1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Integrity Measurement Architecture
4 *
5 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
6 *
7 * Authors:
8 * Reiner Sailer <sailer@watson.ibm.com>
9 * Serge Hallyn <serue@us.ibm.com>
10 * Kylene Hall <kylene@us.ibm.com>
11 * Mimi Zohar <zohar@us.ibm.com>
12 *
13 * File: ima_main.c
14 * implements the IMA hooks: ima_bprm_check, ima_file_mmap,
15 * and ima_file_check.
16 */
17
18 #include <linux/module.h>
19 #include <linux/file.h>
20 #include <linux/binfmts.h>
21 #include <linux/kernel_read_file.h>
22 #include <linux/mount.h>
23 #include <linux/mman.h>
24 #include <linux/slab.h>
25 #include <linux/xattr.h>
26 #include <linux/ima.h>
27 #include <linux/fs.h>
28 #include <linux/iversion.h>
29 #include <linux/evm.h>
30
31 #include "ima.h"
32
33 #ifdef CONFIG_IMA_APPRAISE
34 int ima_appraise = IMA_APPRAISE_ENFORCE;
35 #else
36 int ima_appraise;
37 #endif
38
39 int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1;
40 static int hash_setup_done;
41
42 static struct notifier_block ima_lsm_policy_notifier = {
43 .notifier_call = ima_lsm_policy_change,
44 };
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 pr_err("invalid hash algorithm \"%s\" for template \"%s\"",
61 str, IMA_TEMPLATE_IMA_NAME);
62 return 1;
63 }
64 goto out;
65 }
66
67 i = match_string(hash_algo_name, HASH_ALGO__LAST, str);
68 if (i < 0) {
69 pr_err("invalid hash algorithm \"%s\"", str);
70 return 1;
71 }
72
73 ima_hash_algo = i;
74 out:
75 hash_setup_done = 1;
76 return 1;
77 }
78 __setup("ima_hash=", hash_setup);
79
80 enum hash_algo ima_get_current_hash_algo(void)
81 {
82 return ima_hash_algo;
83 }
84
85 /* Prevent mmap'ing a file execute that is already mmap'ed write */
86 static int mmap_violation_check(enum ima_hooks func, struct file *file,
87 char **pathbuf, const char **pathname,
88 char *filename)
89 {
90 struct inode *inode;
91 int rc = 0;
92
93 if ((func == MMAP_CHECK || func == MMAP_CHECK_REQPROT) &&
94 mapping_writably_mapped(file->f_mapping)) {
95 rc = -ETXTBSY;
96 inode = file_inode(file);
97
98 if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */
99 *pathname = ima_d_path(&file->f_path, pathbuf,
100 filename);
101 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname,
102 "mmap_file", "mmapped_writers", rc, 0);
103 }
104 return rc;
105 }
106
107 /*
108 * ima_rdwr_violation_check
109 *
110 * Only invalidate the PCR for measured files:
111 * - Opening a file for write when already open for read,
112 * results in a time of measure, time of use (ToMToU) error.
113 * - Opening a file for read when already open for write,
114 * could result in a file measurement error.
115 *
116 */
117 static void ima_rdwr_violation_check(struct file *file,
118 struct ima_iint_cache *iint,
119 int must_measure,
120 char **pathbuf,
121 const char **pathname,
122 char *filename)
123 {
124 struct inode *inode = file_inode(file);
125 fmode_t mode = file->f_mode;
126 bool send_tomtou = false, send_writers = false;
127
128 if (mode & FMODE_WRITE) {
129 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
130 if (!iint)
131 iint = ima_iint_find(inode);
132 /* IMA_MEASURE is set from reader side */
133 if (iint && test_bit(IMA_MUST_MEASURE,
134 &iint->atomic_flags))
135 send_tomtou = true;
136 }
137 } else {
138 if (must_measure)
139 set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
140 if (inode_is_open_for_write(inode) && must_measure)
141 send_writers = true;
142 }
143
144 if (!send_tomtou && !send_writers)
145 return;
146
147 *pathname = ima_d_path(&file->f_path, pathbuf, filename);
148
149 if (send_tomtou)
150 ima_add_violation(file, *pathname, iint,
151 "invalid_pcr", "ToMToU");
152 if (send_writers)
153 ima_add_violation(file, *pathname, iint,
154 "invalid_pcr", "open_writers");
155 }
156
157 static void ima_check_last_writer(struct ima_iint_cache *iint,
158 struct inode *inode, struct file *file)
159 {
160 fmode_t mode = file->f_mode;
161 bool update;
162
163 if (!(mode & FMODE_WRITE))
164 return;
165
166 mutex_lock(&iint->mutex);
167 if (atomic_read(&inode->i_writecount) == 1) {
168 struct kstat stat;
169
170 update = test_and_clear_bit(IMA_UPDATE_XATTR,
171 &iint->atomic_flags);
172 if ((iint->flags & IMA_NEW_FILE) ||
173 vfs_getattr_nosec(&file->f_path, &stat,
174 STATX_CHANGE_COOKIE,
175 AT_STATX_SYNC_AS_STAT) ||
176 !(stat.result_mask & STATX_CHANGE_COOKIE) ||
177 stat.change_cookie != iint->real_inode.version) {
178 iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
179 iint->measured_pcrs = 0;
180 if (update)
181 ima_update_xattr(iint, file);
182 }
183 }
184 mutex_unlock(&iint->mutex);
185 }
186
187 /**
188 * ima_file_free - called on __fput()
189 * @file: pointer to file structure being freed
190 *
191 * Flag files that changed, based on i_version
192 */
193 static void ima_file_free(struct file *file)
194 {
195 struct inode *inode = file_inode(file);
196 struct ima_iint_cache *iint;
197
198 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
199 return;
200
201 iint = ima_iint_find(inode);
202 if (!iint)
203 return;
204
205 ima_check_last_writer(iint, inode, file);
206 }
207
208 static int process_measurement(struct file *file, const struct cred *cred,
209 u32 secid, char *buf, loff_t size, int mask,
210 enum ima_hooks func)
211 {
212 struct inode *real_inode, *inode = file_inode(file);
213 struct ima_iint_cache *iint = NULL;
214 struct ima_template_desc *template_desc = NULL;
215 struct inode *metadata_inode;
216 char *pathbuf = NULL;
217 char filename[NAME_MAX];
218 const char *pathname = NULL;
219 int rc = 0, action, must_appraise = 0;
220 int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
221 struct evm_ima_xattr_data *xattr_value = NULL;
222 struct modsig *modsig = NULL;
223 int xattr_len = 0;
224 bool violation_check;
225 enum hash_algo hash_algo;
226 unsigned int allowed_algos = 0;
227
228 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
229 return 0;
230
231 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
232 * bitmask based on the appraise/audit/measurement policy.
233 * Included is the appraise submask.
234 */
235 action = ima_get_action(file_mnt_idmap(file), inode, cred, secid,
236 mask, func, &pcr, &template_desc, NULL,
237 &allowed_algos);
238 violation_check = ((func == FILE_CHECK || func == MMAP_CHECK ||
239 func == MMAP_CHECK_REQPROT) &&
240 (ima_policy_flag & IMA_MEASURE));
241 if (!action && !violation_check)
242 return 0;
243
244 must_appraise = action & IMA_APPRAISE;
245
246 /* Is the appraise rule hook specific? */
247 if (action & IMA_FILE_APPRAISE)
248 func = FILE_CHECK;
249
250 inode_lock(inode);
251
252 if (action) {
253 iint = ima_inode_get(inode);
254 if (!iint)
255 rc = -ENOMEM;
256 }
257
258 if (!rc && violation_check)
259 ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
260 &pathbuf, &pathname, filename);
261
262 inode_unlock(inode);
263
264 if (rc)
265 goto out;
266 if (!action)
267 goto out;
268
269 mutex_lock(&iint->mutex);
270
271 if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
272 /* reset appraisal flags if ima_inode_post_setattr was called */
273 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
274 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
275 IMA_NONACTION_FLAGS);
276
277 /*
278 * Re-evaulate the file if either the xattr has changed or the
279 * kernel has no way of detecting file change on the filesystem.
280 * (Limited to privileged mounted filesystems.)
281 */
282 if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) ||
283 ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
284 !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
285 !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
286 iint->flags &= ~IMA_DONE_MASK;
287 iint->measured_pcrs = 0;
288 }
289
290 /*
291 * On stacked filesystems, detect and re-evaluate file data and
292 * metadata changes.
293 */
294 real_inode = d_real_inode(file_dentry(file));
295 if (real_inode != inode &&
296 (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) {
297 if (!IS_I_VERSION(real_inode) ||
298 integrity_inode_attrs_changed(&iint->real_inode,
299 real_inode)) {
300 iint->flags &= ~IMA_DONE_MASK;
301 iint->measured_pcrs = 0;
302 }
303
304 /*
305 * Reset the EVM status when metadata changed.
306 */
307 metadata_inode = d_inode(d_real(file_dentry(file),
308 D_REAL_METADATA));
309 if (evm_metadata_changed(inode, metadata_inode))
310 iint->flags &= ~(IMA_APPRAISED |
311 IMA_APPRAISED_SUBMASK);
312 }
313
314 /* Determine if already appraised/measured based on bitmask
315 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
316 * IMA_AUDIT, IMA_AUDITED)
317 */
318 iint->flags |= action;
319 action &= IMA_DO_MASK;
320 action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
321
322 /* If target pcr is already measured, unset IMA_MEASURE action */
323 if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
324 action ^= IMA_MEASURE;
325
326 /* HASH sets the digital signature and update flags, nothing else */
327 if ((action & IMA_HASH) &&
328 !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) {
329 xattr_len = ima_read_xattr(file_dentry(file),
330 &xattr_value, xattr_len);
331 if ((xattr_value && xattr_len > 2) &&
332 (xattr_value->type == EVM_IMA_XATTR_DIGSIG))
333 set_bit(IMA_DIGSIG, &iint->atomic_flags);
334 iint->flags |= IMA_HASHED;
335 action ^= IMA_HASH;
336 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
337 }
338
339 /* Nothing to do, just return existing appraised status */
340 if (!action) {
341 if (must_appraise) {
342 rc = mmap_violation_check(func, file, &pathbuf,
343 &pathname, filename);
344 if (!rc)
345 rc = ima_get_cache_status(iint, func);
346 }
347 goto out_locked;
348 }
349
350 if ((action & IMA_APPRAISE_SUBMASK) ||
351 strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) {
352 /* read 'security.ima' */
353 xattr_len = ima_read_xattr(file_dentry(file),
354 &xattr_value, xattr_len);
355
356 /*
357 * Read the appended modsig if allowed by the policy, and allow
358 * an additional measurement list entry, if needed, based on the
359 * template format and whether the file was already measured.
360 */
361 if (iint->flags & IMA_MODSIG_ALLOWED) {
362 rc = ima_read_modsig(func, buf, size, &modsig);
363
364 if (!rc && ima_template_has_modsig(template_desc) &&
365 iint->flags & IMA_MEASURED)
366 action |= IMA_MEASURE;
367 }
368 }
369
370 hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
371
372 rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig);
373 if (rc != 0 && rc != -EBADF && rc != -EINVAL)
374 goto out_locked;
375
376 if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
377 pathname = ima_d_path(&file->f_path, &pathbuf, filename);
378
379 if (action & IMA_MEASURE)
380 ima_store_measurement(iint, file, pathname,
381 xattr_value, xattr_len, modsig, pcr,
382 template_desc);
383 if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
384 rc = ima_check_blacklist(iint, modsig, pcr);
385 if (rc != -EPERM) {
386 inode_lock(inode);
387 rc = ima_appraise_measurement(func, iint, file,
388 pathname, xattr_value,
389 xattr_len, modsig);
390 inode_unlock(inode);
391 }
392 if (!rc)
393 rc = mmap_violation_check(func, file, &pathbuf,
394 &pathname, filename);
395 }
396 if (action & IMA_AUDIT)
397 ima_audit_measurement(iint, pathname);
398
399 if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
400 rc = 0;
401
402 /* Ensure the digest was generated using an allowed algorithm */
403 if (rc == 0 && must_appraise && allowed_algos != 0 &&
404 (allowed_algos & (1U << hash_algo)) == 0) {
405 rc = -EACCES;
406
407 integrity_audit_msg(AUDIT_INTEGRITY_DATA, file_inode(file),
408 pathname, "collect_data",
409 "denied-hash-algorithm", rc, 0);
410 }
411 out_locked:
412 if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
413 !(iint->flags & IMA_NEW_FILE))
414 rc = -EACCES;
415 mutex_unlock(&iint->mutex);
416 kfree(xattr_value);
417 ima_free_modsig(modsig);
418 out:
419 if (pathbuf)
420 __putname(pathbuf);
421 if (must_appraise) {
422 if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
423 return -EACCES;
424 if (file->f_mode & FMODE_WRITE)
425 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
426 }
427 return 0;
428 }
429
430 /**
431 * ima_file_mmap - based on policy, collect/store measurement.
432 * @file: pointer to the file to be measured (May be NULL)
433 * @reqprot: protection requested by the application
434 * @prot: protection that will be applied by the kernel
435 * @flags: operational flags
436 *
437 * Measure files being mmapped executable based on the ima_must_measure()
438 * policy decision.
439 *
440 * On success return 0. On integrity appraisal error, assuming the file
441 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
442 */
443 static int ima_file_mmap(struct file *file, unsigned long reqprot,
444 unsigned long prot, unsigned long flags)
445 {
446 u32 secid;
447 int ret;
448
449 if (!file)
450 return 0;
451
452 security_current_getsecid_subj(&secid);
453
454 if (reqprot & PROT_EXEC) {
455 ret = process_measurement(file, current_cred(), secid, NULL,
456 0, MAY_EXEC, MMAP_CHECK_REQPROT);
457 if (ret)
458 return ret;
459 }
460
461 if (prot & PROT_EXEC)
462 return process_measurement(file, current_cred(), secid, NULL,
463 0, MAY_EXEC, MMAP_CHECK);
464
465 return 0;
466 }
467
468 /**
469 * ima_file_mprotect - based on policy, limit mprotect change
470 * @vma: vm_area_struct protection is set to
471 * @reqprot: protection requested by the application
472 * @prot: protection that will be applied by the kernel
473 *
474 * Files can be mmap'ed read/write and later changed to execute to circumvent
475 * IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore
476 * would be taken before i_mutex), files can not be measured or appraised at
477 * this point. Eliminate this integrity gap by denying the mprotect
478 * PROT_EXECUTE change, if an mmap appraise policy rule exists.
479 *
480 * On mprotect change success, return 0. On failure, return -EACESS.
481 */
482 static int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
483 unsigned long prot)
484 {
485 struct ima_template_desc *template = NULL;
486 struct file *file;
487 char filename[NAME_MAX];
488 char *pathbuf = NULL;
489 const char *pathname = NULL;
490 struct inode *inode;
491 int result = 0;
492 int action;
493 u32 secid;
494 int pcr;
495
496 /* Is mprotect making an mmap'ed file executable? */
497 if (!(ima_policy_flag & IMA_APPRAISE) || !vma->vm_file ||
498 !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC))
499 return 0;
500
501 security_current_getsecid_subj(&secid);
502 inode = file_inode(vma->vm_file);
503 action = ima_get_action(file_mnt_idmap(vma->vm_file), inode,
504 current_cred(), secid, MAY_EXEC, MMAP_CHECK,
505 &pcr, &template, NULL, NULL);
506 action |= ima_get_action(file_mnt_idmap(vma->vm_file), inode,
507 current_cred(), secid, MAY_EXEC,
508 MMAP_CHECK_REQPROT, &pcr, &template, NULL,
509 NULL);
510
511 /* Is the mmap'ed file in policy? */
512 if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))
513 return 0;
514
515 if (action & IMA_APPRAISE_SUBMASK)
516 result = -EPERM;
517
518 file = vma->vm_file;
519 pathname = ima_d_path(&file->f_path, &pathbuf, filename);
520 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, pathname,
521 "collect_data", "failed-mprotect", result, 0);
522 if (pathbuf)
523 __putname(pathbuf);
524
525 return result;
526 }
527
528 /**
529 * ima_bprm_check - based on policy, collect/store measurement.
530 * @bprm: contains the linux_binprm structure
531 *
532 * The OS protects against an executable file, already open for write,
533 * from being executed in deny_write_access() and an executable file,
534 * already open for execute, from being modified in get_write_access().
535 * So we can be certain that what we verify and measure here is actually
536 * what is being executed.
537 *
538 * On success return 0. On integrity appraisal error, assuming the file
539 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
540 */
541 static int ima_bprm_check(struct linux_binprm *bprm)
542 {
543 int ret;
544 u32 secid;
545
546 security_current_getsecid_subj(&secid);
547 ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
548 MAY_EXEC, BPRM_CHECK);
549 if (ret)
550 return ret;
551
552 security_cred_getsecid(bprm->cred, &secid);
553 return process_measurement(bprm->file, bprm->cred, secid, NULL, 0,
554 MAY_EXEC, CREDS_CHECK);
555 }
556
557 /**
558 * ima_file_check - based on policy, collect/store measurement.
559 * @file: pointer to the file to be measured
560 * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND
561 *
562 * Measure files based on the ima_must_measure() policy decision.
563 *
564 * On success return 0. On integrity appraisal error, assuming the file
565 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
566 */
567 static int ima_file_check(struct file *file, int mask)
568 {
569 u32 secid;
570
571 security_current_getsecid_subj(&secid);
572 return process_measurement(file, current_cred(), secid, NULL, 0,
573 mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
574 MAY_APPEND), FILE_CHECK);
575 }
576
577 static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
578 size_t buf_size)
579 {
580 struct ima_iint_cache *iint = NULL, tmp_iint;
581 int rc, hash_algo;
582
583 if (ima_policy_flag) {
584 iint = ima_iint_find(inode);
585 if (iint)
586 mutex_lock(&iint->mutex);
587 }
588
589 if ((!iint || !(iint->flags & IMA_COLLECTED)) && file) {
590 if (iint)
591 mutex_unlock(&iint->mutex);
592
593 memset(&tmp_iint, 0, sizeof(tmp_iint));
594 mutex_init(&tmp_iint.mutex);
595
596 rc = ima_collect_measurement(&tmp_iint, file, NULL, 0,
597 ima_hash_algo, NULL);
598 if (rc < 0) {
599 /* ima_hash could be allocated in case of failure. */
600 if (rc != -ENOMEM)
601 kfree(tmp_iint.ima_hash);
602
603 return -EOPNOTSUPP;
604 }
605
606 iint = &tmp_iint;
607 mutex_lock(&iint->mutex);
608 }
609
610 if (!iint)
611 return -EOPNOTSUPP;
612
613 /*
614 * ima_file_hash can be called when ima_collect_measurement has still
615 * not been called, we might not always have a hash.
616 */
617 if (!iint->ima_hash || !(iint->flags & IMA_COLLECTED)) {
618 mutex_unlock(&iint->mutex);
619 return -EOPNOTSUPP;
620 }
621
622 if (buf) {
623 size_t copied_size;
624
625 copied_size = min_t(size_t, iint->ima_hash->length, buf_size);
626 memcpy(buf, iint->ima_hash->digest, copied_size);
627 }
628 hash_algo = iint->ima_hash->algo;
629 mutex_unlock(&iint->mutex);
630
631 if (iint == &tmp_iint)
632 kfree(iint->ima_hash);
633
634 return hash_algo;
635 }
636
637 /**
638 * ima_file_hash - return a measurement of the file
639 * @file: pointer to the file
640 * @buf: buffer in which to store the hash
641 * @buf_size: length of the buffer
642 *
643 * On success, return the hash algorithm (as defined in the enum hash_algo).
644 * If buf is not NULL, this function also outputs the hash into buf.
645 * If the hash is larger than buf_size, then only buf_size bytes will be copied.
646 * It generally just makes sense to pass a buffer capable of holding the largest
647 * possible hash: IMA_MAX_DIGEST_SIZE.
648 * The file hash returned is based on the entire file, including the appended
649 * signature.
650 *
651 * If the measurement cannot be performed, return -EOPNOTSUPP.
652 * If the parameters are incorrect, return -EINVAL.
653 */
654 int ima_file_hash(struct file *file, char *buf, size_t buf_size)
655 {
656 if (!file)
657 return -EINVAL;
658
659 return __ima_inode_hash(file_inode(file), file, buf, buf_size);
660 }
661 EXPORT_SYMBOL_GPL(ima_file_hash);
662
663 /**
664 * ima_inode_hash - return the stored measurement if the inode has been hashed
665 * and is in the iint cache.
666 * @inode: pointer to the inode
667 * @buf: buffer in which to store the hash
668 * @buf_size: length of the buffer
669 *
670 * On success, return the hash algorithm (as defined in the enum hash_algo).
671 * If buf is not NULL, this function also outputs the hash into buf.
672 * If the hash is larger than buf_size, then only buf_size bytes will be copied.
673 * It generally just makes sense to pass a buffer capable of holding the largest
674 * possible hash: IMA_MAX_DIGEST_SIZE.
675 * The hash returned is based on the entire contents, including the appended
676 * signature.
677 *
678 * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
679 * If the parameters are incorrect, return -EINVAL.
680 */
681 int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
682 {
683 if (!inode)
684 return -EINVAL;
685
686 return __ima_inode_hash(inode, NULL, buf, buf_size);
687 }
688 EXPORT_SYMBOL_GPL(ima_inode_hash);
689
690 /**
691 * ima_post_create_tmpfile - mark newly created tmpfile as new
692 * @idmap: idmap of the mount the inode was found from
693 * @inode: inode of the newly created tmpfile
694 *
695 * No measuring, appraising or auditing of newly created tmpfiles is needed.
696 * Skip calling process_measurement(), but indicate which newly, created
697 * tmpfiles are in policy.
698 */
699 static void ima_post_create_tmpfile(struct mnt_idmap *idmap,
700 struct inode *inode)
701
702 {
703 struct ima_iint_cache *iint;
704 int must_appraise;
705
706 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
707 return;
708
709 must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS,
710 FILE_CHECK);
711 if (!must_appraise)
712 return;
713
714 /* Nothing to do if we can't allocate memory */
715 iint = ima_inode_get(inode);
716 if (!iint)
717 return;
718
719 /* needed for writing the security xattrs */
720 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
721 iint->ima_file_status = INTEGRITY_PASS;
722 }
723
724 /**
725 * ima_post_path_mknod - mark as a new inode
726 * @idmap: idmap of the mount the inode was found from
727 * @dentry: newly created dentry
728 *
729 * Mark files created via the mknodat syscall as new, so that the
730 * file data can be written later.
731 */
732 static void ima_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry)
733 {
734 struct ima_iint_cache *iint;
735 struct inode *inode = dentry->d_inode;
736 int must_appraise;
737
738 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
739 return;
740
741 must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS,
742 FILE_CHECK);
743 if (!must_appraise)
744 return;
745
746 /* Nothing to do if we can't allocate memory */
747 iint = ima_inode_get(inode);
748 if (!iint)
749 return;
750
751 /* needed for re-opening empty files */
752 iint->flags |= IMA_NEW_FILE;
753 }
754
755 /**
756 * ima_read_file - pre-measure/appraise hook decision based on policy
757 * @file: pointer to the file to be measured/appraised/audit
758 * @read_id: caller identifier
759 * @contents: whether a subsequent call will be made to ima_post_read_file()
760 *
761 * Permit reading a file based on policy. The policy rules are written
762 * in terms of the policy identifier. Appraising the integrity of
763 * a file requires a file descriptor.
764 *
765 * For permission return 0, otherwise return -EACCES.
766 */
767 static int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
768 bool contents)
769 {
770 enum ima_hooks func;
771 u32 secid;
772
773 /*
774 * Do devices using pre-allocated memory run the risk of the
775 * firmware being accessible to the device prior to the completion
776 * of IMA's signature verification any more than when using two
777 * buffers? It may be desirable to include the buffer address
778 * in this API and walk all the dma_map_single() mappings to check.
779 */
780
781 /*
782 * There will be a call made to ima_post_read_file() with
783 * a filled buffer, so we don't need to perform an extra
784 * read early here.
785 */
786 if (contents)
787 return 0;
788
789 /* Read entire file for all partial reads. */
790 func = read_idmap[read_id] ?: FILE_CHECK;
791 security_current_getsecid_subj(&secid);
792 return process_measurement(file, current_cred(), secid, NULL,
793 0, MAY_READ, func);
794 }
795
796 const int read_idmap[READING_MAX_ID] = {
797 [READING_FIRMWARE] = FIRMWARE_CHECK,
798 [READING_MODULE] = MODULE_CHECK,
799 [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
800 [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
801 [READING_POLICY] = POLICY_CHECK
802 };
803
804 /**
805 * ima_post_read_file - in memory collect/appraise/audit measurement
806 * @file: pointer to the file to be measured/appraised/audit
807 * @buf: pointer to in memory file contents
808 * @size: size of in memory file contents
809 * @read_id: caller identifier
810 *
811 * Measure/appraise/audit in memory file based on policy. Policy rules
812 * are written in terms of a policy identifier.
813 *
814 * On success return 0. On integrity appraisal error, assuming the file
815 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
816 */
817 static int ima_post_read_file(struct file *file, char *buf, loff_t size,
818 enum kernel_read_file_id read_id)
819 {
820 enum ima_hooks func;
821 u32 secid;
822
823 /* permit signed certs */
824 if (!file && read_id == READING_X509_CERTIFICATE)
825 return 0;
826
827 if (!file || !buf || size == 0) { /* should never happen */
828 if (ima_appraise & IMA_APPRAISE_ENFORCE)
829 return -EACCES;
830 return 0;
831 }
832
833 func = read_idmap[read_id] ?: FILE_CHECK;
834 security_current_getsecid_subj(&secid);
835 return process_measurement(file, current_cred(), secid, buf, size,
836 MAY_READ, func);
837 }
838
839 /**
840 * ima_load_data - appraise decision based on policy
841 * @id: kernel load data caller identifier
842 * @contents: whether the full contents will be available in a later
843 * call to ima_post_load_data().
844 *
845 * Callers of this LSM hook can not measure, appraise, or audit the
846 * data provided by userspace. Enforce policy rules requiring a file
847 * signature (eg. kexec'ed kernel image).
848 *
849 * For permission return 0, otherwise return -EACCES.
850 */
851 static int ima_load_data(enum kernel_load_data_id id, bool contents)
852 {
853 bool ima_enforce, sig_enforce;
854
855 ima_enforce =
856 (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
857
858 switch (id) {
859 case LOADING_KEXEC_IMAGE:
860 if (IS_ENABLED(CONFIG_KEXEC_SIG)
861 && arch_ima_get_secureboot()) {
862 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
863 return -EACCES;
864 }
865
866 if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
867 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
868 return -EACCES; /* INTEGRITY_UNKNOWN */
869 }
870 break;
871 case LOADING_FIRMWARE:
872 if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE) && !contents) {
873 pr_err("Prevent firmware sysfs fallback loading.\n");
874 return -EACCES; /* INTEGRITY_UNKNOWN */
875 }
876 break;
877 case LOADING_MODULE:
878 sig_enforce = is_module_sig_enforced();
879
880 if (ima_enforce && (!sig_enforce
881 && (ima_appraise & IMA_APPRAISE_MODULES))) {
882 pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
883 return -EACCES; /* INTEGRITY_UNKNOWN */
884 }
885 break;
886 default:
887 break;
888 }
889 return 0;
890 }
891
892 /**
893 * ima_post_load_data - appraise decision based on policy
894 * @buf: pointer to in memory file contents
895 * @size: size of in memory file contents
896 * @load_id: kernel load data caller identifier
897 * @description: @load_id-specific description of contents
898 *
899 * Measure/appraise/audit in memory buffer based on policy. Policy rules
900 * are written in terms of a policy identifier.
901 *
902 * On success return 0. On integrity appraisal error, assuming the file
903 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
904 */
905 static int ima_post_load_data(char *buf, loff_t size,
906 enum kernel_load_data_id load_id,
907 char *description)
908 {
909 if (load_id == LOADING_FIRMWARE) {
910 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
911 (ima_appraise & IMA_APPRAISE_ENFORCE)) {
912 pr_err("Prevent firmware loading_store.\n");
913 return -EACCES; /* INTEGRITY_UNKNOWN */
914 }
915 return 0;
916 }
917
918 /*
919 * Measure the init_module syscall buffer containing the ELF image.
920 */
921 if (load_id == LOADING_MODULE)
922 ima_measure_critical_data("modules", "init_module",
923 buf, size, true, NULL, 0);
924
925 return 0;
926 }
927
928 /**
929 * process_buffer_measurement - Measure the buffer or the buffer data hash
930 * @idmap: idmap of the mount the inode was found from
931 * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
932 * @buf: pointer to the buffer that needs to be added to the log.
933 * @size: size of buffer(in bytes).
934 * @eventname: event name to be used for the buffer entry.
935 * @func: IMA hook
936 * @pcr: pcr to extend the measurement
937 * @func_data: func specific data, may be NULL
938 * @buf_hash: measure buffer data hash
939 * @digest: buffer digest will be written to
940 * @digest_len: buffer length
941 *
942 * Based on policy, either the buffer data or buffer data hash is measured
943 *
944 * Return: 0 if the buffer has been successfully measured, 1 if the digest
945 * has been written to the passed location but not added to a measurement entry,
946 * a negative value otherwise.
947 */
948 int process_buffer_measurement(struct mnt_idmap *idmap,
949 struct inode *inode, const void *buf, int size,
950 const char *eventname, enum ima_hooks func,
951 int pcr, const char *func_data,
952 bool buf_hash, u8 *digest, size_t digest_len)
953 {
954 int ret = 0;
955 const char *audit_cause = "ENOMEM";
956 struct ima_template_entry *entry = NULL;
957 struct ima_iint_cache iint = {};
958 struct ima_event_data event_data = {.iint = &iint,
959 .filename = eventname,
960 .buf = buf,
961 .buf_len = size};
962 struct ima_template_desc *template;
963 struct ima_max_digest_data hash;
964 struct ima_digest_data *hash_hdr = container_of(&hash.hdr,
965 struct ima_digest_data, hdr);
966 char digest_hash[IMA_MAX_DIGEST_SIZE];
967 int digest_hash_len = hash_digest_size[ima_hash_algo];
968 int violation = 0;
969 int action = 0;
970 u32 secid;
971
972 if (digest && digest_len < digest_hash_len)
973 return -EINVAL;
974
975 if (!ima_policy_flag && !digest)
976 return -ENOENT;
977
978 template = ima_template_desc_buf();
979 if (!template) {
980 ret = -EINVAL;
981 audit_cause = "ima_template_desc_buf";
982 goto out;
983 }
984
985 /*
986 * Both LSM hooks and auxilary based buffer measurements are
987 * based on policy. To avoid code duplication, differentiate
988 * between the LSM hooks and auxilary buffer measurements,
989 * retrieving the policy rule information only for the LSM hook
990 * buffer measurements.
991 */
992 if (func) {
993 security_current_getsecid_subj(&secid);
994 action = ima_get_action(idmap, inode, current_cred(),
995 secid, 0, func, &pcr, &template,
996 func_data, NULL);
997 if (!(action & IMA_MEASURE) && !digest)
998 return -ENOENT;
999 }
1000
1001 if (!pcr)
1002 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
1003
1004 iint.ima_hash = hash_hdr;
1005 iint.ima_hash->algo = ima_hash_algo;
1006 iint.ima_hash->length = hash_digest_size[ima_hash_algo];
1007
1008 ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
1009 if (ret < 0) {
1010 audit_cause = "hashing_error";
1011 goto out;
1012 }
1013
1014 if (buf_hash) {
1015 memcpy(digest_hash, hash_hdr->digest, digest_hash_len);
1016
1017 ret = ima_calc_buffer_hash(digest_hash, digest_hash_len,
1018 iint.ima_hash);
1019 if (ret < 0) {
1020 audit_cause = "hashing_error";
1021 goto out;
1022 }
1023
1024 event_data.buf = digest_hash;
1025 event_data.buf_len = digest_hash_len;
1026 }
1027
1028 if (digest)
1029 memcpy(digest, iint.ima_hash->digest, digest_hash_len);
1030
1031 if (!ima_policy_flag || (func && !(action & IMA_MEASURE)))
1032 return 1;
1033
1034 ret = ima_alloc_init_template(&event_data, &entry, template);
1035 if (ret < 0) {
1036 audit_cause = "alloc_entry";
1037 goto out;
1038 }
1039
1040 ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr);
1041 if (ret < 0) {
1042 audit_cause = "store_entry";
1043 ima_free_template_entry(entry);
1044 }
1045
1046 out:
1047 if (ret < 0)
1048 integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL, eventname,
1049 func_measure_str(func),
1050 audit_cause, ret, 0, ret);
1051
1052 return ret;
1053 }
1054
1055 /**
1056 * ima_kexec_cmdline - measure kexec cmdline boot args
1057 * @kernel_fd: file descriptor of the kexec kernel being loaded
1058 * @buf: pointer to buffer
1059 * @size: size of buffer
1060 *
1061 * Buffers can only be measured, not appraised.
1062 */
1063 void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
1064 {
1065 struct fd f;
1066
1067 if (!buf || !size)
1068 return;
1069
1070 f = fdget(kernel_fd);
1071 if (!f.file)
1072 return;
1073
1074 process_buffer_measurement(file_mnt_idmap(f.file), file_inode(f.file),
1075 buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
1076 NULL, false, NULL, 0);
1077 fdput(f);
1078 }
1079
1080 /**
1081 * ima_measure_critical_data - measure kernel integrity critical data
1082 * @event_label: unique event label for grouping and limiting critical data
1083 * @event_name: event name for the record in the IMA measurement list
1084 * @buf: pointer to buffer data
1085 * @buf_len: length of buffer data (in bytes)
1086 * @hash: measure buffer data hash
1087 * @digest: buffer digest will be written to
1088 * @digest_len: buffer length
1089 *
1090 * Measure data critical to the integrity of the kernel into the IMA log
1091 * and extend the pcr. Examples of critical data could be various data
1092 * structures, policies, and states stored in kernel memory that can
1093 * impact the integrity of the system.
1094 *
1095 * Return: 0 if the buffer has been successfully measured, 1 if the digest
1096 * has been written to the passed location but not added to a measurement entry,
1097 * a negative value otherwise.
1098 */
1099 int ima_measure_critical_data(const char *event_label,
1100 const char *event_name,
1101 const void *buf, size_t buf_len,
1102 bool hash, u8 *digest, size_t digest_len)
1103 {
1104 if (!event_name || !event_label || !buf || !buf_len)
1105 return -ENOPARAM;
1106
1107 return process_buffer_measurement(&nop_mnt_idmap, NULL, buf, buf_len,
1108 event_name, CRITICAL_DATA, 0,
1109 event_label, hash, digest,
1110 digest_len);
1111 }
1112 EXPORT_SYMBOL_GPL(ima_measure_critical_data);
1113
1114 #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
1115
1116 /**
1117 * ima_kernel_module_request - Prevent crypto-pkcs1pad(rsa,*) requests
1118 * @kmod_name: kernel module name
1119 *
1120 * Avoid a verification loop where verifying the signature of the modprobe
1121 * binary requires executing modprobe itself. Since the modprobe iint->mutex
1122 * is already held when the signature verification is performed, a deadlock
1123 * occurs as soon as modprobe is executed within the critical region, since
1124 * the same lock cannot be taken again.
1125 *
1126 * This happens when public_key_verify_signature(), in case of RSA algorithm,
1127 * use alg_name to store internal information in order to construct an
1128 * algorithm on the fly, but crypto_larval_lookup() will try to use alg_name
1129 * in order to load a kernel module with same name.
1130 *
1131 * Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules,
1132 * we are safe to fail such module request from crypto_larval_lookup(), and
1133 * avoid the verification loop.
1134 *
1135 * Return: Zero if it is safe to load the kernel module, -EINVAL otherwise.
1136 */
1137 static int ima_kernel_module_request(char *kmod_name)
1138 {
1139 if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
1140 return -EINVAL;
1141
1142 return 0;
1143 }
1144
1145 #endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */
1146
1147 static int __init init_ima(void)
1148 {
1149 int error;
1150
1151 ima_appraise_parse_cmdline();
1152 ima_init_template_list();
1153 hash_setup(CONFIG_IMA_DEFAULT_HASH);
1154 error = ima_init();
1155
1156 if (error && strcmp(hash_algo_name[ima_hash_algo],
1157 CONFIG_IMA_DEFAULT_HASH) != 0) {
1158 pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
1159 hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
1160 hash_setup_done = 0;
1161 hash_setup(CONFIG_IMA_DEFAULT_HASH);
1162 error = ima_init();
1163 }
1164
1165 if (error)
1166 return error;
1167
1168 error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier);
1169 if (error)
1170 pr_warn("Couldn't register LSM notifier, error %d\n", error);
1171
1172 if (!error)
1173 ima_update_policy_flags();
1174
1175 return error;
1176 }
1177
1178 static struct security_hook_list ima_hooks[] __ro_after_init = {
1179 LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
1180 LSM_HOOK_INIT(file_post_open, ima_file_check),
1181 LSM_HOOK_INIT(inode_post_create_tmpfile, ima_post_create_tmpfile),
1182 LSM_HOOK_INIT(file_release, ima_file_free),
1183 LSM_HOOK_INIT(mmap_file, ima_file_mmap),
1184 LSM_HOOK_INIT(file_mprotect, ima_file_mprotect),
1185 LSM_HOOK_INIT(kernel_load_data, ima_load_data),
1186 LSM_HOOK_INIT(kernel_post_load_data, ima_post_load_data),
1187 LSM_HOOK_INIT(kernel_read_file, ima_read_file),
1188 LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file),
1189 LSM_HOOK_INIT(path_post_mknod, ima_post_path_mknod),
1190 #ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
1191 LSM_HOOK_INIT(key_post_create_or_update, ima_post_key_create_or_update),
1192 #endif
1193 #ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
1194 LSM_HOOK_INIT(kernel_module_request, ima_kernel_module_request),
1195 #endif
1196 LSM_HOOK_INIT(inode_free_security_rcu, ima_inode_free_rcu),
1197 };
1198
1199 static const struct lsm_id ima_lsmid = {
1200 .name = "ima",
1201 .id = LSM_ID_IMA,
1202 };
1203
1204 static int __init init_ima_lsm(void)
1205 {
1206 ima_iintcache_init();
1207 security_add_hooks(ima_hooks, ARRAY_SIZE(ima_hooks), &ima_lsmid);
1208 init_ima_appraise_lsm(&ima_lsmid);
1209 return 0;
1210 }
1211
1212 struct lsm_blob_sizes ima_blob_sizes __ro_after_init = {
1213 .lbs_inode = sizeof(struct ima_iint_cache *),
1214 };
1215
1216 DEFINE_LSM(ima) = {
1217 .name = "ima",
1218 .init = init_ima_lsm,
1219 .order = LSM_ORDER_LAST,
1220 .blobs = &ima_blob_sizes,
1221 };
1222
1223 late_initcall(init_ima); /* Start IMA after the TPM is available */
1224
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