kern_pax.c revision 1.26.8.1
1 /* $NetBSD: kern_pax.c,v 1.26.8.1 2014/08/20 00:04:29 tls Exp $ */ 2 3 /*- 4 * Copyright (c) 2006 Elad Efrat <elad (at) NetBSD.org> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. The name of the author may not be used to endorse or promote products 16 * derived from this software without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 #include <sys/cdefs.h> 31 __KERNEL_RCSID(0, "$NetBSD: kern_pax.c,v 1.26.8.1 2014/08/20 00:04:29 tls Exp $"); 32 33 #include "opt_pax.h" 34 35 #include <sys/param.h> 36 #include <sys/proc.h> 37 #include <sys/exec_elf.h> 38 #include <sys/pax.h> 39 #include <sys/sysctl.h> 40 #include <sys/kmem.h> 41 #include <sys/fileassoc.h> 42 #include <sys/syslog.h> 43 #include <sys/vnode.h> 44 #include <sys/queue.h> 45 #include <sys/kauth.h> 46 #include <sys/cprng.h> 47 48 #ifdef PAX_ASLR 49 #include <sys/mman.h> 50 #include <sys/rnd.h> 51 #include <sys/exec.h> 52 53 int pax_aslr_enabled = 1; 54 int pax_aslr_global = PAX_ASLR; 55 56 #ifndef PAX_ASLR_DELTA_MMAP_LSB 57 #define PAX_ASLR_DELTA_MMAP_LSB PGSHIFT 58 #endif 59 #ifndef PAX_ASLR_DELTA_MMAP_LEN 60 #define PAX_ASLR_DELTA_MMAP_LEN ((sizeof(void *) * NBBY) / 2) 61 #endif 62 #ifndef PAX_ASLR_DELTA_STACK_LSB 63 #define PAX_ASLR_DELTA_STACK_LSB PGSHIFT 64 #endif 65 #ifndef PAX_ASLR_DELTA_STACK_LEN 66 #define PAX_ASLR_DELTA_STACK_LEN 12 67 #endif 68 69 #endif /* PAX_ASLR */ 70 71 #ifdef PAX_MPROTECT 72 static int pax_mprotect_enabled = 1; 73 static int pax_mprotect_global = PAX_MPROTECT; 74 #endif /* PAX_MPROTECT */ 75 76 #ifdef PAX_SEGVGUARD 77 #ifndef PAX_SEGVGUARD_EXPIRY 78 #define PAX_SEGVGUARD_EXPIRY (2 * 60) 79 #endif 80 81 #ifndef PAX_SEGVGUARD_SUSPENSION 82 #define PAX_SEGVGUARD_SUSPENSION (10 * 60) 83 #endif 84 85 #ifndef PAX_SEGVGUARD_MAXCRASHES 86 #define PAX_SEGVGUARD_MAXCRASHES 5 87 #endif 88 89 static int pax_segvguard_enabled = 1; 90 static int pax_segvguard_global = PAX_SEGVGUARD; 91 static int pax_segvguard_expiry = PAX_SEGVGUARD_EXPIRY; 92 static int pax_segvguard_suspension = PAX_SEGVGUARD_SUSPENSION; 93 static int pax_segvguard_maxcrashes = PAX_SEGVGUARD_MAXCRASHES; 94 95 static fileassoc_t segvguard_id; 96 97 struct pax_segvguard_uid_entry { 98 uid_t sue_uid; 99 size_t sue_ncrashes; 100 time_t sue_expiry; 101 time_t sue_suspended; 102 LIST_ENTRY(pax_segvguard_uid_entry) sue_list; 103 }; 104 105 struct pax_segvguard_entry { 106 LIST_HEAD(, pax_segvguard_uid_entry) segv_uids; 107 }; 108 109 static void pax_segvguard_cb(void *); 110 #endif /* PAX_SEGVGUARD */ 111 112 /* PaX internal setspecific flags */ 113 #define PAX_MPROTECT_EXPLICIT_ENABLE (void *)0x01 114 #define PAX_MPROTECT_EXPLICIT_DISABLE (void *)0x02 115 #define PAX_SEGVGUARD_EXPLICIT_ENABLE (void *)0x03 116 #define PAX_SEGVGUARD_EXPLICIT_DISABLE (void *)0x04 117 #define PAX_ASLR_EXPLICIT_ENABLE (void *)0x05 118 #define PAX_ASLR_EXPLICIT_DISABLE (void *)0x06 119 120 SYSCTL_SETUP(sysctl_security_pax_setup, "sysctl security.pax setup") 121 { 122 const struct sysctlnode *rnode = NULL, *cnode; 123 124 sysctl_createv(clog, 0, NULL, &rnode, 125 CTLFLAG_PERMANENT, 126 CTLTYPE_NODE, "pax", 127 SYSCTL_DESCR("PaX (exploit mitigation) features."), 128 NULL, 0, NULL, 0, 129 CTL_SECURITY, CTL_CREATE, CTL_EOL); 130 131 cnode = rnode; 132 133 #ifdef PAX_MPROTECT 134 rnode = cnode; 135 sysctl_createv(clog, 0, &rnode, &rnode, 136 CTLFLAG_PERMANENT, 137 CTLTYPE_NODE, "mprotect", 138 SYSCTL_DESCR("mprotect(2) W^X restrictions."), 139 NULL, 0, NULL, 0, 140 CTL_CREATE, CTL_EOL); 141 sysctl_createv(clog, 0, &rnode, NULL, 142 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 143 CTLTYPE_INT, "enabled", 144 SYSCTL_DESCR("Restrictions enabled."), 145 NULL, 0, &pax_mprotect_enabled, 0, 146 CTL_CREATE, CTL_EOL); 147 sysctl_createv(clog, 0, &rnode, NULL, 148 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 149 CTLTYPE_INT, "global", 150 SYSCTL_DESCR("When enabled, unless explicitly " 151 "specified, apply restrictions to " 152 "all processes."), 153 NULL, 0, &pax_mprotect_global, 0, 154 CTL_CREATE, CTL_EOL); 155 #endif /* PAX_MPROTECT */ 156 157 #ifdef PAX_SEGVGUARD 158 rnode = cnode; 159 sysctl_createv(clog, 0, &rnode, &rnode, 160 CTLFLAG_PERMANENT, 161 CTLTYPE_NODE, "segvguard", 162 SYSCTL_DESCR("PaX segvguard."), 163 NULL, 0, NULL, 0, 164 CTL_CREATE, CTL_EOL); 165 sysctl_createv(clog, 0, &rnode, NULL, 166 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 167 CTLTYPE_INT, "enabled", 168 SYSCTL_DESCR("segvguard enabled."), 169 NULL, 0, &pax_segvguard_enabled, 0, 170 CTL_CREATE, CTL_EOL); 171 sysctl_createv(clog, 0, &rnode, NULL, 172 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 173 CTLTYPE_INT, "global", 174 SYSCTL_DESCR("segvguard all programs."), 175 NULL, 0, &pax_segvguard_global, 0, 176 CTL_CREATE, CTL_EOL); 177 sysctl_createv(clog, 0, &rnode, NULL, 178 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 179 CTLTYPE_INT, "expiry_timeout", 180 SYSCTL_DESCR("Entry expiry timeout (in seconds)."), 181 NULL, 0, &pax_segvguard_expiry, 0, 182 CTL_CREATE, CTL_EOL); 183 sysctl_createv(clog, 0, &rnode, NULL, 184 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 185 CTLTYPE_INT, "suspend_timeout", 186 SYSCTL_DESCR("Entry suspension timeout (in seconds)."), 187 NULL, 0, &pax_segvguard_suspension, 0, 188 CTL_CREATE, CTL_EOL); 189 sysctl_createv(clog, 0, &rnode, NULL, 190 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 191 CTLTYPE_INT, "max_crashes", 192 SYSCTL_DESCR("Max number of crashes before expiry."), 193 NULL, 0, &pax_segvguard_maxcrashes, 0, 194 CTL_CREATE, CTL_EOL); 195 #endif /* PAX_SEGVGUARD */ 196 197 #ifdef PAX_ASLR 198 rnode = cnode; 199 sysctl_createv(clog, 0, &rnode, &rnode, 200 CTLFLAG_PERMANENT, 201 CTLTYPE_NODE, "aslr", 202 SYSCTL_DESCR("Address Space Layout Randomization."), 203 NULL, 0, NULL, 0, 204 CTL_CREATE, CTL_EOL); 205 sysctl_createv(clog, 0, &rnode, NULL, 206 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 207 CTLTYPE_INT, "enabled", 208 SYSCTL_DESCR("Restrictions enabled."), 209 NULL, 0, &pax_aslr_enabled, 0, 210 CTL_CREATE, CTL_EOL); 211 sysctl_createv(clog, 0, &rnode, NULL, 212 CTLFLAG_PERMANENT|CTLFLAG_READWRITE, 213 CTLTYPE_INT, "global", 214 SYSCTL_DESCR("When enabled, unless explicitly " 215 "specified, apply to all processes."), 216 NULL, 0, &pax_aslr_global, 0, 217 CTL_CREATE, CTL_EOL); 218 sysctl_createv(clog, 0, &rnode, NULL, 219 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 220 CTLTYPE_INT, "mmap_len", 221 SYSCTL_DESCR("Number of bits randomized for " 222 "mmap(2) calls."), 223 NULL, PAX_ASLR_DELTA_MMAP_LEN, NULL, 0, 224 CTL_CREATE, CTL_EOL); 225 sysctl_createv(clog, 0, &rnode, NULL, 226 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 227 CTLTYPE_INT, "stack_len", 228 SYSCTL_DESCR("Number of bits randomized for " 229 "the stack."), 230 NULL, PAX_ASLR_DELTA_STACK_LEN, NULL, 0, 231 CTL_CREATE, CTL_EOL); 232 sysctl_createv(clog, 0, &rnode, NULL, 233 CTLFLAG_PERMANENT|CTLFLAG_IMMEDIATE, 234 CTLTYPE_INT, "exec_len", 235 SYSCTL_DESCR("Number of bits randomized for " 236 "the PIE exec base."), 237 NULL, PAX_ASLR_DELTA_EXEC_LEN, NULL, 0, 238 CTL_CREATE, CTL_EOL); 239 240 #endif /* PAX_ASLR */ 241 } 242 243 /* 244 * Initialize PaX. 245 */ 246 void 247 pax_init(void) 248 { 249 #ifdef PAX_SEGVGUARD 250 int error; 251 #endif /* PAX_SEGVGUARD */ 252 253 #ifdef PAX_SEGVGUARD 254 error = fileassoc_register("segvguard", pax_segvguard_cb, 255 &segvguard_id); 256 if (error) { 257 panic("pax_init: segvguard_id: error=%d\n", error); 258 } 259 #endif /* PAX_SEGVGUARD */ 260 } 261 262 #ifdef PAX_MPROTECT 263 void 264 pax_mprotect(struct lwp *l, vm_prot_t *prot, vm_prot_t *maxprot) 265 { 266 uint32_t f; 267 268 if (!pax_mprotect_enabled) 269 return; 270 271 f = l->l_proc->p_pax; 272 if ((pax_mprotect_global && (f & ELF_NOTE_PAX_NOMPROTECT) != 0) || 273 (!pax_mprotect_global && (f & ELF_NOTE_PAX_MPROTECT) == 0)) 274 return; 275 276 if ((*prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) != VM_PROT_EXECUTE) { 277 *prot &= ~VM_PROT_EXECUTE; 278 *maxprot &= ~VM_PROT_EXECUTE; 279 } else { 280 *prot &= ~VM_PROT_WRITE; 281 *maxprot &= ~VM_PROT_WRITE; 282 } 283 } 284 #endif /* PAX_MPROTECT */ 285 286 #ifdef PAX_ASLR 287 bool 288 pax_aslr_active(struct lwp *l) 289 { 290 uint32_t f; 291 292 if (!pax_aslr_enabled) 293 return false; 294 295 f = l->l_proc->p_pax; 296 if ((pax_aslr_global && (f & ELF_NOTE_PAX_NOASLR) != 0) || 297 (!pax_aslr_global && (f & ELF_NOTE_PAX_ASLR) == 0)) 298 return false; 299 return true; 300 } 301 302 void 303 pax_aslr_init(struct lwp *l, struct vmspace *vm) 304 { 305 if (!pax_aslr_active(l)) 306 return; 307 308 vm->vm_aslr_delta_mmap = PAX_ASLR_DELTA(cprng_fast32(), 309 PAX_ASLR_DELTA_MMAP_LSB, PAX_ASLR_DELTA_MMAP_LEN); 310 } 311 312 void 313 pax_aslr(struct lwp *l, vaddr_t *addr, vaddr_t orig_addr, int f) 314 { 315 if (!pax_aslr_active(l)) 316 return; 317 318 if (!(f & MAP_FIXED) && ((orig_addr == 0) || !(f & MAP_ANON))) { 319 #ifdef PAX_ASLR_DEBUG 320 uprintf("applying to 0x%lx orig_addr=0x%lx f=%x\n", 321 (unsigned long)*addr, (unsigned long)orig_addr, f); 322 #endif 323 if (!(l->l_proc->p_vmspace->vm_map.flags & VM_MAP_TOPDOWN)) 324 *addr += l->l_proc->p_vmspace->vm_aslr_delta_mmap; 325 else 326 *addr -= l->l_proc->p_vmspace->vm_aslr_delta_mmap; 327 #ifdef PAX_ASLR_DEBUG 328 uprintf("result 0x%lx\n", *addr); 329 #endif 330 } 331 #ifdef PAX_ASLR_DEBUG 332 else 333 uprintf("not applying to 0x%lx orig_addr=0x%lx f=%x\n", 334 (unsigned long)*addr, (unsigned long)orig_addr, f); 335 #endif 336 } 337 338 void 339 pax_aslr_stack(struct lwp *l, struct exec_package *epp, u_long *max_stack_size) 340 { 341 if (pax_aslr_active(l)) { 342 u_long d = PAX_ASLR_DELTA(cprng_fast32(), 343 PAX_ASLR_DELTA_STACK_LSB, 344 PAX_ASLR_DELTA_STACK_LEN); 345 #ifdef PAX_ASLR_DEBUG 346 uprintf("stack 0x%lx d=0x%lx 0x%lx\n", 347 epp->ep_minsaddr, d, epp->ep_minsaddr - d); 348 #endif 349 epp->ep_minsaddr -= d; 350 *max_stack_size -= d; 351 if (epp->ep_ssize > *max_stack_size) 352 epp->ep_ssize = *max_stack_size; 353 } 354 } 355 #endif /* PAX_ASLR */ 356 357 #ifdef PAX_SEGVGUARD 358 static void 359 pax_segvguard_cb(void *v) 360 { 361 struct pax_segvguard_entry *p = v; 362 struct pax_segvguard_uid_entry *up; 363 364 if (p == NULL) { 365 return; 366 } 367 while ((up = LIST_FIRST(&p->segv_uids)) != NULL) { 368 LIST_REMOVE(up, sue_list); 369 kmem_free(up, sizeof(*up)); 370 } 371 kmem_free(p, sizeof(*p)); 372 } 373 374 /* 375 * Called when a process of image vp generated a segfault. 376 */ 377 int 378 pax_segvguard(struct lwp *l, struct vnode *vp, const char *name, 379 bool crashed) 380 { 381 struct pax_segvguard_entry *p; 382 struct pax_segvguard_uid_entry *up; 383 struct timeval tv; 384 uid_t uid; 385 uint32_t f; 386 bool have_uid; 387 388 if (!pax_segvguard_enabled) 389 return (0); 390 391 f = l->l_proc->p_pax; 392 if ((pax_segvguard_global && (f & ELF_NOTE_PAX_NOGUARD) != 0) || 393 (!pax_segvguard_global && (f & ELF_NOTE_PAX_GUARD) == 0)) 394 return (0); 395 396 if (vp == NULL) 397 return (EFAULT); 398 399 /* Check if we already monitor the file. */ 400 p = fileassoc_lookup(vp, segvguard_id); 401 402 /* Fast-path if starting a program we don't know. */ 403 if (p == NULL && !crashed) 404 return (0); 405 406 microtime(&tv); 407 408 /* 409 * If a program we don't know crashed, we need to create a new entry 410 * for it. 411 */ 412 if (p == NULL) { 413 p = kmem_alloc(sizeof(*p), KM_SLEEP); 414 fileassoc_add(vp, segvguard_id, p); 415 LIST_INIT(&p->segv_uids); 416 417 /* 418 * Initialize a new entry with "crashes so far" of 1. 419 * The expiry time is when we purge the entry if it didn't 420 * reach the limit. 421 */ 422 up = kmem_alloc(sizeof(*up), KM_SLEEP); 423 up->sue_uid = kauth_cred_getuid(l->l_cred); 424 up->sue_ncrashes = 1; 425 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 426 up->sue_suspended = 0; 427 428 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 429 430 return (0); 431 } 432 433 /* 434 * A program we "know" either executed or crashed again. 435 * See if it's a culprit we're familiar with. 436 */ 437 uid = kauth_cred_getuid(l->l_cred); 438 have_uid = false; 439 LIST_FOREACH(up, &p->segv_uids, sue_list) { 440 if (up->sue_uid == uid) { 441 have_uid = true; 442 break; 443 } 444 } 445 446 /* 447 * It's someone else. Add an entry for him if we crashed. 448 */ 449 if (!have_uid) { 450 if (crashed) { 451 up = kmem_alloc(sizeof(*up), KM_SLEEP); 452 up->sue_uid = uid; 453 up->sue_ncrashes = 1; 454 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 455 up->sue_suspended = 0; 456 457 LIST_INSERT_HEAD(&p->segv_uids, up, sue_list); 458 } 459 return (0); 460 } 461 462 if (crashed) { 463 /* Check if timer on previous crashes expired first. */ 464 if (up->sue_expiry < tv.tv_sec) { 465 log(LOG_INFO, "PaX Segvguard: [%s] Suspension" 466 " expired.\n", name ? name : "unknown"); 467 468 up->sue_ncrashes = 1; 469 up->sue_expiry = tv.tv_sec + pax_segvguard_expiry; 470 up->sue_suspended = 0; 471 472 return (0); 473 } 474 475 up->sue_ncrashes++; 476 477 if (up->sue_ncrashes >= pax_segvguard_maxcrashes) { 478 log(LOG_ALERT, "PaX Segvguard: [%s] Suspending " 479 "execution for %d seconds after %zu crashes.\n", 480 name ? name : "unknown", pax_segvguard_suspension, 481 up->sue_ncrashes); 482 483 /* Suspend this program for a while. */ 484 up->sue_suspended = tv.tv_sec + pax_segvguard_suspension; 485 up->sue_ncrashes = 0; 486 up->sue_expiry = 0; 487 } 488 } else { 489 /* Are we supposed to be suspended? */ 490 if (up->sue_suspended > tv.tv_sec) { 491 log(LOG_ALERT, "PaX Segvguard: [%s] Preventing " 492 "execution due to repeated segfaults.\n", name ? 493 name : "unknown"); 494 495 return (EPERM); 496 } 497 } 498 499 return (0); 500 } 501 #endif /* PAX_SEGVGUARD */ 502
Indexes created Tue Sep 30 11:09:46 GMT 2025