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 #include <linux/module.h>
18 #include <linux/crypto.h>
19 #include <linux/xattr.h>
20 #include <linux/integrity.h>
21 #include <linux/evm.h>
22 #include <crypto/hash.h>
27 char *evm_hmac = "hmac(sha1)";
28 char *evm_hash = "sha1";
30 char *evm_config_xattrnames[] = {
31 #ifdef CONFIG_SECURITY_SELINUX
34 #ifdef CONFIG_SECURITY_SMACK
37 #ifdef CONFIG_IMA_APPRAISE
44 static int evm_fixmode;
45 static int __init evm_set_fixmode(char *str)
47 if (strncmp(str, "fix", 3) == 0)
51 __setup("evm=", evm_set_fixmode);
53 static int evm_find_protected_xattrs(struct dentry *dentry)
55 struct inode *inode = dentry->d_inode;
60 if (!inode->i_op || !inode->i_op->getxattr)
63 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
64 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
66 if (error == -ENODATA)
77 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
79 * Compute the HMAC on the dentry's protected set of extended attributes
80 * and compare it against the stored security.evm xattr.
83 * - use the previoulsy retrieved xattr value and length to calculate the
85 * - cache the verification result in the iint, when available.
87 * Returns integrity status
89 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
90 const char *xattr_name,
92 size_t xattr_value_len,
93 struct integrity_iint_cache *iint)
95 struct evm_ima_xattr_data *xattr_data = NULL;
96 struct evm_ima_xattr_data calc;
97 enum integrity_status evm_status = INTEGRITY_PASS;
100 if (iint && iint->evm_status == INTEGRITY_PASS)
101 return iint->evm_status;
103 /* if status is not PASS, try to check again - against -ENOMEM */
105 /* first need to know the sig type */
106 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
110 evm_status = INTEGRITY_FAIL; /* empty */
111 else if (rc == -ENODATA) {
112 rc = evm_find_protected_xattrs(dentry);
114 evm_status = INTEGRITY_NOLABEL;
116 evm_status = INTEGRITY_NOXATTRS; /* new file */
123 /* check value type */
124 switch (xattr_data->type) {
126 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
127 xattr_value_len, calc.digest);
130 rc = memcmp(xattr_data->digest, calc.digest,
131 sizeof(calc.digest));
135 case EVM_IMA_XATTR_DIGSIG:
136 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
137 xattr_value_len, calc.digest);
140 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
141 xattr_data->digest, xattr_len,
142 calc.digest, sizeof(calc.digest));
144 /* we probably want to replace rsa with hmac here */
145 evm_update_evmxattr(dentry, xattr_name, xattr_value,
155 evm_status = (rc == -ENODATA) ?
156 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
159 iint->evm_status = evm_status;
164 static int evm_protected_xattr(const char *req_xattr_name)
170 namelen = strlen(req_xattr_name);
171 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
172 if ((strlen(*xattrname) == namelen)
173 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
177 if (strncmp(req_xattr_name,
178 *xattrname + XATTR_SECURITY_PREFIX_LEN,
179 strlen(req_xattr_name)) == 0) {
188 * evm_verifyxattr - verify the integrity of the requested xattr
189 * @dentry: object of the verify xattr
190 * @xattr_name: requested xattr
191 * @xattr_value: requested xattr value
192 * @xattr_value_len: requested xattr value length
194 * Calculate the HMAC for the given dentry and verify it against the stored
195 * security.evm xattr. For performance, use the xattr value and length
196 * previously retrieved to calculate the HMAC.
198 * Returns the xattr integrity status.
200 * This function requires the caller to lock the inode's i_mutex before it
203 enum integrity_status evm_verifyxattr(struct dentry *dentry,
204 const char *xattr_name,
205 void *xattr_value, size_t xattr_value_len,
206 struct integrity_iint_cache *iint)
208 if (!evm_initialized || !evm_protected_xattr(xattr_name))
209 return INTEGRITY_UNKNOWN;
212 iint = integrity_iint_find(dentry->d_inode);
214 return INTEGRITY_UNKNOWN;
216 return evm_verify_hmac(dentry, xattr_name, xattr_value,
217 xattr_value_len, iint);
219 EXPORT_SYMBOL_GPL(evm_verifyxattr);
222 * evm_verify_current_integrity - verify the dentry's metadata integrity
223 * @dentry: pointer to the affected dentry
225 * Verify and return the dentry's metadata integrity. The exceptions are
226 * before EVM is initialized or in 'fix' mode.
228 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
230 struct inode *inode = dentry->d_inode;
232 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
234 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
238 * evm_protect_xattr - protect the EVM extended attribute
240 * Prevent security.evm from being modified or removed without the
241 * necessary permissions or when the existing value is invalid.
243 * The posix xattr acls are 'system' prefixed, which normally would not
244 * affect security.evm. An interesting side affect of writing posix xattr
245 * acls is their modifying of the i_mode, which is included in security.evm.
246 * For posix xattr acls only, permit security.evm, even if it currently
247 * doesn't exist, to be updated.
249 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
250 const void *xattr_value, size_t xattr_value_len)
252 enum integrity_status evm_status;
254 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
255 if (!capable(CAP_SYS_ADMIN))
257 } else if (!evm_protected_xattr(xattr_name)) {
258 if (!posix_xattr_acl(xattr_name))
260 evm_status = evm_verify_current_integrity(dentry);
261 if ((evm_status == INTEGRITY_PASS) ||
262 (evm_status == INTEGRITY_NOXATTRS))
266 evm_status = evm_verify_current_integrity(dentry);
267 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
271 * evm_inode_setxattr - protect the EVM extended attribute
272 * @dentry: pointer to the affected dentry
273 * @xattr_name: pointer to the affected extended attribute name
274 * @xattr_value: pointer to the new extended attribute value
275 * @xattr_value_len: pointer to the new extended attribute value length
277 * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
278 * the current value is valid.
280 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
281 const void *xattr_value, size_t xattr_value_len)
283 return evm_protect_xattr(dentry, xattr_name, xattr_value,
288 * evm_inode_removexattr - protect the EVM extended attribute
289 * @dentry: pointer to the affected dentry
290 * @xattr_name: pointer to the affected extended attribute name
292 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
293 * the current value is valid.
295 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
297 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
301 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
302 * @dentry: pointer to the affected dentry
303 * @xattr_name: pointer to the affected extended attribute name
304 * @xattr_value: pointer to the new extended attribute value
305 * @xattr_value_len: pointer to the new extended attribute value length
307 * Update the HMAC stored in 'security.evm' to reflect the change.
309 * No need to take the i_mutex lock here, as this function is called from
310 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
313 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
314 const void *xattr_value, size_t xattr_value_len)
316 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
317 && !posix_xattr_acl(xattr_name)))
320 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
325 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
326 * @dentry: pointer to the affected dentry
327 * @xattr_name: pointer to the affected extended attribute name
329 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
331 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
333 struct inode *inode = dentry->d_inode;
335 if (!evm_initialized || !evm_protected_xattr(xattr_name))
338 mutex_lock(&inode->i_mutex);
339 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
340 mutex_unlock(&inode->i_mutex);
345 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
346 * @dentry: pointer to the affected dentry
348 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
350 unsigned int ia_valid = attr->ia_valid;
351 enum integrity_status evm_status;
353 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
355 evm_status = evm_verify_current_integrity(dentry);
356 if ((evm_status == INTEGRITY_PASS) ||
357 (evm_status == INTEGRITY_NOXATTRS))
363 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
364 * @dentry: pointer to the affected dentry
365 * @ia_valid: for the UID and GID status
367 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
370 * This function is called from notify_change(), which expects the caller
371 * to lock the inode's i_mutex.
373 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
375 if (!evm_initialized)
378 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
379 evm_update_evmxattr(dentry, NULL, NULL, 0);
384 * evm_inode_init_security - initializes security.evm
386 int evm_inode_init_security(struct inode *inode,
387 const struct xattr *lsm_xattr,
388 struct xattr *evm_xattr)
390 struct evm_ima_xattr_data *xattr_data;
393 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
396 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
400 xattr_data->type = EVM_XATTR_HMAC;
401 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
405 evm_xattr->value = xattr_data;
406 evm_xattr->value_len = sizeof(*xattr_data);
407 evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS);
413 EXPORT_SYMBOL_GPL(evm_inode_init_security);
415 static int __init init_evm(void)
419 error = evm_init_secfs();
421 printk(KERN_INFO "EVM: Error registering secfs\n");
430 static void __exit cleanup_evm(void)
434 crypto_free_shash(hmac_tfm);
436 crypto_free_shash(hash_tfm);
440 * evm_display_config - list the EVM protected security extended attributes
442 static int __init evm_display_config(void)
446 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
447 printk(KERN_INFO "EVM: %s\n", *xattrname);
451 pure_initcall(evm_display_config);
452 late_initcall(init_evm);
454 MODULE_DESCRIPTION("Extended Verification Module");
455 MODULE_LICENSE("GPL");