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
41 static int evm_fixmode;
42 static int __init evm_set_fixmode(char *str)
44 if (strncmp(str, "fix", 3) == 0)
48 __setup("evm=", evm_set_fixmode);
50 static int evm_find_protected_xattrs(struct dentry *dentry)
52 struct inode *inode = dentry->d_inode;
57 if (!inode->i_op || !inode->i_op->getxattr)
60 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
61 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
63 if (error == -ENODATA)
74 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
76 * Compute the HMAC on the dentry's protected set of extended attributes
77 * and compare it against the stored security.evm xattr.
80 * - use the previoulsy retrieved xattr value and length to calculate the
82 * - cache the verification result in the iint, when available.
84 * Returns integrity status
86 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
87 const char *xattr_name,
89 size_t xattr_value_len,
90 struct integrity_iint_cache *iint)
92 struct evm_ima_xattr_data *xattr_data = NULL;
93 struct evm_ima_xattr_data calc;
94 enum integrity_status evm_status = INTEGRITY_PASS;
97 if (iint && iint->evm_status == INTEGRITY_PASS)
98 return iint->evm_status;
100 /* if status is not PASS, try to check again - against -ENOMEM */
102 /* first need to know the sig type */
103 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
107 evm_status = INTEGRITY_FAIL; /* empty */
108 else if (rc == -ENODATA) {
109 rc = evm_find_protected_xattrs(dentry);
111 evm_status = INTEGRITY_NOLABEL;
113 evm_status = INTEGRITY_NOXATTRS; /* new file */
120 /* check value type */
121 switch (xattr_data->type) {
123 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
124 xattr_value_len, calc.digest);
127 rc = memcmp(xattr_data->digest, calc.digest,
128 sizeof(calc.digest));
132 case EVM_IMA_XATTR_DIGSIG:
133 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
134 xattr_value_len, calc.digest);
137 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
138 xattr_data->digest, xattr_len,
139 calc.digest, sizeof(calc.digest));
141 /* we probably want to replace rsa with hmac here */
142 evm_update_evmxattr(dentry, xattr_name, xattr_value,
152 evm_status = (rc == -ENODATA) ?
153 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
156 iint->evm_status = evm_status;
161 static int evm_protected_xattr(const char *req_xattr_name)
167 namelen = strlen(req_xattr_name);
168 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
169 if ((strlen(*xattrname) == namelen)
170 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
174 if (strncmp(req_xattr_name,
175 *xattrname + XATTR_SECURITY_PREFIX_LEN,
176 strlen(req_xattr_name)) == 0) {
185 * evm_verifyxattr - verify the integrity of the requested xattr
186 * @dentry: object of the verify xattr
187 * @xattr_name: requested xattr
188 * @xattr_value: requested xattr value
189 * @xattr_value_len: requested xattr value length
191 * Calculate the HMAC for the given dentry and verify it against the stored
192 * security.evm xattr. For performance, use the xattr value and length
193 * previously retrieved to calculate the HMAC.
195 * Returns the xattr integrity status.
197 * This function requires the caller to lock the inode's i_mutex before it
200 enum integrity_status evm_verifyxattr(struct dentry *dentry,
201 const char *xattr_name,
202 void *xattr_value, size_t xattr_value_len,
203 struct integrity_iint_cache *iint)
205 if (!evm_initialized || !evm_protected_xattr(xattr_name))
206 return INTEGRITY_UNKNOWN;
209 iint = integrity_iint_find(dentry->d_inode);
211 return INTEGRITY_UNKNOWN;
213 return evm_verify_hmac(dentry, xattr_name, xattr_value,
214 xattr_value_len, iint);
216 EXPORT_SYMBOL_GPL(evm_verifyxattr);
219 * evm_verify_current_integrity - verify the dentry's metadata integrity
220 * @dentry: pointer to the affected dentry
222 * Verify and return the dentry's metadata integrity. The exceptions are
223 * before EVM is initialized or in 'fix' mode.
225 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
227 struct inode *inode = dentry->d_inode;
229 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
231 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
235 * evm_protect_xattr - protect the EVM extended attribute
237 * Prevent security.evm from being modified or removed without the
238 * necessary permissions or when the existing value is invalid.
240 * The posix xattr acls are 'system' prefixed, which normally would not
241 * affect security.evm. An interesting side affect of writing posix xattr
242 * acls is their modifying of the i_mode, which is included in security.evm.
243 * For posix xattr acls only, permit security.evm, even if it currently
244 * doesn't exist, to be updated.
246 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
247 const void *xattr_value, size_t xattr_value_len)
249 enum integrity_status evm_status;
251 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
252 if (!capable(CAP_SYS_ADMIN))
254 } else if (!evm_protected_xattr(xattr_name)) {
255 if (!posix_xattr_acl(xattr_name))
257 evm_status = evm_verify_current_integrity(dentry);
258 if ((evm_status == INTEGRITY_PASS) ||
259 (evm_status == INTEGRITY_NOXATTRS))
263 evm_status = evm_verify_current_integrity(dentry);
264 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
268 * evm_inode_setxattr - protect the EVM extended attribute
269 * @dentry: pointer to the affected dentry
270 * @xattr_name: pointer to the affected extended attribute name
271 * @xattr_value: pointer to the new extended attribute value
272 * @xattr_value_len: pointer to the new extended attribute value length
274 * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
275 * the current value is valid.
277 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
278 const void *xattr_value, size_t xattr_value_len)
280 return evm_protect_xattr(dentry, xattr_name, xattr_value,
285 * evm_inode_removexattr - protect the EVM extended attribute
286 * @dentry: pointer to the affected dentry
287 * @xattr_name: pointer to the affected extended attribute name
289 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
290 * the current value is valid.
292 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
294 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
298 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
299 * @dentry: pointer to the affected dentry
300 * @xattr_name: pointer to the affected extended attribute name
301 * @xattr_value: pointer to the new extended attribute value
302 * @xattr_value_len: pointer to the new extended attribute value length
304 * Update the HMAC stored in 'security.evm' to reflect the change.
306 * No need to take the i_mutex lock here, as this function is called from
307 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
310 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
311 const void *xattr_value, size_t xattr_value_len)
313 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
314 && !posix_xattr_acl(xattr_name)))
317 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
322 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
323 * @dentry: pointer to the affected dentry
324 * @xattr_name: pointer to the affected extended attribute name
326 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
328 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
330 struct inode *inode = dentry->d_inode;
332 if (!evm_initialized || !evm_protected_xattr(xattr_name))
335 mutex_lock(&inode->i_mutex);
336 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
337 mutex_unlock(&inode->i_mutex);
342 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
343 * @dentry: pointer to the affected dentry
345 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
347 unsigned int ia_valid = attr->ia_valid;
348 enum integrity_status evm_status;
350 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
352 evm_status = evm_verify_current_integrity(dentry);
353 if ((evm_status == INTEGRITY_PASS) ||
354 (evm_status == INTEGRITY_NOXATTRS))
360 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
361 * @dentry: pointer to the affected dentry
362 * @ia_valid: for the UID and GID status
364 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
367 * This function is called from notify_change(), which expects the caller
368 * to lock the inode's i_mutex.
370 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
372 if (!evm_initialized)
375 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
376 evm_update_evmxattr(dentry, NULL, NULL, 0);
381 * evm_inode_init_security - initializes security.evm
383 int evm_inode_init_security(struct inode *inode,
384 const struct xattr *lsm_xattr,
385 struct xattr *evm_xattr)
387 struct evm_ima_xattr_data *xattr_data;
390 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
393 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
397 xattr_data->type = EVM_XATTR_HMAC;
398 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
402 evm_xattr->value = xattr_data;
403 evm_xattr->value_len = sizeof(*xattr_data);
404 evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS);
410 EXPORT_SYMBOL_GPL(evm_inode_init_security);
412 static int __init init_evm(void)
416 error = evm_init_secfs();
418 printk(KERN_INFO "EVM: Error registering secfs\n");
427 static void __exit cleanup_evm(void)
431 crypto_free_shash(hmac_tfm);
433 crypto_free_shash(hash_tfm);
437 * evm_display_config - list the EVM protected security extended attributes
439 static int __init evm_display_config(void)
443 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
444 printk(KERN_INFO "EVM: %s\n", *xattrname);
448 pure_initcall(evm_display_config);
449 late_initcall(init_evm);
451 MODULE_DESCRIPTION("Extended Verification Module");
452 MODULE_LICENSE("GPL");