1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2011 IBM Corporation 4 * 5 * Author: 6 * Mimi Zohar <zohar@us.ibm.com> 7 */ 8 #include <linux/init.h> 9 #include <linux/file.h> 10 #include <linux/fs.h> 11 #include <linux/xattr.h> 12 #include <linux/magic.h> 13 #include <linux/ima.h> 14 #include <linux/evm.h> 15 #include <keys/system_keyring.h> 16 17 #include "ima.h" 18 19 static int __init default_appraise_setup(char *str) 20 { 21 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM 22 bool sb_state = arch_ima_get_secureboot(); 23 int appraisal_state = ima_appraise; 24 25 if (strncmp(str, "off", 3) == 0) 26 appraisal_state = 0; 27 else if (strncmp(str, "log", 3) == 0) 28 appraisal_state = IMA_APPRAISE_LOG; 29 else if (strncmp(str, "fix", 3) == 0) 30 appraisal_state = IMA_APPRAISE_FIX; 31 else if (strncmp(str, "enforce", 7) == 0) 32 appraisal_state = IMA_APPRAISE_ENFORCE; 33 else 34 pr_err("invalid \"%s\" appraise option", str); 35 36 /* If appraisal state was changed, but secure boot is enabled, 37 * keep its default */ 38 if (sb_state) { 39 if (!(appraisal_state & IMA_APPRAISE_ENFORCE)) 40 pr_info("Secure boot enabled: ignoring ima_appraise=%s option", 41 str); 42 } else { 43 ima_appraise = appraisal_state; 44 } 45 #endif 46 return 1; 47 } 48 49 __setup("ima_appraise=", default_appraise_setup); 50 51 /* 52 * is_ima_appraise_enabled - return appraise status 53 * 54 * Only return enabled, if not in ima_appraise="fix" or "log" modes. 55 */ 56 bool is_ima_appraise_enabled(void) 57 { 58 return ima_appraise & IMA_APPRAISE_ENFORCE; 59 } 60 61 /* 62 * ima_must_appraise - set appraise flag 63 * 64 * Return 1 to appraise or hash 65 */ 66 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) 67 { 68 u32 secid; 69 70 if (!ima_appraise) 71 return 0; 72 73 security_task_getsecid(current, &secid); 74 return ima_match_policy(inode, current_cred(), secid, func, mask, 75 IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL); 76 } 77 78 static int ima_fix_xattr(struct dentry *dentry, 79 struct integrity_iint_cache *iint) 80 { 81 int rc, offset; 82 u8 algo = iint->ima_hash->algo; 83 84 if (algo <= HASH_ALGO_SHA1) { 85 offset = 1; 86 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST; 87 } else { 88 offset = 0; 89 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; 90 iint->ima_hash->xattr.ng.algo = algo; 91 } 92 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, 93 &iint->ima_hash->xattr.data[offset], 94 (sizeof(iint->ima_hash->xattr) - offset) + 95 iint->ima_hash->length, 0); 96 return rc; 97 } 98 99 /* Return specific func appraised cached result */ 100 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, 101 enum ima_hooks func) 102 { 103 switch (func) { 104 case MMAP_CHECK: 105 return iint->ima_mmap_status; 106 case BPRM_CHECK: 107 return iint->ima_bprm_status; 108 case CREDS_CHECK: 109 return iint->ima_creds_status; 110 case FILE_CHECK: 111 case POST_SETATTR: 112 return iint->ima_file_status; 113 case MODULE_CHECK ... MAX_CHECK - 1: 114 default: 115 return iint->ima_read_status; 116 } 117 } 118 119 static void ima_set_cache_status(struct integrity_iint_cache *iint, 120 enum ima_hooks func, 121 enum integrity_status status) 122 { 123 switch (func) { 124 case MMAP_CHECK: 125 iint->ima_mmap_status = status; 126 break; 127 case BPRM_CHECK: 128 iint->ima_bprm_status = status; 129 break; 130 case CREDS_CHECK: 131 iint->ima_creds_status = status; 132 break; 133 case FILE_CHECK: 134 case POST_SETATTR: 135 iint->ima_file_status = status; 136 break; 137 case MODULE_CHECK ... MAX_CHECK - 1: 138 default: 139 iint->ima_read_status = status; 140 break; 141 } 142 } 143 144 static void ima_cache_flags(struct integrity_iint_cache *iint, 145 enum ima_hooks func) 146 { 147 switch (func) { 148 case MMAP_CHECK: 149 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); 150 break; 151 case BPRM_CHECK: 152 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); 153 break; 154 case CREDS_CHECK: 155 iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED); 156 break; 157 case FILE_CHECK: 158 case POST_SETATTR: 159 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); 160 break; 161 case MODULE_CHECK ... MAX_CHECK - 1: 162 default: 163 iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED); 164 break; 165 } 166 } 167 168 enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, 169 int xattr_len) 170 { 171 struct signature_v2_hdr *sig; 172 enum hash_algo ret; 173 174 if (!xattr_value || xattr_len < 2) 175 /* return default hash algo */ 176 return ima_hash_algo; 177 178 switch (xattr_value->type) { 179 case EVM_IMA_XATTR_DIGSIG: 180 sig = (typeof(sig))xattr_value; 181 if (sig->version != 2 || xattr_len <= sizeof(*sig)) 182 return ima_hash_algo; 183 return sig->hash_algo; 184 break; 185 case IMA_XATTR_DIGEST_NG: 186 /* first byte contains algorithm id */ 187 ret = xattr_value->data[0]; 188 if (ret < HASH_ALGO__LAST) 189 return ret; 190 break; 191 case IMA_XATTR_DIGEST: 192 /* this is for backward compatibility */ 193 if (xattr_len == 21) { 194 unsigned int zero = 0; 195 if (!memcmp(&xattr_value->data[16], &zero, 4)) 196 return HASH_ALGO_MD5; 197 else 198 return HASH_ALGO_SHA1; 199 } else if (xattr_len == 17) 200 return HASH_ALGO_MD5; 201 break; 202 } 203 204 /* return default hash algo */ 205 return ima_hash_algo; 206 } 207 208 int ima_read_xattr(struct dentry *dentry, 209 struct evm_ima_xattr_data **xattr_value) 210 { 211 ssize_t ret; 212 213 ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, 214 0, GFP_NOFS); 215 if (ret == -EOPNOTSUPP) 216 ret = 0; 217 return ret; 218 } 219 220 /* 221 * xattr_verify - verify xattr digest or signature 222 * 223 * Verify whether the hash or signature matches the file contents. 224 * 225 * Return 0 on success, error code otherwise. 226 */ 227 static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint, 228 struct evm_ima_xattr_data *xattr_value, int xattr_len, 229 enum integrity_status *status, const char **cause) 230 { 231 int rc = -EINVAL, hash_start = 0; 232 233 switch (xattr_value->type) { 234 case IMA_XATTR_DIGEST_NG: 235 /* first byte contains algorithm id */ 236 hash_start = 1; 237 fallthrough; 238 case IMA_XATTR_DIGEST: 239 if (iint->flags & IMA_DIGSIG_REQUIRED) { 240 *cause = "IMA-signature-required"; 241 *status = INTEGRITY_FAIL; 242 break; 243 } 244 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 245 if (xattr_len - sizeof(xattr_value->type) - hash_start >= 246 iint->ima_hash->length) 247 /* 248 * xattr length may be longer. md5 hash in previous 249 * version occupied 20 bytes in xattr, instead of 16 250 */ 251 rc = memcmp(&xattr_value->data[hash_start], 252 iint->ima_hash->digest, 253 iint->ima_hash->length); 254 else 255 rc = -EINVAL; 256 if (rc) { 257 *cause = "invalid-hash"; 258 *status = INTEGRITY_FAIL; 259 break; 260 } 261 *status = INTEGRITY_PASS; 262 break; 263 case EVM_IMA_XATTR_DIGSIG: 264 set_bit(IMA_DIGSIG, &iint->atomic_flags); 265 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 266 (const char *)xattr_value, 267 xattr_len, 268 iint->ima_hash->digest, 269 iint->ima_hash->length); 270 if (rc == -EOPNOTSUPP) { 271 *status = INTEGRITY_UNKNOWN; 272 break; 273 } 274 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && 275 func == KEXEC_KERNEL_CHECK) 276 rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM, 277 (const char *)xattr_value, 278 xattr_len, 279 iint->ima_hash->digest, 280 iint->ima_hash->length); 281 if (rc) { 282 *cause = "invalid-signature"; 283 *status = INTEGRITY_FAIL; 284 } else { 285 *status = INTEGRITY_PASS; 286 } 287 break; 288 default: 289 *status = INTEGRITY_UNKNOWN; 290 *cause = "unknown-ima-data"; 291 break; 292 } 293 294 return rc; 295 } 296 297 /* 298 * modsig_verify - verify modsig signature 299 * 300 * Verify whether the signature matches the file contents. 301 * 302 * Return 0 on success, error code otherwise. 303 */ 304 static int modsig_verify(enum ima_hooks func, const struct modsig *modsig, 305 enum integrity_status *status, const char **cause) 306 { 307 int rc; 308 309 rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig); 310 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && 311 func == KEXEC_KERNEL_CHECK) 312 rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM, 313 modsig); 314 if (rc) { 315 *cause = "invalid-signature"; 316 *status = INTEGRITY_FAIL; 317 } else { 318 *status = INTEGRITY_PASS; 319 } 320 321 return rc; 322 } 323 324 /* 325 * ima_check_blacklist - determine if the binary is blacklisted. 326 * 327 * Add the hash of the blacklisted binary to the measurement list, based 328 * on policy. 329 * 330 * Returns -EPERM if the hash is blacklisted. 331 */ 332 int ima_check_blacklist(struct integrity_iint_cache *iint, 333 const struct modsig *modsig, int pcr) 334 { 335 enum hash_algo hash_algo; 336 const u8 *digest = NULL; 337 u32 digestsize = 0; 338 int rc = 0; 339 340 if (!(iint->flags & IMA_CHECK_BLACKLIST)) 341 return 0; 342 343 if (iint->flags & IMA_MODSIG_ALLOWED && modsig) { 344 ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize); 345 346 rc = is_binary_blacklisted(digest, digestsize); 347 if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) 348 process_buffer_measurement(NULL, digest, digestsize, 349 "blacklisted-hash", NONE, 350 pcr, NULL); 351 } 352 353 return rc; 354 } 355 356 /* 357 * ima_appraise_measurement - appraise file measurement 358 * 359 * Call evm_verifyxattr() to verify the integrity of 'security.ima'. 360 * Assuming success, compare the xattr hash with the collected measurement. 361 * 362 * Return 0 on success, error code otherwise 363 */ 364 int ima_appraise_measurement(enum ima_hooks func, 365 struct integrity_iint_cache *iint, 366 struct file *file, const unsigned char *filename, 367 struct evm_ima_xattr_data *xattr_value, 368 int xattr_len, const struct modsig *modsig) 369 { 370 static const char op[] = "appraise_data"; 371 const char *cause = "unknown"; 372 struct dentry *dentry = file_dentry(file); 373 struct inode *inode = d_backing_inode(dentry); 374 enum integrity_status status = INTEGRITY_UNKNOWN; 375 int rc = xattr_len; 376 bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig; 377 378 /* If not appraising a modsig, we need an xattr. */ 379 if (!(inode->i_opflags & IOP_XATTR) && !try_modsig) 380 return INTEGRITY_UNKNOWN; 381 382 /* If reading the xattr failed and there's no modsig, error out. */ 383 if (rc <= 0 && !try_modsig) { 384 if (rc && rc != -ENODATA) 385 goto out; 386 387 cause = iint->flags & IMA_DIGSIG_REQUIRED ? 388 "IMA-signature-required" : "missing-hash"; 389 status = INTEGRITY_NOLABEL; 390 if (file->f_mode & FMODE_CREATED) 391 iint->flags |= IMA_NEW_FILE; 392 if ((iint->flags & IMA_NEW_FILE) && 393 (!(iint->flags & IMA_DIGSIG_REQUIRED) || 394 (inode->i_size == 0))) 395 status = INTEGRITY_PASS; 396 goto out; 397 } 398 399 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); 400 switch (status) { 401 case INTEGRITY_PASS: 402 case INTEGRITY_PASS_IMMUTABLE: 403 case INTEGRITY_UNKNOWN: 404 break; 405 case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ 406 /* It's fine not to have xattrs when using a modsig. */ 407 if (try_modsig) 408 break; 409 fallthrough; 410 case INTEGRITY_NOLABEL: /* No security.evm xattr. */ 411 cause = "missing-HMAC"; 412 goto out; 413 case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ 414 cause = "invalid-HMAC"; 415 goto out; 416 default: 417 WARN_ONCE(true, "Unexpected integrity status %d\n", status); 418 } 419 420 if (xattr_value) 421 rc = xattr_verify(func, iint, xattr_value, xattr_len, &status, 422 &cause); 423 424 /* 425 * If we have a modsig and either no imasig or the imasig's key isn't 426 * known, then try verifying the modsig. 427 */ 428 if (try_modsig && 429 (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG || 430 rc == -ENOKEY)) 431 rc = modsig_verify(func, modsig, &status, &cause); 432 433 out: 434 /* 435 * File signatures on some filesystems can not be properly verified. 436 * When such filesystems are mounted by an untrusted mounter or on a 437 * system not willing to accept such a risk, fail the file signature 438 * verification. 439 */ 440 if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && 441 ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) || 442 (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) { 443 status = INTEGRITY_FAIL; 444 cause = "unverifiable-signature"; 445 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 446 op, cause, rc, 0); 447 } else if (status != INTEGRITY_PASS) { 448 /* Fix mode, but don't replace file signatures. */ 449 if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig && 450 (!xattr_value || 451 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { 452 if (!ima_fix_xattr(dentry, iint)) 453 status = INTEGRITY_PASS; 454 } 455 456 /* Permit new files with file signatures, but without data. */ 457 if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && 458 xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { 459 status = INTEGRITY_PASS; 460 } 461 462 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 463 op, cause, rc, 0); 464 } else { 465 ima_cache_flags(iint, func); 466 } 467 468 ima_set_cache_status(iint, func, status); 469 return status; 470 } 471 472 /* 473 * ima_update_xattr - update 'security.ima' hash value 474 */ 475 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) 476 { 477 struct dentry *dentry = file_dentry(file); 478 int rc = 0; 479 480 /* do not collect and update hash for digital signatures */ 481 if (test_bit(IMA_DIGSIG, &iint->atomic_flags)) 482 return; 483 484 if ((iint->ima_file_status != INTEGRITY_PASS) && 485 !(iint->flags & IMA_HASH)) 486 return; 487 488 rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL); 489 if (rc < 0) 490 return; 491 492 inode_lock(file_inode(file)); 493 ima_fix_xattr(dentry, iint); 494 inode_unlock(file_inode(file)); 495 } 496 497 /** 498 * ima_inode_post_setattr - reflect file metadata changes 499 * @dentry: pointer to the affected dentry 500 * 501 * Changes to a dentry's metadata might result in needing to appraise. 502 * 503 * This function is called from notify_change(), which expects the caller 504 * to lock the inode's i_mutex. 505 */ 506 void ima_inode_post_setattr(struct dentry *dentry) 507 { 508 struct inode *inode = d_backing_inode(dentry); 509 struct integrity_iint_cache *iint; 510 int action; 511 512 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode) 513 || !(inode->i_opflags & IOP_XATTR)) 514 return; 515 516 action = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); 517 if (!action) 518 __vfs_removexattr(dentry, XATTR_NAME_IMA); 519 iint = integrity_iint_find(inode); 520 if (iint) { 521 set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags); 522 if (!action) 523 clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); 524 } 525 } 526 527 /* 528 * ima_protect_xattr - protect 'security.ima' 529 * 530 * Ensure that not just anyone can modify or remove 'security.ima'. 531 */ 532 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, 533 const void *xattr_value, size_t xattr_value_len) 534 { 535 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { 536 if (!capable(CAP_SYS_ADMIN)) 537 return -EPERM; 538 return 1; 539 } 540 return 0; 541 } 542 543 static void ima_reset_appraise_flags(struct inode *inode, int digsig) 544 { 545 struct integrity_iint_cache *iint; 546 547 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) 548 return; 549 550 iint = integrity_iint_find(inode); 551 if (!iint) 552 return; 553 iint->measured_pcrs = 0; 554 set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); 555 if (digsig) 556 set_bit(IMA_DIGSIG, &iint->atomic_flags); 557 else 558 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 559 } 560 561 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, 562 const void *xattr_value, size_t xattr_value_len) 563 { 564 const struct evm_ima_xattr_data *xvalue = xattr_value; 565 int result; 566 567 result = ima_protect_xattr(dentry, xattr_name, xattr_value, 568 xattr_value_len); 569 if (result == 1) { 570 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) 571 return -EINVAL; 572 ima_reset_appraise_flags(d_backing_inode(dentry), 573 xvalue->type == EVM_IMA_XATTR_DIGSIG); 574 result = 0; 575 } 576 return result; 577 } 578 579 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) 580 { 581 int result; 582 583 result = ima_protect_xattr(dentry, xattr_name, NULL, 0); 584 if (result == 1) { 585 ima_reset_appraise_flags(d_backing_inode(dentry), 0); 586 result = 0; 587 } 588 return result; 589 } 590