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/algapi.h>
33 static char *integrity_status_msg[] = {
34 "pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown"
36 char *evm_hmac = "hmac(sha1)";
37 char *evm_hash = "sha1";
40 char *evm_config_xattrnames[] = {
41 #ifdef CONFIG_SECURITY_SELINUX
44 #ifdef CONFIG_SECURITY_SMACK
46 #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
48 XATTR_NAME_SMACKTRANSMUTE,
52 #ifdef CONFIG_IMA_APPRAISE
59 static int evm_fixmode __ro_after_init;
60 static int __init evm_set_fixmode(char *str)
62 if (strncmp(str, "fix", 3) == 0)
66 __setup("evm=", evm_set_fixmode);
68 static void __init evm_init_config(void)
70 #ifdef CONFIG_EVM_ATTR_FSUUID
71 evm_hmac_attrs |= EVM_ATTR_FSUUID;
73 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
76 static int evm_find_protected_xattrs(struct dentry *dentry)
78 struct inode *inode = d_backing_inode(dentry);
83 if (!(inode->i_opflags & IOP_XATTR))
86 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
87 error = __vfs_getxattr(dentry, inode, *xattr, NULL, 0);
89 if (error == -ENODATA)
100 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
102 * Compute the HMAC on the dentry's protected set of extended attributes
103 * and compare it against the stored security.evm xattr.
106 * - use the previoulsy retrieved xattr value and length to calculate the
108 * - cache the verification result in the iint, when available.
110 * Returns integrity status
112 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
113 const char *xattr_name,
115 size_t xattr_value_len,
116 struct integrity_iint_cache *iint)
118 struct evm_ima_xattr_data *xattr_data = NULL;
119 struct evm_ima_xattr_data calc;
120 enum integrity_status evm_status = INTEGRITY_PASS;
123 if (iint && (iint->evm_status == INTEGRITY_PASS ||
124 iint->evm_status == INTEGRITY_PASS_IMMUTABLE))
125 return iint->evm_status;
127 /* if status is not PASS, try to check again - against -ENOMEM */
129 /* first need to know the sig type */
130 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
133 evm_status = INTEGRITY_FAIL;
134 if (rc == -ENODATA) {
135 rc = evm_find_protected_xattrs(dentry);
137 evm_status = INTEGRITY_NOLABEL;
139 evm_status = INTEGRITY_NOXATTRS; /* new file */
140 } else if (rc == -EOPNOTSUPP) {
141 evm_status = INTEGRITY_UNKNOWN;
148 /* check value type */
149 switch (xattr_data->type) {
151 if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
152 evm_status = INTEGRITY_FAIL;
155 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
156 xattr_value_len, calc.digest);
159 rc = crypto_memneq(xattr_data->digest, calc.digest,
160 sizeof(calc.digest));
164 case EVM_IMA_XATTR_DIGSIG:
165 case EVM_XATTR_PORTABLE_DIGSIG:
166 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
167 xattr_value_len, xattr_data->type,
171 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
172 (const char *)xattr_data, xattr_len,
173 calc.digest, sizeof(calc.digest));
175 if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) {
177 iint->flags |= EVM_IMMUTABLE_DIGSIG;
178 evm_status = INTEGRITY_PASS_IMMUTABLE;
179 } else if (!IS_RDONLY(d_backing_inode(dentry)) &&
180 !IS_IMMUTABLE(d_backing_inode(dentry))) {
181 evm_update_evmxattr(dentry, xattr_name,
193 evm_status = (rc == -ENODATA) ?
194 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
197 iint->evm_status = evm_status;
202 static int evm_protected_xattr(const char *req_xattr_name)
208 namelen = strlen(req_xattr_name);
209 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
210 if ((strlen(*xattrname) == namelen)
211 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
215 if (strncmp(req_xattr_name,
216 *xattrname + XATTR_SECURITY_PREFIX_LEN,
217 strlen(req_xattr_name)) == 0) {
226 * evm_verifyxattr - verify the integrity of the requested xattr
227 * @dentry: object of the verify xattr
228 * @xattr_name: requested xattr
229 * @xattr_value: requested xattr value
230 * @xattr_value_len: requested xattr value length
232 * Calculate the HMAC for the given dentry and verify it against the stored
233 * security.evm xattr. For performance, use the xattr value and length
234 * previously retrieved to calculate the HMAC.
236 * Returns the xattr integrity status.
238 * This function requires the caller to lock the inode's i_mutex before it
241 enum integrity_status evm_verifyxattr(struct dentry *dentry,
242 const char *xattr_name,
243 void *xattr_value, size_t xattr_value_len,
244 struct integrity_iint_cache *iint)
246 if (!evm_initialized || !evm_protected_xattr(xattr_name))
247 return INTEGRITY_UNKNOWN;
250 iint = integrity_iint_find(d_backing_inode(dentry));
252 return INTEGRITY_UNKNOWN;
254 return evm_verify_hmac(dentry, xattr_name, xattr_value,
255 xattr_value_len, iint);
257 EXPORT_SYMBOL_GPL(evm_verifyxattr);
260 * evm_verify_current_integrity - verify the dentry's metadata integrity
261 * @dentry: pointer to the affected dentry
263 * Verify and return the dentry's metadata integrity. The exceptions are
264 * before EVM is initialized or in 'fix' mode.
266 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
268 struct inode *inode = d_backing_inode(dentry);
270 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
272 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
276 * evm_protect_xattr - protect the EVM extended attribute
278 * Prevent security.evm from being modified or removed without the
279 * necessary permissions or when the existing value is invalid.
281 * The posix xattr acls are 'system' prefixed, which normally would not
282 * affect security.evm. An interesting side affect of writing posix xattr
283 * acls is their modifying of the i_mode, which is included in security.evm.
284 * For posix xattr acls only, permit security.evm, even if it currently
285 * doesn't exist, to be updated unless the EVM signature is immutable.
287 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
288 const void *xattr_value, size_t xattr_value_len)
290 enum integrity_status evm_status;
292 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
293 if (!capable(CAP_SYS_ADMIN))
295 } else if (!evm_protected_xattr(xattr_name)) {
296 if (!posix_xattr_acl(xattr_name))
298 evm_status = evm_verify_current_integrity(dentry);
299 if ((evm_status == INTEGRITY_PASS) ||
300 (evm_status == INTEGRITY_NOXATTRS))
304 evm_status = evm_verify_current_integrity(dentry);
305 if (evm_status == INTEGRITY_NOXATTRS) {
306 struct integrity_iint_cache *iint;
308 iint = integrity_iint_find(d_backing_inode(dentry));
309 if (iint && (iint->flags & IMA_NEW_FILE))
312 /* exception for pseudo filesystems */
313 if (dentry->d_sb->s_magic == TMPFS_MAGIC
314 || dentry->d_sb->s_magic == SYSFS_MAGIC)
317 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
318 dentry->d_inode, dentry->d_name.name,
320 integrity_status_msg[evm_status],
324 if (evm_status != INTEGRITY_PASS)
325 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
326 dentry->d_name.name, "appraise_metadata",
327 integrity_status_msg[evm_status],
329 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
333 * evm_inode_setxattr - protect the EVM extended attribute
334 * @dentry: pointer to the affected dentry
335 * @xattr_name: pointer to the affected extended attribute name
336 * @xattr_value: pointer to the new extended attribute value
337 * @xattr_value_len: pointer to the new extended attribute value length
339 * Before allowing the 'security.evm' protected xattr to be updated,
340 * verify the existing value is valid. As only the kernel should have
341 * access to the EVM encrypted key needed to calculate the HMAC, prevent
342 * userspace from writing HMAC value. Writing 'security.evm' requires
343 * requires CAP_SYS_ADMIN privileges.
345 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
346 const void *xattr_value, size_t xattr_value_len)
348 const struct evm_ima_xattr_data *xattr_data = xattr_value;
350 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
351 if (!xattr_value_len)
353 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG &&
354 xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG)
357 return evm_protect_xattr(dentry, xattr_name, xattr_value,
362 * evm_inode_removexattr - protect the EVM extended attribute
363 * @dentry: pointer to the affected dentry
364 * @xattr_name: pointer to the affected extended attribute name
366 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
367 * the current value is valid.
369 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
371 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
374 static void evm_reset_status(struct inode *inode)
376 struct integrity_iint_cache *iint;
378 iint = integrity_iint_find(inode);
380 iint->evm_status = INTEGRITY_UNKNOWN;
384 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
385 * @dentry: pointer to the affected dentry
386 * @xattr_name: pointer to the affected extended attribute name
387 * @xattr_value: pointer to the new extended attribute value
388 * @xattr_value_len: pointer to the new extended attribute value length
390 * Update the HMAC stored in 'security.evm' to reflect the change.
392 * No need to take the i_mutex lock here, as this function is called from
393 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
396 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
397 const void *xattr_value, size_t xattr_value_len)
399 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
400 && !posix_xattr_acl(xattr_name)))
403 evm_reset_status(dentry->d_inode);
405 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
409 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
410 * @dentry: pointer to the affected dentry
411 * @xattr_name: pointer to the affected extended attribute name
413 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
415 * No need to take the i_mutex lock here, as this function is called from
416 * vfs_removexattr() which takes the i_mutex.
418 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
420 if (!evm_initialized || !evm_protected_xattr(xattr_name))
423 evm_reset_status(dentry->d_inode);
425 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
429 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
430 * @idmap: idmap of the mount
431 * @dentry: pointer to the affected dentry
432 * @attr: iattr structure containing the new file attributes
434 * Permit update of file attributes when files have a valid EVM signature,
435 * except in the case of them having an immutable portable signature.
437 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
439 unsigned int ia_valid = attr->ia_valid;
440 enum integrity_status evm_status;
442 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
444 evm_status = evm_verify_current_integrity(dentry);
445 if ((evm_status == INTEGRITY_PASS) ||
446 (evm_status == INTEGRITY_NOXATTRS))
448 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
449 dentry->d_name.name, "appraise_metadata",
450 integrity_status_msg[evm_status], -EPERM, 0);
455 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
456 * @dentry: pointer to the affected dentry
457 * @ia_valid: for the UID and GID status
459 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
462 * This function is called from notify_change(), which expects the caller
463 * to lock the inode's i_mutex.
465 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
467 if (!evm_initialized)
470 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
471 evm_update_evmxattr(dentry, NULL, NULL, 0);
475 * evm_inode_init_security - initializes security.evm
477 int evm_inode_init_security(struct inode *inode,
478 const struct xattr *lsm_xattr,
479 struct xattr *evm_xattr)
481 struct evm_ima_xattr_data *xattr_data;
484 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
487 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
491 xattr_data->type = EVM_XATTR_HMAC;
492 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
496 evm_xattr->value = xattr_data;
497 evm_xattr->value_len = sizeof(*xattr_data);
498 evm_xattr->name = XATTR_EVM_SUFFIX;
504 EXPORT_SYMBOL_GPL(evm_inode_init_security);
506 #ifdef CONFIG_EVM_LOAD_X509
507 void __init evm_load_x509(void)
511 rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
513 evm_initialized |= EVM_INIT_X509;
517 static int __init init_evm(void)
523 error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
527 error = evm_init_secfs();
529 pr_info("Error registering secfs\n");
537 * evm_display_config - list the EVM protected security extended attributes
539 static int __init evm_display_config(void)
543 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
544 pr_info("%s\n", *xattrname);
548 pure_initcall(evm_display_config);
549 late_initcall(init_evm);
551 MODULE_DESCRIPTION("Extended Verification Module");
552 MODULE_LICENSE("GPL");