1 // SPDX-License-Identifier: GPL-2.0-only
3 * Copyright (C) 2005-2010 IBM Corporation
6 * Mimi Zohar <zohar@us.ibm.com>
7 * Kylene Hall <kjhall@us.ibm.com>
10 * implements evm_inode_setxattr, evm_inode_post_setxattr,
11 * evm_inode_removexattr, and evm_verifyxattr
14 #include <linux/init.h>
15 #include <linux/crypto.h>
16 #include <linux/audit.h>
17 #include <linux/xattr.h>
18 #include <linux/integrity.h>
19 #include <linux/evm.h>
20 #include <linux/magic.h>
22 #include <crypto/hash.h>
23 #include <crypto/hash_info.h>
24 #include <crypto/algapi.h>
29 static const char * const integrity_status_msg[] = {
30 "pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown"
34 static struct xattr_list evm_config_default_xattrnames[] = {
35 #ifdef CONFIG_SECURITY_SELINUX
36 {.name = XATTR_NAME_SELINUX},
38 #ifdef CONFIG_SECURITY_SMACK
39 {.name = XATTR_NAME_SMACK},
40 #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
41 {.name = XATTR_NAME_SMACKEXEC},
42 {.name = XATTR_NAME_SMACKTRANSMUTE},
43 {.name = XATTR_NAME_SMACKMMAP},
46 #ifdef CONFIG_SECURITY_APPARMOR
47 {.name = XATTR_NAME_APPARMOR},
49 #ifdef CONFIG_IMA_APPRAISE
50 {.name = XATTR_NAME_IMA},
52 {.name = XATTR_NAME_CAPS},
55 LIST_HEAD(evm_config_xattrnames);
57 static int evm_fixmode;
58 static int __init evm_set_fixmode(char *str)
60 if (strncmp(str, "fix", 3) == 0)
64 __setup("evm=", evm_set_fixmode);
66 static void __init evm_init_config(void)
70 xattrs = ARRAY_SIZE(evm_config_default_xattrnames);
72 pr_info("Initialising EVM extended attributes:\n");
73 for (i = 0; i < xattrs; i++) {
74 pr_info("%s\n", evm_config_default_xattrnames[i].name);
75 list_add_tail(&evm_config_default_xattrnames[i].list,
76 &evm_config_xattrnames);
79 #ifdef CONFIG_EVM_ATTR_FSUUID
80 evm_hmac_attrs |= EVM_ATTR_FSUUID;
82 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
85 static bool evm_key_loaded(void)
87 return (bool)(evm_initialized & EVM_KEY_MASK);
90 static int evm_find_protected_xattrs(struct dentry *dentry)
92 struct inode *inode = d_backing_inode(dentry);
93 struct xattr_list *xattr;
97 if (!(inode->i_opflags & IOP_XATTR))
100 list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
101 error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0);
103 if (error == -ENODATA)
114 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
116 * Compute the HMAC on the dentry's protected set of extended attributes
117 * and compare it against the stored security.evm xattr.
120 * - use the previoulsy retrieved xattr value and length to calculate the
122 * - cache the verification result in the iint, when available.
124 * Returns integrity status
126 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
127 const char *xattr_name,
129 size_t xattr_value_len,
130 struct integrity_iint_cache *iint)
132 struct evm_ima_xattr_data *xattr_data = NULL;
133 struct signature_v2_hdr *hdr;
134 enum integrity_status evm_status = INTEGRITY_PASS;
135 struct evm_digest digest;
139 if (iint && (iint->evm_status == INTEGRITY_PASS ||
140 iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
141 return iint->evm_status;
143 /* if status is not PASS, try to check again - against -ENOMEM */
145 /* first need to know the sig type */
146 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
149 evm_status = INTEGRITY_FAIL;
150 if (rc == -ENODATA) {
151 rc = evm_find_protected_xattrs(dentry);
153 evm_status = INTEGRITY_NOLABEL;
155 evm_status = INTEGRITY_NOXATTRS; /* new file */
156 } else if (rc == -EOPNOTSUPP) {
157 evm_status = INTEGRITY_UNKNOWN;
164 /* check value type */
165 switch (xattr_data->type) {
167 if (xattr_len != sizeof(struct evm_xattr)) {
168 evm_status = INTEGRITY_FAIL;
172 digest.hdr.algo = HASH_ALGO_SHA1;
173 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
174 xattr_value_len, &digest);
177 rc = crypto_memneq(xattr_data->data, digest.digest,
182 case EVM_IMA_XATTR_DIGSIG:
183 case EVM_XATTR_PORTABLE_DIGSIG:
184 hdr = (struct signature_v2_hdr *)xattr_data;
185 digest.hdr.algo = hdr->hash_algo;
186 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
187 xattr_value_len, xattr_data->type, &digest);
190 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
191 (const char *)xattr_data, xattr_len,
192 digest.digest, digest.hdr.length);
194 inode = d_backing_inode(dentry);
196 if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
198 iint->flags |= EVM_IMMUTABLE_DIGSIG;
199 evm_status = INTEGRITY_PASS_IMMUTABLE;
200 } else if (!IS_RDONLY(inode) &&
201 !(inode->i_sb->s_readonly_remount) &&
202 !IS_IMMUTABLE(inode)) {
203 evm_update_evmxattr(dentry, xattr_name,
215 evm_status = (rc == -ENODATA) ?
216 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
219 iint->evm_status = evm_status;
224 static int evm_protected_xattr(const char *req_xattr_name)
228 struct xattr_list *xattr;
230 namelen = strlen(req_xattr_name);
231 list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) {
232 if ((strlen(xattr->name) == namelen)
233 && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) {
237 if (strncmp(req_xattr_name,
238 xattr->name + XATTR_SECURITY_PREFIX_LEN,
239 strlen(req_xattr_name)) == 0) {
249 * evm_verifyxattr - verify the integrity of the requested xattr
250 * @dentry: object of the verify xattr
251 * @xattr_name: requested xattr
252 * @xattr_value: requested xattr value
253 * @xattr_value_len: requested xattr value length
255 * Calculate the HMAC for the given dentry and verify it against the stored
256 * security.evm xattr. For performance, use the xattr value and length
257 * previously retrieved to calculate the HMAC.
259 * Returns the xattr integrity status.
261 * This function requires the caller to lock the inode's i_mutex before it
264 enum integrity_status evm_verifyxattr(struct dentry *dentry,
265 const char *xattr_name,
266 void *xattr_value, size_t xattr_value_len,
267 struct integrity_iint_cache *iint)
269 if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
270 return INTEGRITY_UNKNOWN;
273 iint = integrity_iint_find(d_backing_inode(dentry));
275 return INTEGRITY_UNKNOWN;
277 return evm_verify_hmac(dentry, xattr_name, xattr_value,
278 xattr_value_len, iint);
280 EXPORT_SYMBOL_GPL(evm_verifyxattr);
283 * evm_verify_current_integrity - verify the dentry's metadata integrity
284 * @dentry: pointer to the affected dentry
286 * Verify and return the dentry's metadata integrity. The exceptions are
287 * before EVM is initialized or in 'fix' mode.
289 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
291 struct inode *inode = d_backing_inode(dentry);
293 if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode)
295 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
299 * evm_protect_xattr - protect the EVM extended attribute
301 * Prevent security.evm from being modified or removed without the
302 * necessary permissions or when the existing value is invalid.
304 * The posix xattr acls are 'system' prefixed, which normally would not
305 * affect security.evm. An interesting side affect of writing posix xattr
306 * acls is their modifying of the i_mode, which is included in security.evm.
307 * For posix xattr acls only, permit security.evm, even if it currently
308 * doesn't exist, to be updated unless the EVM signature is immutable.
310 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
311 const void *xattr_value, size_t xattr_value_len)
313 enum integrity_status evm_status;
315 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
316 if (!capable(CAP_SYS_ADMIN))
318 } else if (!evm_protected_xattr(xattr_name)) {
319 if (!posix_xattr_acl(xattr_name))
321 evm_status = evm_verify_current_integrity(dentry);
322 if ((evm_status == INTEGRITY_PASS) ||
323 (evm_status == INTEGRITY_NOXATTRS))
328 evm_status = evm_verify_current_integrity(dentry);
329 if (evm_status == INTEGRITY_NOXATTRS) {
330 struct integrity_iint_cache *iint;
332 iint = integrity_iint_find(d_backing_inode(dentry));
333 if (iint && (iint->flags & IMA_NEW_FILE))
336 /* exception for pseudo filesystems */
337 if (dentry->d_sb->s_magic == TMPFS_MAGIC
338 || dentry->d_sb->s_magic == SYSFS_MAGIC)
341 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
342 dentry->d_inode, dentry->d_name.name,
344 integrity_status_msg[evm_status],
348 if (evm_status != INTEGRITY_PASS)
349 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
350 dentry->d_name.name, "appraise_metadata",
351 integrity_status_msg[evm_status],
353 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
357 * evm_inode_setxattr - protect the EVM extended attribute
358 * @dentry: pointer to the affected dentry
359 * @xattr_name: pointer to the affected extended attribute name
360 * @xattr_value: pointer to the new extended attribute value
361 * @xattr_value_len: pointer to the new extended attribute value length
363 * Before allowing the 'security.evm' protected xattr to be updated,
364 * verify the existing value is valid. As only the kernel should have
365 * access to the EVM encrypted key needed to calculate the HMAC, prevent
366 * userspace from writing HMAC value. Writing 'security.evm' requires
367 * requires CAP_SYS_ADMIN privileges.
369 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
370 const void *xattr_value, size_t xattr_value_len)
372 const struct evm_ima_xattr_data *xattr_data = xattr_value;
374 /* Policy permits modification of the protected xattrs even though
375 * there's no HMAC key loaded
377 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
380 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
381 if (!xattr_value_len)
383 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
384 xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
387 return evm_protect_xattr(dentry, xattr_name, xattr_value,
392 * evm_inode_removexattr - protect the EVM extended attribute
393 * @dentry: pointer to the affected dentry
394 * @xattr_name: pointer to the affected extended attribute name
396 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
397 * the current value is valid.
399 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
401 /* Policy permits modification of the protected xattrs even though
402 * there's no HMAC key loaded
404 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
407 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
410 static void evm_reset_status(struct inode *inode)
412 struct integrity_iint_cache *iint;
414 iint = integrity_iint_find(inode);
416 iint->evm_status = INTEGRITY_UNKNOWN;
420 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
421 * @dentry: pointer to the affected dentry
422 * @xattr_name: pointer to the affected extended attribute name
423 * @xattr_value: pointer to the new extended attribute value
424 * @xattr_value_len: pointer to the new extended attribute value length
426 * Update the HMAC stored in 'security.evm' to reflect the change.
428 * No need to take the i_mutex lock here, as this function is called from
429 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
432 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
433 const void *xattr_value, size_t xattr_value_len)
435 if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name)
436 && !posix_xattr_acl(xattr_name)))
439 evm_reset_status(dentry->d_inode);
441 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
445 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
446 * @dentry: pointer to the affected dentry
447 * @xattr_name: pointer to the affected extended attribute name
449 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
451 * No need to take the i_mutex lock here, as this function is called from
452 * vfs_removexattr() which takes the i_mutex.
454 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
456 if (!evm_key_loaded() || !evm_protected_xattr(xattr_name))
459 evm_reset_status(dentry->d_inode);
461 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
465 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
466 * @dentry: pointer to the affected dentry
468 * Permit update of file attributes when files have a valid EVM signature,
469 * except in the case of them having an immutable portable signature.
471 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
473 unsigned int ia_valid = attr->ia_valid;
474 enum integrity_status evm_status;
476 /* Policy permits modification of the protected attrs even though
477 * there's no HMAC key loaded
479 if (evm_initialized & EVM_ALLOW_METADATA_WRITES)
482 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
484 evm_status = evm_verify_current_integrity(dentry);
485 if ((evm_status == INTEGRITY_PASS) ||
486 (evm_status == INTEGRITY_NOXATTRS))
488 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
489 dentry->d_name.name, "appraise_metadata",
490 integrity_status_msg[evm_status], -EPERM, 0);
495 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
496 * @dentry: pointer to the affected dentry
497 * @ia_valid: for the UID and GID status
499 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
502 * This function is called from notify_change(), which expects the caller
503 * to lock the inode's i_mutex.
505 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
507 if (!evm_key_loaded())
510 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
511 evm_update_evmxattr(dentry, NULL, NULL, 0);
515 * evm_inode_init_security - initializes security.evm
517 int evm_inode_init_security(struct inode *inode,
518 const struct xattr *lsm_xattr,
519 struct xattr *evm_xattr)
521 struct evm_xattr *xattr_data;
524 if (!evm_key_loaded() || !evm_protected_xattr(lsm_xattr->name))
527 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
531 xattr_data->data.type = EVM_XATTR_HMAC;
532 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
536 evm_xattr->value = xattr_data;
537 evm_xattr->value_len = sizeof(*xattr_data);
538 evm_xattr->name = XATTR_EVM_SUFFIX;
544 EXPORT_SYMBOL_GPL(evm_inode_init_security);
546 #ifdef CONFIG_EVM_LOAD_X509
547 void __init evm_load_x509(void)
551 rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
553 evm_initialized |= EVM_INIT_X509;
557 static int __init init_evm(void)
560 struct list_head *pos, *q;
564 error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
568 error = evm_init_secfs();
570 pr_info("Error registering secfs\n");
576 if (!list_empty(&evm_config_xattrnames)) {
577 list_for_each_safe(pos, q, &evm_config_xattrnames)
585 late_initcall(init_evm);