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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, and evm_verifyxattr
12 */
13
14#define pr_fmt(fmt) KBUILD_MODNAME ": " 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
24#include <crypto/hash.h>
25#include <crypto/hash_info.h>
26#include <crypto/algapi.h>
27#include "evm.h"
28
29int evm_initialized;
30
31static const char * const integrity_status_msg[] = {
32 "pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown"
33};
34int evm_hmac_attrs;
35
36static struct xattr_list evm_config_default_xattrnames[] = {
37#ifdef CONFIG_SECURITY_SELINUX
38 {.name = XATTR_NAME_SELINUX},
39#endif
40#ifdef CONFIG_SECURITY_SMACK
41 {.name = XATTR_NAME_SMACK},
42#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
43 {.name = XATTR_NAME_SMACKEXEC},
44 {.name = XATTR_NAME_SMACKTRANSMUTE},
45 {.name = XATTR_NAME_SMACKMMAP},
46#endif
47#endif
48#ifdef CONFIG_SECURITY_APPARMOR
49 {.name = XATTR_NAME_APPARMOR},
50#endif
51#ifdef CONFIG_IMA_APPRAISE
52 {.name = XATTR_NAME_IMA},
53#endif
54 {.name = XATTR_NAME_CAPS},
55};
56
57LIST_HEAD(evm_config_xattrnames);
58
59static int evm_fixmode;
60static int __init evm_set_fixmode(char *str)
61{
62 if (strncmp(str, "fix", 3) == 0)
63 evm_fixmode = 1;
64 return 0;
65}
66__setup("evm=", evm_set_fixmode);
67
68static void __init evm_init_config(void)
69{
70 int i, xattrs;
71
72 xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
73
74 pr_info("Initialising EVM extended attributes:\n");
75 for (i = 0; i < xattrs; i++) {
76 pr_info("%s\n", evm_config_default_xattrnames[i].name);
77 list_add_tail(&evm_config_default_xattrnames[i].list,
78 &evm_config_xattrnames);
79 }
80
81#ifdef CONFIG_EVM_ATTR_FSUUID
82 evm_hmac_attrs |= EVM_ATTR_FSUUID;
83#endif
84 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
85}
86
87static bool evm_key_loaded(void)
88{
89 return (bool)(evm_initialized & EVM_KEY_MASK);
90}
91
92static int evm_find_protected_xattrs(struct dentry *dentry)
93{
94 struct inode *inode = d_backing_inode(dentry);
95 struct xattr_list *xattr;
96 int error;
97 int count = 0;
98
99 if (!(inode->i_opflags & IOP_XATTR))
100 return -EOPNOTSUPP;
101
102 list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
103 error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
104 if (error < 0) {
105 if (error == -ENODATA)
106 continue;
107 return error;
108 }
109 count++;
110 }
111
112 return count;
113}
114
115/*
116 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
117 *
118 * Compute the HMAC on the dentry's protected set of extended attributes
119 * and compare it against the stored security.evm xattr.
120 *
121 * For performance:
122 * - use the previoulsy retrieved xattr value and length to calculate the
123 * HMAC.)
124 * - cache the verification result in the iint, when available.
125 *
126 * Returns integrity status
127 */
128static enum integrity_status evm_verify_hmac(struct dentry *dentry,
129 const char *xattr_name,
130 char *xattr_value,
131 size_t xattr_value_len,
132 struct integrity_iint_cache *iint)
133{
134 struct evm_ima_xattr_data *xattr_data = NULL;
135 struct signature_v2_hdr *hdr;
136 enum integrity_status evm_status = INTEGRITY_PASS;
137 struct evm_digest digest;
138 struct inode *inode;
139 int rc, xattr_len;
140
141 if (iint && (iint->evm_status == INTEGRITY_PASS ||
142 iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
143 return iint->evm_status;
144
145 /* if status is not PASS, try to check again - against -ENOMEM */
146
147 /* first need to know the sig type */
148 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
149 GFP_NOFS);
150 if (rc <= 0) {
151 evm_status = INTEGRITY_FAIL;
152 if (rc == -ENODATA) {
153 rc = evm_find_protected_xattrs(dentry);
154 if (rc > 0)
155 evm_status = INTEGRITY_NOLABEL;
156 else if (rc == 0)
157 evm_status = INTEGRITY_NOXATTRS; /* new file */
158 } else if (rc == -EOPNOTSUPP) {
159 evm_status = INTEGRITY_UNKNOWN;
160 }
161 goto out;
162 }
163
164 xattr_len = rc;
165
166 /* check value type */
167 switch (xattr_data->type) {
168 case EVM_XATTR_HMAC:
169 if (xattr_len != sizeof(struct evm_xattr)) {
170 evm_status = INTEGRITY_FAIL;
171 goto out;
172 }
173
174 digest.hdr.algo = HASH_ALGO_SHA1;
175 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
176 xattr_value_len, &digest);
177 if (rc)
178 break;
179 rc = crypto_memneq(xattr_data->data, digest.digest,
180 SHA1_DIGEST_SIZE);
181 if (rc)
182 rc = -EINVAL;
183 break;
184 case EVM_IMA_XATTR_DIGSIG:
185 case EVM_XATTR_PORTABLE_DIGSIG:
186 hdr = (struct signature_v2_hdr *)xattr_data;
187 digest.hdr.algo = hdr->hash_algo;
188 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
189 xattr_value_len, xattr_data->type, &digest);
190 if (rc)
191 break;
192 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
193 (const char *)xattr_data, xattr_len,
194 digest.digest, digest.hdr.length);
195 if (!rc) {
196 inode = d_backing_inode(dentry);
197
198 if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
199 if (iint)
200 iint->flags |= EVM_IMMUTABLE_DIGSIG;
201 evm_status = INTEGRITY_PASS_IMMUTABLE;
202 } else if (!IS_RDONLY(inode) &&
203 !(inode->i_sb->s_readonly_remount) &&
204 !IS_IMMUTABLE(inode)) {
205 evm_update_evmxattr(dentry, xattr_name,
206 xattr_value,
207 xattr_value_len);
208 }
209 }
210 break;
211 default:
212 rc = -EINVAL;
213 break;
214 }
215
216 if (rc)
217 evm_status = (rc == -ENODATA) ?
218 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
219out:
220 if (iint)
221 iint->evm_status = evm_status;
222 kfree(xattr_data);
223 return evm_status;
224}
225
226static int evm_protected_xattr(const char *req_xattr_name)
227{
228 int namelen;
229 int found = 0;
230 struct xattr_list *xattr;
231
232 namelen = strlen(req_xattr_name);
233 list_for_each_entry_rcu(xattr, &evm_config_xattrnames, list) {
234 if ((strlen(xattr->name) == namelen)
235 && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
236 found = 1;
237 break;
238 }
239 if (strncmp(req_xattr_name,
240 xattr->name + XATTR_SECURITY_PREFIX_LEN,
241 strlen(req_xattr_name)) == 0) {
242 found = 1;
243 break;
244 }
245 }
246
247 return found;
248}
249
250/**
251 * evm_verifyxattr - verify the integrity of the requested xattr
252 * @dentry: object of the verify xattr
253 * @xattr_name: requested xattr
254 * @xattr_value: requested xattr value
255 * @xattr_value_len: requested xattr value length
256 *
257 * Calculate the HMAC for the given dentry and verify it against the stored
258 * security.evm xattr. For performance, use the xattr value and length
259 * previously retrieved to calculate the HMAC.
260 *
261 * Returns the xattr integrity status.
262 *
263 * This function requires the caller to lock the inode's i_mutex before it
264 * is executed.
265 */
266enum integrity_status evm_verifyxattr(struct dentry *dentry,
267 const char *xattr_name,
268 void *xattr_value, size_t xattr_value_len,
269 struct integrity_iint_cache *iint)
270{
271 if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
272 return INTEGRITY_UNKNOWN;
273
274 if (!iint) {
275 iint = integrity_iint_find(d_backing_inode(dentry));
276 if (!iint)
277 return INTEGRITY_UNKNOWN;
278 }
279 return evm_verify_hmac(dentry, xattr_name, xattr_value,
280 xattr_value_len, iint);
281}
282EXPORT_SYMBOL_GPL(evm_verifyxattr);
283
284/*
285 * evm_verify_current_integrity - verify the dentry's metadata integrity
286 * @dentry: pointer to the affected dentry
287 *
288 * Verify and return the dentry's metadata integrity. The exceptions are
289 * before EVM is initialized or in 'fix' mode.
290 */
291static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
292{
293 struct inode *inode = d_backing_inode(dentry);
294
295 if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
296 return 0;
297 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
298}
299
300/*
301 * evm_protect_xattr - protect the EVM extended attribute
302 *
303 * Prevent security.evm from being modified or removed without the
304 * necessary permissions or when the existing value is invalid.
305 *
306 * The posix xattr acls are 'system' prefixed, which normally would not
307 * affect security.evm. An interesting side affect of writing posix xattr
308 * acls is their modifying of the i_mode, which is included in security.evm.
309 * For posix xattr acls only, permit security.evm, even if it currently
310 * doesn't exist, to be updated unless the EVM signature is immutable.
311 */
312static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
313 const void *xattr_value, size_t xattr_value_len)
314{
315 enum integrity_status evm_status;
316
317 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
318 if (!capable(CAP_SYS_ADMIN))
319 return -EPERM;
320 } else if (!evm_protected_xattr(xattr_name)) {
321 if (!posix_xattr_acl(xattr_name))
322 return 0;
323 evm_status = evm_verify_current_integrity(dentry);
324 if ((evm_status == INTEGRITY_PASS) ||
325 (evm_status == INTEGRITY_NOXATTRS))
326 return 0;
327 goto out;
328 }
329
330 evm_status = evm_verify_current_integrity(dentry);
331 if (evm_status == INTEGRITY_NOXATTRS) {
332 struct integrity_iint_cache *iint;
333
334 iint = integrity_iint_find(d_backing_inode(dentry));
335 if (iint && (iint->flags & IMA_NEW_FILE))
336 return 0;
337
338 /* exception for pseudo filesystems */
339 if (dentry->d_sb->s_magic == TMPFS_MAGIC
340 || dentry->d_sb->s_magic == SYSFS_MAGIC)
341 return 0;
342
343 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
344 dentry->d_inode, dentry->d_name.name,
345 "update_metadata",
346 integrity_status_msg[evm_status],
347 -EPERM, 0);
348 }
349out:
350 if (evm_status != INTEGRITY_PASS)
351 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
352 dentry->d_name.name, "appraise_metadata",
353 integrity_status_msg[evm_status],
354 -EPERM, 0);
355 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
356}
357
358/**
359 * evm_inode_setxattr - protect the EVM extended attribute
360 * @dentry: pointer to the affected dentry
361 * @xattr_name: pointer to the affected extended attribute name
362 * @xattr_value: pointer to the new extended attribute value
363 * @xattr_value_len: pointer to the new extended attribute value length
364 *
365 * Before allowing the 'security.evm' protected xattr to be updated,
366 * verify the existing value is valid. As only the kernel should have
367 * access to the EVM encrypted key needed to calculate the HMAC, prevent
368 * userspace from writing HMAC value. Writing 'security.evm' requires
369 * requires CAP_SYS_ADMIN privileges.
370 */
371int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
372 const void *xattr_value, size_t xattr_value_len)
373{
374 const struct evm_ima_xattr_data *xattr_data = xattr_value;
375
376 /* Policy permits modification of the protected xattrs even though
377 * there's no HMAC key loaded
378 */
379 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
380 return 0;
381
382 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
383 if (!xattr_value_len)
384 return -EINVAL;
385 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
386 xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
387 return -EPERM;
388 }
389 return evm_protect_xattr(dentry, xattr_name, xattr_value,
390 xattr_value_len);
391}
392
393/**
394 * evm_inode_removexattr - protect the EVM extended attribute
395 * @dentry: pointer to the affected dentry
396 * @xattr_name: pointer to the affected extended attribute name
397 *
398 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
399 * the current value is valid.
400 */
401int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
402{
403 /* Policy permits modification of the protected xattrs even though
404 * there's no HMAC key loaded
405 */
406 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
407 return 0;
408
409 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
410}
411
412static void evm_reset_status(struct inode *inode)
413{
414 struct integrity_iint_cache *iint;
415
416 iint = integrity_iint_find(inode);
417 if (iint)
418 iint->evm_status = INTEGRITY_UNKNOWN;
419}
420
421/**
422 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
423 * @dentry: pointer to the affected dentry
424 * @xattr_name: pointer to the affected extended attribute name
425 * @xattr_value: pointer to the new extended attribute value
426 * @xattr_value_len: pointer to the new extended attribute value length
427 *
428 * Update the HMAC stored in 'security.evm' to reflect the change.
429 *
430 * No need to take the i_mutex lock here, as this function is called from
431 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
432 * i_mutex lock.
433 */
434void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
435 const void *xattr_value, size_t xattr_value_len)
436{
437 if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name)
438 && !posix_xattr_acl(xattr_name)))
439 return;
440
441 evm_reset_status(dentry->d_inode);
442
443 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
444}
445
446/**
447 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
448 * @dentry: pointer to the affected dentry
449 * @xattr_name: pointer to the affected extended attribute name
450 *
451 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
452 *
453 * No need to take the i_mutex lock here, as this function is called from
454 * vfs_removexattr() which takes the i_mutex.
455 */
456void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
457{
458 if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
459 return;
460
461 evm_reset_status(dentry->d_inode);
462
463 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
464}
465
466/**
467 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
468 * @dentry: pointer to the affected dentry
469 *
470 * Permit update of file attributes when files have a valid EVM signature,
471 * except in the case of them having an immutable portable signature.
472 */
473int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
474{
475 unsigned int ia_valid = attr->ia_valid;
476 enum integrity_status evm_status;
477
478 /* Policy permits modification of the protected attrs even though
479 * there's no HMAC key loaded
480 */
481 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
482 return 0;
483
484 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
485 return 0;
486 evm_status = evm_verify_current_integrity(dentry);
487 if ((evm_status == INTEGRITY_PASS) ||
488 (evm_status == INTEGRITY_NOXATTRS))
489 return 0;
490 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
491 dentry->d_name.name, "appraise_metadata",
492 integrity_status_msg[evm_status], -EPERM, 0);
493 return -EPERM;
494}
495
496/**
497 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
498 * @dentry: pointer to the affected dentry
499 * @ia_valid: for the UID and GID status
500 *
501 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
502 * changes.
503 *
504 * This function is called from notify_change(), which expects the caller
505 * to lock the inode's i_mutex.
506 */
507void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
508{
509 if (!evm_key_loaded())
510 return;
511
512 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
513 evm_update_evmxattr(dentry, NULL, NULL, 0);
514}
515
516/*
517 * evm_inode_init_security - initializes security.evm
518 */
519int evm_inode_init_security(struct inode *inode,
520 const struct xattr *lsm_xattr,
521 struct xattr *evm_xattr)
522{
523 struct evm_xattr *xattr_data;
524 int rc;
525
526 if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name))
527 return 0;
528
529 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
530 if (!xattr_data)
531 return -ENOMEM;
532
533 xattr_data->data.type = EVM_XATTR_HMAC;
534 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
535 if (rc < 0)
536 goto out;
537
538 evm_xattr->value = xattr_data;
539 evm_xattr->value_len = sizeof(*xattr_data);
540 evm_xattr->name = XATTR_EVM_SUFFIX;
541 return 0;
542out:
543 kfree(xattr_data);
544 return rc;
545}
546EXPORT_SYMBOL_GPL(evm_inode_init_security);
547
548#ifdef CONFIG_EVM_LOAD_X509
549void __init evm_load_x509(void)
550{
551 int rc;
552
553 rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
554 if (!rc)
555 evm_initialized |= EVM_INIT_X509;
556}
557#endif
558
559static int __init init_evm(void)
560{
561 int error;
562 struct list_head *pos, *q;
563
564 evm_init_config();
565
566 error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
567 if (error)
568 goto error;
569
570 error = evm_init_secfs();
571 if (error < 0) {
572 pr_info("Error registering secfs\n");
573 goto error;
574 }
575
576error:
577 if (error != 0) {
578 if (!list_empty(&evm_config_xattrnames)) {
579 list_for_each_safe(pos, q, &evm_config_xattrnames)
580 list_del(pos);
581 }
582 }
583
584 return error;
585}
586
587late_initcall(init_evm);
1/*
2 * Copyright (C) 2005-2010 IBM Corporation
3 *
4 * Author:
5 * Mimi Zohar <zohar@us.ibm.com>
6 * Kylene Hall <kjhall@us.ibm.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation, version 2 of the License.
11 *
12 * File: evm_main.c
13 * implements evm_inode_setxattr, evm_inode_post_setxattr,
14 * evm_inode_removexattr, and evm_verifyxattr
15 */
16
17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18
19#include <linux/module.h>
20#include <linux/crypto.h>
21#include <linux/audit.h>
22#include <linux/xattr.h>
23#include <linux/integrity.h>
24#include <linux/evm.h>
25#include <crypto/hash.h>
26#include <crypto/algapi.h>
27#include "evm.h"
28
29int evm_initialized;
30
31static char *integrity_status_msg[] = {
32 "pass", "fail", "no_label", "no_xattrs", "unknown"
33};
34char *evm_hmac = "hmac(sha1)";
35char *evm_hash = "sha1";
36int evm_hmac_attrs;
37
38char *evm_config_xattrnames[] = {
39#ifdef CONFIG_SECURITY_SELINUX
40 XATTR_NAME_SELINUX,
41#endif
42#ifdef CONFIG_SECURITY_SMACK
43 XATTR_NAME_SMACK,
44#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
45 XATTR_NAME_SMACKEXEC,
46 XATTR_NAME_SMACKTRANSMUTE,
47 XATTR_NAME_SMACKMMAP,
48#endif
49#endif
50#ifdef CONFIG_IMA_APPRAISE
51 XATTR_NAME_IMA,
52#endif
53 XATTR_NAME_CAPS,
54 NULL
55};
56
57static int evm_fixmode;
58static int __init evm_set_fixmode(char *str)
59{
60 if (strncmp(str, "fix", 3) == 0)
61 evm_fixmode = 1;
62 return 0;
63}
64__setup("evm=", evm_set_fixmode);
65
66static void __init evm_init_config(void)
67{
68#ifdef CONFIG_EVM_ATTR_FSUUID
69 evm_hmac_attrs |= EVM_ATTR_FSUUID;
70#endif
71 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
72}
73
74static int evm_find_protected_xattrs(struct dentry *dentry)
75{
76 struct inode *inode = d_backing_inode(dentry);
77 char **xattr;
78 int error;
79 int count = 0;
80
81 if (!inode->i_op->getxattr)
82 return -EOPNOTSUPP;
83
84 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
85 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
86 if (error < 0) {
87 if (error == -ENODATA)
88 continue;
89 return error;
90 }
91 count++;
92 }
93
94 return count;
95}
96
97/*
98 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
99 *
100 * Compute the HMAC on the dentry's protected set of extended attributes
101 * and compare it against the stored security.evm xattr.
102 *
103 * For performance:
104 * - use the previoulsy retrieved xattr value and length to calculate the
105 * HMAC.)
106 * - cache the verification result in the iint, when available.
107 *
108 * Returns integrity status
109 */
110static enum integrity_status evm_verify_hmac(struct dentry *dentry,
111 const char *xattr_name,
112 char *xattr_value,
113 size_t xattr_value_len,
114 struct integrity_iint_cache *iint)
115{
116 struct evm_ima_xattr_data *xattr_data = NULL;
117 struct evm_ima_xattr_data calc;
118 enum integrity_status evm_status = INTEGRITY_PASS;
119 int rc, xattr_len;
120
121 if (iint && iint->evm_status == INTEGRITY_PASS)
122 return iint->evm_status;
123
124 /* if status is not PASS, try to check again - against -ENOMEM */
125
126 /* first need to know the sig type */
127 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
128 GFP_NOFS);
129 if (rc <= 0) {
130 evm_status = INTEGRITY_FAIL;
131 if (rc == -ENODATA) {
132 rc = evm_find_protected_xattrs(dentry);
133 if (rc > 0)
134 evm_status = INTEGRITY_NOLABEL;
135 else if (rc == 0)
136 evm_status = INTEGRITY_NOXATTRS; /* new file */
137 } else if (rc == -EOPNOTSUPP) {
138 evm_status = INTEGRITY_UNKNOWN;
139 }
140 goto out;
141 }
142
143 xattr_len = rc;
144
145 /* check value type */
146 switch (xattr_data->type) {
147 case EVM_XATTR_HMAC:
148 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
149 xattr_value_len, calc.digest);
150 if (rc)
151 break;
152 rc = crypto_memneq(xattr_data->digest, calc.digest,
153 sizeof(calc.digest));
154 if (rc)
155 rc = -EINVAL;
156 break;
157 case EVM_IMA_XATTR_DIGSIG:
158 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
159 xattr_value_len, calc.digest);
160 if (rc)
161 break;
162 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
163 (const char *)xattr_data, xattr_len,
164 calc.digest, sizeof(calc.digest));
165 if (!rc) {
166 /* Replace RSA with HMAC if not mounted readonly and
167 * not immutable
168 */
169 if (!IS_RDONLY(d_backing_inode(dentry)) &&
170 !IS_IMMUTABLE(d_backing_inode(dentry)))
171 evm_update_evmxattr(dentry, xattr_name,
172 xattr_value,
173 xattr_value_len);
174 }
175 break;
176 default:
177 rc = -EINVAL;
178 break;
179 }
180
181 if (rc)
182 evm_status = (rc == -ENODATA) ?
183 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
184out:
185 if (iint)
186 iint->evm_status = evm_status;
187 kfree(xattr_data);
188 return evm_status;
189}
190
191static int evm_protected_xattr(const char *req_xattr_name)
192{
193 char **xattrname;
194 int namelen;
195 int found = 0;
196
197 namelen = strlen(req_xattr_name);
198 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
199 if ((strlen(*xattrname) == namelen)
200 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
201 found = 1;
202 break;
203 }
204 if (strncmp(req_xattr_name,
205 *xattrname + XATTR_SECURITY_PREFIX_LEN,
206 strlen(req_xattr_name)) == 0) {
207 found = 1;
208 break;
209 }
210 }
211 return found;
212}
213
214/**
215 * evm_verifyxattr - verify the integrity of the requested xattr
216 * @dentry: object of the verify xattr
217 * @xattr_name: requested xattr
218 * @xattr_value: requested xattr value
219 * @xattr_value_len: requested xattr value length
220 *
221 * Calculate the HMAC for the given dentry and verify it against the stored
222 * security.evm xattr. For performance, use the xattr value and length
223 * previously retrieved to calculate the HMAC.
224 *
225 * Returns the xattr integrity status.
226 *
227 * This function requires the caller to lock the inode's i_mutex before it
228 * is executed.
229 */
230enum integrity_status evm_verifyxattr(struct dentry *dentry,
231 const char *xattr_name,
232 void *xattr_value, size_t xattr_value_len,
233 struct integrity_iint_cache *iint)
234{
235 if (!evm_initialized || !evm_protected_xattr(xattr_name))
236 return INTEGRITY_UNKNOWN;
237
238 if (!iint) {
239 iint = integrity_iint_find(d_backing_inode(dentry));
240 if (!iint)
241 return INTEGRITY_UNKNOWN;
242 }
243 return evm_verify_hmac(dentry, xattr_name, xattr_value,
244 xattr_value_len, iint);
245}
246EXPORT_SYMBOL_GPL(evm_verifyxattr);
247
248/*
249 * evm_verify_current_integrity - verify the dentry's metadata integrity
250 * @dentry: pointer to the affected dentry
251 *
252 * Verify and return the dentry's metadata integrity. The exceptions are
253 * before EVM is initialized or in 'fix' mode.
254 */
255static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
256{
257 struct inode *inode = d_backing_inode(dentry);
258
259 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
260 return 0;
261 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
262}
263
264/*
265 * evm_protect_xattr - protect the EVM extended attribute
266 *
267 * Prevent security.evm from being modified or removed without the
268 * necessary permissions or when the existing value is invalid.
269 *
270 * The posix xattr acls are 'system' prefixed, which normally would not
271 * affect security.evm. An interesting side affect of writing posix xattr
272 * acls is their modifying of the i_mode, which is included in security.evm.
273 * For posix xattr acls only, permit security.evm, even if it currently
274 * doesn't exist, to be updated.
275 */
276static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
277 const void *xattr_value, size_t xattr_value_len)
278{
279 enum integrity_status evm_status;
280
281 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
282 if (!capable(CAP_SYS_ADMIN))
283 return -EPERM;
284 } else if (!evm_protected_xattr(xattr_name)) {
285 if (!posix_xattr_acl(xattr_name))
286 return 0;
287 evm_status = evm_verify_current_integrity(dentry);
288 if ((evm_status == INTEGRITY_PASS) ||
289 (evm_status == INTEGRITY_NOXATTRS))
290 return 0;
291 goto out;
292 }
293 evm_status = evm_verify_current_integrity(dentry);
294 if (evm_status == INTEGRITY_NOXATTRS) {
295 struct integrity_iint_cache *iint;
296
297 iint = integrity_iint_find(d_backing_inode(dentry));
298 if (iint && (iint->flags & IMA_NEW_FILE))
299 return 0;
300
301 /* exception for pseudo filesystems */
302 if (dentry->d_inode->i_sb->s_magic == TMPFS_MAGIC
303 || dentry->d_inode->i_sb->s_magic == SYSFS_MAGIC)
304 return 0;
305
306 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
307 dentry->d_inode, dentry->d_name.name,
308 "update_metadata",
309 integrity_status_msg[evm_status],
310 -EPERM, 0);
311 }
312out:
313 if (evm_status != INTEGRITY_PASS)
314 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
315 dentry->d_name.name, "appraise_metadata",
316 integrity_status_msg[evm_status],
317 -EPERM, 0);
318 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
319}
320
321/**
322 * evm_inode_setxattr - protect the EVM extended attribute
323 * @dentry: pointer to the affected dentry
324 * @xattr_name: pointer to the affected extended attribute name
325 * @xattr_value: pointer to the new extended attribute value
326 * @xattr_value_len: pointer to the new extended attribute value length
327 *
328 * Before allowing the 'security.evm' protected xattr to be updated,
329 * verify the existing value is valid. As only the kernel should have
330 * access to the EVM encrypted key needed to calculate the HMAC, prevent
331 * userspace from writing HMAC value. Writing 'security.evm' requires
332 * requires CAP_SYS_ADMIN privileges.
333 */
334int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
335 const void *xattr_value, size_t xattr_value_len)
336{
337 const struct evm_ima_xattr_data *xattr_data = xattr_value;
338
339 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
340 if (!xattr_value_len)
341 return -EINVAL;
342 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
343 return -EPERM;
344 }
345 return evm_protect_xattr(dentry, xattr_name, xattr_value,
346 xattr_value_len);
347}
348
349/**
350 * evm_inode_removexattr - protect the EVM extended attribute
351 * @dentry: pointer to the affected dentry
352 * @xattr_name: pointer to the affected extended attribute name
353 *
354 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
355 * the current value is valid.
356 */
357int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
358{
359 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
360}
361
362static void evm_reset_status(struct inode *inode)
363{
364 struct integrity_iint_cache *iint;
365
366 iint = integrity_iint_find(inode);
367 if (iint)
368 iint->evm_status = INTEGRITY_UNKNOWN;
369}
370
371/**
372 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
373 * @dentry: pointer to the affected dentry
374 * @xattr_name: pointer to the affected extended attribute name
375 * @xattr_value: pointer to the new extended attribute value
376 * @xattr_value_len: pointer to the new extended attribute value length
377 *
378 * Update the HMAC stored in 'security.evm' to reflect the change.
379 *
380 * No need to take the i_mutex lock here, as this function is called from
381 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
382 * i_mutex lock.
383 */
384void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
385 const void *xattr_value, size_t xattr_value_len)
386{
387 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
388 && !posix_xattr_acl(xattr_name)))
389 return;
390
391 evm_reset_status(dentry->d_inode);
392
393 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
394}
395
396/**
397 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
398 * @dentry: pointer to the affected dentry
399 * @xattr_name: pointer to the affected extended attribute name
400 *
401 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
402 *
403 * No need to take the i_mutex lock here, as this function is called from
404 * vfs_removexattr() which takes the i_mutex.
405 */
406void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
407{
408 if (!evm_initialized || !evm_protected_xattr(xattr_name))
409 return;
410
411 evm_reset_status(dentry->d_inode);
412
413 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
414}
415
416/**
417 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
418 * @dentry: pointer to the affected dentry
419 */
420int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
421{
422 unsigned int ia_valid = attr->ia_valid;
423 enum integrity_status evm_status;
424
425 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
426 return 0;
427 evm_status = evm_verify_current_integrity(dentry);
428 if ((evm_status == INTEGRITY_PASS) ||
429 (evm_status == INTEGRITY_NOXATTRS))
430 return 0;
431 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
432 dentry->d_name.name, "appraise_metadata",
433 integrity_status_msg[evm_status], -EPERM, 0);
434 return -EPERM;
435}
436
437/**
438 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
439 * @dentry: pointer to the affected dentry
440 * @ia_valid: for the UID and GID status
441 *
442 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
443 * changes.
444 *
445 * This function is called from notify_change(), which expects the caller
446 * to lock the inode's i_mutex.
447 */
448void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
449{
450 if (!evm_initialized)
451 return;
452
453 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
454 evm_update_evmxattr(dentry, NULL, NULL, 0);
455}
456
457/*
458 * evm_inode_init_security - initializes security.evm
459 */
460int evm_inode_init_security(struct inode *inode,
461 const struct xattr *lsm_xattr,
462 struct xattr *evm_xattr)
463{
464 struct evm_ima_xattr_data *xattr_data;
465 int rc;
466
467 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
468 return 0;
469
470 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
471 if (!xattr_data)
472 return -ENOMEM;
473
474 xattr_data->type = EVM_XATTR_HMAC;
475 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
476 if (rc < 0)
477 goto out;
478
479 evm_xattr->value = xattr_data;
480 evm_xattr->value_len = sizeof(*xattr_data);
481 evm_xattr->name = XATTR_EVM_SUFFIX;
482 return 0;
483out:
484 kfree(xattr_data);
485 return rc;
486}
487EXPORT_SYMBOL_GPL(evm_inode_init_security);
488
489#ifdef CONFIG_EVM_LOAD_X509
490void __init evm_load_x509(void)
491{
492 int rc;
493
494 rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
495 if (!rc)
496 evm_initialized |= EVM_INIT_X509;
497}
498#endif
499
500static int __init init_evm(void)
501{
502 int error;
503
504 evm_init_config();
505
506 error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
507 if (error)
508 return error;
509
510 error = evm_init_secfs();
511 if (error < 0) {
512 pr_info("Error registering secfs\n");
513 return error;
514 }
515
516 return 0;
517}
518
519/*
520 * evm_display_config - list the EVM protected security extended attributes
521 */
522static int __init evm_display_config(void)
523{
524 char **xattrname;
525
526 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
527 pr_info("%s\n", *xattrname);
528 return 0;
529}
530
531pure_initcall(evm_display_config);
532late_initcall(init_evm);
533
534MODULE_DESCRIPTION("Extended Verification Module");
535MODULE_LICENSE("GPL");