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_verify_current_integrity - verify the dentry's metadata integrity
163 * @dentry: pointer to the affected dentry
165 * Verify and return the dentry's metadata integrity. The exceptions are
166 * before EVM is initialized or in 'fix' mode.
168 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
170 struct inode *inode = dentry->d_inode;
172 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
174 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
178 * evm_protect_xattr - protect the EVM extended attribute
180 * Prevent security.evm from being modified or removed without the
181 * necessary permissions or when the existing value is invalid.
183 * The posix xattr acls are 'system' prefixed, which normally would not
184 * affect security.evm. An interesting side affect of writing posix xattr
185 * acls is their modifying of the i_mode, which is included in security.evm.
186 * For posix xattr acls only, permit security.evm, even if it currently
187 * doesn't exist, to be updated.
189 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
190 const void *xattr_value, size_t xattr_value_len)
192 enum integrity_status evm_status;
194 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
195 if (!capable(CAP_SYS_ADMIN))
197 } else if (!evm_protected_xattr(xattr_name)) {
198 if (!posix_xattr_acl(xattr_name))
200 evm_status = evm_verify_current_integrity(dentry);
201 if ((evm_status == INTEGRITY_PASS) ||
202 (evm_status == INTEGRITY_NOLABEL))
206 evm_status = evm_verify_current_integrity(dentry);
207 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
211 * evm_inode_setxattr - protect the EVM extended attribute
212 * @dentry: pointer to the affected dentry
213 * @xattr_name: pointer to the affected extended attribute name
214 * @xattr_value: pointer to the new extended attribute value
215 * @xattr_value_len: pointer to the new extended attribute value length
217 * Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that
218 * the current value is valid.
220 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
221 const void *xattr_value, size_t xattr_value_len)
223 return evm_protect_xattr(dentry, xattr_name, xattr_value,
228 * evm_inode_removexattr - protect the EVM extended attribute
229 * @dentry: pointer to the affected dentry
230 * @xattr_name: pointer to the affected extended attribute name
232 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
233 * the current value is valid.
235 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
237 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
241 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
242 * @dentry: pointer to the affected dentry
243 * @xattr_name: pointer to the affected extended attribute name
244 * @xattr_value: pointer to the new extended attribute value
245 * @xattr_value_len: pointer to the new extended attribute value length
247 * Update the HMAC stored in 'security.evm' to reflect the change.
249 * No need to take the i_mutex lock here, as this function is called from
250 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
253 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
254 const void *xattr_value, size_t xattr_value_len)
256 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
257 && !posix_xattr_acl(xattr_name)))
260 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
265 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
266 * @dentry: pointer to the affected dentry
267 * @xattr_name: pointer to the affected extended attribute name
269 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
271 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
273 struct inode *inode = dentry->d_inode;
275 if (!evm_initialized || !evm_protected_xattr(xattr_name))
278 mutex_lock(&inode->i_mutex);
279 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
280 mutex_unlock(&inode->i_mutex);
285 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
286 * @dentry: pointer to the affected dentry
288 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
290 unsigned int ia_valid = attr->ia_valid;
291 enum integrity_status evm_status;
293 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
295 evm_status = evm_verify_current_integrity(dentry);
296 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
300 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
301 * @dentry: pointer to the affected dentry
302 * @ia_valid: for the UID and GID status
304 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
307 * This function is called from notify_change(), which expects the caller
308 * to lock the inode's i_mutex.
310 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
312 if (!evm_initialized)
315 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
316 evm_update_evmxattr(dentry, NULL, NULL, 0);
321 * evm_inode_init_security - initializes security.evm
323 int evm_inode_init_security(struct inode *inode,
324 const struct xattr *lsm_xattr,
325 struct xattr *evm_xattr)
327 struct evm_ima_xattr_data *xattr_data;
330 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
333 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
337 xattr_data->type = EVM_XATTR_HMAC;
338 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
342 evm_xattr->value = xattr_data;
343 evm_xattr->value_len = sizeof(*xattr_data);
344 evm_xattr->name = kstrdup(XATTR_EVM_SUFFIX, GFP_NOFS);
350 EXPORT_SYMBOL_GPL(evm_inode_init_security);
352 static int __init init_evm(void)
356 error = evm_init_secfs();
358 printk(KERN_INFO "EVM: Error registering secfs\n");
365 static void __exit cleanup_evm(void)
369 crypto_free_shash(hmac_tfm);
373 * evm_display_config - list the EVM protected security extended attributes
375 static int __init evm_display_config(void)
379 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
380 printk(KERN_INFO "EVM: %s\n", *xattrname);
384 pure_initcall(evm_display_config);
385 late_initcall(init_evm);
387 MODULE_DESCRIPTION("Extended Verification Module");
388 MODULE_LICENSE("GPL");