1 /*
2 * DRBG based on NIST SP800-90A
3 *
4 * Copyright Stephan Mueller <smueller@chronox.de>, 2014
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, and the entire permission notice in its entirety,
11 * including the disclaimer of warranties.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. The name of the author may not be used to endorse or promote
16 * products derived from this software without specific prior
17 * written permission.
18 *
19 * ALTERNATIVELY, this product may be distributed under the terms of
20 * the GNU General Public License, in which case the provisions of the GPL are
21 * required INSTEAD OF the above restrictions. (This clause is
22 * necessary due to a potential bad interaction between the GPL and
23 * the restrictions contained in a BSD-style copyright.)
24 *
25 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
26 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
28 * WHICH ARE HEREBY DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
29 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
30 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
31 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
32 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
33 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
35 * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
36 * DAMAGE.
37 */
38
39 #ifndef _DRBG_H
40 #define _DRBG_H
41
42
43 #include <linux/random.h>
44 #include <linux/scatterlist.h>
45 #include <crypto/hash.h>
46 #include <crypto/skcipher.h>
47 #include <linux/module.h>
48 #include <linux/crypto.h>
49 #include <linux/slab.h>
50 #include <crypto/internal/rng.h>
51 #include <crypto/rng.h>
52 #include <linux/fips.h>
53 #include <linux/mutex.h>
54 #include <linux/list.h>
55 #include <linux/workqueue.h>
56
57 /*
58 * Concatenation Helper and string operation helper
59 *
60 * SP800-90A requires the concatenation of different data. To avoid copying
61 * buffers around or allocate additional memory, the following data structure
62 * is used to point to the original memory with its size. In addition, it
63 * is used to build a linked list. The linked list defines the concatenation
64 * of individual buffers. The order of memory block referenced in that
65 * linked list determines the order of concatenation.
66 */
67 struct drbg_string {
68 const unsigned char *buf;
69 size_t len;
70 struct list_head list;
71 };
72
73 static inline void drbg_string_fill(struct drbg_string *string,
74 const unsigned char *buf, size_t len)
75 {
76 string->buf = buf;
77 string->len = len;
78 INIT_LIST_HEAD(&string->list);
79 }
80
81 struct drbg_state;
82 typedef uint32_t drbg_flag_t;
83
84 struct drbg_core {
85 drbg_flag_t flags; /* flags for the cipher */
86 __u8 statelen; /* maximum state length */
87 __u8 blocklen_bytes; /* block size of output in bytes */
88 char cra_name[CRYPTO_MAX_ALG_NAME]; /* mapping to kernel crypto API */
89 /* kernel crypto API backend cipher name */
90 char backend_cra_name[CRYPTO_MAX_ALG_NAME];
91 };
92
93 struct drbg_state_ops {
94 int (*update)(struct drbg_state *drbg, struct list_head *seed,
95 int reseed);
96 int (*generate)(struct drbg_state *drbg,
97 unsigned char *buf, unsigned int buflen,
98 struct list_head *addtl);
99 int (*crypto_init)(struct drbg_state *drbg);
100 int (*crypto_fini)(struct drbg_state *drbg);
101
102 };
103
104 struct drbg_test_data {
105 struct drbg_string *testentropy; /* TEST PARAMETER: test entropy */
106 };
107
108 struct drbg_state {
109 struct mutex drbg_mutex; /* lock around DRBG */
110 unsigned char *V; /* internal state 10.1.1.1 1a) */
111 unsigned char *Vbuf;
112 /* hash: static value 10.1.1.1 1b) hmac / ctr: key */
113 unsigned char *C;
114 unsigned char *Cbuf;
115 /* Number of RNG requests since last reseed -- 10.1.1.1 1c) */
116 size_t reseed_ctr;
117 size_t reseed_threshold;
118 /* some memory the DRBG can use for its operation */
119 unsigned char *scratchpad;
120 unsigned char *scratchpadbuf;
121 void *priv_data; /* Cipher handle */
122
123 struct crypto_skcipher *ctr_handle; /* CTR mode cipher handle */
124 struct skcipher_request *ctr_req; /* CTR mode request handle */
125 __u8 *outscratchpadbuf; /* CTR mode output scratchpad */
126 __u8 *outscratchpad; /* CTR mode aligned outbuf */
127 struct crypto_wait ctr_wait; /* CTR mode async wait obj */
128 struct scatterlist sg_in, sg_out; /* CTR mode SGLs */
129
130 bool seeded; /* DRBG fully seeded? */
131 bool pr; /* Prediction resistance enabled? */
132 bool fips_primed; /* Continuous test primed? */
133 unsigned char *prev; /* FIPS 140-2 continuous test value */
134 struct work_struct seed_work; /* asynchronous seeding support */
135 struct crypto_rng *jent;
136 const struct drbg_state_ops *d_ops;
137 const struct drbg_core *core;
138 struct drbg_string test_data;
139 struct random_ready_callback random_ready;
140 };
141
142 static inline __u8 drbg_statelen(struct drbg_state *drbg)
143 {
144 if (drbg && drbg->core)
145 return drbg->core->statelen;
146 return 0;
147 }
148
149 static inline __u8 drbg_blocklen(struct drbg_state *drbg)
150 {
151 if (drbg && drbg->core)
152 return drbg->core->blocklen_bytes;
153 return 0;
154 }
155
156 static inline __u8 drbg_keylen(struct drbg_state *drbg)
157 {
158 if (drbg && drbg->core)
159 return (drbg->core->statelen - drbg->core->blocklen_bytes);
160 return 0;
161 }
162
163 static inline size_t drbg_max_request_bytes(struct drbg_state *drbg)
164 {
165 /* SP800-90A requires the limit 2**19 bits, but we return bytes */
166 return (1 << 16);
167 }
168
169 static inline size_t drbg_max_addtl(struct drbg_state *drbg)
170 {
171 /* SP800-90A requires 2**35 bytes additional info str / pers str */
172 #if (__BITS_PER_LONG == 32)
173 /*
174 * SP800-90A allows smaller maximum numbers to be returned -- we
175 * return SIZE_MAX - 1 to allow the verification of the enforcement
176 * of this value in drbg_healthcheck_sanity.
177 */
178 return (SIZE_MAX - 1);
179 #else
180 return (1UL<<35);
181 #endif
182 }
183
184 static inline size_t drbg_max_requests(struct drbg_state *drbg)
185 {
186 /* SP800-90A requires 2**48 maximum requests before reseeding */
187 #if (__BITS_PER_LONG == 32)
188 return SIZE_MAX;
189 #else
190 return (1UL<<48);
191 #endif
192 }
193
194 /*
195 * This is a wrapper to the kernel crypto API function of
196 * crypto_rng_generate() to allow the caller to provide additional data.
197 *
198 * @drng DRBG handle -- see crypto_rng_get_bytes
199 * @outbuf output buffer -- see crypto_rng_get_bytes
200 * @outlen length of output buffer -- see crypto_rng_get_bytes
201 * @addtl_input additional information string input buffer
202 * @addtllen length of additional information string buffer
203 *
204 * return
205 * see crypto_rng_get_bytes
206 */
207 static inline int crypto_drbg_get_bytes_addtl(struct crypto_rng *drng,
208 unsigned char *outbuf, unsigned int outlen,
209 struct drbg_string *addtl)
210 {
211 return crypto_rng_generate(drng, addtl->buf, addtl->len,
212 outbuf, outlen);
213 }
214
215 /*
216 * TEST code
217 *
218 * This is a wrapper to the kernel crypto API function of
219 * crypto_rng_generate() to allow the caller to provide additional data and
220 * allow furnishing of test_data
221 *
222 * @drng DRBG handle -- see crypto_rng_get_bytes
223 * @outbuf output buffer -- see crypto_rng_get_bytes
224 * @outlen length of output buffer -- see crypto_rng_get_bytes
225 * @addtl_input additional information string input buffer
226 * @addtllen length of additional information string buffer
227 * @test_data filled test data
228 *
229 * return
230 * see crypto_rng_get_bytes
231 */
232 static inline int crypto_drbg_get_bytes_addtl_test(struct crypto_rng *drng,
233 unsigned char *outbuf, unsigned int outlen,
234 struct drbg_string *addtl,
235 struct drbg_test_data *test_data)
236 {
237 crypto_rng_set_entropy(drng, test_data->testentropy->buf,
238 test_data->testentropy->len);
239 return crypto_rng_generate(drng, addtl->buf, addtl->len,
240 outbuf, outlen);
241 }
242
243 /*
244 * TEST code
245 *
246 * This is a wrapper to the kernel crypto API function of
247 * crypto_rng_reset() to allow the caller to provide test_data
248 *
249 * @drng DRBG handle -- see crypto_rng_reset
250 * @pers personalization string input buffer
251 * @perslen length of additional information string buffer
252 * @test_data filled test data
253 *
254 * return
255 * see crypto_rng_reset
256 */
257 static inline int crypto_drbg_reset_test(struct crypto_rng *drng,
258 struct drbg_string *pers,
259 struct drbg_test_data *test_data)
260 {
261 crypto_rng_set_entropy(drng, test_data->testentropy->buf,
262 test_data->testentropy->len);
263 return crypto_rng_reset(drng, pers->buf, pers->len);
264 }
265
266 /* DRBG type flags */
267 #define DRBG_CTR ((drbg_flag_t)1<<0)
268 #define DRBG_HMAC ((drbg_flag_t)1<<1)
269 #define DRBG_HASH ((drbg_flag_t)1<<2)
270 #define DRBG_TYPE_MASK (DRBG_CTR | DRBG_HMAC | DRBG_HASH)
271 /* DRBG strength flags */
272 #define DRBG_STRENGTH128 ((drbg_flag_t)1<<3)
273 #define DRBG_STRENGTH192 ((drbg_flag_t)1<<4)
274 #define DRBG_STRENGTH256 ((drbg_flag_t)1<<5)
275 #define DRBG_STRENGTH_MASK (DRBG_STRENGTH128 | DRBG_STRENGTH192 | \
276 DRBG_STRENGTH256)
277
278 enum drbg_prefixes {
279 DRBG_PREFIX0 = 0x00,
280 DRBG_PREFIX1,
281 DRBG_PREFIX2,
282 DRBG_PREFIX3
283 };
284
285 #endif /* _DRBG_H */