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";
29 int evm_hmac_version = CONFIG_EVM_HMAC_VERSION;
31 char *evm_config_xattrnames[] = {
32 #ifdef CONFIG_SECURITY_SELINUX
35 #ifdef CONFIG_SECURITY_SMACK
38 #ifdef CONFIG_IMA_APPRAISE
45 static int evm_fixmode;
46 static int __init evm_set_fixmode(char *str)
48 if (strncmp(str, "fix", 3) == 0)
52 __setup("evm=", evm_set_fixmode);
54 static int evm_find_protected_xattrs(struct dentry *dentry)
56 struct inode *inode = dentry->d_inode;
61 if (!inode->i_op || !inode->i_op->getxattr)
64 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
65 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
67 if (error == -ENODATA)
78 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
80 * Compute the HMAC on the dentry's protected set of extended attributes
81 * and compare it against the stored security.evm xattr.
84 * - use the previoulsy retrieved xattr value and length to calculate the
86 * - cache the verification result in the iint, when available.
88 * Returns integrity status
90 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
91 const char *xattr_name,
93 size_t xattr_value_len,
94 struct integrity_iint_cache *iint)
96 struct evm_ima_xattr_data *xattr_data = NULL;
97 struct evm_ima_xattr_data calc;
98 enum integrity_status evm_status = INTEGRITY_PASS;
101 if (iint && iint->evm_status == INTEGRITY_PASS)
102 return iint->evm_status;
104 /* if status is not PASS, try to check again - against -ENOMEM */
106 /* first need to know the sig type */
107 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
111 evm_status = INTEGRITY_FAIL; /* empty */
112 else if (rc == -ENODATA) {
113 rc = evm_find_protected_xattrs(dentry);
115 evm_status = INTEGRITY_NOLABEL;
117 evm_status = INTEGRITY_NOXATTRS; /* new file */
124 /* check value type */
125 switch (xattr_data->type) {
127 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
128 xattr_value_len, calc.digest);
131 rc = memcmp(xattr_data->digest, calc.digest,
132 sizeof(calc.digest));
136 case EVM_IMA_XATTR_DIGSIG:
137 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
138 xattr_value_len, calc.digest);
141 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
142 xattr_data->digest, xattr_len,
143 calc.digest, sizeof(calc.digest));
145 /* we probably want to replace rsa with hmac here */
146 evm_update_evmxattr(dentry, xattr_name, xattr_value,
156 evm_status = (rc == -ENODATA) ?
157 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
160 iint->evm_status = evm_status;
165 static int evm_protected_xattr(const char *req_xattr_name)
171 namelen = strlen(req_xattr_name);
172 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
173 if ((strlen(*xattrname) == namelen)
174 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
178 if (strncmp(req_xattr_name,
179 *xattrname + XATTR_SECURITY_PREFIX_LEN,
180 strlen(req_xattr_name)) == 0) {
189 * evm_verifyxattr - verify the integrity of the requested xattr
190 * @dentry: object of the verify xattr
191 * @xattr_name: requested xattr
192 * @xattr_value: requested xattr value
193 * @xattr_value_len: requested xattr value length
195 * Calculate the HMAC for the given dentry and verify it against the stored
196 * security.evm xattr. For performance, use the xattr value and length
197 * previously retrieved to calculate the HMAC.
199 * Returns the xattr integrity status.
201 * This function requires the caller to lock the inode's i_mutex before it
204 enum integrity_status evm_verifyxattr(struct dentry *dentry,
205 const char *xattr_name,
206 void *xattr_value, size_t xattr_value_len,
207 struct integrity_iint_cache *iint)
209 if (!evm_initialized || !evm_protected_xattr(xattr_name))
210 return INTEGRITY_UNKNOWN;
213 iint = integrity_iint_find(dentry->d_inode);
215 return INTEGRITY_UNKNOWN;
217 return evm_verify_hmac(dentry, xattr_name, xattr_value,
218 xattr_value_len, iint);
220 EXPORT_SYMBOL_GPL(evm_verifyxattr);
223 * evm_verify_current_integrity - verify the dentry's metadata integrity
224 * @dentry: pointer to the affected dentry
226 * Verify and return the dentry's metadata integrity. The exceptions are
227 * before EVM is initialized or in 'fix' mode.
229 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
231 struct inode *inode = dentry->d_inode;
233 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
235 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
239 * evm_protect_xattr - protect the EVM extended attribute
241 * Prevent security.evm from being modified or removed without the
242 * necessary permissions or when the existing value is invalid.
244 * The posix xattr acls are 'system' prefixed, which normally would not
245 * affect security.evm. An interesting side affect of writing posix xattr
246 * acls is their modifying of the i_mode, which is included in security.evm.
247 * For posix xattr acls only, permit security.evm, even if it currently
248 * doesn't exist, to be updated.
250 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
251 const void *xattr_value, size_t xattr_value_len)
253 enum integrity_status evm_status;
255 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
256 if (!capable(CAP_SYS_ADMIN))
258 } else if (!evm_protected_xattr(xattr_name)) {
259 if (!posix_xattr_acl(xattr_name))
261 evm_status = evm_verify_current_integrity(dentry);
262 if ((evm_status == INTEGRITY_PASS) ||
263 (evm_status == INTEGRITY_NOXATTRS))
267 evm_status = evm_verify_current_integrity(dentry);
268 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
272 * evm_inode_setxattr - protect the EVM extended attribute
273 * @dentry: pointer to the affected dentry
274 * @xattr_name: pointer to the affected extended attribute name
275 * @xattr_value: pointer to the new extended attribute value
276 * @xattr_value_len: pointer to the new extended attribute value length
278 * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
279 * the current value is valid.
281 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
282 const void *xattr_value, size_t xattr_value_len)
284 return evm_protect_xattr(dentry, xattr_name, xattr_value,
289 * evm_inode_removexattr - protect the EVM extended attribute
290 * @dentry: pointer to the affected dentry
291 * @xattr_name: pointer to the affected extended attribute name
293 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
294 * the current value is valid.
296 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
298 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
302 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
303 * @dentry: pointer to the affected dentry
304 * @xattr_name: pointer to the affected extended attribute name
305 * @xattr_value: pointer to the new extended attribute value
306 * @xattr_value_len: pointer to the new extended attribute value length
308 * Update the HMAC stored in 'security.evm' to reflect the change.
310 * No need to take the i_mutex lock here, as this function is called from
311 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
314 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
315 const void *xattr_value, size_t xattr_value_len)
317 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
318 && !posix_xattr_acl(xattr_name)))
321 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
326 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
327 * @dentry: pointer to the affected dentry
328 * @xattr_name: pointer to the affected extended attribute name
330 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
332 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
334 struct inode *inode = dentry->d_inode;
336 if (!evm_initialized || !evm_protected_xattr(xattr_name))
339 mutex_lock(&inode->i_mutex);
340 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
341 mutex_unlock(&inode->i_mutex);
346 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
347 * @dentry: pointer to the affected dentry
349 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
351 unsigned int ia_valid = attr->ia_valid;
352 enum integrity_status evm_status;
354 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
356 evm_status = evm_verify_current_integrity(dentry);
357 if ((evm_status == INTEGRITY_PASS) ||
358 (evm_status == INTEGRITY_NOXATTRS))
364 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
365 * @dentry: pointer to the affected dentry
366 * @ia_valid: for the UID and GID status
368 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
371 * This function is called from notify_change(), which expects the caller
372 * to lock the inode's i_mutex.
374 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
376 if (!evm_initialized)
379 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
380 evm_update_evmxattr(dentry, NULL, NULL, 0);
385 * evm_inode_init_security - initializes security.evm
387 int evm_inode_init_security(struct inode *inode,
388 const struct xattr *lsm_xattr,
389 struct xattr *evm_xattr)
391 struct evm_ima_xattr_data *xattr_data;
394 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
397 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
401 xattr_data->type = EVM_XATTR_HMAC;
402 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
406 evm_xattr->value = xattr_data;
407 evm_xattr->value_len = sizeof(*xattr_data);
408 evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS);
414 EXPORT_SYMBOL_GPL(evm_inode_init_security);
416 static int __init init_evm(void)
420 error = evm_init_secfs();
422 printk(KERN_INFO "EVM: Error registering secfs\n");
432 * evm_display_config - list the EVM protected security extended attributes
434 static int __init evm_display_config(void)
438 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
439 printk(KERN_INFO "EVM: %s\n", *xattrname);
443 pure_initcall(evm_display_config);
444 late_initcall(init_evm);
446 MODULE_DESCRIPTION("Extended Verification Module");
447 MODULE_LICENSE("GPL");