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