ima_queue.c revision 20ee451f5a7cd43edda56ba36cbec4d881d3329f 
1/*
2 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
3 *
4 * Authors:
5 * Serge Hallyn <serue@us.ibm.com>
6 * Reiner Sailer <sailer@watson.ibm.com>
7 * Mimi Zohar <zohar@us.ibm.com>
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU General Public License as
11 * published by the Free Software Foundation, version 2 of the
12 * License.
13 *
14 * File: ima_queue.c
15 *       Implements queues that store template measurements and
16 *       maintains aggregate over the stored measurements
17 *       in the pre-configured TPM PCR (if available).
18 *       The measurement list is append-only. No entry is
19 *       ever removed or changed during the boot-cycle.
20 */
21
22#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
23
24#include <linux/module.h>
25#include <linux/rculist.h>
26#include <linux/slab.h>
27#include "ima.h"
28
29#define AUDIT_CAUSE_LEN_MAX 32
30
31LIST_HEAD(ima_measurements);	/* list of all measurements */
32
33/* key: inode (before secure-hashing a file) */
34struct ima_h_table ima_htable = {
35	.len = ATOMIC_LONG_INIT(0),
36	.violations = ATOMIC_LONG_INIT(0),
37	.queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
38};
39
40/* mutex protects atomicity of extending measurement list
41 * and extending the TPM PCR aggregate. Since tpm_extend can take
42 * long (and the tpm driver uses a mutex), we can't use the spinlock.
43 */
44static DEFINE_MUTEX(ima_extend_list_mutex);
45
46/* lookup up the digest value in the hash table, and return the entry */
47static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value)
48{
49	struct ima_queue_entry *qe, *ret = NULL;
50	unsigned int key;
51	int rc;
52
53	key = ima_hash_key(digest_value);
54	rcu_read_lock();
55	hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
56		rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
57		if (rc == 0) {
58			ret = qe;
59			break;
60		}
61	}
62	rcu_read_unlock();
63	return ret;
64}
65
66/* ima_add_template_entry helper function:
67 * - Add template entry to measurement list and hash table.
68 *
69 * (Called with ima_extend_list_mutex held.)
70 */
71static int ima_add_digest_entry(struct ima_template_entry *entry)
72{
73	struct ima_queue_entry *qe;
74	unsigned int key;
75
76	qe = kmalloc(sizeof(*qe), GFP_KERNEL);
77	if (qe == NULL) {
78		pr_err("OUT OF MEMORY ERROR creating queue entry\n");
79		return -ENOMEM;
80	}
81	qe->entry = entry;
82
83	INIT_LIST_HEAD(&qe->later);
84	list_add_tail_rcu(&qe->later, &ima_measurements);
85
86	atomic_long_inc(&ima_htable.len);
87	key = ima_hash_key(entry->digest);
88	hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
89	return 0;
90}
91
92static int ima_pcr_extend(const u8 *hash)
93{
94	int result = 0;
95
96	if (!ima_used_chip)
97		return result;
98
99	result = tpm_pcr_extend(TPM_ANY_NUM, CONFIG_IMA_MEASURE_PCR_IDX, hash);
100	if (result != 0)
101		pr_err("Error Communicating to TPM chip, result: %d\n", result);
102	return result;
103}
104
105/* Add template entry to the measurement list and hash table,
106 * and extend the pcr.
107 */
108int ima_add_template_entry(struct ima_template_entry *entry, int violation,
109			   const char *op, struct inode *inode,
110			   const unsigned char *filename)
111{
112	u8 digest[TPM_DIGEST_SIZE];
113	const char *audit_cause = "hash_added";
114	char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
115	int audit_info = 1;
116	int result = 0, tpmresult = 0;
117
118	mutex_lock(&ima_extend_list_mutex);
119	if (!violation) {
120		memcpy(digest, entry->digest, sizeof digest);
121		if (ima_lookup_digest_entry(digest)) {
122			audit_cause = "hash_exists";
123			result = -EEXIST;
124			goto out;
125		}
126	}
127
128	result = ima_add_digest_entry(entry);
129	if (result < 0) {
130		audit_cause = "ENOMEM";
131		audit_info = 0;
132		goto out;
133	}
134
135	if (violation)		/* invalidate pcr */
136		memset(digest, 0xff, sizeof digest);
137
138	tpmresult = ima_pcr_extend(digest);
139	if (tpmresult != 0) {
140		snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
141			 tpmresult);
142		audit_cause = tpm_audit_cause;
143		audit_info = 0;
144	}
145out:
146	mutex_unlock(&ima_extend_list_mutex);
147	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
148			    op, audit_cause, result, audit_info);
149	return result;
150}
151