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66dbc325 MZ |
1 | /* |
2 | * Copyright (C) 2005-2010 IBM Corporation | |
3 | * | |
4 | * Author: | |
5 | * Mimi Zohar <zohar@us.ibm.com> | |
6 | * Kylene Hall <kjhall@us.ibm.com> | |
7 | * | |
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. | |
11 | * | |
12 | * File: evm_main.c | |
13 | * implements evm_inode_setxattr, evm_inode_post_setxattr, | |
14 | * evm_inode_removexattr, and evm_verifyxattr | |
15 | */ | |
16 | ||
20ee451f JP |
17 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
18 | ||
66dbc325 MZ |
19 | #include <linux/module.h> |
20 | #include <linux/crypto.h> | |
9b97b6cd | 21 | #include <linux/audit.h> |
66dbc325 MZ |
22 | #include <linux/xattr.h> |
23 | #include <linux/integrity.h> | |
3e1be52d | 24 | #include <linux/evm.h> |
d46eb369 | 25 | #include <crypto/hash.h> |
66dbc325 MZ |
26 | #include "evm.h" |
27 | ||
28 | int evm_initialized; | |
29 | ||
9b97b6cd MZ |
30 | static char *integrity_status_msg[] = { |
31 | "pass", "fail", "no_label", "no_xattrs", "unknown" | |
32 | }; | |
66dbc325 | 33 | char *evm_hmac = "hmac(sha1)"; |
15647eb3 | 34 | char *evm_hash = "sha1"; |
d3b33679 | 35 | int evm_hmac_attrs; |
66dbc325 MZ |
36 | |
37 | char *evm_config_xattrnames[] = { | |
38 | #ifdef CONFIG_SECURITY_SELINUX | |
39 | XATTR_NAME_SELINUX, | |
40 | #endif | |
41 | #ifdef CONFIG_SECURITY_SMACK | |
42 | XATTR_NAME_SMACK, | |
3e38df56 DK |
43 | #ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS |
44 | XATTR_NAME_SMACKEXEC, | |
45 | XATTR_NAME_SMACKTRANSMUTE, | |
46 | XATTR_NAME_SMACKMMAP, | |
47 | #endif | |
2fe5d6de MZ |
48 | #endif |
49 | #ifdef CONFIG_IMA_APPRAISE | |
50 | XATTR_NAME_IMA, | |
66dbc325 MZ |
51 | #endif |
52 | XATTR_NAME_CAPS, | |
53 | NULL | |
54 | }; | |
55 | ||
7102ebcd MZ |
56 | static int evm_fixmode; |
57 | static int __init evm_set_fixmode(char *str) | |
58 | { | |
59 | if (strncmp(str, "fix", 3) == 0) | |
60 | evm_fixmode = 1; | |
61 | return 0; | |
62 | } | |
63 | __setup("evm=", evm_set_fixmode); | |
64 | ||
d3b33679 DK |
65 | static void __init evm_init_config(void) |
66 | { | |
67 | #ifdef CONFIG_EVM_ATTR_FSUUID | |
68 | evm_hmac_attrs |= EVM_ATTR_FSUUID; | |
69 | #endif | |
70 | pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs); | |
71 | } | |
72 | ||
15647eb3 DK |
73 | static int evm_find_protected_xattrs(struct dentry *dentry) |
74 | { | |
75 | struct inode *inode = dentry->d_inode; | |
76 | char **xattr; | |
77 | int error; | |
78 | int count = 0; | |
79 | ||
627bf81a | 80 | if (!inode->i_op->getxattr) |
15647eb3 DK |
81 | return -EOPNOTSUPP; |
82 | ||
83 | for (xattr = evm_config_xattrnames; *xattr != NULL; xattr++) { | |
84 | error = inode->i_op->getxattr(dentry, *xattr, NULL, 0); | |
85 | if (error < 0) { | |
86 | if (error == -ENODATA) | |
87 | continue; | |
88 | return error; | |
89 | } | |
90 | count++; | |
91 | } | |
92 | ||
93 | return count; | |
94 | } | |
95 | ||
66dbc325 MZ |
96 | /* |
97 | * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr | |
98 | * | |
99 | * Compute the HMAC on the dentry's protected set of extended attributes | |
7102ebcd MZ |
100 | * and compare it against the stored security.evm xattr. |
101 | * | |
102 | * For performance: | |
103 | * - use the previoulsy retrieved xattr value and length to calculate the | |
104 | * HMAC.) | |
105 | * - cache the verification result in the iint, when available. | |
66dbc325 MZ |
106 | * |
107 | * Returns integrity status | |
108 | */ | |
109 | static enum integrity_status evm_verify_hmac(struct dentry *dentry, | |
110 | const char *xattr_name, | |
111 | char *xattr_value, | |
112 | size_t xattr_value_len, | |
113 | struct integrity_iint_cache *iint) | |
114 | { | |
15647eb3 DK |
115 | struct evm_ima_xattr_data *xattr_data = NULL; |
116 | struct evm_ima_xattr_data calc; | |
566be59a | 117 | enum integrity_status evm_status = INTEGRITY_PASS; |
15647eb3 | 118 | int rc, xattr_len; |
66dbc325 | 119 | |
7102ebcd | 120 | if (iint && iint->evm_status == INTEGRITY_PASS) |
24e0198e | 121 | return iint->evm_status; |
66dbc325 | 122 | |
6d38ca01 DK |
123 | /* if status is not PASS, try to check again - against -ENOMEM */ |
124 | ||
15647eb3 DK |
125 | /* first need to know the sig type */ |
126 | rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0, | |
127 | GFP_NOFS); | |
128 | if (rc <= 0) { | |
1f100979 DK |
129 | evm_status = INTEGRITY_FAIL; |
130 | if (rc == -ENODATA) { | |
15647eb3 DK |
131 | rc = evm_find_protected_xattrs(dentry); |
132 | if (rc > 0) | |
133 | evm_status = INTEGRITY_NOLABEL; | |
134 | else if (rc == 0) | |
135 | evm_status = INTEGRITY_NOXATTRS; /* new file */ | |
1f100979 DK |
136 | } else if (rc == -EOPNOTSUPP) { |
137 | evm_status = INTEGRITY_UNKNOWN; | |
15647eb3 | 138 | } |
566be59a MZ |
139 | goto out; |
140 | } | |
66dbc325 | 141 | |
b1aaab22 | 142 | xattr_len = rc; |
15647eb3 DK |
143 | |
144 | /* check value type */ | |
145 | switch (xattr_data->type) { | |
146 | case EVM_XATTR_HMAC: | |
147 | rc = evm_calc_hmac(dentry, xattr_name, xattr_value, | |
148 | xattr_value_len, calc.digest); | |
149 | if (rc) | |
150 | break; | |
151 | rc = memcmp(xattr_data->digest, calc.digest, | |
152 | sizeof(calc.digest)); | |
153 | if (rc) | |
154 | rc = -EINVAL; | |
155 | break; | |
156 | case EVM_IMA_XATTR_DIGSIG: | |
157 | rc = evm_calc_hash(dentry, xattr_name, xattr_value, | |
158 | xattr_value_len, calc.digest); | |
159 | if (rc) | |
160 | break; | |
161 | rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, | |
b1aaab22 | 162 | (const char *)xattr_data, xattr_len, |
15647eb3 DK |
163 | calc.digest, sizeof(calc.digest)); |
164 | if (!rc) { | |
165 | /* we probably want to replace rsa with hmac here */ | |
166 | evm_update_evmxattr(dentry, xattr_name, xattr_value, | |
167 | xattr_value_len); | |
168 | } | |
169 | break; | |
170 | default: | |
171 | rc = -EINVAL; | |
172 | break; | |
173 | } | |
174 | ||
175 | if (rc) | |
176 | evm_status = (rc == -ENODATA) ? | |
177 | INTEGRITY_NOXATTRS : INTEGRITY_FAIL; | |
7102ebcd MZ |
178 | out: |
179 | if (iint) | |
180 | iint->evm_status = evm_status; | |
15647eb3 | 181 | kfree(xattr_data); |
7102ebcd | 182 | return evm_status; |
66dbc325 MZ |
183 | } |
184 | ||
185 | static int evm_protected_xattr(const char *req_xattr_name) | |
186 | { | |
187 | char **xattrname; | |
188 | int namelen; | |
189 | int found = 0; | |
190 | ||
191 | namelen = strlen(req_xattr_name); | |
192 | for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) { | |
193 | if ((strlen(*xattrname) == namelen) | |
194 | && (strncmp(req_xattr_name, *xattrname, namelen) == 0)) { | |
195 | found = 1; | |
196 | break; | |
197 | } | |
cb723180 MZ |
198 | if (strncmp(req_xattr_name, |
199 | *xattrname + XATTR_SECURITY_PREFIX_LEN, | |
200 | strlen(req_xattr_name)) == 0) { | |
201 | found = 1; | |
202 | break; | |
203 | } | |
66dbc325 MZ |
204 | } |
205 | return found; | |
206 | } | |
207 | ||
208 | /** | |
209 | * evm_verifyxattr - verify the integrity of the requested xattr | |
210 | * @dentry: object of the verify xattr | |
211 | * @xattr_name: requested xattr | |
212 | * @xattr_value: requested xattr value | |
213 | * @xattr_value_len: requested xattr value length | |
214 | * | |
215 | * Calculate the HMAC for the given dentry and verify it against the stored | |
216 | * security.evm xattr. For performance, use the xattr value and length | |
217 | * previously retrieved to calculate the HMAC. | |
218 | * | |
219 | * Returns the xattr integrity status. | |
220 | * | |
221 | * This function requires the caller to lock the inode's i_mutex before it | |
222 | * is executed. | |
223 | */ | |
224 | enum integrity_status evm_verifyxattr(struct dentry *dentry, | |
225 | const char *xattr_name, | |
2960e6cb DK |
226 | void *xattr_value, size_t xattr_value_len, |
227 | struct integrity_iint_cache *iint) | |
66dbc325 | 228 | { |
66dbc325 MZ |
229 | if (!evm_initialized || !evm_protected_xattr(xattr_name)) |
230 | return INTEGRITY_UNKNOWN; | |
231 | ||
2960e6cb DK |
232 | if (!iint) { |
233 | iint = integrity_iint_find(dentry->d_inode); | |
234 | if (!iint) | |
235 | return INTEGRITY_UNKNOWN; | |
236 | } | |
237 | return evm_verify_hmac(dentry, xattr_name, xattr_value, | |
66dbc325 | 238 | xattr_value_len, iint); |
66dbc325 MZ |
239 | } |
240 | EXPORT_SYMBOL_GPL(evm_verifyxattr); | |
241 | ||
7102ebcd MZ |
242 | /* |
243 | * evm_verify_current_integrity - verify the dentry's metadata integrity | |
244 | * @dentry: pointer to the affected dentry | |
245 | * | |
246 | * Verify and return the dentry's metadata integrity. The exceptions are | |
247 | * before EVM is initialized or in 'fix' mode. | |
248 | */ | |
249 | static enum integrity_status evm_verify_current_integrity(struct dentry *dentry) | |
250 | { | |
251 | struct inode *inode = dentry->d_inode; | |
252 | ||
253 | if (!evm_initialized || !S_ISREG(inode->i_mode) || evm_fixmode) | |
254 | return 0; | |
255 | return evm_verify_hmac(dentry, NULL, NULL, 0, NULL); | |
256 | } | |
257 | ||
a924ce0b MZ |
258 | /* |
259 | * evm_protect_xattr - protect the EVM extended attribute | |
260 | * | |
bf6d0f5d MZ |
261 | * Prevent security.evm from being modified or removed without the |
262 | * necessary permissions or when the existing value is invalid. | |
263 | * | |
264 | * The posix xattr acls are 'system' prefixed, which normally would not | |
265 | * affect security.evm. An interesting side affect of writing posix xattr | |
266 | * acls is their modifying of the i_mode, which is included in security.evm. | |
267 | * For posix xattr acls only, permit security.evm, even if it currently | |
268 | * doesn't exist, to be updated. | |
a924ce0b MZ |
269 | */ |
270 | static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name, | |
271 | const void *xattr_value, size_t xattr_value_len) | |
272 | { | |
273 | enum integrity_status evm_status; | |
274 | ||
275 | if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { | |
276 | if (!capable(CAP_SYS_ADMIN)) | |
277 | return -EPERM; | |
bf6d0f5d MZ |
278 | } else if (!evm_protected_xattr(xattr_name)) { |
279 | if (!posix_xattr_acl(xattr_name)) | |
280 | return 0; | |
281 | evm_status = evm_verify_current_integrity(dentry); | |
282 | if ((evm_status == INTEGRITY_PASS) || | |
566be59a | 283 | (evm_status == INTEGRITY_NOXATTRS)) |
bf6d0f5d | 284 | return 0; |
9b97b6cd | 285 | goto out; |
bf6d0f5d | 286 | } |
a924ce0b | 287 | evm_status = evm_verify_current_integrity(dentry); |
3dcbad52 DK |
288 | if (evm_status == INTEGRITY_NOXATTRS) { |
289 | struct integrity_iint_cache *iint; | |
290 | ||
291 | iint = integrity_iint_find(dentry->d_inode); | |
292 | if (iint && (iint->flags & IMA_NEW_FILE)) | |
293 | return 0; | |
294 | } | |
9b97b6cd MZ |
295 | out: |
296 | if (evm_status != INTEGRITY_PASS) | |
297 | integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode, | |
298 | dentry->d_name.name, "appraise_metadata", | |
299 | integrity_status_msg[evm_status], | |
300 | -EPERM, 0); | |
a924ce0b MZ |
301 | return evm_status == INTEGRITY_PASS ? 0 : -EPERM; |
302 | } | |
303 | ||
66dbc325 MZ |
304 | /** |
305 | * evm_inode_setxattr - protect the EVM extended attribute | |
306 | * @dentry: pointer to the affected dentry | |
307 | * @xattr_name: pointer to the affected extended attribute name | |
308 | * @xattr_value: pointer to the new extended attribute value | |
309 | * @xattr_value_len: pointer to the new extended attribute value length | |
310 | * | |
2fb1c9a4 MZ |
311 | * Before allowing the 'security.evm' protected xattr to be updated, |
312 | * verify the existing value is valid. As only the kernel should have | |
313 | * access to the EVM encrypted key needed to calculate the HMAC, prevent | |
314 | * userspace from writing HMAC value. Writing 'security.evm' requires | |
315 | * requires CAP_SYS_ADMIN privileges. | |
66dbc325 MZ |
316 | */ |
317 | int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name, | |
318 | const void *xattr_value, size_t xattr_value_len) | |
319 | { | |
2fb1c9a4 MZ |
320 | const struct evm_ima_xattr_data *xattr_data = xattr_value; |
321 | ||
3b1deef6 DK |
322 | if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { |
323 | if (!xattr_value_len) | |
324 | return -EINVAL; | |
325 | if (xattr_data->type != EVM_IMA_XATTR_DIGSIG) | |
326 | return -EPERM; | |
327 | } | |
a924ce0b MZ |
328 | return evm_protect_xattr(dentry, xattr_name, xattr_value, |
329 | xattr_value_len); | |
66dbc325 MZ |
330 | } |
331 | ||
332 | /** | |
333 | * evm_inode_removexattr - protect the EVM extended attribute | |
334 | * @dentry: pointer to the affected dentry | |
335 | * @xattr_name: pointer to the affected extended attribute name | |
336 | * | |
7102ebcd MZ |
337 | * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that |
338 | * the current value is valid. | |
66dbc325 MZ |
339 | */ |
340 | int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name) | |
341 | { | |
a924ce0b | 342 | return evm_protect_xattr(dentry, xattr_name, NULL, 0); |
66dbc325 MZ |
343 | } |
344 | ||
345 | /** | |
346 | * evm_inode_post_setxattr - update 'security.evm' to reflect the changes | |
347 | * @dentry: pointer to the affected dentry | |
348 | * @xattr_name: pointer to the affected extended attribute name | |
349 | * @xattr_value: pointer to the new extended attribute value | |
350 | * @xattr_value_len: pointer to the new extended attribute value length | |
351 | * | |
352 | * Update the HMAC stored in 'security.evm' to reflect the change. | |
353 | * | |
354 | * No need to take the i_mutex lock here, as this function is called from | |
355 | * __vfs_setxattr_noperm(). The caller of which has taken the inode's | |
356 | * i_mutex lock. | |
357 | */ | |
358 | void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, | |
359 | const void *xattr_value, size_t xattr_value_len) | |
360 | { | |
bf6d0f5d MZ |
361 | if (!evm_initialized || (!evm_protected_xattr(xattr_name) |
362 | && !posix_xattr_acl(xattr_name))) | |
66dbc325 MZ |
363 | return; |
364 | ||
365 | evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len); | |
66dbc325 MZ |
366 | } |
367 | ||
368 | /** | |
369 | * evm_inode_post_removexattr - update 'security.evm' after removing the xattr | |
370 | * @dentry: pointer to the affected dentry | |
371 | * @xattr_name: pointer to the affected extended attribute name | |
372 | * | |
373 | * Update the HMAC stored in 'security.evm' to reflect removal of the xattr. | |
374 | */ | |
375 | void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) | |
376 | { | |
377 | struct inode *inode = dentry->d_inode; | |
378 | ||
379 | if (!evm_initialized || !evm_protected_xattr(xattr_name)) | |
380 | return; | |
381 | ||
382 | mutex_lock(&inode->i_mutex); | |
383 | evm_update_evmxattr(dentry, xattr_name, NULL, 0); | |
384 | mutex_unlock(&inode->i_mutex); | |
66dbc325 MZ |
385 | } |
386 | ||
817b54aa MZ |
387 | /** |
388 | * evm_inode_setattr - prevent updating an invalid EVM extended attribute | |
389 | * @dentry: pointer to the affected dentry | |
390 | */ | |
391 | int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) | |
392 | { | |
393 | unsigned int ia_valid = attr->ia_valid; | |
394 | enum integrity_status evm_status; | |
395 | ||
a924ce0b | 396 | if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))) |
817b54aa MZ |
397 | return 0; |
398 | evm_status = evm_verify_current_integrity(dentry); | |
566be59a MZ |
399 | if ((evm_status == INTEGRITY_PASS) || |
400 | (evm_status == INTEGRITY_NOXATTRS)) | |
401 | return 0; | |
9b97b6cd MZ |
402 | integrity_audit_msg(AUDIT_INTEGRITY_METADATA, dentry->d_inode, |
403 | dentry->d_name.name, "appraise_metadata", | |
404 | integrity_status_msg[evm_status], -EPERM, 0); | |
566be59a | 405 | return -EPERM; |
817b54aa MZ |
406 | } |
407 | ||
66dbc325 MZ |
408 | /** |
409 | * evm_inode_post_setattr - update 'security.evm' after modifying metadata | |
410 | * @dentry: pointer to the affected dentry | |
411 | * @ia_valid: for the UID and GID status | |
412 | * | |
413 | * For now, update the HMAC stored in 'security.evm' to reflect UID/GID | |
414 | * changes. | |
415 | * | |
416 | * This function is called from notify_change(), which expects the caller | |
417 | * to lock the inode's i_mutex. | |
418 | */ | |
419 | void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) | |
420 | { | |
421 | if (!evm_initialized) | |
422 | return; | |
423 | ||
424 | if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) | |
425 | evm_update_evmxattr(dentry, NULL, NULL, 0); | |
66dbc325 MZ |
426 | } |
427 | ||
cb723180 MZ |
428 | /* |
429 | * evm_inode_init_security - initializes security.evm | |
430 | */ | |
431 | int evm_inode_init_security(struct inode *inode, | |
432 | const struct xattr *lsm_xattr, | |
433 | struct xattr *evm_xattr) | |
434 | { | |
435 | struct evm_ima_xattr_data *xattr_data; | |
436 | int rc; | |
437 | ||
438 | if (!evm_initialized || !evm_protected_xattr(lsm_xattr->name)) | |
5a4730ba | 439 | return 0; |
cb723180 MZ |
440 | |
441 | xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); | |
442 | if (!xattr_data) | |
443 | return -ENOMEM; | |
444 | ||
445 | xattr_data->type = EVM_XATTR_HMAC; | |
446 | rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest); | |
447 | if (rc < 0) | |
448 | goto out; | |
449 | ||
450 | evm_xattr->value = xattr_data; | |
451 | evm_xattr->value_len = sizeof(*xattr_data); | |
9548906b | 452 | evm_xattr->name = XATTR_EVM_SUFFIX; |
cb723180 MZ |
453 | return 0; |
454 | out: | |
455 | kfree(xattr_data); | |
456 | return rc; | |
457 | } | |
458 | EXPORT_SYMBOL_GPL(evm_inode_init_security); | |
459 | ||
66dbc325 MZ |
460 | static int __init init_evm(void) |
461 | { | |
462 | int error; | |
463 | ||
d3b33679 DK |
464 | evm_init_config(); |
465 | ||
66dbc325 MZ |
466 | error = evm_init_secfs(); |
467 | if (error < 0) { | |
20ee451f | 468 | pr_info("Error registering secfs\n"); |
66dbc325 MZ |
469 | goto err; |
470 | } | |
15647eb3 DK |
471 | |
472 | return 0; | |
66dbc325 MZ |
473 | err: |
474 | return error; | |
475 | } | |
476 | ||
66dbc325 MZ |
477 | /* |
478 | * evm_display_config - list the EVM protected security extended attributes | |
479 | */ | |
480 | static int __init evm_display_config(void) | |
481 | { | |
482 | char **xattrname; | |
483 | ||
484 | for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) | |
20ee451f | 485 | pr_info("%s\n", *xattrname); |
66dbc325 MZ |
486 | return 0; |
487 | } | |
488 | ||
489 | pure_initcall(evm_display_config); | |
490 | late_initcall(init_evm); | |
491 | ||
492 | MODULE_DESCRIPTION("Extended Verification Module"); | |
493 | MODULE_LICENSE("GPL"); |