2 * Copyright (C) 2005-2010 IBM Corporation
5 * Mimi Zohar <zohar@us.ibm.com>
6 * Kylene Hall <kjhall@us.ibm.com>
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.
13 * implements evm_inode_setxattr, evm_inode_post_setxattr,
14 * evm_inode_removexattr, and evm_verifyxattr
17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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 <linux/magic.h>
27 #include <crypto/hash.h>
28 #include <crypto/hash_info.h>
29 #include <crypto/algapi.h>
34 static const char * const integrity_status_msg[] = {
35 "pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown"
39 static struct xattr_list evm_config_default_xattrnames[] = {
40 #ifdef CONFIG_SECURITY_SELINUX
41 {.name = XATTR_NAME_SELINUX},
43 #ifdef CONFIG_SECURITY_SMACK
44 {.name = XATTR_NAME_SMACK},
45 #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
46 {.name = XATTR_NAME_SMACKEXEC},
47 {.name = XATTR_NAME_SMACKTRANSMUTE},
48 {.name = XATTR_NAME_SMACKMMAP},
51 #ifdef CONFIG_SECURITY_APPARMOR
52 {.name = XATTR_NAME_APPARMOR},
54 #ifdef CONFIG_IMA_APPRAISE
55 {.name = XATTR_NAME_IMA},
57 {.name = XATTR_NAME_CAPS},
60 LIST_HEAD(evm_config_xattrnames);
62 static int evm_fixmode __ro_after_init;
63 static int __init evm_set_fixmode(char *str)
65 if (strncmp(str, "fix", 3) == 0)
69 __setup("evm=", evm_set_fixmode);
71 static void __init evm_init_config(void)
75 xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
77 pr_info("Initialising EVM extended attributes:\n");
78 for (i = 0; i < xattrs; i++) {
79 pr_info("%s\n", evm_config_default_xattrnames[i].name);
80 list_add_tail(&evm_config_default_xattrnames[i].list,
81 &evm_config_xattrnames);
84 #ifdef CONFIG_EVM_ATTR_FSUUID
85 evm_hmac_attrs |= EVM_ATTR_FSUUID;
87 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
90 static bool evm_key_loaded(void)
92 return (bool)(evm_initialized & EVM_KEY_MASK);
95 static int evm_find_protected_xattrs(struct dentry *dentry)
97 struct inode *inode = d_backing_inode(dentry);
98 struct xattr_list *xattr;
102 if (!(inode->i_opflags & IOP_XATTR))
105 list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
106 error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
108 if (error == -ENODATA)
119 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
121 * Compute the HMAC on the dentry's protected set of extended attributes
122 * and compare it against the stored security.evm xattr.
125 * - use the previoulsy retrieved xattr value and length to calculate the
127 * - cache the verification result in the iint, when available.
129 * Returns integrity status
131 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
132 const char *xattr_name,
134 size_t xattr_value_len,
135 struct integrity_iint_cache *iint)
137 struct evm_ima_xattr_data *xattr_data = NULL;
138 struct signature_v2_hdr *hdr;
139 enum integrity_status evm_status = INTEGRITY_PASS;
140 struct evm_digest digest;
144 if (iint && (iint->evm_status == INTEGRITY_PASS ||
145 iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
146 return iint->evm_status;
148 /* if status is not PASS, try to check again - against -ENOMEM */
150 /* first need to know the sig type */
151 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
154 evm_status = INTEGRITY_FAIL;
155 if (rc == -ENODATA) {
156 rc = evm_find_protected_xattrs(dentry);
158 evm_status = INTEGRITY_NOLABEL;
160 evm_status = INTEGRITY_NOXATTRS; /* new file */
161 } else if (rc == -EOPNOTSUPP) {
162 evm_status = INTEGRITY_UNKNOWN;
169 /* check value type */
170 switch (xattr_data->type) {
172 if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
173 evm_status = INTEGRITY_FAIL;
177 digest.hdr.algo = HASH_ALGO_SHA1;
178 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
179 xattr_value_len, &digest);
182 rc = crypto_memneq(xattr_data->digest, digest.digest,
187 case EVM_IMA_XATTR_DIGSIG:
188 case EVM_XATTR_PORTABLE_DIGSIG:
189 /* accept xattr with non-empty signature field */
190 if (xattr_len <= sizeof(struct signature_v2_hdr)) {
191 evm_status = INTEGRITY_FAIL;
195 hdr = (struct signature_v2_hdr *)xattr_data;
196 digest.hdr.algo = hdr->hash_algo;
197 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
198 xattr_value_len, xattr_data->type, &digest);
201 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
202 (const char *)xattr_data, xattr_len,
203 digest.digest, digest.hdr.length);
205 inode = d_backing_inode(dentry);
207 if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
209 iint->flags |= EVM_IMMUTABLE_DIGSIG;
210 evm_status = INTEGRITY_PASS_IMMUTABLE;
211 } else if (!IS_RDONLY(inode) &&
212 !(inode->i_sb->s_readonly_remount) &&
213 !IS_IMMUTABLE(inode)) {
214 evm_update_evmxattr(dentry, xattr_name,
226 evm_status = (rc == -ENODATA) ?
227 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
230 iint->evm_status = evm_status;
235 static int evm_protected_xattr(const char *req_xattr_name)
239 struct xattr_list *xattr;
241 namelen = strlen(req_xattr_name);
242 list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
243 if ((strlen(xattr->name) == namelen)
244 && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
248 if (strncmp(req_xattr_name,
249 xattr->name + XATTR_SECURITY_PREFIX_LEN,
250 strlen(req_xattr_name)) == 0) {
260 * evm_verifyxattr - verify the integrity of the requested xattr
261 * @dentry: object of the verify xattr
262 * @xattr_name: requested xattr
263 * @xattr_value: requested xattr value
264 * @xattr_value_len: requested xattr value length
266 * Calculate the HMAC for the given dentry and verify it against the stored
267 * security.evm xattr. For performance, use the xattr value and length
268 * previously retrieved to calculate the HMAC.
270 * Returns the xattr integrity status.
272 * This function requires the caller to lock the inode's i_mutex before it
275 enum integrity_status evm_verifyxattr(struct dentry *dentry,
276 const char *xattr_name,
277 void *xattr_value, size_t xattr_value_len,
278 struct integrity_iint_cache *iint)
280 if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
281 return INTEGRITY_UNKNOWN;
284 iint = integrity_iint_find(d_backing_inode(dentry));
286 return INTEGRITY_UNKNOWN;
288 return evm_verify_hmac(dentry, xattr_name, xattr_value,
289 xattr_value_len, iint);
291 EXPORT_SYMBOL_GPL(evm_verifyxattr);
294 * evm_verify_current_integrity - verify the dentry's metadata integrity
295 * @dentry: pointer to the affected dentry
297 * Verify and return the dentry's metadata integrity. The exceptions are
298 * before EVM is initialized or in 'fix' mode.
300 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
302 struct inode *inode = d_backing_inode(dentry);
304 if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
306 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
310 * evm_protect_xattr - protect the EVM extended attribute
312 * Prevent security.evm from being modified or removed without the
313 * necessary permissions or when the existing value is invalid.
315 * The posix xattr acls are 'system' prefixed, which normally would not
316 * affect security.evm. An interesting side affect of writing posix xattr
317 * acls is their modifying of the i_mode, which is included in security.evm.
318 * For posix xattr acls only, permit security.evm, even if it currently
319 * doesn't exist, to be updated unless the EVM signature is immutable.
321 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
322 const void *xattr_value, size_t xattr_value_len)
324 enum integrity_status evm_status;
326 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
327 if (!capable(CAP_SYS_ADMIN))
329 } else if (!evm_protected_xattr(xattr_name)) {
330 if (!posix_xattr_acl(xattr_name))
332 evm_status = evm_verify_current_integrity(dentry);
333 if ((evm_status == INTEGRITY_PASS) ||
334 (evm_status == INTEGRITY_NOXATTRS))
339 evm_status = evm_verify_current_integrity(dentry);
340 if (evm_status == INTEGRITY_NOXATTRS) {
341 struct integrity_iint_cache *iint;
343 iint = integrity_iint_find(d_backing_inode(dentry));
344 if (iint && (iint->flags & IMA_NEW_FILE))
347 /* exception for pseudo filesystems */
348 if (dentry->d_sb->s_magic == TMPFS_MAGIC
349 || dentry->d_sb->s_magic == SYSFS_MAGIC)
352 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
353 dentry->d_inode, dentry->d_name.name,
355 integrity_status_msg[evm_status],
359 if (evm_status != INTEGRITY_PASS)
360 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
361 dentry->d_name.name, "appraise_metadata",
362 integrity_status_msg[evm_status],
364 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
368 * evm_inode_setxattr - protect the EVM extended attribute
369 * @dentry: pointer to the affected dentry
370 * @xattr_name: pointer to the affected extended attribute name
371 * @xattr_value: pointer to the new extended attribute value
372 * @xattr_value_len: pointer to the new extended attribute value length
374 * Before allowing the 'security.evm' protected xattr to be updated,
375 * verify the existing value is valid. As only the kernel should have
376 * access to the EVM encrypted key needed to calculate the HMAC, prevent
377 * userspace from writing HMAC value. Writing 'security.evm' requires
378 * requires CAP_SYS_ADMIN privileges.
380 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
381 const void *xattr_value, size_t xattr_value_len)
383 const struct evm_ima_xattr_data *xattr_data = xattr_value;
385 /* Policy permits modification of the protected xattrs even though
386 * there's no HMAC key loaded
388 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
391 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
392 if (!xattr_value_len)
394 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
395 xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
398 return evm_protect_xattr(dentry, xattr_name, xattr_value,
403 * evm_inode_removexattr - protect the EVM extended attribute
404 * @dentry: pointer to the affected dentry
405 * @xattr_name: pointer to the affected extended attribute name
407 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
408 * the current value is valid.
410 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
412 /* Policy permits modification of the protected xattrs even though
413 * there's no HMAC key loaded
415 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
418 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
421 static void evm_reset_status(struct inode *inode)
423 struct integrity_iint_cache *iint;
425 iint = integrity_iint_find(inode);
427 iint->evm_status = INTEGRITY_UNKNOWN;
431 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
432 * @dentry: pointer to the affected dentry
433 * @xattr_name: pointer to the affected extended attribute name
434 * @xattr_value: pointer to the new extended attribute value
435 * @xattr_value_len: pointer to the new extended attribute value length
437 * Update the HMAC stored in 'security.evm' to reflect the change.
439 * No need to take the i_mutex lock here, as this function is called from
440 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
443 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
444 const void *xattr_value, size_t xattr_value_len)
446 if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name)
447 && !posix_xattr_acl(xattr_name)))
450 evm_reset_status(dentry->d_inode);
452 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
456 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
457 * @dentry: pointer to the affected dentry
458 * @xattr_name: pointer to the affected extended attribute name
460 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
462 * No need to take the i_mutex lock here, as this function is called from
463 * vfs_removexattr() which takes the i_mutex.
465 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
467 if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
470 evm_reset_status(dentry->d_inode);
472 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
476 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
477 * @dentry: pointer to the affected dentry
479 * Permit update of file attributes when files have a valid EVM signature,
480 * except in the case of them having an immutable portable signature.
482 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
484 unsigned int ia_valid = attr->ia_valid;
485 enum integrity_status evm_status;
487 /* Policy permits modification of the protected attrs even though
488 * there's no HMAC key loaded
490 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
493 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
495 evm_status = evm_verify_current_integrity(dentry);
496 if ((evm_status == INTEGRITY_PASS) ||
497 (evm_status == INTEGRITY_NOXATTRS))
499 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
500 dentry->d_name.name, "appraise_metadata",
501 integrity_status_msg[evm_status], -EPERM, 0);
506 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
507 * @dentry: pointer to the affected dentry
508 * @ia_valid: for the UID and GID status
510 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
513 * This function is called from notify_change(), which expects the caller
514 * to lock the inode's i_mutex.
516 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
518 if (!evm_key_loaded())
521 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
522 evm_update_evmxattr(dentry, NULL, NULL, 0);
526 * evm_inode_init_security - initializes security.evm HMAC value
528 int evm_inode_init_security(struct inode *inode,
529 const struct xattr *lsm_xattr,
530 struct xattr *evm_xattr)
532 struct evm_ima_xattr_data *xattr_data;
535 if (!(evm_initialized & EVM_INIT_HMAC) ||
536 !evm_protected_xattr(lsm_xattr->name))
539 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
543 xattr_data->type = EVM_XATTR_HMAC;
544 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
548 evm_xattr->value = xattr_data;
549 evm_xattr->value_len = sizeof(*xattr_data);
550 evm_xattr->name = XATTR_EVM_SUFFIX;
556 EXPORT_SYMBOL_GPL(evm_inode_init_security);
558 #ifdef CONFIG_EVM_LOAD_X509
559 void __init evm_load_x509(void)
563 rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
565 evm_initialized |= EVM_INIT_X509;
569 static int __init init_evm(void)
572 struct list_head *pos, *q;
573 struct xattr_list *xattr;
577 error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
581 error = evm_init_secfs();
583 pr_info("Error registering secfs\n");
589 if (!list_empty(&evm_config_xattrnames)) {
590 list_for_each_safe(pos, q, &evm_config_xattrnames) {
591 xattr = list_entry(pos, struct xattr_list,
601 late_initcall(init_evm);
603 MODULE_DESCRIPTION("Extended Verification Module");
604 MODULE_LICENSE("GPL");