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
30#include "ima.h"
31
32#ifdef CONFIG_IMA_APPRAISE
33int ima_appraise = IMA_APPRAISE_ENFORCE;
34#else
35int ima_appraise;
36#endif
37
38int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1;
39static int hash_setup_done;
40
41static struct notifier_block ima_lsm_policy_notifier = {
42 .notifier_call = ima_lsm_policy_change,
43};
44
45static 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(array: hash_algo_name, n: HASH_ALGO__LAST, string: str);
67 if (i < 0) {
68 pr_err("invalid hash algorithm \"%s\"", str);
69 return 1;
70 }
71
72 ima_hash_algo = i;
73out:
74 hash_setup_done = 1;
75 return 1;
76}
77__setup("ima_hash=", hash_setup);
78
79enum 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 */
85static 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 || func == MMAP_CHECK_REQPROT) &&
93 mapping_writably_mapped(mapping: file->f_mapping)) {
94 rc = -ETXTBSY;
95 inode = file_inode(f: file);
96
97 if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */
98 *pathname = ima_d_path(path: &file->f_path, pathbuf,
99 filename);
100 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, fname: *pathname,
101 op: "mmap_file", cause: "mmapped_writers", result: rc, info: 0);
102 }
103 return rc;
104}
105
106/*
107 * ima_rdwr_violation_check
108 *
109 * Only invalidate the PCR for measured files:
110 * - Opening a file for write when already open for read,
111 * results in a time of measure, time of use (ToMToU) error.
112 * - Opening a file for read when already open for write,
113 * could result in a file measurement error.
114 *
115 */
116static void ima_rdwr_violation_check(struct file *file,
117 struct ima_iint_cache *iint,
118 int must_measure,
119 char **pathbuf,
120 const char **pathname,
121 char *filename)
122{
123 struct inode *inode = file_inode(f: file);
124 fmode_t mode = file->f_mode;
125 bool send_tomtou = false, send_writers = false;
126
127 if (mode & FMODE_WRITE) {
128 if (atomic_read(v: &inode->i_readcount) && IS_IMA(inode)) {
129 if (!iint)
130 iint = ima_iint_find(inode);
131 /* IMA_MEASURE is set from reader side */
132 if (iint && test_bit(IMA_MUST_MEASURE,
133 &iint->atomic_flags))
134 send_tomtou = true;
135 }
136 } else {
137 if (must_measure)
138 set_bit(IMA_MUST_MEASURE, addr: &iint->atomic_flags);
139 if (inode_is_open_for_write(inode) && must_measure)
140 send_writers = true;
141 }
142
143 if (!send_tomtou && !send_writers)
144 return;
145
146 *pathname = ima_d_path(path: &file->f_path, pathbuf, filename);
147
148 if (send_tomtou)
149 ima_add_violation(file, filename: *pathname, iint,
150 op: "invalid_pcr", cause: "ToMToU");
151 if (send_writers)
152 ima_add_violation(file, filename: *pathname, iint,
153 op: "invalid_pcr", cause: "open_writers");
154}
155
156static void ima_check_last_writer(struct ima_iint_cache *iint,
157 struct inode *inode, struct file *file)
158{
159 fmode_t mode = file->f_mode;
160 bool update;
161
162 if (!(mode & FMODE_WRITE))
163 return;
164
165 mutex_lock(&iint->mutex);
166 if (atomic_read(v: &inode->i_writecount) == 1) {
167 struct kstat stat;
168
169 update = test_and_clear_bit(IMA_UPDATE_XATTR,
170 addr: &iint->atomic_flags);
171 if ((iint->flags & IMA_NEW_FILE) ||
172 vfs_getattr_nosec(&file->f_path, &stat,
173 STATX_CHANGE_COOKIE,
174 AT_STATX_SYNC_AS_STAT) ||
175 !(stat.result_mask & STATX_CHANGE_COOKIE) ||
176 stat.change_cookie != iint->version) {
177 iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
178 iint->measured_pcrs = 0;
179 if (update)
180 ima_update_xattr(iint, file);
181 }
182 }
183 mutex_unlock(lock: &iint->mutex);
184}
185
186/**
187 * ima_file_free - called on __fput()
188 * @file: pointer to file structure being freed
189 *
190 * Flag files that changed, based on i_version
191 */
192static void ima_file_free(struct file *file)
193{
194 struct inode *inode = file_inode(f: file);
195 struct ima_iint_cache *iint;
196
197 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
198 return;
199
200 iint = ima_iint_find(inode);
201 if (!iint)
202 return;
203
204 ima_check_last_writer(iint, inode, file);
205}
206
207static int process_measurement(struct file *file, const struct cred *cred,
208 u32 secid, char *buf, loff_t size, int mask,
209 enum ima_hooks func)
210{
211 struct inode *backing_inode, *inode = file_inode(f: file);
212 struct ima_iint_cache *iint = NULL;
213 struct ima_template_desc *template_desc = NULL;
214 char *pathbuf = NULL;
215 char filename[NAME_MAX];
216 const char *pathname = NULL;
217 int rc = 0, action, must_appraise = 0;
218 int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
219 struct evm_ima_xattr_data *xattr_value = NULL;
220 struct modsig *modsig = NULL;
221 int xattr_len = 0;
222 bool violation_check;
223 enum hash_algo hash_algo;
224 unsigned int allowed_algos = 0;
225
226 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
227 return 0;
228
229 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action
230 * bitmask based on the appraise/audit/measurement policy.
231 * Included is the appraise submask.
232 */
233 action = ima_get_action(idmap: file_mnt_idmap(file), inode, cred, secid,
234 mask, func, pcr: &pcr, template_desc: &template_desc, NULL,
235 allowed_algos: &allowed_algos);
236 violation_check = ((func == FILE_CHECK || func == MMAP_CHECK ||
237 func == MMAP_CHECK_REQPROT) &&
238 (ima_policy_flag & IMA_MEASURE));
239 if (!action && !violation_check)
240 return 0;
241
242 must_appraise = action & IMA_APPRAISE;
243
244 /* Is the appraise rule hook specific? */
245 if (action & IMA_FILE_APPRAISE)
246 func = FILE_CHECK;
247
248 inode_lock(inode);
249
250 if (action) {
251 iint = ima_inode_get(inode);
252 if (!iint)
253 rc = -ENOMEM;
254 }
255
256 if (!rc && violation_check)
257 ima_rdwr_violation_check(file, iint, must_measure: action & IMA_MEASURE,
258 pathbuf: &pathbuf, pathname: &pathname, filename);
259
260 inode_unlock(inode);
261
262 if (rc)
263 goto out;
264 if (!action)
265 goto out;
266
267 mutex_lock(&iint->mutex);
268
269 if (test_and_clear_bit(IMA_CHANGE_ATTR, addr: &iint->atomic_flags))
270 /* reset appraisal flags if ima_inode_post_setattr was called */
271 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED |
272 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK |
273 IMA_NONACTION_FLAGS);
274
275 /*
276 * Re-evaulate the file if either the xattr has changed or the
277 * kernel has no way of detecting file change on the filesystem.
278 * (Limited to privileged mounted filesystems.)
279 */
280 if (test_and_clear_bit(IMA_CHANGE_XATTR, addr: &iint->atomic_flags) ||
281 ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) &&
282 !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) &&
283 !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) {
284 iint->flags &= ~IMA_DONE_MASK;
285 iint->measured_pcrs = 0;
286 }
287
288 /* Detect and re-evaluate changes made to the backing file. */
289 backing_inode = d_real_inode(dentry: file_dentry(file));
290 if (backing_inode != inode &&
291 (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) {
292 if (!IS_I_VERSION(backing_inode) ||
293 backing_inode->i_sb->s_dev != iint->real_dev ||
294 backing_inode->i_ino != iint->real_ino ||
295 !inode_eq_iversion(inode: backing_inode, old: iint->version)) {
296 iint->flags &= ~IMA_DONE_MASK;
297 iint->measured_pcrs = 0;
298 }
299 }
300
301 /* Determine if already appraised/measured based on bitmask
302 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED,
303 * IMA_AUDIT, IMA_AUDITED)
304 */
305 iint->flags |= action;
306 action &= IMA_DO_MASK;
307 action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1);
308
309 /* If target pcr is already measured, unset IMA_MEASURE action */
310 if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr)))
311 action ^= IMA_MEASURE;
312
313 /* HASH sets the digital signature and update flags, nothing else */
314 if ((action & IMA_HASH) &&
315 !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) {
316 xattr_len = ima_read_xattr(dentry: file_dentry(file),
317 xattr_value: &xattr_value, xattr_len);
318 if ((xattr_value && xattr_len > 2) &&
319 (xattr_value->type == EVM_IMA_XATTR_DIGSIG))
320 set_bit(IMA_DIGSIG, addr: &iint->atomic_flags);
321 iint->flags |= IMA_HASHED;
322 action ^= IMA_HASH;
323 set_bit(IMA_UPDATE_XATTR, addr: &iint->atomic_flags);
324 }
325
326 /* Nothing to do, just return existing appraised status */
327 if (!action) {
328 if (must_appraise) {
329 rc = mmap_violation_check(func, file, pathbuf: &pathbuf,
330 pathname: &pathname, filename);
331 if (!rc)
332 rc = ima_get_cache_status(iint, func);
333 }
334 goto out_locked;
335 }
336
337 if ((action & IMA_APPRAISE_SUBMASK) ||
338 strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) {
339 /* read 'security.ima' */
340 xattr_len = ima_read_xattr(dentry: file_dentry(file),
341 xattr_value: &xattr_value, xattr_len);
342
343 /*
344 * Read the appended modsig if allowed by the policy, and allow
345 * an additional measurement list entry, if needed, based on the
346 * template format and whether the file was already measured.
347 */
348 if (iint->flags & IMA_MODSIG_ALLOWED) {
349 rc = ima_read_modsig(func, buf, buf_len: size, modsig: &modsig);
350
351 if (!rc && ima_template_has_modsig(ima_template: template_desc) &&
352 iint->flags & IMA_MEASURED)
353 action |= IMA_MEASURE;
354 }
355 }
356
357 hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
358
359 rc = ima_collect_measurement(iint, file, buf, size, algo: hash_algo, modsig);
360 if (rc != 0 && rc != -EBADF && rc != -EINVAL)
361 goto out_locked;
362
363 if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */
364 pathname = ima_d_path(path: &file->f_path, pathbuf: &pathbuf, filename);
365
366 if (action & IMA_MEASURE)
367 ima_store_measurement(iint, file, filename: pathname,
368 xattr_value, xattr_len, modsig, pcr,
369 template_desc);
370 if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) {
371 rc = ima_check_blacklist(iint, modsig, pcr);
372 if (rc != -EPERM) {
373 inode_lock(inode);
374 rc = ima_appraise_measurement(func, iint, file,
375 filename: pathname, xattr_value,
376 xattr_len, modsig);
377 inode_unlock(inode);
378 }
379 if (!rc)
380 rc = mmap_violation_check(func, file, pathbuf: &pathbuf,
381 pathname: &pathname, filename);
382 }
383 if (action & IMA_AUDIT)
384 ima_audit_measurement(iint, filename: pathname);
385
386 if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO))
387 rc = 0;
388
389 /* Ensure the digest was generated using an allowed algorithm */
390 if (rc == 0 && must_appraise && allowed_algos != 0 &&
391 (allowed_algos & (1U << hash_algo)) == 0) {
392 rc = -EACCES;
393
394 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode: file_inode(f: file),
395 fname: pathname, op: "collect_data",
396 cause: "denied-hash-algorithm", result: rc, info: 0);
397 }
398out_locked:
399 if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) &&
400 !(iint->flags & IMA_NEW_FILE))
401 rc = -EACCES;
402 mutex_unlock(lock: &iint->mutex);
403 kfree(objp: xattr_value);
404 ima_free_modsig(modsig);
405out:
406 if (pathbuf)
407 __putname(pathbuf);
408 if (must_appraise) {
409 if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE))
410 return -EACCES;
411 if (file->f_mode & FMODE_WRITE)
412 set_bit(IMA_UPDATE_XATTR, addr: &iint->atomic_flags);
413 }
414 return 0;
415}
416
417/**
418 * ima_file_mmap - based on policy, collect/store measurement.
419 * @file: pointer to the file to be measured (May be NULL)
420 * @reqprot: protection requested by the application
421 * @prot: protection that will be applied by the kernel
422 * @flags: operational flags
423 *
424 * Measure files being mmapped executable based on the ima_must_measure()
425 * policy decision.
426 *
427 * On success return 0. On integrity appraisal error, assuming the file
428 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
429 */
430static int ima_file_mmap(struct file *file, unsigned long reqprot,
431 unsigned long prot, unsigned long flags)
432{
433 u32 secid;
434 int ret;
435
436 if (!file)
437 return 0;
438
439 security_current_getsecid_subj(secid: &secid);
440
441 if (reqprot & PROT_EXEC) {
442 ret = process_measurement(file, current_cred(), secid, NULL,
443 size: 0, MAY_EXEC, func: MMAP_CHECK_REQPROT);
444 if (ret)
445 return ret;
446 }
447
448 if (prot & PROT_EXEC)
449 return process_measurement(file, current_cred(), secid, NULL,
450 size: 0, MAY_EXEC, func: MMAP_CHECK);
451
452 return 0;
453}
454
455/**
456 * ima_file_mprotect - based on policy, limit mprotect change
457 * @vma: vm_area_struct protection is set to
458 * @reqprot: protection requested by the application
459 * @prot: protection that will be applied by the kernel
460 *
461 * Files can be mmap'ed read/write and later changed to execute to circumvent
462 * IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore
463 * would be taken before i_mutex), files can not be measured or appraised at
464 * this point. Eliminate this integrity gap by denying the mprotect
465 * PROT_EXECUTE change, if an mmap appraise policy rule exists.
466 *
467 * On mprotect change success, return 0. On failure, return -EACESS.
468 */
469static int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
470 unsigned long prot)
471{
472 struct ima_template_desc *template = NULL;
473 struct file *file;
474 char filename[NAME_MAX];
475 char *pathbuf = NULL;
476 const char *pathname = NULL;
477 struct inode *inode;
478 int result = 0;
479 int action;
480 u32 secid;
481 int pcr;
482
483 /* Is mprotect making an mmap'ed file executable? */
484 if (!(ima_policy_flag & IMA_APPRAISE) || !vma->vm_file ||
485 !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC))
486 return 0;
487
488 security_current_getsecid_subj(secid: &secid);
489 inode = file_inode(f: vma->vm_file);
490 action = ima_get_action(idmap: file_mnt_idmap(file: vma->vm_file), inode,
491 current_cred(), secid, MAY_EXEC, func: MMAP_CHECK,
492 pcr: &pcr, template_desc: &template, NULL, NULL);
493 action |= ima_get_action(idmap: file_mnt_idmap(file: vma->vm_file), inode,
494 current_cred(), secid, MAY_EXEC,
495 func: MMAP_CHECK_REQPROT, pcr: &pcr, template_desc: &template, NULL,
496 NULL);
497
498 /* Is the mmap'ed file in policy? */
499 if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK)))
500 return 0;
501
502 if (action & IMA_APPRAISE_SUBMASK)
503 result = -EPERM;
504
505 file = vma->vm_file;
506 pathname = ima_d_path(path: &file->f_path, pathbuf: &pathbuf, filename);
507 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, fname: pathname,
508 op: "collect_data", cause: "failed-mprotect", result, info: 0);
509 if (pathbuf)
510 __putname(pathbuf);
511
512 return result;
513}
514
515/**
516 * ima_bprm_check - based on policy, collect/store measurement.
517 * @bprm: contains the linux_binprm structure
518 *
519 * The OS protects against an executable file, already open for write,
520 * from being executed in deny_write_access() and an executable file,
521 * already open for execute, from being modified in get_write_access().
522 * So we can be certain that what we verify and measure here is actually
523 * what is being executed.
524 *
525 * On success return 0. On integrity appraisal error, assuming the file
526 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
527 */
528static int ima_bprm_check(struct linux_binprm *bprm)
529{
530 int ret;
531 u32 secid;
532
533 security_current_getsecid_subj(secid: &secid);
534 ret = process_measurement(file: bprm->file, current_cred(), secid, NULL, size: 0,
535 MAY_EXEC, func: BPRM_CHECK);
536 if (ret)
537 return ret;
538
539 security_cred_getsecid(c: bprm->cred, secid: &secid);
540 return process_measurement(file: bprm->file, cred: bprm->cred, secid, NULL, size: 0,
541 MAY_EXEC, func: CREDS_CHECK);
542}
543
544/**
545 * ima_file_check - based on policy, collect/store measurement.
546 * @file: pointer to the file to be measured
547 * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND
548 *
549 * Measure files based on the ima_must_measure() policy decision.
550 *
551 * On success return 0. On integrity appraisal error, assuming the file
552 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
553 */
554static int ima_file_check(struct file *file, int mask)
555{
556 u32 secid;
557
558 security_current_getsecid_subj(secid: &secid);
559 return process_measurement(file, current_cred(), secid, NULL, size: 0,
560 mask: mask & (MAY_READ | MAY_WRITE | MAY_EXEC |
561 MAY_APPEND), func: FILE_CHECK);
562}
563
564static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf,
565 size_t buf_size)
566{
567 struct ima_iint_cache *iint = NULL, tmp_iint;
568 int rc, hash_algo;
569
570 if (ima_policy_flag) {
571 iint = ima_iint_find(inode);
572 if (iint)
573 mutex_lock(&iint->mutex);
574 }
575
576 if ((!iint || !(iint->flags & IMA_COLLECTED)) && file) {
577 if (iint)
578 mutex_unlock(lock: &iint->mutex);
579
580 memset(&tmp_iint, 0, sizeof(tmp_iint));
581 mutex_init(&tmp_iint.mutex);
582
583 rc = ima_collect_measurement(iint: &tmp_iint, file, NULL, size: 0,
584 algo: ima_hash_algo, NULL);
585 if (rc < 0) {
586 /* ima_hash could be allocated in case of failure. */
587 if (rc != -ENOMEM)
588 kfree(objp: tmp_iint.ima_hash);
589
590 return -EOPNOTSUPP;
591 }
592
593 iint = &tmp_iint;
594 mutex_lock(&iint->mutex);
595 }
596
597 if (!iint)
598 return -EOPNOTSUPP;
599
600 /*
601 * ima_file_hash can be called when ima_collect_measurement has still
602 * not been called, we might not always have a hash.
603 */
604 if (!iint->ima_hash || !(iint->flags & IMA_COLLECTED)) {
605 mutex_unlock(lock: &iint->mutex);
606 return -EOPNOTSUPP;
607 }
608
609 if (buf) {
610 size_t copied_size;
611
612 copied_size = min_t(size_t, iint->ima_hash->length, buf_size);
613 memcpy(buf, iint->ima_hash->digest, copied_size);
614 }
615 hash_algo = iint->ima_hash->algo;
616 mutex_unlock(lock: &iint->mutex);
617
618 if (iint == &tmp_iint)
619 kfree(objp: iint->ima_hash);
620
621 return hash_algo;
622}
623
624/**
625 * ima_file_hash - return a measurement of the file
626 * @file: pointer to the file
627 * @buf: buffer in which to store the hash
628 * @buf_size: length of the buffer
629 *
630 * On success, return the hash algorithm (as defined in the enum hash_algo).
631 * If buf is not NULL, this function also outputs the hash into buf.
632 * If the hash is larger than buf_size, then only buf_size bytes will be copied.
633 * It generally just makes sense to pass a buffer capable of holding the largest
634 * possible hash: IMA_MAX_DIGEST_SIZE.
635 * The file hash returned is based on the entire file, including the appended
636 * signature.
637 *
638 * If the measurement cannot be performed, return -EOPNOTSUPP.
639 * If the parameters are incorrect, return -EINVAL.
640 */
641int ima_file_hash(struct file *file, char *buf, size_t buf_size)
642{
643 if (!file)
644 return -EINVAL;
645
646 return __ima_inode_hash(inode: file_inode(f: file), file, buf, buf_size);
647}
648EXPORT_SYMBOL_GPL(ima_file_hash);
649
650/**
651 * ima_inode_hash - return the stored measurement if the inode has been hashed
652 * and is in the iint cache.
653 * @inode: pointer to the inode
654 * @buf: buffer in which to store the hash
655 * @buf_size: length of the buffer
656 *
657 * On success, return the hash algorithm (as defined in the enum hash_algo).
658 * If buf is not NULL, this function also outputs the hash into buf.
659 * If the hash is larger than buf_size, then only buf_size bytes will be copied.
660 * It generally just makes sense to pass a buffer capable of holding the largest
661 * possible hash: IMA_MAX_DIGEST_SIZE.
662 * The hash returned is based on the entire contents, including the appended
663 * signature.
664 *
665 * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
666 * If the parameters are incorrect, return -EINVAL.
667 */
668int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size)
669{
670 if (!inode)
671 return -EINVAL;
672
673 return __ima_inode_hash(inode, NULL, buf, buf_size);
674}
675EXPORT_SYMBOL_GPL(ima_inode_hash);
676
677/**
678 * ima_post_create_tmpfile - mark newly created tmpfile as new
679 * @idmap: idmap of the mount the inode was found from
680 * @inode: inode of the newly created tmpfile
681 *
682 * No measuring, appraising or auditing of newly created tmpfiles is needed.
683 * Skip calling process_measurement(), but indicate which newly, created
684 * tmpfiles are in policy.
685 */
686static void ima_post_create_tmpfile(struct mnt_idmap *idmap,
687 struct inode *inode)
688
689{
690 struct ima_iint_cache *iint;
691 int must_appraise;
692
693 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
694 return;
695
696 must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS,
697 func: FILE_CHECK);
698 if (!must_appraise)
699 return;
700
701 /* Nothing to do if we can't allocate memory */
702 iint = ima_inode_get(inode);
703 if (!iint)
704 return;
705
706 /* needed for writing the security xattrs */
707 set_bit(IMA_UPDATE_XATTR, addr: &iint->atomic_flags);
708 iint->ima_file_status = INTEGRITY_PASS;
709}
710
711/**
712 * ima_post_path_mknod - mark as a new inode
713 * @idmap: idmap of the mount the inode was found from
714 * @dentry: newly created dentry
715 *
716 * Mark files created via the mknodat syscall as new, so that the
717 * file data can be written later.
718 */
719static void ima_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry)
720{
721 struct ima_iint_cache *iint;
722 struct inode *inode = dentry->d_inode;
723 int must_appraise;
724
725 if (!ima_policy_flag || !S_ISREG(inode->i_mode))
726 return;
727
728 must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS,
729 func: FILE_CHECK);
730 if (!must_appraise)
731 return;
732
733 /* Nothing to do if we can't allocate memory */
734 iint = ima_inode_get(inode);
735 if (!iint)
736 return;
737
738 /* needed for re-opening empty files */
739 iint->flags |= IMA_NEW_FILE;
740}
741
742/**
743 * ima_read_file - pre-measure/appraise hook decision based on policy
744 * @file: pointer to the file to be measured/appraised/audit
745 * @read_id: caller identifier
746 * @contents: whether a subsequent call will be made to ima_post_read_file()
747 *
748 * Permit reading a file based on policy. The policy rules are written
749 * in terms of the policy identifier. Appraising the integrity of
750 * a file requires a file descriptor.
751 *
752 * For permission return 0, otherwise return -EACCES.
753 */
754static int ima_read_file(struct file *file, enum kernel_read_file_id read_id,
755 bool contents)
756{
757 enum ima_hooks func;
758 u32 secid;
759
760 /*
761 * Do devices using pre-allocated memory run the risk of the
762 * firmware being accessible to the device prior to the completion
763 * of IMA's signature verification any more than when using two
764 * buffers? It may be desirable to include the buffer address
765 * in this API and walk all the dma_map_single() mappings to check.
766 */
767
768 /*
769 * There will be a call made to ima_post_read_file() with
770 * a filled buffer, so we don't need to perform an extra
771 * read early here.
772 */
773 if (contents)
774 return 0;
775
776 /* Read entire file for all partial reads. */
777 func = read_idmap[read_id] ?: FILE_CHECK;
778 security_current_getsecid_subj(secid: &secid);
779 return process_measurement(file, current_cred(), secid, NULL,
780 size: 0, MAY_READ, func);
781}
782
783const int read_idmap[READING_MAX_ID] = {
784 [READING_FIRMWARE] = FIRMWARE_CHECK,
785 [READING_MODULE] = MODULE_CHECK,
786 [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
787 [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
788 [READING_POLICY] = POLICY_CHECK
789};
790
791/**
792 * ima_post_read_file - in memory collect/appraise/audit measurement
793 * @file: pointer to the file to be measured/appraised/audit
794 * @buf: pointer to in memory file contents
795 * @size: size of in memory file contents
796 * @read_id: caller identifier
797 *
798 * Measure/appraise/audit in memory file based on policy. Policy rules
799 * are written in terms of a policy identifier.
800 *
801 * On success return 0. On integrity appraisal error, assuming the file
802 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
803 */
804static int ima_post_read_file(struct file *file, char *buf, loff_t size,
805 enum kernel_read_file_id read_id)
806{
807 enum ima_hooks func;
808 u32 secid;
809
810 /* permit signed certs */
811 if (!file && read_id == READING_X509_CERTIFICATE)
812 return 0;
813
814 if (!file || !buf || size == 0) { /* should never happen */
815 if (ima_appraise & IMA_APPRAISE_ENFORCE)
816 return -EACCES;
817 return 0;
818 }
819
820 func = read_idmap[read_id] ?: FILE_CHECK;
821 security_current_getsecid_subj(secid: &secid);
822 return process_measurement(file, current_cred(), secid, buf, size,
823 MAY_READ, func);
824}
825
826/**
827 * ima_load_data - appraise decision based on policy
828 * @id: kernel load data caller identifier
829 * @contents: whether the full contents will be available in a later
830 * call to ima_post_load_data().
831 *
832 * Callers of this LSM hook can not measure, appraise, or audit the
833 * data provided by userspace. Enforce policy rules requiring a file
834 * signature (eg. kexec'ed kernel image).
835 *
836 * For permission return 0, otherwise return -EACCES.
837 */
838static int ima_load_data(enum kernel_load_data_id id, bool contents)
839{
840 bool ima_enforce, sig_enforce;
841
842 ima_enforce =
843 (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE;
844
845 switch (id) {
846 case LOADING_KEXEC_IMAGE:
847 if (IS_ENABLED(CONFIG_KEXEC_SIG)
848 && arch_ima_get_secureboot()) {
849 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
850 return -EACCES;
851 }
852
853 if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) {
854 pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n");
855 return -EACCES; /* INTEGRITY_UNKNOWN */
856 }
857 break;
858 case LOADING_FIRMWARE:
859 if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE) && !contents) {
860 pr_err("Prevent firmware sysfs fallback loading.\n");
861 return -EACCES; /* INTEGRITY_UNKNOWN */
862 }
863 break;
864 case LOADING_MODULE:
865 sig_enforce = is_module_sig_enforced();
866
867 if (ima_enforce && (!sig_enforce
868 && (ima_appraise & IMA_APPRAISE_MODULES))) {
869 pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n");
870 return -EACCES; /* INTEGRITY_UNKNOWN */
871 }
872 break;
873 default:
874 break;
875 }
876 return 0;
877}
878
879/**
880 * ima_post_load_data - appraise decision based on policy
881 * @buf: pointer to in memory file contents
882 * @size: size of in memory file contents
883 * @load_id: kernel load data caller identifier
884 * @description: @load_id-specific description of contents
885 *
886 * Measure/appraise/audit in memory buffer based on policy. Policy rules
887 * are written in terms of a policy identifier.
888 *
889 * On success return 0. On integrity appraisal error, assuming the file
890 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES.
891 */
892static int ima_post_load_data(char *buf, loff_t size,
893 enum kernel_load_data_id load_id,
894 char *description)
895{
896 if (load_id == LOADING_FIRMWARE) {
897 if ((ima_appraise & IMA_APPRAISE_FIRMWARE) &&
898 (ima_appraise & IMA_APPRAISE_ENFORCE)) {
899 pr_err("Prevent firmware loading_store.\n");
900 return -EACCES; /* INTEGRITY_UNKNOWN */
901 }
902 return 0;
903 }
904
905 return 0;
906}
907
908/**
909 * process_buffer_measurement - Measure the buffer or the buffer data hash
910 * @idmap: idmap of the mount the inode was found from
911 * @inode: inode associated with the object being measured (NULL for KEY_CHECK)
912 * @buf: pointer to the buffer that needs to be added to the log.
913 * @size: size of buffer(in bytes).
914 * @eventname: event name to be used for the buffer entry.
915 * @func: IMA hook
916 * @pcr: pcr to extend the measurement
917 * @func_data: func specific data, may be NULL
918 * @buf_hash: measure buffer data hash
919 * @digest: buffer digest will be written to
920 * @digest_len: buffer length
921 *
922 * Based on policy, either the buffer data or buffer data hash is measured
923 *
924 * Return: 0 if the buffer has been successfully measured, 1 if the digest
925 * has been written to the passed location but not added to a measurement entry,
926 * a negative value otherwise.
927 */
928int process_buffer_measurement(struct mnt_idmap *idmap,
929 struct inode *inode, const void *buf, int size,
930 const char *eventname, enum ima_hooks func,
931 int pcr, const char *func_data,
932 bool buf_hash, u8 *digest, size_t digest_len)
933{
934 int ret = 0;
935 const char *audit_cause = "ENOMEM";
936 struct ima_template_entry *entry = NULL;
937 struct ima_iint_cache iint = {};
938 struct ima_event_data event_data = {.iint = &iint,
939 .filename = eventname,
940 .buf = buf,
941 .buf_len = size};
942 struct ima_template_desc *template;
943 struct ima_max_digest_data hash;
944 char digest_hash[IMA_MAX_DIGEST_SIZE];
945 int digest_hash_len = hash_digest_size[ima_hash_algo];
946 int violation = 0;
947 int action = 0;
948 u32 secid;
949
950 if (digest && digest_len < digest_hash_len)
951 return -EINVAL;
952
953 if (!ima_policy_flag && !digest)
954 return -ENOENT;
955
956 template = ima_template_desc_buf();
957 if (!template) {
958 ret = -EINVAL;
959 audit_cause = "ima_template_desc_buf";
960 goto out;
961 }
962
963 /*
964 * Both LSM hooks and auxilary based buffer measurements are
965 * based on policy. To avoid code duplication, differentiate
966 * between the LSM hooks and auxilary buffer measurements,
967 * retrieving the policy rule information only for the LSM hook
968 * buffer measurements.
969 */
970 if (func) {
971 security_current_getsecid_subj(secid: &secid);
972 action = ima_get_action(idmap, inode, current_cred(),
973 secid, mask: 0, func, pcr: &pcr, template_desc: &template,
974 func_data, NULL);
975 if (!(action & IMA_MEASURE) && !digest)
976 return -ENOENT;
977 }
978
979 if (!pcr)
980 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
981
982 iint.ima_hash = &hash.hdr;
983 iint.ima_hash->algo = ima_hash_algo;
984 iint.ima_hash->length = hash_digest_size[ima_hash_algo];
985
986 ret = ima_calc_buffer_hash(buf, len: size, hash: iint.ima_hash);
987 if (ret < 0) {
988 audit_cause = "hashing_error";
989 goto out;
990 }
991
992 if (buf_hash) {
993 memcpy(digest_hash, hash.hdr.digest, digest_hash_len);
994
995 ret = ima_calc_buffer_hash(buf: digest_hash, len: digest_hash_len,
996 hash: iint.ima_hash);
997 if (ret < 0) {
998 audit_cause = "hashing_error";
999 goto out;
1000 }
1001
1002 event_data.buf = digest_hash;
1003 event_data.buf_len = digest_hash_len;
1004 }
1005
1006 if (digest)
1007 memcpy(digest, iint.ima_hash->digest, digest_hash_len);
1008
1009 if (!ima_policy_flag || (func && !(action & IMA_MEASURE)))
1010 return 1;
1011
1012 ret = ima_alloc_init_template(event_data: &event_data, entry: &entry, template_desc: template);
1013 if (ret < 0) {
1014 audit_cause = "alloc_entry";
1015 goto out;
1016 }
1017
1018 ret = ima_store_template(entry, violation, NULL, filename: event_data.buf, pcr);
1019 if (ret < 0) {
1020 audit_cause = "store_entry";
1021 ima_free_template_entry(entry);
1022 }
1023
1024out:
1025 if (ret < 0)
1026 integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL, fname: eventname,
1027 op: func_measure_str(func),
1028 cause: audit_cause, result: ret, info: 0, errno: ret);
1029
1030 return ret;
1031}
1032
1033/**
1034 * ima_kexec_cmdline - measure kexec cmdline boot args
1035 * @kernel_fd: file descriptor of the kexec kernel being loaded
1036 * @buf: pointer to buffer
1037 * @size: size of buffer
1038 *
1039 * Buffers can only be measured, not appraised.
1040 */
1041void ima_kexec_cmdline(int kernel_fd, const void *buf, int size)
1042{
1043 struct fd f;
1044
1045 if (!buf || !size)
1046 return;
1047
1048 f = fdget(fd: kernel_fd);
1049 if (!f.file)
1050 return;
1051
1052 process_buffer_measurement(idmap: file_mnt_idmap(file: f.file), inode: file_inode(f: f.file),
1053 buf, size, eventname: "kexec-cmdline", func: KEXEC_CMDLINE, pcr: 0,
1054 NULL, buf_hash: false, NULL, digest_len: 0);
1055 fdput(fd: f);
1056}
1057
1058/**
1059 * ima_measure_critical_data - measure kernel integrity critical data
1060 * @event_label: unique event label for grouping and limiting critical data
1061 * @event_name: event name for the record in the IMA measurement list
1062 * @buf: pointer to buffer data
1063 * @buf_len: length of buffer data (in bytes)
1064 * @hash: measure buffer data hash
1065 * @digest: buffer digest will be written to
1066 * @digest_len: buffer length
1067 *
1068 * Measure data critical to the integrity of the kernel into the IMA log
1069 * and extend the pcr. Examples of critical data could be various data
1070 * structures, policies, and states stored in kernel memory that can
1071 * impact the integrity of the system.
1072 *
1073 * Return: 0 if the buffer has been successfully measured, 1 if the digest
1074 * has been written to the passed location but not added to a measurement entry,
1075 * a negative value otherwise.
1076 */
1077int ima_measure_critical_data(const char *event_label,
1078 const char *event_name,
1079 const void *buf, size_t buf_len,
1080 bool hash, u8 *digest, size_t digest_len)
1081{
1082 if (!event_name || !event_label || !buf || !buf_len)
1083 return -ENOPARAM;
1084
1085 return process_buffer_measurement(idmap: &nop_mnt_idmap, NULL, buf, size: buf_len,
1086 eventname: event_name, func: CRITICAL_DATA, pcr: 0,
1087 func_data: event_label, buf_hash: hash, digest,
1088 digest_len);
1089}
1090EXPORT_SYMBOL_GPL(ima_measure_critical_data);
1091
1092#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
1093
1094/**
1095 * ima_kernel_module_request - Prevent crypto-pkcs1pad(rsa,*) requests
1096 * @kmod_name: kernel module name
1097 *
1098 * Avoid a verification loop where verifying the signature of the modprobe
1099 * binary requires executing modprobe itself. Since the modprobe iint->mutex
1100 * is already held when the signature verification is performed, a deadlock
1101 * occurs as soon as modprobe is executed within the critical region, since
1102 * the same lock cannot be taken again.
1103 *
1104 * This happens when public_key_verify_signature(), in case of RSA algorithm,
1105 * use alg_name to store internal information in order to construct an
1106 * algorithm on the fly, but crypto_larval_lookup() will try to use alg_name
1107 * in order to load a kernel module with same name.
1108 *
1109 * Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules,
1110 * we are safe to fail such module request from crypto_larval_lookup(), and
1111 * avoid the verification loop.
1112 *
1113 * Return: Zero if it is safe to load the kernel module, -EINVAL otherwise.
1114 */
1115static int ima_kernel_module_request(char *kmod_name)
1116{
1117 if (strncmp(kmod_name, "crypto-pkcs1pad(rsa,", 20) == 0)
1118 return -EINVAL;
1119
1120 return 0;
1121}
1122
1123#endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */
1124
1125static int __init init_ima(void)
1126{
1127 int error;
1128
1129 ima_appraise_parse_cmdline();
1130 ima_init_template_list();
1131 hash_setup(CONFIG_IMA_DEFAULT_HASH);
1132 error = ima_init();
1133
1134 if (error && strcmp(hash_algo_name[ima_hash_algo],
1135 CONFIG_IMA_DEFAULT_HASH) != 0) {
1136 pr_info("Allocating %s failed, going to use default hash algorithm %s\n",
1137 hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH);
1138 hash_setup_done = 0;
1139 hash_setup(CONFIG_IMA_DEFAULT_HASH);
1140 error = ima_init();
1141 }
1142
1143 if (error)
1144 return error;
1145
1146 error = register_blocking_lsm_notifier(nb: &ima_lsm_policy_notifier);
1147 if (error)
1148 pr_warn("Couldn't register LSM notifier, error %d\n", error);
1149
1150 if (!error)
1151 ima_update_policy_flags();
1152
1153 return error;
1154}
1155
1156static struct security_hook_list ima_hooks[] __ro_after_init = {
1157 LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
1158 LSM_HOOK_INIT(file_post_open, ima_file_check),
1159 LSM_HOOK_INIT(inode_post_create_tmpfile, ima_post_create_tmpfile),
1160 LSM_HOOK_INIT(file_release, ima_file_free),
1161 LSM_HOOK_INIT(mmap_file, ima_file_mmap),
1162 LSM_HOOK_INIT(file_mprotect, ima_file_mprotect),
1163 LSM_HOOK_INIT(kernel_load_data, ima_load_data),
1164 LSM_HOOK_INIT(kernel_post_load_data, ima_post_load_data),
1165 LSM_HOOK_INIT(kernel_read_file, ima_read_file),
1166 LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file),
1167 LSM_HOOK_INIT(path_post_mknod, ima_post_path_mknod),
1168#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS
1169 LSM_HOOK_INIT(key_post_create_or_update, ima_post_key_create_or_update),
1170#endif
1171#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS
1172 LSM_HOOK_INIT(kernel_module_request, ima_kernel_module_request),
1173#endif
1174 LSM_HOOK_INIT(inode_free_security, ima_inode_free),
1175};
1176
1177static const struct lsm_id ima_lsmid = {
1178 .name = "ima",
1179 .id = LSM_ID_IMA,
1180};
1181
1182static int __init init_ima_lsm(void)
1183{
1184 ima_iintcache_init();
1185 security_add_hooks(hooks: ima_hooks, ARRAY_SIZE(ima_hooks), lsmid: &ima_lsmid);
1186 init_ima_appraise_lsm(lsmid: &ima_lsmid);
1187 return 0;
1188}
1189
1190struct lsm_blob_sizes ima_blob_sizes __ro_after_init = {
1191 .lbs_inode = sizeof(struct ima_iint_cache *),
1192};
1193
1194DEFINE_LSM(ima) = {
1195 .name = "ima",
1196 .init = init_ima_lsm,
1197 .order = LSM_ORDER_LAST,
1198 .blobs = &ima_blob_sizes,
1199};
1200
1201late_initcall(init_ima); /* Start IMA after the TPM is available */
1202

source code of linux/security/integrity/ima/ima_main.c