kern_pax.c revision 1.53
1 /* $NetBSD: kern_pax.c,v 1.53 2016/05/25 20:07:54 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 1.53 2016/05/25 20:07:54 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 int pax_mprotect_ptrace = 1; 121 static bool pax_mprotect_elf_flags_active(uint32_t); 122 #endif /* PAX_MPROTECT */ 123 #ifdef PAX_MPROTECT_DEBUG 124 int pax_mprotect_debug; 125 #endif 126 127 #ifdef PAX_SEGVGUARD 128 #ifndef PAX_SEGVGUARD_EXPIRY 129 #define PAX_SEGVGUARD_EXPIRY (2 * 60) 130 #endif 131 #ifndef PAX_SEGVGUARD_SUSPENSION 132 #define PAX_SEGVGUARD_SUSPENSION (10 * 60) 133 #endif 134 #ifndef PAX_SEGVGUARD_MAXCRASHES 135 #define PAX_SEGVGUARD_MAXCRASHES 5 136 #endif 137 138 #ifdef PAX_ASLR_DEBUG 139 int pax_aslr_debug; 140 /* flag set means disable */ 141 int pax_aslr_flags; 142 uint32_t pax_aslr_rand; 143 #define PAX_ASLR_STACK 0x01 144 #define PAX_ASLR_STACK_GAP 0x02 145 #define PAX_ASLR_MMAP 0x04 146 #define PAX_ASLR_EXEC_OFFSET 0x08 147 #define PAX_ASLR_RTLD_OFFSET 0x10 148 #define PAX_ASLR_FIXED 0x20 149 #endif 150 151 static int pax_segvguard_enabled = 1; 152 static int pax_segvguard_global = PAX_SEGVGUARD; 153 static int pax_segvguard_expiry = PAX_SEGVGUARD_EXPIRY; 154 static int pax_segvguard_suspension = PAX_SEGVGUARD_SUSPENSION; 155 static int pax_segvguard_maxcrashes = PAX_SEGVGUARD_MAXCRASHES; 156 157 static fileassoc_t segvguard_id; 158 159 struct pax_segvguard_uid_entry { 160 uid_t sue_uid; 161 size_t sue_ncrashes; 162 time_t sue_expiry; 163 time_t sue_suspended; 164 LIST_ENTRY(pax_segvguard_uid_entry) sue_list; 165 }; 166 167 struct pax_segvguard_entry { 168 LIST_HEAD(, pax_segvguard_uid_entry) segv_uids; 169 }; 170 171 static bool pax_segvguard_elf_flags_active(uint32_t); 172 static void pax_segvguard_cleanup_cb(void *); 173 #endif /* PAX_SEGVGUARD */ 174 175 SYSCTL_SETUP(sysctl_security_pax_setup, "sysctl security.pax setup") 176 { 177 const struct sysctlnode *rnode = NULL, *cnode; 178 179 sysctl_createv(clog, 0, NULL, &rnode, 180 CTLFLAG_PERMANENT, 181 CTLTYPE_NODE, "pax", 182 SYSCTL_DESCR("PaX (exploit mitigation) features."), 183 NULL, 0, NULL, 0, 184 CTL_SECURITY, CTL_CREATE, CTL_EOL); 185 186 cnode = rnode; 187 188 #ifdef PAX_MPROTECT 189 rnode = cnode; 190 sysctl_createv(clog, 0, &rnode, &rnode, 191 CTLFLAG_PERMANENT, 192 CTLTYPE_NODE, "mprotect", 193 SYSCTL_DESCR("mprotect(2) W^X restrictions."), 194 NULL, 0, NULL, 0, 195 CTL_CREATE, CTL_EOL); 196 sysctl_createv(clog, 0, &rnode, NULL, 197 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 198 CTLTYPE_INT, "enabled", 199 SYSCTL_DESCR("Restrictions enabled."), 200 NULL, 0, &pax_mprotect_enabled, 0, 201 CTL_CREATE, CTL_EOL); 202 sysctl_createv(clog, 0, &rnode, NULL, 203 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 204 CTLTYPE_INT, "global", 205 SYSCTL_DESCR("When enabled, unless explicitly " 206 "specified, apply restrictions to " 207 "all processes."), 208 NULL, 0, &pax_mprotect_global, 0, 209 CTL_CREATE, CTL_EOL); 210 sysctl_createv(clog, 0, &rnode, NULL, 211 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 212 CTLTYPE_INT, "ptrace", 213 SYSCTL_DESCR("When enabled, allow ptrace(2) to " 214 "override mprotect permissions on traced " 215 "processes"), 216 NULL, 0, &pax_mprotect_ptrace, 0, 217 CTL_CREATE, CTL_EOL); 218 #ifdef PAX_MPROTECT_DEBUG 219 sysctl_createv(clog, 0, &rnode, NULL, 220 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 221 CTLTYPE_INT, "debug", 222 SYSCTL_DESCR("print mprotect changes."), 223 NULL, 0, &pax_mprotect_debug, 0, 224 CTL_CREATE, CTL_EOL); 225 #endif 226 #endif /* PAX_MPROTECT */ 227 228 #ifdef PAX_SEGVGUARD 229 rnode = cnode; 230 sysctl_createv(clog, 0, &rnode, &rnode, 231 CTLFLAG_PERMANENT, 232 CTLTYPE_NODE, "segvguard", 233 SYSCTL_DESCR("PaX segvguard."), 234 NULL, 0, NULL, 0, 235 CTL_CREATE, CTL_EOL); 236 sysctl_createv(clog, 0, &rnode, NULL, 237 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 238 CTLTYPE_INT, "enabled", 239 SYSCTL_DESCR("segvguard enabled."), 240 NULL, 0, &pax_segvguard_enabled, 0, 241 CTL_CREATE, CTL_EOL); 242 sysctl_createv(clog, 0, &rnode, NULL, 243 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 244 CTLTYPE_INT, "global", 245 SYSCTL_DESCR("segvguard all programs."), 246 NULL, 0, &pax_segvguard_global, 0, 247 CTL_CREATE, CTL_EOL); 248 sysctl_createv(clog, 0, &rnode, NULL, 249 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 250 CTLTYPE_INT, "expiry_timeout", 251 SYSCTL_DESCR("Entry expiry timeout (in seconds)."), 252 NULL, 0, &pax_segvguard_expiry, 0, 253 CTL_CREATE, CTL_EOL); 254 sysctl_createv(clog, 0, &rnode, NULL, 255 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 256 CTLTYPE_INT, "suspend_timeout", 257 SYSCTL_DESCR("Entry suspension timeout (in seconds)."), 258 NULL, 0, &pax_segvguard_suspension, 0, 259 CTL_CREATE, CTL_EOL); 260 sysctl_createv(clog, 0, &rnode, NULL, 261 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 262 CTLTYPE_INT, "max_crashes", 263 SYSCTL_DESCR("Max number of crashes before expiry."), 264 NULL, 0, &pax_segvguard_maxcrashes, 0, 265 CTL_CREATE, CTL_EOL); 266 #endif /* PAX_SEGVGUARD */ 267 268 #ifdef PAX_ASLR 269 rnode = cnode; 270 sysctl_createv(clog, 0, &rnode, &rnode, 271 CTLFLAG_PERMANENT, 272 CTLTYPE_NODE, "aslr", 273 SYSCTL_DESCR("Address Space Layout Randomization."), 274 NULL, 0, NULL, 0, 275 CTL_CREATE, CTL_EOL); 276 sysctl_createv(clog, 0, &rnode, NULL, 277 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 278 CTLTYPE_INT, "enabled", 279 SYSCTL_DESCR("Restrictions enabled."), 280 NULL, 0, &pax_aslr_enabled, 0, 281 CTL_CREATE, CTL_EOL); 282 sysctl_createv(clog, 0, &rnode, NULL, 283 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 284 CTLTYPE_INT, "global", 285 SYSCTL_DESCR("When enabled, unless explicitly " 286 "specified, apply to all processes."), 287 NULL, 0, &pax_aslr_global, 0, 288 CTL_CREATE, CTL_EOL); 289 #ifdef PAX_ASLR_DEBUG 290 sysctl_createv(clog, 0, &rnode, NULL, 291 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 292 CTLTYPE_INT, "debug", 293 SYSCTL_DESCR("Pring ASLR selected addresses."), 294 NULL, 0, &pax_aslr_debug, 0, 295 CTL_CREATE, CTL_EOL); 296 sysctl_createv(clog, 0, &rnode, NULL, 297 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 298 CTLTYPE_INT, "flags", 299 SYSCTL_DESCR("Disable/Enable select ASLR features."), 300 NULL, 0, &pax_aslr_flags, 0, 301 CTL_CREATE, CTL_EOL); 302 sysctl_createv(clog, 0, &rnode, NULL, 303 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 304 CTLTYPE_INT, "rand", 305 SYSCTL_DESCR("Use the given fixed random value"), 306 NULL, 0, &pax_aslr_rand, 0, 307 CTL_CREATE, CTL_EOL); 308 #endif 309 sysctl_createv(clog, 0, &rnode, NULL, 310 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 311 CTLTYPE_INT, "mmap_len", 312 SYSCTL_DESCR("Number of bits randomized for " 313 "mmap(2) calls."), 314 NULL, PAX_ASLR_DELTA_MMAP_LEN, NULL, 0, 315 CTL_CREATE, CTL_EOL); 316 sysctl_createv(clog, 0, &rnode, NULL, 317 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 318 CTLTYPE_INT, "stack_len", 319 SYSCTL_DESCR("Number of bits randomized for " 320 "the stack."), 321 NULL, PAX_ASLR_DELTA_STACK_LEN, NULL, 0, 322 CTL_CREATE, CTL_EOL); 323 sysctl_createv(clog, 0, &rnode, NULL, 324 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 325 CTLTYPE_INT, "exec_len", 326 SYSCTL_DESCR("Number of bits randomized for " 327 "the PIE exec base."), 328 NULL, PAX_ASLR_DELTA_EXEC_LEN, NULL, 0, 329 CTL_CREATE, CTL_EOL); 330 331 #endif /* PAX_ASLR */ 332 } 333 334 /* 335 * Initialize PaX. 336 */ 337 void 338 pax_init(void) 339 { 340 #ifdef PAX_SEGVGUARD 341 int error; 342 343 error = fileassoc_register("segvguard", pax_segvguard_cleanup_cb, 344 &segvguard_id); 345 if (error) { 346 panic("pax_init: segvguard_id: error=%d\n", error); 347 } 348 #endif /* PAX_SEGVGUARD */ 349 #ifdef PAX_ASLR 350 /* Adjust maximum stack by the size we can consume for ASLR */ 351 extern rlim_t maxsmap; 352 maxsmap = MAXSSIZ - (MAXSSIZ / PAX_ASLR_MAX_STACK_WASTE); 353 // XXX: compat32 is not handled. 354 #endif 355 } 356 357 void 358 pax_set_flags(struct exec_package *epp, struct proc *p) 359 { 360 p->p_pax = epp->ep_pax_flags; 361 362 if (pax_mprotect_ptrace == 0) 363 return; 364 /* 365 * If we are running under the debugger, turn off MPROTECT so 366 * the debugger can insert/delete breakpoints 367 */ 368 if (p->p_slflag & PSL_TRACED) 369 p->p_pax &= ~P_PAX_MPROTECT; 370 } 371 372 void 373 pax_setup_elf_flags(struct exec_package *epp, uint32_t elf_flags) 374 { 375 uint32_t flags = 0; 376 377 #ifdef PAX_ASLR 378 if (pax_aslr_elf_flags_active(elf_flags)) { 379 flags |= P_PAX_ASLR; 380 } 381 #endif 382 #ifdef PAX_MPROTECT 383 if (pax_mprotect_elf_flags_active(elf_flags)) { 384 flags |= P_PAX_MPROTECT; 385 } 386 #endif 387 #ifdef PAX_SEGVGUARD 388 if (pax_segvguard_elf_flags_active(elf_flags)) { 389 flags |= P_PAX_GUARD; 390 } 391 #endif 392 393 epp->ep_pax_flags = flags; 394 } 395 396 #if defined(PAX_MPROTECT) || defined(PAX_SEGVGUARD) || defined(PAX_ASLR) 397 static inline bool 398 pax_flags_active(uint32_t flags, uint32_t opt) 399 { 400 if (!(flags & opt)) 401 return false; 402 return true; 403 } 404 #endif /* PAX_MPROTECT || PAX_SEGVGUARD || PAX_ASLR */ 405 406 #ifdef PAX_MPROTECT 407 static bool 408 pax_mprotect_elf_flags_active(uint32_t flags) 409 { 410 if (!pax_mprotect_enabled) 411 return false; 412 if (pax_mprotect_global && (flags & ELF_NOTE_PAX_NOMPROTECT) != 0) { 413 /* Mprotect explicitly disabled */ 414 return false; 415 } 416 if (!pax_mprotect_global && (flags & ELF_NOTE_PAX_MPROTECT) == 0) { 417 /* Mprotect not requested */ 418 return false; 419 } 420 return true; 421 } 422 423 void 424 pax_mprotect_adjust( 425 #ifdef PAX_MPROTECT_DEBUG 426 const char *file, size_t line, 427 #endif 428 struct lwp *l, vm_prot_t *prot, vm_prot_t *maxprot) 429 { 430 uint32_t flags; 431 432 flags = l->l_proc->p_pax; 433 if (!pax_flags_active(flags, P_PAX_MPROTECT)) 434 return; 435 436 if ((*prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) != VM_PROT_EXECUTE) { 437 #ifdef PAX_MPROTECT_DEBUG 438 struct proc *p = l->l_proc; 439 if ((*prot & VM_PROT_EXECUTE) && pax_mprotect_debug) { 440 printf("%s: %s,%zu: %d.%d (%s): -x\n", 441 __func__, file, line, 442 p->p_pid, l->l_lid, p->p_comm); 443 } 444 #endif 445 *prot &= ~VM_PROT_EXECUTE; 446 *maxprot &= ~VM_PROT_EXECUTE; 447 } else { 448 #ifdef PAX_MPROTECT_DEBUG 449 struct proc *p = l->l_proc; 450 if ((*prot & VM_PROT_WRITE) && pax_mprotect_debug) { 451 printf("%s: %s,%zu: %d.%d (%s): -w\n", 452 __func__, file, line, 453 p->p_pid, l->l_lid, p->p_comm); 454 } 455 #endif 456 *prot &= ~VM_PROT_WRITE; 457 *maxprot &= ~VM_PROT_WRITE; 458 } 459 } 460 461 /* 462 * Bypass MPROTECT for traced processes 463 */ 464 int 465 pax_mprotect_prot(struct lwp *l) 466 { 467 uint32_t flags; 468 469 flags = l->l_proc->p_pax; 470 if (!pax_flags_active(flags, P_PAX_MPROTECT)) 471 return 0; 472 if (pax_mprotect_ptrace < 2) 473 return 0; 474 return UVM_EXTRACT_PROT_ALL; 475 } 476 477 478 #endif /* PAX_MPROTECT */ 479 480 #ifdef PAX_ASLR 481 static bool 482 pax_aslr_elf_flags_active(uint32_t flags) 483 { 484 if (!pax_aslr_enabled) 485 return false; 486 if (pax_aslr_global && (flags & ELF_NOTE_PAX_NOASLR) != 0) { 487 /* ASLR explicitly disabled */ 488 return false; 489 } 490 if (!pax_aslr_global && (flags & ELF_NOTE_PAX_ASLR) == 0) { 491 /* ASLR not requested */ 492 return false; 493 } 494 return true; 495 } 496 497 static bool 498 pax_aslr_epp_active(struct exec_package *epp) 499 { 500 if (__predict_false((epp->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0)) 501 return false; 502 return pax_flags_active(epp->ep_pax_flags, P_PAX_ASLR); 503 } 504 505 static bool 506 pax_aslr_active(struct lwp *l) 507 { 508 return pax_flags_active(l->l_proc->p_pax, P_PAX_ASLR); 509 } 510 511 void 512 pax_aslr_init_vm(struct lwp *l, struct vmspace *vm, struct exec_package *ep) 513 { 514 if (!pax_aslr_active(l)) 515 return; 516 517 if (__predict_false((ep->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0)) 518 return; 519 520 #ifdef PAX_ASLR_DEBUG 521 if (pax_aslr_flags & PAX_ASLR_MMAP) 522 return; 523 #endif 524 525 uint32_t len = (ep->ep_flags & EXEC_32) ? 526 PAX_ASLR_DELTA_MMAP_LEN32 : PAX_ASLR_DELTA_MMAP_LEN; 527 528 uint32_t rand = cprng_fast32(); 529 #ifdef PAX_ASLR_DEBUG 530 if (pax_aslr_flags & PAX_ASLR_FIXED) 531 rand = pax_aslr_rand; 532 #endif 533 vm->vm_aslr_delta_mmap = PAX_ASLR_DELTA(rand, 534 PAX_ASLR_DELTA_MMAP_LSB, len); 535 536 PAX_DPRINTF("delta_mmap=%#jx/%u", 537 (uintmax_t)vm->vm_aslr_delta_mmap, len); 538 } 539 540 void 541 pax_aslr_mmap(struct lwp *l, vaddr_t *addr, vaddr_t orig_addr, int f) 542 { 543 if (!pax_aslr_active(l)) 544 return; 545 #ifdef PAX_ASLR_DEBUG 546 char buf[256]; 547 548 if (pax_aslr_flags & PAX_ASLR_MMAP) 549 return; 550 551 if (pax_aslr_debug) 552 snprintb(buf, sizeof(buf), MAP_FMT, f); 553 else 554 buf[0] = '\0'; 555 #endif 556 557 if (!(f & MAP_FIXED) && ((orig_addr == 0) || !(f & MAP_ANON))) { 558 PAX_DPRINTF("applying to %#jx orig_addr=%#jx f=%s", 559 (uintmax_t)*addr, (uintmax_t)orig_addr, buf); 560 if (!(l->l_proc->p_vmspace->vm_map.flags & VM_MAP_TOPDOWN)) 561 *addr += l->l_proc->p_vmspace->vm_aslr_delta_mmap; 562 else 563 *addr -= l->l_proc->p_vmspace->vm_aslr_delta_mmap; 564 PAX_DPRINTF("result %#jx", (uintmax_t)*addr); 565 } else { 566 PAX_DPRINTF("not applying to %#jx orig_addr=%#jx f=%s", 567 (uintmax_t)*addr, (uintmax_t)orig_addr, buf); 568 } 569 } 570 571 static vaddr_t 572 pax_aslr_offset(vaddr_t align) 573 { 574 size_t pax_align, l2, delta; 575 uint32_t rand; 576 vaddr_t offset; 577 578 pax_align = align == 0 ? PGSHIFT : align; 579 l2 = ilog2(pax_align); 580 581 rand = cprng_fast32(); 582 #ifdef PAX_ASLR_DEBUG 583 if (pax_aslr_flags & PAX_ASLR_FIXED) 584 rand = pax_aslr_rand; 585 #endif 586 587 #define PAX_TRUNC(a, b) ((a) & ~((b) - 1)) 588 589 delta = PAX_ASLR_DELTA(rand, l2, PAX_ASLR_DELTA_EXEC_LEN); 590 offset = PAX_TRUNC(delta, pax_align) + PAGE_SIZE; 591 592 PAX_DPRINTF("rand=%#x l2=%#zx pax_align=%#zx delta=%#zx offset=%#jx", 593 rand, l2, pax_align, delta, (uintmax_t)offset); 594 595 return offset; 596 } 597 598 vaddr_t 599 pax_aslr_exec_offset(struct exec_package *epp, vaddr_t align) 600 { 601 if (!pax_aslr_epp_active(epp)) 602 goto out; 603 604 #ifdef PAX_ASLR_DEBUG 605 if (pax_aslr_flags & PAX_ASLR_EXEC_OFFSET) 606 goto out; 607 #endif 608 return pax_aslr_offset(align) + PAGE_SIZE; 609 out: 610 return MAX(align, PAGE_SIZE); 611 } 612 613 voff_t 614 pax_aslr_rtld_offset(struct exec_package *epp, vaddr_t align, int use_topdown) 615 { 616 voff_t offset; 617 618 if (!pax_aslr_epp_active(epp)) 619 return 0; 620 621 #ifdef PAX_ASLR_DEBUG 622 if (pax_aslr_flags & PAX_ASLR_RTLD_OFFSET) 623 return 0; 624 #endif 625 offset = pax_aslr_offset(align); 626 if (use_topdown) 627 offset = -offset; 628 629 return offset; 630 } 631 632 void 633 pax_aslr_stack(struct exec_package *epp, u_long *max_stack_size) 634 { 635 if (!pax_aslr_epp_active(epp)) 636 return; 637 #ifdef PAX_ASLR_DEBUG 638 if (pax_aslr_flags & PAX_ASLR_STACK) 639 return; 640 #endif 641 642 uint32_t len = (epp->ep_flags & EXEC_32) ? 643 PAX_ASLR_DELTA_STACK_LEN32 : PAX_ASLR_DELTA_STACK_LEN; 644 uint32_t rand = cprng_fast32(); 645 #ifdef PAX_ASLR_DEBUG 646 if (pax_aslr_flags & PAX_ASLR_FIXED) 647 rand = pax_aslr_rand; 648 #endif 649 u_long d = PAX_ASLR_DELTA(rand, PAX_ASLR_DELTA_STACK_LSB, len); 650 d &= (*max_stack_size / PAX_ASLR_MAX_STACK_WASTE) - 1; 651 u_long newminsaddr = (u_long)STACK_GROW(epp->ep_minsaddr, d); 652 PAX_DPRINTF("old minsaddr=%#jx delta=%#lx new minsaddr=%#lx", 653 (uintmax_t)epp->ep_minsaddr, d, newminsaddr); 654 epp->ep_minsaddr = (vaddr_t)newminsaddr; 655 *max_stack_size -= d; 656 } 657 658 uint32_t 659 pax_aslr_stack_gap(struct exec_package *epp) 660 { 661 if (!pax_aslr_epp_active(epp)) 662 return 0; 663 664 #ifdef PAX_ASLR_DEBUG 665 if (pax_aslr_flags & PAX_ASLR_STACK_GAP) 666 return 0; 667 #endif 668 669 uint32_t rand = cprng_fast32(); 670 #ifdef PAX_ASLR_DEBUG 671 if (pax_aslr_flags & PAX_ASLR_FIXED) 672 rand = pax_aslr_rand; 673 #endif 674 rand %= PAGE_SIZE; 675 PAX_DPRINTF("stack gap=%#x\n", rand); 676 return rand; 677 } 678 #endif /* PAX_ASLR */ 679 680 #ifdef PAX_SEGVGUARD 681 static bool 682 pax_segvguard_elf_flags_active(uint32_t flags) 683 { 684 if (!pax_segvguard_enabled) 685 return false; 686 if (pax_segvguard_global && (flags & ELF_NOTE_PAX_NOGUARD) != 0) { 687 /* Segvguard explicitly disabled */ 688 return false; 689 } 690 if (!pax_segvguard_global && (flags & ELF_NOTE_PAX_GUARD) == 0) { 691 /* Segvguard not requested */ 692 return false; 693 } 694 return true; 695 } 696 697 static void 698 pax_segvguard_cleanup_cb(void *v) 699 { 700 struct pax_segvguard_entry *p = v; 701 struct pax_segvguard_uid_entry *up; 702 703 if (p == NULL) { 704 return; 705 } 706 while ((up = LIST_FIRST(&p->segv_uids)) != NULL) { 707 LIST_REMOVE(up, sue_list); 708 kmem_free(up, sizeof(*up)); 709 } 710 kmem_free(p, sizeof(*p)); 711 } 712 713 /* 714 * Called when a process of image vp generated a segfault. 715 */ 716 int 717 pax_segvguard(struct lwp *l, struct vnode *vp, const char *name, 718 bool crashed) 719 { 720 struct pax_segvguard_entry *p; 721 struct pax_segvguard_uid_entry *up; 722 struct timeval tv; 723 uid_t uid; 724 uint32_t flags; 725 bool have_uid; 726 727 flags = l->l_proc->p_pax; 728 if (!pax_flags_active(flags, P_PAX_GUARD)) 729 return 0; 730 731 if (vp == NULL) 732 return EFAULT; 733 734 /* Check if we already monitor the file. */ 735 p = fileassoc_lookup(vp, segvguard_id); 736 737 /* Fast-path if starting a program we don't know. */ 738 if (p == NULL && !crashed) 739 return 0; 740 741 microtime(&tv); 742 743 /* 744 * If a program we don't know crashed, we need to create a new entry 745 * for it. 746 */ 747 if (p == NULL) { 748 p = kmem_alloc(sizeof(*p), KM_SLEEP); 749 fileassoc_add(vp, segvguard_id, p); 750 LIST_INIT(&p->segv_uids); 751 752 /* 753 * Initialize a new entry with "crashes so far" of 1. 754 * The expiry time is when we purge the entry if it didn't 755 * reach the limit. 756 */ 757 up = kmem_alloc(sizeof(*up), KM_SLEEP); 758 up->sue_uid = kauth_cred_getuid(l->l_cred); 759 up->sue_ncrashes = 1; 760 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 761 up->sue_suspended = 0; 762 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 763 return 0; 764 } 765 766 /* 767 * A program we "know" either executed or crashed again. 768 * See if it's a culprit we're familiar with. 769 */ 770 uid = kauth_cred_getuid(l->l_cred); 771 have_uid = false; 772 LIST_FOREACH(up, &p->segv_uids, sue_list) { 773 if (up->sue_uid == uid) { 774 have_uid = true; 775 break; 776 } 777 } 778 779 /* 780 * It's someone else. Add an entry for him if we crashed. 781 */ 782 if (!have_uid) { 783 if (crashed) { 784 up = kmem_alloc(sizeof(*up), KM_SLEEP); 785 up->sue_uid = uid; 786 up->sue_ncrashes = 1; 787 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 788 up->sue_suspended = 0; 789 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 790 } 791 return 0; 792 } 793 794 if (crashed) { 795 /* Check if timer on previous crashes expired first. */ 796 if (up->sue_expiry < tv.tv_sec) { 797 log(LOG_INFO, "PaX Segvguard: [%s] Suspension" 798 " expired.\n", name ? name : "unknown"); 799 up->sue_ncrashes = 1; 800 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 801 up->sue_suspended = 0; 802 return 0; 803 } 804 805 up->sue_ncrashes++; 806 807 if (up->sue_ncrashes >= pax_segvguard_maxcrashes) { 808 log(LOG_ALERT, "PaX Segvguard: [%s] Suspending " 809 "execution for %d seconds after %zu crashes.\n", 810 name ? name : "unknown", pax_segvguard_suspension, 811 up->sue_ncrashes); 812 813 /* Suspend this program for a while. */ 814 up->sue_suspended = tv.tv_sec + pax_segvguard_suspension; 815 up->sue_ncrashes = 0; 816 up->sue_expiry = 0; 817 } 818 } else { 819 /* Are we supposed to be suspended? */ 820 if (up->sue_suspended > tv.tv_sec) { 821 log(LOG_ALERT, "PaX Segvguard: [%s] Preventing " 822 "execution due to repeated segfaults.\n", name ? 823 name : "unknown"); 824 return EPERM; 825 } 826 } 827 828 return 0; 829 } 830 #endif /* PAX_SEGVGUARD */ 831
Indexes created Tue Sep 30 11:09:46 GMT 2025