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 
31 LIST_HEAD(ima_measurements);	/* list of all measurements */
32 
33 /* key: inode (before secure-hashing a file) */
34 struct 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  */
44 static DEFINE_MUTEX(ima_extend_list_mutex);
45 
46 /* lookup up the digest value in the hash table, and return the entry */
47 static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
48 						       int pcr)
49 {
50 	struct ima_queue_entry *qe, *ret = NULL;
51 	unsigned int key;
52 	int rc;
53 
54 	key = ima_hash_key(digest_value);
55 	rcu_read_lock();
56 	hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
57 		rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
58 		if ((rc == 0) && (qe->entry->pcr == pcr)) {
59 			ret = qe;
60 			break;
61 		}
62 	}
63 	rcu_read_unlock();
64 	return ret;
65 }
66 
67 /* ima_add_template_entry helper function:
68  * - Add template entry to measurement list and hash table.
69  *
70  * (Called with ima_extend_list_mutex held.)
71  */
72 static int ima_add_digest_entry(struct ima_template_entry *entry)
73 {
74 	struct ima_queue_entry *qe;
75 	unsigned int key;
76 
77 	qe = kmalloc(sizeof(*qe), GFP_KERNEL);
78 	if (qe == NULL) {
79 		pr_err("OUT OF MEMORY ERROR creating queue entry\n");
80 		return -ENOMEM;
81 	}
82 	qe->entry = entry;
83 
84 	INIT_LIST_HEAD(&qe->later);
85 	list_add_tail_rcu(&qe->later, &ima_measurements);
86 
87 	atomic_long_inc(&ima_htable.len);
88 	key = ima_hash_key(entry->digest);
89 	hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
90 	return 0;
91 }
92 
93 static int ima_pcr_extend(const u8 *hash, int pcr)
94 {
95 	int result = 0;
96 
97 	if (!ima_used_chip)
98 		return result;
99 
100 	result = tpm_pcr_extend(TPM_ANY_NUM, pcr, hash);
101 	if (result != 0)
102 		pr_err("Error Communicating to TPM chip, result: %d\n", result);
103 	return result;
104 }
105 
106 /* Add template entry to the measurement list and hash table,
107  * and extend the pcr.
108  */
109 int ima_add_template_entry(struct ima_template_entry *entry, int violation,
110 			   const char *op, struct inode *inode,
111 			   const unsigned char *filename)
112 {
113 	u8 digest[TPM_DIGEST_SIZE];
114 	const char *audit_cause = "hash_added";
115 	char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
116 	int audit_info = 1;
117 	int result = 0, tpmresult = 0;
118 
119 	mutex_lock(&ima_extend_list_mutex);
120 	if (!violation) {
121 		memcpy(digest, entry->digest, sizeof(digest));
122 		if (ima_lookup_digest_entry(digest, entry->pcr)) {
123 			audit_cause = "hash_exists";
124 			result = -EEXIST;
125 			goto out;
126 		}
127 	}
128 
129 	result = ima_add_digest_entry(entry);
130 	if (result < 0) {
131 		audit_cause = "ENOMEM";
132 		audit_info = 0;
133 		goto out;
134 	}
135 
136 	if (violation)		/* invalidate pcr */
137 		memset(digest, 0xff, sizeof(digest));
138 
139 	tpmresult = ima_pcr_extend(digest, entry->pcr);
140 	if (tpmresult != 0) {
141 		snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
142 			 tpmresult);
143 		audit_cause = tpm_audit_cause;
144 		audit_info = 0;
145 	}
146 out:
147 	mutex_unlock(&ima_extend_list_mutex);
148 	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
149 			    op, audit_cause, result, audit_info);
150 	return result;
151 }
152