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Commit | Line | Data |
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aa6bb135 | 1 | /* |
a38c878c | 2 | * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved. |
d02b48c6 | 3 | * |
e38873f5 | 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use |
aa6bb135 RS |
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 | |
d02b48c6 RE |
8 | */ |
9 | ||
10 | #include <stdio.h> | |
b39fc560 | 11 | #include "internal/cryptlib.h" |
0aeddcfa | 12 | #include "dh_locl.h" |
25f2138b | 13 | #include "crypto/bn.h" |
d02b48c6 | 14 | |
13066cee | 15 | static int generate_key(DH *dh); |
f971ccb2 RL |
16 | static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh); |
17 | static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, | |
0f113f3e MC |
18 | const BIGNUM *a, const BIGNUM *p, |
19 | const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); | |
13066cee DSH |
20 | static int dh_init(DH *dh); |
21 | static int dh_finish(DH *dh); | |
22 | ||
6b691a5c | 23 | int DH_generate_key(DH *dh) |
0f113f3e MC |
24 | { |
25 | return dh->meth->generate_key(dh); | |
26 | } | |
13066cee | 27 | |
f971ccb2 | 28 | int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) |
0f113f3e MC |
29 | { |
30 | return dh->meth->compute_key(key, pub_key, dh); | |
31 | } | |
13066cee | 32 | |
bc91494e | 33 | int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh) |
0f113f3e MC |
34 | { |
35 | int rv, pad; | |
36 | rv = dh->meth->compute_key(key, pub_key, dh); | |
37 | if (rv <= 0) | |
38 | return rv; | |
39 | pad = BN_num_bytes(dh->p) - rv; | |
40 | if (pad > 0) { | |
41 | memmove(key + pad, key, rv); | |
42 | memset(key, 0, pad); | |
43 | } | |
44 | return rv + pad; | |
45 | } | |
bc91494e | 46 | |
13066cee | 47 | static DH_METHOD dh_ossl = { |
0f113f3e MC |
48 | "OpenSSL DH Method", |
49 | generate_key, | |
50 | compute_key, | |
51 | dh_bn_mod_exp, | |
52 | dh_init, | |
53 | dh_finish, | |
54 | DH_FLAG_FIPS_METHOD, | |
55 | NULL, | |
56 | NULL | |
13066cee DSH |
57 | }; |
58 | ||
076fc555 RS |
59 | static const DH_METHOD *default_DH_method = &dh_ossl; |
60 | ||
f971ccb2 | 61 | const DH_METHOD *DH_OpenSSL(void) |
13066cee | 62 | { |
0f113f3e | 63 | return &dh_ossl; |
13066cee DSH |
64 | } |
65 | ||
076fc555 RS |
66 | void DH_set_default_method(const DH_METHOD *meth) |
67 | { | |
68 | default_DH_method = meth; | |
69 | } | |
70 | ||
71 | const DH_METHOD *DH_get_default_method(void) | |
72 | { | |
73 | return default_DH_method; | |
74 | } | |
75 | ||
13066cee | 76 | static int generate_key(DH *dh) |
0f113f3e MC |
77 | { |
78 | int ok = 0; | |
79 | int generate_new_key = 0; | |
80 | unsigned l; | |
91f7361f | 81 | BN_CTX *ctx = NULL; |
0f113f3e MC |
82 | BN_MONT_CTX *mont = NULL; |
83 | BIGNUM *pub_key = NULL, *priv_key = NULL; | |
d02b48c6 | 84 | |
91f7361f GV |
85 | if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { |
86 | DHerr(DH_F_GENERATE_KEY, DH_R_MODULUS_TOO_LARGE); | |
87 | return 0; | |
88 | } | |
89 | ||
6de1fe90 BE |
90 | if (BN_num_bits(dh->p) < DH_MIN_MODULUS_BITS) { |
91 | DHerr(DH_F_GENERATE_KEY, DH_R_MODULUS_TOO_SMALL); | |
92 | return 0; | |
93 | } | |
94 | ||
0f113f3e MC |
95 | ctx = BN_CTX_new(); |
96 | if (ctx == NULL) | |
97 | goto err; | |
d02b48c6 | 98 | |
0f113f3e | 99 | if (dh->priv_key == NULL) { |
74924dcb | 100 | priv_key = BN_secure_new(); |
0f113f3e MC |
101 | if (priv_key == NULL) |
102 | goto err; | |
103 | generate_new_key = 1; | |
104 | } else | |
105 | priv_key = dh->priv_key; | |
d02b48c6 | 106 | |
0f113f3e MC |
107 | if (dh->pub_key == NULL) { |
108 | pub_key = BN_new(); | |
109 | if (pub_key == NULL) | |
110 | goto err; | |
111 | } else | |
112 | pub_key = dh->pub_key; | |
d02b48c6 | 113 | |
0f113f3e MC |
114 | if (dh->flags & DH_FLAG_CACHE_MONT_P) { |
115 | mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, | |
d188a536 | 116 | dh->lock, dh->p, ctx); |
0f113f3e MC |
117 | if (!mont) |
118 | goto err; | |
119 | } | |
6ec8e63a | 120 | |
0f113f3e MC |
121 | if (generate_new_key) { |
122 | if (dh->q) { | |
123 | do { | |
ddc6a5c8 | 124 | if (!BN_priv_rand_range(priv_key, dh->q)) |
0f113f3e MC |
125 | goto err; |
126 | } | |
127 | while (BN_is_zero(priv_key) || BN_is_one(priv_key)); | |
128 | } else { | |
129 | /* secret exponent length */ | |
130 | l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; | |
ddc6a5c8 | 131 | if (!BN_priv_rand(priv_key, l, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY)) |
0f113f3e | 132 | goto err; |
a38c878c BE |
133 | /* |
134 | * We handle just one known case where g is a quadratic non-residue: | |
135 | * for g = 2: p % 8 == 3 | |
136 | */ | |
137 | if (BN_is_word(dh->g, DH_GENERATOR_2) && !BN_is_bit_set(dh->p, 2)) { | |
138 | /* clear bit 0, since it won't be a secret anyway */ | |
139 | if (!BN_clear_bit(priv_key, 0)) | |
140 | goto err; | |
141 | } | |
0f113f3e MC |
142 | } |
143 | } | |
dfeab068 | 144 | |
0f113f3e | 145 | { |
5584f65a | 146 | BIGNUM *prk = BN_new(); |
46a64376 | 147 | |
5584f65a MC |
148 | if (prk == NULL) |
149 | goto err; | |
150 | BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME); | |
46a64376 | 151 | |
0f113f3e | 152 | if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) { |
a38c878c | 153 | BN_clear_free(prk); |
0f113f3e MC |
154 | goto err; |
155 | } | |
5584f65a | 156 | /* We MUST free prk before any further use of priv_key */ |
a38c878c | 157 | BN_clear_free(prk); |
0f113f3e | 158 | } |
46a64376 | 159 | |
0f113f3e MC |
160 | dh->pub_key = pub_key; |
161 | dh->priv_key = priv_key; | |
8b84b075 | 162 | dh->dirty_cnt++; |
0f113f3e MC |
163 | ok = 1; |
164 | err: | |
165 | if (ok != 1) | |
166 | DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB); | |
d02b48c6 | 167 | |
23a1d5e9 | 168 | if (pub_key != dh->pub_key) |
0f113f3e | 169 | BN_free(pub_key); |
23a1d5e9 | 170 | if (priv_key != dh->priv_key) |
0f113f3e MC |
171 | BN_free(priv_key); |
172 | BN_CTX_free(ctx); | |
26a7d938 | 173 | return ok; |
0f113f3e | 174 | } |
d02b48c6 | 175 | |
f971ccb2 | 176 | static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh) |
0f113f3e MC |
177 | { |
178 | BN_CTX *ctx = NULL; | |
179 | BN_MONT_CTX *mont = NULL; | |
180 | BIGNUM *tmp; | |
181 | int ret = -1; | |
182 | int check_result; | |
d02b48c6 | 183 | |
0f113f3e MC |
184 | if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) { |
185 | DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE); | |
186 | goto err; | |
187 | } | |
5e3225cc | 188 | |
6de1fe90 BE |
189 | if (BN_num_bits(dh->p) < DH_MIN_MODULUS_BITS) { |
190 | DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_SMALL); | |
191 | return 0; | |
192 | } | |
193 | ||
0f113f3e MC |
194 | ctx = BN_CTX_new(); |
195 | if (ctx == NULL) | |
196 | goto err; | |
197 | BN_CTX_start(ctx); | |
198 | tmp = BN_CTX_get(ctx); | |
7928ee4d BE |
199 | if (tmp == NULL) |
200 | goto err; | |
6ec8e63a | 201 | |
0f113f3e MC |
202 | if (dh->priv_key == NULL) { |
203 | DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE); | |
204 | goto err; | |
205 | } | |
dfeab068 | 206 | |
0f113f3e MC |
207 | if (dh->flags & DH_FLAG_CACHE_MONT_P) { |
208 | mont = BN_MONT_CTX_set_locked(&dh->method_mont_p, | |
d188a536 | 209 | dh->lock, dh->p, ctx); |
5584f65a | 210 | BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME); |
0f113f3e MC |
211 | if (!mont) |
212 | goto err; | |
213 | } | |
bf3d6c0c | 214 | |
0f113f3e MC |
215 | if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) { |
216 | DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY); | |
217 | goto err; | |
218 | } | |
d02b48c6 | 219 | |
0f113f3e MC |
220 | if (!dh-> |
221 | meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) { | |
222 | DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB); | |
223 | goto err; | |
224 | } | |
13066cee | 225 | |
0f113f3e MC |
226 | ret = BN_bn2bin(tmp, key); |
227 | err: | |
ce1415ed SL |
228 | BN_CTX_end(ctx); |
229 | BN_CTX_free(ctx); | |
26a7d938 | 230 | return ret; |
0f113f3e | 231 | } |
6dad7bd6 | 232 | |
0f113f3e MC |
233 | static int dh_bn_mod_exp(const DH *dh, BIGNUM *r, |
234 | const BIGNUM *a, const BIGNUM *p, | |
235 | const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx) | |
236 | { | |
5584f65a | 237 | return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx); |
0f113f3e | 238 | } |
13066cee DSH |
239 | |
240 | static int dh_init(DH *dh) | |
0f113f3e MC |
241 | { |
242 | dh->flags |= DH_FLAG_CACHE_MONT_P; | |
208fb891 | 243 | return 1; |
0f113f3e | 244 | } |
13066cee DSH |
245 | |
246 | static int dh_finish(DH *dh) | |
0f113f3e | 247 | { |
23a1d5e9 | 248 | BN_MONT_CTX_free(dh->method_mont_p); |
208fb891 | 249 | return 1; |
0f113f3e | 250 | } |
9aaecbfc | 251 | |
252 | int dh_buf2key(DH *dh, const unsigned char *buf, size_t len) | |
253 | { | |
254 | int err_reason = DH_R_BN_ERROR; | |
255 | BIGNUM *pubkey = NULL; | |
256 | const BIGNUM *p; | |
257 | size_t p_size; | |
258 | ||
259 | if ((pubkey = BN_bin2bn(buf, len, NULL)) == NULL) | |
260 | goto err; | |
261 | DH_get0_pqg(dh, &p, NULL, NULL); | |
262 | if (p == NULL || (p_size = BN_num_bytes(p)) == 0) { | |
263 | err_reason = DH_R_NO_PARAMETERS_SET; | |
264 | goto err; | |
265 | } | |
266 | /* | |
267 | * As per Section 4.2.8.1 of RFC 8446 fail if DHE's | |
268 | * public key is of size not equal to size of p | |
269 | */ | |
270 | if (BN_is_zero(pubkey) || p_size != len) { | |
271 | err_reason = DH_R_INVALID_PUBKEY; | |
272 | goto err; | |
273 | } | |
274 | if (DH_set0_key(dh, pubkey, NULL) != 1) | |
275 | goto err; | |
276 | return 1; | |
277 | err: | |
278 | DHerr(DH_F_DH_BUF2KEY, err_reason); | |
279 | BN_free(pubkey); | |
280 | return 0; | |
281 | } | |
282 | ||
283 | size_t dh_key2buf(const DH *dh, unsigned char **pbuf_out) | |
284 | { | |
285 | const BIGNUM *pubkey; | |
286 | unsigned char *pbuf; | |
287 | const BIGNUM *p; | |
288 | int p_size; | |
289 | ||
290 | DH_get0_pqg(dh, &p, NULL, NULL); | |
291 | DH_get0_key(dh, &pubkey, NULL); | |
292 | if (p == NULL || pubkey == NULL | |
293 | || (p_size = BN_num_bytes(p)) == 0 | |
294 | || BN_num_bytes(pubkey) == 0) { | |
295 | DHerr(DH_F_DH_KEY2BUF, DH_R_INVALID_PUBKEY); | |
296 | return 0; | |
297 | } | |
298 | if ((pbuf = OPENSSL_malloc(p_size)) == NULL) { | |
299 | DHerr(DH_F_DH_KEY2BUF, ERR_R_MALLOC_FAILURE); | |
300 | return 0; | |
301 | } | |
302 | /* | |
303 | * As per Section 4.2.8.1 of RFC 8446 left pad public | |
304 | * key with zeros to the size of p | |
305 | */ | |
306 | if (BN_bn2binpad(pubkey, pbuf, p_size) < 0) { | |
307 | OPENSSL_free(pbuf); | |
308 | DHerr(DH_F_DH_KEY2BUF, DH_R_BN_ERROR); | |
309 | return 0; | |
310 | } | |
311 | *pbuf_out = pbuf; | |
312 | return p_size; | |
313 | } |