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/audit.h>
20 #include <linux/xattr.h>
21 #include <linux/integrity.h>
22 #include <linux/evm.h>
23 #include <crypto/hash.h>
28 static char *integrity_status_msg[] = {
29 "pass", "fail", "no_label", "no_xattrs", "unknown"
31 char *evm_hmac = "hmac(sha1)";
32 char *evm_hash = "sha1";
33 int evm_hmac_version = CONFIG_EVM_HMAC_VERSION;
35 char *evm_config_xattrnames[] = {
36 #ifdef CONFIG_SECURITY_SELINUX
39 #ifdef CONFIG_SECURITY_SMACK
42 #ifdef CONFIG_IMA_APPRAISE
49 static int evm_fixmode;
50 static int __init evm_set_fixmode(char *str)
52 if (strncmp(str, "fix", 3) == 0)
56 __setup("evm=", evm_set_fixmode);
58 static int evm_find_protected_xattrs(struct dentry *dentry)
60 struct inode *inode = dentry->d_inode;
65 if (!inode->i_op || !inode->i_op->getxattr)
68 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
69 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
71 if (error == -ENODATA)
82 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
84 * Compute the HMAC on the dentry's protected set of extended attributes
85 * and compare it against the stored security.evm xattr.
88 * - use the previoulsy retrieved xattr value and length to calculate the
90 * - cache the verification result in the iint, when available.
92 * Returns integrity status
94 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
95 const char *xattr_name,
97 size_t xattr_value_len,
98 struct integrity_iint_cache *iint)
100 struct evm_ima_xattr_data *xattr_data = NULL;
101 struct evm_ima_xattr_data calc;
102 enum integrity_status evm_status = INTEGRITY_PASS;
105 if (iint && iint->evm_status == INTEGRITY_PASS)
106 return iint->evm_status;
108 /* if status is not PASS, try to check again - against -ENOMEM */
110 /* first need to know the sig type */
111 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
115 evm_status = INTEGRITY_FAIL; /* empty */
116 else if (rc == -ENODATA) {
117 rc = evm_find_protected_xattrs(dentry);
119 evm_status = INTEGRITY_NOLABEL;
121 evm_status = INTEGRITY_NOXATTRS; /* new file */
128 /* check value type */
129 switch (xattr_data->type) {
131 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
132 xattr_value_len, calc.digest);
135 rc = memcmp(xattr_data->digest, calc.digest,
136 sizeof(calc.digest));
140 case EVM_IMA_XATTR_DIGSIG:
141 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
142 xattr_value_len, calc.digest);
145 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
146 (const char *)xattr_data, xattr_len,
147 calc.digest, sizeof(calc.digest));
149 /* we probably want to replace rsa with hmac here */
150 evm_update_evmxattr(dentry, xattr_name, xattr_value,
160 evm_status = (rc == -ENODATA) ?
161 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
164 iint->evm_status = evm_status;
169 static int evm_protected_xattr(const char *req_xattr_name)
175 namelen = strlen(req_xattr_name);
176 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
177 if ((strlen(*xattrname) == namelen)
178 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
182 if (strncmp(req_xattr_name,
183 *xattrname + XATTR_SECURITY_PREFIX_LEN,
184 strlen(req_xattr_name)) == 0) {
193 * evm_verifyxattr - verify the integrity of the requested xattr
194 * @dentry: object of the verify xattr
195 * @xattr_name: requested xattr
196 * @xattr_value: requested xattr value
197 * @xattr_value_len: requested xattr value length
199 * Calculate the HMAC for the given dentry and verify it against the stored
200 * security.evm xattr. For performance, use the xattr value and length
201 * previously retrieved to calculate the HMAC.
203 * Returns the xattr integrity status.
205 * This function requires the caller to lock the inode's i_mutex before it
208 enum integrity_status evm_verifyxattr(struct dentry *dentry,
209 const char *xattr_name,
210 void *xattr_value, size_t xattr_value_len,
211 struct integrity_iint_cache *iint)
213 if (!evm_initialized || !evm_protected_xattr(xattr_name))
214 return INTEGRITY_UNKNOWN;
217 iint = integrity_iint_find(dentry->d_inode);
219 return INTEGRITY_UNKNOWN;
221 return evm_verify_hmac(dentry, xattr_name, xattr_value,
222 xattr_value_len, iint);
224 EXPORT_SYMBOL_GPL(evm_verifyxattr);
227 * evm_verify_current_integrity - verify the dentry's metadata integrity
228 * @dentry: pointer to the affected dentry
230 * Verify and return the dentry's metadata integrity. The exceptions are
231 * before EVM is initialized or in 'fix' mode.
233 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
235 struct inode *inode = dentry->d_inode;
237 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
239 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
243 * evm_protect_xattr - protect the EVM extended attribute
245 * Prevent security.evm from being modified or removed without the
246 * necessary permissions or when the existing value is invalid.
248 * The posix xattr acls are 'system' prefixed, which normally would not
249 * affect security.evm. An interesting side affect of writing posix xattr
250 * acls is their modifying of the i_mode, which is included in security.evm.
251 * For posix xattr acls only, permit security.evm, even if it currently
252 * doesn't exist, to be updated.
254 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
255 const void *xattr_value, size_t xattr_value_len)
257 enum integrity_status evm_status;
259 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
260 if (!capable(CAP_SYS_ADMIN))
262 } else if (!evm_protected_xattr(xattr_name)) {
263 if (!posix_xattr_acl(xattr_name))
265 evm_status = evm_verify_current_integrity(dentry);
266 if ((evm_status == INTEGRITY_PASS) ||
267 (evm_status == INTEGRITY_NOXATTRS))
271 evm_status = evm_verify_current_integrity(dentry);
272 if (evm_status == INTEGRITY_NOXATTRS) {
273 struct integrity_iint_cache *iint;
275 iint = integrity_iint_find(dentry->d_inode);
276 if (iint && (iint->flags & IMA_NEW_FILE))
280 if (evm_status != INTEGRITY_PASS)
281 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
282 dentry->d_name.name, "appraise_metadata",
283 integrity_status_msg[evm_status],
285 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
289 * evm_inode_setxattr - protect the EVM extended attribute
290 * @dentry: pointer to the affected dentry
291 * @xattr_name: pointer to the affected extended attribute name
292 * @xattr_value: pointer to the new extended attribute value
293 * @xattr_value_len: pointer to the new extended attribute value length
295 * Before allowing the 'security.evm' protected xattr to be updated,
296 * verify the existing value is valid. As only the kernel should have
297 * access to the EVM encrypted key needed to calculate the HMAC, prevent
298 * userspace from writing HMAC value. Writing 'security.evm' requires
299 * requires CAP_SYS_ADMIN privileges.
301 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
302 const void *xattr_value, size_t xattr_value_len)
304 const struct evm_ima_xattr_data *xattr_data = xattr_value;
306 if ((strcmp(xattr_name, XATTR_NAME_EVM) == 0)
307 && (xattr_data->type == EVM_XATTR_HMAC))
309 return evm_protect_xattr(dentry, xattr_name, xattr_value,
314 * evm_inode_removexattr - protect the EVM extended attribute
315 * @dentry: pointer to the affected dentry
316 * @xattr_name: pointer to the affected extended attribute name
318 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
319 * the current value is valid.
321 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
323 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
327 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
328 * @dentry: pointer to the affected dentry
329 * @xattr_name: pointer to the affected extended attribute name
330 * @xattr_value: pointer to the new extended attribute value
331 * @xattr_value_len: pointer to the new extended attribute value length
333 * Update the HMAC stored in 'security.evm' to reflect the change.
335 * No need to take the i_mutex lock here, as this function is called from
336 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
339 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
340 const void *xattr_value, size_t xattr_value_len)
342 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
343 && !posix_xattr_acl(xattr_name)))
346 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
351 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
352 * @dentry: pointer to the affected dentry
353 * @xattr_name: pointer to the affected extended attribute name
355 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
357 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
359 struct inode *inode = dentry->d_inode;
361 if (!evm_initialized || !evm_protected_xattr(xattr_name))
364 mutex_lock(&inode->i_mutex);
365 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
366 mutex_unlock(&inode->i_mutex);
371 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
372 * @dentry: pointer to the affected dentry
374 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
376 unsigned int ia_valid = attr->ia_valid;
377 enum integrity_status evm_status;
379 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
381 evm_status = evm_verify_current_integrity(dentry);
382 if ((evm_status == INTEGRITY_PASS) ||
383 (evm_status == INTEGRITY_NOXATTRS))
385 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
386 dentry->d_name.name, "appraise_metadata",
387 integrity_status_msg[evm_status], -EPERM, 0);
392 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
393 * @dentry: pointer to the affected dentry
394 * @ia_valid: for the UID and GID status
396 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
399 * This function is called from notify_change(), which expects the caller
400 * to lock the inode's i_mutex.
402 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
404 if (!evm_initialized)
407 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
408 evm_update_evmxattr(dentry, NULL, NULL, 0);
413 * evm_inode_init_security - initializes security.evm
415 int evm_inode_init_security(struct inode *inode,
416 const struct xattr *lsm_xattr,
417 struct xattr *evm_xattr)
419 struct evm_ima_xattr_data *xattr_data;
422 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
425 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
429 xattr_data->type = EVM_XATTR_HMAC;
430 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
434 evm_xattr->value = xattr_data;
435 evm_xattr->value_len = sizeof(*xattr_data);
436 evm_xattr->name = XATTR_EVM_SUFFIX;
442 EXPORT_SYMBOL_GPL(evm_inode_init_security);
444 static int __init init_evm(void)
448 error = evm_init_secfs();
450 printk(KERN_INFO "EVM: Error registering secfs\n");
460 * evm_display_config - list the EVM protected security extended attributes
462 static int __init evm_display_config(void)
466 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
467 printk(KERN_INFO "EVM: %s\n", *xattrname);
471 pure_initcall(evm_display_config);
472 late_initcall(init_evm);
474 MODULE_DESCRIPTION("Extended Verification Module");
475 MODULE_LICENSE("GPL");