FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_priv.c
1 /*-
2 * Copyright (c) 2006 nCircle Network Security, Inc.
3 * Copyright (c) 2009 Robert N. M. Watson
4 * All rights reserved.
5 *
6 * This software was developed by Robert N. M. Watson for the TrustedBSD
7 * Project under contract to nCircle Network Security, Inc.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR, NCIRCLE NETWORK SECURITY,
22 * INC., OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
24 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
25 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
26 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
27 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #include "opt_kdtrace.h"
32 #include "opt_mac.h"
33
34 #include <sys/cdefs.h>
35 __FBSDID("$FreeBSD$");
36
37 #include <sys/param.h>
38 #include <sys/jail.h>
39 #include <sys/kernel.h>
40 #include <sys/priv.h>
41 #include <sys/proc.h>
42 #include <sys/sdt.h>
43 #include <sys/sysctl.h>
44 #include <sys/systm.h>
45
46 #include <security/mac/mac_framework.h>
47
48 /*
49 * `suser_enabled' (which can be set by the security.bsd.suser_enabled
50 * sysctl) determines whether the system 'super-user' policy is in effect. If
51 * it is nonzero, an effective uid of 0 connotes special privilege,
52 * overriding many mandatory and discretionary protections. If it is zero,
53 * uid 0 is offered no special privilege in the kernel security policy.
54 * Setting it to zero may seriously impact the functionality of many existing
55 * userland programs, and should not be done without careful consideration of
56 * the consequences.
57 */
58 static int suser_enabled = 1;
59 SYSCTL_INT(_security_bsd, OID_AUTO, suser_enabled, CTLFLAG_RW,
60 &suser_enabled, 0, "processes with uid 0 have privilege");
61 TUNABLE_INT("security.bsd.suser_enabled", &suser_enabled);
62
63 SDT_PROVIDER_DEFINE(priv);
64 SDT_PROBE_DEFINE1(priv, kernel, priv_check, priv_ok, "int");
65 SDT_PROBE_DEFINE1(priv, kernel, priv_check, priv_err, "int");
66
67 /*
68 * Check a credential for privilege. Lots of good reasons to deny privilege;
69 * only a few to grant it.
70 */
71 int
72 priv_check_cred(struct ucred *cred, int priv, int flags)
73 {
74 int error;
75
76 KASSERT(PRIV_VALID(priv), ("priv_check_cred: invalid privilege %d",
77 priv));
78
79 /*
80 * We first evaluate policies that may deny the granting of
81 * privilege unilaterally.
82 */
83 #ifdef MAC
84 error = mac_priv_check(cred, priv);
85 if (error)
86 goto out;
87 #endif
88
89 /*
90 * Jail policy will restrict certain privileges that may otherwise be
91 * be granted.
92 */
93 error = prison_priv_check(cred, priv);
94 if (error)
95 goto out;
96
97 /*
98 * Having determined if privilege is restricted by various policies,
99 * now determine if privilege is granted. At this point, any policy
100 * may grant privilege. For now, we allow short-circuit boolean
101 * evaluation, so may not call all policies. Perhaps we should.
102 *
103 * Superuser policy grants privilege based on the effective (or in
104 * the case of specific privileges, real) uid being 0. We allow the
105 * superuser policy to be globally disabled, although this is
106 * currenty of limited utility.
107 */
108 if (suser_enabled) {
109 switch (priv) {
110 case PRIV_MAXFILES:
111 case PRIV_MAXPROC:
112 case PRIV_PROC_LIMIT:
113 if (cred->cr_ruid == 0) {
114 error = 0;
115 goto out;
116 }
117 break;
118
119 default:
120 if (cred->cr_uid == 0) {
121 error = 0;
122 goto out;
123 }
124 break;
125 }
126 }
127
128 /*
129 * Now check with MAC, if enabled, to see if a policy module grants
130 * privilege.
131 */
132 #ifdef MAC
133 if (mac_priv_grant(cred, priv) == 0) {
134 error = 0;
135 goto out;
136 }
137 #endif
138
139 /*
140 * The default is deny, so if no policies have granted it, reject
141 * with a privilege error here.
142 */
143 error = EPERM;
144 out:
145 if (error) {
146 SDT_PROBE(priv, kernel, priv_check, priv_err, priv, 0, 0, 0,
147 0);
148 } else {
149 SDT_PROBE(priv, kernel, priv_check, priv_ok, priv, 0, 0, 0,
150 0);
151 }
152 return (error);
153 }
154
155 int
156 priv_check(struct thread *td, int priv)
157 {
158
159 KASSERT(td == curthread, ("priv_check: td != curthread"));
160
161 return (priv_check_cred(td->td_ucred, priv, 0));
162 }
163
164 /*
165 * Historical suser() wrapper functions, which now simply request PRIV_ROOT.
166 * These will be removed in the near future, and exist solely because
167 * the kernel and modules are not yet fully adapted to the new model.
168 */
169 int
170 suser_cred(struct ucred *cred, int flags)
171 {
172
173 return (priv_check_cred(cred, PRIV_ROOT, flags));
174 }
175
176 int
177 suser(struct thread *td)
178 {
179
180 KASSERT(td == curthread, ("suser: td != curthread"));
181
182 return (suser_cred(td->td_ucred, 0));
183 }
Cache object: 5b361e474ed1700e59332bb6ee3986c0
|