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