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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2005-2010 IBM Corporation
4 *
5 * Author:
6 * Mimi Zohar <zohar@us.ibm.com>
7 * Kylene Hall <kjhall@us.ibm.com>
8 *
9 * File: evm_main.c
10 * implements evm_inode_setxattr, evm_inode_post_setxattr,
11 * evm_inode_removexattr, evm_verifyxattr, and evm_inode_set_acl.
12 */
13
14#define pr_fmt(fmt) "EVM: "fmt
15
16#include <linux/init.h>
17#include <linux/crypto.h>
18#include <linux/audit.h>
19#include <linux/xattr.h>
20#include <linux/integrity.h>
21#include <linux/evm.h>
22#include <linux/magic.h>
23#include <linux/posix_acl_xattr.h>
24
25#include <crypto/hash.h>
26#include <crypto/hash_info.h>
27#include <crypto/algapi.h>
28#include "evm.h"
29
30int evm_initialized;
31
32static const char * const integrity_status_msg[] = {
33 "pass", "pass_immutable", "fail", "fail_immutable", "no_label",
34 "no_xattrs", "unknown"
35};
36int evm_hmac_attrs;
37
38static struct xattr_list evm_config_default_xattrnames[] = {
39 {
40 .name = XATTR_NAME_SELINUX,
41 .enabled = IS_ENABLED(CONFIG_SECURITY_SELINUX)
42 },
43 {
44 .name = XATTR_NAME_SMACK,
45 .enabled = IS_ENABLED(CONFIG_SECURITY_SMACK)
46 },
47 {
48 .name = XATTR_NAME_SMACKEXEC,
49 .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
50 },
51 {
52 .name = XATTR_NAME_SMACKTRANSMUTE,
53 .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
54 },
55 {
56 .name = XATTR_NAME_SMACKMMAP,
57 .enabled = IS_ENABLED(CONFIG_EVM_EXTRA_SMACK_XATTRS)
58 },
59 {
60 .name = XATTR_NAME_APPARMOR,
61 .enabled = IS_ENABLED(CONFIG_SECURITY_APPARMOR)
62 },
63 {
64 .name = XATTR_NAME_IMA,
65 .enabled = IS_ENABLED(CONFIG_IMA_APPRAISE)
66 },
67 {
68 .name = XATTR_NAME_CAPS,
69 .enabled = true
70 },
71};
72
73LIST_HEAD(evm_config_xattrnames);
74
75static int evm_fixmode __ro_after_init;
76static int __init evm_set_fixmode(char *str)
77{
78 if (strncmp(str, "fix", 3) == 0)
79 evm_fixmode = 1;
80 else
81 pr_err("invalid \"%s\" mode", str);
82
83 return 1;
84}
85__setup("evm=", evm_set_fixmode);
86
87static void __init evm_init_config(void)
88{
89 int i, xattrs;
90
91 xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
92
93 pr_info("Initialising EVM extended attributes:\n");
94 for (i = 0; i < xattrs; i++) {
95 pr_info("%s%s\n", evm_config_default_xattrnames[i].name,
96 !evm_config_default_xattrnames[i].enabled ?
97 " (disabled)" : "");
98 list_add_tail(&evm_config_default_xattrnames[i].list,
99 &evm_config_xattrnames);
100 }
101
102#ifdef CONFIG_EVM_ATTR_FSUUID
103 evm_hmac_attrs |= EVM_ATTR_FSUUID;
104#endif
105 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
106}
107
108static bool evm_key_loaded(void)
109{
110 return (bool)(evm_initialized & EVM_KEY_MASK);
111}
112
113/*
114 * This function determines whether or not it is safe to ignore verification
115 * errors, based on the ability of EVM to calculate HMACs. If the HMAC key
116 * is not loaded, and it cannot be loaded in the future due to the
117 * EVM_SETUP_COMPLETE initialization flag, allowing an operation despite the
118 * attrs/xattrs being found invalid will not make them valid.
119 */
120static bool evm_hmac_disabled(void)
121{
122 if (evm_initialized & EVM_INIT_HMAC)
123 return false;
124
125 if (!(evm_initialized & EVM_SETUP_COMPLETE))
126 return false;
127
128 return true;
129}
130
131static int evm_find_protected_xattrs(struct dentry *dentry)
132{
133 struct inode *inode = d_backing_inode(dentry);
134 struct xattr_list *xattr;
135 int error;
136 int count = 0;
137
138 if (!(inode->i_opflags & IOP_XATTR))
139 return -EOPNOTSUPP;
140
141 list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
142 error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
143 if (error < 0) {
144 if (error == -ENODATA)
145 continue;
146 return error;
147 }
148 count++;
149 }
150
151 return count;
152}
153
154/*
155 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
156 *
157 * Compute the HMAC on the dentry's protected set of extended attributes
158 * and compare it against the stored security.evm xattr.
159 *
160 * For performance:
161 * - use the previoulsy retrieved xattr value and length to calculate the
162 * HMAC.)
163 * - cache the verification result in the iint, when available.
164 *
165 * Returns integrity status
166 */
167static enum integrity_status evm_verify_hmac(struct dentry *dentry,
168 const char *xattr_name,
169 char *xattr_value,
170 size_t xattr_value_len,
171 struct integrity_iint_cache *iint)
172{
173 struct evm_ima_xattr_data *xattr_data = NULL;
174 struct signature_v2_hdr *hdr;
175 enum integrity_status evm_status = INTEGRITY_PASS;
176 struct evm_digest digest;
177 struct inode *inode;
178 int rc, xattr_len, evm_immutable = 0;
179
180 if (iint && (iint->evm_status == INTEGRITY_PASS ||
181 iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
182 return iint->evm_status;
183
184 /* if status is not PASS, try to check again - against -ENOMEM */
185
186 /* first need to know the sig type */
187 rc = vfs_getxattr_alloc(&init_user_ns, dentry, XATTR_NAME_EVM,
188 (char **)&xattr_data, 0, GFP_NOFS);
189 if (rc <= 0) {
190 evm_status = INTEGRITY_FAIL;
191 if (rc == -ENODATA) {
192 rc = evm_find_protected_xattrs(dentry);
193 if (rc > 0)
194 evm_status = INTEGRITY_NOLABEL;
195 else if (rc == 0)
196 evm_status = INTEGRITY_NOXATTRS; /* new file */
197 } else if (rc == -EOPNOTSUPP) {
198 evm_status = INTEGRITY_UNKNOWN;
199 }
200 goto out;
201 }
202
203 xattr_len = rc;
204
205 /* check value type */
206 switch (xattr_data->type) {
207 case EVM_XATTR_HMAC:
208 if (xattr_len != sizeof(struct evm_xattr)) {
209 evm_status = INTEGRITY_FAIL;
210 goto out;
211 }
212
213 digest.hdr.algo = HASH_ALGO_SHA1;
214 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
215 xattr_value_len, &digest);
216 if (rc)
217 break;
218 rc = crypto_memneq(xattr_data->data, digest.digest,
219 SHA1_DIGEST_SIZE);
220 if (rc)
221 rc = -EINVAL;
222 break;
223 case EVM_XATTR_PORTABLE_DIGSIG:
224 evm_immutable = 1;
225 fallthrough;
226 case EVM_IMA_XATTR_DIGSIG:
227 /* accept xattr with non-empty signature field */
228 if (xattr_len <= sizeof(struct signature_v2_hdr)) {
229 evm_status = INTEGRITY_FAIL;
230 goto out;
231 }
232
233 hdr = (struct signature_v2_hdr *)xattr_data;
234 digest.hdr.algo = hdr->hash_algo;
235 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
236 xattr_value_len, xattr_data->type, &digest);
237 if (rc)
238 break;
239 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
240 (const char *)xattr_data, xattr_len,
241 digest.digest, digest.hdr.length);
242 if (!rc) {
243 inode = d_backing_inode(dentry);
244
245 if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
246 if (iint)
247 iint->flags |= EVM_IMMUTABLE_DIGSIG;
248 evm_status = INTEGRITY_PASS_IMMUTABLE;
249 } else if (!IS_RDONLY(inode) &&
250 !(inode->i_sb->s_readonly_remount) &&
251 !IS_IMMUTABLE(inode)) {
252 evm_update_evmxattr(dentry, xattr_name,
253 xattr_value,
254 xattr_value_len);
255 }
256 }
257 break;
258 default:
259 rc = -EINVAL;
260 break;
261 }
262
263 if (rc) {
264 if (rc == -ENODATA)
265 evm_status = INTEGRITY_NOXATTRS;
266 else if (evm_immutable)
267 evm_status = INTEGRITY_FAIL_IMMUTABLE;
268 else
269 evm_status = INTEGRITY_FAIL;
270 }
271 pr_debug("digest: (%d) [%*phN]\n", digest.hdr.length, digest.hdr.length,
272 digest.digest);
273out:
274 if (iint)
275 iint->evm_status = evm_status;
276 kfree(xattr_data);
277 return evm_status;
278}
279
280static int evm_protected_xattr_common(const char *req_xattr_name,
281 bool all_xattrs)
282{
283 int namelen;
284 int found = 0;
285 struct xattr_list *xattr;
286
287 namelen = strlen(req_xattr_name);
288 list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
289 if (!all_xattrs && !xattr->enabled)
290 continue;
291
292 if ((strlen(xattr->name) == namelen)
293 && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
294 found = 1;
295 break;
296 }
297 if (strncmp(req_xattr_name,
298 xattr->name + XATTR_SECURITY_PREFIX_LEN,
299 strlen(req_xattr_name)) == 0) {
300 found = 1;
301 break;
302 }
303 }
304
305 return found;
306}
307
308static int evm_protected_xattr(const char *req_xattr_name)
309{
310 return evm_protected_xattr_common(req_xattr_name, false);
311}
312
313int evm_protected_xattr_if_enabled(const char *req_xattr_name)
314{
315 return evm_protected_xattr_common(req_xattr_name, true);
316}
317
318/**
319 * evm_read_protected_xattrs - read EVM protected xattr names, lengths, values
320 * @dentry: dentry of the read xattrs
321 * @inode: inode of the read xattrs
322 * @buffer: buffer xattr names, lengths or values are copied to
323 * @buffer_size: size of buffer
324 * @type: n: names, l: lengths, v: values
325 * @canonical_fmt: data format (true: little endian, false: native format)
326 *
327 * Read protected xattr names (separated by |), lengths (u32) or values for a
328 * given dentry and return the total size of copied data. If buffer is NULL,
329 * just return the total size.
330 *
331 * Returns the total size on success, a negative value on error.
332 */
333int evm_read_protected_xattrs(struct dentry *dentry, u8 *buffer,
334 int buffer_size, char type, bool canonical_fmt)
335{
336 struct xattr_list *xattr;
337 int rc, size, total_size = 0;
338
339 list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
340 rc = __vfs_getxattr(dentry, d_backing_inode(dentry),
341 xattr->name, NULL, 0);
342 if (rc < 0 && rc == -ENODATA)
343 continue;
344 else if (rc < 0)
345 return rc;
346
347 switch (type) {
348 case 'n':
349 size = strlen(xattr->name) + 1;
350 if (buffer) {
351 if (total_size)
352 *(buffer + total_size - 1) = '|';
353
354 memcpy(buffer + total_size, xattr->name, size);
355 }
356 break;
357 case 'l':
358 size = sizeof(u32);
359 if (buffer) {
360 if (canonical_fmt)
361 rc = (__force int)cpu_to_le32(rc);
362
363 *(u32 *)(buffer + total_size) = rc;
364 }
365 break;
366 case 'v':
367 size = rc;
368 if (buffer) {
369 rc = __vfs_getxattr(dentry,
370 d_backing_inode(dentry), xattr->name,
371 buffer + total_size,
372 buffer_size - total_size);
373 if (rc < 0)
374 return rc;
375 }
376 break;
377 default:
378 return -EINVAL;
379 }
380
381 total_size += size;
382 }
383
384 return total_size;
385}
386
387/**
388 * evm_verifyxattr - verify the integrity of the requested xattr
389 * @dentry: object of the verify xattr
390 * @xattr_name: requested xattr
391 * @xattr_value: requested xattr value
392 * @xattr_value_len: requested xattr value length
393 *
394 * Calculate the HMAC for the given dentry and verify it against the stored
395 * security.evm xattr. For performance, use the xattr value and length
396 * previously retrieved to calculate the HMAC.
397 *
398 * Returns the xattr integrity status.
399 *
400 * This function requires the caller to lock the inode's i_mutex before it
401 * is executed.
402 */
403enum integrity_status evm_verifyxattr(struct dentry *dentry,
404 const char *xattr_name,
405 void *xattr_value, size_t xattr_value_len,
406 struct integrity_iint_cache *iint)
407{
408 if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
409 return INTEGRITY_UNKNOWN;
410
411 if (!iint) {
412 iint = integrity_iint_find(d_backing_inode(dentry));
413 if (!iint)
414 return INTEGRITY_UNKNOWN;
415 }
416 return evm_verify_hmac(dentry, xattr_name, xattr_value,
417 xattr_value_len, iint);
418}
419EXPORT_SYMBOL_GPL(evm_verifyxattr);
420
421/*
422 * evm_verify_current_integrity - verify the dentry's metadata integrity
423 * @dentry: pointer to the affected dentry
424 *
425 * Verify and return the dentry's metadata integrity. The exceptions are
426 * before EVM is initialized or in 'fix' mode.
427 */
428static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
429{
430 struct inode *inode = d_backing_inode(dentry);
431
432 if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
433 return INTEGRITY_PASS;
434 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
435}
436
437/*
438 * evm_xattr_change - check if passed xattr value differs from current value
439 * @mnt_userns: user namespace of the idmapped mount
440 * @dentry: pointer to the affected dentry
441 * @xattr_name: requested xattr
442 * @xattr_value: requested xattr value
443 * @xattr_value_len: requested xattr value length
444 *
445 * Check if passed xattr value differs from current value.
446 *
447 * Returns 1 if passed xattr value differs from current value, 0 otherwise.
448 */
449static int evm_xattr_change(struct user_namespace *mnt_userns,
450 struct dentry *dentry, const char *xattr_name,
451 const void *xattr_value, size_t xattr_value_len)
452{
453 char *xattr_data = NULL;
454 int rc = 0;
455
456 rc = vfs_getxattr_alloc(&init_user_ns, dentry, xattr_name, &xattr_data,
457 0, GFP_NOFS);
458 if (rc < 0) {
459 rc = 1;
460 goto out;
461 }
462
463 if (rc == xattr_value_len)
464 rc = !!memcmp(xattr_value, xattr_data, rc);
465 else
466 rc = 1;
467
468out:
469 kfree(xattr_data);
470 return rc;
471}
472
473/*
474 * evm_protect_xattr - protect the EVM extended attribute
475 *
476 * Prevent security.evm from being modified or removed without the
477 * necessary permissions or when the existing value is invalid.
478 *
479 * The posix xattr acls are 'system' prefixed, which normally would not
480 * affect security.evm. An interesting side affect of writing posix xattr
481 * acls is their modifying of the i_mode, which is included in security.evm.
482 * For posix xattr acls only, permit security.evm, even if it currently
483 * doesn't exist, to be updated unless the EVM signature is immutable.
484 */
485static int evm_protect_xattr(struct user_namespace *mnt_userns,
486 struct dentry *dentry, const char *xattr_name,
487 const void *xattr_value, size_t xattr_value_len)
488{
489 enum integrity_status evm_status;
490
491 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
492 if (!capable(CAP_SYS_ADMIN))
493 return -EPERM;
494 } else if (!evm_protected_xattr(xattr_name)) {
495 if (!posix_xattr_acl(xattr_name))
496 return 0;
497 evm_status = evm_verify_current_integrity(dentry);
498 if ((evm_status == INTEGRITY_PASS) ||
499 (evm_status == INTEGRITY_NOXATTRS))
500 return 0;
501 goto out;
502 }
503
504 evm_status = evm_verify_current_integrity(dentry);
505 if (evm_status == INTEGRITY_NOXATTRS) {
506 struct integrity_iint_cache *iint;
507
508 /* Exception if the HMAC is not going to be calculated. */
509 if (evm_hmac_disabled())
510 return 0;
511
512 iint = integrity_iint_find(d_backing_inode(dentry));
513 if (iint && (iint->flags & IMA_NEW_FILE))
514 return 0;
515
516 /* exception for pseudo filesystems */
517 if (dentry->d_sb->s_magic == TMPFS_MAGIC
518 || dentry->d_sb->s_magic == SYSFS_MAGIC)
519 return 0;
520
521 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
522 dentry->d_inode, dentry->d_name.name,
523 "update_metadata",
524 integrity_status_msg[evm_status],
525 -EPERM, 0);
526 }
527out:
528 /* Exception if the HMAC is not going to be calculated. */
529 if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
530 evm_status == INTEGRITY_UNKNOWN))
531 return 0;
532
533 /*
534 * Writing other xattrs is safe for portable signatures, as portable
535 * signatures are immutable and can never be updated.
536 */
537 if (evm_status == INTEGRITY_FAIL_IMMUTABLE)
538 return 0;
539
540 if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
541 !evm_xattr_change(mnt_userns, dentry, xattr_name, xattr_value,
542 xattr_value_len))
543 return 0;
544
545 if (evm_status != INTEGRITY_PASS &&
546 evm_status != INTEGRITY_PASS_IMMUTABLE)
547 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
548 dentry->d_name.name, "appraise_metadata",
549 integrity_status_msg[evm_status],
550 -EPERM, 0);
551 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
552}
553
554/**
555 * evm_inode_setxattr - protect the EVM extended attribute
556 * @mnt_userns: user namespace of the idmapped mount
557 * @dentry: pointer to the affected dentry
558 * @xattr_name: pointer to the affected extended attribute name
559 * @xattr_value: pointer to the new extended attribute value
560 * @xattr_value_len: pointer to the new extended attribute value length
561 *
562 * Before allowing the 'security.evm' protected xattr to be updated,
563 * verify the existing value is valid. As only the kernel should have
564 * access to the EVM encrypted key needed to calculate the HMAC, prevent
565 * userspace from writing HMAC value. Writing 'security.evm' requires
566 * requires CAP_SYS_ADMIN privileges.
567 */
568int evm_inode_setxattr(struct user_namespace *mnt_userns, struct dentry *dentry,
569 const char *xattr_name, const void *xattr_value,
570 size_t xattr_value_len)
571{
572 const struct evm_ima_xattr_data *xattr_data = xattr_value;
573
574 /* Policy permits modification of the protected xattrs even though
575 * there's no HMAC key loaded
576 */
577 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
578 return 0;
579
580 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
581 if (!xattr_value_len)
582 return -EINVAL;
583 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
584 xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
585 return -EPERM;
586 }
587 return evm_protect_xattr(mnt_userns, dentry, xattr_name, xattr_value,
588 xattr_value_len);
589}
590
591/**
592 * evm_inode_removexattr - protect the EVM extended attribute
593 * @mnt_userns: user namespace of the idmapped mount
594 * @dentry: pointer to the affected dentry
595 * @xattr_name: pointer to the affected extended attribute name
596 *
597 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
598 * the current value is valid.
599 */
600int evm_inode_removexattr(struct user_namespace *mnt_userns,
601 struct dentry *dentry, const char *xattr_name)
602{
603 /* Policy permits modification of the protected xattrs even though
604 * there's no HMAC key loaded
605 */
606 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
607 return 0;
608
609 return evm_protect_xattr(mnt_userns, dentry, xattr_name, NULL, 0);
610}
611
612#ifdef CONFIG_FS_POSIX_ACL
613static int evm_inode_set_acl_change(struct user_namespace *mnt_userns,
614 struct dentry *dentry, const char *name,
615 struct posix_acl *kacl)
616{
617 int rc;
618
619 umode_t mode;
620 struct inode *inode = d_backing_inode(dentry);
621
622 if (!kacl)
623 return 1;
624
625 rc = posix_acl_update_mode(mnt_userns, inode, &mode, &kacl);
626 if (rc || (inode->i_mode != mode))
627 return 1;
628
629 return 0;
630}
631#else
632static inline int evm_inode_set_acl_change(struct user_namespace *mnt_userns,
633 struct dentry *dentry,
634 const char *name,
635 struct posix_acl *kacl)
636{
637 return 0;
638}
639#endif
640
641/**
642 * evm_inode_set_acl - protect the EVM extended attribute from posix acls
643 * @mnt_userns: user namespace of the idmapped mount
644 * @dentry: pointer to the affected dentry
645 * @acl_name: name of the posix acl
646 * @kacl: pointer to the posix acls
647 *
648 * Prevent modifying posix acls causing the EVM HMAC to be re-calculated
649 * and 'security.evm' xattr updated, unless the existing 'security.evm' is
650 * valid.
651 */
652int evm_inode_set_acl(struct user_namespace *mnt_userns, struct dentry *dentry,
653 const char *acl_name, struct posix_acl *kacl)
654{
655 enum integrity_status evm_status;
656
657 /* Policy permits modification of the protected xattrs even though
658 * there's no HMAC key loaded
659 */
660 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
661 return 0;
662
663 evm_status = evm_verify_current_integrity(dentry);
664 if ((evm_status == INTEGRITY_PASS) ||
665 (evm_status == INTEGRITY_NOXATTRS))
666 return 0;
667
668 /* Exception if the HMAC is not going to be calculated. */
669 if (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
670 evm_status == INTEGRITY_UNKNOWN))
671 return 0;
672
673 /*
674 * Writing other xattrs is safe for portable signatures, as portable
675 * signatures are immutable and can never be updated.
676 */
677 if (evm_status == INTEGRITY_FAIL_IMMUTABLE)
678 return 0;
679
680 if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
681 !evm_inode_set_acl_change(mnt_userns, dentry, acl_name, kacl))
682 return 0;
683
684 if (evm_status != INTEGRITY_PASS_IMMUTABLE)
685 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
686 dentry->d_name.name, "appraise_metadata",
687 integrity_status_msg[evm_status],
688 -EPERM, 0);
689 return -EPERM;
690}
691
692static void evm_reset_status(struct inode *inode)
693{
694 struct integrity_iint_cache *iint;
695
696 iint = integrity_iint_find(inode);
697 if (iint)
698 iint->evm_status = INTEGRITY_UNKNOWN;
699}
700
701/**
702 * evm_revalidate_status - report whether EVM status re-validation is necessary
703 * @xattr_name: pointer to the affected extended attribute name
704 *
705 * Report whether callers of evm_verifyxattr() should re-validate the
706 * EVM status.
707 *
708 * Return true if re-validation is necessary, false otherwise.
709 */
710bool evm_revalidate_status(const char *xattr_name)
711{
712 if (!evm_key_loaded())
713 return false;
714
715 /* evm_inode_post_setattr() passes NULL */
716 if (!xattr_name)
717 return true;
718
719 if (!evm_protected_xattr(xattr_name) && !posix_xattr_acl(xattr_name) &&
720 strcmp(xattr_name, XATTR_NAME_EVM))
721 return false;
722
723 return true;
724}
725
726/**
727 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
728 * @dentry: pointer to the affected dentry
729 * @xattr_name: pointer to the affected extended attribute name
730 * @xattr_value: pointer to the new extended attribute value
731 * @xattr_value_len: pointer to the new extended attribute value length
732 *
733 * Update the HMAC stored in 'security.evm' to reflect the change.
734 *
735 * No need to take the i_mutex lock here, as this function is called from
736 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
737 * i_mutex lock.
738 */
739void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
740 const void *xattr_value, size_t xattr_value_len)
741{
742 if (!evm_revalidate_status(xattr_name))
743 return;
744
745 evm_reset_status(dentry->d_inode);
746
747 if (!strcmp(xattr_name, XATTR_NAME_EVM))
748 return;
749
750 if (!(evm_initialized & EVM_INIT_HMAC))
751 return;
752
753 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
754}
755
756/**
757 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
758 * @dentry: pointer to the affected dentry
759 * @xattr_name: pointer to the affected extended attribute name
760 *
761 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
762 *
763 * No need to take the i_mutex lock here, as this function is called from
764 * vfs_removexattr() which takes the i_mutex.
765 */
766void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
767{
768 if (!evm_revalidate_status(xattr_name))
769 return;
770
771 evm_reset_status(dentry->d_inode);
772
773 if (!strcmp(xattr_name, XATTR_NAME_EVM))
774 return;
775
776 if (!(evm_initialized & EVM_INIT_HMAC))
777 return;
778
779 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
780}
781
782static int evm_attr_change(struct user_namespace *mnt_userns,
783 struct dentry *dentry, struct iattr *attr)
784{
785 struct inode *inode = d_backing_inode(dentry);
786 unsigned int ia_valid = attr->ia_valid;
787
788 if (!i_uid_needs_update(mnt_userns, attr, inode) &&
789 !i_gid_needs_update(mnt_userns, attr, inode) &&
790 (!(ia_valid & ATTR_MODE) || attr->ia_mode == inode->i_mode))
791 return 0;
792
793 return 1;
794}
795
796/**
797 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
798 * @dentry: pointer to the affected dentry
799 *
800 * Permit update of file attributes when files have a valid EVM signature,
801 * except in the case of them having an immutable portable signature.
802 */
803int evm_inode_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
804 struct iattr *attr)
805{
806 unsigned int ia_valid = attr->ia_valid;
807 enum integrity_status evm_status;
808
809 /* Policy permits modification of the protected attrs even though
810 * there's no HMAC key loaded
811 */
812 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
813 return 0;
814
815 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
816 return 0;
817 evm_status = evm_verify_current_integrity(dentry);
818 /*
819 * Writing attrs is safe for portable signatures, as portable signatures
820 * are immutable and can never be updated.
821 */
822 if ((evm_status == INTEGRITY_PASS) ||
823 (evm_status == INTEGRITY_NOXATTRS) ||
824 (evm_status == INTEGRITY_FAIL_IMMUTABLE) ||
825 (evm_hmac_disabled() && (evm_status == INTEGRITY_NOLABEL ||
826 evm_status == INTEGRITY_UNKNOWN)))
827 return 0;
828
829 if (evm_status == INTEGRITY_PASS_IMMUTABLE &&
830 !evm_attr_change(mnt_userns, dentry, attr))
831 return 0;
832
833 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
834 dentry->d_name.name, "appraise_metadata",
835 integrity_status_msg[evm_status], -EPERM, 0);
836 return -EPERM;
837}
838
839/**
840 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
841 * @dentry: pointer to the affected dentry
842 * @ia_valid: for the UID and GID status
843 *
844 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
845 * changes.
846 *
847 * This function is called from notify_change(), which expects the caller
848 * to lock the inode's i_mutex.
849 */
850void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
851{
852 if (!evm_revalidate_status(NULL))
853 return;
854
855 evm_reset_status(dentry->d_inode);
856
857 if (!(evm_initialized & EVM_INIT_HMAC))
858 return;
859
860 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
861 evm_update_evmxattr(dentry, NULL, NULL, 0);
862}
863
864/*
865 * evm_inode_init_security - initializes security.evm HMAC value
866 */
867int evm_inode_init_security(struct inode *inode,
868 const struct xattr *lsm_xattr,
869 struct xattr *evm_xattr)
870{
871 struct evm_xattr *xattr_data;
872 int rc;
873
874 if (!(evm_initialized & EVM_INIT_HMAC) ||
875 !evm_protected_xattr(lsm_xattr->name))
876 return 0;
877
878 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
879 if (!xattr_data)
880 return -ENOMEM;
881
882 xattr_data->data.type = EVM_XATTR_HMAC;
883 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
884 if (rc < 0)
885 goto out;
886
887 evm_xattr->value = xattr_data;
888 evm_xattr->value_len = sizeof(*xattr_data);
889 evm_xattr->name = XATTR_EVM_SUFFIX;
890 return 0;
891out:
892 kfree(xattr_data);
893 return rc;
894}
895EXPORT_SYMBOL_GPL(evm_inode_init_security);
896
897#ifdef CONFIG_EVM_LOAD_X509
898void __init evm_load_x509(void)
899{
900 int rc;
901
902 rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
903 if (!rc)
904 evm_initialized |= EVM_INIT_X509;
905}
906#endif
907
908static int __init init_evm(void)
909{
910 int error;
911 struct list_head *pos, *q;
912
913 evm_init_config();
914
915 error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
916 if (error)
917 goto error;
918
919 error = evm_init_secfs();
920 if (error < 0) {
921 pr_info("Error registering secfs\n");
922 goto error;
923 }
924
925error:
926 if (error != 0) {
927 if (!list_empty(&evm_config_xattrnames)) {
928 list_for_each_safe(pos, q, &evm_config_xattrnames)
929 list_del(pos);
930 }
931 }
932
933 return error;
934}
935
936late_initcall(init_evm);