841 lines
22 KiB
C
841 lines
22 KiB
C
/* $NetBSD: kern_pax.c,v 1.60 2017/06/25 04:10:47 snj Exp $ */
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/*
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* Copyright (c) 2015 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Maxime Villard.
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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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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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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 1.60 2017/06/25 04:10:47 snj 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.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/kmem.h>
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#include <sys/mman.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/bitops.h>
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#include <sys/kauth.h>
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#include <sys/cprng.h>
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#ifdef PAX_ASLR_DEBUG
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#define PAX_DPRINTF(_fmt, args...) \
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do if (pax_aslr_debug) uprintf("%s: " _fmt "\n", __func__, ##args); \
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while (/*CONSTCOND*/0)
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#else
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#define PAX_DPRINTF(_fmt, args...) do {} while (/*CONSTCOND*/0)
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#endif
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#ifdef PAX_ASLR
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#include <sys/mman.h>
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int pax_aslr_enabled = 1;
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int pax_aslr_global = PAX_ASLR;
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#ifndef PAX_ASLR_DELTA_MMAP_LSB
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#define PAX_ASLR_DELTA_MMAP_LSB PGSHIFT
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#endif
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#ifndef PAX_ASLR_DELTA_MMAP_LEN
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#define PAX_ASLR_DELTA_MMAP_LEN ((sizeof(void *) * NBBY) / 2)
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#endif
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#ifndef PAX_ASLR_DELTA_MMAP_LEN32
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#define PAX_ASLR_DELTA_MMAP_LEN32 ((sizeof(uint32_t) * NBBY) / 2)
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#endif
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#ifndef PAX_ASLR_DELTA_STACK_LSB
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#define PAX_ASLR_DELTA_STACK_LSB PGSHIFT
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#endif
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#ifndef PAX_ASLR_DELTA_STACK_LEN
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#define PAX_ASLR_DELTA_STACK_LEN ((sizeof(void *) * NBBY) / 4)
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#endif
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#ifndef PAX_ASLR_DELTA_STACK_LEN32
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#define PAX_ASLR_DELTA_STACK_LEN32 ((sizeof(uint32_t) * NBBY) / 4)
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#endif
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#define PAX_ASLR_MAX_STACK_WASTE 8
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#ifdef PAX_ASLR_DEBUG
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int pax_aslr_debug;
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/* flag set means disable */
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int pax_aslr_flags;
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uint32_t pax_aslr_rand;
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#define PAX_ASLR_STACK 0x01
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#define PAX_ASLR_STACK_GAP 0x02
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#define PAX_ASLR_MMAP 0x04
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#define PAX_ASLR_EXEC_OFFSET 0x08
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#define PAX_ASLR_RTLD_OFFSET 0x10
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#define PAX_ASLR_FIXED 0x20
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#endif
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static bool pax_aslr_elf_flags_active(uint32_t);
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#endif /* PAX_ASLR */
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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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static int pax_mprotect_ptrace = 1;
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static bool pax_mprotect_elf_flags_active(uint32_t);
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#endif /* PAX_MPROTECT */
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#ifdef PAX_MPROTECT_DEBUG
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int pax_mprotect_debug;
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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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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 bool pax_segvguard_elf_flags_active(uint32_t);
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static void pax_segvguard_cleanup_cb(void *);
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#endif /* PAX_SEGVGUARD */
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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, "pax",
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SYSCTL_DESCR("PaX (exploit mitigation) features."),
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NULL, 0, NULL, 0,
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CTL_SECURITY, CTL_CREATE, CTL_EOL);
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cnode = rnode;
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#ifdef PAX_MPROTECT
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rnode = cnode;
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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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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "ptrace",
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SYSCTL_DESCR("When enabled, allow ptrace(2) to "
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"override mprotect permissions on traced "
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"processes"),
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NULL, 0, &pax_mprotect_ptrace, 0,
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CTL_CREATE, CTL_EOL);
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#ifdef PAX_MPROTECT_DEBUG
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "debug",
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SYSCTL_DESCR("print mprotect changes."),
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NULL, 0, &pax_mprotect_debug, 0,
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CTL_CREATE, CTL_EOL);
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#endif
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#endif /* PAX_MPROTECT */
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#ifdef PAX_SEGVGUARD
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rnode = cnode;
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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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#ifdef PAX_ASLR
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rnode = cnode;
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sysctl_createv(clog, 0, &rnode, &rnode,
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CTLFLAG_PERMANENT,
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CTLTYPE_NODE, "aslr",
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SYSCTL_DESCR("Address Space Layout Randomization."),
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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_aslr_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 to all processes."),
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NULL, 0, &pax_aslr_global, 0,
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CTL_CREATE, CTL_EOL);
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#ifdef PAX_ASLR_DEBUG
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
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CTLTYPE_INT, "debug",
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SYSCTL_DESCR("Print ASLR selected addresses."),
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NULL, 0, &pax_aslr_debug, 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, "flags",
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SYSCTL_DESCR("Disable/Enable select ASLR features."),
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NULL, 0, &pax_aslr_flags, 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, "rand",
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SYSCTL_DESCR("Use the given fixed random value"),
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NULL, 0, &pax_aslr_rand, 0,
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CTL_CREATE, CTL_EOL);
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#endif
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sysctl_createv(clog, 0, &rnode, NULL,
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CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE,
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CTLTYPE_INT, "mmap_len",
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SYSCTL_DESCR("Number of bits randomized for "
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"mmap(2) calls."),
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NULL, PAX_ASLR_DELTA_MMAP_LEN, 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_IMMEDIATE,
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CTLTYPE_INT, "stack_len",
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SYSCTL_DESCR("Number of bits randomized for "
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"the stack."),
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NULL, PAX_ASLR_DELTA_STACK_LEN, 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_IMMEDIATE,
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CTLTYPE_INT, "exec_len",
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SYSCTL_DESCR("Number of bits randomized for "
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"the PIE exec base."),
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NULL, PAX_ASLR_DELTA_EXEC_LEN, NULL, 0,
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CTL_CREATE, CTL_EOL);
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#endif /* PAX_ASLR */
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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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error = fileassoc_register("segvguard", pax_segvguard_cleanup_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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#endif /* PAX_SEGVGUARD */
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#ifdef PAX_ASLR
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/* Adjust maximum stack by the size we can consume for ASLR */
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extern rlim_t maxsmap;
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maxsmap = MAXSSIZ - (MAXSSIZ / PAX_ASLR_MAX_STACK_WASTE);
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// XXX: compat32 is not handled.
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#endif
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}
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void
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pax_set_flags(struct exec_package *epp, struct proc *p)
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{
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p->p_pax = epp->ep_pax_flags;
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#ifdef PAX_MPROTECT
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if (pax_mprotect_ptrace == 0)
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return;
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/*
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* If we are running under the debugger, turn off MPROTECT so
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* the debugger can insert/delete breakpoints
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*/
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if (p->p_slflag & PSL_TRACED)
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p->p_pax &= ~P_PAX_MPROTECT;
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#endif
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}
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void
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pax_setup_elf_flags(struct exec_package *epp, uint32_t elf_flags)
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{
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uint32_t flags = 0;
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#ifdef PAX_ASLR
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if (pax_aslr_elf_flags_active(elf_flags)) {
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flags |= P_PAX_ASLR;
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}
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#endif
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#ifdef PAX_MPROTECT
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if (pax_mprotect_elf_flags_active(elf_flags)) {
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flags |= P_PAX_MPROTECT;
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}
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#endif
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#ifdef PAX_SEGVGUARD
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if (pax_segvguard_elf_flags_active(elf_flags)) {
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flags |= P_PAX_GUARD;
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}
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#endif
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epp->ep_pax_flags = flags;
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}
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#if defined(PAX_MPROTECT) || defined(PAX_SEGVGUARD) || defined(PAX_ASLR)
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static inline bool
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pax_flags_active(uint32_t flags, uint32_t opt)
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{
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if (!(flags & opt))
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return false;
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return true;
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}
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#endif /* PAX_MPROTECT || PAX_SEGVGUARD || PAX_ASLR */
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#ifdef PAX_MPROTECT
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static bool
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pax_mprotect_elf_flags_active(uint32_t flags)
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{
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if (!pax_mprotect_enabled)
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return false;
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if (pax_mprotect_global && (flags & ELF_NOTE_PAX_NOMPROTECT) != 0) {
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/* Mprotect explicitly disabled */
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return false;
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}
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if (!pax_mprotect_global && (flags & ELF_NOTE_PAX_MPROTECT) == 0) {
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/* Mprotect not requested */
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return false;
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}
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return true;
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}
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vm_prot_t
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pax_mprotect_maxprotect(
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#ifdef PAX_MPROTECT_DEBUG
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const char *file, size_t line,
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#endif
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struct lwp *l, vm_prot_t active, vm_prot_t extra, vm_prot_t maxprot)
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{
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uint32_t flags;
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flags = l->l_proc->p_pax;
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if (!pax_flags_active(flags, P_PAX_MPROTECT))
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return maxprot;
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return (active|extra) & maxprot;
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}
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int
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pax_mprotect_validate(
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#ifdef PAX_MPROTECT_DEBUG
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const char *file, size_t line,
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#endif
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struct lwp *l, vm_prot_t prot)
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{
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uint32_t flags;
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flags = l->l_proc->p_pax;
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if (!pax_flags_active(flags, P_PAX_MPROTECT))
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return 0;
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if ((prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) ==
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(VM_PROT_WRITE|VM_PROT_EXECUTE)) {
|
|
#ifdef PAX_MPROTECT_DEBUG
|
|
struct proc *p = l->l_proc;
|
|
|
|
if (pax_mprotect_debug)
|
|
printf("%s: %s,%zu: %d.%d (%s): WX rejected\n",
|
|
__func__, file, line,
|
|
p->p_pid, l->l_lid, p->p_comm);
|
|
#endif
|
|
return EACCES;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Bypass MPROTECT for traced processes
|
|
*/
|
|
int
|
|
pax_mprotect_prot(struct lwp *l)
|
|
{
|
|
uint32_t flags;
|
|
|
|
flags = l->l_proc->p_pax;
|
|
if (!pax_flags_active(flags, P_PAX_MPROTECT))
|
|
return 0;
|
|
if (pax_mprotect_ptrace < 2)
|
|
return 0;
|
|
return UVM_EXTRACT_PROT_ALL;
|
|
}
|
|
|
|
|
|
#endif /* PAX_MPROTECT */
|
|
|
|
#ifdef PAX_ASLR
|
|
static bool
|
|
pax_aslr_elf_flags_active(uint32_t flags)
|
|
{
|
|
if (!pax_aslr_enabled)
|
|
return false;
|
|
if (pax_aslr_global && (flags & ELF_NOTE_PAX_NOASLR) != 0) {
|
|
/* ASLR explicitly disabled */
|
|
return false;
|
|
}
|
|
if (!pax_aslr_global && (flags & ELF_NOTE_PAX_ASLR) == 0) {
|
|
/* ASLR not requested */
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static bool
|
|
pax_aslr_epp_active(struct exec_package *epp)
|
|
{
|
|
if (__predict_false((epp->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0))
|
|
return false;
|
|
return pax_flags_active(epp->ep_pax_flags, P_PAX_ASLR);
|
|
}
|
|
|
|
static bool
|
|
pax_aslr_active(struct lwp *l)
|
|
{
|
|
return pax_flags_active(l->l_proc->p_pax, P_PAX_ASLR);
|
|
}
|
|
|
|
void
|
|
pax_aslr_init_vm(struct lwp *l, struct vmspace *vm, struct exec_package *ep)
|
|
{
|
|
if (!pax_aslr_active(l))
|
|
return;
|
|
|
|
if (__predict_false((ep->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0))
|
|
return;
|
|
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_MMAP)
|
|
return;
|
|
#endif
|
|
|
|
uint32_t len = (ep->ep_flags & EXEC_32) ?
|
|
PAX_ASLR_DELTA_MMAP_LEN32 : PAX_ASLR_DELTA_MMAP_LEN;
|
|
|
|
uint32_t rand = cprng_fast32();
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_FIXED)
|
|
rand = pax_aslr_rand;
|
|
#endif
|
|
vm->vm_aslr_delta_mmap = PAX_ASLR_DELTA(rand,
|
|
PAX_ASLR_DELTA_MMAP_LSB, len);
|
|
|
|
PAX_DPRINTF("delta_mmap=%#jx/%u",
|
|
(uintmax_t)vm->vm_aslr_delta_mmap, len);
|
|
}
|
|
|
|
void
|
|
pax_aslr_mmap(struct lwp *l, vaddr_t *addr, vaddr_t orig_addr, int f)
|
|
{
|
|
if (!pax_aslr_active(l))
|
|
return;
|
|
#ifdef PAX_ASLR_DEBUG
|
|
char buf[256];
|
|
|
|
if (pax_aslr_flags & PAX_ASLR_MMAP)
|
|
return;
|
|
|
|
if (pax_aslr_debug)
|
|
snprintb(buf, sizeof(buf), MAP_FMT, f);
|
|
else
|
|
buf[0] = '\0';
|
|
#endif
|
|
|
|
if (!(f & MAP_FIXED) && ((orig_addr == 0) || !(f & MAP_ANON))) {
|
|
PAX_DPRINTF("applying to %#jx orig_addr=%#jx f=%s",
|
|
(uintmax_t)*addr, (uintmax_t)orig_addr, buf);
|
|
if (!(l->l_proc->p_vmspace->vm_map.flags & VM_MAP_TOPDOWN))
|
|
*addr += l->l_proc->p_vmspace->vm_aslr_delta_mmap;
|
|
else
|
|
*addr -= l->l_proc->p_vmspace->vm_aslr_delta_mmap;
|
|
PAX_DPRINTF("result %#jx", (uintmax_t)*addr);
|
|
} else {
|
|
PAX_DPRINTF("not applying to %#jx orig_addr=%#jx f=%s",
|
|
(uintmax_t)*addr, (uintmax_t)orig_addr, buf);
|
|
}
|
|
}
|
|
|
|
static vaddr_t
|
|
pax_aslr_offset(vaddr_t align)
|
|
{
|
|
size_t pax_align, l2, delta;
|
|
uint32_t rand;
|
|
vaddr_t offset;
|
|
|
|
pax_align = align == 0 ? PAGE_SIZE : align;
|
|
l2 = ilog2(pax_align);
|
|
|
|
rand = cprng_fast32();
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_FIXED)
|
|
rand = pax_aslr_rand;
|
|
#endif
|
|
|
|
#define PAX_TRUNC(a, b) ((a) & ~((b) - 1))
|
|
|
|
delta = PAX_ASLR_DELTA(rand, l2, PAX_ASLR_DELTA_EXEC_LEN);
|
|
offset = PAX_TRUNC(delta, pax_align);
|
|
offset = MAX(offset, pax_align);
|
|
|
|
PAX_DPRINTF("rand=%#x l2=%#zx pax_align=%#zx delta=%#zx offset=%#jx",
|
|
rand, l2, pax_align, delta, (uintmax_t)offset);
|
|
|
|
return offset;
|
|
}
|
|
|
|
vaddr_t
|
|
pax_aslr_exec_offset(struct exec_package *epp, vaddr_t align)
|
|
{
|
|
if (!pax_aslr_epp_active(epp))
|
|
goto out;
|
|
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_EXEC_OFFSET)
|
|
goto out;
|
|
#endif
|
|
return pax_aslr_offset(align);
|
|
out:
|
|
return 0;
|
|
}
|
|
|
|
voff_t
|
|
pax_aslr_rtld_offset(struct exec_package *epp, vaddr_t align, int use_topdown)
|
|
{
|
|
voff_t offset;
|
|
|
|
if (!pax_aslr_epp_active(epp))
|
|
return 0;
|
|
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_RTLD_OFFSET)
|
|
return 0;
|
|
#endif
|
|
offset = pax_aslr_offset(align);
|
|
if (use_topdown)
|
|
offset = -offset;
|
|
|
|
return offset;
|
|
}
|
|
|
|
void
|
|
pax_aslr_stack(struct exec_package *epp, vsize_t *max_stack_size)
|
|
{
|
|
if (!pax_aslr_epp_active(epp))
|
|
return;
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_STACK)
|
|
return;
|
|
#endif
|
|
|
|
uint32_t len = (epp->ep_flags & EXEC_32) ?
|
|
PAX_ASLR_DELTA_STACK_LEN32 : PAX_ASLR_DELTA_STACK_LEN;
|
|
uint32_t rand = cprng_fast32();
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_FIXED)
|
|
rand = pax_aslr_rand;
|
|
#endif
|
|
u_long d = PAX_ASLR_DELTA(rand, PAX_ASLR_DELTA_STACK_LSB, len);
|
|
d &= (*max_stack_size / PAX_ASLR_MAX_STACK_WASTE) - 1;
|
|
u_long newminsaddr = (u_long)STACK_GROW(epp->ep_minsaddr, d);
|
|
PAX_DPRINTF("old minsaddr=%#jx delta=%#lx new minsaddr=%#lx",
|
|
(uintmax_t)epp->ep_minsaddr, d, newminsaddr);
|
|
epp->ep_minsaddr = (vaddr_t)newminsaddr;
|
|
*max_stack_size -= d;
|
|
}
|
|
|
|
uint32_t
|
|
pax_aslr_stack_gap(struct exec_package *epp)
|
|
{
|
|
if (!pax_aslr_epp_active(epp))
|
|
return 0;
|
|
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_STACK_GAP)
|
|
return 0;
|
|
#endif
|
|
|
|
uint32_t rand = cprng_fast32();
|
|
#ifdef PAX_ASLR_DEBUG
|
|
if (pax_aslr_flags & PAX_ASLR_FIXED)
|
|
rand = pax_aslr_rand;
|
|
#endif
|
|
rand %= PAGE_SIZE;
|
|
PAX_DPRINTF("stack gap=%#x\n", rand);
|
|
return rand;
|
|
}
|
|
#endif /* PAX_ASLR */
|
|
|
|
#ifdef PAX_SEGVGUARD
|
|
static bool
|
|
pax_segvguard_elf_flags_active(uint32_t flags)
|
|
{
|
|
if (!pax_segvguard_enabled)
|
|
return false;
|
|
if (pax_segvguard_global && (flags & ELF_NOTE_PAX_NOGUARD) != 0) {
|
|
/* Segvguard explicitly disabled */
|
|
return false;
|
|
}
|
|
if (!pax_segvguard_global && (flags & ELF_NOTE_PAX_GUARD) == 0) {
|
|
/* Segvguard not requested */
|
|
return false;
|
|
}
|
|
return true;
|
|
}
|
|
|
|
static void
|
|
pax_segvguard_cleanup_cb(void *v)
|
|
{
|
|
struct pax_segvguard_entry *p = v;
|
|
struct pax_segvguard_uid_entry *up;
|
|
|
|
if (p == NULL) {
|
|
return;
|
|
}
|
|
while ((up = LIST_FIRST(&p->segv_uids)) != NULL) {
|
|
LIST_REMOVE(up, sue_list);
|
|
kmem_free(up, sizeof(*up));
|
|
}
|
|
kmem_free(p, sizeof(*p));
|
|
}
|
|
|
|
/*
|
|
* Called when a process of image vp generated a segfault.
|
|
*/
|
|
int
|
|
pax_segvguard(struct lwp *l, struct vnode *vp, const char *name,
|
|
bool crashed)
|
|
{
|
|
struct pax_segvguard_entry *p;
|
|
struct pax_segvguard_uid_entry *up;
|
|
struct timeval tv;
|
|
uid_t uid;
|
|
uint32_t flags;
|
|
bool have_uid;
|
|
|
|
flags = l->l_proc->p_pax;
|
|
if (!pax_flags_active(flags, P_PAX_GUARD))
|
|
return 0;
|
|
|
|
if (vp == NULL)
|
|
return EFAULT;
|
|
|
|
/* Check if we already monitor the file. */
|
|
p = fileassoc_lookup(vp, segvguard_id);
|
|
|
|
/* Fast-path if starting a program we don't know. */
|
|
if (p == NULL && !crashed)
|
|
return 0;
|
|
|
|
microtime(&tv);
|
|
|
|
/*
|
|
* If a program we don't know crashed, we need to create a new entry
|
|
* for it.
|
|
*/
|
|
if (p == NULL) {
|
|
p = kmem_alloc(sizeof(*p), KM_SLEEP);
|
|
fileassoc_add(vp, segvguard_id, p);
|
|
LIST_INIT(&p->segv_uids);
|
|
|
|
/*
|
|
* Initialize a new entry with "crashes so far" of 1.
|
|
* The expiry time is when we purge the entry if it didn't
|
|
* reach the limit.
|
|
*/
|
|
up = kmem_alloc(sizeof(*up), KM_SLEEP);
|
|
up->sue_uid = kauth_cred_getuid(l->l_cred);
|
|
up->sue_ncrashes = 1;
|
|
up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
|
|
up->sue_suspended = 0;
|
|
LIST_INSERT_HEAD(&p->segv_uids, up, sue_list);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* A program we "know" either executed or crashed again.
|
|
* See if it's a culprit we're familiar with.
|
|
*/
|
|
uid = kauth_cred_getuid(l->l_cred);
|
|
have_uid = false;
|
|
LIST_FOREACH(up, &p->segv_uids, sue_list) {
|
|
if (up->sue_uid == uid) {
|
|
have_uid = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* It's someone else. Add an entry for him if we crashed.
|
|
*/
|
|
if (!have_uid) {
|
|
if (crashed) {
|
|
up = kmem_alloc(sizeof(*up), KM_SLEEP);
|
|
up->sue_uid = uid;
|
|
up->sue_ncrashes = 1;
|
|
up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
|
|
up->sue_suspended = 0;
|
|
LIST_INSERT_HEAD(&p->segv_uids, up, sue_list);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
if (crashed) {
|
|
/* Check if timer on previous crashes expired first. */
|
|
if (up->sue_expiry < tv.tv_sec) {
|
|
log(LOG_INFO, "PaX Segvguard: [%s] Suspension"
|
|
" expired.\n", name ? name : "unknown");
|
|
up->sue_ncrashes = 1;
|
|
up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
|
|
up->sue_suspended = 0;
|
|
return 0;
|
|
}
|
|
|
|
up->sue_ncrashes++;
|
|
|
|
if (up->sue_ncrashes >= pax_segvguard_maxcrashes) {
|
|
log(LOG_ALERT, "PaX Segvguard: [%s] Suspending "
|
|
"execution for %d seconds after %zu crashes.\n",
|
|
name ? name : "unknown", pax_segvguard_suspension,
|
|
up->sue_ncrashes);
|
|
|
|
/* Suspend this program for a while. */
|
|
up->sue_suspended = tv.tv_sec + pax_segvguard_suspension;
|
|
up->sue_ncrashes = 0;
|
|
up->sue_expiry = 0;
|
|
}
|
|
} else {
|
|
/* Are we supposed to be suspended? */
|
|
if (up->sue_suspended > tv.tv_sec) {
|
|
log(LOG_ALERT, "PaX Segvguard: [%s] Preventing "
|
|
"execution due to repeated segfaults.\n", name ?
|
|
name : "unknown");
|
|
return EPERM;
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
#endif /* PAX_SEGVGUARD */
|