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>
26 #include <crypto/algapi.h>
31 static char *integrity_status_msg[] = {
32 "pass", "fail", "no_label", "no_xattrs", "unknown"
34 char *evm_hmac = "hmac(sha1)";
35 char *evm_hash = "sha1";
38 char *evm_config_xattrnames[] = {
39 #ifdef CONFIG_SECURITY_SELINUX
42 #ifdef CONFIG_SECURITY_SMACK
44 #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS
46 XATTR_NAME_SMACKTRANSMUTE,
50 #ifdef CONFIG_IMA_APPRAISE
57 static int evm_fixmode;
58 static int __init evm_set_fixmode(char *str)
60 if (strncmp(str, "fix", 3) == 0)
64 __setup("evm=", evm_set_fixmode);
66 static void __init evm_init_config(void)
68 #ifdef CONFIG_EVM_ATTR_FSUUID
69 evm_hmac_attrs |= EVM_ATTR_FSUUID;
71 pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs);
74 static int evm_find_protected_xattrs(struct dentry *dentry)
76 struct inode *inode = d_backing_inode(dentry);
81 if (!inode->i_op->getxattr)
84 for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) {
85 error = inode->i_op->getxattr(dentry, *xattr, NULL, 0);
87 if (error == -ENODATA)
98 * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
100 * Compute the HMAC on the dentry's protected set of extended attributes
101 * and compare it against the stored security.evm xattr.
104 * - use the previoulsy retrieved xattr value and length to calculate the
106 * - cache the verification result in the iint, when available.
108 * Returns integrity status
110 static enum integrity_status evm_verify_hmac(struct dentry *dentry,
111 const char *xattr_name,
113 size_t xattr_value_len,
114 struct integrity_iint_cache *iint)
116 struct evm_ima_xattr_data *xattr_data = NULL;
117 struct evm_ima_xattr_data calc;
118 enum integrity_status evm_status = INTEGRITY_PASS;
121 if (iint && iint->evm_status == INTEGRITY_PASS)
122 return iint->evm_status;
124 /* if status is not PASS, try to check again - against -ENOMEM */
126 /* first need to know the sig type */
127 rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0,
130 evm_status = INTEGRITY_FAIL;
131 if (rc == -ENODATA) {
132 rc = evm_find_protected_xattrs(dentry);
134 evm_status = INTEGRITY_NOLABEL;
136 evm_status = INTEGRITY_NOXATTRS; /* new file */
137 } else if (rc == -EOPNOTSUPP) {
138 evm_status = INTEGRITY_UNKNOWN;
145 /* check value type */
146 switch (xattr_data->type) {
148 rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
149 xattr_value_len, calc.digest);
152 rc = crypto_memneq(xattr_data->digest, calc.digest,
153 sizeof(calc.digest));
157 case EVM_IMA_XATTR_DIGSIG:
158 rc = evm_calc_hash(dentry, xattr_name, xattr_value,
159 xattr_value_len, calc.digest);
162 rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM,
163 (const char *)xattr_data, xattr_len,
164 calc.digest, sizeof(calc.digest));
166 /* Replace RSA with HMAC if not mounted readonly and
169 if (!IS_RDONLY(d_backing_inode(dentry)) &&
170 !IS_IMMUTABLE(d_backing_inode(dentry)))
171 evm_update_evmxattr(dentry, xattr_name,
182 evm_status = (rc == -ENODATA) ?
183 INTEGRITY_NOXATTRS : INTEGRITY_FAIL;
186 iint->evm_status = evm_status;
191 static int evm_protected_xattr(const char *req_xattr_name)
197 namelen = strlen(req_xattr_name);
198 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
199 if ((strlen(*xattrname) == namelen)
200 && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) {
204 if (strncmp(req_xattr_name,
205 *xattrname + XATTR_SECURITY_PREFIX_LEN,
206 strlen(req_xattr_name)) == 0) {
215 * evm_verifyxattr - verify the integrity of the requested xattr
216 * @dentry: object of the verify xattr
217 * @xattr_name: requested xattr
218 * @xattr_value: requested xattr value
219 * @xattr_value_len: requested xattr value length
221 * Calculate the HMAC for the given dentry and verify it against the stored
222 * security.evm xattr. For performance, use the xattr value and length
223 * previously retrieved to calculate the HMAC.
225 * Returns the xattr integrity status.
227 * This function requires the caller to lock the inode's i_mutex before it
230 enum integrity_status evm_verifyxattr(struct dentry *dentry,
231 const char *xattr_name,
232 void *xattr_value, size_t xattr_value_len,
233 struct integrity_iint_cache *iint)
235 if (!evm_initialized || !evm_protected_xattr(xattr_name))
236 return INTEGRITY_UNKNOWN;
239 iint = integrity_iint_find(d_backing_inode(dentry));
241 return INTEGRITY_UNKNOWN;
243 return evm_verify_hmac(dentry, xattr_name, xattr_value,
244 xattr_value_len, iint);
246 EXPORT_SYMBOL_GPL(evm_verifyxattr);
249 * evm_verify_current_integrity - verify the dentry's metadata integrity
250 * @dentry: pointer to the affected dentry
252 * Verify and return the dentry's metadata integrity. The exceptions are
253 * before EVM is initialized or in 'fix' mode.
255 static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
257 struct inode *inode = d_backing_inode(dentry);
259 if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode)
261 return evm_verify_hmac(dentry, NULL, NULL, 0, NULL);
265 * evm_protect_xattr - protect the EVM extended attribute
267 * Prevent security.evm from being modified or removed without the
268 * necessary permissions or when the existing value is invalid.
270 * The posix xattr acls are 'system' prefixed, which normally would not
271 * affect security.evm. An interesting side affect of writing posix xattr
272 * acls is their modifying of the i_mode, which is included in security.evm.
273 * For posix xattr acls only, permit security.evm, even if it currently
274 * doesn't exist, to be updated.
276 static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
277 const void *xattr_value, size_t xattr_value_len)
279 enum integrity_status evm_status;
281 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
282 if (!capable(CAP_SYS_ADMIN))
284 } else if (!evm_protected_xattr(xattr_name)) {
285 if (!posix_xattr_acl(xattr_name))
287 evm_status = evm_verify_current_integrity(dentry);
288 if ((evm_status == INTEGRITY_PASS) ||
289 (evm_status == INTEGRITY_NOXATTRS))
293 evm_status = evm_verify_current_integrity(dentry);
294 if (evm_status == INTEGRITY_NOXATTRS) {
295 struct integrity_iint_cache *iint;
297 iint = integrity_iint_find(d_backing_inode(dentry));
298 if (iint && (iint->flags & IMA_NEW_FILE))
301 /* exception for pseudo filesystems */
302 if (dentry->d_inode->i_sb->s_magic == TMPFS_MAGIC
303 || dentry->d_inode->i_sb->s_magic == SYSFS_MAGIC)
306 integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
307 dentry->d_inode, dentry->d_name.name,
309 integrity_status_msg[evm_status],
313 if (evm_status != INTEGRITY_PASS)
314 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
315 dentry->d_name.name, "appraise_metadata",
316 integrity_status_msg[evm_status],
318 return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
322 * evm_inode_setxattr - protect the EVM extended attribute
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 * Before allowing the 'security.evm' protected xattr to be updated,
329 * verify the existing value is valid. As only the kernel should have
330 * access to the EVM encrypted key needed to calculate the HMAC, prevent
331 * userspace from writing HMAC value. Writing 'security.evm' requires
332 * requires CAP_SYS_ADMIN privileges.
334 int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
335 const void *xattr_value, size_t xattr_value_len)
337 const struct evm_ima_xattr_data *xattr_data = xattr_value;
339 if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
340 if (!xattr_value_len)
342 if (xattr_data->type != EVM_IMA_XATTR_DIGSIG)
345 return evm_protect_xattr(dentry, xattr_name, xattr_value,
350 * evm_inode_removexattr - protect the EVM extended attribute
351 * @dentry: pointer to the affected dentry
352 * @xattr_name: pointer to the affected extended attribute name
354 * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that
355 * the current value is valid.
357 int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
359 return evm_protect_xattr(dentry, xattr_name, NULL, 0);
363 * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
364 * @dentry: pointer to the affected dentry
365 * @xattr_name: pointer to the affected extended attribute name
366 * @xattr_value: pointer to the new extended attribute value
367 * @xattr_value_len: pointer to the new extended attribute value length
369 * Update the HMAC stored in 'security.evm' to reflect the change.
371 * No need to take the i_mutex lock here, as this function is called from
372 * __vfs_setxattr_noperm(). The caller of which has taken the inode's
375 void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
376 const void *xattr_value, size_t xattr_value_len)
378 if (!evm_initialized || (!evm_protected_xattr(xattr_name)
379 && !posix_xattr_acl(xattr_name)))
382 evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
386 * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
387 * @dentry: pointer to the affected dentry
388 * @xattr_name: pointer to the affected extended attribute name
390 * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
392 * No need to take the i_mutex lock here, as this function is called from
393 * vfs_removexattr() which takes the i_mutex.
395 void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
397 if (!evm_initialized || !evm_protected_xattr(xattr_name))
400 evm_update_evmxattr(dentry, xattr_name, NULL, 0);
404 * evm_inode_setattr - prevent updating an invalid EVM extended attribute
405 * @dentry: pointer to the affected dentry
407 int evm_inode_setattr(struct dentry *dentry, struct iattr *attr)
409 unsigned int ia_valid = attr->ia_valid;
410 enum integrity_status evm_status;
412 if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
414 evm_status = evm_verify_current_integrity(dentry);
415 if ((evm_status == INTEGRITY_PASS) ||
416 (evm_status == INTEGRITY_NOXATTRS))
418 integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry),
419 dentry->d_name.name, "appraise_metadata",
420 integrity_status_msg[evm_status], -EPERM, 0);
425 * evm_inode_post_setattr - update 'security.evm' after modifying metadata
426 * @dentry: pointer to the affected dentry
427 * @ia_valid: for the UID and GID status
429 * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
432 * This function is called from notify_change(), which expects the caller
433 * to lock the inode's i_mutex.
435 void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
437 if (!evm_initialized)
440 if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
441 evm_update_evmxattr(dentry, NULL, NULL, 0);
445 * evm_inode_init_security - initializes security.evm
447 int evm_inode_init_security(struct inode *inode,
448 const struct xattr *lsm_xattr,
449 struct xattr *evm_xattr)
451 struct evm_ima_xattr_data *xattr_data;
454 if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name))
457 xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS);
461 xattr_data->type = EVM_XATTR_HMAC;
462 rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest);
466 evm_xattr->value = xattr_data;
467 evm_xattr->value_len = sizeof(*xattr_data);
468 evm_xattr->name = XATTR_EVM_SUFFIX;
474 EXPORT_SYMBOL_GPL(evm_inode_init_security);
476 static int __init init_evm(void)
482 error = evm_init_secfs();
484 pr_info("Error registering secfs\n");
494 * evm_display_config - list the EVM protected security extended attributes
496 static int __init evm_display_config(void)
500 for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
501 pr_info("%s\n", *xattrname);
505 pure_initcall(evm_display_config);
506 late_initcall(init_evm);
508 MODULE_DESCRIPTION("Extended Verification Module");
509 MODULE_LICENSE("GPL");