diff options
Diffstat (limited to 'sys/kern/kern_priv.c')
| -rw-r--r-- | sys/kern/kern_priv.c | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/sys/kern/kern_priv.c b/sys/kern/kern_priv.c new file mode 100644 index 0000000..2f70c2b --- /dev/null +++ b/sys/kern/kern_priv.c @@ -0,0 +1,179 @@ +/*- + * 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); + +static int unprivileged_mlock = 1; +SYSCTL_INT(_security_bsd, OID_AUTO, unprivileged_mlock, CTLFLAG_RW|CTLFLAG_TUN, + &unprivileged_mlock, 0, "Allow non-root users to call mlock(2)"); +TUNABLE_INT("security.bsd.unprivileged_mlock", &unprivileged_mlock); + +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; + + if (unprivileged_mlock) { + /* + * Allow unprivileged users to call mlock(2)/munlock(2) and + * mlockall(2)/munlockall(2). + */ + switch (priv) { + case PRIV_VM_MLOCK: + case PRIV_VM_MUNLOCK: + error = 0; + 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)); +} |
