1 /*
2 * Copyright (C) 2005,2006,2007,2008 IBM Corporation
3 *
4 * Authors:
5 * Mimi Zohar <zohar@us.ibm.com>
6 * Kylene Hall <kjhall@us.ibm.com>
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation, version 2 of the License.
11 *
12 * File: ima_crypto.c
13 * Calculates md5/sha1 file hash, template hash, boot-aggreate hash
14 */
15
16 #include <linux/kernel.h>
17 #include <linux/file.h>
18 #include <linux/crypto.h>
19 #include <linux/scatterlist.h>
20 #include <linux/err.h>
21 #include <linux/slab.h>
22 #include <crypto/hash.h>
23 #include <crypto/hash_info.h>
24 #include "ima.h"
25
26 static struct crypto_shash *ima_shash_tfm;
27
28 /**
29 * ima_kernel_read - read file content
30 *
31 * This is a function for reading file content instead of kernel_read().
32 * It does not perform locking checks to ensure it cannot be blocked.
33 * It does not perform security checks because it is irrelevant for IMA.
34 *
35 */
36 static int ima_kernel_read(struct file *file, loff_t offset,
37 char *addr, unsigned long count)
38 {
39 mm_segment_t old_fs;
40 char __user *buf = addr;
41 ssize_t ret;
42
43 if (!(file->f_mode & FMODE_READ))
44 return -EBADF;
45 if (!file->f_op->read && !file->f_op->aio_read)
46 return -EINVAL;
47
48 old_fs = get_fs();
49 set_fs(get_ds());
50 if (file->f_op->read)
51 ret = file->f_op->read(file, buf, count, &offset);
52 else
53 ret = do_sync_read(file, buf, count, &offset);
54 set_fs(old_fs);
55 return ret;
56 }
57
58 int ima_init_crypto(void)
59 {
60 long rc;
61
62 ima_shash_tfm = crypto_alloc_shash(hash_algo_name[ima_hash_algo], 0, 0);
63 if (IS_ERR(ima_shash_tfm)) {
64 rc = PTR_ERR(ima_shash_tfm);
65 pr_err("Can not allocate %s (reason: %ld)\n",
66 hash_algo_name[ima_hash_algo], rc);
67 return rc;
68 }
69 return 0;
70 }
71
72 static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
73 {
74 struct crypto_shash *tfm = ima_shash_tfm;
75 int rc;
76
77 if (algo != ima_hash_algo && algo < HASH_ALGO__LAST) {
78 tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
79 if (IS_ERR(tfm)) {
80 rc = PTR_ERR(tfm);
81 pr_err("Can not allocate %s (reason: %d)\n",
82 hash_algo_name[algo], rc);
83 }
84 }
85 return tfm;
86 }
87
88 static void ima_free_tfm(struct crypto_shash *tfm)
89 {
90 if (tfm != ima_shash_tfm)
91 crypto_free_shash(tfm);
92 }
93
94 /*
95 * Calculate the MD5/SHA1 file digest
96 */
97 static int ima_calc_file_hash_tfm(struct file *file,
98 struct ima_digest_data *hash,
99 struct crypto_shash *tfm)
100 {
101 loff_t i_size, offset = 0;
102 char *rbuf;
103 int rc, read = 0;
104 struct {
105 struct shash_desc shash;
106 char ctx[crypto_shash_descsize(tfm)];
107 } desc;
108
109 desc.shash.tfm = tfm;
110 desc.shash.flags = 0;
111
112 hash->length = crypto_shash_digestsize(tfm);
113
114 rc = crypto_shash_init(&desc.shash);
115 if (rc != 0)
116 return rc;
117
118 rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
119 if (!rbuf) {
120 rc = -ENOMEM;
121 goto out;
122 }
123 if (!(file->f_mode & FMODE_READ)) {
124 file->f_mode |= FMODE_READ;
125 read = 1;
126 }
127 i_size = i_size_read(file_inode(file));
128 while (offset < i_size) {
129 int rbuf_len;
130
131 rbuf_len = ima_kernel_read(file, offset, rbuf, PAGE_SIZE);
132 if (rbuf_len < 0) {
133 rc = rbuf_len;
134 break;
135 }
136 if (rbuf_len == 0)
137 break;
138 offset += rbuf_len;
139
140 rc = crypto_shash_update(&desc.shash, rbuf, rbuf_len);
141 if (rc)
142 break;
143 }
144 kfree(rbuf);
145 if (!rc)
146 rc = crypto_shash_final(&desc.shash, hash->digest);
147 if (read)
148 file->f_mode &= ~FMODE_READ;
149 out:
150 return rc;
151 }
152
153 int ima_calc_file_hash(struct file *file, struct ima_digest_data *hash)
154 {
155 struct crypto_shash *tfm;
156 int rc;
157
158 tfm = ima_alloc_tfm(hash->algo);
159 if (IS_ERR(tfm))
160 return PTR_ERR(tfm);
161
162 rc = ima_calc_file_hash_tfm(file, hash, tfm);
163
164 ima_free_tfm(tfm);
165
166 return rc;
167 }
168
169 /*
170 * Calculate the hash of template data
171 */
172 static int ima_calc_field_array_hash_tfm(struct ima_field_data *field_data,
173 struct ima_template_desc *td,
174 int num_fields,
175 struct ima_digest_data *hash,
176 struct crypto_shash *tfm)
177 {
178 struct {
179 struct shash_desc shash;
180 char ctx[crypto_shash_descsize(tfm)];
181 } desc;
182 int rc, i;
183
184 desc.shash.tfm = tfm;
185 desc.shash.flags = 0;
186
187 hash->length = crypto_shash_digestsize(tfm);
188
189 rc = crypto_shash_init(&desc.shash);
190 if (rc != 0)
191 return rc;
192
193 for (i = 0; i < num_fields; i++) {
194 if (strcmp(td->name, IMA_TEMPLATE_IMA_NAME) != 0) {
195 rc = crypto_shash_update(&desc.shash,
196 (const u8 *) &field_data[i].len,
197 sizeof(field_data[i].len));
198 if (rc)
199 break;
200 }
201 rc = crypto_shash_update(&desc.shash, field_data[i].data,
202 field_data[i].len);
203 if (rc)
204 break;
205 }
206
207 if (!rc)
208 rc = crypto_shash_final(&desc.shash, hash->digest);
209
210 return rc;
211 }
212
213 int ima_calc_field_array_hash(struct ima_field_data *field_data,
214 struct ima_template_desc *desc, int num_fields,
215 struct ima_digest_data *hash)
216 {
217 struct crypto_shash *tfm;
218 int rc;
219
220 tfm = ima_alloc_tfm(hash->algo);
221 if (IS_ERR(tfm))
222 return PTR_ERR(tfm);
223
224 rc = ima_calc_field_array_hash_tfm(field_data, desc, num_fields,
225 hash, tfm);
226
227 ima_free_tfm(tfm);
228
229 return rc;
230 }
231
232 static void __init ima_pcrread(int idx, u8 *pcr)
233 {
234 if (!ima_used_chip)
235 return;
236
237 if (tpm_pcr_read(TPM_ANY_NUM, idx, pcr) != 0)
238 pr_err("IMA: Error Communicating to TPM chip\n");
239 }
240
241 /*
242 * Calculate the boot aggregate hash
243 */
244 static int __init ima_calc_boot_aggregate_tfm(char *digest,
245 struct crypto_shash *tfm)
246 {
247 u8 pcr_i[TPM_DIGEST_SIZE];
248 int rc, i;
249 struct {
250 struct shash_desc shash;
251 char ctx[crypto_shash_descsize(tfm)];
252 } desc;
253
254 desc.shash.tfm = tfm;
255 desc.shash.flags = 0;
256
257 rc = crypto_shash_init(&desc.shash);
258 if (rc != 0)
259 return rc;
260
261 /* cumulative sha1 over tpm registers 0-7 */
262 for (i = TPM_PCR0; i < TPM_PCR8; i++) {
263 ima_pcrread(i, pcr_i);
264 /* now accumulate with current aggregate */
265 rc = crypto_shash_update(&desc.shash, pcr_i, TPM_DIGEST_SIZE);
266 }
267 if (!rc)
268 crypto_shash_final(&desc.shash, digest);
269 return rc;
270 }
271
272 int __init ima_calc_boot_aggregate(struct ima_digest_data *hash)
273 {
274 struct crypto_shash *tfm;
275 int rc;
276
277 tfm = ima_alloc_tfm(hash->algo);
278 if (IS_ERR(tfm))
279 return PTR_ERR(tfm);
280
281 hash->length = crypto_shash_digestsize(tfm);
282 rc = ima_calc_boot_aggregate_tfm(hash->digest, tfm);
283
284 ima_free_tfm(tfm);
285
286 return rc;
287 }
288
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.