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