kern_pax.c revision 1.57
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 (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 1.57 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 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 #ifdef PAX_ASLR_DEBUG 115 int pax_aslr_debug; 116 /* flag set means disable */ 117 int pax_aslr_flags; 118 uint32_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 126 127 static bool pax_aslr_elf_flags_active(uint32_t); 128 #endif /* PAX_ASLR */ 129 130 #ifdef PAX_MPROTECT 131 static int pax_mprotect_enabled = 1; 132 static int pax_mprotect_global = PAX_MPROTECT; 133 static int pax_mprotect_ptrace = 1; 134 static bool pax_mprotect_elf_flags_active(uint32_t); 135 #endif /* PAX_MPROTECT */ 136 #ifdef PAX_MPROTECT_DEBUG 137 int 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 150 151 152 static int pax_segvguard_enabled = 1; 153 static int pax_segvguard_global = PAX_SEGVGUARD; 154 static int pax_segvguard_expiry = PAX_SEGVGUARD_EXPIRY; 155 static int pax_segvguard_suspension = PAX_SEGVGUARD_SUSPENSION; 156 static int pax_segvguard_maxcrashes = PAX_SEGVGUARD_MAXCRASHES; 157 158 static fileassoc_t segvguard_id; 159 160 struct 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 }; 167 168 struct pax_segvguard_entry { 169 LIST_HEAD(, pax_segvguard_uid_entry) segv_uids; 170 }; 171 172 static bool pax_segvguard_elf_flags_active(uint32_t); 173 static void pax_segvguard_cleanup_cb(void *); 174 #endif /* PAX_SEGVGUARD */ 175 176 SYSCTL_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 */ 338 void 339 pax_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 } 357 358 void 359 pax_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 } 374 375 void 376 pax_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) 400 static inline bool 401 pax_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 410 static bool 411 pax_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 } 425 426 void 427 pax_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 */ 467 int 468 pax_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 484 static bool 485 pax_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 } 499 500 static bool 501 pax_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 } 507 508 static bool 509 pax_aslr_active(struct lwp *l) 510 { 511 return pax_flags_active(l->l_proc->p_pax, P_PAX_ASLR); 512 } 513 514 void 515 pax_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 } 542 543 void 544 pax_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 } 573 574 static vaddr_t 575 pax_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 } 600 601 vaddr_t 602 pax_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; 612 out: 613 return MAX(align, PAGE_SIZE); 614 } 615 616 voff_t 617 pax_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 } 634 635 void 636 pax_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 } 660 661 uint32_t 662 pax_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 684 static bool 685 pax_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 } 699 700 static void 701 pax_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 */ 719 int 720 pax_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
Indexes created Sun Sep 21 20:09:37 GMT 2025