xref: /linux/security/integrity/ima/ima_appraise.c (revision 4b911a9690d72641879ea6d13cce1de31d346d79)
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 <linux/fsverity.h>
17 #include <keys/system_keyring.h>
18 #include <uapi/linux/fsverity.h>
19 
20 #include "ima.h"
21 
22 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM
23 static char *ima_appraise_cmdline_default __initdata;
24 core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0);
25 
26 void __init ima_appraise_parse_cmdline(void)
27 {
28 	const char *str = ima_appraise_cmdline_default;
29 	bool sb_state = arch_ima_get_secureboot();
30 	int appraisal_state = ima_appraise;
31 
32 	if (!str)
33 		return;
34 
35 	if (strncmp(str, "off", 3) == 0)
36 		appraisal_state = 0;
37 	else if (strncmp(str, "log", 3) == 0)
38 		appraisal_state = IMA_APPRAISE_LOG;
39 	else if (strncmp(str, "fix", 3) == 0)
40 		appraisal_state = IMA_APPRAISE_FIX;
41 	else if (strncmp(str, "enforce", 7) == 0)
42 		appraisal_state = IMA_APPRAISE_ENFORCE;
43 	else
44 		pr_err("invalid \"%s\" appraise option", str);
45 
46 	/* If appraisal state was changed, but secure boot is enabled,
47 	 * keep its default */
48 	if (sb_state) {
49 		if (!(appraisal_state & IMA_APPRAISE_ENFORCE))
50 			pr_info("Secure boot enabled: ignoring ima_appraise=%s option",
51 				str);
52 	} else {
53 		ima_appraise = appraisal_state;
54 	}
55 }
56 #endif
57 
58 /*
59  * is_ima_appraise_enabled - return appraise status
60  *
61  * Only return enabled, if not in ima_appraise="fix" or "log" modes.
62  */
63 bool is_ima_appraise_enabled(void)
64 {
65 	return ima_appraise & IMA_APPRAISE_ENFORCE;
66 }
67 
68 /*
69  * ima_must_appraise - set appraise flag
70  *
71  * Return 1 to appraise or hash
72  */
73 int ima_must_appraise(struct mnt_idmap *idmap, struct inode *inode,
74 		      int mask, enum ima_hooks func)
75 {
76 	u32 secid;
77 
78 	if (!ima_appraise)
79 		return 0;
80 
81 	security_current_getsecid_subj(&secid);
82 	return ima_match_policy(idmap, inode, current_cred(), secid,
83 				func, mask, IMA_APPRAISE | IMA_HASH, NULL,
84 				NULL, NULL, NULL);
85 }
86 
87 static int ima_fix_xattr(struct dentry *dentry, struct ima_iint_cache *iint)
88 {
89 	int rc, offset;
90 	u8 algo = iint->ima_hash->algo;
91 
92 	if (algo <= HASH_ALGO_SHA1) {
93 		offset = 1;
94 		iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST;
95 	} else {
96 		offset = 0;
97 		iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG;
98 		iint->ima_hash->xattr.ng.algo = algo;
99 	}
100 	rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
101 				   &iint->ima_hash->xattr.data[offset],
102 				   (sizeof(iint->ima_hash->xattr) - offset) +
103 				   iint->ima_hash->length, 0);
104 	return rc;
105 }
106 
107 /* Return specific func appraised cached result */
108 enum integrity_status ima_get_cache_status(struct ima_iint_cache *iint,
109 					   enum ima_hooks func)
110 {
111 	switch (func) {
112 	case MMAP_CHECK:
113 	case MMAP_CHECK_REQPROT:
114 		return iint->ima_mmap_status;
115 	case BPRM_CHECK:
116 		return iint->ima_bprm_status;
117 	case CREDS_CHECK:
118 		return iint->ima_creds_status;
119 	case FILE_CHECK:
120 	case POST_SETATTR:
121 		return iint->ima_file_status;
122 	case MODULE_CHECK ... MAX_CHECK - 1:
123 	default:
124 		return iint->ima_read_status;
125 	}
126 }
127 
128 static void ima_set_cache_status(struct ima_iint_cache *iint,
129 				 enum ima_hooks func,
130 				 enum integrity_status status)
131 {
132 	switch (func) {
133 	case MMAP_CHECK:
134 	case MMAP_CHECK_REQPROT:
135 		iint->ima_mmap_status = status;
136 		break;
137 	case BPRM_CHECK:
138 		iint->ima_bprm_status = status;
139 		break;
140 	case CREDS_CHECK:
141 		iint->ima_creds_status = status;
142 		break;
143 	case FILE_CHECK:
144 	case POST_SETATTR:
145 		iint->ima_file_status = status;
146 		break;
147 	case MODULE_CHECK ... MAX_CHECK - 1:
148 	default:
149 		iint->ima_read_status = status;
150 		break;
151 	}
152 }
153 
154 static void ima_cache_flags(struct ima_iint_cache *iint, enum ima_hooks func)
155 {
156 	switch (func) {
157 	case MMAP_CHECK:
158 	case MMAP_CHECK_REQPROT:
159 		iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED);
160 		break;
161 	case BPRM_CHECK:
162 		iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED);
163 		break;
164 	case CREDS_CHECK:
165 		iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED);
166 		break;
167 	case FILE_CHECK:
168 	case POST_SETATTR:
169 		iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
170 		break;
171 	case MODULE_CHECK ... MAX_CHECK - 1:
172 	default:
173 		iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED);
174 		break;
175 	}
176 }
177 
178 enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value,
179 				 int xattr_len)
180 {
181 	struct signature_v2_hdr *sig;
182 	enum hash_algo ret;
183 
184 	if (!xattr_value || xattr_len < 2)
185 		/* return default hash algo */
186 		return ima_hash_algo;
187 
188 	switch (xattr_value->type) {
189 	case IMA_VERITY_DIGSIG:
190 		sig = (typeof(sig))xattr_value;
191 		if (sig->version != 3 || xattr_len <= sizeof(*sig) ||
192 		    sig->hash_algo >= HASH_ALGO__LAST)
193 			return ima_hash_algo;
194 		return sig->hash_algo;
195 	case EVM_IMA_XATTR_DIGSIG:
196 		sig = (typeof(sig))xattr_value;
197 		if (sig->version != 2 || xattr_len <= sizeof(*sig)
198 		    || sig->hash_algo >= HASH_ALGO__LAST)
199 			return ima_hash_algo;
200 		return sig->hash_algo;
201 	case IMA_XATTR_DIGEST_NG:
202 		/* first byte contains algorithm id */
203 		ret = xattr_value->data[0];
204 		if (ret < HASH_ALGO__LAST)
205 			return ret;
206 		break;
207 	case IMA_XATTR_DIGEST:
208 		/* this is for backward compatibility */
209 		if (xattr_len == 21) {
210 			unsigned int zero = 0;
211 			if (!memcmp(&xattr_value->data[16], &zero, 4))
212 				return HASH_ALGO_MD5;
213 			else
214 				return HASH_ALGO_SHA1;
215 		} else if (xattr_len == 17)
216 			return HASH_ALGO_MD5;
217 		break;
218 	}
219 
220 	/* return default hash algo */
221 	return ima_hash_algo;
222 }
223 
224 int ima_read_xattr(struct dentry *dentry,
225 		   struct evm_ima_xattr_data **xattr_value, int xattr_len)
226 {
227 	int ret;
228 
229 	ret = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_IMA,
230 				 (char **)xattr_value, xattr_len, GFP_NOFS);
231 	if (ret == -EOPNOTSUPP)
232 		ret = 0;
233 	return ret;
234 }
235 
236 /*
237  * calc_file_id_hash - calculate the hash of the ima_file_id struct data
238  * @type: xattr type [enum evm_ima_xattr_type]
239  * @algo: hash algorithm [enum hash_algo]
240  * @digest: pointer to the digest to be hashed
241  * @hash: (out) pointer to the hash
242  *
243  * IMA signature version 3 disambiguates the data that is signed by
244  * indirectly signing the hash of the ima_file_id structure data.
245  *
246  * Signing the ima_file_id struct is currently only supported for
247  * IMA_VERITY_DIGSIG type xattrs.
248  *
249  * Return 0 on success, error code otherwise.
250  */
251 static int calc_file_id_hash(enum evm_ima_xattr_type type,
252 			     enum hash_algo algo, const u8 *digest,
253 			     struct ima_digest_data *hash)
254 {
255 	struct ima_file_id file_id = {
256 		.hash_type = IMA_VERITY_DIGSIG, .hash_algorithm = algo};
257 	unsigned int unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo];
258 
259 	if (type != IMA_VERITY_DIGSIG)
260 		return -EINVAL;
261 
262 	memcpy(file_id.hash, digest, hash_digest_size[algo]);
263 
264 	hash->algo = algo;
265 	hash->length = hash_digest_size[algo];
266 
267 	return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused, hash);
268 }
269 
270 /*
271  * xattr_verify - verify xattr digest or signature
272  *
273  * Verify whether the hash or signature matches the file contents.
274  *
275  * Return 0 on success, error code otherwise.
276  */
277 static int xattr_verify(enum ima_hooks func, struct ima_iint_cache *iint,
278 			struct evm_ima_xattr_data *xattr_value, int xattr_len,
279 			enum integrity_status *status, const char **cause)
280 {
281 	struct ima_max_digest_data hash;
282 	struct signature_v2_hdr *sig;
283 	int rc = -EINVAL, hash_start = 0;
284 	int mask;
285 
286 	switch (xattr_value->type) {
287 	case IMA_XATTR_DIGEST_NG:
288 		/* first byte contains algorithm id */
289 		hash_start = 1;
290 		fallthrough;
291 	case IMA_XATTR_DIGEST:
292 		if (*status != INTEGRITY_PASS_IMMUTABLE) {
293 			if (iint->flags & IMA_DIGSIG_REQUIRED) {
294 				if (iint->flags & IMA_VERITY_REQUIRED)
295 					*cause = "verity-signature-required";
296 				else
297 					*cause = "IMA-signature-required";
298 				*status = INTEGRITY_FAIL;
299 				break;
300 			}
301 			clear_bit(IMA_DIGSIG, &iint->atomic_flags);
302 		} else {
303 			set_bit(IMA_DIGSIG, &iint->atomic_flags);
304 		}
305 		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
306 				iint->ima_hash->length)
307 			/*
308 			 * xattr length may be longer. md5 hash in previous
309 			 * version occupied 20 bytes in xattr, instead of 16
310 			 */
311 			rc = memcmp(&xattr_value->data[hash_start],
312 				    iint->ima_hash->digest,
313 				    iint->ima_hash->length);
314 		else
315 			rc = -EINVAL;
316 		if (rc) {
317 			*cause = "invalid-hash";
318 			*status = INTEGRITY_FAIL;
319 			break;
320 		}
321 		*status = INTEGRITY_PASS;
322 		break;
323 	case EVM_IMA_XATTR_DIGSIG:
324 		set_bit(IMA_DIGSIG, &iint->atomic_flags);
325 
326 		mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED;
327 		if ((iint->flags & mask) == mask) {
328 			*cause = "verity-signature-required";
329 			*status = INTEGRITY_FAIL;
330 			break;
331 		}
332 
333 		sig = (typeof(sig))xattr_value;
334 		if (sig->version >= 3) {
335 			*cause = "invalid-signature-version";
336 			*status = INTEGRITY_FAIL;
337 			break;
338 		}
339 		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
340 					     (const char *)xattr_value,
341 					     xattr_len,
342 					     iint->ima_hash->digest,
343 					     iint->ima_hash->length);
344 		if (rc == -EOPNOTSUPP) {
345 			*status = INTEGRITY_UNKNOWN;
346 			break;
347 		}
348 		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
349 		    func == KEXEC_KERNEL_CHECK)
350 			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
351 						     (const char *)xattr_value,
352 						     xattr_len,
353 						     iint->ima_hash->digest,
354 						     iint->ima_hash->length);
355 		if (rc) {
356 			*cause = "invalid-signature";
357 			*status = INTEGRITY_FAIL;
358 		} else {
359 			*status = INTEGRITY_PASS;
360 		}
361 		break;
362 	case IMA_VERITY_DIGSIG:
363 		set_bit(IMA_DIGSIG, &iint->atomic_flags);
364 
365 		if (iint->flags & IMA_DIGSIG_REQUIRED) {
366 			if (!(iint->flags & IMA_VERITY_REQUIRED)) {
367 				*cause = "IMA-signature-required";
368 				*status = INTEGRITY_FAIL;
369 				break;
370 			}
371 		}
372 
373 		sig = (typeof(sig))xattr_value;
374 		if (sig->version != 3) {
375 			*cause = "invalid-signature-version";
376 			*status = INTEGRITY_FAIL;
377 			break;
378 		}
379 
380 		rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo,
381 				       iint->ima_hash->digest, &hash.hdr);
382 		if (rc) {
383 			*cause = "sigv3-hashing-error";
384 			*status = INTEGRITY_FAIL;
385 			break;
386 		}
387 
388 		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
389 					     (const char *)xattr_value,
390 					     xattr_len, hash.digest,
391 					     hash.hdr.length);
392 		if (rc) {
393 			*cause = "invalid-verity-signature";
394 			*status = INTEGRITY_FAIL;
395 		} else {
396 			*status = INTEGRITY_PASS;
397 		}
398 
399 		break;
400 	default:
401 		*status = INTEGRITY_UNKNOWN;
402 		*cause = "unknown-ima-data";
403 		break;
404 	}
405 
406 	return rc;
407 }
408 
409 /*
410  * modsig_verify - verify modsig signature
411  *
412  * Verify whether the signature matches the file contents.
413  *
414  * Return 0 on success, error code otherwise.
415  */
416 static int modsig_verify(enum ima_hooks func, const struct modsig *modsig,
417 			 enum integrity_status *status, const char **cause)
418 {
419 	int rc;
420 
421 	rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig);
422 	if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
423 	    func == KEXEC_KERNEL_CHECK)
424 		rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM,
425 					     modsig);
426 	if (rc) {
427 		*cause = "invalid-signature";
428 		*status = INTEGRITY_FAIL;
429 	} else {
430 		*status = INTEGRITY_PASS;
431 	}
432 
433 	return rc;
434 }
435 
436 /*
437  * ima_check_blacklist - determine if the binary is blacklisted.
438  *
439  * Add the hash of the blacklisted binary to the measurement list, based
440  * on policy.
441  *
442  * Returns -EPERM if the hash is blacklisted.
443  */
444 int ima_check_blacklist(struct ima_iint_cache *iint,
445 			const struct modsig *modsig, int pcr)
446 {
447 	enum hash_algo hash_algo;
448 	const u8 *digest = NULL;
449 	u32 digestsize = 0;
450 	int rc = 0;
451 
452 	if (!(iint->flags & IMA_CHECK_BLACKLIST))
453 		return 0;
454 
455 	if (iint->flags & IMA_MODSIG_ALLOWED && modsig) {
456 		ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize);
457 
458 		rc = is_binary_blacklisted(digest, digestsize);
459 	} else if (iint->flags & IMA_DIGSIG_REQUIRED && iint->ima_hash)
460 		rc = is_binary_blacklisted(iint->ima_hash->digest, iint->ima_hash->length);
461 
462 	if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
463 		process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize,
464 					   "blacklisted-hash", NONE,
465 					   pcr, NULL, false, NULL, 0);
466 
467 	return rc;
468 }
469 
470 /*
471  * ima_appraise_measurement - appraise file measurement
472  *
473  * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
474  * Assuming success, compare the xattr hash with the collected measurement.
475  *
476  * Return 0 on success, error code otherwise
477  */
478 int ima_appraise_measurement(enum ima_hooks func, struct ima_iint_cache *iint,
479 			     struct file *file, const unsigned char *filename,
480 			     struct evm_ima_xattr_data *xattr_value,
481 			     int xattr_len, const struct modsig *modsig)
482 {
483 	static const char op[] = "appraise_data";
484 	const char *cause = "unknown";
485 	struct dentry *dentry = file_dentry(file);
486 	struct inode *inode = d_backing_inode(dentry);
487 	enum integrity_status status = INTEGRITY_UNKNOWN;
488 	int rc = xattr_len;
489 	bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig;
490 
491 	/* If not appraising a modsig, we need an xattr. */
492 	if (!(inode->i_opflags & IOP_XATTR) && !try_modsig)
493 		return INTEGRITY_UNKNOWN;
494 
495 	/* If reading the xattr failed and there's no modsig, error out. */
496 	if (rc <= 0 && !try_modsig) {
497 		if (rc && rc != -ENODATA)
498 			goto out;
499 
500 		if (iint->flags & IMA_DIGSIG_REQUIRED) {
501 			if (iint->flags & IMA_VERITY_REQUIRED)
502 				cause = "verity-signature-required";
503 			else
504 				cause = "IMA-signature-required";
505 		} else {
506 			cause = "missing-hash";
507 		}
508 
509 		status = INTEGRITY_NOLABEL;
510 		if (file->f_mode & FMODE_CREATED)
511 			iint->flags |= IMA_NEW_FILE;
512 		if ((iint->flags & IMA_NEW_FILE) &&
513 		    (!(iint->flags & IMA_DIGSIG_REQUIRED) ||
514 		     (inode->i_size == 0)))
515 			status = INTEGRITY_PASS;
516 		goto out;
517 	}
518 
519 	status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value,
520 				 rc < 0 ? 0 : rc);
521 	switch (status) {
522 	case INTEGRITY_PASS:
523 	case INTEGRITY_PASS_IMMUTABLE:
524 	case INTEGRITY_UNKNOWN:
525 		break;
526 	case INTEGRITY_NOXATTRS:	/* No EVM protected xattrs. */
527 		/* It's fine not to have xattrs when using a modsig. */
528 		if (try_modsig)
529 			break;
530 		fallthrough;
531 	case INTEGRITY_NOLABEL:		/* No security.evm xattr. */
532 		cause = "missing-HMAC";
533 		goto out;
534 	case INTEGRITY_FAIL_IMMUTABLE:
535 		set_bit(IMA_DIGSIG, &iint->atomic_flags);
536 		cause = "invalid-fail-immutable";
537 		goto out;
538 	case INTEGRITY_FAIL:		/* Invalid HMAC/signature. */
539 		cause = "invalid-HMAC";
540 		goto out;
541 	default:
542 		WARN_ONCE(true, "Unexpected integrity status %d\n", status);
543 	}
544 
545 	if (xattr_value)
546 		rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
547 				  &cause);
548 
549 	/*
550 	 * If we have a modsig and either no imasig or the imasig's key isn't
551 	 * known, then try verifying the modsig.
552 	 */
553 	if (try_modsig &&
554 	    (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG ||
555 	     rc == -ENOKEY))
556 		rc = modsig_verify(func, modsig, &status, &cause);
557 
558 out:
559 	/*
560 	 * File signatures on some filesystems can not be properly verified.
561 	 * When such filesystems are mounted by an untrusted mounter or on a
562 	 * system not willing to accept such a risk, fail the file signature
563 	 * verification.
564 	 */
565 	if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
566 	    ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) ||
567 	     (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) {
568 		status = INTEGRITY_FAIL;
569 		cause = "unverifiable-signature";
570 		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
571 				    op, cause, rc, 0);
572 	} else if (status != INTEGRITY_PASS) {
573 		/* Fix mode, but don't replace file signatures. */
574 		if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig &&
575 		    (!xattr_value ||
576 		     xattr_value->type != EVM_IMA_XATTR_DIGSIG)) {
577 			if (!ima_fix_xattr(dentry, iint))
578 				status = INTEGRITY_PASS;
579 		}
580 
581 		/*
582 		 * Permit new files with file/EVM portable signatures, but
583 		 * without data.
584 		 */
585 		if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE &&
586 		    test_bit(IMA_DIGSIG, &iint->atomic_flags)) {
587 			status = INTEGRITY_PASS;
588 		}
589 
590 		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename,
591 				    op, cause, rc, 0);
592 	} else {
593 		ima_cache_flags(iint, func);
594 	}
595 
596 	ima_set_cache_status(iint, func, status);
597 	return status;
598 }
599 
600 /*
601  * ima_update_xattr - update 'security.ima' hash value
602  */
603 void ima_update_xattr(struct ima_iint_cache *iint, struct file *file)
604 {
605 	struct dentry *dentry = file_dentry(file);
606 	int rc = 0;
607 
608 	/* do not collect and update hash for digital signatures */
609 	if (test_bit(IMA_DIGSIG, &iint->atomic_flags))
610 		return;
611 
612 	if ((iint->ima_file_status != INTEGRITY_PASS) &&
613 	    !(iint->flags & IMA_HASH))
614 		return;
615 
616 	rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL);
617 	if (rc < 0)
618 		return;
619 
620 	inode_lock(file_inode(file));
621 	ima_fix_xattr(dentry, iint);
622 	inode_unlock(file_inode(file));
623 }
624 
625 /**
626  * ima_inode_post_setattr - reflect file metadata changes
627  * @idmap:  idmap of the mount the inode was found from
628  * @dentry: pointer to the affected dentry
629  * @ia_valid: for the UID and GID status
630  *
631  * Changes to a dentry's metadata might result in needing to appraise.
632  *
633  * This function is called from notify_change(), which expects the caller
634  * to lock the inode's i_mutex.
635  */
636 static void ima_inode_post_setattr(struct mnt_idmap *idmap,
637 				   struct dentry *dentry, int ia_valid)
638 {
639 	struct inode *inode = d_backing_inode(dentry);
640 	struct ima_iint_cache *iint;
641 	int action;
642 
643 	if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)
644 	    || !(inode->i_opflags & IOP_XATTR))
645 		return;
646 
647 	action = ima_must_appraise(idmap, inode, MAY_ACCESS, POST_SETATTR);
648 	iint = ima_iint_find(inode);
649 	if (iint) {
650 		set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags);
651 		if (!action)
652 			clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
653 	}
654 }
655 
656 /*
657  * ima_protect_xattr - protect 'security.ima'
658  *
659  * Ensure that not just anyone can modify or remove 'security.ima'.
660  */
661 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name,
662 			     const void *xattr_value, size_t xattr_value_len)
663 {
664 	if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) {
665 		if (!capable(CAP_SYS_ADMIN))
666 			return -EPERM;
667 		return 1;
668 	}
669 	return 0;
670 }
671 
672 static void ima_reset_appraise_flags(struct inode *inode, int digsig)
673 {
674 	struct ima_iint_cache *iint;
675 
676 	if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode))
677 		return;
678 
679 	iint = ima_iint_find(inode);
680 	if (!iint)
681 		return;
682 	iint->measured_pcrs = 0;
683 	set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags);
684 	if (digsig)
685 		set_bit(IMA_DIGSIG, &iint->atomic_flags);
686 	else
687 		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
688 }
689 
690 /**
691  * validate_hash_algo() - Block setxattr with unsupported hash algorithms
692  * @dentry: object of the setxattr()
693  * @xattr_value: userland supplied xattr value
694  * @xattr_value_len: length of xattr_value
695  *
696  * The xattr value is mapped to its hash algorithm, and this algorithm
697  * must be built in the kernel for the setxattr to be allowed.
698  *
699  * Emit an audit message when the algorithm is invalid.
700  *
701  * Return: 0 on success, else an error.
702  */
703 static int validate_hash_algo(struct dentry *dentry,
704 			      const struct evm_ima_xattr_data *xattr_value,
705 			      size_t xattr_value_len)
706 {
707 	char *path = NULL, *pathbuf = NULL;
708 	enum hash_algo xattr_hash_algo;
709 	const char *errmsg = "unavailable-hash-algorithm";
710 	unsigned int allowed_hashes;
711 
712 	xattr_hash_algo = ima_get_hash_algo(xattr_value, xattr_value_len);
713 
714 	allowed_hashes = atomic_read(&ima_setxattr_allowed_hash_algorithms);
715 
716 	if (allowed_hashes) {
717 		/* success if the algorithm is allowed in the ima policy */
718 		if (allowed_hashes & (1U << xattr_hash_algo))
719 			return 0;
720 
721 		/*
722 		 * We use a different audit message when the hash algorithm
723 		 * is denied by a policy rule, instead of not being built
724 		 * in the kernel image
725 		 */
726 		errmsg = "denied-hash-algorithm";
727 	} else {
728 		if (likely(xattr_hash_algo == ima_hash_algo))
729 			return 0;
730 
731 		/* allow any xattr using an algorithm built in the kernel */
732 		if (crypto_has_alg(hash_algo_name[xattr_hash_algo], 0, 0))
733 			return 0;
734 	}
735 
736 	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
737 	if (!pathbuf)
738 		return -EACCES;
739 
740 	path = dentry_path(dentry, pathbuf, PATH_MAX);
741 
742 	integrity_audit_msg(AUDIT_INTEGRITY_DATA, d_inode(dentry), path,
743 			    "set_data", errmsg, -EACCES, 0);
744 
745 	kfree(pathbuf);
746 
747 	return -EACCES;
748 }
749 
750 static int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry,
751 			      const char *xattr_name, const void *xattr_value,
752 			      size_t xattr_value_len, int flags)
753 {
754 	const struct evm_ima_xattr_data *xvalue = xattr_value;
755 	int digsig = 0;
756 	int result;
757 	int err;
758 
759 	result = ima_protect_xattr(dentry, xattr_name, xattr_value,
760 				   xattr_value_len);
761 	if (result == 1) {
762 		if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
763 			return -EINVAL;
764 
765 		err = validate_hash_algo(dentry, xvalue, xattr_value_len);
766 		if (err)
767 			return err;
768 
769 		digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG);
770 	} else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) {
771 		digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG);
772 	}
773 	if (result == 1 || evm_revalidate_status(xattr_name)) {
774 		ima_reset_appraise_flags(d_backing_inode(dentry), digsig);
775 		if (result == 1)
776 			result = 0;
777 	}
778 	return result;
779 }
780 
781 static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry,
782 			     const char *acl_name, struct posix_acl *kacl)
783 {
784 	if (evm_revalidate_status(acl_name))
785 		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
786 
787 	return 0;
788 }
789 
790 static int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry,
791 				 const char *xattr_name)
792 {
793 	int result;
794 
795 	result = ima_protect_xattr(dentry, xattr_name, NULL, 0);
796 	if (result == 1 || evm_revalidate_status(xattr_name)) {
797 		ima_reset_appraise_flags(d_backing_inode(dentry), 0);
798 		if (result == 1)
799 			result = 0;
800 	}
801 	return result;
802 }
803 
804 static int ima_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry,
805 				const char *acl_name)
806 {
807 	return ima_inode_set_acl(idmap, dentry, acl_name, NULL);
808 }
809 
810 static struct security_hook_list ima_appraise_hooks[] __ro_after_init = {
811 	LSM_HOOK_INIT(inode_post_setattr, ima_inode_post_setattr),
812 	LSM_HOOK_INIT(inode_setxattr, ima_inode_setxattr),
813 	LSM_HOOK_INIT(inode_set_acl, ima_inode_set_acl),
814 	LSM_HOOK_INIT(inode_removexattr, ima_inode_removexattr),
815 	LSM_HOOK_INIT(inode_remove_acl, ima_inode_remove_acl),
816 };
817 
818 void __init init_ima_appraise_lsm(const struct lsm_id *lsmid)
819 {
820 	security_add_hooks(ima_appraise_hooks, ARRAY_SIZE(ima_appraise_hooks),
821 			   lsmid);
822 }
823