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