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 #ifdef CONFIG_IMA_KEXEC
33 static unsigned long binary_runtime_size;
34 #else
35 static unsigned long binary_runtime_size = ULONG_MAX;
36 #endif
37 
38 /* key: inode (before secure-hashing a file) */
39 struct ima_h_table ima_htable = {
40 	.len = ATOMIC_LONG_INIT(0),
41 	.violations = ATOMIC_LONG_INIT(0),
42 	.queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
43 };
44 
45 /* mutex protects atomicity of extending measurement list
46  * and extending the TPM PCR aggregate. Since tpm_extend can take
47  * long (and the tpm driver uses a mutex), we can't use the spinlock.
48  */
49 static DEFINE_MUTEX(ima_extend_list_mutex);
50 
51 /* lookup up the digest value in the hash table, and return the entry */
52 static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
53 						       int pcr)
54 {
55 	struct ima_queue_entry *qe, *ret = NULL;
56 	unsigned int key;
57 	int rc;
58 
59 	key = ima_hash_key(digest_value);
60 	rcu_read_lock();
61 	hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
62 		rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
63 		if ((rc == 0) && (qe->entry->pcr == pcr)) {
64 			ret = qe;
65 			break;
66 		}
67 	}
68 	rcu_read_unlock();
69 	return ret;
70 }
71 
72 /*
73  * Calculate the memory required for serializing a single
74  * binary_runtime_measurement list entry, which contains a
75  * couple of variable length fields (e.g template name and data).
76  */
77 static int get_binary_runtime_size(struct ima_template_entry *entry)
78 {
79 	int size = 0;
80 
81 	size += sizeof(u32);	/* pcr */
82 	size += sizeof(entry->digest);
83 	size += sizeof(int);	/* template name size field */
84 	size += strlen(entry->template_desc->name);
85 	size += sizeof(entry->template_data_len);
86 	size += entry->template_data_len;
87 	return size;
88 }
89 
90 /* ima_add_template_entry helper function:
91  * - Add template entry to the measurement list and hash table, for
92  *   all entries except those carried across kexec.
93  *
94  * (Called with ima_extend_list_mutex held.)
95  */
96 static int ima_add_digest_entry(struct ima_template_entry *entry,
97 				bool update_htable)
98 {
99 	struct ima_queue_entry *qe;
100 	unsigned int key;
101 
102 	qe = kmalloc(sizeof(*qe), GFP_KERNEL);
103 	if (qe == NULL) {
104 		pr_err("OUT OF MEMORY ERROR creating queue entry\n");
105 		return -ENOMEM;
106 	}
107 	qe->entry = entry;
108 
109 	INIT_LIST_HEAD(&qe->later);
110 	list_add_tail_rcu(&qe->later, &ima_measurements);
111 
112 	atomic_long_inc(&ima_htable.len);
113 	if (update_htable) {
114 		key = ima_hash_key(entry->digest);
115 		hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
116 	}
117 
118 	if (binary_runtime_size != ULONG_MAX) {
119 		int size;
120 
121 		size = get_binary_runtime_size(entry);
122 		binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ?
123 		     binary_runtime_size + size : ULONG_MAX;
124 	}
125 	return 0;
126 }
127 
128 /*
129  * Return the amount of memory required for serializing the
130  * entire binary_runtime_measurement list, including the ima_kexec_hdr
131  * structure.
132  */
133 unsigned long ima_get_binary_runtime_size(void)
134 {
135 	if (binary_runtime_size >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
136 		return ULONG_MAX;
137 	else
138 		return binary_runtime_size + sizeof(struct ima_kexec_hdr);
139 };
140 
141 static int ima_pcr_extend(const u8 *hash, int pcr)
142 {
143 	int result = 0;
144 
145 	if (!ima_used_chip)
146 		return result;
147 
148 	result = tpm_pcr_extend(TPM_ANY_NUM, pcr, hash);
149 	if (result != 0)
150 		pr_err("Error Communicating to TPM chip, result: %d\n", result);
151 	return result;
152 }
153 
154 /*
155  * Add template entry to the measurement list and hash table, and
156  * extend the pcr.
157  *
158  * On systems which support carrying the IMA measurement list across
159  * kexec, maintain the total memory size required for serializing the
160  * binary_runtime_measurements.
161  */
162 int ima_add_template_entry(struct ima_template_entry *entry, int violation,
163 			   const char *op, struct inode *inode,
164 			   const unsigned char *filename)
165 {
166 	u8 digest[TPM_DIGEST_SIZE];
167 	const char *audit_cause = "hash_added";
168 	char tpm_audit_cause[AUDIT_CAUSE_LEN_MAX];
169 	int audit_info = 1;
170 	int result = 0, tpmresult = 0;
171 
172 	mutex_lock(&ima_extend_list_mutex);
173 	if (!violation) {
174 		memcpy(digest, entry->digest, sizeof(digest));
175 		if (ima_lookup_digest_entry(digest, entry->pcr)) {
176 			audit_cause = "hash_exists";
177 			result = -EEXIST;
178 			goto out;
179 		}
180 	}
181 
182 	result = ima_add_digest_entry(entry, 1);
183 	if (result < 0) {
184 		audit_cause = "ENOMEM";
185 		audit_info = 0;
186 		goto out;
187 	}
188 
189 	if (violation)		/* invalidate pcr */
190 		memset(digest, 0xff, sizeof(digest));
191 
192 	tpmresult = ima_pcr_extend(digest, entry->pcr);
193 	if (tpmresult != 0) {
194 		snprintf(tpm_audit_cause, AUDIT_CAUSE_LEN_MAX, "TPM_error(%d)",
195 			 tpmresult);
196 		audit_cause = tpm_audit_cause;
197 		audit_info = 0;
198 	}
199 out:
200 	mutex_unlock(&ima_extend_list_mutex);
201 	integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
202 			    op, audit_cause, result, audit_info);
203 	return result;
204 }
205 
206 int ima_restore_measurement_entry(struct ima_template_entry *entry)
207 {
208 	int result = 0;
209 
210 	mutex_lock(&ima_extend_list_mutex);
211 	result = ima_add_digest_entry(entry, 0);
212 	mutex_unlock(&ima_extend_list_mutex);
213 	return result;
214 }
215