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 static 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 /* 72 * We first evaluate policies that may deny the granting of 73 * privilege unilaterally. 74 */ 75 #ifdef MAC 76 error = mac_priv_check(cred, priv); 77 if (error) 78 return (error); 79 #endif 80 81 /* 82 * Jail policy will restrict certain privileges that may otherwise be 83 * be granted. 84 */ 85 error = prison_priv_check(cred, priv); 86 if (error) 87 return (error); 88 89 /* 90 * Having determined if privilege is restricted by various policies, 91 * now determine if privilege is granted. At this point, any policy 92 * may grant privilege. For now, we allow short-circuit boolean 93 * evaluation, so may not call all policies. Perhaps we should. 94 * 95 * Superuser policy grants privilege based on the effective (or in 96 * the case of specific privileges, real) uid being 0. We allow the 97 * superuser policy to be globally disabled, although this is 98 * currenty of limited utility. 99 */ 100 if (suser_enabled) { 101 switch (priv) { 102 case PRIV_MAXFILES: 103 case PRIV_MAXPROC: 104 case PRIV_PROC_LIMIT: 105 if (cred->cr_ruid == 0) 106 return (0); 107 break; 108 109 default: 110 if (cred->cr_uid == 0) 111 return (0); 112 break; 113 } 114 } 115 116 /* 117 * Now check with MAC, if enabled, to see if a policy module grants 118 * privilege. 119 */ 120 #ifdef MAC 121 if (mac_priv_grant(cred, priv) == 0) 122 return (0); 123 #endif 124 return (EPERM); 125 } 126 127 int 128 priv_check(struct thread *td, int priv) 129 { 130 131 KASSERT(td == curthread, ("priv_check: td != curthread")); 132 133 return (priv_check_cred(td->td_ucred, priv, 0)); 134 } 135 136 /* 137 * Historical suser() wrapper functions, which now simply request PRIV_ROOT. 138 * These will be removed in the near future, and exist solely because 139 * the kernel and modules are not yet fully adapted to the new model. 140 */ 141 int 142 suser_cred(struct ucred *cred, int flags) 143 { 144 145 return (priv_check_cred(cred, PRIV_ROOT, flags)); 146 } 147 148 int 149 suser(struct thread *td) 150 { 151 152 KASSERT(td == curthread, ("suser: td != curthread")); 153 154 return (suser_cred(td->td_ucred, 0)); 155 } 156