ima_queue.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
  4 *
  5 * Authors:
  6 * Serge Hallyn <serue@us.ibm.com>
  7 * Reiner Sailer <sailer@watson.ibm.com>
  8 * Mimi Zohar <zohar@us.ibm.com>
  9 *
 10 * File: ima_queue.c
 11 *       Implements queues that store template measurements and
 12 *       maintains aggregate over the stored measurements
 13 *       in the pre-configured TPM PCR (if available).
 14 *       The measurement list is append-only. No entry is
 15 *       ever removed or changed during the boot-cycle.
 16 */
 17
 18#include <linux/rculist.h>
 19#include <linux/reboot.h>
 20#include <linux/slab.h>
 21#include "ima.h"
 22
 23#define AUDIT_CAUSE_LEN_MAX 32
 24
 25/* pre-allocated array of tpm_digest structures to extend a PCR */
 26static struct tpm_digest *digests;
 27
 28LIST_HEAD(ima_measurements);	/* list of all measurements */
 29#ifdef CONFIG_IMA_KEXEC
 30static unsigned long binary_runtime_size;
 31#else
 32static unsigned long binary_runtime_size = ULONG_MAX;
 33#endif
 34
 35/* key: inode (before secure-hashing a file) */
 36struct ima_h_table ima_htable = {
 37	.len = ATOMIC_LONG_INIT(0),
 38	.violations = ATOMIC_LONG_INIT(0),
 39	.queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
 40};
 41
 42/* mutex protects atomicity of extending measurement list
 43 * and extending the TPM PCR aggregate. Since tpm_extend can take
 44 * long (and the tpm driver uses a mutex), we can't use the spinlock.
 45 */
 46static DEFINE_MUTEX(ima_extend_list_mutex);
 47
 48/*
 49 * Used internally by the kernel to suspend measurements.
 50 * Protected by ima_extend_list_mutex.
 51 */
 52static bool ima_measurements_suspended;
 53
 54/* lookup up the digest value in the hash table, and return the entry */
 55static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
 56						       int pcr)
 57{
 58	struct ima_queue_entry *qe, *ret = NULL;
 59	unsigned int key;
 60	int rc;
 61
 62	key = ima_hash_key(digest_value);
 63	rcu_read_lock();
 64	hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
 65		rc = memcmp(qe->entry->digests[ima_hash_algo_idx].digest,
 66			    digest_value, hash_digest_size[ima_hash_algo]);
 67		if ((rc == 0) && (qe->entry->pcr == pcr)) {
 68			ret = qe;
 69			break;
 70		}
 71	}
 72	rcu_read_unlock();
 73	return ret;
 74}
 75
 76/*
 77 * Calculate the memory required for serializing a single
 78 * binary_runtime_measurement list entry, which contains a
 79 * couple of variable length fields (e.g template name and data).
 80 */
 81static int get_binary_runtime_size(struct ima_template_entry *entry)
 82{
 83	int size = 0;
 84
 85	size += sizeof(u32);	/* pcr */
 86	size += TPM_DIGEST_SIZE;
 87	size += sizeof(int);	/* template name size field */
 88	size += strlen(entry->template_desc->name);
 89	size += sizeof(entry->template_data_len);
 90	size += entry->template_data_len;
 91	return size;
 92}
 93
 94/* ima_add_template_entry helper function:
 95 * - Add template entry to the measurement list and hash table, for
 96 *   all entries except those carried across kexec.
 97 *
 98 * (Called with ima_extend_list_mutex held.)
 99 */
100static int ima_add_digest_entry(struct ima_template_entry *entry,
101				bool update_htable)
102{
103	struct ima_queue_entry *qe;
104	unsigned int key;
105
106	qe = kmalloc(sizeof(*qe), GFP_KERNEL);
107	if (qe == NULL) {
108		pr_err("OUT OF MEMORY ERROR creating queue entry\n");
109		return -ENOMEM;
110	}
111	qe->entry = entry;
112
113	INIT_LIST_HEAD(&qe->later);
114	list_add_tail_rcu(&qe->later, &ima_measurements);
115
116	atomic_long_inc(&ima_htable.len);
117	if (update_htable) {
118		key = ima_hash_key(entry->digests[ima_hash_algo_idx].digest);
119		hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
120	}
121
122	if (binary_runtime_size != ULONG_MAX) {
123		int size;
124
125		size = get_binary_runtime_size(entry);
126		binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ?
127		     binary_runtime_size + size : ULONG_MAX;
128	}
129	return 0;
130}
131
132/*
133 * Return the amount of memory required for serializing the
134 * entire binary_runtime_measurement list, including the ima_kexec_hdr
135 * structure.
136 */
137unsigned long ima_get_binary_runtime_size(void)
138{
139	if (binary_runtime_size >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
140		return ULONG_MAX;
141	else
142		return binary_runtime_size + sizeof(struct ima_kexec_hdr);
143}
144
145static int ima_pcr_extend(struct tpm_digest *digests_arg, int pcr)
146{
147	int result = 0;
148
149	if (!ima_tpm_chip)
150		return result;
151
152	result = tpm_pcr_extend(ima_tpm_chip, pcr, digests_arg);
153	if (result != 0)
154		pr_err("Error Communicating to TPM chip, result: %d\n", result);
155	return result;
156}
157
158/*
159 * Add template entry to the measurement list and hash table, and
160 * extend the pcr.
161 *
162 * On systems which support carrying the IMA measurement list across
163 * kexec, maintain the total memory size required for serializing the
164 * binary_runtime_measurements.
165 */
166int ima_add_template_entry(struct ima_template_entry *entry, int violation,
167			   const char *op, struct inode *inode,
168			   const unsigned char *filename)
169{
170	u8 *digest = entry->digests[ima_hash_algo_idx].digest;
171	struct tpm_digest *digests_arg = entry->digests;
172	const char *audit_cause = "hash_added";
173	char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
174	int audit_info = 1;
175	int result = 0, tpmresult = 0;
176
177	mutex_lock(&ima_extend_list_mutex);
178
179	/*
180	 * Avoid appending to the measurement log when the TPM subsystem has
181	 * been shut down while preparing for system reboot.
182	 */
183	if (ima_measurements_suspended) {
184		audit_cause = "measurements_suspended";
185		audit_info = 0;
186		result = -ENODEV;
187		goto out;
188	}
189
190	if (!violation && !IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE)) {
191		if (ima_lookup_digest_entry(digest, entry->pcr)) {
192			audit_cause = "hash_exists";
193			result = -EEXIST;
194			goto out;
195		}
196	}
197
198	result = ima_add_digest_entry(entry,
199				      !IS_ENABLED(CONFIG_IMA_DISABLE_HTABLE));
200	if (result < 0) {
201		audit_cause = "ENOMEM";
202		audit_info = 0;
203		goto out;
204	}
205
206	if (violation)		/* invalidate pcr */
207		digests_arg = digests;
208
209	tpmresult = ima_pcr_extend(digests_arg, entry->pcr);
210	if (tpmresult != 0) {
211		snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
212			 tpmresult);
213		audit_cause = tpm_audit_cause;
214		audit_info = 0;
215	}
216out:
217	mutex_unlock(&ima_extend_list_mutex);
218	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
219			    op, audit_cause, result, audit_info);
220	return result;
221}
222
223int ima_restore_measurement_entry(struct ima_template_entry *entry)
224{
225	int result = 0;
226
227	mutex_lock(&ima_extend_list_mutex);
228	result = ima_add_digest_entry(entry, 0);
229	mutex_unlock(&ima_extend_list_mutex);
230	return result;
231}
232
233static void ima_measurements_suspend(void)
234{
235	mutex_lock(&ima_extend_list_mutex);
236	ima_measurements_suspended = true;
237	mutex_unlock(&ima_extend_list_mutex);
238}
239
240static int ima_reboot_notifier(struct notifier_block *nb,
241			       unsigned long action,
242			       void *data)
243{
244#ifdef CONFIG_IMA_KEXEC
245	if (action == SYS_RESTART && data && !strcmp(data, "kexec reboot"))
246		ima_measure_kexec_event("kexec_execute");
247#endif
248
249	ima_measurements_suspend();
250
251	return NOTIFY_DONE;
252}
253
254static struct notifier_block ima_reboot_nb = {
255	.notifier_call = ima_reboot_notifier,
256};
257
258void __init ima_init_reboot_notifier(void)
259{
260	register_reboot_notifier(&ima_reboot_nb);
261}
262
263int __init ima_init_digests(void)
264{
265	u16 digest_size;
266	u16 crypto_id;
267	int i;
268
269	if (!ima_tpm_chip)
270		return 0;
271
272	digests = kcalloc(ima_tpm_chip->nr_allocated_banks, sizeof(*digests),
273			  GFP_NOFS);
274	if (!digests)
275		return -ENOMEM;
276
277	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++) {
278		digests[i].alg_id = ima_tpm_chip->allocated_banks[i].alg_id;
279		digest_size = ima_tpm_chip->allocated_banks[i].digest_size;
280		crypto_id = ima_tpm_chip->allocated_banks[i].crypto_id;
281
282		/* for unmapped TPM algorithms digest is still a padded SHA1 */
283		if (crypto_id == HASH_ALGO__LAST)
284			digest_size = SHA1_DIGEST_SIZE;
285
286		memset(digests[i].digest, 0xff, digest_size);
287	}
288
289	return 0;
290}