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/iversion.h>
28 #include <linux/fs.h>
29
30 #include "ima.h"
31
32 #ifdef CONFIG_IMA_APPRAISE
33 int ima_appraise = IMA_APPRAISE_ENFORCE;
34 #else
35 int ima_appraise;
36 #endif
37
38 int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1;
39 static int hash_setup_done;
40
41 static struct notifier_block ima_lsm_policy_notifier = {
42 .notifier_call = ima_lsm_policy_change,
43 };
44
hash_setup(char * str)45 static int __init hash_setup(char *str)
46 {
47 struct ima_template_desc *template_desc = ima_template_desc_current();
48 int i;
49
50 if (hash_setup_done)
51 return 1;
52
53 if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) {
54 if (strncmp(str, "sha1", 4) == 0) {
55 ima_hash_algo = HASH_ALGO_SHA1;
56 } else if (strncmp(str, "md5", 3) == 0) {
57 ima_hash_algo = HASH_ALGO_MD5;
58 } else {
59 pr_err("invalid hash algorithm \"%s\" for template \"%s\"",
60 str, IMA_TEMPLATE_IMA_NAME);
61 return 1;
62 }
63 goto out;
64 }
65
66 i = match_string(hash_algo_name, HASH_ALGO__LAST, str);
67 if (i < 0) {
68 pr_err("invalid hash algorithm \"%s\"", str);
69 return 1;
70 }
71
72 ima_hash_algo = i;
73 out:
74 hash_setup_done = 1;
75 return 1;
76 }
77 __setup("ima_hash=", hash_setup);
78
ima_get_current_hash_algo(void)79 enum hash_algo ima_get_current_hash_algo(void)
80 {
81 return ima_hash_algo;
82 }
83
84 /* Prevent mmap'ing a file execute that is already mmap'ed write */
mmap_violation_check(enum ima_hooks func,struct file * file,char ** pathbuf,const char ** pathname,char * filename)85 static int mmap_violation_check(enum ima_hooks func, struct file *file,
86 char **pathbuf, const char **pathname,
87 char *filename)
88 {
89 struct inode *inode;
90 int rc = 0;
91
92 if ((func == MMAP_CHECK) && mapping_writably_mapped(file->f_mapping)) {
93 rc = -ETXTBSY;
94 inode = file_inode(file);
95
96 if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */
97 *pathname = ima_d_path(&file->f_path, pathbuf,
98 filename);
99 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname,
100 "mmap_file", "mmapped_writers", rc, 0);
101 }
102 return rc;
103 }
104
105 /*
106 * ima_rdwr_violation_check
107 *
108 * Only invalidate the PCR for measured files:
109 * - Opening a file for write when already open for read,
110 * results in a time of measure, time of use (ToMToU) error.
111 * - Opening a file for read when already open for write,
112 * could result in a file measurement error.
113 *
114 */
ima_rdwr_violation_check(struct file * file,struct integrity_iint_cache * iint,int must_measure,char ** pathbuf,const char ** pathname,char * filename)115 static void ima_rdwr_violation_check(struct file *file,
116 struct integrity_iint_cache *iint,
117 int must_measure,
118 char **pathbuf,
119 const char **pathname,
120 char *filename)
121 {
122 struct inode *inode = file_inode(file);
123 fmode_t mode = file->f_mode;
124 bool send_tomtou = false, send_writers = false;
125
126 if (mode & FMODE_WRITE) {
127 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) {
128 if (!iint)
129 iint = integrity_iint_find(inode);
130 /* IMA_MEASURE is set from reader side */
131 if (iint && test_bit(IMA_MUST_MEASURE,
132 &iint->atomic_flags))
133 send_tomtou = true;
134 }
135 } else {
136 if (must_measure)
137 set_bit(IMA_MUST_MEASURE, &iint->atomic_flags);
138 if (inode_is_open_for_write(inode) && must_measure)
139 send_writers = true;
140 }
141
142 if (!send_tomtou && !send_writers)
143 return;
144
145 *pathname = ima_d_path(&file->f_path, pathbuf, filename);
146
147 if (send_tomtou)
148 ima_add_violation(file, *pathname, iint,
149 "invalid_pcr", "ToMToU");
150 if (send_writers)
151 ima_add_violation(file, *pathname, iint,
152 "invalid_pcr", "open_writers");
153 }
154
ima_check_last_writer(struct integrity_iint_cache * iint,struct inode * inode,struct file * file)155 static void ima_check_last_writer(struct integrity_iint_cache *iint,
156 struct inode *inode, struct file *file)
157 {
158 fmode_t mode = file->f_mode;
159 bool update;
160
161 if (!(mode & FMODE_WRITE))
162 return;
163
164 mutex_lock(&iint->mutex);
165 if (atomic_read(&inode->i_writecount) == 1) {
166 update = test_and_clear_bit(IMA_UPDATE_XATTR,
167 &iint->atomic_flags);
168 if (!IS_I_VERSION(inode) ||
169 !inode_eq_iversion(inode, iint->version) ||
170 (iint->flags & IMA_NEW_FILE)) {
171 iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
172 iint->measured_pcrs = 0;
173 if (update)
174 ima_update_xattr(iint, file);
175 }
176 }
177 mutex_unlock(&iint->mutex);
178 }
179
180 /**
181 * ima_file_free - called on __fput()
182 * @file: pointer to file structure being freed
183 *
184 * Flag files that changed, based on i_version
185 */
ima_file_free(struct file * file)186 void ima_file_free(struct file *file)
187 {
188 struct inode *inode = file_inode(file);
189 struct integrity_iint_cache *iint;
190
191 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
192 return;
193
194 iint = integrity_iint_find(inode);
195 if (!iint)
196 return;
197
198 ima_check_last_writer(iint, inode, file);
199 }
200
process_measurement(struct file * file,const struct cred * cred,u32 secid,char * buf,loff_t size,int mask,enum ima_hooks func)201 static int process_measurement(struct file *file, const struct cred *cred,
202 u32 secid, char *buf, loff_t size, int mask,
203 enum ima_hooks func)
204 {
205 struct inode *inode = file_inode(file);
206 struct integrity_iint_cache *iint = NULL;
207 struct ima_template_desc *template_desc = NULL;
208 char *pathbuf = NULL;
209 char filename[NAME_MAX];
210 const char *pathname = NULL;
211 int rc = 0, action, must_appraise = 0;
212 int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
213 struct evm_ima_xattr_data *xattr_value = NULL;
214 struct modsig *modsig = NULL;
215 int xattr_len = 0;
216 bool violation_check;
217 enum hash_algo hash_algo;
218 unsigned int allowed_algos = 0;
219
220 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
221 return 0;
222
223 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
224 * bitmask based on the appraise/audit/measurement policy.
225 * Included is the appraise submask.
226 */
227 action = ima_get_action(file_mnt_user_ns(file), inode, cred, secid,
228 mask, func, &pcr, &template_desc, NULL,
229 &allowed_algos);
230 violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) &&
231 (ima_policy_flag & IMA_MEASURE));
232 if (!action && !violation_check)
233 return 0;
234
235 must_appraise = action & IMA_APPRAISE;
236
237 /* Is the appraise rule hook specific? */
238 if (action & IMA_FILE_APPRAISE)
239 func = FILE_CHECK;
240
241 inode_lock(inode);
242
243 if (action) {
244 iint = integrity_inode_get(inode);
245 if (!iint)
246 rc = -ENOMEM;
247 }
248
249 if (!rc && violation_check)
250 ima_rdwr_violation_check(file, iint, action & IMA_MEASURE,
251 &pathbuf, &pathname, filename);
252
253 inode_unlock(inode);
254
255 if (rc)
256 goto out;
257 if (!action)
258 goto out;
259
260 mutex_lock(&iint->mutex);
261
262 if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags))
263 /* reset appraisal flags if ima_inode_post_setattr was called */
264 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
265 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
266 IMA_NONACTION_FLAGS);
267
268 /*
269 * Re-evaulate the file if either the xattr has changed or the
270 * kernel has no way of detecting file change on the filesystem.
271 * (Limited to privileged mounted filesystems.)
272 */
273 if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) ||
274 ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
275 !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
276 !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
277 iint->flags &= ~IMA_DONE_MASK;
278 iint->measured_pcrs = 0;
279 }
280
281 /* Determine if already appraised/measured based on bitmask
282 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
283 * IMA_AUDIT, IMA_AUDITED)
284 */
285 iint->flags |= action;
286 action &= IMA_DO_MASK;
287 action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
288
289 /* If target pcr is already measured, unset IMA_MEASURE action */
290 if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
291 action ^= IMA_MEASURE;
292
293 /* HASH sets the digital signature and update flags, nothing else */
294 if ((action & IMA_HASH) &&
295 !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) {
296 xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
297 if ((xattr_value && xattr_len > 2) &&
298 (xattr_value->type == EVM_IMA_XATTR_DIGSIG))
299 set_bit(IMA_DIGSIG, &iint->atomic_flags);
300 iint->flags |= IMA_HASHED;
301 action ^= IMA_HASH;
302 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
303 }
304
305 /* Nothing to do, just return existing appraised status */
306 if (!action) {
307 if (must_appraise) {
308 rc = mmap_violation_check(func, file, &pathbuf,
309 &pathname, filename);
310 if (!rc)
311 rc = ima_get_cache_status(iint, func);
312 }
313 goto out_locked;
314 }
315
316 if ((action & IMA_APPRAISE_SUBMASK) ||
317 strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) {
318 /* read 'security.ima' */
319 xattr_len = ima_read_xattr(file_dentry(file), &xattr_value);
320
321 /*
322 * Read the appended modsig if allowed by the policy, and allow
323 * an additional measurement list entry, if needed, based on the
324 * template format and whether the file was already measured.
325 */
326 if (iint->flags & IMA_MODSIG_ALLOWED) {
327 rc = ima_read_modsig(func, buf, size, &modsig);
328
329 if (!rc && ima_template_has_modsig(template_desc) &&
330 iint->flags & IMA_MEASURED)
331 action |= IMA_MEASURE;
332 }
333 }
334
335 hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
336
337 rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig);
338 if (rc == -ENOMEM)
339 goto out_locked;
340
341 if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
342 pathname = ima_d_path(&file->f_path, &pathbuf, filename);
343
344 if (action & IMA_MEASURE)
345 ima_store_measurement(iint, file, pathname,
346 xattr_value, xattr_len, modsig, pcr,
347 template_desc);
348 if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
349 rc = ima_check_blacklist(iint, modsig, pcr);
350 if (rc != -EPERM) {
351 inode_lock(inode);
352 rc = ima_appraise_measurement(func, iint, file,
353 pathname, xattr_value,
354 xattr_len, modsig);
355 inode_unlock(inode);
356 }
357 if (!rc)
358 rc = mmap_violation_check(func, file, &pathbuf,
359 &pathname, filename);
360 }
361 if (action & IMA_AUDIT)
362 ima_audit_measurement(iint, pathname);
363
364 if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
365 rc = 0;
366
367 /* Ensure the digest was generated using an allowed algorithm */
368 if (rc == 0 && must_appraise && allowed_algos != 0 &&
369 (allowed_algos & (1U << hash_algo)) == 0) {
370 rc = -EACCES;
371
372 integrity_audit_msg(AUDIT_INTEGRITY_DATA, file_inode(file),
373 pathname, "collect_data",
374 "denied-hash-algorithm", rc, 0);
375 }
376 out_locked:
377 if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
378 !(iint->flags & IMA_NEW_FILE))
379 rc = -EACCES;
380 mutex_unlock(&iint->mutex);
381 kfree(xattr_value);
382 ima_free_modsig(modsig);
383 out:
384 if (pathbuf)
385 __putname(pathbuf);
386 if (must_appraise) {
387 if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
388 return -EACCES;
389 if (file->f_mode & FMODE_WRITE)
390 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
391 }
392 return 0;
393 }
394
395 /**
396 * ima_file_mmap - based on policy, collect/store measurement.
397 * @file: pointer to the file to be measured (May be NULL)
398 * @prot: contains the protection that will be applied by the kernel.
399 *
400 * Measure files being mmapped executable based on the ima_must_measure()
401 * policy decision.
402 *
403 * On success return 0. On integrity appraisal error, assuming the file
404 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
405 */
ima_file_mmap(struct file * file,unsigned long prot)406 int ima_file_mmap(struct file *file, unsigned long prot)
407 {
408 u32 secid;
409
410 if (file && (prot & PROT_EXEC)) {
411 security_current_getsecid_subj(&secid);
412 return process_measurement(file, current_cred(), secid, NULL,
413 0, MAY_EXEC, MMAP_CHECK);
414 }
415
416 return 0;
417 }
418
419 /**
420 * ima_file_mprotect - based on policy, limit mprotect change
421 * @vma: vm_area_struct protection is set to
422 * @prot: contains the protection that will be applied by the kernel.
423 *
424 * Files can be mmap'ed read/write and later changed to execute to circumvent
425 * IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore
426 * would be taken before i_mutex), files can not be measured or appraised at
427 * this point. Eliminate this integrity gap by denying the mprotect
428 * PROT_EXECUTE change, if an mmap appraise policy rule exists.
429 *
430 * On mprotect change success, return 0. On failure, return -EACESS.
431 */
ima_file_mprotect(struct vm_area_struct * vma,unsigned long prot)432 int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot)
433 {
434 struct ima_template_desc *template = NULL;
435 struct file *file;
436 char filename[NAME_MAX];
437 char *pathbuf = NULL;
438 const char *pathname = NULL;
439 struct inode *inode;
440 int result = 0;
441 int action;
442 u32 secid;
443 int pcr;
444
445 /* Is mprotect making an mmap'ed file executable? */
446 if (!(ima_policy_flag & IMA_APPRAISE) || !vma->vm_file ||
447 !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC))
448 return 0;
449
450 security_current_getsecid_subj(&secid);
451 inode = file_inode(vma->vm_file);
452 action = ima_get_action(file_mnt_user_ns(vma->vm_file), inode,
453 current_cred(), secid, MAY_EXEC, MMAP_CHECK,
454 &pcr, &template, NULL, NULL);
455
456 /* Is the mmap'ed file in policy? */
457 if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))
458 return 0;
459
460 if (action & IMA_APPRAISE_SUBMASK)
461 result = -EPERM;
462
463 file = vma->vm_file;
464 pathname = ima_d_path(&file->f_path, &pathbuf, filename);
465 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, pathname,
466 "collect_data", "failed-mprotect", result, 0);
467 if (pathbuf)
468 __putname(pathbuf);
469
470 return result;
471 }
472
473 /**
474 * ima_bprm_check - based on policy, collect/store measurement.
475 * @bprm: contains the linux_binprm structure
476 *
477 * The OS protects against an executable file, already open for write,
478 * from being executed in deny_write_access() and an executable file,
479 * already open for execute, from being modified in get_write_access().
480 * So we can be certain that what we verify and measure here is actually
481 * what is being executed.
482 *
483 * On success return 0. On integrity appraisal error, assuming the file
484 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
485 */
ima_bprm_check(struct linux_binprm * bprm)486 int ima_bprm_check(struct linux_binprm *bprm)
487 {
488 int ret;
489 u32 secid;
490
491 security_current_getsecid_subj(&secid);
492 ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0,
493 MAY_EXEC, BPRM_CHECK);
494 if (ret)
495 return ret;
496
497 security_cred_getsecid(bprm->cred, &secid);
498 return process_measurement(bprm->file, bprm->cred, secid, NULL, 0,
499 MAY_EXEC, CREDS_CHECK);
500 }
501
502 /**
503 * ima_file_check - based on policy, collect/store measurement.
504 * @file: pointer to the file to be measured
505 * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND
506 *
507 * Measure files based on the ima_must_measure() policy decision.
508 *
509 * On success return 0. On integrity appraisal error, assuming the file
510 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
511 */
ima_file_check(struct file * file,int mask)512 int ima_file_check(struct file *file, int mask)
513 {
514 u32 secid;
515
516 security_current_getsecid_subj(&secid);
517 return process_measurement(file, current_cred(), secid, NULL, 0,
518 mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
519 MAY_APPEND), FILE_CHECK);
520 }
521 EXPORT_SYMBOL_GPL(ima_file_check);
522
__ima_inode_hash(struct inode * inode,struct file * file,char * buf,size_t buf_size)523 static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
524 size_t buf_size)
525 {
526 struct integrity_iint_cache *iint = NULL, tmp_iint;
527 int rc, hash_algo;
528
529 if (ima_policy_flag) {
530 iint = integrity_iint_find(inode);
531 if (iint)
532 mutex_lock(&iint->mutex);
533 }
534
535 if ((!iint || !(iint->flags & IMA_COLLECTED)) && file) {
536 if (iint)
537 mutex_unlock(&iint->mutex);
538
539 memset(&tmp_iint, 0, sizeof(tmp_iint));
540 tmp_iint.inode = inode;
541 mutex_init(&tmp_iint.mutex);
542
543 rc = ima_collect_measurement(&tmp_iint, file, NULL, 0,
544 ima_hash_algo, NULL);
545 if (rc < 0) {
546 /* ima_hash could be allocated in case of failure. */
547 if (rc != -ENOMEM)
548 kfree(tmp_iint.ima_hash);
549
550 return -EOPNOTSUPP;
551 }
552
553 iint = &tmp_iint;
554 mutex_lock(&iint->mutex);
555 }
556
557 if (!iint)
558 return -EOPNOTSUPP;
559
560 /*
561 * ima_file_hash can be called when ima_collect_measurement has still
562 * not been called, we might not always have a hash.
563 */
564 if (!iint->ima_hash) {
565 mutex_unlock(&iint->mutex);
566 return -EOPNOTSUPP;
567 }
568
569 if (buf) {
570 size_t copied_size;
571
572 copied_size = min_t(size_t, iint->ima_hash->length, buf_size);
573 memcpy(buf, iint->ima_hash->digest, copied_size);
574 }
575 hash_algo = iint->ima_hash->algo;
576 mutex_unlock(&iint->mutex);
577
578 if (iint == &tmp_iint)
579 kfree(iint->ima_hash);
580
581 return hash_algo;
582 }
583
584 /**
585 * ima_file_hash - return a measurement of the file
586 * @file: pointer to the file
587 * @buf: buffer in which to store the hash
588 * @buf_size: length of the buffer
589 *
590 * On success, return the hash algorithm (as defined in the enum hash_algo).
591 * If buf is not NULL, this function also outputs the hash into buf.
592 * If the hash is larger than buf_size, then only buf_size bytes will be copied.
593 * It generally just makes sense to pass a buffer capable of holding the largest
594 * possible hash: IMA_MAX_DIGEST_SIZE.
595 * The file hash returned is based on the entire file, including the appended
596 * signature.
597 *
598 * If the measurement cannot be performed, return -EOPNOTSUPP.
599 * If the parameters are incorrect, return -EINVAL.
600 */
ima_file_hash(struct file * file,char * buf,size_t buf_size)601 int ima_file_hash(struct file *file, char *buf, size_t buf_size)
602 {
603 if (!file)
604 return -EINVAL;
605
606 return __ima_inode_hash(file_inode(file), file, buf, buf_size);
607 }
608 EXPORT_SYMBOL_GPL(ima_file_hash);
609
610 /**
611 * ima_inode_hash - return the stored measurement if the inode has been hashed
612 * and is in the iint cache.
613 * @inode: pointer to the inode
614 * @buf: buffer in which to store the hash
615 * @buf_size: length of the buffer
616 *
617 * On success, return the hash algorithm (as defined in the enum hash_algo).
618 * If buf is not NULL, this function also outputs the hash into buf.
619 * If the hash is larger than buf_size, then only buf_size bytes will be copied.
620 * It generally just makes sense to pass a buffer capable of holding the largest
621 * possible hash: IMA_MAX_DIGEST_SIZE.
622 * The hash returned is based on the entire contents, including the appended
623 * signature.
624 *
625 * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
626 * If the parameters are incorrect, return -EINVAL.
627 */
ima_inode_hash(struct inode * inode,char * buf,size_t buf_size)628 int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
629 {
630 if (!inode)
631 return -EINVAL;
632
633 return __ima_inode_hash(inode, NULL, buf, buf_size);
634 }
635 EXPORT_SYMBOL_GPL(ima_inode_hash);
636
637 /**
638 * ima_post_create_tmpfile - mark newly created tmpfile as new
639 * @mnt_userns: user namespace of the mount the inode was found from
640 * @inode: inode of the newly created tmpfile
641 *
642 * No measuring, appraising or auditing of newly created tmpfiles is needed.
643 * Skip calling process_measurement(), but indicate which newly, created
644 * tmpfiles are in policy.
645 */
ima_post_create_tmpfile(struct user_namespace * mnt_userns,struct inode * inode)646 void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
647 struct inode *inode)
648 {
649 struct integrity_iint_cache *iint;
650 int must_appraise;
651
652 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
653 return;
654
655 must_appraise = ima_must_appraise(mnt_userns, inode, MAY_ACCESS,
656 FILE_CHECK);
657 if (!must_appraise)
658 return;
659
660 /* Nothing to do if we can't allocate memory */
661 iint = integrity_inode_get(inode);
662 if (!iint)
663 return;
664
665 /* needed for writing the security xattrs */
666 set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags);
667 iint->ima_file_status = INTEGRITY_PASS;
668 }
669
670 /**
671 * ima_post_path_mknod - mark as a new inode
672 * @mnt_userns: user namespace of the mount the inode was found from
673 * @dentry: newly created dentry
674 *
675 * Mark files created via the mknodat syscall as new, so that the
676 * file data can be written later.
677 */
ima_post_path_mknod(struct user_namespace * mnt_userns,struct dentry * dentry)678 void ima_post_path_mknod(struct user_namespace *mnt_userns,
679 struct dentry *dentry)
680 {
681 struct integrity_iint_cache *iint;
682 struct inode *inode = dentry->d_inode;
683 int must_appraise;
684
685 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
686 return;
687
688 must_appraise = ima_must_appraise(mnt_userns, inode, MAY_ACCESS,
689 FILE_CHECK);
690 if (!must_appraise)
691 return;
692
693 /* Nothing to do if we can't allocate memory */
694 iint = integrity_inode_get(inode);
695 if (!iint)
696 return;
697
698 /* needed for re-opening empty files */
699 iint->flags |= IMA_NEW_FILE;
700 }
701
702 /**
703 * ima_read_file - pre-measure/appraise hook decision based on policy
704 * @file: pointer to the file to be measured/appraised/audit
705 * @read_id: caller identifier
706 * @contents: whether a subsequent call will be made to ima_post_read_file()
707 *
708 * Permit reading a file based on policy. The policy rules are written
709 * in terms of the policy identifier. Appraising the integrity of
710 * a file requires a file descriptor.
711 *
712 * For permission return 0, otherwise return -EACCES.
713 */
ima_read_file(struct file * file,enum kernel_read_file_id read_id,bool contents)714 int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
715 bool contents)
716 {
717 enum ima_hooks func;
718 u32 secid;
719
720 /*
721 * Do devices using pre-allocated memory run the risk of the
722 * firmware being accessible to the device prior to the completion
723 * of IMA's signature verification any more than when using two
724 * buffers? It may be desirable to include the buffer address
725 * in this API and walk all the dma_map_single() mappings to check.
726 */
727
728 /*
729 * There will be a call made to ima_post_read_file() with
730 * a filled buffer, so we don't need to perform an extra
731 * read early here.
732 */
733 if (contents)
734 return 0;
735
736 /* Read entire file for all partial reads. */
737 func = read_idmap[read_id] ?: FILE_CHECK;
738 security_current_getsecid_subj(&secid);
739 return process_measurement(file, current_cred(), secid, NULL,
740 0, MAY_READ, func);
741 }
742
743 const int read_idmap[READING_MAX_ID] = {
744 [READING_FIRMWARE] = FIRMWARE_CHECK,
745 [READING_MODULE] = MODULE_CHECK,
746 [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
747 [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
748 [READING_POLICY] = POLICY_CHECK
749 };
750
751 /**
752 * ima_post_read_file - in memory collect/appraise/audit measurement
753 * @file: pointer to the file to be measured/appraised/audit
754 * @buf: pointer to in memory file contents
755 * @size: size of in memory file contents
756 * @read_id: caller identifier
757 *
758 * Measure/appraise/audit in memory file based on policy. Policy rules
759 * are written in terms of a policy identifier.
760 *
761 * On success return 0. On integrity appraisal error, assuming the file
762 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
763 */
ima_post_read_file(struct file * file,void * buf,loff_t size,enum kernel_read_file_id read_id)764 int ima_post_read_file(struct file *file, void *buf, loff_t size,
765 enum kernel_read_file_id read_id)
766 {
767 enum ima_hooks func;
768 u32 secid;
769
770 /* permit signed certs */
771 if (!file && read_id == READING_X509_CERTIFICATE)
772 return 0;
773
774 if (!file || !buf || size == 0) { /* should never happen */
775 if (ima_appraise & IMA_APPRAISE_ENFORCE)
776 return -EACCES;
777 return 0;
778 }
779
780 func = read_idmap[read_id] ?: FILE_CHECK;
781 security_current_getsecid_subj(&secid);
782 return process_measurement(file, current_cred(), secid, buf, size,
783 MAY_READ, func);
784 }
785
786 /**
787 * ima_load_data - appraise decision based on policy
788 * @id: kernel load data caller identifier
789 * @contents: whether the full contents will be available in a later
790 * call to ima_post_load_data().
791 *
792 * Callers of this LSM hook can not measure, appraise, or audit the
793 * data provided by userspace. Enforce policy rules requiring a file
794 * signature (eg. kexec'ed kernel image).
795 *
796 * For permission return 0, otherwise return -EACCES.
797 */
ima_load_data(enum kernel_load_data_id id,bool contents)798 int ima_load_data(enum kernel_load_data_id id, bool contents)
799 {
800 bool ima_enforce, sig_enforce;
801
802 ima_enforce =
803 (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
804
805 switch (id) {
806 case LOADING_KEXEC_IMAGE:
807 if (IS_ENABLED(CONFIG_KEXEC_SIG)
808 && arch_ima_get_secureboot()) {
809 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
810 return -EACCES;
811 }
812
813 if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
814 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
815 return -EACCES; /* INTEGRITY_UNKNOWN */
816 }
817 break;
818 case LOADING_FIRMWARE:
819 if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE) && !contents) {
820 pr_err("Prevent firmware sysfs fallback loading.\n");
821 return -EACCES; /* INTEGRITY_UNKNOWN */
822 }
823 break;
824 case LOADING_MODULE:
825 sig_enforce = is_module_sig_enforced();
826
827 if (ima_enforce && (!sig_enforce
828 && (ima_appraise & IMA_APPRAISE_MODULES))) {
829 pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
830 return -EACCES; /* INTEGRITY_UNKNOWN */
831 }
832 break;
833 default:
834 break;
835 }
836 return 0;
837 }
838
839 /**
840 * ima_post_load_data - appraise decision based on policy
841 * @buf: pointer to in memory file contents
842 * @size: size of in memory file contents
843 * @load_id: kernel load data caller identifier
844 * @description: @load_id-specific description of contents
845 *
846 * Measure/appraise/audit in memory buffer based on policy. Policy rules
847 * are written in terms of a policy identifier.
848 *
849 * On success return 0. On integrity appraisal error, assuming the file
850 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
851 */
ima_post_load_data(char * buf,loff_t size,enum kernel_load_data_id load_id,char * description)852 int ima_post_load_data(char *buf, loff_t size,
853 enum kernel_load_data_id load_id,
854 char *description)
855 {
856 if (load_id == LOADING_FIRMWARE) {
857 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
858 (ima_appraise & IMA_APPRAISE_ENFORCE)) {
859 pr_err("Prevent firmware loading_store.\n");
860 return -EACCES; /* INTEGRITY_UNKNOWN */
861 }
862 return 0;
863 }
864
865 return 0;
866 }
867
868 /**
869 * process_buffer_measurement - Measure the buffer or the buffer data hash
870 * @mnt_userns: user namespace of the mount the inode was found from
871 * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
872 * @buf: pointer to the buffer that needs to be added to the log.
873 * @size: size of buffer(in bytes).
874 * @eventname: event name to be used for the buffer entry.
875 * @func: IMA hook
876 * @pcr: pcr to extend the measurement
877 * @func_data: func specific data, may be NULL
878 * @buf_hash: measure buffer data hash
879 * @digest: buffer digest will be written to
880 * @digest_len: buffer length
881 *
882 * Based on policy, either the buffer data or buffer data hash is measured
883 *
884 * Return: 0 if the buffer has been successfully measured, 1 if the digest
885 * has been written to the passed location but not added to a measurement entry,
886 * a negative value otherwise.
887 */
process_buffer_measurement(struct user_namespace * mnt_userns,struct inode * inode,const void * buf,int size,const char * eventname,enum ima_hooks func,int pcr,const char * func_data,bool buf_hash,u8 * digest,size_t digest_len)888 int process_buffer_measurement(struct user_namespace *mnt_userns,
889 struct inode *inode, const void *buf, int size,
890 const char *eventname, enum ima_hooks func,
891 int pcr, const char *func_data,
892 bool buf_hash, u8 *digest, size_t digest_len)
893 {
894 int ret = 0;
895 const char *audit_cause = "ENOMEM";
896 struct ima_template_entry *entry = NULL;
897 struct integrity_iint_cache iint = {};
898 struct ima_event_data event_data = {.iint = &iint,
899 .filename = eventname,
900 .buf = buf,
901 .buf_len = size};
902 struct ima_template_desc *template;
903 struct ima_max_digest_data hash;
904 char digest_hash[IMA_MAX_DIGEST_SIZE];
905 int digest_hash_len = hash_digest_size[ima_hash_algo];
906 int violation = 0;
907 int action = 0;
908 u32 secid;
909
910 if (digest && digest_len < digest_hash_len)
911 return -EINVAL;
912
913 if (!ima_policy_flag && !digest)
914 return -ENOENT;
915
916 template = ima_template_desc_buf();
917 if (!template) {
918 ret = -EINVAL;
919 audit_cause = "ima_template_desc_buf";
920 goto out;
921 }
922
923 /*
924 * Both LSM hooks and auxilary based buffer measurements are
925 * based on policy. To avoid code duplication, differentiate
926 * between the LSM hooks and auxilary buffer measurements,
927 * retrieving the policy rule information only for the LSM hook
928 * buffer measurements.
929 */
930 if (func) {
931 security_current_getsecid_subj(&secid);
932 action = ima_get_action(mnt_userns, inode, current_cred(),
933 secid, 0, func, &pcr, &template,
934 func_data, NULL);
935 if (!(action & IMA_MEASURE) && !digest)
936 return -ENOENT;
937 }
938
939 if (!pcr)
940 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
941
942 iint.ima_hash = &hash.hdr;
943 iint.ima_hash->algo = ima_hash_algo;
944 iint.ima_hash->length = hash_digest_size[ima_hash_algo];
945
946 ret = ima_calc_buffer_hash(buf, size, iint.ima_hash);
947 if (ret < 0) {
948 audit_cause = "hashing_error";
949 goto out;
950 }
951
952 if (buf_hash) {
953 memcpy(digest_hash, hash.hdr.digest, digest_hash_len);
954
955 ret = ima_calc_buffer_hash(digest_hash, digest_hash_len,
956 iint.ima_hash);
957 if (ret < 0) {
958 audit_cause = "hashing_error";
959 goto out;
960 }
961
962 event_data.buf = digest_hash;
963 event_data.buf_len = digest_hash_len;
964 }
965
966 if (digest)
967 memcpy(digest, iint.ima_hash->digest, digest_hash_len);
968
969 if (!ima_policy_flag || (func && !(action & IMA_MEASURE)))
970 return 1;
971
972 ret = ima_alloc_init_template(&event_data, &entry, template);
973 if (ret < 0) {
974 audit_cause = "alloc_entry";
975 goto out;
976 }
977
978 ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr);
979 if (ret < 0) {
980 audit_cause = "store_entry";
981 ima_free_template_entry(entry);
982 }
983
984 out:
985 if (ret < 0)
986 integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL, eventname,
987 func_measure_str(func),
988 audit_cause, ret, 0, ret);
989
990 return ret;
991 }
992
993 /**
994 * ima_kexec_cmdline - measure kexec cmdline boot args
995 * @kernel_fd: file descriptor of the kexec kernel being loaded
996 * @buf: pointer to buffer
997 * @size: size of buffer
998 *
999 * Buffers can only be measured, not appraised.
1000 */
ima_kexec_cmdline(int kernel_fd,const void * buf,int size)1001 void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
1002 {
1003 struct fd f;
1004
1005 if (!buf || !size)
1006 return;
1007
1008 f = fdget(kernel_fd);
1009 if (!f.file)
1010 return;
1011
1012 process_buffer_measurement(file_mnt_user_ns(f.file), file_inode(f.file),
1013 buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0,
1014 NULL, false, NULL, 0);
1015 fdput(f);
1016 }
1017
1018 /**
1019 * ima_measure_critical_data - measure kernel integrity critical data
1020 * @event_label: unique event label for grouping and limiting critical data
1021 * @event_name: event name for the record in the IMA measurement list
1022 * @buf: pointer to buffer data
1023 * @buf_len: length of buffer data (in bytes)
1024 * @hash: measure buffer data hash
1025 * @digest: buffer digest will be written to
1026 * @digest_len: buffer length
1027 *
1028 * Measure data critical to the integrity of the kernel into the IMA log
1029 * and extend the pcr. Examples of critical data could be various data
1030 * structures, policies, and states stored in kernel memory that can
1031 * impact the integrity of the system.
1032 *
1033 * Return: 0 if the buffer has been successfully measured, 1 if the digest
1034 * has been written to the passed location but not added to a measurement entry,
1035 * a negative value otherwise.
1036 */
ima_measure_critical_data(const char * event_label,const char * event_name,const void * buf,size_t buf_len,bool hash,u8 * digest,size_t digest_len)1037 int ima_measure_critical_data(const char *event_label,
1038 const char *event_name,
1039 const void *buf, size_t buf_len,
1040 bool hash, u8 *digest, size_t digest_len)
1041 {
1042 if (!event_name || !event_label || !buf || !buf_len)
1043 return -ENOPARAM;
1044
1045 return process_buffer_measurement(&init_user_ns, NULL, buf, buf_len,
1046 event_name, CRITICAL_DATA, 0,
1047 event_label, hash, digest,
1048 digest_len);
1049 }
1050 EXPORT_SYMBOL_GPL(ima_measure_critical_data);
1051
init_ima(void)1052 static int __init init_ima(void)
1053 {
1054 int error;
1055
1056 ima_appraise_parse_cmdline();
1057 ima_init_template_list();
1058 hash_setup(CONFIG_IMA_DEFAULT_HASH);
1059 error = ima_init();
1060
1061 if (error && strcmp(hash_algo_name[ima_hash_algo],
1062 CONFIG_IMA_DEFAULT_HASH) != 0) {
1063 pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
1064 hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
1065 hash_setup_done = 0;
1066 hash_setup(CONFIG_IMA_DEFAULT_HASH);
1067 error = ima_init();
1068 }
1069
1070 if (error)
1071 return error;
1072
1073 error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier);
1074 if (error)
1075 pr_warn("Couldn't register LSM notifier, error %d\n", error);
1076
1077 if (!error)
1078 ima_update_policy_flags();
1079
1080 return error;
1081 }
1082
1083 late_initcall(init_ima); /* Start IMA after the TPM is available */
1084