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", "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_SECURITY_APPARMOR
55 #ifdef CONFIG_IMA_APPRAISE
62 static int evm_fixmode;
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)
73 #ifdef CONFIG_EVM_ATTR_FSUUID
74 evm_hmac_attrs |= EVM_ATTR_FSUUID;
76 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
79 static int evm_find_protected_xattrs(struct dentry *dentry)
81 struct inode *inode = d_backing_inode(dentry);
86 if (!(inode->i_opflags & IOP_XATTR))
89 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
90 error = __vfs_getxattr(dentry, inode, *xattr, NULL, 0);
92 if (error == -ENODATA)
103 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
105 * Compute the HMAC on the dentry's protected set of extended attributes
106 * and compare it against the stored security.evm xattr.
109 * - use the previoulsy retrieved xattr value and length to calculate the
111 * - cache the verification result in the iint, when available.
113 * Returns integrity status
115 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
116 const char *xattr_name,
118 size_t xattr_value_len,
119 struct integrity_iint_cache *iint)
121 struct evm_ima_xattr_data *xattr_data = NULL;
122 struct evm_ima_xattr_data calc;
123 enum integrity_status evm_status = INTEGRITY_PASS;
126 if (iint && iint->evm_status == INTEGRITY_PASS)
127 return iint->evm_status;
129 /* if status is not PASS, try to check again - against -ENOMEM */
131 /* first need to know the sig type */
132 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
135 evm_status = INTEGRITY_FAIL;
136 if (rc == -ENODATA) {
137 rc = evm_find_protected_xattrs(dentry);
139 evm_status = INTEGRITY_NOLABEL;
141 evm_status = INTEGRITY_NOXATTRS; /* new file */
142 } else if (rc == -EOPNOTSUPP) {
143 evm_status = INTEGRITY_UNKNOWN;
150 /* check value type */
151 switch (xattr_data->type) {
153 if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
154 evm_status = INTEGRITY_FAIL;
157 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
158 xattr_value_len, calc.digest);
161 rc = crypto_memneq(xattr_data->digest, calc.digest,
162 sizeof(calc.digest));
166 case EVM_IMA_XATTR_DIGSIG:
167 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
168 xattr_value_len, calc.digest);
171 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
172 (const char *)xattr_data, xattr_len,
173 calc.digest, sizeof(calc.digest));
175 /* Replace RSA with HMAC if not mounted readonly and
178 if (!IS_RDONLY(d_backing_inode(dentry)) &&
179 !IS_IMMUTABLE(d_backing_inode(dentry)))
180 evm_update_evmxattr(dentry, xattr_name,
191 evm_status = (rc == -ENODATA) ?
192 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
195 iint->evm_status = evm_status;
200 static int evm_protected_xattr(const char *req_xattr_name)
206 namelen = strlen(req_xattr_name);
207 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
208 if ((strlen(*xattrname) == namelen)
209 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
213 if (strncmp(req_xattr_name,
214 *xattrname + XATTR_SECURITY_PREFIX_LEN,
215 strlen(req_xattr_name)) == 0) {
224 * evm_verifyxattr - verify the integrity of the requested xattr
225 * @dentry: object of the verify xattr
226 * @xattr_name: requested xattr
227 * @xattr_value: requested xattr value
228 * @xattr_value_len: requested xattr value length
230 * Calculate the HMAC for the given dentry and verify it against the stored
231 * security.evm xattr. For performance, use the xattr value and length
232 * previously retrieved to calculate the HMAC.
234 * Returns the xattr integrity status.
236 * This function requires the caller to lock the inode's i_mutex before it
239 enum integrity_status evm_verifyxattr(struct dentry *dentry,
240 const char *xattr_name,
241 void *xattr_value, size_t xattr_value_len,
242 struct integrity_iint_cache *iint)
244 if (!evm_initialized || !evm_protected_xattr(xattr_name))
245 return INTEGRITY_UNKNOWN;
248 iint = integrity_iint_find(d_backing_inode(dentry));
250 return INTEGRITY_UNKNOWN;
252 return evm_verify_hmac(dentry, xattr_name, xattr_value,
253 xattr_value_len, iint);
255 EXPORT_SYMBOL_GPL(evm_verifyxattr);
258 * evm_verify_current_integrity - verify the dentry's metadata integrity
259 * @dentry: pointer to the affected dentry
261 * Verify and return the dentry's metadata integrity. The exceptions are
262 * before EVM is initialized or in 'fix' mode.
264 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
266 struct inode *inode = d_backing_inode(dentry);
268 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
270 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
274 * evm_protect_xattr - protect the EVM extended attribute
276 * Prevent security.evm from being modified or removed without the
277 * necessary permissions or when the existing value is invalid.
279 * The posix xattr acls are 'system' prefixed, which normally would not
280 * affect security.evm. An interesting side affect of writing posix xattr
281 * acls is their modifying of the i_mode, which is included in security.evm.
282 * For posix xattr acls only, permit security.evm, even if it currently
283 * doesn't exist, to be updated.
285 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
286 const void *xattr_value, size_t xattr_value_len)
288 enum integrity_status evm_status;
290 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
291 if (!capable(CAP_SYS_ADMIN))
293 } else if (!evm_protected_xattr(xattr_name)) {
294 if (!posix_xattr_acl(xattr_name))
296 evm_status = evm_verify_current_integrity(dentry);
297 if ((evm_status == INTEGRITY_PASS) ||
298 (evm_status == INTEGRITY_NOXATTRS))
302 evm_status = evm_verify_current_integrity(dentry);
303 if (evm_status == INTEGRITY_NOXATTRS) {
304 struct integrity_iint_cache *iint;
306 iint = integrity_iint_find(d_backing_inode(dentry));
307 if (iint && (iint->flags & IMA_NEW_FILE))
310 /* exception for pseudo filesystems */
311 if (dentry->d_sb->s_magic == TMPFS_MAGIC
312 || dentry->d_sb->s_magic == SYSFS_MAGIC)
315 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
316 dentry->d_inode, dentry->d_name.name,
318 integrity_status_msg[evm_status],
322 if (evm_status != INTEGRITY_PASS)
323 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
324 dentry->d_name.name, "appraise_metadata",
325 integrity_status_msg[evm_status],
327 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
331 * evm_inode_setxattr - protect the EVM extended attribute
332 * @dentry: pointer to the affected dentry
333 * @xattr_name: pointer to the affected extended attribute name
334 * @xattr_value: pointer to the new extended attribute value
335 * @xattr_value_len: pointer to the new extended attribute value length
337 * Before allowing the 'security.evm' protected xattr to be updated,
338 * verify the existing value is valid. As only the kernel should have
339 * access to the EVM encrypted key needed to calculate the HMAC, prevent
340 * userspace from writing HMAC value. Writing 'security.evm' requires
341 * requires CAP_SYS_ADMIN privileges.
343 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
344 const void *xattr_value, size_t xattr_value_len)
346 const struct evm_ima_xattr_data *xattr_data = xattr_value;
348 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
349 if (!xattr_value_len)
351 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
354 return evm_protect_xattr(dentry, xattr_name, xattr_value,
359 * evm_inode_removexattr - protect the EVM extended attribute
360 * @dentry: pointer to the affected dentry
361 * @xattr_name: pointer to the affected extended attribute name
363 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
364 * the current value is valid.
366 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
368 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
371 static void evm_reset_status(struct inode *inode)
373 struct integrity_iint_cache *iint;
375 iint = integrity_iint_find(inode);
377 iint->evm_status = INTEGRITY_UNKNOWN;
381 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
382 * @dentry: pointer to the affected dentry
383 * @xattr_name: pointer to the affected extended attribute name
384 * @xattr_value: pointer to the new extended attribute value
385 * @xattr_value_len: pointer to the new extended attribute value length
387 * Update the HMAC stored in 'security.evm' to reflect the change.
389 * No need to take the i_mutex lock here, as this function is called from
390 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
393 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
394 const void *xattr_value, size_t xattr_value_len)
396 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
397 && !posix_xattr_acl(xattr_name)))
400 evm_reset_status(dentry->d_inode);
402 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
406 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
407 * @dentry: pointer to the affected dentry
408 * @xattr_name: pointer to the affected extended attribute name
410 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
412 * No need to take the i_mutex lock here, as this function is called from
413 * vfs_removexattr() which takes the i_mutex.
415 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
417 if (!evm_initialized || !evm_protected_xattr(xattr_name))
420 evm_reset_status(dentry->d_inode);
422 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
426 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
427 * @dentry: pointer to the affected dentry
429 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
431 unsigned int ia_valid = attr->ia_valid;
432 enum integrity_status evm_status;
434 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
436 evm_status = evm_verify_current_integrity(dentry);
437 if ((evm_status == INTEGRITY_PASS) ||
438 (evm_status == INTEGRITY_NOXATTRS))
440 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
441 dentry->d_name.name, "appraise_metadata",
442 integrity_status_msg[evm_status], -EPERM, 0);
447 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
448 * @dentry: pointer to the affected dentry
449 * @ia_valid: for the UID and GID status
451 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
454 * This function is called from notify_change(), which expects the caller
455 * to lock the inode's i_mutex.
457 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
459 if (!evm_initialized)
462 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
463 evm_update_evmxattr(dentry, NULL, NULL, 0);
467 * evm_inode_init_security - initializes security.evm
469 int evm_inode_init_security(struct inode *inode,
470 const struct xattr *lsm_xattr,
471 struct xattr *evm_xattr)
473 struct evm_ima_xattr_data *xattr_data;
476 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
479 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
483 xattr_data->type = EVM_XATTR_HMAC;
484 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
488 evm_xattr->value = xattr_data;
489 evm_xattr->value_len = sizeof(*xattr_data);
490 evm_xattr->name = XATTR_EVM_SUFFIX;
496 EXPORT_SYMBOL_GPL(evm_inode_init_security);
498 #ifdef CONFIG_EVM_LOAD_X509
499 void __init evm_load_x509(void)
503 rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH);
505 evm_initialized |= EVM_INIT_X509;
509 static int __init init_evm(void)
515 error = integrity_init_keyring(INTEGRITY_KEYRING_EVM);
519 error = evm_init_secfs();
521 pr_info("Error registering secfs\n");
529 * evm_display_config - list the EVM protected security extended attributes
531 static int __init evm_display_config(void)
535 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
536 pr_info("%s\n", *xattrname);
540 pure_initcall(evm_display_config);
541 late_initcall(init_evm);
543 MODULE_DESCRIPTION("Extended Verification Module");
544 MODULE_LICENSE("GPL");