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