/*- * Copyright (c) 2006 nCircle Network Security, Inc. * Copyright (c) 2009 Robert N. M. Watson * 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_kdtrace.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/sdt.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); SDT_PROVIDER_DEFINE(priv); SDT_PROBE_DEFINE1(priv, kernel, priv_check, priv_ok, priv-ok, "int"); SDT_PROBE_DEFINE1(priv, kernel, priv_check, priv_err, priv-err, "int"); /* * 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) goto out; #endif /* * Jail policy will restrict certain privileges that may otherwise be * be granted. */ error = prison_priv_check(cred, priv); if (error) goto out; /* * 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) { error = 0; goto out; } break; default: if (cred->cr_uid == 0) { error = 0; goto out; } break; } } /* * Now check with MAC, if enabled, to see if a policy module grants * privilege. */ #ifdef MAC if (mac_priv_grant(cred, priv) == 0) { error = 0; goto out; } #endif /* * The default is deny, so if no policies have granted it, reject * with a privilege error here. */ error = EPERM; out: if (error) { SDT_PROBE(priv, kernel, priv_check, priv_err, priv, 0, 0, 0, 0); } else { SDT_PROBE(priv, kernel, priv_check, priv_ok, priv, 0, 0, 0, 0); } return (error); } int priv_check(struct thread *td, int priv) { KASSERT(td == curthread, ("priv_check: td != curthread")); return (priv_check_cred(td->td_ucred, priv, 0)); }