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