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