1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2008 IBM Corporation
4 *
5 * Author: Mimi Zohar <zohar@us.ibm.com>
6 *
7 * File: ima_api.c
8 *	Implements must_appraise_or_measure, collect_measurement,
9 *	appraise_measurement, store_measurement and store_template.
10 */
11#include <linux/slab.h>
12#include <linux/file.h>
13#include <linux/fs.h>
14#include <linux/xattr.h>
15#include <linux/evm.h>
16#include <linux/fsverity.h>
17
18#include "ima.h"
19
20/*
21 * ima_free_template_entry - free an existing template entry
22 */
23void ima_free_template_entry(struct ima_template_entry *entry)
24{
25	int i;
26
27	for (i = 0; i < entry->template_desc->num_fields; i++)
28		kfree(entry->template_data[i].data);
29
30	kfree(entry->digests);
31	kfree(entry);
32}
33
34/*
35 * ima_alloc_init_template - create and initialize a new template entry
36 */
37int ima_alloc_init_template(struct ima_event_data *event_data,
38			    struct ima_template_entry **entry,
39			    struct ima_template_desc *desc)
40{
41	struct ima_template_desc *template_desc;
42	struct tpm_digest *digests;
43	int i, result = 0;
44
45	if (desc)
46		template_desc = desc;
47	else
48		template_desc = ima_template_desc_current();
49
50	*entry = kzalloc(struct_size(*entry, template_data,
51				     template_desc->num_fields), GFP_NOFS);
52	if (!*entry)
53		return -ENOMEM;
54
55	digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
56			  sizeof(*digests), GFP_NOFS);
57	if (!digests) {
58		kfree(*entry);
59		*entry = NULL;
60		return -ENOMEM;
61	}
62
63	(*entry)->digests = digests;
64	(*entry)->template_desc = template_desc;
65	for (i = 0; i < template_desc->num_fields; i++) {
66		const struct ima_template_field *field =
67			template_desc->fields[i];
68		u32 len;
69
70		result = field->field_init(event_data,
71					   &((*entry)->template_data[i]));
72		if (result != 0)
73			goto out;
74
75		len = (*entry)->template_data[i].len;
76		(*entry)->template_data_len += sizeof(len);
77		(*entry)->template_data_len += len;
78	}
79	return 0;
80out:
81	ima_free_template_entry(*entry);
82	*entry = NULL;
83	return result;
84}
85
86/*
87 * ima_store_template - store ima template measurements
88 *
89 * Calculate the hash of a template entry, add the template entry
90 * to an ordered list of measurement entries maintained inside the kernel,
91 * and also update the aggregate integrity value (maintained inside the
92 * configured TPM PCR) over the hashes of the current list of measurement
93 * entries.
94 *
95 * Applications retrieve the current kernel-held measurement list through
96 * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
97 * TPM PCR (called quote) can be retrieved using a TPM user space library
98 * and is used to validate the measurement list.
99 *
100 * Returns 0 on success, error code otherwise
101 */
102int ima_store_template(struct ima_template_entry *entry,
103		       int violation, struct inode *inode,
104		       const unsigned char *filename, int pcr)
105{
106	static const char op[] = "add_template_measure";
107	static const char audit_cause[] = "hashing_error";
108	char *template_name = entry->template_desc->name;
109	int result;
110
111	if (!violation) {
112		result = ima_calc_field_array_hash(&entry->template_data[0],
113						   entry);
114		if (result < 0) {
115			integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
116					    template_name, op,
117					    audit_cause, result, 0);
118			return result;
119		}
120	}
121	entry->pcr = pcr;
122	result = ima_add_template_entry(entry, violation, op, inode, filename);
123	return result;
124}
125
126/*
127 * ima_add_violation - add violation to measurement list.
128 *
129 * Violations are flagged in the measurement list with zero hash values.
130 * By extending the PCR with 0xFF's instead of with zeroes, the PCR
131 * value is invalidated.
132 */
133void ima_add_violation(struct file *file, const unsigned char *filename,
134		       struct ima_iint_cache *iint, const char *op,
135		       const char *cause)
136{
137	struct ima_template_entry *entry;
138	struct inode *inode = file_inode(file);
139	struct ima_event_data event_data = { .iint = iint,
140					     .file = file,
141					     .filename = filename,
142					     .violation = cause };
143	int violation = 1;
144	int result;
145
146	/* can overflow, only indicator */
147	atomic_long_inc(&ima_htable.violations);
148
149	result = ima_alloc_init_template(&event_data, &entry, NULL);
150	if (result < 0) {
151		result = -ENOMEM;
152		goto err_out;
153	}
154	result = ima_store_template(entry, violation, inode,
155				    filename, CONFIG_IMA_MEASURE_PCR_IDX);
156	if (result < 0)
157		ima_free_template_entry(entry);
158err_out:
159	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
160			    op, cause, result, 0);
161}
162
163/**
164 * ima_get_action - appraise & measure decision based on policy.
165 * @idmap: idmap of the mount the inode was found from
166 * @inode: pointer to the inode associated with the object being validated
167 * @cred: pointer to credentials structure to validate
168 * @secid: secid of the task being validated
169 * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
170 *        MAY_APPEND)
171 * @func: caller identifier
172 * @pcr: pointer filled in if matched measure policy sets pcr=
173 * @template_desc: pointer filled in if matched measure policy sets template=
174 * @func_data: func specific data, may be NULL
175 * @allowed_algos: allowlist of hash algorithms for the IMA xattr
176 *
177 * The policy is defined in terms of keypairs:
178 *		subj=, obj=, type=, func=, mask=, fsmagic=
179 *	subj,obj, and type: are LSM specific.
180 *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
181 *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA | SETXATTR_CHECK
182 *	| MMAP_CHECK_REQPROT
183 *	mask: contains the permission mask
184 *	fsmagic: hex value
185 *
186 * Returns IMA_MEASURE, IMA_APPRAISE mask.
187 *
188 */
189int ima_get_action(struct mnt_idmap *idmap, struct inode *inode,
190		   const struct cred *cred, u32 secid, int mask,
191		   enum ima_hooks func, int *pcr,
192		   struct ima_template_desc **template_desc,
193		   const char *func_data, unsigned int *allowed_algos)
194{
195	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
196
197	flags &= ima_policy_flag;
198
199	return ima_match_policy(idmap, inode, cred, secid, func, mask,
200				flags, pcr, template_desc, func_data,
201				allowed_algos);
202}
203
204static bool ima_get_verity_digest(struct ima_iint_cache *iint,
205				  struct inode *inode,
206				  struct ima_max_digest_data *hash)
207{
208	enum hash_algo alg;
209	int digest_len;
210
211	/*
212	 * On failure, 'measure' policy rules will result in a file data
213	 * hash containing 0's.
214	 */
215	digest_len = fsverity_get_digest(inode, hash->digest, NULL, &alg);
216	if (digest_len == 0)
217		return false;
218
219	/*
220	 * Unlike in the case of actually calculating the file hash, in
221	 * the fsverity case regardless of the hash algorithm, return
222	 * the verity digest to be included in the measurement list. A
223	 * mismatch between the verity algorithm and the xattr signature
224	 * algorithm, if one exists, will be detected later.
225	 */
226	hash->hdr.algo = alg;
227	hash->hdr.length = digest_len;
228	return true;
229}
230
231/*
232 * ima_collect_measurement - collect file measurement
233 *
234 * Calculate the file hash, if it doesn't already exist,
235 * storing the measurement and i_version in the iint.
236 *
237 * Must be called with iint->mutex held.
238 *
239 * Return 0 on success, error code otherwise
240 */
241int ima_collect_measurement(struct ima_iint_cache *iint, struct file *file,
242			    void *buf, loff_t size, enum hash_algo algo,
243			    struct modsig *modsig)
244{
245	const char *audit_cause = "failed";
246	struct inode *inode = file_inode(file);
247	struct inode *real_inode = d_real_inode(file_dentry(file));
248	const char *filename = file->f_path.dentry->d_name.name;
249	struct ima_max_digest_data hash;
250	struct kstat stat;
251	int result = 0;
252	int length;
253	void *tmpbuf;
254	u64 i_version = 0;
255
256	/*
257	 * Always collect the modsig, because IMA might have already collected
258	 * the file digest without collecting the modsig in a previous
259	 * measurement rule.
260	 */
261	if (modsig)
262		ima_collect_modsig(modsig, buf, size);
263
264	if (iint->flags & IMA_COLLECTED)
265		goto out;
266
267	/*
268	 * Detecting file change is based on i_version. On filesystems
269	 * which do not support i_version, support was originally limited
270	 * to an initial measurement/appraisal/audit, but was modified to
271	 * assume the file changed.
272	 */
273	result = vfs_getattr_nosec(&file->f_path, &stat, STATX_CHANGE_COOKIE,
274				   AT_STATX_SYNC_AS_STAT);
275	if (!result && (stat.result_mask & STATX_CHANGE_COOKIE))
276		i_version = stat.change_cookie;
277	hash.hdr.algo = algo;
278	hash.hdr.length = hash_digest_size[algo];
279
280	/* Initialize hash digest to 0's in case of failure */
281	memset(&hash.digest, 0, sizeof(hash.digest));
282
283	if (iint->flags & IMA_VERITY_REQUIRED) {
284		if (!ima_get_verity_digest(iint, inode, &hash)) {
285			audit_cause = "no-verity-digest";
286			result = -ENODATA;
287		}
288	} else if (buf) {
289		result = ima_calc_buffer_hash(buf, size, &hash.hdr);
290	} else {
291		result = ima_calc_file_hash(file, &hash.hdr);
292	}
293
294	if (result && result != -EBADF && result != -EINVAL)
295		goto out;
296
297	length = sizeof(hash.hdr) + hash.hdr.length;
298	tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
299	if (!tmpbuf) {
300		result = -ENOMEM;
301		goto out;
302	}
303
304	iint->ima_hash = tmpbuf;
305	memcpy(iint->ima_hash, &hash, length);
306	iint->version = i_version;
307	if (real_inode != inode) {
308		iint->real_ino = real_inode->i_ino;
309		iint->real_dev = real_inode->i_sb->s_dev;
310	}
311
312	/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
313	if (!result)
314		iint->flags |= IMA_COLLECTED;
315out:
316	if (result) {
317		if (file->f_flags & O_DIRECT)
318			audit_cause = "failed(directio)";
319
320		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
321				    filename, "collect_data", audit_cause,
322				    result, 0);
323	}
324	return result;
325}
326
327/*
328 * ima_store_measurement - store file measurement
329 *
330 * Create an "ima" template and then store the template by calling
331 * ima_store_template.
332 *
333 * We only get here if the inode has not already been measured,
334 * but the measurement could already exist:
335 *	- multiple copies of the same file on either the same or
336 *	  different filesystems.
337 *	- the inode was previously flushed as well as the iint info,
338 *	  containing the hashing info.
339 *
340 * Must be called with iint->mutex held.
341 */
342void ima_store_measurement(struct ima_iint_cache *iint, struct file *file,
343			   const unsigned char *filename,
344			   struct evm_ima_xattr_data *xattr_value,
345			   int xattr_len, const struct modsig *modsig, int pcr,
346			   struct ima_template_desc *template_desc)
347{
348	static const char op[] = "add_template_measure";
349	static const char audit_cause[] = "ENOMEM";
350	int result = -ENOMEM;
351	struct inode *inode = file_inode(file);
352	struct ima_template_entry *entry;
353	struct ima_event_data event_data = { .iint = iint,
354					     .file = file,
355					     .filename = filename,
356					     .xattr_value = xattr_value,
357					     .xattr_len = xattr_len,
358					     .modsig = modsig };
359	int violation = 0;
360
361	/*
362	 * We still need to store the measurement in the case of MODSIG because
363	 * we only have its contents to put in the list at the time of
364	 * appraisal, but a file measurement from earlier might already exist in
365	 * the measurement list.
366	 */
367	if (iint->measured_pcrs & (0x1 << pcr) && !modsig)
368		return;
369
370	result = ima_alloc_init_template(&event_data, &entry, template_desc);
371	if (result < 0) {
372		integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
373				    op, audit_cause, result, 0);
374		return;
375	}
376
377	result = ima_store_template(entry, violation, inode, filename, pcr);
378	if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
379		iint->flags |= IMA_MEASURED;
380		iint->measured_pcrs |= (0x1 << pcr);
381	}
382	if (result < 0)
383		ima_free_template_entry(entry);
384}
385
386void ima_audit_measurement(struct ima_iint_cache *iint,
387			   const unsigned char *filename)
388{
389	struct audit_buffer *ab;
390	char *hash;
391	const char *algo_name = hash_algo_name[iint->ima_hash->algo];
392	int i;
393
394	if (iint->flags & IMA_AUDITED)
395		return;
396
397	hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
398	if (!hash)
399		return;
400
401	for (i = 0; i < iint->ima_hash->length; i++)
402		hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
403	hash[i * 2] = '\0';
404
405	ab = audit_log_start(audit_context(), GFP_KERNEL,
406			     AUDIT_INTEGRITY_RULE);
407	if (!ab)
408		goto out;
409
410	audit_log_format(ab, "file=");
411	audit_log_untrustedstring(ab, filename);
412	audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);
413
414	audit_log_task_info(ab);
415	audit_log_end(ab);
416
417	iint->flags |= IMA_AUDITED;
418out:
419	kfree(hash);
420	return;
421}
422
423/*
424 * ima_d_path - return a pointer to the full pathname
425 *
426 * Attempt to return a pointer to the full pathname for use in the
427 * IMA measurement list, IMA audit records, and auditing logs.
428 *
429 * On failure, return a pointer to a copy of the filename, not dname.
430 * Returning a pointer to dname, could result in using the pointer
431 * after the memory has been freed.
432 */
433const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
434{
435	char *pathname = NULL;
436
437	*pathbuf = __getname();
438	if (*pathbuf) {
439		pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
440		if (IS_ERR(pathname)) {
441			__putname(*pathbuf);
442			*pathbuf = NULL;
443			pathname = NULL;
444		}
445	}
446
447	if (!pathname) {
448		strscpy(namebuf, path->dentry->d_name.name, NAME_MAX);
449		pathname = namebuf;
450	}
451
452	return pathname;
453}
454