1 /* 2 * Copyright (C) 2008 IBM Corporation 3 * Author: Mimi Zohar <zohar@us.ibm.com> 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation, version 2 of the License. 8 * 9 * ima_policy.c 10 * - initialize default measure policy rules 11 * 12 */ 13 #include <linux/module.h> 14 #include <linux/list.h> 15 #include <linux/security.h> 16 #include <linux/magic.h> 17 #include <linux/parser.h> 18 #include <linux/slab.h> 19 20 #include "ima.h" 21 22 /* flags definitions */ 23 #define IMA_FUNC 0x0001 24 #define IMA_MASK 0x0002 25 #define IMA_FSMAGIC 0x0004 26 #define IMA_UID 0x0008 27 #define IMA_FOWNER 0x0010 28 29 #define UNKNOWN 0 30 #define MEASURE 0x0001 /* same as IMA_MEASURE */ 31 #define DONT_MEASURE 0x0002 32 #define APPRAISE 0x0004 /* same as IMA_APPRAISE */ 33 #define DONT_APPRAISE 0x0008 34 #define AUDIT 0x0040 35 36 #define MAX_LSM_RULES 6 37 enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE, 38 LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE 39 }; 40 41 struct ima_rule_entry { 42 struct list_head list; 43 int action; 44 unsigned int flags; 45 enum ima_hooks func; 46 int mask; 47 unsigned long fsmagic; 48 kuid_t uid; 49 kuid_t fowner; 50 struct { 51 void *rule; /* LSM file metadata specific */ 52 int type; /* audit type */ 53 } lsm[MAX_LSM_RULES]; 54 }; 55 56 /* 57 * Without LSM specific knowledge, the default policy can only be 58 * written in terms of .action, .func, .mask, .fsmagic, .uid, and .fowner 59 */ 60 61 /* 62 * The minimum rule set to allow for full TCB coverage. Measures all files 63 * opened or mmap for exec and everything read by root. Dangerous because 64 * normal users can easily run the machine out of memory simply building 65 * and running executables. 66 */ 67 static struct ima_rule_entry default_rules[] = { 68 {.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,.flags = IMA_FSMAGIC}, 69 {.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC}, 70 {.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC}, 71 {.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC}, 72 {.action = DONT_MEASURE,.fsmagic = RAMFS_MAGIC,.flags = IMA_FSMAGIC}, 73 {.action = DONT_MEASURE,.fsmagic = DEVPTS_SUPER_MAGIC,.flags = IMA_FSMAGIC}, 74 {.action = DONT_MEASURE,.fsmagic = BINFMTFS_MAGIC,.flags = IMA_FSMAGIC}, 75 {.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,.flags = IMA_FSMAGIC}, 76 {.action = DONT_MEASURE,.fsmagic = SELINUX_MAGIC,.flags = IMA_FSMAGIC}, 77 {.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC, 78 .flags = IMA_FUNC | IMA_MASK}, 79 {.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC, 80 .flags = IMA_FUNC | IMA_MASK}, 81 {.action = MEASURE,.func = FILE_CHECK,.mask = MAY_READ,.uid = GLOBAL_ROOT_UID, 82 .flags = IMA_FUNC | IMA_MASK | IMA_UID}, 83 {.action = MEASURE,.func = MODULE_CHECK, .flags = IMA_FUNC}, 84 }; 85 86 static struct ima_rule_entry default_appraise_rules[] = { 87 {.action = DONT_APPRAISE,.fsmagic = PROC_SUPER_MAGIC,.flags = IMA_FSMAGIC}, 88 {.action = DONT_APPRAISE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC}, 89 {.action = DONT_APPRAISE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC}, 90 {.action = DONT_APPRAISE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC}, 91 {.action = DONT_APPRAISE,.fsmagic = RAMFS_MAGIC,.flags = IMA_FSMAGIC}, 92 {.action = DONT_APPRAISE,.fsmagic = DEVPTS_SUPER_MAGIC,.flags = IMA_FSMAGIC}, 93 {.action = DONT_APPRAISE,.fsmagic = BINFMTFS_MAGIC,.flags = IMA_FSMAGIC}, 94 {.action = DONT_APPRAISE,.fsmagic = SECURITYFS_MAGIC,.flags = IMA_FSMAGIC}, 95 {.action = DONT_APPRAISE,.fsmagic = SELINUX_MAGIC,.flags = IMA_FSMAGIC}, 96 {.action = DONT_APPRAISE,.fsmagic = CGROUP_SUPER_MAGIC,.flags = IMA_FSMAGIC}, 97 {.action = APPRAISE,.fowner = GLOBAL_ROOT_UID,.flags = IMA_FOWNER}, 98 }; 99 100 static LIST_HEAD(ima_default_rules); 101 static LIST_HEAD(ima_policy_rules); 102 static struct list_head *ima_rules; 103 104 static DEFINE_MUTEX(ima_rules_mutex); 105 106 static bool ima_use_tcb __initdata; 107 static int __init default_measure_policy_setup(char *str) 108 { 109 ima_use_tcb = 1; 110 return 1; 111 } 112 __setup("ima_tcb", default_measure_policy_setup); 113 114 static bool ima_use_appraise_tcb __initdata; 115 static int __init default_appraise_policy_setup(char *str) 116 { 117 ima_use_appraise_tcb = 1; 118 return 1; 119 } 120 __setup("ima_appraise_tcb", default_appraise_policy_setup); 121 122 /** 123 * ima_match_rules - determine whether an inode matches the measure rule. 124 * @rule: a pointer to a rule 125 * @inode: a pointer to an inode 126 * @func: LIM hook identifier 127 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) 128 * 129 * Returns true on rule match, false on failure. 130 */ 131 static bool ima_match_rules(struct ima_rule_entry *rule, 132 struct inode *inode, enum ima_hooks func, int mask) 133 { 134 struct task_struct *tsk = current; 135 const struct cred *cred = current_cred(); 136 int i; 137 138 if ((rule->flags & IMA_FUNC) && rule->func != func) 139 return false; 140 if ((rule->flags & IMA_MASK) && rule->mask != mask) 141 return false; 142 if ((rule->flags & IMA_FSMAGIC) 143 && rule->fsmagic != inode->i_sb->s_magic) 144 return false; 145 if ((rule->flags & IMA_UID) && !uid_eq(rule->uid, cred->uid)) 146 return false; 147 if ((rule->flags & IMA_FOWNER) && !uid_eq(rule->fowner, inode->i_uid)) 148 return false; 149 for (i = 0; i < MAX_LSM_RULES; i++) { 150 int rc = 0; 151 u32 osid, sid; 152 153 if (!rule->lsm[i].rule) 154 continue; 155 156 switch (i) { 157 case LSM_OBJ_USER: 158 case LSM_OBJ_ROLE: 159 case LSM_OBJ_TYPE: 160 security_inode_getsecid(inode, &osid); 161 rc = security_filter_rule_match(osid, 162 rule->lsm[i].type, 163 Audit_equal, 164 rule->lsm[i].rule, 165 NULL); 166 break; 167 case LSM_SUBJ_USER: 168 case LSM_SUBJ_ROLE: 169 case LSM_SUBJ_TYPE: 170 security_task_getsecid(tsk, &sid); 171 rc = security_filter_rule_match(sid, 172 rule->lsm[i].type, 173 Audit_equal, 174 rule->lsm[i].rule, 175 NULL); 176 default: 177 break; 178 } 179 if (!rc) 180 return false; 181 } 182 return true; 183 } 184 185 /** 186 * ima_match_policy - decision based on LSM and other conditions 187 * @inode: pointer to an inode for which the policy decision is being made 188 * @func: IMA hook identifier 189 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) 190 * 191 * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type) 192 * conditions. 193 * 194 * (There is no need for locking when walking the policy list, 195 * as elements in the list are never deleted, nor does the list 196 * change.) 197 */ 198 int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask, 199 int flags) 200 { 201 struct ima_rule_entry *entry; 202 int action = 0, actmask = flags | (flags << 1); 203 204 list_for_each_entry(entry, ima_rules, list) { 205 206 if (!(entry->action & actmask)) 207 continue; 208 209 if (!ima_match_rules(entry, inode, func, mask)) 210 continue; 211 212 action |= entry->action & IMA_DO_MASK; 213 if (entry->action & IMA_DO_MASK) 214 actmask &= ~(entry->action | entry->action << 1); 215 else 216 actmask &= ~(entry->action | entry->action >> 1); 217 218 if (!actmask) 219 break; 220 } 221 222 return action; 223 } 224 225 /** 226 * ima_init_policy - initialize the default measure rules. 227 * 228 * ima_rules points to either the ima_default_rules or the 229 * the new ima_policy_rules. 230 */ 231 void __init ima_init_policy(void) 232 { 233 int i, measure_entries, appraise_entries; 234 235 /* if !ima_use_tcb set entries = 0 so we load NO default rules */ 236 measure_entries = ima_use_tcb ? ARRAY_SIZE(default_rules) : 0; 237 appraise_entries = ima_use_appraise_tcb ? 238 ARRAY_SIZE(default_appraise_rules) : 0; 239 240 for (i = 0; i < measure_entries + appraise_entries; i++) { 241 if (i < measure_entries) 242 list_add_tail(&default_rules[i].list, 243 &ima_default_rules); 244 else { 245 int j = i - measure_entries; 246 247 list_add_tail(&default_appraise_rules[j].list, 248 &ima_default_rules); 249 } 250 } 251 252 ima_rules = &ima_default_rules; 253 } 254 255 /** 256 * ima_update_policy - update default_rules with new measure rules 257 * 258 * Called on file .release to update the default rules with a complete new 259 * policy. Once updated, the policy is locked, no additional rules can be 260 * added to the policy. 261 */ 262 void ima_update_policy(void) 263 { 264 const char *op = "policy_update"; 265 const char *cause = "already exists"; 266 int result = 1; 267 int audit_info = 0; 268 269 if (ima_rules == &ima_default_rules) { 270 ima_rules = &ima_policy_rules; 271 cause = "complete"; 272 result = 0; 273 } 274 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 275 NULL, op, cause, result, audit_info); 276 } 277 278 enum { 279 Opt_err = -1, 280 Opt_measure = 1, Opt_dont_measure, 281 Opt_appraise, Opt_dont_appraise, 282 Opt_audit, 283 Opt_obj_user, Opt_obj_role, Opt_obj_type, 284 Opt_subj_user, Opt_subj_role, Opt_subj_type, 285 Opt_func, Opt_mask, Opt_fsmagic, Opt_uid, Opt_fowner 286 }; 287 288 static match_table_t policy_tokens = { 289 {Opt_measure, "measure"}, 290 {Opt_dont_measure, "dont_measure"}, 291 {Opt_appraise, "appraise"}, 292 {Opt_dont_appraise, "dont_appraise"}, 293 {Opt_audit, "audit"}, 294 {Opt_obj_user, "obj_user=%s"}, 295 {Opt_obj_role, "obj_role=%s"}, 296 {Opt_obj_type, "obj_type=%s"}, 297 {Opt_subj_user, "subj_user=%s"}, 298 {Opt_subj_role, "subj_role=%s"}, 299 {Opt_subj_type, "subj_type=%s"}, 300 {Opt_func, "func=%s"}, 301 {Opt_mask, "mask=%s"}, 302 {Opt_fsmagic, "fsmagic=%s"}, 303 {Opt_uid, "uid=%s"}, 304 {Opt_fowner, "fowner=%s"}, 305 {Opt_err, NULL} 306 }; 307 308 static int ima_lsm_rule_init(struct ima_rule_entry *entry, 309 char *args, int lsm_rule, int audit_type) 310 { 311 int result; 312 313 if (entry->lsm[lsm_rule].rule) 314 return -EINVAL; 315 316 entry->lsm[lsm_rule].type = audit_type; 317 result = security_filter_rule_init(entry->lsm[lsm_rule].type, 318 Audit_equal, args, 319 &entry->lsm[lsm_rule].rule); 320 if (!entry->lsm[lsm_rule].rule) 321 return -EINVAL; 322 return result; 323 } 324 325 static void ima_log_string(struct audit_buffer *ab, char *key, char *value) 326 { 327 audit_log_format(ab, "%s=", key); 328 audit_log_untrustedstring(ab, value); 329 audit_log_format(ab, " "); 330 } 331 332 static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) 333 { 334 struct audit_buffer *ab; 335 char *p; 336 int result = 0; 337 338 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE); 339 340 entry->uid = INVALID_UID; 341 entry->fowner = INVALID_UID; 342 entry->action = UNKNOWN; 343 while ((p = strsep(&rule, " \t")) != NULL) { 344 substring_t args[MAX_OPT_ARGS]; 345 int token; 346 unsigned long lnum; 347 348 if (result < 0) 349 break; 350 if ((*p == '\0') || (*p == ' ') || (*p == '\t')) 351 continue; 352 token = match_token(p, policy_tokens, args); 353 switch (token) { 354 case Opt_measure: 355 ima_log_string(ab, "action", "measure"); 356 357 if (entry->action != UNKNOWN) 358 result = -EINVAL; 359 360 entry->action = MEASURE; 361 break; 362 case Opt_dont_measure: 363 ima_log_string(ab, "action", "dont_measure"); 364 365 if (entry->action != UNKNOWN) 366 result = -EINVAL; 367 368 entry->action = DONT_MEASURE; 369 break; 370 case Opt_appraise: 371 ima_log_string(ab, "action", "appraise"); 372 373 if (entry->action != UNKNOWN) 374 result = -EINVAL; 375 376 entry->action = APPRAISE; 377 break; 378 case Opt_dont_appraise: 379 ima_log_string(ab, "action", "dont_appraise"); 380 381 if (entry->action != UNKNOWN) 382 result = -EINVAL; 383 384 entry->action = DONT_APPRAISE; 385 break; 386 case Opt_audit: 387 ima_log_string(ab, "action", "audit"); 388 389 if (entry->action != UNKNOWN) 390 result = -EINVAL; 391 392 entry->action = AUDIT; 393 break; 394 case Opt_func: 395 ima_log_string(ab, "func", args[0].from); 396 397 if (entry->func) 398 result = -EINVAL; 399 400 if (strcmp(args[0].from, "FILE_CHECK") == 0) 401 entry->func = FILE_CHECK; 402 /* PATH_CHECK is for backwards compat */ 403 else if (strcmp(args[0].from, "PATH_CHECK") == 0) 404 entry->func = FILE_CHECK; 405 else if (strcmp(args[0].from, "MODULE_CHECK") == 0) 406 entry->func = MODULE_CHECK; 407 else if (strcmp(args[0].from, "FILE_MMAP") == 0) 408 entry->func = FILE_MMAP; 409 else if (strcmp(args[0].from, "BPRM_CHECK") == 0) 410 entry->func = BPRM_CHECK; 411 else 412 result = -EINVAL; 413 if (!result) 414 entry->flags |= IMA_FUNC; 415 break; 416 case Opt_mask: 417 ima_log_string(ab, "mask", args[0].from); 418 419 if (entry->mask) 420 result = -EINVAL; 421 422 if ((strcmp(args[0].from, "MAY_EXEC")) == 0) 423 entry->mask = MAY_EXEC; 424 else if (strcmp(args[0].from, "MAY_WRITE") == 0) 425 entry->mask = MAY_WRITE; 426 else if (strcmp(args[0].from, "MAY_READ") == 0) 427 entry->mask = MAY_READ; 428 else if (strcmp(args[0].from, "MAY_APPEND") == 0) 429 entry->mask = MAY_APPEND; 430 else 431 result = -EINVAL; 432 if (!result) 433 entry->flags |= IMA_MASK; 434 break; 435 case Opt_fsmagic: 436 ima_log_string(ab, "fsmagic", args[0].from); 437 438 if (entry->fsmagic) { 439 result = -EINVAL; 440 break; 441 } 442 443 result = strict_strtoul(args[0].from, 16, 444 &entry->fsmagic); 445 if (!result) 446 entry->flags |= IMA_FSMAGIC; 447 break; 448 case Opt_uid: 449 ima_log_string(ab, "uid", args[0].from); 450 451 if (uid_valid(entry->uid)) { 452 result = -EINVAL; 453 break; 454 } 455 456 result = strict_strtoul(args[0].from, 10, &lnum); 457 if (!result) { 458 entry->uid = make_kuid(current_user_ns(), (uid_t)lnum); 459 if (!uid_valid(entry->uid) || (((uid_t)lnum) != lnum)) 460 result = -EINVAL; 461 else 462 entry->flags |= IMA_UID; 463 } 464 break; 465 case Opt_fowner: 466 ima_log_string(ab, "fowner", args[0].from); 467 468 if (uid_valid(entry->fowner)) { 469 result = -EINVAL; 470 break; 471 } 472 473 result = strict_strtoul(args[0].from, 10, &lnum); 474 if (!result) { 475 entry->fowner = make_kuid(current_user_ns(), (uid_t)lnum); 476 if (!uid_valid(entry->fowner) || (((uid_t)lnum) != lnum)) 477 result = -EINVAL; 478 else 479 entry->flags |= IMA_FOWNER; 480 } 481 break; 482 case Opt_obj_user: 483 ima_log_string(ab, "obj_user", args[0].from); 484 result = ima_lsm_rule_init(entry, args[0].from, 485 LSM_OBJ_USER, 486 AUDIT_OBJ_USER); 487 break; 488 case Opt_obj_role: 489 ima_log_string(ab, "obj_role", args[0].from); 490 result = ima_lsm_rule_init(entry, args[0].from, 491 LSM_OBJ_ROLE, 492 AUDIT_OBJ_ROLE); 493 break; 494 case Opt_obj_type: 495 ima_log_string(ab, "obj_type", args[0].from); 496 result = ima_lsm_rule_init(entry, args[0].from, 497 LSM_OBJ_TYPE, 498 AUDIT_OBJ_TYPE); 499 break; 500 case Opt_subj_user: 501 ima_log_string(ab, "subj_user", args[0].from); 502 result = ima_lsm_rule_init(entry, args[0].from, 503 LSM_SUBJ_USER, 504 AUDIT_SUBJ_USER); 505 break; 506 case Opt_subj_role: 507 ima_log_string(ab, "subj_role", args[0].from); 508 result = ima_lsm_rule_init(entry, args[0].from, 509 LSM_SUBJ_ROLE, 510 AUDIT_SUBJ_ROLE); 511 break; 512 case Opt_subj_type: 513 ima_log_string(ab, "subj_type", args[0].from); 514 result = ima_lsm_rule_init(entry, args[0].from, 515 LSM_SUBJ_TYPE, 516 AUDIT_SUBJ_TYPE); 517 break; 518 case Opt_err: 519 ima_log_string(ab, "UNKNOWN", p); 520 result = -EINVAL; 521 break; 522 } 523 } 524 if (!result && (entry->action == UNKNOWN)) 525 result = -EINVAL; 526 else if (entry->func == MODULE_CHECK) 527 ima_appraise |= IMA_APPRAISE_MODULES; 528 audit_log_format(ab, "res=%d", !result); 529 audit_log_end(ab); 530 return result; 531 } 532 533 /** 534 * ima_parse_add_rule - add a rule to ima_policy_rules 535 * @rule - ima measurement policy rule 536 * 537 * Uses a mutex to protect the policy list from multiple concurrent writers. 538 * Returns the length of the rule parsed, an error code on failure 539 */ 540 ssize_t ima_parse_add_rule(char *rule) 541 { 542 const char *op = "update_policy"; 543 char *p; 544 struct ima_rule_entry *entry; 545 ssize_t result, len; 546 int audit_info = 0; 547 548 /* Prevent installed policy from changing */ 549 if (ima_rules != &ima_default_rules) { 550 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 551 NULL, op, "already exists", 552 -EACCES, audit_info); 553 return -EACCES; 554 } 555 556 entry = kzalloc(sizeof(*entry), GFP_KERNEL); 557 if (!entry) { 558 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 559 NULL, op, "-ENOMEM", -ENOMEM, audit_info); 560 return -ENOMEM; 561 } 562 563 INIT_LIST_HEAD(&entry->list); 564 565 p = strsep(&rule, "\n"); 566 len = strlen(p) + 1; 567 568 if (*p == '#') { 569 kfree(entry); 570 return len; 571 } 572 573 result = ima_parse_rule(p, entry); 574 if (result) { 575 kfree(entry); 576 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 577 NULL, op, "invalid policy", result, 578 audit_info); 579 return result; 580 } 581 582 mutex_lock(&ima_rules_mutex); 583 list_add_tail(&entry->list, &ima_policy_rules); 584 mutex_unlock(&ima_rules_mutex); 585 586 return len; 587 } 588 589 /* ima_delete_rules called to cleanup invalid policy */ 590 void ima_delete_rules(void) 591 { 592 struct ima_rule_entry *entry, *tmp; 593 594 mutex_lock(&ima_rules_mutex); 595 list_for_each_entry_safe(entry, tmp, &ima_policy_rules, list) { 596 list_del(&entry->list); 597 kfree(entry); 598 } 599 mutex_unlock(&ima_rules_mutex); 600 } 601