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