1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
4  *
5  * Authors:
6  * Serge Hallyn <serue@us.ibm.com>
7  * Reiner Sailer <sailer@watson.ibm.com>
8  * Mimi Zohar <zohar@us.ibm.com>
9  *
10  * File: ima_queue.c
11  *       Implements queues that store template measurements and
12  *       maintains aggregate over the stored measurements
13  *       in the pre-configured TPM PCR (if available).
14  *       The measurement list is append-only. No entry is
15  *       ever removed or changed during the boot-cycle.
16  */
17 
18 #include <linux/rculist.h>
19 #include <linux/slab.h>
20 #include "ima.h"
21 
22 #define AUDIT_CAUSE_LEN_MAX 32
23 
24 /* pre-allocated array of tpm_digest structures to extend a PCR */
25 static struct tpm_digest *digests;
26 
27 LIST_HEAD(ima_measurements);	/* list of all measurements */
28 #ifdef CONFIG_IMA_KEXEC
29 static unsigned long binary_runtime_size;
30 #else
31 static unsigned long binary_runtime_size = ULONG_MAX;
32 #endif
33 
34 /* key: inode (before secure-hashing a file) */
35 struct ima_h_table ima_htable = {
36 	.len = ATOMIC_LONG_INIT(0),
37 	.violations = ATOMIC_LONG_INIT(0),
38 	.queue[0 ... IMA_MEASURE_HTABLE_SIZE - 1] = HLIST_HEAD_INIT
39 };
40 
41 /* mutex protects atomicity of extending measurement list
42  * and extending the TPM PCR aggregate. Since tpm_extend can take
43  * long (and the tpm driver uses a mutex), we can't use the spinlock.
44  */
45 static DEFINE_MUTEX(ima_extend_list_mutex);
46 
47 /* lookup up the digest value in the hash table, and return the entry */
48 static struct ima_queue_entry *ima_lookup_digest_entry(u8 *digest_value,
49 						       int pcr)
50 {
51 	struct ima_queue_entry *qe, *ret = NULL;
52 	unsigned int key;
53 	int rc;
54 
55 	key = ima_hash_key(digest_value);
56 	rcu_read_lock();
57 	hlist_for_each_entry_rcu(qe, &ima_htable.queue[key], hnext) {
58 		rc = memcmp(qe->entry->digest, digest_value, TPM_DIGEST_SIZE);
59 		if ((rc == 0) && (qe->entry->pcr == pcr)) {
60 			ret = qe;
61 			break;
62 		}
63 	}
64 	rcu_read_unlock();
65 	return ret;
66 }
67 
68 /*
69  * Calculate the memory required for serializing a single
70  * binary_runtime_measurement list entry, which contains a
71  * couple of variable length fields (e.g template name and data).
72  */
73 static int get_binary_runtime_size(struct ima_template_entry *entry)
74 {
75 	int size = 0;
76 
77 	size += sizeof(u32);	/* pcr */
78 	size += sizeof(entry->digest);
79 	size += sizeof(int);	/* template name size field */
80 	size += strlen(entry->template_desc->name);
81 	size += sizeof(entry->template_data_len);
82 	size += entry->template_data_len;
83 	return size;
84 }
85 
86 /* ima_add_template_entry helper function:
87  * - Add template entry to the measurement list and hash table, for
88  *   all entries except those carried across kexec.
89  *
90  * (Called with ima_extend_list_mutex held.)
91  */
92 static int ima_add_digest_entry(struct ima_template_entry *entry,
93 				bool update_htable)
94 {
95 	struct ima_queue_entry *qe;
96 	unsigned int key;
97 
98 	qe = kmalloc(sizeof(*qe), GFP_KERNEL);
99 	if (qe == NULL) {
100 		pr_err("OUT OF MEMORY ERROR creating queue entry\n");
101 		return -ENOMEM;
102 	}
103 	qe->entry = entry;
104 
105 	INIT_LIST_HEAD(&qe->later);
106 	list_add_tail_rcu(&qe->later, &ima_measurements);
107 
108 	atomic_long_inc(&ima_htable.len);
109 	if (update_htable) {
110 		key = ima_hash_key(entry->digest);
111 		hlist_add_head_rcu(&qe->hnext, &ima_htable.queue[key]);
112 	}
113 
114 	if (binary_runtime_size != ULONG_MAX) {
115 		int size;
116 
117 		size = get_binary_runtime_size(entry);
118 		binary_runtime_size = (binary_runtime_size < ULONG_MAX - size) ?
119 		     binary_runtime_size + size : ULONG_MAX;
120 	}
121 	return 0;
122 }
123 
124 /*
125  * Return the amount of memory required for serializing the
126  * entire binary_runtime_measurement list, including the ima_kexec_hdr
127  * structure.
128  */
129 unsigned long ima_get_binary_runtime_size(void)
130 {
131 	if (binary_runtime_size >= (ULONG_MAX - sizeof(struct ima_kexec_hdr)))
132 		return ULONG_MAX;
133 	else
134 		return binary_runtime_size + sizeof(struct ima_kexec_hdr);
135 };
136 
137 static int ima_pcr_extend(const u8 *hash, int pcr)
138 {
139 	int result = 0;
140 	int i;
141 
142 	if (!ima_tpm_chip)
143 		return result;
144 
145 	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++)
146 		memcpy(digests[i].digest, hash, TPM_DIGEST_SIZE);
147 
148 	result = tpm_pcr_extend(ima_tpm_chip, pcr, digests);
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 
216 int __init ima_init_digests(void)
217 {
218 	int i;
219 
220 	if (!ima_tpm_chip)
221 		return 0;
222 
223 	digests = kcalloc(ima_tpm_chip->nr_allocated_banks, sizeof(*digests),
224 			  GFP_NOFS);
225 	if (!digests)
226 		return -ENOMEM;
227 
228 	for (i = 0; i < ima_tpm_chip->nr_allocated_banks; i++)
229 		digests[i].alg_id = ima_tpm_chip->allocated_banks[i].alg_id;
230 
231 	return 0;
232 }
233