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
43 #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
45 XATTR_NAME_SMACKTRANSMUTE,
49 #ifdef CONFIG_IMA_APPRAISE
56 static int evm_fixmode;
57 static int __init evm_set_fixmode(char *str)
59 if (strncmp(str, "fix", 3) == 0)
63 __setup("evm=", evm_set_fixmode);
65 static void __init evm_init_config(void)
67 #ifdef CONFIG_EVM_ATTR_FSUUID
68 evm_hmac_attrs |= EVM_ATTR_FSUUID;
70 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
73 static int evm_find_protected_xattrs(struct dentry *dentry)
75 struct inode *inode = dentry->d_inode;
80 if (!inode->i_op->getxattr)
83 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
84 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
86 if (error == -ENODATA)
97 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
99 * Compute the HMAC on the dentry's protected set of extended attributes
100 * and compare it against the stored security.evm xattr.
103 * - use the previoulsy retrieved xattr value and length to calculate the
105 * - cache the verification result in the iint, when available.
107 * Returns integrity status
109 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
110 const char *xattr_name,
112 size_t xattr_value_len,
113 struct integrity_iint_cache *iint)
115 struct evm_ima_xattr_data *xattr_data = NULL;
116 struct evm_ima_xattr_data calc;
117 enum integrity_status evm_status = INTEGRITY_PASS;
120 if (iint && iint->evm_status == INTEGRITY_PASS)
121 return iint->evm_status;
123 /* if status is not PASS, try to check again - against -ENOMEM */
125 /* first need to know the sig type */
126 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
130 evm_status = INTEGRITY_FAIL; /* empty */
131 else if (rc == -ENODATA) {
132 rc = evm_find_protected_xattrs(dentry);
134 evm_status = INTEGRITY_NOLABEL;
136 evm_status = INTEGRITY_NOXATTRS; /* new file */
143 /* check value type */
144 switch (xattr_data->type) {
146 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
147 xattr_value_len, calc.digest);
150 rc = memcmp(xattr_data->digest, calc.digest,
151 sizeof(calc.digest));
155 case EVM_IMA_XATTR_DIGSIG:
156 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
157 xattr_value_len, calc.digest);
160 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
161 (const char *)xattr_data, xattr_len,
162 calc.digest, sizeof(calc.digest));
164 /* we probably want to replace rsa with hmac here */
165 evm_update_evmxattr(dentry, xattr_name, xattr_value,
175 evm_status = (rc == -ENODATA) ?
176 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
179 iint->evm_status = evm_status;
184 static int evm_protected_xattr(const char *req_xattr_name)
190 namelen = strlen(req_xattr_name);
191 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
192 if ((strlen(*xattrname) == namelen)
193 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
197 if (strncmp(req_xattr_name,
198 *xattrname + XATTR_SECURITY_PREFIX_LEN,
199 strlen(req_xattr_name)) == 0) {
208 * evm_verifyxattr - verify the integrity of the requested xattr
209 * @dentry: object of the verify xattr
210 * @xattr_name: requested xattr
211 * @xattr_value: requested xattr value
212 * @xattr_value_len: requested xattr value length
214 * Calculate the HMAC for the given dentry and verify it against the stored
215 * security.evm xattr. For performance, use the xattr value and length
216 * previously retrieved to calculate the HMAC.
218 * Returns the xattr integrity status.
220 * This function requires the caller to lock the inode's i_mutex before it
223 enum integrity_status evm_verifyxattr(struct dentry *dentry,
224 const char *xattr_name,
225 void *xattr_value, size_t xattr_value_len,
226 struct integrity_iint_cache *iint)
228 if (!evm_initialized || !evm_protected_xattr(xattr_name))
229 return INTEGRITY_UNKNOWN;
232 iint = integrity_iint_find(dentry->d_inode);
234 return INTEGRITY_UNKNOWN;
236 return evm_verify_hmac(dentry, xattr_name, xattr_value,
237 xattr_value_len, iint);
239 EXPORT_SYMBOL_GPL(evm_verifyxattr);
242 * evm_verify_current_integrity - verify the dentry's metadata integrity
243 * @dentry: pointer to the affected dentry
245 * Verify and return the dentry's metadata integrity. The exceptions are
246 * before EVM is initialized or in 'fix' mode.
248 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
250 struct inode *inode = dentry->d_inode;
252 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
254 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
258 * evm_protect_xattr - protect the EVM extended attribute
260 * Prevent security.evm from being modified or removed without the
261 * necessary permissions or when the existing value is invalid.
263 * The posix xattr acls are 'system' prefixed, which normally would not
264 * affect security.evm. An interesting side affect of writing posix xattr
265 * acls is their modifying of the i_mode, which is included in security.evm.
266 * For posix xattr acls only, permit security.evm, even if it currently
267 * doesn't exist, to be updated.
269 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
270 const void *xattr_value, size_t xattr_value_len)
272 enum integrity_status evm_status;
274 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
275 if (!capable(CAP_SYS_ADMIN))
277 } else if (!evm_protected_xattr(xattr_name)) {
278 if (!posix_xattr_acl(xattr_name))
280 evm_status = evm_verify_current_integrity(dentry);
281 if ((evm_status == INTEGRITY_PASS) ||
282 (evm_status == INTEGRITY_NOXATTRS))
286 evm_status = evm_verify_current_integrity(dentry);
288 if (evm_status != INTEGRITY_PASS)
289 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
290 dentry->d_name.name, "appraise_metadata",
291 integrity_status_msg[evm_status],
293 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
297 * evm_inode_setxattr - protect the EVM extended attribute
298 * @dentry: pointer to the affected dentry
299 * @xattr_name: pointer to the affected extended attribute name
300 * @xattr_value: pointer to the new extended attribute value
301 * @xattr_value_len: pointer to the new extended attribute value length
303 * Before allowing the 'security.evm' protected xattr to be updated,
304 * verify the existing value is valid. As only the kernel should have
305 * access to the EVM encrypted key needed to calculate the HMAC, prevent
306 * userspace from writing HMAC value. Writing 'security.evm' requires
307 * requires CAP_SYS_ADMIN privileges.
309 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
310 const void *xattr_value, size_t xattr_value_len)
312 const struct evm_ima_xattr_data *xattr_data = xattr_value;
314 if ((strcmp(xattr_name, XATTR_NAME_EVM) == 0)
315 && (xattr_data->type == EVM_XATTR_HMAC))
317 return evm_protect_xattr(dentry, xattr_name, xattr_value,
322 * evm_inode_removexattr - protect the EVM extended attribute
323 * @dentry: pointer to the affected dentry
324 * @xattr_name: pointer to the affected extended attribute name
326 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
327 * the current value is valid.
329 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
331 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
335 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
336 * @dentry: pointer to the affected dentry
337 * @xattr_name: pointer to the affected extended attribute name
338 * @xattr_value: pointer to the new extended attribute value
339 * @xattr_value_len: pointer to the new extended attribute value length
341 * Update the HMAC stored in 'security.evm' to reflect the change.
343 * No need to take the i_mutex lock here, as this function is called from
344 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
347 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
348 const void *xattr_value, size_t xattr_value_len)
350 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
351 && !posix_xattr_acl(xattr_name)))
354 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
359 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
360 * @dentry: pointer to the affected dentry
361 * @xattr_name: pointer to the affected extended attribute name
363 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
365 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
367 struct inode *inode = dentry->d_inode;
369 if (!evm_initialized || !evm_protected_xattr(xattr_name))
372 mutex_lock(&inode->i_mutex);
373 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
374 mutex_unlock(&inode->i_mutex);
379 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
380 * @dentry: pointer to the affected dentry
382 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
384 unsigned int ia_valid = attr->ia_valid;
385 enum integrity_status evm_status;
387 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
389 evm_status = evm_verify_current_integrity(dentry);
390 if ((evm_status == INTEGRITY_PASS) ||
391 (evm_status == INTEGRITY_NOXATTRS))
393 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode,
394 dentry->d_name.name, "appraise_metadata",
395 integrity_status_msg[evm_status], -EPERM, 0);
400 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
401 * @dentry: pointer to the affected dentry
402 * @ia_valid: for the UID and GID status
404 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
407 * This function is called from notify_change(), which expects the caller
408 * to lock the inode's i_mutex.
410 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
412 if (!evm_initialized)
415 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
416 evm_update_evmxattr(dentry, NULL, NULL, 0);
421 * evm_inode_init_security - initializes security.evm
423 int evm_inode_init_security(struct inode *inode,
424 const struct xattr *lsm_xattr,
425 struct xattr *evm_xattr)
427 struct evm_ima_xattr_data *xattr_data;
430 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
433 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
437 xattr_data->type = EVM_XATTR_HMAC;
438 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
442 evm_xattr->value = xattr_data;
443 evm_xattr->value_len = sizeof(*xattr_data);
444 evm_xattr->name = XATTR_EVM_SUFFIX;
450 EXPORT_SYMBOL_GPL(evm_inode_init_security);
452 static int __init init_evm(void)
458 error = evm_init_secfs();
460 pr_info("Error registering secfs\n");
470 * evm_display_config - list the EVM protected security extended attributes
472 static int __init evm_display_config(void)
476 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
477 pr_info("%s\n", *xattrname);
481 pure_initcall(evm_display_config);
482 late_initcall(init_evm);
484 MODULE_DESCRIPTION("Extended Verification Module");
485 MODULE_LICENSE("GPL");