ima_queue.c revision 9803d413f41db86fdf0097f1af781fe2e68f474c 
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#include <linux/module.h>
22#include <linux/rculist.h>
23#include <linux/slab.h>
24#include "ima.h"
25
26#define AUDIT_CAUSE_LEN_MAX 32
27
28LIST_HEAD(ima_measurements);	/* list of all measurements */
29
30/* key: inode (before secure-hashing a file) */
31struct ima_h_table ima_htable = {
32	.len = ATOMIC_LONG_INIT(0),
33	.violations = ATOMIC_LONG_INIT(0),
34	.queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
35};
36
37/* mutex protects atomicity of extending measurement list
38 * and extending the TPM PCR aggregate. Since tpm_extend can take
39 * long (and the tpm driver uses a mutex), we can't use the spinlock.
40 */
41static DEFINE_MUTEX(ima_extend_list_mutex);
42
43/* lookup up the digest value in the hash table, and return the entry */
44static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value)
45{
46	struct ima_queue_entry *qe, *ret = NULL;
47	unsigned int key;
48	int rc;
49
50	key = ima_hash_key(digest_value);
51	rcu_read_lock();
52	hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
53		rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
54		if (rc == 0) {
55			ret = qe;
56			break;
57		}
58	}
59	rcu_read_unlock();
60	return ret;
61}
62
63/* ima_add_template_entry helper function:
64 * - Add template entry to measurement list and hash table.
65 *
66 * (Called with ima_extend_list_mutex held.)
67 */
68static int ima_add_digest_entry(struct ima_template_entry *entry)
69{
70	struct ima_queue_entry *qe;
71	unsigned int key;
72
73	qe = kmalloc(sizeof(*qe), GFP_KERNEL);
74	if (qe == NULL) {
75		pr_err("IMA: OUT OF MEMORY ERROR creating queue entry.\n");
76		return -ENOMEM;
77	}
78	qe->entry = entry;
79
80	INIT_LIST_HEAD(&qe->later);
81	list_add_tail_rcu(&qe->later, &ima_measurements);
82
83	atomic_long_inc(&ima_htable.len);
84	key = ima_hash_key(entry->digest);
85	hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
86	return 0;
87}
88
89static int ima_pcr_extend(const u8 *hash)
90{
91	int result = 0;
92
93	if (!ima_used_chip)
94		return result;
95
96	result = tpm_pcr_extend(TPM_ANY_NUM, CONFIG_IMA_MEASURE_PCR_IDX, hash);
97	if (result != 0)
98		pr_err("IMA: Error Communicating to TPM chip, result: %d\n",
99		       result);
100	return result;
101}
102
103/* Add template entry to the measurement list and hash table,
104 * and extend the pcr.
105 */
106int ima_add_template_entry(struct ima_template_entry *entry, int violation,
107			   const char *op, struct inode *inode,
108			   const unsigned char *filename)
109{
110	u8 digest[TPM_DIGEST_SIZE];
111	const char *audit_cause = "hash_added";
112	char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
113	int audit_info = 1;
114	int result = 0, tpmresult = 0;
115
116	mutex_lock(&ima_extend_list_mutex);
117	if (!violation) {
118		memcpy(digest, entry->digest, sizeof digest);
119		if (ima_lookup_digest_entry(digest)) {
120			audit_cause = "hash_exists";
121			result = -EEXIST;
122			goto out;
123		}
124	}
125
126	result = ima_add_digest_entry(entry);
127	if (result < 0) {
128		audit_cause = "ENOMEM";
129		audit_info = 0;
130		goto out;
131	}
132
133	if (violation)		/* invalidate pcr */
134		memset(digest, 0xff, sizeof digest);
135
136	tpmresult = ima_pcr_extend(digest);
137	if (tpmresult != 0) {
138		snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
139			 tpmresult);
140		audit_cause = tpm_audit_cause;
141		audit_info = 0;
142	}
143out:
144	mutex_unlock(&ima_extend_list_mutex);
145	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
146			    op, audit_cause, result, audit_info);
147	return result;
148}
149