kern_pax.c revision 1.59
1 /* $NetBSD: kern_pax.c,v 1.59 2017/05/06 21:34:51 joerg 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 1.59 2017/05/06 21:34:51 joerg 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 vm_prot_t 427 pax_mprotect_maxprotect( 428 #ifdef PAX_MPROTECT_DEBUG 429 const char *file, size_t line, 430 #endif 431 struct lwp *l, vm_prot_t active, vm_prot_t extra, 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 maxprot; 438 439 return (active|extra) & maxprot; 440 } 441 442 int 443 pax_mprotect_validate( 444 #ifdef PAX_MPROTECT_DEBUG 445 const char *file, size_t line, 446 #endif 447 struct lwp *l, vm_prot_t prot) 448 { 449 uint32_t flags; 450 451 flags = l->l_proc->p_pax; 452 if (!pax_flags_active(flags, P_PAX_MPROTECT)) 453 return 0; 454 455 if ((prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) == 456 (VM_PROT_WRITE|VM_PROT_EXECUTE)) { 457 #ifdef PAX_MPROTECT_DEBUG 458 struct proc *p = l->l_proc; 459 460 if (pax_mprotect_debug) 461 printf("%s: %s,%zu: %d.%d (%s): WX rejected\n", 462 __func__, file, line, 463 p->p_pid, l->l_lid, p->p_comm); 464 #endif 465 return EACCES; 466 } 467 return 0; 468 } 469 470 /* 471 * Bypass MPROTECT for traced processes 472 */ 473 int 474 pax_mprotect_prot(struct lwp *l) 475 { 476 uint32_t flags; 477 478 flags = l->l_proc->p_pax; 479 if (!pax_flags_active(flags, P_PAX_MPROTECT)) 480 return 0; 481 if (pax_mprotect_ptrace < 2) 482 return 0; 483 return UVM_EXTRACT_PROT_ALL; 484 } 485 486 487 #endif /* PAX_MPROTECT */ 488 489 #ifdef PAX_ASLR 490 static bool 491 pax_aslr_elf_flags_active(uint32_t flags) 492 { 493 if (!pax_aslr_enabled) 494 return false; 495 if (pax_aslr_global && (flags & ELF_NOTE_PAX_NOASLR) != 0) { 496 /* ASLR explicitly disabled */ 497 return false; 498 } 499 if (!pax_aslr_global && (flags & ELF_NOTE_PAX_ASLR) == 0) { 500 /* ASLR not requested */ 501 return false; 502 } 503 return true; 504 } 505 506 static bool 507 pax_aslr_epp_active(struct exec_package *epp) 508 { 509 if (__predict_false((epp->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0)) 510 return false; 511 return pax_flags_active(epp->ep_pax_flags, P_PAX_ASLR); 512 } 513 514 static bool 515 pax_aslr_active(struct lwp *l) 516 { 517 return pax_flags_active(l->l_proc->p_pax, P_PAX_ASLR); 518 } 519 520 void 521 pax_aslr_init_vm(struct lwp *l, struct vmspace *vm, struct exec_package *ep) 522 { 523 if (!pax_aslr_active(l)) 524 return; 525 526 if (__predict_false((ep->ep_flags & (EXEC_32|EXEC_TOPDOWN_VM)) == 0)) 527 return; 528 529 #ifdef PAX_ASLR_DEBUG 530 if (pax_aslr_flags & PAX_ASLR_MMAP) 531 return; 532 #endif 533 534 uint32_t len = (ep->ep_flags & EXEC_32) ? 535 PAX_ASLR_DELTA_MMAP_LEN32 : PAX_ASLR_DELTA_MMAP_LEN; 536 537 uint32_t rand = cprng_fast32(); 538 #ifdef PAX_ASLR_DEBUG 539 if (pax_aslr_flags & PAX_ASLR_FIXED) 540 rand = pax_aslr_rand; 541 #endif 542 vm->vm_aslr_delta_mmap = PAX_ASLR_DELTA(rand, 543 PAX_ASLR_DELTA_MMAP_LSB, len); 544 545 PAX_DPRINTF("delta_mmap=%#jx/%u", 546 (uintmax_t)vm->vm_aslr_delta_mmap, len); 547 } 548 549 void 550 pax_aslr_mmap(struct lwp *l, vaddr_t *addr, vaddr_t orig_addr, int f) 551 { 552 if (!pax_aslr_active(l)) 553 return; 554 #ifdef PAX_ASLR_DEBUG 555 char buf[256]; 556 557 if (pax_aslr_flags & PAX_ASLR_MMAP) 558 return; 559 560 if (pax_aslr_debug) 561 snprintb(buf, sizeof(buf), MAP_FMT, f); 562 else 563 buf[0] = '\0'; 564 #endif 565 566 if (!(f & MAP_FIXED) && ((orig_addr == 0) || !(f & MAP_ANON))) { 567 PAX_DPRINTF("applying to %#jx orig_addr=%#jx f=%s", 568 (uintmax_t)*addr, (uintmax_t)orig_addr, buf); 569 if (!(l->l_proc->p_vmspace->vm_map.flags & VM_MAP_TOPDOWN)) 570 *addr += l->l_proc->p_vmspace->vm_aslr_delta_mmap; 571 else 572 *addr -= l->l_proc->p_vmspace->vm_aslr_delta_mmap; 573 PAX_DPRINTF("result %#jx", (uintmax_t)*addr); 574 } else { 575 PAX_DPRINTF("not applying to %#jx orig_addr=%#jx f=%s", 576 (uintmax_t)*addr, (uintmax_t)orig_addr, buf); 577 } 578 } 579 580 static vaddr_t 581 pax_aslr_offset(vaddr_t align) 582 { 583 size_t pax_align, l2, delta; 584 uint32_t rand; 585 vaddr_t offset; 586 587 pax_align = align == 0 ? PAGE_SIZE : align; 588 l2 = ilog2(pax_align); 589 590 rand = cprng_fast32(); 591 #ifdef PAX_ASLR_DEBUG 592 if (pax_aslr_flags & PAX_ASLR_FIXED) 593 rand = pax_aslr_rand; 594 #endif 595 596 #define PAX_TRUNC(a, b) ((a) & ~((b) - 1)) 597 598 delta = PAX_ASLR_DELTA(rand, l2, PAX_ASLR_DELTA_EXEC_LEN); 599 offset = PAX_TRUNC(delta, pax_align); 600 offset = MAX(offset, pax_align); 601 602 PAX_DPRINTF("rand=%#x l2=%#zx pax_align=%#zx delta=%#zx offset=%#jx", 603 rand, l2, pax_align, delta, (uintmax_t)offset); 604 605 return offset; 606 } 607 608 vaddr_t 609 pax_aslr_exec_offset(struct exec_package *epp, vaddr_t align) 610 { 611 if (!pax_aslr_epp_active(epp)) 612 goto out; 613 614 #ifdef PAX_ASLR_DEBUG 615 if (pax_aslr_flags & PAX_ASLR_EXEC_OFFSET) 616 goto out; 617 #endif 618 return pax_aslr_offset(align); 619 out: 620 return 0; 621 } 622 623 voff_t 624 pax_aslr_rtld_offset(struct exec_package *epp, vaddr_t align, int use_topdown) 625 { 626 voff_t offset; 627 628 if (!pax_aslr_epp_active(epp)) 629 return 0; 630 631 #ifdef PAX_ASLR_DEBUG 632 if (pax_aslr_flags & PAX_ASLR_RTLD_OFFSET) 633 return 0; 634 #endif 635 offset = pax_aslr_offset(align); 636 if (use_topdown) 637 offset = -offset; 638 639 return offset; 640 } 641 642 void 643 pax_aslr_stack(struct exec_package *epp, vsize_t *max_stack_size) 644 { 645 if (!pax_aslr_epp_active(epp)) 646 return; 647 #ifdef PAX_ASLR_DEBUG 648 if (pax_aslr_flags & PAX_ASLR_STACK) 649 return; 650 #endif 651 652 uint32_t len = (epp->ep_flags & EXEC_32) ? 653 PAX_ASLR_DELTA_STACK_LEN32 : PAX_ASLR_DELTA_STACK_LEN; 654 uint32_t rand = cprng_fast32(); 655 #ifdef PAX_ASLR_DEBUG 656 if (pax_aslr_flags & PAX_ASLR_FIXED) 657 rand = pax_aslr_rand; 658 #endif 659 u_long d = PAX_ASLR_DELTA(rand, PAX_ASLR_DELTA_STACK_LSB, len); 660 d &= (*max_stack_size / PAX_ASLR_MAX_STACK_WASTE) - 1; 661 u_long newminsaddr = (u_long)STACK_GROW(epp->ep_minsaddr, d); 662 PAX_DPRINTF("old minsaddr=%#jx delta=%#lx new minsaddr=%#lx", 663 (uintmax_t)epp->ep_minsaddr, d, newminsaddr); 664 epp->ep_minsaddr = (vaddr_t)newminsaddr; 665 *max_stack_size -= d; 666 } 667 668 uint32_t 669 pax_aslr_stack_gap(struct exec_package *epp) 670 { 671 if (!pax_aslr_epp_active(epp)) 672 return 0; 673 674 #ifdef PAX_ASLR_DEBUG 675 if (pax_aslr_flags & PAX_ASLR_STACK_GAP) 676 return 0; 677 #endif 678 679 uint32_t rand = cprng_fast32(); 680 #ifdef PAX_ASLR_DEBUG 681 if (pax_aslr_flags & PAX_ASLR_FIXED) 682 rand = pax_aslr_rand; 683 #endif 684 rand %= PAGE_SIZE; 685 PAX_DPRINTF("stack gap=%#x\n", rand); 686 return rand; 687 } 688 #endif /* PAX_ASLR */ 689 690 #ifdef PAX_SEGVGUARD 691 static bool 692 pax_segvguard_elf_flags_active(uint32_t flags) 693 { 694 if (!pax_segvguard_enabled) 695 return false; 696 if (pax_segvguard_global && (flags & ELF_NOTE_PAX_NOGUARD) != 0) { 697 /* Segvguard explicitly disabled */ 698 return false; 699 } 700 if (!pax_segvguard_global && (flags & ELF_NOTE_PAX_GUARD) == 0) { 701 /* Segvguard not requested */ 702 return false; 703 } 704 return true; 705 } 706 707 static void 708 pax_segvguard_cleanup_cb(void *v) 709 { 710 struct pax_segvguard_entry *p = v; 711 struct pax_segvguard_uid_entry *up; 712 713 if (p == NULL) { 714 return; 715 } 716 while ((up = LIST_FIRST(&p->segv_uids)) != NULL) { 717 LIST_REMOVE(up, sue_list); 718 kmem_free(up, sizeof(*up)); 719 } 720 kmem_free(p, sizeof(*p)); 721 } 722 723 /* 724 * Called when a process of image vp generated a segfault. 725 */ 726 int 727 pax_segvguard(struct lwp *l, struct vnode *vp, const char *name, 728 bool crashed) 729 { 730 struct pax_segvguard_entry *p; 731 struct pax_segvguard_uid_entry *up; 732 struct timeval tv; 733 uid_t uid; 734 uint32_t flags; 735 bool have_uid; 736 737 flags = l->l_proc->p_pax; 738 if (!pax_flags_active(flags, P_PAX_GUARD)) 739 return 0; 740 741 if (vp == NULL) 742 return EFAULT; 743 744 /* Check if we already monitor the file. */ 745 p = fileassoc_lookup(vp, segvguard_id); 746 747 /* Fast-path if starting a program we don't know. */ 748 if (p == NULL && !crashed) 749 return 0; 750 751 microtime(&tv); 752 753 /* 754 * If a program we don't know crashed, we need to create a new entry 755 * for it. 756 */ 757 if (p == NULL) { 758 p = kmem_alloc(sizeof(*p), KM_SLEEP); 759 fileassoc_add(vp, segvguard_id, p); 760 LIST_INIT(&p->segv_uids); 761 762 /* 763 * Initialize a new entry with "crashes so far" of 1. 764 * The expiry time is when we purge the entry if it didn't 765 * reach the limit. 766 */ 767 up = kmem_alloc(sizeof(*up), KM_SLEEP); 768 up->sue_uid = kauth_cred_getuid(l->l_cred); 769 up->sue_ncrashes = 1; 770 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 771 up->sue_suspended = 0; 772 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 773 return 0; 774 } 775 776 /* 777 * A program we "know" either executed or crashed again. 778 * See if it's a culprit we're familiar with. 779 */ 780 uid = kauth_cred_getuid(l->l_cred); 781 have_uid = false; 782 LIST_FOREACH(up, &p->segv_uids, sue_list) { 783 if (up->sue_uid == uid) { 784 have_uid = true; 785 break; 786 } 787 } 788 789 /* 790 * It's someone else. Add an entry for him if we crashed. 791 */ 792 if (!have_uid) { 793 if (crashed) { 794 up = kmem_alloc(sizeof(*up), KM_SLEEP); 795 up->sue_uid = uid; 796 up->sue_ncrashes = 1; 797 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 798 up->sue_suspended = 0; 799 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 800 } 801 return 0; 802 } 803 804 if (crashed) { 805 /* Check if timer on previous crashes expired first. */ 806 if (up->sue_expiry < tv.tv_sec) { 807 log(LOG_INFO, "PaX Segvguard: [%s] Suspension" 808 " expired.\n", name ? name : "unknown"); 809 up->sue_ncrashes = 1; 810 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 811 up->sue_suspended = 0; 812 return 0; 813 } 814 815 up->sue_ncrashes++; 816 817 if (up->sue_ncrashes >= pax_segvguard_maxcrashes) { 818 log(LOG_ALERT, "PaX Segvguard: [%s] Suspending " 819 "execution for %d seconds after %zu crashes.\n", 820 name ? name : "unknown", pax_segvguard_suspension, 821 up->sue_ncrashes); 822 823 /* Suspend this program for a while. */ 824 up->sue_suspended = tv.tv_sec + pax_segvguard_suspension; 825 up->sue_ncrashes = 0; 826 up->sue_expiry = 0; 827 } 828 } else { 829 /* Are we supposed to be suspended? */ 830 if (up->sue_suspended > tv.tv_sec) { 831 log(LOG_ALERT, "PaX Segvguard: [%s] Preventing " 832 "execution due to repeated segfaults.\n", name ? 833 name : "unknown"); 834 return EPERM; 835 } 836 } 837 838 return 0; 839 } 840 #endif /* PAX_SEGVGUARD */ 841
Indexes created Sat Sep 20 22:09:52 GMT 2025