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)";
29 char *evm_config_xattrnames[] = {
30 #ifdef CONFIG_SECURITY_SELINUX
33 #ifdef CONFIG_SECURITY_SMACK
40 static int evm_fixmode;
41 static int __init evm_set_fixmode(char *str)
43 if (strncmp(str, "fix", 3) == 0)
47 __setup("evm=", evm_set_fixmode);
50 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
52 * Compute the HMAC on the dentry's protected set of extended attributes
53 * and compare it against the stored security.evm xattr.
56 * - use the previoulsy retrieved xattr value and length to calculate the
58 * - cache the verification result in the iint, when available.
60 * Returns integrity status
62 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
63 const char *xattr_name,
65 size_t xattr_value_len,
66 struct integrity_iint_cache *iint)
68 struct evm_ima_xattr_data xattr_data;
69 enum integrity_status evm_status;
72 if (iint && iint->evm_status == INTEGRITY_PASS)
73 return iint->evm_status;
75 /* if status is not PASS, try to check again - against -ENOMEM */
77 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
78 xattr_value_len, xattr_data.digest);
82 xattr_data.type = EVM_XATTR_HMAC;
83 rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data,
84 sizeof xattr_data, GFP_NOFS);
87 evm_status = INTEGRITY_PASS;
92 case -ENODATA: /* file not labelled */
93 evm_status = INTEGRITY_NOLABEL;
96 evm_status = INTEGRITY_FAIL;
100 iint->evm_status = evm_status;
104 static int evm_protected_xattr(const char *req_xattr_name)
110 namelen = strlen(req_xattr_name);
111 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
112 if ((strlen(*xattrname) == namelen)
113 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
117 if (strncmp(req_xattr_name,
118 *xattrname + XATTR_SECURITY_PREFIX_LEN,
119 strlen(req_xattr_name)) == 0) {
128 * evm_verifyxattr - verify the integrity of the requested xattr
129 * @dentry: object of the verify xattr
130 * @xattr_name: requested xattr
131 * @xattr_value: requested xattr value
132 * @xattr_value_len: requested xattr value length
134 * Calculate the HMAC for the given dentry and verify it against the stored
135 * security.evm xattr. For performance, use the xattr value and length
136 * previously retrieved to calculate the HMAC.
138 * Returns the xattr integrity status.
140 * This function requires the caller to lock the inode's i_mutex before it
143 enum integrity_status evm_verifyxattr(struct dentry *dentry,
144 const char *xattr_name,
145 void *xattr_value, size_t xattr_value_len,
146 struct integrity_iint_cache *iint)
148 if (!evm_initialized || !evm_protected_xattr(xattr_name))
149 return INTEGRITY_UNKNOWN;
152 iint = integrity_iint_find(dentry->d_inode);
154 return INTEGRITY_UNKNOWN;
156 return evm_verify_hmac(dentry, xattr_name, xattr_value,
157 xattr_value_len, iint);
159 EXPORT_SYMBOL_GPL(evm_verifyxattr);
162 * evm_protect_xattr - protect the EVM extended attribute
164 * Prevent security.evm from being modified or removed.
166 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
167 const void *xattr_value, size_t xattr_value_len)
169 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
170 if (!capable(CAP_SYS_ADMIN))
177 * evm_verify_current_integrity - verify the dentry's metadata integrity
178 * @dentry: pointer to the affected dentry
180 * Verify and return the dentry's metadata integrity. The exceptions are
181 * before EVM is initialized or in 'fix' mode.
183 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
185 struct inode *inode = dentry->d_inode;
187 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
189 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
193 * evm_inode_setxattr - protect the EVM extended attribute
194 * @dentry: pointer to the affected dentry
195 * @xattr_name: pointer to the affected extended attribute name
196 * @xattr_value: pointer to the new extended attribute value
197 * @xattr_value_len: pointer to the new extended attribute value length
199 * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
200 * the current value is valid.
202 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
203 const void *xattr_value, size_t xattr_value_len)
206 enum integrity_status evm_status;
209 ret = evm_protect_xattr(dentry, xattr_name, xattr_value,
213 evm_status = evm_verify_current_integrity(dentry);
214 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
218 * evm_inode_removexattr - protect the EVM extended attribute
219 * @dentry: pointer to the affected dentry
220 * @xattr_name: pointer to the affected extended attribute name
222 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
223 * the current value is valid.
225 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
227 enum integrity_status evm_status;
230 ret = evm_protect_xattr(dentry, xattr_name, NULL, 0);
233 evm_status = evm_verify_current_integrity(dentry);
234 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
238 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
239 * @dentry: pointer to the affected dentry
240 * @xattr_name: pointer to the affected extended attribute name
241 * @xattr_value: pointer to the new extended attribute value
242 * @xattr_value_len: pointer to the new extended attribute value length
244 * Update the HMAC stored in 'security.evm' to reflect the change.
246 * No need to take the i_mutex lock here, as this function is called from
247 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
250 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
251 const void *xattr_value, size_t xattr_value_len)
253 if (!evm_initialized || !evm_protected_xattr(xattr_name))
256 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
261 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
262 * @dentry: pointer to the affected dentry
263 * @xattr_name: pointer to the affected extended attribute name
265 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
267 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
269 struct inode *inode = dentry->d_inode;
271 if (!evm_initialized || !evm_protected_xattr(xattr_name))
274 mutex_lock(&inode->i_mutex);
275 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
276 mutex_unlock(&inode->i_mutex);
281 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
282 * @dentry: pointer to the affected dentry
284 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
286 unsigned int ia_valid = attr->ia_valid;
287 enum integrity_status evm_status;
289 if (ia_valid & ~(ATTR_MODE | ATTR_UID | ATTR_GID))
291 evm_status = evm_verify_current_integrity(dentry);
292 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
296 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
297 * @dentry: pointer to the affected dentry
298 * @ia_valid: for the UID and GID status
300 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
303 * This function is called from notify_change(), which expects the caller
304 * to lock the inode's i_mutex.
306 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
308 if (!evm_initialized)
311 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
312 evm_update_evmxattr(dentry, NULL, NULL, 0);
317 * evm_inode_init_security - initializes security.evm
319 int evm_inode_init_security(struct inode *inode,
320 const struct xattr *lsm_xattr,
321 struct xattr *evm_xattr)
323 struct evm_ima_xattr_data *xattr_data;
326 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
329 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
333 xattr_data->type = EVM_XATTR_HMAC;
334 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
338 evm_xattr->value = xattr_data;
339 evm_xattr->value_len = sizeof(*xattr_data);
340 evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS);
346 EXPORT_SYMBOL_GPL(evm_inode_init_security);
348 static int __init init_evm(void)
352 error = evm_init_secfs();
354 printk(KERN_INFO "EVM: Error registering secfs\n");
361 static void __exit cleanup_evm(void)
365 crypto_free_shash(hmac_tfm);
369 * evm_display_config - list the EVM protected security extended attributes
371 static int __init evm_display_config(void)
375 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
376 printk(KERN_INFO "EVM: %s\n", *xattrname);
380 pure_initcall(evm_display_config);
381 late_initcall(init_evm);
383 MODULE_DESCRIPTION("Extended Verification Module");
384 MODULE_LICENSE("GPL");