1 /*
2 * Integrity Measurement Architecture
3 *
4 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
5 *
6 * Authors:
7 * Reiner Sailer <sailer@watson.ibm.com>
8 * Serge Hallyn <serue@us.ibm.com>
9 * Kylene Hall <kylene@us.ibm.com>
10 * Mimi Zohar <zohar@us.ibm.com>
11 *
12 * This program is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU General Public License as
14 * published by the Free Software Foundation, version 2 of the
15 * License.
16 *
17 * File: ima_main.c
18 * implements the IMA hooks: ima_bprm_check, ima_file_mmap,
19 * and ima_file_check.
20 */
21
22 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
23
24 #include <linux/module.h>
25 #include <linux/file.h>
26 #include <linux/binfmts.h>
27 #include <linux/mount.h>
28 #include <linux/mman.h>
29 #include <linux/slab.h>
30 #include <linux/xattr.h>
31 #include <linux/ima.h>
32 #include <linux/iversion.h>
33 #include <linux/fs.h>
34
35 #include "ima.h"
36
37 #ifdef CONFIG_IMA_APPRAISE
38 int ima_appraise = IMA_APPRAISE_ENFORCE;
39 #else
40 int ima_appraise;
41 #endif
42
43 int ima_hash_algo = HASH_ALGO_SHA1;
44 static int hash_setup_done;
45
46 static int __init hash_setup(char *str)
47 {
48 struct ima_template_desc *template_desc = ima_template_desc_current();
49 int i;
50
51 if (hash_setup_done)
52 return 1;
53
54 if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
55 if (strncmp(str, "sha1", 4) == 0)
56 ima_hash_algo = HASH_ALGO_SHA1;
57 else if (strncmp(str, "md5", 3) == 0)
58 ima_hash_algo = HASH_ALGO_MD5;
59 else
60 return 1;
61 goto out;
62 }
63
64 i = match_string(hash_algo_name, HASH_ALGO__LAST, str);
65 if (i < 0)
66 return 1;
67
68 ima_hash_algo = i;
69 out:
70 hash_setup_done = 1;
71 return 1;
72 }
73 __setup("ima_hash=", hash_setup);
74
75 /*
76 * ima_rdwr_violation_check
77 *
78 * Only invalidate the PCR for measured files:
79 * - Opening a file for write when already open for read,
80 * results in a time of measure, time of use (ToMToU) error.
81 * - Opening a file for read when already open for write,
82 * could result in a file measurement error.
83 *
84 */
85 static void ima_rdwr_violation_check(struct file *file,
86 struct integrity_iint_cache *iint,
87 int must_measure,
88 char **pathbuf,
89 const char **pathname,
90 char *filename)
91 {
92 struct inode *inode = file_inode(file);
93 fmode_t mode = file->f_mode;
94 bool send_tomtou = false, send_writers = false;
95
96 if (mode & FMODE_WRITE) {
97 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
98 if (!iint)
99 iint = integrity_iint_find(inode);
100 /* IMA_MEASURE is set from reader side */
101 if (iint && test_bit(IMA_MUST_MEASURE,
102 &iint->atomic_flags))
103 send_tomtou = true;
104 }
105 } else {
106 if (must_measure)
107 set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
108 if (inode_is_open_for_write(inode) && must_measure)
109 send_writers = true;
110 }
111
112 if (!send_tomtou && !send_writers)
113 return;
114
115 *pathname = ima_d_path(&file->f_path, pathbuf, filename);
116
117 if (send_tomtou)
118 ima_add_violation(file, *pathname, iint,
119 "invalid_pcr", "ToMToU");
120 if (send_writers)
121 ima_add_violation(file, *pathname, iint,
122 "invalid_pcr", "open_writers");
123 }
124
125 static void ima_check_last_writer(struct integrity_iint_cache *iint,
126 struct inode *inode, struct file *file)
127 {
128 fmode_t mode = file->f_mode;
129 bool update;
130
131 if (!(mode & FMODE_WRITE))
132 return;
133
134 mutex_lock(&iint->mutex);
135 if (atomic_read(&inode->i_writecount) == 1) {
136 update = test_and_clear_bit(IMA_UPDATE_XATTR,
137 &iint->atomic_flags);
138 if (!IS_I_VERSION(inode) ||
139 !inode_eq_iversion(inode, iint->version) ||
140 (iint->flags & IMA_NEW_FILE)) {
141 iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
142 iint->measured_pcrs = 0;
143 if (update)
144 ima_update_xattr(iint, file);
145 }
146 }
147 mutex_unlock(&iint->mutex);
148 }
149
150 /**
151 * ima_file_free - called on __fput()
152 * @file: pointer to file structure being freed
153 *
154 * Flag files that changed, based on i_version
155 */
156 void ima_file_free(struct file *file)
157 {
158 struct inode *inode = file_inode(file);
159 struct integrity_iint_cache *iint;
160
161 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
162 return;
163
164 iint = integrity_iint_find(inode);
165 if (!iint)
166 return;
167
168 ima_check_last_writer(iint, inode, file);
169 }
170
171 static int process_measurement(struct file *file, const struct cred *cred,
172 u32 secid, char *buf, loff_t size, int mask,
173 enum ima_hooks func)
174 {
175 struct inode *inode = file_inode(file);
176 struct integrity_iint_cache *iint = NULL;
177 struct ima_template_desc *template_desc;
178 char *pathbuf = NULL;
179 char filename[NAME_MAX];
180 const char *pathname = NULL;
181 int rc = 0, action, must_appraise = 0;
182 int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
183 struct evm_ima_xattr_data *xattr_value = NULL;
184 int xattr_len = 0;
185 bool violation_check;
186 enum hash_algo hash_algo;
187
188 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
189 return 0;
190
191 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
192 * bitmask based on the appraise/audit/measurement policy.
193 * Included is the appraise submask.
194 */
195 action = ima_get_action(inode, cred, secid, mask, func, &pcr);
196 violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
197 (ima_policy_flag & IMA_MEASURE));
198 if (!action && !violation_check)
199 return 0;
200
201 must_appraise = action & IMA_APPRAISE;
202
203 /* Is the appraise rule hook specific? */
204 if (action & IMA_FILE_APPRAISE)
205 func = FILE_CHECK;
206
207 inode_lock(inode);
208
209 if (action) {
210 iint = integrity_inode_get(inode);
211 if (!iint)
212 rc = -ENOMEM;
213 }
214
215 if (!rc && violation_check)
216 ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
217 &pathbuf, &pathname, filename);
218
219 inode_unlock(inode);
220
221 if (rc)
222 goto out;
223 if (!action)
224 goto out;
225
226 mutex_lock(&iint->mutex);
227
228 if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
229 /* reset appraisal flags if ima_inode_post_setattr was called */
230 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
231 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
232 IMA_ACTION_FLAGS);
233
234 /*
235 * Re-evaulate the file if either the xattr has changed or the
236 * kernel has no way of detecting file change on the filesystem.
237 * (Limited to privileged mounted filesystems.)
238 */
239 if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) ||
240 ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
241 !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
242 !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
243 iint->flags &= ~IMA_DONE_MASK;
244 iint->measured_pcrs = 0;
245 }
246
247 /* Determine if already appraised/measured based on bitmask
248 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
249 * IMA_AUDIT, IMA_AUDITED)
250 */
251 iint->flags |= action;
252 action &= IMA_DO_MASK;
253 action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
254
255 /* If target pcr is already measured, unset IMA_MEASURE action */
256 if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
257 action ^= IMA_MEASURE;
258
259 /* HASH sets the digital signature and update flags, nothing else */
260 if ((action & IMA_HASH) &&
261 !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) {
262 xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
263 if ((xattr_value && xattr_len > 2) &&
264 (xattr_value->type == EVM_IMA_XATTR_DIGSIG))
265 set_bit(IMA_DIGSIG, &iint->atomic_flags);
266 iint->flags |= IMA_HASHED;
267 action ^= IMA_HASH;
268 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
269 }
270
271 /* Nothing to do, just return existing appraised status */
272 if (!action) {
273 if (must_appraise)
274 rc = ima_get_cache_status(iint, func);
275 goto out_locked;
276 }
277
278 template_desc = ima_template_desc_current();
279 if ((action & IMA_APPRAISE_SUBMASK) ||
280 strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
281 /* read 'security.ima' */
282 xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
283
284 hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
285
286 rc = ima_collect_measurement(iint, file, buf, size, hash_algo);
287 if (rc != 0 && rc != -EBADF && rc != -EINVAL)
288 goto out_locked;
289
290 if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
291 pathname = ima_d_path(&file->f_path, &pathbuf, filename);
292
293 if (action & IMA_MEASURE)
294 ima_store_measurement(iint, file, pathname,
295 xattr_value, xattr_len, pcr);
296 if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
297 inode_lock(inode);
298 rc = ima_appraise_measurement(func, iint, file, pathname,
299 xattr_value, xattr_len);
300 inode_unlock(inode);
301 }
302 if (action & IMA_AUDIT)
303 ima_audit_measurement(iint, pathname);
304
305 if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
306 rc = 0;
307 out_locked:
308 if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
309 !(iint->flags & IMA_NEW_FILE))
310 rc = -EACCES;
311 mutex_unlock(&iint->mutex);
312 kfree(xattr_value);
313 out:
314 if (pathbuf)
315 __putname(pathbuf);
316 if (must_appraise) {
317 if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
318 return -EACCES;
319 if (file->f_mode & FMODE_WRITE)
320 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
321 }
322 return 0;
323 }
324
325 /**
326 * ima_file_mmap - based on policy, collect/store measurement.
327 * @file: pointer to the file to be measured (May be NULL)
328 * @prot: contains the protection that will be applied by the kernel.
329 *
330 * Measure files being mmapped executable based on the ima_must_measure()
331 * policy decision.
332 *
333 * On success return 0. On integrity appraisal error, assuming the file
334 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
335 */
336 int ima_file_mmap(struct file *file, unsigned long prot)
337 {
338 u32 secid;
339
340 if (file && (prot & PROT_EXEC)) {
341 security_task_getsecid(current, &secid);
342 return process_measurement(file, current_cred(), secid, NULL,
343 0, MAY_EXEC, MMAP_CHECK);
344 }
345
346 return 0;
347 }
348
349 /**
350 * ima_bprm_check - based on policy, collect/store measurement.
351 * @bprm: contains the linux_binprm structure
352 *
353 * The OS protects against an executable file, already open for write,
354 * from being executed in deny_write_access() and an executable file,
355 * already open for execute, from being modified in get_write_access().
356 * So we can be certain that what we verify and measure here is actually
357 * what is being executed.
358 *
359 * On success return 0. On integrity appraisal error, assuming the file
360 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
361 */
362 int ima_bprm_check(struct linux_binprm *bprm)
363 {
364 int ret;
365 u32 secid;
366
367 security_task_getsecid(current, &secid);
368 ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
369 MAY_EXEC, BPRM_CHECK);
370 if (ret)
371 return ret;
372
373 security_cred_getsecid(bprm->cred, &secid);
374 return process_measurement(bprm->file, bprm->cred, secid, NULL, 0,
375 MAY_EXEC, CREDS_CHECK);
376 }
377
378 /**
379 * ima_path_check - based on policy, collect/store measurement.
380 * @file: pointer to the file to be measured
381 * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND
382 *
383 * Measure files based on the ima_must_measure() policy decision.
384 *
385 * On success return 0. On integrity appraisal error, assuming the file
386 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
387 */
388 int ima_file_check(struct file *file, int mask)
389 {
390 u32 secid;
391
392 security_task_getsecid(current, &secid);
393 return process_measurement(file, current_cred(), secid, NULL, 0,
394 mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
395 MAY_APPEND), FILE_CHECK);
396 }
397 EXPORT_SYMBOL_GPL(ima_file_check);
398
399 /**
400 * ima_post_create_tmpfile - mark newly created tmpfile as new
401 * @file : newly created tmpfile
402 *
403 * No measuring, appraising or auditing of newly created tmpfiles is needed.
404 * Skip calling process_measurement(), but indicate which newly, created
405 * tmpfiles are in policy.
406 */
407 void ima_post_create_tmpfile(struct inode *inode)
408 {
409 struct integrity_iint_cache *iint;
410 int must_appraise;
411
412 must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
413 if (!must_appraise)
414 return;
415
416 /* Nothing to do if we can't allocate memory */
417 iint = integrity_inode_get(inode);
418 if (!iint)
419 return;
420
421 /* needed for writing the security xattrs */
422 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
423 iint->ima_file_status = INTEGRITY_PASS;
424 }
425
426 /**
427 * ima_post_path_mknod - mark as a new inode
428 * @dentry: newly created dentry
429 *
430 * Mark files created via the mknodat syscall as new, so that the
431 * file data can be written later.
432 */
433 void ima_post_path_mknod(struct dentry *dentry)
434 {
435 struct integrity_iint_cache *iint;
436 struct inode *inode = dentry->d_inode;
437 int must_appraise;
438
439 must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK);
440 if (!must_appraise)
441 return;
442
443 /* Nothing to do if we can't allocate memory */
444 iint = integrity_inode_get(inode);
445 if (!iint)
446 return;
447
448 /* needed for re-opening empty files */
449 iint->flags |= IMA_NEW_FILE;
450 }
451
452 /**
453 * ima_read_file - pre-measure/appraise hook decision based on policy
454 * @file: pointer to the file to be measured/appraised/audit
455 * @read_id: caller identifier
456 *
457 * Permit reading a file based on policy. The policy rules are written
458 * in terms of the policy identifier. Appraising the integrity of
459 * a file requires a file descriptor.
460 *
461 * For permission return 0, otherwise return -EACCES.
462 */
463 int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
464 {
465 /*
466 * READING_FIRMWARE_PREALLOC_BUFFER
467 *
468 * Do devices using pre-allocated memory run the risk of the
469 * firmware being accessible to the device prior to the completion
470 * of IMA's signature verification any more than when using two
471 * buffers?
472 */
473 return 0;
474 }
475
476 static const int read_idmap[READING_MAX_ID] = {
477 [READING_FIRMWARE] = FIRMWARE_CHECK,
478 [READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK,
479 [READING_MODULE] = MODULE_CHECK,
480 [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
481 [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
482 [READING_POLICY] = POLICY_CHECK
483 };
484
485 /**
486 * ima_post_read_file - in memory collect/appraise/audit measurement
487 * @file: pointer to the file to be measured/appraised/audit
488 * @buf: pointer to in memory file contents
489 * @size: size of in memory file contents
490 * @read_id: caller identifier
491 *
492 * Measure/appraise/audit in memory file based on policy. Policy rules
493 * are written in terms of a policy identifier.
494 *
495 * On success return 0. On integrity appraisal error, assuming the file
496 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
497 */
498 int ima_post_read_file(struct file *file, void *buf, loff_t size,
499 enum kernel_read_file_id read_id)
500 {
501 enum ima_hooks func;
502 u32 secid;
503
504 if (!file && read_id == READING_FIRMWARE) {
505 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
506 (ima_appraise & IMA_APPRAISE_ENFORCE)) {
507 pr_err("Prevent firmware loading_store.\n");
508 return -EACCES; /* INTEGRITY_UNKNOWN */
509 }
510 return 0;
511 }
512
513 /* permit signed certs */
514 if (!file && read_id == READING_X509_CERTIFICATE)
515 return 0;
516
517 if (!file || !buf || size == 0) { /* should never happen */
518 if (ima_appraise & IMA_APPRAISE_ENFORCE)
519 return -EACCES;
520 return 0;
521 }
522
523 func = read_idmap[read_id] ?: FILE_CHECK;
524 security_task_getsecid(current, &secid);
525 return process_measurement(file, current_cred(), secid, buf, size,
526 MAY_READ, func);
527 }
528
529 /**
530 * ima_load_data - appraise decision based on policy
531 * @id: kernel load data caller identifier
532 *
533 * Callers of this LSM hook can not measure, appraise, or audit the
534 * data provided by userspace. Enforce policy rules requring a file
535 * signature (eg. kexec'ed kernel image).
536 *
537 * For permission return 0, otherwise return -EACCES.
538 */
539 int ima_load_data(enum kernel_load_data_id id)
540 {
541 bool ima_enforce, sig_enforce;
542
543 ima_enforce =
544 (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
545
546 switch (id) {
547 case LOADING_KEXEC_IMAGE:
548 if (IS_ENABLED(CONFIG_KEXEC_VERIFY_SIG)
549 && arch_ima_get_secureboot()) {
550 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
551 return -EACCES;
552 }
553
554 if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
555 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
556 return -EACCES; /* INTEGRITY_UNKNOWN */
557 }
558 break;
559 case LOADING_FIRMWARE:
560 if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE)) {
561 pr_err("Prevent firmware sysfs fallback loading.\n");
562 return -EACCES; /* INTEGRITY_UNKNOWN */
563 }
564 break;
565 case LOADING_MODULE:
566 sig_enforce = is_module_sig_enforced();
567
568 if (ima_enforce && (!sig_enforce
569 && (ima_appraise & IMA_APPRAISE_MODULES))) {
570 pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
571 return -EACCES; /* INTEGRITY_UNKNOWN */
572 }
573 default:
574 break;
575 }
576 return 0;
577 }
578
579 static int __init init_ima(void)
580 {
581 int error;
582
583 ima_init_template_list();
584 hash_setup(CONFIG_IMA_DEFAULT_HASH);
585 error = ima_init();
586
587 if (error && strcmp(hash_algo_name[ima_hash_algo],
588 CONFIG_IMA_DEFAULT_HASH) != 0) {
589 pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
590 hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
591 hash_setup_done = 0;
592 hash_setup(CONFIG_IMA_DEFAULT_HASH);
593 error = ima_init();
594 }
595
596 if (!error)
597 ima_update_policy_flag();
598
599 return error;
600 }
601
602 late_initcall(init_ima); /* Start IMA after the TPM is available */
603
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