kern_pax.c revision 1.44
1 /* $NetBSD: kern_pax.c,v 1.44 2016/05/13 17:33:43 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 (at) 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 1.44 2016/05/13 17:33:43 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 91 int pax_aslr_enabled = 1; 92 int 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 static bool pax_aslr_elf_flags_active(uint32_t); 115 #endif /* PAX_ASLR */ 116 117 #ifdef PAX_MPROTECT 118 static int pax_mprotect_enabled = 1; 119 static int pax_mprotect_global = PAX_MPROTECT; 120 static bool pax_mprotect_elf_flags_active(uint32_t); 121 #endif /* PAX_MPROTECT */ 122 #ifdef PAX_MPROTECT_DEBUG 123 int pax_mprotect_debug; 124 #endif 125 126 #ifdef PAX_SEGVGUARD 127 #ifndef PAX_SEGVGUARD_EXPIRY 128 #define PAX_SEGVGUARD_EXPIRY (2 * 60) 129 #endif 130 #ifndef PAX_SEGVGUARD_SUSPENSION 131 #define PAX_SEGVGUARD_SUSPENSION (10 * 60) 132 #endif 133 #ifndef PAX_SEGVGUARD_MAXCRASHES 134 #define PAX_SEGVGUARD_MAXCRASHES 5 135 #endif 136 137 #ifdef PAX_ASLR_DEBUG 138 int pax_aslr_debug; 139 /* flag set means disable */ 140 int pax_aslr_flags; 141 uint32_t pax_aslr_rand; 142 #define PAX_ASLR_STACK 0x01 143 #define PAX_ASLR_STACK_GAP 0x02 144 #define PAX_ASLR_MMAP 0x04 145 #define PAX_ASLR_EXEC_OFFSET 0x08 146 #define PAX_ASLR_FIXED 0x10 147 #endif 148 149 static int pax_segvguard_enabled = 1; 150 static int pax_segvguard_global = PAX_SEGVGUARD; 151 static int pax_segvguard_expiry = PAX_SEGVGUARD_EXPIRY; 152 static int pax_segvguard_suspension = PAX_SEGVGUARD_SUSPENSION; 153 static int pax_segvguard_maxcrashes = PAX_SEGVGUARD_MAXCRASHES; 154 155 static fileassoc_t segvguard_id; 156 157 struct pax_segvguard_uid_entry { 158 uid_t sue_uid; 159 size_t sue_ncrashes; 160 time_t sue_expiry; 161 time_t sue_suspended; 162 LIST_ENTRY(pax_segvguard_uid_entry) sue_list; 163 }; 164 165 struct pax_segvguard_entry { 166 LIST_HEAD(, pax_segvguard_uid_entry) segv_uids; 167 }; 168 169 static bool pax_segvguard_elf_flags_active(uint32_t); 170 static void pax_segvguard_cleanup_cb(void *); 171 #endif /* PAX_SEGVGUARD */ 172 173 SYSCTL_SETUP(sysctl_security_pax_setup, "sysctl security.pax setup") 174 { 175 const struct sysctlnode *rnode = NULL, *cnode; 176 177 sysctl_createv(clog, 0, NULL, &rnode, 178 CTLFLAG_PERMANENT, 179 CTLTYPE_NODE, "pax", 180 SYSCTL_DESCR("PaX (exploit mitigation) features."), 181 NULL, 0, NULL, 0, 182 CTL_SECURITY, CTL_CREATE, CTL_EOL); 183 184 cnode = rnode; 185 186 #ifdef PAX_MPROTECT 187 rnode = cnode; 188 sysctl_createv(clog, 0, &rnode, &rnode, 189 CTLFLAG_PERMANENT, 190 CTLTYPE_NODE, "mprotect", 191 SYSCTL_DESCR("mprotect(2) W^X restrictions."), 192 NULL, 0, NULL, 0, 193 CTL_CREATE, CTL_EOL); 194 sysctl_createv(clog, 0, &rnode, NULL, 195 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 196 CTLTYPE_INT, "enabled", 197 SYSCTL_DESCR("Restrictions enabled."), 198 NULL, 0, &pax_mprotect_enabled, 0, 199 CTL_CREATE, CTL_EOL); 200 sysctl_createv(clog, 0, &rnode, NULL, 201 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 202 CTLTYPE_INT, "global", 203 SYSCTL_DESCR("When enabled, unless explicitly " 204 "specified, apply restrictions to " 205 "all processes."), 206 NULL, 0, &pax_mprotect_global, 0, 207 CTL_CREATE, CTL_EOL); 208 #ifdef PAX_MPROTECT_DEBUG 209 sysctl_createv(clog, 0, &rnode, NULL, 210 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 211 CTLTYPE_INT, "debug", 212 SYSCTL_DESCR("print mprotect changes."), 213 NULL, 0, &pax_mprotect_debug, 0, 214 CTL_CREATE, CTL_EOL); 215 #endif 216 #endif /* PAX_MPROTECT */ 217 218 #ifdef PAX_SEGVGUARD 219 rnode = cnode; 220 sysctl_createv(clog, 0, &rnode, &rnode, 221 CTLFLAG_PERMANENT, 222 CTLTYPE_NODE, "segvguard", 223 SYSCTL_DESCR("PaX segvguard."), 224 NULL, 0, NULL, 0, 225 CTL_CREATE, CTL_EOL); 226 sysctl_createv(clog, 0, &rnode, NULL, 227 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 228 CTLTYPE_INT, "enabled", 229 SYSCTL_DESCR("segvguard enabled."), 230 NULL, 0, &pax_segvguard_enabled, 0, 231 CTL_CREATE, CTL_EOL); 232 sysctl_createv(clog, 0, &rnode, NULL, 233 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 234 CTLTYPE_INT, "global", 235 SYSCTL_DESCR("segvguard all programs."), 236 NULL, 0, &pax_segvguard_global, 0, 237 CTL_CREATE, CTL_EOL); 238 sysctl_createv(clog, 0, &rnode, NULL, 239 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 240 CTLTYPE_INT, "expiry_timeout", 241 SYSCTL_DESCR("Entry expiry timeout (in seconds)."), 242 NULL, 0, &pax_segvguard_expiry, 0, 243 CTL_CREATE, CTL_EOL); 244 sysctl_createv(clog, 0, &rnode, NULL, 245 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 246 CTLTYPE_INT, "suspend_timeout", 247 SYSCTL_DESCR("Entry suspension timeout (in seconds)."), 248 NULL, 0, &pax_segvguard_suspension, 0, 249 CTL_CREATE, CTL_EOL); 250 sysctl_createv(clog, 0, &rnode, NULL, 251 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 252 CTLTYPE_INT, "max_crashes", 253 SYSCTL_DESCR("Max number of crashes before expiry."), 254 NULL, 0, &pax_segvguard_maxcrashes, 0, 255 CTL_CREATE, CTL_EOL); 256 #endif /* PAX_SEGVGUARD */ 257 258 #ifdef PAX_ASLR 259 rnode = cnode; 260 sysctl_createv(clog, 0, &rnode, &rnode, 261 CTLFLAG_PERMANENT, 262 CTLTYPE_NODE, "aslr", 263 SYSCTL_DESCR("Address Space Layout Randomization."), 264 NULL, 0, NULL, 0, 265 CTL_CREATE, CTL_EOL); 266 sysctl_createv(clog, 0, &rnode, NULL, 267 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 268 CTLTYPE_INT, "enabled", 269 SYSCTL_DESCR("Restrictions enabled."), 270 NULL, 0, &pax_aslr_enabled, 0, 271 CTL_CREATE, CTL_EOL); 272 sysctl_createv(clog, 0, &rnode, NULL, 273 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 274 CTLTYPE_INT, "global", 275 SYSCTL_DESCR("When enabled, unless explicitly " 276 "specified, apply to all processes."), 277 NULL, 0, &pax_aslr_global, 0, 278 CTL_CREATE, CTL_EOL); 279 #ifdef PAX_ASLR_DEBUG 280 sysctl_createv(clog, 0, &rnode, NULL, 281 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 282 CTLTYPE_INT, "debug", 283 SYSCTL_DESCR("Pring ASLR selected addresses."), 284 NULL, 0, &pax_aslr_debug, 0, 285 CTL_CREATE, CTL_EOL); 286 sysctl_createv(clog, 0, &rnode, NULL, 287 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 288 CTLTYPE_INT, "flags", 289 SYSCTL_DESCR("Disable/Enable select ASLR features."), 290 NULL, 0, &pax_aslr_flags, 0, 291 CTL_CREATE, CTL_EOL); 292 sysctl_createv(clog, 0, &rnode, NULL, 293 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 294 CTLTYPE_INT, "rand", 295 SYSCTL_DESCR("Use the given fixed random value"), 296 NULL, 0, &pax_aslr_rand, 0, 297 CTL_CREATE, CTL_EOL); 298 #endif 299 sysctl_createv(clog, 0, &rnode, NULL, 300 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 301 CTLTYPE_INT, "mmap_len", 302 SYSCTL_DESCR("Number of bits randomized for " 303 "mmap(2) calls."), 304 NULL, PAX_ASLR_DELTA_MMAP_LEN, NULL, 0, 305 CTL_CREATE, CTL_EOL); 306 sysctl_createv(clog, 0, &rnode, NULL, 307 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 308 CTLTYPE_INT, "stack_len", 309 SYSCTL_DESCR("Number of bits randomized for " 310 "the stack."), 311 NULL, PAX_ASLR_DELTA_STACK_LEN, NULL, 0, 312 CTL_CREATE, CTL_EOL); 313 sysctl_createv(clog, 0, &rnode, NULL, 314 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 315 CTLTYPE_INT, "exec_len", 316 SYSCTL_DESCR("Number of bits randomized for " 317 "the PIE exec base."), 318 NULL, PAX_ASLR_DELTA_EXEC_LEN, NULL, 0, 319 CTL_CREATE, CTL_EOL); 320 321 #endif /* PAX_ASLR */ 322 } 323 324 /* 325 * Initialize PaX. 326 */ 327 void 328 pax_init(void) 329 { 330 #ifdef PAX_SEGVGUARD 331 int error; 332 333 error = fileassoc_register("segvguard", pax_segvguard_cleanup_cb, 334 &segvguard_id); 335 if (error) { 336 panic("pax_init: segvguard_id: error=%d\n", error); 337 } 338 #endif /* PAX_SEGVGUARD */ 339 #ifdef PAX_ASLR 340 /* Adjust maximum stack by the size we can consume for ASLR */ 341 extern rlim_t maxsmap; 342 maxsmap = MAXSSIZ - (MAXSSIZ / PAX_ASLR_MAX_STACK_WASTE); 343 // XXX: compat32 is not handled. 344 #endif 345 } 346 347 void 348 pax_setup_elf_flags(struct exec_package *epp, uint32_t elf_flags) 349 { 350 uint32_t flags = 0; 351 352 #ifdef PAX_ASLR 353 if (pax_aslr_elf_flags_active(elf_flags)) { 354 flags |= P_PAX_ASLR; 355 } 356 #endif 357 #ifdef PAX_MPROTECT 358 if (pax_mprotect_elf_flags_active(elf_flags)) { 359 flags |= P_PAX_MPROTECT; 360 } 361 #endif 362 #ifdef PAX_SEGVGUARD 363 if (pax_segvguard_elf_flags_active(elf_flags)) { 364 flags |= P_PAX_GUARD; 365 } 366 #endif 367 368 epp->ep_pax_flags = flags; 369 } 370 371 #if defined(PAX_MPROTECT) || defined(PAX_SEGVGUARD) || defined(PAX_ASLR) 372 static inline bool 373 pax_flags_active(uint32_t flags, uint32_t opt) 374 { 375 if (!(flags & opt)) 376 return false; 377 return true; 378 } 379 #endif /* PAX_MPROTECT || PAX_SEGVGUARD || PAX_ASLR */ 380 381 #ifdef PAX_MPROTECT 382 static bool 383 pax_mprotect_elf_flags_active(uint32_t flags) 384 { 385 if (!pax_mprotect_enabled) 386 return false; 387 if (pax_mprotect_global && (flags & ELF_NOTE_PAX_NOMPROTECT) != 0) { 388 /* Mprotect explicitly disabled */ 389 return false; 390 } 391 if (!pax_mprotect_global && (flags & ELF_NOTE_PAX_MPROTECT) == 0) { 392 /* Mprotect not requested */ 393 return false; 394 } 395 return true; 396 } 397 398 void 399 pax_mprotect_adjust( 400 #ifdef PAX_MPROTECT_DEBUG 401 const char *file, size_t line, 402 #endif 403 struct lwp *l, vm_prot_t *prot, vm_prot_t *maxprot) 404 { 405 uint32_t flags; 406 407 flags = l->l_proc->p_pax; 408 if (!pax_flags_active(flags, P_PAX_MPROTECT)) 409 return; 410 411 if ((*prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) != VM_PROT_EXECUTE) { 412 #ifdef PAX_MPROTECT_DEBUG 413 struct proc *p = l->l_proc; 414 if (pax_mprotect_debug) { 415 printf("%s: %s,%zu: %d.%d (%s): -x\n", 416 __func__, file, line, 417 p->p_pid, l->l_lid, p->p_comm); 418 } 419 #endif 420 *prot &= ~VM_PROT_EXECUTE; 421 *maxprot &= ~VM_PROT_EXECUTE; 422 } else { 423 #ifdef PAX_MPROTECT_DEBUG 424 struct proc *p = l->l_proc; 425 if (pax_mprotect_debug) { 426 printf("%s: %s,%zu: %d.%d (%s): -w\n", 427 __func__, file, line, 428 p->p_pid, l->l_lid, p->p_comm); 429 } 430 #endif 431 *prot &= ~VM_PROT_WRITE; 432 *maxprot &= ~VM_PROT_WRITE; 433 } 434 } 435 #endif /* PAX_MPROTECT */ 436 437 #ifdef PAX_ASLR 438 static bool 439 pax_aslr_elf_flags_active(uint32_t flags) 440 { 441 if (!pax_aslr_enabled) 442 return false; 443 if (pax_aslr_global && (flags & ELF_NOTE_PAX_NOASLR) != 0) { 444 /* ASLR explicitly disabled */ 445 return false; 446 } 447 if (!pax_aslr_global && (flags & ELF_NOTE_PAX_ASLR) == 0) { 448 /* ASLR not requested */ 449 return false; 450 } 451 return true; 452 } 453 454 bool 455 pax_aslr_epp_active(struct exec_package *epp) 456 { 457 return pax_flags_active(epp->ep_pax_flags, P_PAX_ASLR); 458 } 459 460 bool 461 pax_aslr_active(struct lwp *l) 462 { 463 return pax_flags_active(l->l_proc->p_pax, P_PAX_ASLR); 464 } 465 466 void 467 pax_aslr_init_vm(struct lwp *l, struct vmspace *vm, struct exec_package *ep) 468 { 469 if (!pax_aslr_active(l)) 470 return; 471 472 #ifdef PAX_ASLR_DEBUG 473 if (pax_aslr_flags & PAX_ASLR_MMAP) 474 return; 475 #endif 476 477 uint32_t len = (ep->ep_flags & EXEC_32) ? 478 PAX_ASLR_DELTA_MMAP_LEN32 : PAX_ASLR_DELTA_MMAP_LEN; 479 480 uint32_t rand = cprng_fast32(); 481 #ifdef PAX_ASLR_DEBUG 482 if (pax_aslr_flags & PAX_ASLR_FIXED) 483 rand = pax_aslr_rand; 484 #endif 485 vm->vm_aslr_delta_mmap = PAX_ASLR_DELTA(rand, 486 PAX_ASLR_DELTA_MMAP_LSB, len); 487 488 PAX_DPRINTF("delta_mmap=%#jx/%u", vm->vm_aslr_delta_mmap, len); 489 } 490 491 void 492 pax_aslr_mmap(struct lwp *l, vaddr_t *addr, vaddr_t orig_addr, int f) 493 { 494 if (!pax_aslr_active(l)) 495 return; 496 #ifdef PAX_ASLR_DEBUG 497 char buf[256]; 498 499 if (pax_aslr_flags & PAX_ASLR_MMAP) 500 return; 501 502 if (pax_aslr_debug) 503 snprintb(buf, sizeof(buf), MAP_FMT, f); 504 else 505 buf[0] = '\0'; 506 #endif 507 508 if (!(f & MAP_FIXED) && ((orig_addr == 0) || !(f & MAP_ANON))) { 509 PAX_DPRINTF("applying to %#jx orig_addr=%#jx f=%s", 510 (uintmax_t)*addr, (uintmax_t)orig_addr, buf); 511 if (!(l->l_proc->p_vmspace->vm_map.flags & VM_MAP_TOPDOWN)) 512 *addr += l->l_proc->p_vmspace->vm_aslr_delta_mmap; 513 else 514 *addr -= l->l_proc->p_vmspace->vm_aslr_delta_mmap; 515 PAX_DPRINTF("result %#jx", (uintmax_t)*addr); 516 } else { 517 PAX_DPRINTF("not applying to %#jx orig_addr=%#jx f=%s", 518 (uintmax_t)*addr, (uintmax_t)orig_addr, buf); 519 } 520 } 521 522 #define PAX_TRUNC(a, b) ((a) & ~((b) - 1)) 523 vaddr_t 524 pax_aslr_exec_offset(struct exec_package *epp, vaddr_t align) 525 { 526 size_t pax_align, l2, delta; 527 uint32_t rand; 528 vaddr_t offset; 529 530 if (!pax_aslr_epp_active(epp)) 531 goto out; 532 533 #ifdef PAX_ASLR_DEBUG 534 if (pax_aslr_flags & PAX_ASLR_EXEC_OFFSET) 535 goto out; 536 #endif 537 538 pax_align = align == 0 ? PGSHIFT : align; 539 l2 = ilog2(pax_align); 540 541 rand = cprng_fast32(); 542 #ifdef PAX_ASLR_DEBUG 543 if (pax_aslr_flags & PAX_ASLR_FIXED) 544 rand = pax_aslr_rand; 545 #endif 546 delta = PAX_ASLR_DELTA(rand, l2, PAX_ASLR_DELTA_EXEC_LEN); 547 offset = PAX_TRUNC(delta, pax_align) + PAGE_SIZE; 548 549 PAX_DPRINTF("rand=%#x l2=%#zx pax_align=%#zx delta=%#zx offset=%#jx", 550 rand, l2, pax_align, delta, (uintmax_t)offset); 551 return offset; 552 out: 553 return MAX(align, PAGE_SIZE); 554 } 555 556 void 557 pax_aslr_stack(struct exec_package *epp, u_long *max_stack_size) 558 { 559 if (!pax_aslr_epp_active(epp)) 560 return; 561 #ifdef PAX_ASLR_DEBUG 562 if (pax_aslr_flags & PAX_ASLR_STACK) 563 return; 564 #endif 565 566 uint32_t len = (epp->ep_flags & EXEC_32) ? 567 PAX_ASLR_DELTA_STACK_LEN32 : PAX_ASLR_DELTA_STACK_LEN; 568 uint32_t rand = cprng_fast32(); 569 #ifdef PAX_ASLR_DEBUG 570 if (pax_aslr_flags & PAX_ASLR_FIXED) 571 rand = pax_aslr_rand; 572 #endif 573 u_long d = PAX_ASLR_DELTA(rand, PAX_ASLR_DELTA_STACK_LSB, len); 574 d &= (*max_stack_size / PAX_ASLR_MAX_STACK_WASTE) - 1; 575 u_long newminsaddr = (u_long)STACK_GROW(epp->ep_minsaddr, d); 576 PAX_DPRINTF("old minsaddr=%#jx delta=%#lx new minsaddr=%#lx", 577 (uintmax_t)epp->ep_minsaddr, d, newminsaddr); 578 epp->ep_minsaddr = (vaddr_t)newminsaddr; 579 *max_stack_size -= d; 580 } 581 582 uint32_t 583 pax_aslr_stack_gap(struct exec_package *epp) 584 { 585 if (!pax_aslr_epp_active(epp)) 586 return 0; 587 588 #ifdef PAX_ASLR_DEBUG 589 if (pax_aslr_flags & PAX_ASLR_STACK_GAP) 590 return 0; 591 #endif 592 593 uint32_t rand = cprng_fast32(); 594 #ifdef PAX_ASLR_DEBUG 595 if (pax_aslr_flags & PAX_ASLR_FIXED) 596 rand = pax_aslr_rand; 597 #endif 598 rand %= PAGE_SIZE; 599 PAX_DPRINTF("stack gap=%#x\n", rand); 600 return rand; 601 } 602 #endif /* PAX_ASLR */ 603 604 #ifdef PAX_SEGVGUARD 605 static bool 606 pax_segvguard_elf_flags_active(uint32_t flags) 607 { 608 if (!pax_segvguard_enabled) 609 return false; 610 if (pax_segvguard_global && (flags & ELF_NOTE_PAX_NOGUARD) != 0) { 611 /* Segvguard explicitly disabled */ 612 return false; 613 } 614 if (!pax_segvguard_global && (flags & ELF_NOTE_PAX_GUARD) == 0) { 615 /* Segvguard not requested */ 616 return false; 617 } 618 return true; 619 } 620 621 static void 622 pax_segvguard_cleanup_cb(void *v) 623 { 624 struct pax_segvguard_entry *p = v; 625 struct pax_segvguard_uid_entry *up; 626 627 if (p == NULL) { 628 return; 629 } 630 while ((up = LIST_FIRST(&p->segv_uids)) != NULL) { 631 LIST_REMOVE(up, sue_list); 632 kmem_free(up, sizeof(*up)); 633 } 634 kmem_free(p, sizeof(*p)); 635 } 636 637 /* 638 * Called when a process of image vp generated a segfault. 639 */ 640 int 641 pax_segvguard(struct lwp *l, struct vnode *vp, const char *name, 642 bool crashed) 643 { 644 struct pax_segvguard_entry *p; 645 struct pax_segvguard_uid_entry *up; 646 struct timeval tv; 647 uid_t uid; 648 uint32_t flags; 649 bool have_uid; 650 651 flags = l->l_proc->p_pax; 652 if (!pax_flags_active(flags, P_PAX_GUARD)) 653 return 0; 654 655 if (vp == NULL) 656 return EFAULT; 657 658 /* Check if we already monitor the file. */ 659 p = fileassoc_lookup(vp, segvguard_id); 660 661 /* Fast-path if starting a program we don't know. */ 662 if (p == NULL && !crashed) 663 return 0; 664 665 microtime(&tv); 666 667 /* 668 * If a program we don't know crashed, we need to create a new entry 669 * for it. 670 */ 671 if (p == NULL) { 672 p = kmem_alloc(sizeof(*p), KM_SLEEP); 673 fileassoc_add(vp, segvguard_id, p); 674 LIST_INIT(&p->segv_uids); 675 676 /* 677 * Initialize a new entry with "crashes so far" of 1. 678 * The expiry time is when we purge the entry if it didn't 679 * reach the limit. 680 */ 681 up = kmem_alloc(sizeof(*up), KM_SLEEP); 682 up->sue_uid = kauth_cred_getuid(l->l_cred); 683 up->sue_ncrashes = 1; 684 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 685 up->sue_suspended = 0; 686 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 687 return 0; 688 } 689 690 /* 691 * A program we "know" either executed or crashed again. 692 * See if it's a culprit we're familiar with. 693 */ 694 uid = kauth_cred_getuid(l->l_cred); 695 have_uid = false; 696 LIST_FOREACH(up, &p->segv_uids, sue_list) { 697 if (up->sue_uid == uid) { 698 have_uid = true; 699 break; 700 } 701 } 702 703 /* 704 * It's someone else. Add an entry for him if we crashed. 705 */ 706 if (!have_uid) { 707 if (crashed) { 708 up = kmem_alloc(sizeof(*up), KM_SLEEP); 709 up->sue_uid = uid; 710 up->sue_ncrashes = 1; 711 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 712 up->sue_suspended = 0; 713 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 714 } 715 return 0; 716 } 717 718 if (crashed) { 719 /* Check if timer on previous crashes expired first. */ 720 if (up->sue_expiry < tv.tv_sec) { 721 log(LOG_INFO, "PaX Segvguard: [%s] Suspension" 722 " expired.\n", name ? name : "unknown"); 723 up->sue_ncrashes = 1; 724 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 725 up->sue_suspended = 0; 726 return 0; 727 } 728 729 up->sue_ncrashes++; 730 731 if (up->sue_ncrashes >= pax_segvguard_maxcrashes) { 732 log(LOG_ALERT, "PaX Segvguard: [%s] Suspending " 733 "execution for %d seconds after %zu crashes.\n", 734 name ? name : "unknown", pax_segvguard_suspension, 735 up->sue_ncrashes); 736 737 /* Suspend this program for a while. */ 738 up->sue_suspended = tv.tv_sec + pax_segvguard_suspension; 739 up->sue_ncrashes = 0; 740 up->sue_expiry = 0; 741 } 742 } else { 743 /* Are we supposed to be suspended? */ 744 if (up->sue_suspended > tv.tv_sec) { 745 log(LOG_ALERT, "PaX Segvguard: [%s] Preventing " 746 "execution due to repeated segfaults.\n", name ? 747 name : "unknown"); 748 return EPERM; 749 } 750 } 751 752 return 0; 753 } 754 #endif /* PAX_SEGVGUARD */ 755
Indexes created Mon Sep 22 05:09:51 GMT 2025