & X_OK ? 1 : 0)); |
| 157 | |
| 158 | if (mode == 0) |
| 159 | return 0; /* The file exists. */ |
| 160 | |
| 161 | /* Convert the file's permission bits to traditional form. */ |
| 162 | if (S_IRUSR == (4 << 6) && S_IWUSR == (2 << 6) && S_IXUSR == (1 << 6) |
| 163 | && S_IRGRP == (4 << 3) && S_IWGRP == (2 << 3) && S_IXGRP == (1 << 3) |
| 164 | && S_IROTH == (4 << 0) && S_IWOTH == (2 << 0) && S_IXOTH == (1 << 0)) |
| 165 | granted = stats.st_mode; |
| 166 | else |
| 167 | granted = ((stats.st_mode & S_IRUSR ? 4 << 6 : 0) |
| 168 | + (stats.st_mode & S_IWUSR ? 2 << 6 : 0) |
| 169 | + (stats.st_mode & S_IXUSR ? 1 << 6 : 0) |
| 170 | + (stats.st_mode & S_IRGRP ? 4 << 3 : 0) |
| 171 | + (stats.st_mode & S_IWGRP ? 2 << 3 : 0) |
| 172 | + (stats.st_mode & S_IXGRP ? 1 << 3 : 0) |
| 173 | + (stats.st_mode & S_IROTH ? 4 << 0 : 0) |
| 174 | + (stats.st_mode & S_IWOTH ? 2 << 0 : 0) |
| 175 | + (stats.st_mode & S_IXOTH ? 1 << 0 : 0)); |
| 176 | |
| 177 | if (euid == stats.st_uid) |
| 178 | granted >>= 6; |
| 179 | else if (egid == stats.st_gid || group_member (stats.st_gid)) |
| 180 | granted >>= 3; |
| 181 | |
| 182 | if ((mode & ~granted) == 0) |
| 183 | return 0; |
| 184 | __set_errno (EACCESS); |
| 185 | return -1; |
| 186 | |
| 187 | # endif |
| 188 | #endif |
| 189 | } |
| 190 | #undef euidaccess |
| 191 | #ifdef weak_alias |
| 192 | weak_alias (__euidaccess, euidaccess) |
| 193 | #endif |
| 194 | \f |
| 195 | #ifdef TEST |
| 196 | # include <error.h> |
| 197 | # include <stdio.h> |
| 198 | # include <stdlib.h> |
| 199 | |
| 200 | char *program_name; |
| 201 | |
| 202 | int |
| 203 | main (int argc, char **argv) |
| 204 | { |
| 205 | char *file; |
| 206 | int mode; |
| 207 | int err; |
| 208 | |
| 209 | program_name = argv[0]; |
| 210 | if (argc < 3) |
| 211 | abort (); |
| 212 | file = argv[1]; |
| 213 | mode = atoi (argv[2]); |
| 214 | |
| 215 | err = euidaccess (file, mode); |
| 216 | printf ("%d\n", err); |
| 217 | if (err != 0) |
| 218 | error (0, errno, "%s", file); |
| 219 | exit (0); |
| 220 | } |
| 221 | #endif |