403 lines
11 KiB
C
403 lines
11 KiB
C
/* $NetBSD: kern_pax.c,v 1.17 2007/09/21 19:14:12 dsl Exp $ */
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/*-
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* Copyright (c) 2006 Elad Efrat <elad@NetBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: kern_pax.c,v 1.17 2007/09/21 19:14:12 dsl Exp $");
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#include "opt_pax.h"
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#include <sys/param.h>
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#include <sys/proc.h>
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#include <sys/exec_elf.h>
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#include <sys/pax.h>
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#include <sys/sysctl.h>
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#include <sys/malloc.h>
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#include <sys/fileassoc.h>
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#include <sys/syslog.h>
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#include <sys/vnode.h>
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#include <sys/queue.h>
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#include <sys/kauth.h>
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#ifdef PAX_MPROTECT
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static int pax_mprotect_enabled = 1;
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static int pax_mprotect_global = PAX_MPROTECT;
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specificdata_key_t pax_mprotect_key;
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#endif
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#ifdef PAX_SEGVGUARD
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#ifndef PAX_SEGVGUARD_EXPIRY
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#define PAX_SEGVGUARD_EXPIRY (2 * 60)
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#endif
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#ifndef PAX_SEGVGUARD_SUSPENSION
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#define PAX_SEGVGUARD_SUSPENSION (10 * 60)
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#endif
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#ifndef PAX_SEGVGUARD_MAXCRASHES
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#define PAX_SEGVGUARD_MAXCRASHES 5
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#endif
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static int pax_segvguard_enabled = 1;
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static int pax_segvguard_global = PAX_SEGVGUARD;
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static int pax_segvguard_expiry = PAX_SEGVGUARD_EXPIRY;
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static int pax_segvguard_suspension = PAX_SEGVGUARD_SUSPENSION;
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static int pax_segvguard_maxcrashes = PAX_SEGVGUARD_MAXCRASHES;
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static fileassoc_t segvguard_id;
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specificdata_key_t pax_segvguard_key;
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struct pax_segvguard_uid_entry {
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uid_t sue_uid;
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size_t sue_ncrashes;
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time_t sue_expiry;
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time_t sue_suspended;
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LIST_ENTRY(pax_segvguard_uid_entry) sue_list;
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};
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struct pax_segvguard_entry {
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LIST_HEAD(, pax_segvguard_uid_entry) segv_uids;
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};
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static void pax_segvguard_cb(void *);
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#endif /* PAX_SEGVGUARD */
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/* PaX internal setspecific flags */
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#define PAX_MPROTECT_EXPLICIT_ENABLE (void *)0x01
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#define PAX_MPROTECT_EXPLICIT_DISABLE (void *)0x02
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#define PAX_SEGVGUARD_EXPLICIT_ENABLE (void *)0x03
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#define PAX_SEGVGUARD_EXPLICIT_DISABLE (void *)0x04
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SYSCTL_SETUP(sysctl_security_pax_setup, "sysctl security.pax setup")
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{
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const struct sysctlnode *rnode = NULL, *cnode;
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sysctl_createv(clog, 0, NULL, &rnode,
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CTLFLAG_PERMANENT,
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CTLTYPE_NODE, "security", NULL,
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NULL, 0, NULL, 0,
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CTL_SECURITY, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, &rnode,
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CTLFLAG_PERMANENT,
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CTLTYPE_NODE, "pax",
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SYSCTL_DESCR("PaX (exploit mitigation) features."),
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NULL, 0, NULL, 0,
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CTL_CREATE, CTL_EOL);
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cnode = rnode;
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#ifdef PAX_MPROTECT
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sysctl_createv(clog, 0, &rnode, &rnode,
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CTLFLAG_PERMANENT,
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CTLTYPE_NODE, "mprotect",
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SYSCTL_DESCR("mprotect(2) W^X restrictions."),
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NULL, 0, NULL, 0,
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CTL_CREATE, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "enabled",
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SYSCTL_DESCR("Restrictions enabled."),
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NULL, 0, &pax_mprotect_enabled, 0,
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CTL_CREATE, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "global",
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SYSCTL_DESCR("When enabled, unless explicitly "
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"specified, apply restrictions to "
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"all processes."),
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NULL, 0, &pax_mprotect_global, 0,
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CTL_CREATE, CTL_EOL);
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#endif /* PAX_MPROTECT */
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rnode = cnode;
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#ifdef PAX_SEGVGUARD
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sysctl_createv(clog, 0, &rnode, &rnode,
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CTLFLAG_PERMANENT,
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CTLTYPE_NODE, "segvguard",
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SYSCTL_DESCR("PaX segvguard."),
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NULL, 0, NULL, 0,
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CTL_CREATE, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "enabled",
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SYSCTL_DESCR("segvguard enabled."),
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NULL, 0, &pax_segvguard_enabled, 0,
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CTL_CREATE, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "global",
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SYSCTL_DESCR("segvguard all programs."),
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NULL, 0, &pax_segvguard_global, 0,
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CTL_CREATE, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "expiry_timeout",
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SYSCTL_DESCR("Entry expiry timeout (in seconds)."),
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NULL, 0, &pax_segvguard_expiry, 0,
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CTL_CREATE, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "suspend_timeout",
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SYSCTL_DESCR("Entry suspension timeout (in seconds)."),
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NULL, 0, &pax_segvguard_suspension, 0,
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CTL_CREATE, CTL_EOL);
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "max_crashes",
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SYSCTL_DESCR("Max number of crashes before expiry."),
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NULL, 0, &pax_segvguard_maxcrashes, 0,
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CTL_CREATE, CTL_EOL);
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#endif /* PAX_SEGVGUARD */
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}
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/*
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* Initialize PaX.
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*/
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void
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pax_init(void)
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{
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#ifdef PAX_SEGVGUARD
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int error;
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#endif /* PAX_SEGVGUARD */
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#ifdef PAX_MPROTECT
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proc_specific_key_create(&pax_mprotect_key, NULL);
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#endif /* PAX_MPROTECT */
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#ifdef PAX_SEGVGUARD
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error = fileassoc_register("segvguard", pax_segvguard_cb,
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&segvguard_id);
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if (error) {
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panic("pax_init: segvguard_id: error=%d\n", error);
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}
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proc_specific_key_create(&pax_segvguard_key, NULL);
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#endif /* PAX_SEGVGUARD */
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}
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void
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pax_adjust(struct lwp *l, uint32_t f)
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{
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#ifdef PAX_MPROTECT
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if (pax_mprotect_enabled) {
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if (f & ELF_NOTE_PAX_MPROTECT)
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proc_setspecific(l->l_proc, pax_mprotect_key,
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PAX_MPROTECT_EXPLICIT_ENABLE);
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if (f & ELF_NOTE_PAX_NOMPROTECT)
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proc_setspecific(l->l_proc, pax_mprotect_key,
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PAX_MPROTECT_EXPLICIT_DISABLE);
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}
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#endif /* PAX_MPROTECT */
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#ifdef PAX_SEGVGUARD
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if (pax_segvguard_enabled) {
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if (f & ELF_NOTE_PAX_GUARD)
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proc_setspecific(l->l_proc, pax_segvguard_key,
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PAX_SEGVGUARD_EXPLICIT_ENABLE);
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if (f & ELF_NOTE_PAX_NOGUARD)
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proc_setspecific(l->l_proc, pax_segvguard_key,
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PAX_SEGVGUARD_EXPLICIT_DISABLE);
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}
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#endif /* PAX_SEGVGUARD */
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}
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#ifdef PAX_MPROTECT
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void
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pax_mprotect(struct lwp *l, vm_prot_t *prot, vm_prot_t *maxprot)
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{
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void *t;
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if (!pax_mprotect_enabled)
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return;
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t = proc_getspecific(l->l_proc, pax_mprotect_key);
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if ((pax_mprotect_global && t == PAX_MPROTECT_EXPLICIT_DISABLE) ||
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(!pax_mprotect_global && t != PAX_MPROTECT_EXPLICIT_ENABLE))
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return;
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if ((*prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) != VM_PROT_EXECUTE) {
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*prot &= ~VM_PROT_EXECUTE;
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*maxprot &= ~VM_PROT_EXECUTE;
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} else {
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*prot &= ~VM_PROT_WRITE;
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*maxprot &= ~VM_PROT_WRITE;
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}
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}
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#endif /* PAX_MPROTECT */
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#ifdef PAX_SEGVGUARD
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static void
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pax_segvguard_cb(void *v)
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{
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struct pax_segvguard_entry *p;
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struct pax_segvguard_uid_entry *up;
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if (v == NULL)
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return;
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p = v;
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while ((up = LIST_FIRST(&p->segv_uids)) != NULL) {
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LIST_REMOVE(up, sue_list);
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free(up, M_TEMP);
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}
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free(v, M_TEMP);
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}
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/*
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* Called when a process of image vp generated a segfault.
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*/
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int
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pax_segvguard(struct lwp *l, struct vnode *vp, const char *name,
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bool crashed)
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{
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struct pax_segvguard_entry *p;
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struct pax_segvguard_uid_entry *up;
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struct timeval tv;
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uid_t uid;
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void *t;
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bool have_uid;
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if (!pax_segvguard_enabled)
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return (0);
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t = proc_getspecific(l->l_proc, pax_segvguard_key);
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if ((pax_segvguard_global && t == PAX_SEGVGUARD_EXPLICIT_DISABLE) ||
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(!pax_segvguard_global && t != PAX_SEGVGUARD_EXPLICIT_ENABLE))
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return (0);
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if (vp == NULL)
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return (EFAULT);
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/* Check if we already monitor the file. */
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p = fileassoc_lookup(vp, segvguard_id);
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/* Fast-path if starting a program we don't know. */
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if (p == NULL && !crashed)
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return (0);
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microtime(&tv);
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/*
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* If a program we don't know crashed, we need to create a new entry
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* for it.
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*/
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if (p == NULL) {
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p = malloc(sizeof(*p), M_TEMP, M_WAITOK);
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fileassoc_add(vp, segvguard_id, p);
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LIST_INIT(&p->segv_uids);
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/*
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* Initialize a new entry with "crashes so far" of 1.
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* The expiry time is when we purge the entry if it didn't
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* reach the limit.
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*/
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up = malloc(sizeof(*up), M_TEMP, M_WAITOK);
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up->sue_uid = kauth_cred_getuid(l->l_cred);
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up->sue_ncrashes = 1;
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up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
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up->sue_suspended = 0;
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LIST_INSERT_HEAD(&p->segv_uids, up, sue_list);
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return (0);
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}
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/*
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* A program we "know" either executed or crashed again.
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* See if it's a culprit we're familiar with.
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*/
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uid = kauth_cred_getuid(l->l_cred);
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have_uid = false;
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LIST_FOREACH(up, &p->segv_uids, sue_list) {
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if (up->sue_uid == uid) {
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have_uid = true;
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break;
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}
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}
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/*
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* It's someone else. Add an entry for him if we crashed.
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*/
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if (!have_uid) {
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if (crashed) {
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up = malloc(sizeof(*up), M_TEMP, M_WAITOK);
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up->sue_uid = uid;
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up->sue_ncrashes = 1;
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up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
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up->sue_suspended = 0;
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LIST_INSERT_HEAD(&p->segv_uids, up, sue_list);
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}
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return (0);
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}
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if (crashed) {
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/* Check if timer on previous crashes expired first. */
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if (up->sue_expiry < tv.tv_sec) {
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log(LOG_INFO, "PaX Segvguard: [%s] Suspension"
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" expired.\n", name ? name : "unknown");
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up->sue_ncrashes = 1;
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up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
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up->sue_suspended = 0;
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return (0);
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}
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up->sue_ncrashes++;
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if (up->sue_ncrashes >= pax_segvguard_maxcrashes) {
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log(LOG_ALERT, "PaX Segvguard: [%s] Suspending "
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"execution for %d seconds after %zu crashes.\n",
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name ? name : "unknown", pax_segvguard_suspension,
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up->sue_ncrashes);
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/* Suspend this program for a while. */
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up->sue_suspended = tv.tv_sec + pax_segvguard_suspension;
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up->sue_ncrashes = 0;
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up->sue_expiry = 0;
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}
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} else {
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/* Are we supposed to be suspended? */
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if (up->sue_suspended > tv.tv_sec) {
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log(LOG_ALERT, "PaX Segvguard: [%s] Preventing "
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"execution due to repeated segfaults.\n", name ?
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name : "unknown");
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return (EPERM);
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}
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}
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return (0);
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}
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#endif /* PAX_SEGVGUARD */
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