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 28enum ima_action { UNKNOWN = -1, DONT_MEASURE = 0, MEASURE }; 29 30#define MAX_LSM_RULES 6 31enum lsm_rule_types { LSM_OBJ_USER, LSM_OBJ_ROLE, LSM_OBJ_TYPE, 32 LSM_SUBJ_USER, LSM_SUBJ_ROLE, LSM_SUBJ_TYPE 33}; 34 35struct ima_measure_rule_entry { 36 struct list_head list; 37 enum ima_action action; 38 unsigned int flags; 39 enum ima_hooks func; 40 int mask; 41 unsigned long fsmagic; 42 uid_t uid; 43 struct { 44 void *rule; /* LSM file metadata specific */ 45 int type; /* audit type */ 46 } lsm[MAX_LSM_RULES]; 47}; 48 49/* 50 * Without LSM specific knowledge, the default policy can only be 51 * written in terms of .action, .func, .mask, .fsmagic, and .uid 52 */ 53 54/* 55 * The minimum rule set to allow for full TCB coverage. Measures all files 56 * opened or mmap for exec and everything read by root. Dangerous because 57 * normal users can easily run the machine out of memory simply building 58 * and running executables. 59 */ 60static struct ima_measure_rule_entry default_rules[] = { 61 {.action = DONT_MEASURE,.fsmagic = PROC_SUPER_MAGIC,.flags = IMA_FSMAGIC}, 62 {.action = DONT_MEASURE,.fsmagic = SYSFS_MAGIC,.flags = IMA_FSMAGIC}, 63 {.action = DONT_MEASURE,.fsmagic = DEBUGFS_MAGIC,.flags = IMA_FSMAGIC}, 64 {.action = DONT_MEASURE,.fsmagic = TMPFS_MAGIC,.flags = IMA_FSMAGIC}, 65 {.action = DONT_MEASURE,.fsmagic = SECURITYFS_MAGIC,.flags = IMA_FSMAGIC}, 66 {.action = DONT_MEASURE,.fsmagic = SELINUX_MAGIC,.flags = IMA_FSMAGIC}, 67 {.action = MEASURE,.func = FILE_MMAP,.mask = MAY_EXEC, 68 .flags = IMA_FUNC | IMA_MASK}, 69 {.action = MEASURE,.func = BPRM_CHECK,.mask = MAY_EXEC, 70 .flags = IMA_FUNC | IMA_MASK}, 71 {.action = MEASURE,.func = FILE_CHECK,.mask = MAY_READ,.uid = 0, 72 .flags = IMA_FUNC | IMA_MASK | IMA_UID}, 73}; 74 75static LIST_HEAD(measure_default_rules); 76static LIST_HEAD(measure_policy_rules); 77static struct list_head *ima_measure; 78 79static DEFINE_MUTEX(ima_measure_mutex); 80 81static bool ima_use_tcb __initdata; 82static int __init default_policy_setup(char *str) 83{ 84 ima_use_tcb = 1; 85 return 1; 86} 87__setup("ima_tcb", default_policy_setup); 88 89/** 90 * ima_match_rules - determine whether an inode matches the measure rule. 91 * @rule: a pointer to a rule 92 * @inode: a pointer to an inode 93 * @func: LIM hook identifier 94 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) 95 * 96 * Returns true on rule match, false on failure. 97 */ 98static bool ima_match_rules(struct ima_measure_rule_entry *rule, 99 struct inode *inode, enum ima_hooks func, int mask) 100{ 101 struct task_struct *tsk = current; 102 int i; 103 104 if ((rule->flags & IMA_FUNC) && rule->func != func) 105 return false; 106 if ((rule->flags & IMA_MASK) && rule->mask != mask) 107 return false; 108 if ((rule->flags & IMA_FSMAGIC) 109 && rule->fsmagic != inode->i_sb->s_magic) 110 return false; 111 if ((rule->flags & IMA_UID) && rule->uid != tsk->cred->uid) 112 return false; 113 for (i = 0; i < MAX_LSM_RULES; i++) { 114 int rc = 0; 115 u32 osid, sid; 116 117 if (!rule->lsm[i].rule) 118 continue; 119 120 switch (i) { 121 case LSM_OBJ_USER: 122 case LSM_OBJ_ROLE: 123 case LSM_OBJ_TYPE: 124 security_inode_getsecid(inode, &osid); 125 rc = security_filter_rule_match(osid, 126 rule->lsm[i].type, 127 Audit_equal, 128 rule->lsm[i].rule, 129 NULL); 130 break; 131 case LSM_SUBJ_USER: 132 case LSM_SUBJ_ROLE: 133 case LSM_SUBJ_TYPE: 134 security_task_getsecid(tsk, &sid); 135 rc = security_filter_rule_match(sid, 136 rule->lsm[i].type, 137 Audit_equal, 138 rule->lsm[i].rule, 139 NULL); 140 default: 141 break; 142 } 143 if (!rc) 144 return false; 145 } 146 return true; 147} 148 149/** 150 * ima_match_policy - decision based on LSM and other conditions 151 * @inode: pointer to an inode for which the policy decision is being made 152 * @func: IMA hook identifier 153 * @mask: requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) 154 * 155 * Measure decision based on func/mask/fsmagic and LSM(subj/obj/type) 156 * conditions. 157 * 158 * (There is no need for locking when walking the policy list, 159 * as elements in the list are never deleted, nor does the list 160 * change.) 161 */ 162int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask) 163{ 164 struct ima_measure_rule_entry *entry; 165 166 list_for_each_entry(entry, ima_measure, list) { 167 bool rc; 168 169 rc = ima_match_rules(entry, inode, func, mask); 170 if (rc) 171 return entry->action; 172 } 173 return 0; 174} 175 176/** 177 * ima_init_policy - initialize the default measure rules. 178 * 179 * ima_measure points to either the measure_default_rules or the 180 * the new measure_policy_rules. 181 */ 182void __init ima_init_policy(void) 183{ 184 int i, entries; 185 186 /* if !ima_use_tcb set entries = 0 so we load NO default rules */ 187 if (ima_use_tcb) 188 entries = ARRAY_SIZE(default_rules); 189 else 190 entries = 0; 191 192 for (i = 0; i < entries; i++) 193 list_add_tail(&default_rules[i].list, &measure_default_rules); 194 ima_measure = &measure_default_rules; 195} 196 197/** 198 * ima_update_policy - update default_rules with new measure rules 199 * 200 * Called on file .release to update the default rules with a complete new 201 * policy. Once updated, the policy is locked, no additional rules can be 202 * added to the policy. 203 */ 204void ima_update_policy(void) 205{ 206 const char *op = "policy_update"; 207 const char *cause = "already exists"; 208 int result = 1; 209 int audit_info = 0; 210 211 if (ima_measure == &measure_default_rules) { 212 ima_measure = &measure_policy_rules; 213 cause = "complete"; 214 result = 0; 215 } 216 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 217 NULL, op, cause, result, audit_info); 218} 219 220enum { 221 Opt_err = -1, 222 Opt_measure = 1, Opt_dont_measure, 223 Opt_obj_user, Opt_obj_role, Opt_obj_type, 224 Opt_subj_user, Opt_subj_role, Opt_subj_type, 225 Opt_func, Opt_mask, Opt_fsmagic, Opt_uid 226}; 227 228static match_table_t policy_tokens = { 229 {Opt_measure, "measure"}, 230 {Opt_dont_measure, "dont_measure"}, 231 {Opt_obj_user, "obj_user=%s"}, 232 {Opt_obj_role, "obj_role=%s"}, 233 {Opt_obj_type, "obj_type=%s"}, 234 {Opt_subj_user, "subj_user=%s"}, 235 {Opt_subj_role, "subj_role=%s"}, 236 {Opt_subj_type, "subj_type=%s"}, 237 {Opt_func, "func=%s"}, 238 {Opt_mask, "mask=%s"}, 239 {Opt_fsmagic, "fsmagic=%s"}, 240 {Opt_uid, "uid=%s"}, 241 {Opt_err, NULL} 242}; 243 244static int ima_lsm_rule_init(struct ima_measure_rule_entry *entry, 245 char *args, int lsm_rule, int audit_type) 246{ 247 int result; 248 249 if (entry->lsm[lsm_rule].rule) 250 return -EINVAL; 251 252 entry->lsm[lsm_rule].type = audit_type; 253 result = security_filter_rule_init(entry->lsm[lsm_rule].type, 254 Audit_equal, args, 255 &entry->lsm[lsm_rule].rule); 256 if (!entry->lsm[lsm_rule].rule) 257 return -EINVAL; 258 return result; 259} 260 261static void ima_log_string(struct audit_buffer *ab, char *key, char *value) 262{ 263 audit_log_format(ab, "%s=", key); 264 audit_log_untrustedstring(ab, value); 265 audit_log_format(ab, " "); 266} 267 268static int ima_parse_rule(char *rule, struct ima_measure_rule_entry *entry) 269{ 270 struct audit_buffer *ab; 271 char *p; 272 int result = 0; 273 274 ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_RULE); 275 276 entry->uid = -1; 277 entry->action = UNKNOWN; 278 while ((p = strsep(&rule, " \t")) != NULL) { 279 substring_t args[MAX_OPT_ARGS]; 280 int token; 281 unsigned long lnum; 282 283 if (result < 0) 284 break; 285 if ((*p == '\0') || (*p == ' ') || (*p == '\t')) 286 continue; 287 token = match_token(p, policy_tokens, args); 288 switch (token) { 289 case Opt_measure: 290 ima_log_string(ab, "action", "measure"); 291 292 if (entry->action != UNKNOWN) 293 result = -EINVAL; 294 295 entry->action = MEASURE; 296 break; 297 case Opt_dont_measure: 298 ima_log_string(ab, "action", "dont_measure"); 299 300 if (entry->action != UNKNOWN) 301 result = -EINVAL; 302 303 entry->action = DONT_MEASURE; 304 break; 305 case Opt_func: 306 ima_log_string(ab, "func", args[0].from); 307 308 if (entry->func) 309 result = -EINVAL; 310 311 if (strcmp(args[0].from, "FILE_CHECK") == 0) 312 entry->func = FILE_CHECK; 313 /* PATH_CHECK is for backwards compat */ 314 else if (strcmp(args[0].from, "PATH_CHECK") == 0) 315 entry->func = FILE_CHECK; 316 else if (strcmp(args[0].from, "FILE_MMAP") == 0) 317 entry->func = FILE_MMAP; 318 else if (strcmp(args[0].from, "BPRM_CHECK") == 0) 319 entry->func = BPRM_CHECK; 320 else 321 result = -EINVAL; 322 if (!result) 323 entry->flags |= IMA_FUNC; 324 break; 325 case Opt_mask: 326 ima_log_string(ab, "mask", args[0].from); 327 328 if (entry->mask) 329 result = -EINVAL; 330 331 if ((strcmp(args[0].from, "MAY_EXEC")) == 0) 332 entry->mask = MAY_EXEC; 333 else if (strcmp(args[0].from, "MAY_WRITE") == 0) 334 entry->mask = MAY_WRITE; 335 else if (strcmp(args[0].from, "MAY_READ") == 0) 336 entry->mask = MAY_READ; 337 else if (strcmp(args[0].from, "MAY_APPEND") == 0) 338 entry->mask = MAY_APPEND; 339 else 340 result = -EINVAL; 341 if (!result) 342 entry->flags |= IMA_MASK; 343 break; 344 case Opt_fsmagic: 345 ima_log_string(ab, "fsmagic", args[0].from); 346 347 if (entry->fsmagic) { 348 result = -EINVAL; 349 break; 350 } 351 352 result = strict_strtoul(args[0].from, 16, 353 &entry->fsmagic); 354 if (!result) 355 entry->flags |= IMA_FSMAGIC; 356 break; 357 case Opt_uid: 358 ima_log_string(ab, "uid", args[0].from); 359 360 if (entry->uid != -1) { 361 result = -EINVAL; 362 break; 363 } 364 365 result = strict_strtoul(args[0].from, 10, &lnum); 366 if (!result) { 367 entry->uid = (uid_t) lnum; 368 if (entry->uid != lnum) 369 result = -EINVAL; 370 else 371 entry->flags |= IMA_UID; 372 } 373 break; 374 case Opt_obj_user: 375 ima_log_string(ab, "obj_user", args[0].from); 376 result = ima_lsm_rule_init(entry, args[0].from, 377 LSM_OBJ_USER, 378 AUDIT_OBJ_USER); 379 break; 380 case Opt_obj_role: 381 ima_log_string(ab, "obj_role", args[0].from); 382 result = ima_lsm_rule_init(entry, args[0].from, 383 LSM_OBJ_ROLE, 384 AUDIT_OBJ_ROLE); 385 break; 386 case Opt_obj_type: 387 ima_log_string(ab, "obj_type", args[0].from); 388 result = ima_lsm_rule_init(entry, args[0].from, 389 LSM_OBJ_TYPE, 390 AUDIT_OBJ_TYPE); 391 break; 392 case Opt_subj_user: 393 ima_log_string(ab, "subj_user", args[0].from); 394 result = ima_lsm_rule_init(entry, args[0].from, 395 LSM_SUBJ_USER, 396 AUDIT_SUBJ_USER); 397 break; 398 case Opt_subj_role: 399 ima_log_string(ab, "subj_role", args[0].from); 400 result = ima_lsm_rule_init(entry, args[0].from, 401 LSM_SUBJ_ROLE, 402 AUDIT_SUBJ_ROLE); 403 break; 404 case Opt_subj_type: 405 ima_log_string(ab, "subj_type", args[0].from); 406 result = ima_lsm_rule_init(entry, args[0].from, 407 LSM_SUBJ_TYPE, 408 AUDIT_SUBJ_TYPE); 409 break; 410 case Opt_err: 411 ima_log_string(ab, "UNKNOWN", p); 412 result = -EINVAL; 413 break; 414 } 415 } 416 if (!result && (entry->action == UNKNOWN)) 417 result = -EINVAL; 418 419 audit_log_format(ab, "res=%d", !!result); 420 audit_log_end(ab); 421 return result; 422} 423 424/** 425 * ima_parse_add_rule - add a rule to measure_policy_rules 426 * @rule - ima measurement policy rule 427 * 428 * Uses a mutex to protect the policy list from multiple concurrent writers. 429 * Returns the length of the rule parsed, an error code on failure 430 */ 431ssize_t ima_parse_add_rule(char *rule) 432{ 433 const char *op = "update_policy"; 434 char *p; 435 struct ima_measure_rule_entry *entry; 436 ssize_t result, len; 437 int audit_info = 0; 438 439 /* Prevent installed policy from changing */ 440 if (ima_measure != &measure_default_rules) { 441 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 442 NULL, op, "already exists", 443 -EACCES, audit_info); 444 return -EACCES; 445 } 446 447 entry = kzalloc(sizeof(*entry), GFP_KERNEL); 448 if (!entry) { 449 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 450 NULL, op, "-ENOMEM", -ENOMEM, audit_info); 451 return -ENOMEM; 452 } 453 454 INIT_LIST_HEAD(&entry->list); 455 456 p = strsep(&rule, "\n"); 457 len = strlen(p) + 1; 458 459 if (*p == '#') { 460 kfree(entry); 461 return len; 462 } 463 464 result = ima_parse_rule(p, entry); 465 if (result) { 466 kfree(entry); 467 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, 468 NULL, op, "invalid policy", result, 469 audit_info); 470 return result; 471 } 472 473 mutex_lock(&ima_measure_mutex); 474 list_add_tail(&entry->list, &measure_policy_rules); 475 mutex_unlock(&ima_measure_mutex); 476 477 return len; 478} 479 480/* ima_delete_rules called to cleanup invalid policy */ 481void ima_delete_rules(void) 482{ 483 struct ima_measure_rule_entry *entry, *tmp; 484 485 mutex_lock(&ima_measure_mutex); 486 list_for_each_entry_safe(entry, tmp, &measure_policy_rules, list) { 487 list_del(&entry->list); 488 kfree(entry); 489 } 490 mutex_unlock(&ima_measure_mutex); 491} 492