summaryrefslogtreecommitdiff
path: root/security/integrity/ima/ima_api.c
blob: ce541b0ee1d30c930ab08551ec8cbff13b05bb31 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2008 IBM Corporation
 *
 * Author: Mimi Zohar <zohar@us.ibm.com>
 *
 * File: ima_api.c
 *	Implements must_appraise_or_measure, collect_measurement,
 *	appraise_measurement, store_measurement and store_template.
 */
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/xattr.h>
#include <linux/evm.h>
#include <linux/iversion.h>
#include <linux/fsverity.h>

#include "ima.h"

/*
 * ima_free_template_entry - free an existing template entry
 */
void ima_free_template_entry(struct ima_template_entry *entry)
{
	int i;

	for (i = 0; i < entry->template_desc->num_fields; i++)
		kfree(entry->template_data[i].data);

	kfree(entry->digests);
	kfree(entry);
}

/*
 * ima_alloc_init_template - create and initialize a new template entry
 */
int ima_alloc_init_template(struct ima_event_data *event_data,
			    struct ima_template_entry **entry,
			    struct ima_template_desc *desc)
{
	struct ima_template_desc *template_desc;
	struct tpm_digest *digests;
	int i, result = 0;

	if (desc)
		template_desc = desc;
	else
		template_desc = ima_template_desc_current();

	*entry = kzalloc(struct_size(*entry, template_data,
				     template_desc->num_fields), GFP_NOFS);
	if (!*entry)
		return -ENOMEM;

	digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
			  sizeof(*digests), GFP_NOFS);
	if (!digests) {
		kfree(*entry);
		*entry = NULL;
		return -ENOMEM;
	}

	(*entry)->digests = digests;
	(*entry)->template_desc = template_desc;
	for (i = 0; i < template_desc->num_fields; i++) {
		const struct ima_template_field *field =
			template_desc->fields[i];
		u32 len;

		result = field->field_init(event_data,
					   &((*entry)->template_data[i]));
		if (result != 0)
			goto out;

		len = (*entry)->template_data[i].len;
		(*entry)->template_data_len += sizeof(len);
		(*entry)->template_data_len += len;
	}
	return 0;
out:
	ima_free_template_entry(*entry);
	*entry = NULL;
	return result;
}

/*
 * ima_store_template - store ima template measurements
 *
 * Calculate the hash of a template entry, add the template entry
 * to an ordered list of measurement entries maintained inside the kernel,
 * and also update the aggregate integrity value (maintained inside the
 * configured TPM PCR) over the hashes of the current list of measurement
 * entries.
 *
 * Applications retrieve the current kernel-held measurement list through
 * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
 * TPM PCR (called quote) can be retrieved using a TPM user space library
 * and is used to validate the measurement list.
 *
 * Returns 0 on success, error code otherwise
 */
int ima_store_template(struct ima_template_entry *entry,
		       int violation, struct inode *inode,
		       const unsigned char *filename, int pcr)
{
	static const char op[] = "add_template_measure";
	static const char audit_cause[] = "hashing_error";
	char *template_name = entry->template_desc->name;
	int result;

	if (!violation) {
		result = ima_calc_field_array_hash(&entry->template_data[0],
						   entry);
		if (result < 0) {
			integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
					    template_name, op,
					    audit_cause, result, 0);
			return result;
		}
	}
	entry->pcr = pcr;
	result = ima_add_template_entry(entry, violation, op, inode, filename);
	return result;
}

/*
 * ima_add_violation - add violation to measurement list.
 *
 * Violations are flagged in the measurement list with zero hash values.
 * By extending the PCR with 0xFF's instead of with zeroes, the PCR
 * value is invalidated.
 */
void ima_add_violation(struct file *file, const unsigned char *filename,
		       struct integrity_iint_cache *iint,
		       const char *op, const char *cause)
{
	struct ima_template_entry *entry;
	struct inode *inode = file_inode(file);
	struct ima_event_data event_data = { .iint = iint,
					     .file = file,
					     .filename = filename,
					     .violation = cause };
	int violation = 1;
	int result;

	/* can overflow, only indicator */
	atomic_long_inc(&ima_htable.violations);

	result = ima_alloc_init_template(&event_data, &entry, NULL);
	if (result < 0) {
		result = -ENOMEM;
		goto err_out;
	}
	result = ima_store_template(entry, violation, inode,
				    filename, CONFIG_IMA_MEASURE_PCR_IDX);
	if (result < 0)
		ima_free_template_entry(entry);
err_out:
	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
			    op, cause, result, 0);
}

/**
 * ima_get_action - appraise & measure decision based on policy.
 * @idmap: idmap of the mount the inode was found from
 * @inode: pointer to the inode associated with the object being validated
 * @cred: pointer to credentials structure to validate
 * @secid: secid of the task being validated
 * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
 *        MAY_APPEND)
 * @func: caller identifier
 * @pcr: pointer filled in if matched measure policy sets pcr=
 * @template_desc: pointer filled in if matched measure policy sets template=
 * @func_data: func specific data, may be NULL
 * @allowed_algos: allowlist of hash algorithms for the IMA xattr
 *
 * The policy is defined in terms of keypairs:
 *		subj=, obj=, type=, func=, mask=, fsmagic=
 *	subj,obj, and type: are LSM specific.
 *	func: FILE_CHECK | BPRM_CHECK | CREDS_CHECK | MMAP_CHECK | MODULE_CHECK
 *	| KEXEC_CMDLINE | KEY_CHECK | CRITICAL_DATA | SETXATTR_CHECK
 *	| MMAP_CHECK_REQPROT
 *	mask: contains the permission mask
 *	fsmagic: hex value
 *
 * Returns IMA_MEASURE, IMA_APPRAISE mask.
 *
 */
int ima_get_action(struct mnt_idmap *idmap, struct inode *inode,
		   const struct cred *cred, u32 secid, int mask,
		   enum ima_hooks func, int *pcr,
		   struct ima_template_desc **template_desc,
		   const char *func_data, unsigned int *allowed_algos)
{
	int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;

	flags &= ima_policy_flag;

	return ima_match_policy(idmap, inode, cred, secid, func, mask,
				flags, pcr, template_desc, func_data,
				allowed_algos);
}

static bool ima_get_verity_digest(struct integrity_iint_cache *iint,
				  struct ima_max_digest_data *hash)
{
	enum hash_algo alg;
	int digest_len;

	/*
	 * On failure, 'measure' policy rules will result in a file data
	 * hash containing 0's.
	 */
	digest_len = fsverity_get_digest(iint->inode, hash->digest, NULL, &alg);
	if (digest_len == 0)
		return false;

	/*
	 * Unlike in the case of actually calculating the file hash, in
	 * the fsverity case regardless of the hash algorithm, return
	 * the verity digest to be included in the measurement list. A
	 * mismatch between the verity algorithm and the xattr signature
	 * algorithm, if one exists, will be detected later.
	 */
	hash->hdr.algo = alg;
	hash->hdr.length = digest_len;
	return true;
}

/*
 * ima_collect_measurement - collect file measurement
 *
 * Calculate the file hash, if it doesn't already exist,
 * storing the measurement and i_version in the iint.
 *
 * Must be called with iint->mutex held.
 *
 * Return 0 on success, error code otherwise
 */
int ima_collect_measurement(struct integrity_iint_cache *iint,
			    struct file *file, void *buf, loff_t size,
			    enum hash_algo algo, struct modsig *modsig)
{
	const char *audit_cause = "failed";
	struct inode *inode = file_inode(file);
	const char *filename = file->f_path.dentry->d_name.name;
	struct ima_max_digest_data hash;
	int result = 0;
	int length;
	void *tmpbuf;
	u64 i_version;

	/*
	 * Always collect the modsig, because IMA might have already collected
	 * the file digest without collecting the modsig in a previous
	 * measurement rule.
	 */
	if (modsig)
		ima_collect_modsig(modsig, buf, size);

	if (iint->flags & IMA_COLLECTED)
		goto out;

	/*
	 * Detecting file change is based on i_version. On filesystems
	 * which do not support i_version, support was originally limited
	 * to an initial measurement/appraisal/audit, but was modified to
	 * assume the file changed.
	 */
	i_version = inode_query_iversion(inode);
	hash.hdr.algo = algo;
	hash.hdr.length = hash_digest_size[algo];

	/* Initialize hash digest to 0's in case of failure */
	memset(&hash.digest, 0, sizeof(hash.digest));

	if (iint->flags & IMA_VERITY_REQUIRED) {
		if (!ima_get_verity_digest(iint, &hash)) {
			audit_cause = "no-verity-digest";
			result = -ENODATA;
		}
	} else if (buf) {
		result = ima_calc_buffer_hash(buf, size, &hash.hdr);
	} else {
		result = ima_calc_file_hash(file, &hash.hdr);
	}

	if (result && result != -EBADF && result != -EINVAL)
		goto out;

	length = sizeof(hash.hdr) + hash.hdr.length;
	tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
	if (!tmpbuf) {
		result = -ENOMEM;
		goto out;
	}

	iint->ima_hash = tmpbuf;
	memcpy(iint->ima_hash, &hash, length);
	iint->version = i_version;

	/* Possibly temporary failure due to type of read (eg. O_DIRECT) */
	if (!result)
		iint->flags |= IMA_COLLECTED;
out:
	if (result) {
		if (file->f_flags & O_DIRECT)
			audit_cause = "failed(directio)";

		integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
				    filename, "collect_data", audit_cause,
				    result, 0);
	}
	return result;
}

/*
 * ima_store_measurement - store file measurement
 *
 * Create an "ima" template and then store the template by calling
 * ima_store_template.
 *
 * We only get here if the inode has not already been measured,
 * but the measurement could already exist:
 *	- multiple copies of the same file on either the same or
 *	  different filesystems.
 *	- the inode was previously flushed as well as the iint info,
 *	  containing the hashing info.
 *
 * Must be called with iint->mutex held.
 */
void ima_store_measurement(struct integrity_iint_cache *iint,
			   struct file *file, const unsigned char *filename,
			   struct evm_ima_xattr_data *xattr_value,
			   int xattr_len, const struct modsig *modsig, int pcr,
			   struct ima_template_desc *template_desc)
{
	static const char op[] = "add_template_measure";
	static const char audit_cause[] = "ENOMEM";
	int result = -ENOMEM;
	struct inode *inode = file_inode(file);
	struct ima_template_entry *entry;
	struct ima_event_data event_data = { .iint = iint,
					     .file = file,
					     .filename = filename,
					     .xattr_value = xattr_value,
					     .xattr_len = xattr_len,
					     .modsig = modsig };
	int violation = 0;

	/*
	 * We still need to store the measurement in the case of MODSIG because
	 * we only have its contents to put in the list at the time of
	 * appraisal, but a file measurement from earlier might already exist in
	 * the measurement list.
	 */
	if (iint->measured_pcrs & (0x1 << pcr) && !modsig)
		return;

	result = ima_alloc_init_template(&event_data, &entry, template_desc);
	if (result < 0) {
		integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
				    op, audit_cause, result, 0);
		return;
	}

	result = ima_store_template(entry, violation, inode, filename, pcr);
	if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
		iint->flags |= IMA_MEASURED;
		iint->measured_pcrs |= (0x1 << pcr);
	}
	if (result < 0)
		ima_free_template_entry(entry);
}

void ima_audit_measurement(struct integrity_iint_cache *iint,
			   const unsigned char *filename)
{
	struct audit_buffer *ab;
	char *hash;
	const char *algo_name = hash_algo_name[iint->ima_hash->algo];
	int i;

	if (iint->flags & IMA_AUDITED)
		return;

	hash = kzalloc((iint->ima_hash->length * 2) + 1, GFP_KERNEL);
	if (!hash)
		return;

	for (i = 0; i < iint->ima_hash->length; i++)
		hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
	hash[i * 2] = '\0';

	ab = audit_log_start(audit_context(), GFP_KERNEL,
			     AUDIT_INTEGRITY_RULE);
	if (!ab)
		goto out;

	audit_log_format(ab, "file=");
	audit_log_untrustedstring(ab, filename);
	audit_log_format(ab, " hash=\"%s:%s\"", algo_name, hash);

	audit_log_task_info(ab);
	audit_log_end(ab);

	iint->flags |= IMA_AUDITED;
out:
	kfree(hash);
	return;
}

/*
 * ima_d_path - return a pointer to the full pathname
 *
 * Attempt to return a pointer to the full pathname for use in the
 * IMA measurement list, IMA audit records, and auditing logs.
 *
 * On failure, return a pointer to a copy of the filename, not dname.
 * Returning a pointer to dname, could result in using the pointer
 * after the memory has been freed.
 */
const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
{
	char *pathname = NULL;

	*pathbuf = __getname();
	if (*pathbuf) {
		pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
		if (IS_ERR(pathname)) {
			__putname(*pathbuf);
			*pathbuf = NULL;
			pathname = NULL;
		}
	}

	if (!pathname) {
		strscpy(namebuf, path->dentry->d_name.name, NAME_MAX);
		pathname = namebuf;
	}

	return pathname;
}