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";
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 void __init evm_init_config(void)
62 #ifdef CONFIG_EVM_ATTR_FSUUID
63 evm_hmac_attrs |= EVM_ATTR_FSUUID;
65 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
68 static int evm_find_protected_xattrs(struct dentry *dentry)
70 struct inode *inode = dentry->d_inode;
75 if (!inode->i_op->getxattr)
78 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
79 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
81 if (error == -ENODATA)
92 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
94 * Compute the HMAC on the dentry's protected set of extended attributes
95 * and compare it against the stored security.evm xattr.
98 * - use the previoulsy retrieved xattr value and length to calculate the
100 * - cache the verification result in the iint, when available.
102 * Returns integrity status
104 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
105 const char *xattr_name,
107 size_t xattr_value_len,
108 struct integrity_iint_cache *iint)
110 struct evm_ima_xattr_data *xattr_data = NULL;
111 struct evm_ima_xattr_data calc;
112 enum integrity_status evm_status = INTEGRITY_PASS;
115 if (iint && iint->evm_status == INTEGRITY_PASS)
116 return iint->evm_status;
118 /* if status is not PASS, try to check again - against -ENOMEM */
120 /* first need to know the sig type */
121 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
125 evm_status = INTEGRITY_FAIL; /* empty */
126 else if (rc == -ENODATA) {
127 rc = evm_find_protected_xattrs(dentry);
129 evm_status = INTEGRITY_NOLABEL;
131 evm_status = INTEGRITY_NOXATTRS; /* new file */
138 /* check value type */
139 switch (xattr_data->type) {
141 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
142 xattr_value_len, calc.digest);
145 rc = memcmp(xattr_data->digest, calc.digest,
146 sizeof(calc.digest));
150 case EVM_IMA_XATTR_DIGSIG:
151 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
152 xattr_value_len, calc.digest);
155 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
156 (const char *)xattr_data, xattr_len,
157 calc.digest, sizeof(calc.digest));
159 /* we probably want to replace rsa with hmac here */
160 evm_update_evmxattr(dentry, xattr_name, xattr_value,
170 evm_status = (rc == -ENODATA) ?
171 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
174 iint->evm_status = evm_status;
179 static int evm_protected_xattr(const char *req_xattr_name)
185 namelen = strlen(req_xattr_name);
186 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
187 if ((strlen(*xattrname) == namelen)
188 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
192 if (strncmp(req_xattr_name,
193 *xattrname + XATTR_SECURITY_PREFIX_LEN,
194 strlen(req_xattr_name)) == 0) {
203 * evm_verifyxattr - verify the integrity of the requested xattr
204 * @dentry: object of the verify xattr
205 * @xattr_name: requested xattr
206 * @xattr_value: requested xattr value
207 * @xattr_value_len: requested xattr value length
209 * Calculate the HMAC for the given dentry and verify it against the stored
210 * security.evm xattr. For performance, use the xattr value and length
211 * previously retrieved to calculate the HMAC.
213 * Returns the xattr integrity status.
215 * This function requires the caller to lock the inode's i_mutex before it
218 enum integrity_status evm_verifyxattr(struct dentry *dentry,
219 const char *xattr_name,
220 void *xattr_value, size_t xattr_value_len,
221 struct integrity_iint_cache *iint)
223 if (!evm_initialized || !evm_protected_xattr(xattr_name))
224 return INTEGRITY_UNKNOWN;
227 iint = integrity_iint_find(dentry->d_inode);
229 return INTEGRITY_UNKNOWN;
231 return evm_verify_hmac(dentry, xattr_name, xattr_value,
232 xattr_value_len, iint);
234 EXPORT_SYMBOL_GPL(evm_verifyxattr);
237 * evm_verify_current_integrity - verify the dentry's metadata integrity
238 * @dentry: pointer to the affected dentry
240 * Verify and return the dentry's metadata integrity. The exceptions are
241 * before EVM is initialized or in 'fix' mode.
243 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
245 struct inode *inode = dentry->d_inode;
247 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
249 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
253 * evm_protect_xattr - protect the EVM extended attribute
255 * Prevent security.evm from being modified or removed without the
256 * necessary permissions or when the existing value is invalid.
258 * The posix xattr acls are 'system' prefixed, which normally would not
259 * affect security.evm. An interesting side affect of writing posix xattr
260 * acls is their modifying of the i_mode, which is included in security.evm.
261 * For posix xattr acls only, permit security.evm, even if it currently
262 * doesn't exist, to be updated.
264 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
265 const void *xattr_value, size_t xattr_value_len)
267 enum integrity_status evm_status;
269 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
270 if (!capable(CAP_SYS_ADMIN))
272 } else if (!evm_protected_xattr(xattr_name)) {
273 if (!posix_xattr_acl(xattr_name))
275 evm_status = evm_verify_current_integrity(dentry);
276 if ((evm_status == INTEGRITY_PASS) ||
277 (evm_status == INTEGRITY_NOXATTRS))
281 evm_status = evm_verify_current_integrity(dentry);
283 if (evm_status != INTEGRITY_PASS)
284 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
285 dentry->d_name.name, "appraise_metadata",
286 integrity_status_msg[evm_status],
288 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
292 * evm_inode_setxattr - protect the EVM extended attribute
293 * @dentry: pointer to the affected dentry
294 * @xattr_name: pointer to the affected extended attribute name
295 * @xattr_value: pointer to the new extended attribute value
296 * @xattr_value_len: pointer to the new extended attribute value length
298 * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
299 * the current value is valid.
301 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
302 const void *xattr_value, size_t xattr_value_len)
304 return evm_protect_xattr(dentry, xattr_name, xattr_value,
309 * evm_inode_removexattr - protect the EVM extended attribute
310 * @dentry: pointer to the affected dentry
311 * @xattr_name: pointer to the affected extended attribute name
313 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
314 * the current value is valid.
316 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
318 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
322 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
323 * @dentry: pointer to the affected dentry
324 * @xattr_name: pointer to the affected extended attribute name
325 * @xattr_value: pointer to the new extended attribute value
326 * @xattr_value_len: pointer to the new extended attribute value length
328 * Update the HMAC stored in 'security.evm' to reflect the change.
330 * No need to take the i_mutex lock here, as this function is called from
331 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
334 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
335 const void *xattr_value, size_t xattr_value_len)
337 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
338 && !posix_xattr_acl(xattr_name)))
341 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
346 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
347 * @dentry: pointer to the affected dentry
348 * @xattr_name: pointer to the affected extended attribute name
350 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
352 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
354 struct inode *inode = dentry->d_inode;
356 if (!evm_initialized || !evm_protected_xattr(xattr_name))
359 mutex_lock(&inode->i_mutex);
360 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
361 mutex_unlock(&inode->i_mutex);
366 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
367 * @dentry: pointer to the affected dentry
369 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
371 unsigned int ia_valid = attr->ia_valid;
372 enum integrity_status evm_status;
374 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
376 evm_status = evm_verify_current_integrity(dentry);
377 if ((evm_status == INTEGRITY_PASS) ||
378 (evm_status == INTEGRITY_NOXATTRS))
380 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
381 dentry->d_name.name, "appraise_metadata",
382 integrity_status_msg[evm_status], -EPERM, 0);
387 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
388 * @dentry: pointer to the affected dentry
389 * @ia_valid: for the UID and GID status
391 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
394 * This function is called from notify_change(), which expects the caller
395 * to lock the inode's i_mutex.
397 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
399 if (!evm_initialized)
402 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
403 evm_update_evmxattr(dentry, NULL, NULL, 0);
408 * evm_inode_init_security - initializes security.evm
410 int evm_inode_init_security(struct inode *inode,
411 const struct xattr *lsm_xattr,
412 struct xattr *evm_xattr)
414 struct evm_ima_xattr_data *xattr_data;
417 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
420 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
424 xattr_data->type = EVM_XATTR_HMAC;
425 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
429 evm_xattr->value = xattr_data;
430 evm_xattr->value_len = sizeof(*xattr_data);
431 evm_xattr->name = XATTR_EVM_SUFFIX;
437 EXPORT_SYMBOL_GPL(evm_inode_init_security);
439 static int __init init_evm(void)
445 error = evm_init_secfs();
447 pr_info("Error registering secfs\n");
457 * evm_display_config - list the EVM protected security extended attributes
459 static int __init evm_display_config(void)
463 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
464 pr_info("%s\n", *xattrname);
468 pure_initcall(evm_display_config);
469 late_initcall(init_evm);
471 MODULE_DESCRIPTION("Extended Verification Module");
472 MODULE_LICENSE("GPL");