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
23static char *ima_appraise_cmdline_default __initdata;
24core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0);
25
26void __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 */
63bool 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 */
73int 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: &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
87static 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 */
108enum 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
128static 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
154static 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
178enum 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(p: &xattr_value->data[16], q: &zero, size: 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
224int 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(idmap: &nop_mnt_idmap, dentry, XATTR_NAME_IMA,
230 xattr_value: (char **)xattr_value, size: 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 */
251static 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(buf: &file_id, len: 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 */
277static 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, addr: &iint->atomic_flags);
302 } else {
303 set_bit(IMA_DIGSIG, addr: &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(p: &xattr_value->data[hash_start],
312 q: iint->ima_hash->digest,
313 size: 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, addr: &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 sig: (const char *)xattr_value,
341 siglen: xattr_len,
342 digest: iint->ima_hash->digest,
343 digestlen: 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 sig: (const char *)xattr_value,
352 siglen: xattr_len,
353 digest: iint->ima_hash->digest,
354 digestlen: 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, addr: &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(type: IMA_VERITY_DIGSIG, algo: iint->ima_hash->algo,
381 digest: iint->ima_hash->digest, hash: &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 sig: (const char *)xattr_value,
390 siglen: xattr_len, digest: hash.digest,
391 digestlen: 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 */
416static 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 */
444int 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, algo: &hash_algo, digest: &digest, digest_size: &digestsize);
457
458 rc = is_binary_blacklisted(hash: digest, hash_len: digestsize);
459 } else if (iint->flags & IMA_DIGSIG_REQUIRED && iint->ima_hash)
460 rc = is_binary_blacklisted(hash: iint->ima_hash->digest, hash_len: iint->ima_hash->length);
461
462 if ((rc == -EPERM) && (iint->flags & IMA_MEASURE))
463 process_buffer_measurement(idmap: &nop_mnt_idmap, NULL, buf: digest, size: digestsize,
464 eventname: "blacklisted-hash", func: NONE,
465 pcr, NULL, buf_hash: false, NULL, digest_len: 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 */
478int 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(upper: 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 xattr_value_len: 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, addr: &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: &status,
547 cause: &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: &status, cause: &cause);
557
558out:
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, fname: filename,
571 op, cause, result: rc, info: 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, fname: filename,
591 op, cause, result: rc, info: 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 */
603void 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, size: 0, algo: ima_hash_algo, NULL);
617 if (rc < 0)
618 return;
619
620 inode_lock(inode: file_inode(f: file));
621 ima_fix_xattr(dentry, iint);
622 inode_unlock(inode: file_inode(f: 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 */
636static void ima_inode_post_setattr(struct mnt_idmap *idmap,
637 struct dentry *dentry, int ia_valid)
638{
639 struct inode *inode = d_backing_inode(upper: 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, func: POST_SETATTR);
648 iint = ima_iint_find(inode);
649 if (iint) {
650 set_bit(IMA_CHANGE_ATTR, addr: &iint->atomic_flags);
651 if (!action)
652 clear_bit(IMA_UPDATE_XATTR, addr: &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 */
661static 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
672static 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, addr: &iint->atomic_flags);
684 if (digsig)
685 set_bit(IMA_DIGSIG, addr: &iint->atomic_flags);
686 else
687 clear_bit(IMA_DIGSIG, addr: &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 */
703static 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_len: xattr_value_len);
713
714 allowed_hashes = atomic_read(v: &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(name: hash_algo_name[xattr_hash_algo], type: 0, mask: 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, inode: d_inode(dentry), fname: path,
743 op: "set_data", cause: errmsg, result: -EACCES, info: 0);
744
745 kfree(objp: pathbuf);
746
747 return -EACCES;
748}
749
750static 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, xattr_value: 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(inode: d_backing_inode(upper: dentry), digsig);
775 if (result == 1)
776 result = 0;
777 }
778 return result;
779}
780
781static 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(xattr_name: acl_name))
785 ima_reset_appraise_flags(inode: d_backing_inode(upper: dentry), digsig: 0);
786
787 return 0;
788}
789
790static 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, xattr_value_len: 0);
796 if (result == 1 || evm_revalidate_status(xattr_name)) {
797 ima_reset_appraise_flags(inode: d_backing_inode(upper: dentry), digsig: 0);
798 if (result == 1)
799 result = 0;
800 }
801 return result;
802}
803
804static 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
810static 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
818void __init init_ima_appraise_lsm(const struct lsm_id *lsmid)
819{
820 security_add_hooks(hooks: ima_appraise_hooks, ARRAY_SIZE(ima_appraise_hooks),
821 lsmid);
822}
823

source code of linux/security/integrity/ima/ima_appraise.c