1 /*
2 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28 /* $NetBSD: sysv_ipc.c,v 1.7 1994/06/29 06:33:11 cgd Exp $ */
29
30 /*
31 * Copyright (c) 1994 Herb Peyerl <[email protected]>
32 * All rights reserved.
33 *
34 * Redistribution and use in source and binary forms, with or without
35 * modification, are permitted provided that the following conditions
36 * are met:
37 * 1. Redistributions of source code must retain the above copyright
38 * notice, this list of conditions and the following disclaimer.
39 * 2. Redistributions in binary form must reproduce the above copyright
40 * notice, this list of conditions and the following disclaimer in the
41 * documentation and/or other materials provided with the distribution.
42 * 3. All advertising materials mentioning features or use of this software
43 * must display the following acknowledgement:
44 * This product includes software developed by Herb Peyerl.
45 * 4. The name of Herb Peyerl may not be used to endorse or promote products
46 * derived from this software without specific prior written permission.
47 *
48 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
49 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
50 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
51 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
52 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
53 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
54 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
55 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
56 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
57 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
58 */
59
60
61 #include <sys/param.h>
62 #include <sys/ipc.h>
63 #include <sys/stat.h> /* mode constants */
64 #include <sys/ucred.h>
65 #include <sys/kauth.h>
66
67
68 /*
69 * Check for ipc permission
70 */
71
72
73 /*
74 * ipc_perm
75 *
76 * perm->mode mode of the object
77 * mode mode bits we want to test
78 *
79 * Returns: 0 Success
80 * EPERM
81 * EACCES
82 *
83 * Notes: The IPC_M bit is special, in that it may only be granted to
84 * root, the creating user, or the owning user.
85 *
86 * This code does not use posix_cred_access() because of the
87 * need to check both creator and owner separately when we are
88 * considering a rights grant. Because of this, we need to do
89 * two evaluations when the values are inequal, which can lead
90 * us to defeat the callout avoidance optimization. So we do
91 * the work here, inline. This is less than optimal for any
92 * future work involving opacity of of POSIX credentials.
93 *
94 * Setting up the mode_owner / mode_group / mode_world implicitly
95 * masks the IPC_M bit off. This is intentional.
96 *
97 * See the posix_cred_access() implementation for algorithm
98 * information.
99 */
100 int
ipcperm(kauth_cred_t cred,struct ipc_perm * perm,int mode_req)101 ipcperm(kauth_cred_t cred, struct ipc_perm *perm, int mode_req)
102 {
103 uid_t uid = kauth_cred_getuid(cred); /* avoid multiple calls */
104 int want_mod_controlinfo = (mode_req & IPC_M);
105 int is_member;
106 mode_t mode_owner = (perm->mode & S_IRWXU);
107 mode_t mode_group = (mode_t)((perm->mode & S_IRWXG) << 3);
108 mode_t mode_world = (mode_t)((perm->mode & S_IRWXO) << 6);
109
110 /* Grant all rights to super user */
111 if (!suser(cred, (u_short *)NULL)) {
112 return 0;
113 }
114
115 /* Grant or deny rights based on ownership */
116 if (uid == perm->cuid || uid == perm->uid) {
117 if (want_mod_controlinfo) {
118 return 0;
119 }
120
121 return (mode_req & mode_owner) == mode_req ? 0 : EACCES;
122 } else {
123 /* everyone else who wants to modify control info is denied */
124 if (want_mod_controlinfo) {
125 return EPERM;
126 }
127 }
128
129 /*
130 * Combined group and world rights check, if no owner rights; positive
131 * asssertion of gid/cgid equality avoids an extra callout in the
132 * common case.
133 */
134 if ((mode_req & mode_group & mode_world) == mode_req) {
135 return 0;
136 } else {
137 if ((mode_req & mode_group) != mode_req) {
138 if ((!kauth_cred_ismember_gid(cred, perm->gid, &is_member) && is_member) &&
139 ((perm->gid == perm->cgid) ||
140 (!kauth_cred_ismember_gid(cred, perm->cgid, &is_member) && is_member))) {
141 return EACCES;
142 } else {
143 if ((mode_req & mode_world) != mode_req) {
144 return EACCES;
145 } else {
146 return 0;
147 }
148 }
149 } else {
150 if ((!kauth_cred_ismember_gid(cred, perm->gid, &is_member) && is_member) ||
151 ((perm->gid != perm->cgid) &&
152 (!kauth_cred_ismember_gid(cred, perm->cgid, &is_member) && is_member))) {
153 return 0;
154 } else {
155 if ((mode_req & mode_world) != mode_req) {
156 return EACCES;
157 } else {
158 return 0;
159 }
160 }
161 }
162 }
163 }
164