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/module.h> 9 #include <linux/init.h> 10 #include <linux/file.h> 11 #include <linux/fs.h> 12 #include <linux/xattr.h> 13 #include <linux/magic.h> 14 #include <linux/ima.h> 15 #include <linux/evm.h> 16 #include <keys/system_keyring.h> 17 18 #include "ima.h" 19 20 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM 21 static char *ima_appraise_cmdline_default __initdata; 22 core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0); 23 24 void __init ima_appraise_parse_cmdline(void) 25 { 26 const char *str = ima_appraise_cmdline_default; 27 bool sb_state = arch_ima_get_secureboot(); 28 int appraisal_state = ima_appraise; 29 30 if (!str) 31 return; 32 33 if (strncmp(str, "off", 3) == 0) 34 appraisal_state = 0; 35 else if (strncmp(str, "log", 3) == 0) 36 appraisal_state = IMA_APPRAISE_LOG; 37 else if (strncmp(str, "fix", 3) == 0) 38 appraisal_state = IMA_APPRAISE_FIX; 39 else if (strncmp(str, "enforce", 7) == 0) 40 appraisal_state = IMA_APPRAISE_ENFORCE; 41 else 42 pr_err("invalid \"%s\" appraise option", str); 43 44 /* If appraisal state was changed, but secure boot is enabled, 45 * keep its default */ 46 if (sb_state) { 47 if (!(appraisal_state & IMA_APPRAISE_ENFORCE)) 48 pr_info("Secure boot enabled: ignoring ima_appraise=%s option", 49 str); 50 } else { 51 ima_appraise = appraisal_state; 52 } 53 } 54 #endif 55 56 /* 57 * is_ima_appraise_enabled - return appraise status 58 * 59 * Only return enabled, if not in ima_appraise="fix" or "log" modes. 60 */ 61 bool is_ima_appraise_enabled(void) 62 { 63 return ima_appraise & IMA_APPRAISE_ENFORCE; 64 } 65 66 /* 67 * ima_must_appraise - set appraise flag 68 * 69 * Return 1 to appraise or hash 70 */ 71 int ima_must_appraise(struct user_namespace *mnt_userns, struct inode *inode, 72 int mask, enum ima_hooks func) 73 { 74 u32 secid; 75 76 if (!ima_appraise) 77 return 0; 78 79 security_task_getsecid(current, &secid); 80 return ima_match_policy(mnt_userns, inode, current_cred(), secid, func, 81 mask, IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL); 82 } 83 84 static int ima_fix_xattr(struct dentry *dentry, 85 struct integrity_iint_cache *iint) 86 { 87 int rc, offset; 88 u8 algo = iint->ima_hash->algo; 89 90 if (algo <= HASH_ALGO_SHA1) { 91 offset = 1; 92 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST; 93 } else { 94 offset = 0; 95 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; 96 iint->ima_hash->xattr.ng.algo = algo; 97 } 98 rc = __vfs_setxattr_noperm(&init_user_ns, dentry, XATTR_NAME_IMA, 99 &iint->ima_hash->xattr.data[offset], 100 (sizeof(iint->ima_hash->xattr) - offset) + 101 iint->ima_hash->length, 0); 102 return rc; 103 } 104 105 /* Return specific func appraised cached result */ 106 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, 107 enum ima_hooks func) 108 { 109 switch (func) { 110 case MMAP_CHECK: 111 return iint->ima_mmap_status; 112 case BPRM_CHECK: 113 return iint->ima_bprm_status; 114 case CREDS_CHECK: 115 return iint->ima_creds_status; 116 case FILE_CHECK: 117 case POST_SETATTR: 118 return iint->ima_file_status; 119 case MODULE_CHECK ... MAX_CHECK - 1: 120 default: 121 return iint->ima_read_status; 122 } 123 } 124 125 static void ima_set_cache_status(struct integrity_iint_cache *iint, 126 enum ima_hooks func, 127 enum integrity_status status) 128 { 129 switch (func) { 130 case MMAP_CHECK: 131 iint->ima_mmap_status = status; 132 break; 133 case BPRM_CHECK: 134 iint->ima_bprm_status = status; 135 break; 136 case CREDS_CHECK: 137 iint->ima_creds_status = status; 138 break; 139 case FILE_CHECK: 140 case POST_SETATTR: 141 iint->ima_file_status = status; 142 break; 143 case MODULE_CHECK ... MAX_CHECK - 1: 144 default: 145 iint->ima_read_status = status; 146 break; 147 } 148 } 149 150 static void ima_cache_flags(struct integrity_iint_cache *iint, 151 enum ima_hooks func) 152 { 153 switch (func) { 154 case MMAP_CHECK: 155 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); 156 break; 157 case BPRM_CHECK: 158 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); 159 break; 160 case CREDS_CHECK: 161 iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED); 162 break; 163 case FILE_CHECK: 164 case POST_SETATTR: 165 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); 166 break; 167 case MODULE_CHECK ... MAX_CHECK - 1: 168 default: 169 iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED); 170 break; 171 } 172 } 173 174 enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, 175 int xattr_len) 176 { 177 struct signature_v2_hdr *sig; 178 enum hash_algo ret; 179 180 if (!xattr_value || xattr_len < 2) 181 /* return default hash algo */ 182 return ima_hash_algo; 183 184 switch (xattr_value->type) { 185 case EVM_IMA_XATTR_DIGSIG: 186 sig = (typeof(sig))xattr_value; 187 if (sig->version != 2 || xattr_len <= sizeof(*sig)) 188 return ima_hash_algo; 189 return sig->hash_algo; 190 break; 191 case IMA_XATTR_DIGEST_NG: 192 /* first byte contains algorithm id */ 193 ret = xattr_value->data[0]; 194 if (ret < HASH_ALGO__LAST) 195 return ret; 196 break; 197 case IMA_XATTR_DIGEST: 198 /* this is for backward compatibility */ 199 if (xattr_len == 21) { 200 unsigned int zero = 0; 201 if (!memcmp(&xattr_value->data[16], &zero, 4)) 202 return HASH_ALGO_MD5; 203 else 204 return HASH_ALGO_SHA1; 205 } else if (xattr_len == 17) 206 return HASH_ALGO_MD5; 207 break; 208 } 209 210 /* return default hash algo */ 211 return ima_hash_algo; 212 } 213 214 int ima_read_xattr(struct dentry *dentry, 215 struct evm_ima_xattr_data **xattr_value) 216 { 217 ssize_t ret; 218 219 ret = vfs_getxattr_alloc(&init_user_ns, dentry, XATTR_NAME_IMA, 220 (char **)xattr_value, 0, GFP_NOFS); 221 if (ret == -EOPNOTSUPP) 222 ret = 0; 223 return ret; 224 } 225 226 /* 227 * xattr_verify - verify xattr digest or signature 228 * 229 * Verify whether the hash or signature matches the file contents. 230 * 231 * Return 0 on success, error code otherwise. 232 */ 233 static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint, 234 struct evm_ima_xattr_data *xattr_value, int xattr_len, 235 enum integrity_status *status, const char **cause) 236 { 237 int rc = -EINVAL, hash_start = 0; 238 239 switch (xattr_value->type) { 240 case IMA_XATTR_DIGEST_NG: 241 /* first byte contains algorithm id */ 242 hash_start = 1; 243 fallthrough; 244 case IMA_XATTR_DIGEST: 245 if (iint->flags & IMA_DIGSIG_REQUIRED) { 246 *cause = "IMA-signature-required"; 247 *status = INTEGRITY_FAIL; 248 break; 249 } 250 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 251 if (xattr_len - sizeof(xattr_value->type) - hash_start >= 252 iint->ima_hash->length) 253 /* 254 * xattr length may be longer. md5 hash in previous 255 * version occupied 20 bytes in xattr, instead of 16 256 */ 257 rc = memcmp(&xattr_value->data[hash_start], 258 iint->ima_hash->digest, 259 iint->ima_hash->length); 260 else 261 rc = -EINVAL; 262 if (rc) { 263 *cause = "invalid-hash"; 264 *status = INTEGRITY_FAIL; 265 break; 266 } 267 *status = INTEGRITY_PASS; 268 break; 269 case EVM_IMA_XATTR_DIGSIG: 270 set_bit(IMA_DIGSIG, &iint->atomic_flags); 271 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 272 (const char *)xattr_value, 273 xattr_len, 274 iint->ima_hash->digest, 275 iint->ima_hash->length); 276 if (rc == -EOPNOTSUPP) { 277 *status = INTEGRITY_UNKNOWN; 278 break; 279 } 280 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && 281 func == KEXEC_KERNEL_CHECK) 282 rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM, 283 (const char *)xattr_value, 284 xattr_len, 285 iint->ima_hash->digest, 286 iint->ima_hash->length); 287 if (rc) { 288 *cause = "invalid-signature"; 289 *status = INTEGRITY_FAIL; 290 } else { 291 *status = INTEGRITY_PASS; 292 } 293 break; 294 default: 295 *status = INTEGRITY_UNKNOWN; 296 *cause = "unknown-ima-data"; 297 break; 298 } 299 300 return rc; 301 } 302 303 /* 304 * modsig_verify - verify modsig signature 305 * 306 * Verify whether the signature matches the file contents. 307 * 308 * Return 0 on success, error code otherwise. 309 */ 310 static int modsig_verify(enum ima_hooks func, const struct modsig *modsig, 311 enum integrity_status *status, const char **cause) 312 { 313 int rc; 314 315 rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig); 316 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && 317 func == KEXEC_KERNEL_CHECK) 318 rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM, 319 modsig); 320 if (rc) { 321 *cause = "invalid-signature"; 322 *status = INTEGRITY_FAIL; 323 } else { 324 *status = INTEGRITY_PASS; 325 } 326 327 return rc; 328 } 329 330 /* 331 * ima_check_blacklist - determine if the binary is blacklisted. 332 * 333 * Add the hash of the blacklisted binary to the measurement list, based 334 * on policy. 335 * 336 * Returns -EPERM if the hash is blacklisted. 337 */ 338 int ima_check_blacklist(struct integrity_iint_cache *iint, 339 const struct modsig *modsig, int pcr) 340 { 341 enum hash_algo hash_algo; 342 const u8 *digest = NULL; 343 u32 digestsize = 0; 344 int rc = 0; 345 346 if (!(iint->flags & IMA_CHECK_BLACKLIST)) 347 return 0; 348 349 if (iint->flags & IMA_MODSIG_ALLOWED && modsig) { 350 ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize); 351 352 rc = is_binary_blacklisted(digest, digestsize); 353 if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) 354 process_buffer_measurement(&init_user_ns, NULL, digest, digestsize, 355 "blacklisted-hash", NONE, 356 pcr, NULL, false); 357 } 358 359 return rc; 360 } 361 362 /* 363 * ima_appraise_measurement - appraise file measurement 364 * 365 * Call evm_verifyxattr() to verify the integrity of 'security.ima'. 366 * Assuming success, compare the xattr hash with the collected measurement. 367 * 368 * Return 0 on success, error code otherwise 369 */ 370 int ima_appraise_measurement(enum ima_hooks func, 371 struct integrity_iint_cache *iint, 372 struct file *file, const unsigned char *filename, 373 struct evm_ima_xattr_data *xattr_value, 374 int xattr_len, const struct modsig *modsig) 375 { 376 static const char op[] = "appraise_data"; 377 const char *cause = "unknown"; 378 struct dentry *dentry = file_dentry(file); 379 struct inode *inode = d_backing_inode(dentry); 380 enum integrity_status status = INTEGRITY_UNKNOWN; 381 int rc = xattr_len; 382 bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig; 383 384 /* If not appraising a modsig, we need an xattr. */ 385 if (!(inode->i_opflags & IOP_XATTR) && !try_modsig) 386 return INTEGRITY_UNKNOWN; 387 388 /* If reading the xattr failed and there's no modsig, error out. */ 389 if (rc <= 0 && !try_modsig) { 390 if (rc && rc != -ENODATA) 391 goto out; 392 393 cause = iint->flags & IMA_DIGSIG_REQUIRED ? 394 "IMA-signature-required" : "missing-hash"; 395 status = INTEGRITY_NOLABEL; 396 if (file->f_mode & FMODE_CREATED) 397 iint->flags |= IMA_NEW_FILE; 398 if ((iint->flags & IMA_NEW_FILE) && 399 (!(iint->flags & IMA_DIGSIG_REQUIRED) || 400 (inode->i_size == 0))) 401 status = INTEGRITY_PASS; 402 goto out; 403 } 404 405 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); 406 switch (status) { 407 case INTEGRITY_PASS: 408 case INTEGRITY_PASS_IMMUTABLE: 409 case INTEGRITY_UNKNOWN: 410 break; 411 case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ 412 /* It's fine not to have xattrs when using a modsig. */ 413 if (try_modsig) 414 break; 415 fallthrough; 416 case INTEGRITY_NOLABEL: /* No security.evm xattr. */ 417 cause = "missing-HMAC"; 418 goto out; 419 case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ 420 cause = "invalid-HMAC"; 421 goto out; 422 default: 423 WARN_ONCE(true, "Unexpected integrity status %d\n", status); 424 } 425 426 if (xattr_value) 427 rc = xattr_verify(func, iint, xattr_value, xattr_len, &status, 428 &cause); 429 430 /* 431 * If we have a modsig and either no imasig or the imasig's key isn't 432 * known, then try verifying the modsig. 433 */ 434 if (try_modsig && 435 (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG || 436 rc == -ENOKEY)) 437 rc = modsig_verify(func, modsig, &status, &cause); 438 439 out: 440 /* 441 * File signatures on some filesystems can not be properly verified. 442 * When such filesystems are mounted by an untrusted mounter or on a 443 * system not willing to accept such a risk, fail the file signature 444 * verification. 445 */ 446 if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && 447 ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) || 448 (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) { 449 status = INTEGRITY_FAIL; 450 cause = "unverifiable-signature"; 451 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 452 op, cause, rc, 0); 453 } else if (status != INTEGRITY_PASS) { 454 /* Fix mode, but don't replace file signatures. */ 455 if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig && 456 (!xattr_value || 457 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { 458 if (!ima_fix_xattr(dentry, iint)) 459 status = INTEGRITY_PASS; 460 } 461 462 /* Permit new files with file signatures, but without data. */ 463 if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && 464 xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { 465 status = INTEGRITY_PASS; 466 } 467 468 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 469 op, cause, rc, 0); 470 } else { 471 ima_cache_flags(iint, func); 472 } 473 474 ima_set_cache_status(iint, func, status); 475 return status; 476 } 477 478 /* 479 * ima_update_xattr - update 'security.ima' hash value 480 */ 481 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) 482 { 483 struct dentry *dentry = file_dentry(file); 484 int rc = 0; 485 486 /* do not collect and update hash for digital signatures */ 487 if (test_bit(IMA_DIGSIG, &iint->atomic_flags)) 488 return; 489 490 if ((iint->ima_file_status != INTEGRITY_PASS) && 491 !(iint->flags & IMA_HASH)) 492 return; 493 494 rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL); 495 if (rc < 0) 496 return; 497 498 inode_lock(file_inode(file)); 499 ima_fix_xattr(dentry, iint); 500 inode_unlock(file_inode(file)); 501 } 502 503 /** 504 * ima_inode_post_setattr - reflect file metadata changes 505 * @mnt_userns: user namespace of the mount the inode was found from 506 * @dentry: pointer to the affected dentry 507 * 508 * Changes to a dentry's metadata might result in needing to appraise. 509 * 510 * This function is called from notify_change(), which expects the caller 511 * to lock the inode's i_mutex. 512 */ 513 void ima_inode_post_setattr(struct user_namespace *mnt_userns, 514 struct dentry *dentry) 515 { 516 struct inode *inode = d_backing_inode(dentry); 517 struct integrity_iint_cache *iint; 518 int action; 519 520 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode) 521 || !(inode->i_opflags & IOP_XATTR)) 522 return; 523 524 action = ima_must_appraise(mnt_userns, inode, MAY_ACCESS, POST_SETATTR); 525 if (!action) 526 __vfs_removexattr(&init_user_ns, dentry, XATTR_NAME_IMA); 527 iint = integrity_iint_find(inode); 528 if (iint) { 529 set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags); 530 if (!action) 531 clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); 532 } 533 } 534 535 /* 536 * ima_protect_xattr - protect 'security.ima' 537 * 538 * Ensure that not just anyone can modify or remove 'security.ima'. 539 */ 540 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, 541 const void *xattr_value, size_t xattr_value_len) 542 { 543 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { 544 if (!capable(CAP_SYS_ADMIN)) 545 return -EPERM; 546 return 1; 547 } 548 return 0; 549 } 550 551 static void ima_reset_appraise_flags(struct inode *inode, int digsig) 552 { 553 struct integrity_iint_cache *iint; 554 555 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) 556 return; 557 558 iint = integrity_iint_find(inode); 559 if (!iint) 560 return; 561 iint->measured_pcrs = 0; 562 set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); 563 if (digsig) 564 set_bit(IMA_DIGSIG, &iint->atomic_flags); 565 else 566 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 567 } 568 569 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, 570 const void *xattr_value, size_t xattr_value_len) 571 { 572 const struct evm_ima_xattr_data *xvalue = xattr_value; 573 int result; 574 575 result = ima_protect_xattr(dentry, xattr_name, xattr_value, 576 xattr_value_len); 577 if (result == 1) { 578 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) 579 return -EINVAL; 580 ima_reset_appraise_flags(d_backing_inode(dentry), 581 xvalue->type == EVM_IMA_XATTR_DIGSIG); 582 result = 0; 583 } 584 return result; 585 } 586 587 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) 588 { 589 int result; 590 591 result = ima_protect_xattr(dentry, xattr_name, NULL, 0); 592 if (result == 1) { 593 ima_reset_appraise_flags(d_backing_inode(dentry), 0); 594 result = 0; 595 } 596 return result; 597 } 598