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1 | /* |
2 | * Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved. | |
3 | * | |
4 | * Licensed under the OpenSSL license (the "License"). You may not use | |
5 | * this file except in compliance with the License. You can obtain a copy | |
6 | * in the file LICENSE in the source distribution or at | |
7 | * https://www.openssl.org/source/license.html | |
8 | */ | |
9 | ||
10 | #include <assert.h> | |
11 | #include <stdlib.h> | |
12 | #include <string.h> | |
13 | #include <openssl/crypto.h> | |
14 | #include <openssl/err.h> | |
15 | #include <openssl/rand.h> | |
16 | #include "internal/thread_once.h" | |
17 | #include "rand_lcl.h" | |
18 | ||
19 | /* 440 bits from SP800-90Ar1 10.1 table 2 */ | |
20 | #define HASH_PRNG_SMALL_SEEDLEN (440/8) | |
21 | /* Determine what seedlen to use based on the block length */ | |
22 | #define MAX_BLOCKLEN_USING_SMALL_SEEDLEN (256/8) | |
23 | #define INBYTE_IGNORE ((unsigned char)0xFF) | |
24 | ||
25 | ||
26 | /* | |
27 | * SP800-90Ar1 10.3.1 Derivation function using a Hash Function (Hash_df). | |
28 | * The input string used is composed of: | |
29 | * inbyte - An optional leading byte (ignore if equal to INBYTE_IGNORE) | |
30 | * in - input string 1 (A Non NULL value). | |
31 | * in2 - optional input string (Can be NULL). | |
32 | * in3 - optional input string (Can be NULL). | |
33 | * These are concatenated as part of the DigestUpdate process. | |
34 | */ | |
35 | static int hash_df(RAND_DRBG *drbg, unsigned char *out, | |
36 | const unsigned char inbyte, | |
37 | const unsigned char *in, size_t inlen, | |
38 | const unsigned char *in2, size_t in2len, | |
39 | const unsigned char *in3, size_t in3len) | |
40 | { | |
41 | RAND_DRBG_HASH *hash = &drbg->data.hash; | |
42 | EVP_MD_CTX *ctx = hash->ctx; | |
43 | unsigned char *vtmp = hash->vtmp; | |
44 | /* tmp = counter || num_bits_returned || [inbyte] */ | |
45 | unsigned char tmp[1 + 4 + 1]; | |
46 | int tmp_sz = 0; | |
47 | size_t outlen = drbg->seedlen; | |
48 | size_t num_bits_returned = outlen * 8; | |
49 | /* | |
50 | * No need to check outlen size here, as the standard only ever needs | |
51 | * seedlen bytes which is always less than the maximum permitted. | |
52 | */ | |
53 | ||
54 | /* (Step 3) counter = 1 (tmp[0] is the 8 bit counter) */ | |
55 | tmp[tmp_sz++] = 1; | |
56 | /* tmp[1..4] is the fixed 32 bit no_of_bits_to_return */ | |
57 | tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 24) & 0xff); | |
58 | tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 16) & 0xff); | |
59 | tmp[tmp_sz++] = (unsigned char)((num_bits_returned >> 8) & 0xff); | |
60 | tmp[tmp_sz++] = (unsigned char)(num_bits_returned & 0xff); | |
61 | /* Tack the additional input byte onto the end of tmp if it exists */ | |
62 | if (inbyte != INBYTE_IGNORE) | |
63 | tmp[tmp_sz++] = inbyte; | |
64 | ||
65 | /* (Step 4) */ | |
66 | for (;;) { | |
67 | /* | |
68 | * (Step 4.1) out = out || Hash(tmp || in || [in2] || [in3]) | |
69 | * (where tmp = counter || num_bits_returned || [inbyte]) | |
70 | */ | |
71 | if (!(EVP_DigestInit_ex(ctx, hash->md, NULL) | |
72 | && EVP_DigestUpdate(ctx, tmp, tmp_sz) | |
73 | && EVP_DigestUpdate(ctx, in, inlen) | |
74 | && (in2 == NULL || EVP_DigestUpdate(ctx, in2, in2len)) | |
75 | && (in3 == NULL || EVP_DigestUpdate(ctx, in3, in3len)))) | |
76 | return 0; | |
77 | ||
78 | if (outlen < hash->blocklen) { | |
79 | if (!EVP_DigestFinal(ctx, vtmp, NULL)) | |
80 | return 0; | |
81 | memcpy(out, vtmp, outlen); | |
82 | OPENSSL_cleanse(vtmp, hash->blocklen); | |
83 | break; | |
84 | } else if(!EVP_DigestFinal(ctx, out, NULL)) { | |
85 | return 0; | |
86 | } | |
87 | ||
88 | outlen -= hash->blocklen; | |
89 | if (outlen == 0) | |
90 | break; | |
91 | /* (Step 4.2) counter++ */ | |
92 | tmp[0]++; | |
93 | out += hash->blocklen; | |
94 | } | |
95 | return 1; | |
96 | } | |
97 | ||
98 | /* Helper function that just passes 2 input parameters to hash_df() */ | |
99 | static int hash_df1(RAND_DRBG *drbg, unsigned char *out, | |
100 | const unsigned char in_byte, | |
101 | const unsigned char *in1, size_t in1len) | |
102 | { | |
103 | return hash_df(drbg, out, in_byte, in1, in1len, NULL, 0, NULL, 0); | |
104 | } | |
105 | ||
106 | /* | |
107 | * Add 2 byte buffers together. The first elements in each buffer are the top | |
108 | * most bytes. The result is stored in the dst buffer. | |
109 | * The final carry is ignored i.e: dst = (dst + in) mod (2^seedlen_bits). | |
110 | * where dst size is drbg->seedlen, and inlen <= drbg->seedlen. | |
111 | */ | |
112 | static int add_bytes(RAND_DRBG *drbg, unsigned char *dst, | |
113 | unsigned char *in, size_t inlen) | |
114 | { | |
115 | size_t i; | |
116 | int result; | |
117 | const unsigned char *add; | |
118 | unsigned char carry = 0, *d; | |
119 | ||
120 | assert(drbg->seedlen >= 1 && inlen >= 1 && inlen <= drbg->seedlen); | |
121 | ||
122 | d = &dst[drbg->seedlen - 1]; | |
123 | add = &in[inlen - 1]; | |
124 | ||
125 | for (i = inlen; i > 0; i--, d--, add--) { | |
126 | result = *d + *add + carry; | |
127 | carry = (unsigned char)(result >> 8); | |
128 | *d = (unsigned char)(result & 0xff); | |
129 | } | |
130 | ||
131 | if (carry != 0) { | |
132 | /* Add the carry to the top of the dst if inlen is not the same size */ | |
133 | for (i = drbg->seedlen - inlen; i > 0; --i, d--) { | |
134 | *d += 1; /* Carry can only be 1 */ | |
135 | if (*d != 0) /* exit if carry doesnt propagate to the next byte */ | |
136 | break; | |
137 | } | |
138 | } | |
139 | return 1; | |
140 | } | |
141 | ||
142 | /* V = (V + Hash(inbyte || V || [additional_input]) mod (2^seedlen) */ | |
143 | static int add_hash_to_v(RAND_DRBG *drbg, unsigned char inbyte, | |
144 | const unsigned char *adin, size_t adinlen) | |
145 | { | |
146 | RAND_DRBG_HASH *hash = &drbg->data.hash; | |
147 | EVP_MD_CTX *ctx = hash->ctx; | |
148 | ||
149 | return EVP_DigestInit_ex(ctx, hash->md, NULL) | |
150 | && EVP_DigestUpdate(ctx, &inbyte, 1) | |
151 | && EVP_DigestUpdate(ctx, hash->V, drbg->seedlen) | |
152 | && (adin == NULL || EVP_DigestUpdate(ctx, adin, adinlen)) | |
153 | && EVP_DigestFinal(ctx, hash->vtmp, NULL) | |
154 | && add_bytes(drbg, hash->V, hash->vtmp, hash->blocklen); | |
155 | } | |
156 | ||
157 | /* | |
158 | * The Hashgen() as listed in SP800-90Ar1 10.1.1.4 Hash_DRBG_Generate_Process. | |
159 | * | |
160 | * drbg contains the current value of V. | |
161 | * outlen is the requested number of bytes. | |
162 | * out is a buffer to return the generated bits. | |
163 | * | |
164 | * The algorithm to generate the bits is: | |
165 | * data = V | |
166 | * w = NULL | |
167 | * for (i = 1 to m) { | |
168 | * W = W || Hash(data) | |
169 | * data = (data + 1) mod (2^seedlen) | |
170 | * } | |
171 | * out = Leftmost(W, outlen) | |
172 | * | |
173 | * Returns zero if an error occurs otherwise it returns 1. | |
174 | */ | |
175 | static int hash_gen(RAND_DRBG *drbg, unsigned char *out, size_t outlen) | |
176 | { | |
177 | RAND_DRBG_HASH *hash = &drbg->data.hash; | |
178 | unsigned char one = 1; | |
179 | ||
180 | if (outlen == 0) | |
181 | return 1; | |
182 | memcpy(hash->vtmp, hash->V, drbg->seedlen); | |
183 | for(;;) { | |
184 | if (!EVP_DigestInit_ex(hash->ctx, hash->md, NULL) | |
185 | || !EVP_DigestUpdate(hash->ctx, hash->vtmp, drbg->seedlen)) | |
186 | return 0; | |
187 | ||
188 | if (outlen < hash->blocklen) { | |
189 | if (!EVP_DigestFinal(hash->ctx, hash->vtmp, NULL)) | |
190 | return 0; | |
191 | memcpy(out, hash->vtmp, outlen); | |
192 | return 1; | |
193 | } else { | |
194 | if (!EVP_DigestFinal(hash->ctx, out, NULL)) | |
195 | return 0; | |
196 | outlen -= hash->blocklen; | |
197 | if (outlen == 0) | |
198 | break; | |
199 | out += hash->blocklen; | |
200 | } | |
201 | add_bytes(drbg, hash->vtmp, &one, 1); | |
202 | } | |
203 | return 1; | |
204 | } | |
205 | ||
206 | /* | |
207 | * SP800-90Ar1 10.1.1.2 Hash_DRBG_Instantiate_Process: | |
208 | * | |
209 | * ent is entropy input obtained from a randomness source of length ent_len. | |
210 | * nonce is a string of bytes of length nonce_len. | |
211 | * pstr is a personalization string received from an application. May be NULL. | |
212 | * | |
213 | * Returns zero if an error occurs otherwise it returns 1. | |
214 | */ | |
215 | static int drbg_hash_instantiate(RAND_DRBG *drbg, | |
216 | const unsigned char *ent, size_t ent_len, | |
217 | const unsigned char *nonce, size_t nonce_len, | |
218 | const unsigned char *pstr, size_t pstr_len) | |
219 | { | |
220 | RAND_DRBG_HASH *hash = &drbg->data.hash; | |
221 | ||
222 | /* (Step 1-3) V = Hash_df(entropy||nonce||pers, seedlen) */ | |
223 | return hash_df(drbg, hash->V, INBYTE_IGNORE, | |
224 | ent, ent_len, nonce, nonce_len, pstr, pstr_len) | |
225 | /* (Step 4) C = Hash_df(0x00||V, seedlen) */ | |
226 | && hash_df1(drbg, hash->C, 0x00, hash->V, drbg->seedlen); | |
227 | } | |
228 | ||
229 | /* | |
230 | * SP800-90Ar1 10.1.1.3 Hash_DRBG_Reseed_Process: | |
231 | * | |
232 | * ent is entropy input bytes obtained from a randomness source. | |
233 | * addin is additional input received from an application. May be NULL. | |
234 | * | |
235 | * Returns zero if an error occurs otherwise it returns 1. | |
236 | */ | |
237 | static int drbg_hash_reseed(RAND_DRBG *drbg, | |
238 | const unsigned char *ent, size_t ent_len, | |
239 | const unsigned char *adin, size_t adin_len) | |
240 | { | |
241 | RAND_DRBG_HASH *hash = &drbg->data.hash; | |
242 | ||
243 | /* (Step 1-2) V = Hash_df(0x01 || V || entropy_input || additional_input)*/ | |
244 | /* V about to be updated so use C as output instead */ | |
245 | if (!hash_df(drbg, hash->C, 0x01, hash->V, drbg->seedlen, ent, ent_len, | |
246 | adin, adin_len)) | |
247 | return 0; | |
248 | memcpy(hash->V, hash->C, drbg->seedlen); | |
249 | /* (Step 4) C = Hash_df(0x00||V, seedlen) */ | |
250 | return hash_df1(drbg, hash->C, 0x00, hash->V, drbg->seedlen); | |
251 | } | |
252 | ||
253 | /* | |
254 | * SP800-90Ar1 10.1.1.4 Hash_DRBG_Generate_Process: | |
255 | * | |
256 | * Generates pseudo random bytes using the drbg. | |
257 | * out is a buffer to fill with outlen bytes of pseudo random data. | |
258 | * addin is additional input received from an application. May be NULL. | |
259 | * | |
260 | * Returns zero if an error occurs otherwise it returns 1. | |
261 | */ | |
262 | static int drbg_hash_generate(RAND_DRBG *drbg, | |
263 | unsigned char *out, size_t outlen, | |
264 | const unsigned char *adin, size_t adin_len) | |
265 | { | |
266 | RAND_DRBG_HASH *hash = &drbg->data.hash; | |
267 | unsigned char counter[4]; | |
268 | int reseed_counter = drbg->reseed_gen_counter; | |
269 | ||
270 | counter[0] = (unsigned char)((reseed_counter >> 24) & 0xff); | |
271 | counter[1] = (unsigned char)((reseed_counter >> 16) & 0xff); | |
272 | counter[2] = (unsigned char)((reseed_counter >> 8) & 0xff); | |
273 | counter[3] = (unsigned char)(reseed_counter & 0xff); | |
274 | ||
275 | return (adin == NULL | |
276 | /* (Step 2) if adin != NULL then V = V + Hash(0x02||V||adin) */ | |
277 | || adin_len == 0 | |
278 | || add_hash_to_v(drbg, 0x02, adin, adin_len)) | |
279 | /* (Step 3) Hashgen(outlen, V) */ | |
280 | && hash_gen(drbg, out, outlen) | |
281 | /* (Step 4/5) H = V = (V + Hash(0x03||V) mod (2^seedlen_bits) */ | |
282 | && add_hash_to_v(drbg, 0x03, NULL, 0) | |
283 | /* (Step 5) V = (V + H + C + reseed_counter) mod (2^seedlen_bits) */ | |
284 | /* V = (V + C) mod (2^seedlen_bits) */ | |
285 | && add_bytes(drbg, hash->V, hash->C, drbg->seedlen) | |
286 | /* V = (V + reseed_counter) mod (2^seedlen_bits) */ | |
287 | && add_bytes(drbg, hash->V, counter, 4); | |
288 | } | |
289 | ||
290 | static int drbg_hash_uninstantiate(RAND_DRBG *drbg) | |
291 | { | |
292 | EVP_MD_CTX_free(drbg->data.hash.ctx); | |
293 | OPENSSL_cleanse(&drbg->data.hash, sizeof(drbg->data.hash)); | |
294 | return 1; | |
295 | } | |
296 | ||
297 | static RAND_DRBG_METHOD drbg_hash_meth = { | |
298 | drbg_hash_instantiate, | |
299 | drbg_hash_reseed, | |
300 | drbg_hash_generate, | |
301 | drbg_hash_uninstantiate | |
302 | }; | |
303 | ||
304 | int drbg_hash_init(RAND_DRBG *drbg) | |
305 | { | |
306 | const EVP_MD *md; | |
307 | RAND_DRBG_HASH *hash = &drbg->data.hash; | |
308 | ||
309 | /* Any approved digest is allowed */ | |
310 | md = EVP_get_digestbynid(drbg->type); | |
311 | if (md == NULL) | |
312 | return 0; | |
313 | ||
314 | drbg->meth = &drbg_hash_meth; | |
315 | hash->md = md; | |
316 | ||
317 | if (hash->ctx == NULL) { | |
318 | hash->ctx = EVP_MD_CTX_new(); | |
319 | if (hash->ctx == NULL) | |
320 | return 0; | |
321 | } | |
322 | ||
323 | /* These are taken from SP 800-90 10.1 Table 2 */ | |
324 | hash->blocklen = EVP_MD_size(md); | |
325 | /* See SP800-57 Part1 Rev4 5.6.1 Table 3 */ | |
326 | drbg->strength = 64 * (hash->blocklen >> 3); | |
327 | if (drbg->strength > 256) | |
328 | drbg->strength = 256; | |
329 | if (hash->blocklen > MAX_BLOCKLEN_USING_SMALL_SEEDLEN) | |
330 | drbg->seedlen = HASH_PRNG_MAX_SEEDLEN; | |
331 | else | |
332 | drbg->seedlen = HASH_PRNG_SMALL_SEEDLEN; | |
333 | ||
334 | drbg->min_entropylen = drbg->strength / 8; | |
335 | drbg->max_entropylen = DRBG_MINMAX_FACTOR * drbg->min_entropylen; | |
336 | ||
337 | drbg->min_noncelen = drbg->min_entropylen / 2; | |
338 | drbg->max_noncelen = DRBG_MINMAX_FACTOR * drbg->min_noncelen; | |
339 | ||
340 | drbg->max_perslen = DRBG_MAX_LENGTH; | |
341 | drbg->max_adinlen = DRBG_MAX_LENGTH; | |
342 | ||
343 | /* Maximum number of bits per request = 2^19 = 2^16 bytes */ | |
344 | drbg->max_request = 1 << 16; | |
345 | ||
346 | return 1; | |
347 | } |