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 <crypto/hash.h>
30 static char *integrity_status_msg[] = {
31 "pass", "fail", "no_label", "no_xattrs", "unknown"
33 char *evm_hmac = "hmac(sha1)";
34 char *evm_hash = "sha1";
35 int evm_hmac_version = CONFIG_EVM_HMAC_VERSION;
37 char *evm_config_xattrnames[] = {
38 #ifdef CONFIG_SECURITY_SELINUX
41 #ifdef CONFIG_SECURITY_SMACK
44 #ifdef CONFIG_IMA_APPRAISE
51 static int evm_fixmode;
52 static int __init evm_set_fixmode(char *str)
54 if (strncmp(str, "fix", 3) == 0)
58 __setup("evm=", evm_set_fixmode);
60 static int evm_find_protected_xattrs(struct dentry *dentry)
62 struct inode *inode = dentry->d_inode;
67 if (!inode->i_op->getxattr)
70 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
71 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
73 if (error == -ENODATA)
84 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
86 * Compute the HMAC on the dentry's protected set of extended attributes
87 * and compare it against the stored security.evm xattr.
90 * - use the previoulsy retrieved xattr value and length to calculate the
92 * - cache the verification result in the iint, when available.
94 * Returns integrity status
96 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
97 const char *xattr_name,
99 size_t xattr_value_len,
100 struct integrity_iint_cache *iint)
102 struct evm_ima_xattr_data *xattr_data = NULL;
103 struct evm_ima_xattr_data calc;
104 enum integrity_status evm_status = INTEGRITY_PASS;
107 if (iint && iint->evm_status == INTEGRITY_PASS)
108 return iint->evm_status;
110 /* if status is not PASS, try to check again - against -ENOMEM */
112 /* first need to know the sig type */
113 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
117 evm_status = INTEGRITY_FAIL; /* empty */
118 else if (rc == -ENODATA) {
119 rc = evm_find_protected_xattrs(dentry);
121 evm_status = INTEGRITY_NOLABEL;
123 evm_status = INTEGRITY_NOXATTRS; /* new file */
130 /* check value type */
131 switch (xattr_data->type) {
133 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
134 xattr_value_len, calc.digest);
137 rc = memcmp(xattr_data->digest, calc.digest,
138 sizeof(calc.digest));
142 case EVM_IMA_XATTR_DIGSIG:
143 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
144 xattr_value_len, calc.digest);
147 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
148 (const char *)xattr_data, xattr_len,
149 calc.digest, sizeof(calc.digest));
151 /* we probably want to replace rsa with hmac here */
152 evm_update_evmxattr(dentry, xattr_name, xattr_value,
162 evm_status = (rc == -ENODATA) ?
163 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
166 iint->evm_status = evm_status;
171 static int evm_protected_xattr(const char *req_xattr_name)
177 namelen = strlen(req_xattr_name);
178 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
179 if ((strlen(*xattrname) == namelen)
180 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
184 if (strncmp(req_xattr_name,
185 *xattrname + XATTR_SECURITY_PREFIX_LEN,
186 strlen(req_xattr_name)) == 0) {
195 * evm_verifyxattr - verify the integrity of the requested xattr
196 * @dentry: object of the verify xattr
197 * @xattr_name: requested xattr
198 * @xattr_value: requested xattr value
199 * @xattr_value_len: requested xattr value length
201 * Calculate the HMAC for the given dentry and verify it against the stored
202 * security.evm xattr. For performance, use the xattr value and length
203 * previously retrieved to calculate the HMAC.
205 * Returns the xattr integrity status.
207 * This function requires the caller to lock the inode's i_mutex before it
210 enum integrity_status evm_verifyxattr(struct dentry *dentry,
211 const char *xattr_name,
212 void *xattr_value, size_t xattr_value_len,
213 struct integrity_iint_cache *iint)
215 if (!evm_initialized || !evm_protected_xattr(xattr_name))
216 return INTEGRITY_UNKNOWN;
219 iint = integrity_iint_find(dentry->d_inode);
221 return INTEGRITY_UNKNOWN;
223 return evm_verify_hmac(dentry, xattr_name, xattr_value,
224 xattr_value_len, iint);
226 EXPORT_SYMBOL_GPL(evm_verifyxattr);
229 * evm_verify_current_integrity - verify the dentry's metadata integrity
230 * @dentry: pointer to the affected dentry
232 * Verify and return the dentry's metadata integrity. The exceptions are
233 * before EVM is initialized or in 'fix' mode.
235 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
237 struct inode *inode = dentry->d_inode;
239 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
241 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
245 * evm_protect_xattr - protect the EVM extended attribute
247 * Prevent security.evm from being modified or removed without the
248 * necessary permissions or when the existing value is invalid.
250 * The posix xattr acls are 'system' prefixed, which normally would not
251 * affect security.evm. An interesting side affect of writing posix xattr
252 * acls is their modifying of the i_mode, which is included in security.evm.
253 * For posix xattr acls only, permit security.evm, even if it currently
254 * doesn't exist, to be updated.
256 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
257 const void *xattr_value, size_t xattr_value_len)
259 enum integrity_status evm_status;
261 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
262 if (!capable(CAP_SYS_ADMIN))
264 } else if (!evm_protected_xattr(xattr_name)) {
265 if (!posix_xattr_acl(xattr_name))
267 evm_status = evm_verify_current_integrity(dentry);
268 if ((evm_status == INTEGRITY_PASS) ||
269 (evm_status == INTEGRITY_NOXATTRS))
273 evm_status = evm_verify_current_integrity(dentry);
275 if (evm_status != INTEGRITY_PASS)
276 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
277 dentry->d_name.name, "appraise_metadata",
278 integrity_status_msg[evm_status],
280 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
284 * evm_inode_setxattr - protect the EVM extended attribute
285 * @dentry: pointer to the affected dentry
286 * @xattr_name: pointer to the affected extended attribute name
287 * @xattr_value: pointer to the new extended attribute value
288 * @xattr_value_len: pointer to the new extended attribute value length
290 * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
291 * the current value is valid.
293 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
294 const void *xattr_value, size_t xattr_value_len)
296 return evm_protect_xattr(dentry, xattr_name, xattr_value,
301 * evm_inode_removexattr - protect the EVM extended attribute
302 * @dentry: pointer to the affected dentry
303 * @xattr_name: pointer to the affected extended attribute name
305 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
306 * the current value is valid.
308 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
310 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
314 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
315 * @dentry: pointer to the affected dentry
316 * @xattr_name: pointer to the affected extended attribute name
317 * @xattr_value: pointer to the new extended attribute value
318 * @xattr_value_len: pointer to the new extended attribute value length
320 * Update the HMAC stored in 'security.evm' to reflect the change.
322 * No need to take the i_mutex lock here, as this function is called from
323 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
326 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
327 const void *xattr_value, size_t xattr_value_len)
329 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
330 && !posix_xattr_acl(xattr_name)))
333 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
338 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
339 * @dentry: pointer to the affected dentry
340 * @xattr_name: pointer to the affected extended attribute name
342 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
344 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
346 struct inode *inode = dentry->d_inode;
348 if (!evm_initialized || !evm_protected_xattr(xattr_name))
351 mutex_lock(&inode->i_mutex);
352 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
353 mutex_unlock(&inode->i_mutex);
358 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
359 * @dentry: pointer to the affected dentry
361 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
363 unsigned int ia_valid = attr->ia_valid;
364 enum integrity_status evm_status;
366 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
368 evm_status = evm_verify_current_integrity(dentry);
369 if ((evm_status == INTEGRITY_PASS) ||
370 (evm_status == INTEGRITY_NOXATTRS))
372 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
373 dentry->d_name.name, "appraise_metadata",
374 integrity_status_msg[evm_status], -EPERM, 0);
379 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
380 * @dentry: pointer to the affected dentry
381 * @ia_valid: for the UID and GID status
383 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
386 * This function is called from notify_change(), which expects the caller
387 * to lock the inode's i_mutex.
389 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
391 if (!evm_initialized)
394 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
395 evm_update_evmxattr(dentry, NULL, NULL, 0);
400 * evm_inode_init_security - initializes security.evm
402 int evm_inode_init_security(struct inode *inode,
403 const struct xattr *lsm_xattr,
404 struct xattr *evm_xattr)
406 struct evm_ima_xattr_data *xattr_data;
409 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
412 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
416 xattr_data->type = EVM_XATTR_HMAC;
417 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
421 evm_xattr->value = xattr_data;
422 evm_xattr->value_len = sizeof(*xattr_data);
423 evm_xattr->name = XATTR_EVM_SUFFIX;
429 EXPORT_SYMBOL_GPL(evm_inode_init_security);
431 static int __init init_evm(void)
435 error = evm_init_secfs();
437 pr_info("Error registering secfs\n");
447 * evm_display_config - list the EVM protected security extended attributes
449 static int __init evm_display_config(void)
453 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
454 pr_info("%s\n", *xattrname);
458 pure_initcall(evm_display_config);
459 late_initcall(init_evm);
461 MODULE_DESCRIPTION("Extended Verification Module");
462 MODULE_LICENSE("GPL");