1
2 /* Check if effective user id can access file
3 Copyright (C) 1990, 91, 95, 96, 97, 98, 99 Free Software Foundation, Inc.
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 not,
18 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
20
21 /* Written by David MacKenzie and Torbjorn Granlund.
22 Adapted for GNU C library by Roland McGrath. Adapted further
23 for use with xisp by Dimitrios P. Bouras <dbouras@hol.gr> */
24
25 #include <sys/types.h>
26 #include <sys/stat.h>
27
28 #ifdef S_IEXEC
29 #ifndef S_IXUSR
30 #define S_IXUSR S_IEXEC
31 #endif
32 #ifndef S_IXGRP
33 #define S_IXGRP (S_IEXEC >> 3)
34 #endif
35 #ifndef S_IXOTH
36 #define S_IXOTH (S_IEXEC >> 6)
37 #endif
38 #endif /* S_IEXEC */
39
40 #include <unistd.h>
41
42 uid_t getuid ();
43 gid_t getgid ();
44 uid_t geteuid ();
45 gid_t getegid ();
46 #include <sys/param.h>
47 #if !defined(NGROUPS_MAX) && defined(NGROUPS)
48 #define NGROUPS_MAX NGROUPS
49 #endif /* not NGROUPS_MAX and NGROUPS */
50
51 #include <errno.h>
52 #ifndef errno
53 extern int errno;
54 #endif
55 #ifndef __set_errno
56 #define __set_errno(val) errno = (val)
57 #endif
58
59 #if defined(EACCES) && !defined(EACCESS)
60 #define EACCESS EACCES
61 #endif
62
63 #ifndef F_OK
64 #define F_OK 0
65 #define X_OK 1
66 #define W_OK 2
67 #define R_OK 4
68 #endif
69
70 #if !defined (S_IROTH) && defined (R_OK)
71 # define S_IROTH R_OK
72 #endif
73 #if !defined (S_IWOTH) && defined (W_OK)
74 # define S_IWOTH W_OK
75 #endif
76 #if !defined (S_IXOTH) && defined (X_OK)
77 # define S_IXOTH X_OK
78 #endif
79
80 #include <alloca.h>
81 #ifndef NGROUPS_MAX
82 #define NGROUPS_MAX 16 /* First guess. */
83 #endif
group_member(gid)84 int group_member (gid)
85 gid_t gid;
86 {
87 int n, size;
88 gid_t *groups;
89
90 size = NGROUPS_MAX;
91 do
92 {
93 groups = alloca (size * sizeof *groups);
94 n = getgroups (size, groups);
95 size *= 2;
96 } while (n == size / 2);
97
98 while (n > 0)
99 if (groups[n--] == gid)
100 return 1;
101
102 return 0;
103 }
104
105 /* The user's real user id. */
106 static uid_t uid;
107
108 /* The user's real group id. */
109 static gid_t gid;
110
111 /* The user's effective user id. */
112 static uid_t euid;
113
114 /* The user's effective group id. */
115 static gid_t egid;
116
117 /* Nonzero if UID, GID, EUID, and EGID have valid values. */
118 static int have_ids;
119
120 /* Return 0 if the user has permission of type MODE on file PATH;
121 otherwise, return -1 and set `errno' to EACCESS.
122 Like access, except that it uses the effective user and group
123 id's instead of the real ones, and it does not check for read-only
124 filesystem, text busy, etc. */
125
126 int
xisp_euidaccess(path,mode)127 xisp_euidaccess (path, mode)
128 const char *path;
129 int mode;
130 {
131 struct stat stats;
132 int granted;
133
134 if (have_ids == 0)
135 {
136 have_ids = 1;
137 uid = getuid ();
138 gid = getgid ();
139 euid = geteuid ();
140 egid = getegid ();
141 }
142
143 if (uid == euid && gid == egid)
144 /* If we are not set-uid or set-gid, access does the same. */
145 return access (path, mode);
146
147 if (stat (path, &stats))
148 return -1;
149
150 mode &= (X_OK | W_OK | R_OK); /* Clear any bogus bits. */
151 #if R_OK != S_IROTH || W_OK != S_IWOTH || X_OK != S_IXOTH
152 #error Oops, portability assumptions incorrect.
153 #endif
154
155 if (mode == F_OK)
156 return 0; /* The file exists. */
157
158 /* The super-user can read and write any file, and execute any file
159 that anyone can execute. */
160 if (euid == 0 && ((mode & X_OK) == 0
161 || (stats.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
162 return 0;
163
164 if (euid == stats.st_uid)
165 granted = (unsigned) (stats.st_mode & (mode << 6)) >> 6;
166 else if (egid == stats.st_gid || group_member (stats.st_gid))
167 granted = (unsigned) (stats.st_mode & (mode << 3)) >> 3;
168 else
169 granted = (stats.st_mode & mode);
170 if (granted == mode)
171 return 0;
172 __set_errno (EACCESS);
173 return -1;
174 }
175
176