1/* $NetBSD: kern_pax.c,v 1.57 2016/09/17 02:29:11 christos Exp $ */
2
3/*
4 * Copyright (c) 2015 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Maxime Villard.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32/*
33 * Copyright (c) 2006 Elad Efrat <elad@NetBSD.org>
34 * All rights reserved.
35 *
36 * Redistribution and use in source and binary forms, with or without
37 * modification, are permitted provided that the following conditions
38 * are met:
39 * 1. Redistributions of source code must retain the above copyright
40 * notice, this list of conditions and the following disclaimer.
41 * 2. Redistributions in binary form must reproduce the above copyright
42 * notice, this list of conditions and the following disclaimer in the
43 * documentation and/or other materials provided with the distribution.
44 * 3. The name of the author may not be used to endorse or promote products
45 * derived from this software without specific prior written permission.
46 *
47 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
48 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
49 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
50 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
51 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
52 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
53 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
54 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
55 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
56 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
57 */
58
59#include <sys/cdefs.h>
60__KERNEL_RCSID(0, "$NetBSD: kern_pax.c,v 1.57 2016/09/17 02:29:11 christos Exp $");
61
62#include "opt_pax.h"
63
64#include <sys/param.h>
65#include <sys/proc.h>
66#include <sys/exec.h>
67#include <sys/exec_elf.h>
68#include <sys/pax.h>
69#include <sys/sysctl.h>
70#include <sys/kmem.h>
71#include <sys/mman.h>
72#include <sys/fileassoc.h>
73#include <sys/syslog.h>
74#include <sys/vnode.h>
75#include <sys/queue.h>
76#include <sys/bitops.h>
77#include <sys/kauth.h>
78#include <sys/cprng.h>
79
80#ifdef PAX_ASLR_DEBUG
81#define PAX_DPRINTF(_fmt, args...) \
82 do if (pax_aslr_debug) uprintf("%s: " _fmt "\n", __func__, ##args); \
83 while (/*CONSTCOND*/0)
84#else
85#define PAX_DPRINTF(_fmt, args...) do {} while (/*CONSTCOND*/0)
86#endif
87
88#ifdef PAX_ASLR
89#include <sys/mman.h>
90
91int pax_aslr_enabled = 1;
92int pax_aslr_global = PAX_ASLR;
93
94#ifndef PAX_ASLR_DELTA_MMAP_LSB
95#define PAX_ASLR_DELTA_MMAP_LSB PGSHIFT
96#endif
97#ifndef PAX_ASLR_DELTA_MMAP_LEN
98#define PAX_ASLR_DELTA_MMAP_LEN ((sizeof(void *) * NBBY) / 2)
99#endif
100#ifndef PAX_ASLR_DELTA_MMAP_LEN32
101#define PAX_ASLR_DELTA_MMAP_LEN32 ((sizeof(uint32_t) * NBBY) / 2)
102#endif
103#ifndef PAX_ASLR_DELTA_STACK_LSB
104#define PAX_ASLR_DELTA_STACK_LSB PGSHIFT
105#endif
106#ifndef PAX_ASLR_DELTA_STACK_LEN
107#define PAX_ASLR_DELTA_STACK_LEN ((sizeof(void *) * NBBY) / 4)
108#endif
109#ifndef PAX_ASLR_DELTA_STACK_LEN32
110#define PAX_ASLR_DELTA_STACK_LEN32 ((sizeof(uint32_t) * NBBY) / 4)
111#endif
112#define PAX_ASLR_MAX_STACK_WASTE 8
113
114#ifdef PAX_ASLR_DEBUG
115int pax_aslr_debug;
116/* flag set means disable */
117int pax_aslr_flags;
118uint32_t pax_aslr_rand;
119#define PAX_ASLR_STACK 0x01
120#define PAX_ASLR_STACK_GAP 0x02
121#define PAX_ASLR_MMAP 0x04
122#define PAX_ASLR_EXEC_OFFSET 0x08
123#define PAX_ASLR_RTLD_OFFSET 0x10
124#define PAX_ASLR_FIXED 0x20
125#endif
126
127static bool pax_aslr_elf_flags_active(uint32_t);
128#endif /* PAX_ASLR */
129
130#ifdef PAX_MPROTECT
131static int pax_mprotect_enabled = 1;
132static int pax_mprotect_global = PAX_MPROTECT;
133static int pax_mprotect_ptrace = 1;
134static bool pax_mprotect_elf_flags_active(uint32_t);
135#endif /* PAX_MPROTECT */
136#ifdef PAX_MPROTECT_DEBUG
137int pax_mprotect_debug;
138#endif
139
140#ifdef PAX_SEGVGUARD
141#ifndef PAX_SEGVGUARD_EXPIRY
142#define PAX_SEGVGUARD_EXPIRY (2 * 60)
143#endif
144#ifndef PAX_SEGVGUARD_SUSPENSION
145#define PAX_SEGVGUARD_SUSPENSION (10 * 60)
146#endif
147#ifndef PAX_SEGVGUARD_MAXCRASHES
148#define PAX_SEGVGUARD_MAXCRASHES 5
149#endif
150
151
152static int pax_segvguard_enabled = 1;
153static int pax_segvguard_global = PAX_SEGVGUARD;
154static int pax_segvguard_expiry = PAX_SEGVGUARD_EXPIRY;
155static int pax_segvguard_suspension = PAX_SEGVGUARD_SUSPENSION;
156static int pax_segvguard_maxcrashes = PAX_SEGVGUARD_MAXCRASHES;
157
158static fileassoc_t segvguard_id;
159
160struct pax_segvguard_uid_entry {
161 uid_t sue_uid;
162 size_t sue_ncrashes;
163 time_t sue_expiry;
164 time_t sue_suspended;
165 LIST_ENTRY(pax_segvguard_uid_entry) sue_list;
166};
167
168struct pax_segvguard_entry {
169 LIST_HEAD(, pax_segvguard_uid_entry) segv_uids;
170};
171
172static bool pax_segvguard_elf_flags_active(uint32_t);
173static void pax_segvguard_cleanup_cb(void *);
174#endif /* PAX_SEGVGUARD */
175
176SYSCTL_SETUP(sysctl_security_pax_setup, "sysctl security.pax setup")
177{
178 const struct sysctlnode *rnode = NULL, *cnode;
179
180 sysctl_createv(clog, 0, NULL, &rnode,
181 CTLFLAG_PERMANENT,
182 CTLTYPE_NODE, "pax",
183 SYSCTL_DESCR("PaX (exploit mitigation) features."),
184 NULL, 0, NULL, 0,
185 CTL_SECURITY, CTL_CREATE, CTL_EOL);
186
187 cnode = rnode;
188
189#ifdef PAX_MPROTECT
190 rnode = cnode;
191 sysctl_createv(clog, 0, &rnode, &rnode,
192 CTLFLAG_PERMANENT,
193 CTLTYPE_NODE, "mprotect",
194 SYSCTL_DESCR("mprotect(2) W^X restrictions."),
195 NULL, 0, NULL, 0,
196 CTL_CREATE, CTL_EOL);
197 sysctl_createv(clog, 0, &rnode, NULL,
198 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
199 CTLTYPE_INT, "enabled",
200 SYSCTL_DESCR("Restrictions enabled."),
201 NULL, 0, &pax_mprotect_enabled, 0,
202 CTL_CREATE, CTL_EOL);
203 sysctl_createv(clog, 0, &rnode, NULL,
204 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
205 CTLTYPE_INT, "global",
206 SYSCTL_DESCR("When enabled, unless explicitly "
207 "specified, apply restrictions to "
208 "all processes."),
209 NULL, 0, &pax_mprotect_global, 0,
210 CTL_CREATE, CTL_EOL);
211 sysctl_createv(clog, 0, &rnode, NULL,
212 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
213 CTLTYPE_INT, "ptrace",
214 SYSCTL_DESCR("When enabled, allow ptrace(2) to "
215 "override mprotect permissions on traced "
216 "processes"),
217 NULL, 0, &pax_mprotect_ptrace, 0,
218 CTL_CREATE, CTL_EOL);
219#ifdef PAX_MPROTECT_DEBUG
220 sysctl_createv(clog, 0, &rnode, NULL,
221 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
222 CTLTYPE_INT, "debug",
223 SYSCTL_DESCR("print mprotect changes."),
224 NULL, 0, &pax_mprotect_debug, 0,
225 CTL_CREATE, CTL_EOL);
226#endif
227#endif /* PAX_MPROTECT */
228
229#ifdef PAX_SEGVGUARD
230 rnode = cnode;
231 sysctl_createv(clog, 0, &rnode, &rnode,
232 CTLFLAG_PERMANENT,
233 CTLTYPE_NODE, "segvguard",
234 SYSCTL_DESCR("PaX segvguard."),
235 NULL, 0, NULL, 0,
236 CTL_CREATE, CTL_EOL);
237 sysctl_createv(clog, 0, &rnode, NULL,
238 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
239 CTLTYPE_INT, "enabled",
240 SYSCTL_DESCR("segvguard enabled."),
241 NULL, 0, &pax_segvguard_enabled, 0,
242 CTL_CREATE, CTL_EOL);
243 sysctl_createv(clog, 0, &rnode, NULL,
244 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
245 CTLTYPE_INT, "global",
246 SYSCTL_DESCR("segvguard all programs."),
247 NULL, 0, &pax_segvguard_global, 0,
248 CTL_CREATE, CTL_EOL);
249 sysctl_createv(clog, 0, &rnode, NULL,
250 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
251 CTLTYPE_INT, "expiry_timeout",
252 SYSCTL_DESCR("Entry expiry timeout (in seconds)."),
253 NULL, 0, &pax_segvguard_expiry, 0,
254 CTL_CREATE, CTL_EOL);
255 sysctl_createv(clog, 0, &rnode, NULL,
256 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
257 CTLTYPE_INT, "suspend_timeout",
258 SYSCTL_DESCR("Entry suspension timeout (in seconds)."),
259 NULL, 0, &pax_segvguard_suspension, 0,
260 CTL_CREATE, CTL_EOL);
261 sysctl_createv(clog, 0, &rnode, NULL,
262 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
263 CTLTYPE_INT, "max_crashes",
264 SYSCTL_DESCR("Max number of crashes before expiry."),
265 NULL, 0, &pax_segvguard_maxcrashes, 0,
266 CTL_CREATE, CTL_EOL);
267#endif /* PAX_SEGVGUARD */
268
269#ifdef PAX_ASLR
270 rnode = cnode;
271 sysctl_createv(clog, 0, &rnode, &rnode,
272 CTLFLAG_PERMANENT,
273 CTLTYPE_NODE, "aslr",
274 SYSCTL_DESCR("Address Space Layout Randomization."),
275 NULL, 0, NULL, 0,
276 CTL_CREATE, CTL_EOL);
277 sysctl_createv(clog, 0, &rnode, NULL,
278 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
279 CTLTYPE_INT, "enabled",
280 SYSCTL_DESCR("Restrictions enabled."),
281 NULL, 0, &pax_aslr_enabled, 0,
282 CTL_CREATE, CTL_EOL);
283 sysctl_createv(clog, 0, &rnode, NULL,
284 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
285 CTLTYPE_INT, "global",
286 SYSCTL_DESCR("When enabled, unless explicitly "
287 "specified, apply to all processes."),
288 NULL, 0, &pax_aslr_global, 0,
289 CTL_CREATE, CTL_EOL);
290#ifdef PAX_ASLR_DEBUG
291 sysctl_createv(clog, 0, &rnode, NULL,
292 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
293 CTLTYPE_INT, "debug",
294 SYSCTL_DESCR("Pring ASLR selected addresses."),
295 NULL, 0, &pax_aslr_debug, 0,
296 CTL_CREATE, CTL_EOL);
297 sysctl_createv(clog, 0, &rnode, NULL,
298 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
299 CTLTYPE_INT, "flags",
300 SYSCTL_DESCR("Disable/Enable select ASLR features."),
301 NULL, 0, &pax_aslr_flags, 0,
302 CTL_CREATE, CTL_EOL);
303 sysctl_createv(clog, 0, &rnode, NULL,
304 CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
305 CTLTYPE_INT, "rand",
306 SYSCTL_DESCR("Use the given fixed random value"),
307 NULL, 0, &pax_aslr_rand, 0,
308 CTL_CREATE, CTL_EOL);
309#endif
310 sysctl_createv(clog, 0, &rnode, NULL,
311 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE,
312 CTLTYPE_INT, "mmap_len",
313 SYSCTL_DESCR("Number of bits randomized for "
314 "mmap(2) calls."),
315 NULL, PAX_ASLR_DELTA_MMAP_LEN, NULL, 0,
316 CTL_CREATE, CTL_EOL);
317 sysctl_createv(clog, 0, &rnode, NULL,
318 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE,
319 CTLTYPE_INT, "stack_len",
320 SYSCTL_DESCR("Number of bits randomized for "
321 "the stack."),
322 NULL, PAX_ASLR_DELTA_STACK_LEN, NULL, 0,
323 CTL_CREATE, CTL_EOL);
324 sysctl_createv(clog, 0, &rnode, NULL,
325 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE,
326 CTLTYPE_INT, "exec_len",
327 SYSCTL_DESCR("Number of bits randomized for "
328 "the PIE exec base."),
329 NULL, PAX_ASLR_DELTA_EXEC_LEN, NULL, 0,
330 CTL_CREATE, CTL_EOL);
331
332#endif /* PAX_ASLR */
333}
334
335/*
336 * Initialize PaX.
337 */
338void
339pax_init(void)
340{
341#ifdef PAX_SEGVGUARD
342 int error;
343
344 error = fileassoc_register("segvguard", pax_segvguard_cleanup_cb,
345 &segvguard_id);
346 if (error) {
347 panic("pax_init: segvguard_id: error=%d\n", error);
348 }
349#endif /* PAX_SEGVGUARD */
350#ifdef PAX_ASLR
351 /* Adjust maximum stack by the size we can consume for ASLR */
352 extern rlim_t maxsmap;
353 maxsmap = MAXSSIZ - (MAXSSIZ / PAX_ASLR_MAX_STACK_WASTE);
354 // XXX: compat32 is not handled.
355#endif
356}
357
358void
359pax_set_flags(struct exec_package *epp, struct proc *p)
360{
361 p->p_pax = epp->ep_pax_flags;
362
363#ifdef PAX_MPROTECT
364 if (pax_mprotect_ptrace == 0)
365 return;
366 /*
367 * If we are running under the debugger, turn off MPROTECT so
368 * the debugger can insert/delete breakpoints
369 */
370 if (p->p_slflag & PSL_TRACED)
371 p->p_pax &= ~P_PAX_MPROTECT;
372#endif
373}
374
375void
376pax_setup_elf_flags(struct exec_package *epp, uint32_t elf_flags)
377{
378 uint32_t flags = 0;
379
380#ifdef PAX_ASLR
381 if (pax_aslr_elf_flags_active(elf_flags)) {
382 flags |= P_PAX_ASLR;
383 }
384#endif
385#ifdef PAX_MPROTECT
386 if (pax_mprotect_elf_flags_active(elf_flags)) {
387 flags |= P_PAX_MPROTECT;
388 }
389#endif
390#ifdef PAX_SEGVGUARD
391 if (pax_segvguard_elf_flags_active(elf_flags)) {
392 flags |= P_PAX_GUARD;
393 }
394#endif
395
396 epp->ep_pax_flags = flags;
397}
398
399#if defined(PAX_MPROTECT) || defined(PAX_SEGVGUARD) || defined(PAX_ASLR)
400static inline bool
401pax_flags_active(uint32_t flags, uint32_t opt)
402{
403 if (!(flags & opt))
404 return false;
405 return true;
406}
407#endif /* PAX_MPROTECT || PAX_SEGVGUARD || PAX_ASLR */
408
409#ifdef PAX_MPROTECT
410static bool
411pax_mprotect_elf_flags_active(uint32_t flags)
412{
413 if (!pax_mprotect_enabled)
414 return false;
415 if (pax_mprotect_global && (flags & ELF_NOTE_PAX_NOMPROTECT) != 0) {
416 /* Mprotect explicitly disabled */
417 return false;
418 }
419 if (!pax_mprotect_global && (flags & ELF_NOTE_PAX_MPROTECT) == 0) {
420 /* Mprotect not requested */
421 return false;
422 }
423 return true;
424}
425
426void
427pax_mprotect_adjust(
428#ifdef PAX_MPROTECT_DEBUG
429 const char *file, size_t line,
430#endif
431 struct lwp *l, vm_prot_t *prot, vm_prot_t *maxprot)
432{
433 uint32_t flags;
434
435 flags = l->l_proc->p_pax;
436 if (!pax_flags_active(flags, P_PAX_MPROTECT))
437 return;
438
439 if ((*prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) != VM_PROT_EXECUTE) {
440#ifdef PAX_MPROTECT_DEBUG
441 struct proc *p = l->l_proc;
442 if ((*prot & VM_PROT_EXECUTE) && pax_mprotect_debug) {
443 printf("%s: %s,%zu: %d.%d (%s): -x\n",
444 __func__, file, line,
445 p->p_pid, l->l_lid, p->p_comm);
446 }
447#endif
448 *prot &= ~VM_PROT_EXECUTE;
449 *maxprot &= ~VM_PROT_EXECUTE;
450 } else {
451#ifdef PAX_MPROTECT_DEBUG
452 struct proc *p = l->l_proc;
453 if ((*prot & VM_PROT_WRITE) && pax_mprotect_debug) {
454 printf("%s: %s,%zu: %d.%d (%s): -w\n",
455 __func__, file, line,
456 p->p_pid, l->l_lid, p->p_comm);
457 }
458#endif
459 *prot &= ~VM_PROT_WRITE;
460 *maxprot &= ~VM_PROT_WRITE;
461 }
462}
463
464/*
465 * Bypass MPROTECT for traced processes
466 */
467int
468pax_mprotect_prot(struct lwp *l)
469{
470 uint32_t flags;
471
472 flags = l->l_proc->p_pax;
473 if (!pax_flags_active(flags, P_PAX_MPROTECT))
474 return 0;
475 if (pax_mprotect_ptrace < 2)
476 return 0;
477 return UVM_EXTRACT_PROT_ALL;
478}
479
480
481#endif /* PAX_MPROTECT */
482
483#ifdef PAX_ASLR
484static bool
485pax_aslr_elf_flags_active(uint32_t flags)
486{
487 if (!pax_aslr_enabled)
488 return false;
489 if (pax_aslr_global && (flags & ELF_NOTE_PAX_NOASLR) != 0) {
490 /* ASLR explicitly disabled */
491 return false;
492 }
493 if (!pax_aslr_global && (flags & ELF_NOTE_PAX_ASLR) == 0) {
494 /* ASLR not requested */
495 return false;
496 }
497 return true;
498}
499
500static bool
501pax_aslr_epp_active(struct exec_package *epp)
502{
503 if (__predict_false((epp->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0))
504 return false;
505 return pax_flags_active(epp->ep_pax_flags, P_PAX_ASLR);
506}
507
508static bool
509pax_aslr_active(struct lwp *l)
510{
511 return pax_flags_active(l->l_proc->p_pax, P_PAX_ASLR);
512}
513
514void
515pax_aslr_init_vm(struct lwp *l, struct vmspace *vm, struct exec_package *ep)
516{
517 if (!pax_aslr_active(l))
518 return;
519
520 if (__predict_false((ep->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0))
521 return;
522
523#ifdef PAX_ASLR_DEBUG
524 if (pax_aslr_flags & PAX_ASLR_MMAP)
525 return;
526#endif
527
528 uint32_t len = (ep->ep_flags & EXEC_32) ?
529 PAX_ASLR_DELTA_MMAP_LEN32 : PAX_ASLR_DELTA_MMAP_LEN;
530
531 uint32_t rand = cprng_fast32();
532#ifdef PAX_ASLR_DEBUG
533 if (pax_aslr_flags & PAX_ASLR_FIXED)
534 rand = pax_aslr_rand;
535#endif
536 vm->vm_aslr_delta_mmap = PAX_ASLR_DELTA(rand,
537 PAX_ASLR_DELTA_MMAP_LSB, len);
538
539 PAX_DPRINTF("delta_mmap=%#jx/%u",
540 (uintmax_t)vm->vm_aslr_delta_mmap, len);
541}
542
543void
544pax_aslr_mmap(struct lwp *l, vaddr_t *addr, vaddr_t orig_addr, int f)
545{
546 if (!pax_aslr_active(l))
547 return;
548#ifdef PAX_ASLR_DEBUG
549 char buf[256];
550
551 if (pax_aslr_flags & PAX_ASLR_MMAP)
552 return;
553
554 if (pax_aslr_debug)
555 snprintb(buf, sizeof(buf), MAP_FMT, f);
556 else
557 buf[0] = '\0';
558#endif
559
560 if (!(f & MAP_FIXED) && ((orig_addr == 0) || !(f & MAP_ANON))) {
561 PAX_DPRINTF("applying to %#jx orig_addr=%#jx f=%s",
562 (uintmax_t)*addr, (uintmax_t)orig_addr, buf);
563 if (!(l->l_proc->p_vmspace->vm_map.flags & VM_MAP_TOPDOWN))
564 *addr += l->l_proc->p_vmspace->vm_aslr_delta_mmap;
565 else
566 *addr -= l->l_proc->p_vmspace->vm_aslr_delta_mmap;
567 PAX_DPRINTF("result %#jx", (uintmax_t)*addr);
568 } else {
569 PAX_DPRINTF("not applying to %#jx orig_addr=%#jx f=%s",
570 (uintmax_t)*addr, (uintmax_t)orig_addr, buf);
571 }
572}
573
574static vaddr_t
575pax_aslr_offset(vaddr_t align)
576{
577 size_t pax_align, l2, delta;
578 uint32_t rand;
579 vaddr_t offset;
580
581 pax_align = align == 0 ? PGSHIFT : align;
582 l2 = ilog2(pax_align);
583
584 rand = cprng_fast32();
585#ifdef PAX_ASLR_DEBUG
586 if (pax_aslr_flags & PAX_ASLR_FIXED)
587 rand = pax_aslr_rand;
588#endif
589
590#define PAX_TRUNC(a, b) ((a) & ~((b) - 1))
591
592 delta = PAX_ASLR_DELTA(rand, l2, PAX_ASLR_DELTA_EXEC_LEN);
593 offset = PAX_TRUNC(delta, pax_align) + PAGE_SIZE;
594
595 PAX_DPRINTF("rand=%#x l2=%#zx pax_align=%#zx delta=%#zx offset=%#jx",
596 rand, l2, pax_align, delta, (uintmax_t)offset);
597
598 return offset;
599}
600
601vaddr_t
602pax_aslr_exec_offset(struct exec_package *epp, vaddr_t align)
603{
604 if (!pax_aslr_epp_active(epp))
605 goto out;
606
607#ifdef PAX_ASLR_DEBUG
608 if (pax_aslr_flags & PAX_ASLR_EXEC_OFFSET)
609 goto out;
610#endif
611 return pax_aslr_offset(align) + PAGE_SIZE;
612out:
613 return MAX(align, PAGE_SIZE);
614}
615
616voff_t
617pax_aslr_rtld_offset(struct exec_package *epp, vaddr_t align, int use_topdown)
618{
619 voff_t offset;
620
621 if (!pax_aslr_epp_active(epp))
622 return 0;
623
624#ifdef PAX_ASLR_DEBUG
625 if (pax_aslr_flags & PAX_ASLR_RTLD_OFFSET)
626 return 0;
627#endif
628 offset = pax_aslr_offset(align);
629 if (use_topdown)
630 offset = -offset;
631
632 return offset;
633}
634
635void
636pax_aslr_stack(struct exec_package *epp, vsize_t *max_stack_size)
637{
638 if (!pax_aslr_epp_active(epp))
639 return;
640#ifdef PAX_ASLR_DEBUG
641 if (pax_aslr_flags & PAX_ASLR_STACK)
642 return;
643#endif
644
645 uint32_t len = (epp->ep_flags & EXEC_32) ?
646 PAX_ASLR_DELTA_STACK_LEN32 : PAX_ASLR_DELTA_STACK_LEN;
647 uint32_t rand = cprng_fast32();
648#ifdef PAX_ASLR_DEBUG
649 if (pax_aslr_flags & PAX_ASLR_FIXED)
650 rand = pax_aslr_rand;
651#endif
652 u_long d = PAX_ASLR_DELTA(rand, PAX_ASLR_DELTA_STACK_LSB, len);
653 d &= (*max_stack_size / PAX_ASLR_MAX_STACK_WASTE) - 1;
654 u_long newminsaddr = (u_long)STACK_GROW(epp->ep_minsaddr, d);
655 PAX_DPRINTF("old minsaddr=%#jx delta=%#lx new minsaddr=%#lx",
656 (uintmax_t)epp->ep_minsaddr, d, newminsaddr);
657 epp->ep_minsaddr = (vaddr_t)newminsaddr;
658 *max_stack_size -= d;
659}
660
661uint32_t
662pax_aslr_stack_gap(struct exec_package *epp)
663{
664 if (!pax_aslr_epp_active(epp))
665 return 0;
666
667#ifdef PAX_ASLR_DEBUG
668 if (pax_aslr_flags & PAX_ASLR_STACK_GAP)
669 return 0;
670#endif
671
672 uint32_t rand = cprng_fast32();
673#ifdef PAX_ASLR_DEBUG
674 if (pax_aslr_flags & PAX_ASLR_FIXED)
675 rand = pax_aslr_rand;
676#endif
677 rand %= PAGE_SIZE;
678 PAX_DPRINTF("stack gap=%#x\n", rand);
679 return rand;
680}
681#endif /* PAX_ASLR */
682
683#ifdef PAX_SEGVGUARD
684static bool
685pax_segvguard_elf_flags_active(uint32_t flags)
686{
687 if (!pax_segvguard_enabled)
688 return false;
689 if (pax_segvguard_global && (flags & ELF_NOTE_PAX_NOGUARD) != 0) {
690 /* Segvguard explicitly disabled */
691 return false;
692 }
693 if (!pax_segvguard_global && (flags & ELF_NOTE_PAX_GUARD) == 0) {
694 /* Segvguard not requested */
695 return false;
696 }
697 return true;
698}
699
700static void
701pax_segvguard_cleanup_cb(void *v)
702{
703 struct pax_segvguard_entry *p = v;
704 struct pax_segvguard_uid_entry *up;
705
706 if (p == NULL) {
707 return;
708 }
709 while ((up = LIST_FIRST(&p->segv_uids)) != NULL) {
710 LIST_REMOVE(up, sue_list);
711 kmem_free(up, sizeof(*up));
712 }
713 kmem_free(p, sizeof(*p));
714}
715
716/*
717 * Called when a process of image vp generated a segfault.
718 */
719int
720pax_segvguard(struct lwp *l, struct vnode *vp, const char *name,
721 bool crashed)
722{
723 struct pax_segvguard_entry *p;
724 struct pax_segvguard_uid_entry *up;
725 struct timeval tv;
726 uid_t uid;
727 uint32_t flags;
728 bool have_uid;
729
730 flags = l->l_proc->p_pax;
731 if (!pax_flags_active(flags, P_PAX_GUARD))
732 return 0;
733
734 if (vp == NULL)
735 return EFAULT;
736
737 /* Check if we already monitor the file. */
738 p = fileassoc_lookup(vp, segvguard_id);
739
740 /* Fast-path if starting a program we don't know. */
741 if (p == NULL && !crashed)
742 return 0;
743
744 microtime(&tv);
745
746 /*
747 * If a program we don't know crashed, we need to create a new entry
748 * for it.
749 */
750 if (p == NULL) {
751 p = kmem_alloc(sizeof(*p), KM_SLEEP);
752 fileassoc_add(vp, segvguard_id, p);
753 LIST_INIT(&p->segv_uids);
754
755 /*
756 * Initialize a new entry with "crashes so far" of 1.
757 * The expiry time is when we purge the entry if it didn't
758 * reach the limit.
759 */
760 up = kmem_alloc(sizeof(*up), KM_SLEEP);
761 up->sue_uid = kauth_cred_getuid(l->l_cred);
762 up->sue_ncrashes = 1;
763 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
764 up->sue_suspended = 0;
765 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list);
766 return 0;
767 }
768
769 /*
770 * A program we "know" either executed or crashed again.
771 * See if it's a culprit we're familiar with.
772 */
773 uid = kauth_cred_getuid(l->l_cred);
774 have_uid = false;
775 LIST_FOREACH(up, &p->segv_uids, sue_list) {
776 if (up->sue_uid == uid) {
777 have_uid = true;
778 break;
779 }
780 }
781
782 /*
783 * It's someone else. Add an entry for him if we crashed.
784 */
785 if (!have_uid) {
786 if (crashed) {
787 up = kmem_alloc(sizeof(*up), KM_SLEEP);
788 up->sue_uid = uid;
789 up->sue_ncrashes = 1;
790 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
791 up->sue_suspended = 0;
792 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list);
793 }
794 return 0;
795 }
796
797 if (crashed) {
798 /* Check if timer on previous crashes expired first. */
799 if (up->sue_expiry < tv.tv_sec) {
800 log(LOG_INFO, "PaX Segvguard: [%s] Suspension"
801 " expired.\n", name ? name : "unknown");
802 up->sue_ncrashes = 1;
803 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry;
804 up->sue_suspended = 0;
805 return 0;
806 }
807
808 up->sue_ncrashes++;
809
810 if (up->sue_ncrashes >= pax_segvguard_maxcrashes) {
811 log(LOG_ALERT, "PaX Segvguard: [%s] Suspending "
812 "execution for %d seconds after %zu crashes.\n",
813 name ? name : "unknown", pax_segvguard_suspension,
814 up->sue_ncrashes);
815
816 /* Suspend this program for a while. */
817 up->sue_suspended = tv.tv_sec + pax_segvguard_suspension;
818 up->sue_ncrashes = 0;
819 up->sue_expiry = 0;
820 }
821 } else {
822 /* Are we supposed to be suspended? */
823 if (up->sue_suspended > tv.tv_sec) {
824 log(LOG_ALERT, "PaX Segvguard: [%s] Preventing "
825 "execution due to repeated segfaults.\n", name ?
826 name : "unknown");
827 return EPERM;
828 }
829 }
830
831 return 0;
832}
833#endif /* PAX_SEGVGUARD */
834