diffie-hellman: Use bool instead of status_t as get_shared_secret() return value
[strongswan.git] / src / libstrongswan / plugins / gmp / gmp_diffie_hellman.c
1 /*
2 * Copyright (C) 1998-2002 D. Hugh Redelmeier.
3 * Copyright (C) 1999, 2000, 2001 Henry Spencer.
4 * Copyright (C) 2010 Tobias Brunner
5 * Copyright (C) 2005-2008 Martin Willi
6 * Copyright (C) 2005 Jan Hutter
7 * Hochschule fuer Technik Rapperswil
8 *
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms of the GNU General Public License as published by the
11 * Free Software Foundation; either version 2 of the License, or (at your
12 * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
13 *
14 * This program is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 * for more details.
18 */
19
20 #include <gmp.h>
21
22 #include "gmp_diffie_hellman.h"
23
24 #include <utils/debug.h>
25
26 #ifdef HAVE_MPZ_POWM_SEC
27 # undef mpz_powm
28 # define mpz_powm mpz_powm_sec
29 #endif
30
31 typedef struct private_gmp_diffie_hellman_t private_gmp_diffie_hellman_t;
32
33 /**
34 * Private data of an gmp_diffie_hellman_t object.
35 */
36 struct private_gmp_diffie_hellman_t {
37 /**
38 * Public gmp_diffie_hellman_t interface.
39 */
40 gmp_diffie_hellman_t public;
41
42 /**
43 * Diffie Hellman group number.
44 */
45 diffie_hellman_group_t group;
46
47 /*
48 * Generator value.
49 */
50 mpz_t g;
51
52 /**
53 * My private value.
54 */
55 mpz_t xa;
56
57 /**
58 * My public value.
59 */
60 mpz_t ya;
61
62 /**
63 * Other public value.
64 */
65 mpz_t yb;
66
67 /**
68 * Shared secret.
69 */
70 mpz_t zz;
71
72 /**
73 * Modulus.
74 */
75 mpz_t p;
76
77 /**
78 * Modulus length.
79 */
80 size_t p_len;
81
82 /**
83 * True if shared secret is computed and stored in my_public_value.
84 */
85 bool computed;
86 };
87
88 METHOD(diffie_hellman_t, set_other_public_value, void,
89 private_gmp_diffie_hellman_t *this, chunk_t value)
90 {
91 mpz_t p_min_1;
92
93 mpz_init(p_min_1);
94 mpz_sub_ui(p_min_1, this->p, 1);
95
96 mpz_import(this->yb, value.len, 1, 1, 1, 0, value.ptr);
97
98 /* check public value:
99 * 1. 0 or 1 is invalid as 0^a = 0 and 1^a = 1
100 * 2. a public value larger or equal the modulus is invalid */
101 if (mpz_cmp_ui(this->yb, 1) > 0 &&
102 mpz_cmp(this->yb, p_min_1) < 0)
103 {
104 #ifdef EXTENDED_DH_TEST
105 /* 3. test if y ^ q mod p = 1, where q = (p - 1)/2. */
106 mpz_t q, one;
107 diffie_hellman_params_t *params;
108
109 mpz_init(q);
110 mpz_init(one);
111
112 params = diffie_hellman_get_params(this->group);
113 if (!params->subgroup.len)
114 {
115 mpz_fdiv_q_2exp(q, p_min_1, 1);
116 }
117 else
118 {
119 mpz_import(q, params->subgroup.len, 1, 1, 1, 0, params->subgroup.ptr);
120 }
121 mpz_powm(one, this->yb, q, this->p);
122 mpz_clear(q);
123 if (mpz_cmp_ui(one, 1) == 0)
124 {
125 mpz_powm(this->zz, this->yb, this->xa, this->p);
126 this->computed = TRUE;
127 }
128 else
129 {
130 DBG1(DBG_LIB, "public DH value verification failed:"
131 " y ^ q mod p != 1");
132 }
133 mpz_clear(one);
134 #else
135 mpz_powm(this->zz, this->yb, this->xa, this->p);
136 this->computed = TRUE;
137 #endif
138 }
139 else
140 {
141 DBG1(DBG_LIB, "public DH value verification failed:"
142 " y < 2 || y > p - 1 ");
143 }
144 mpz_clear(p_min_1);
145 }
146
147 METHOD(diffie_hellman_t, get_my_public_value, void,
148 private_gmp_diffie_hellman_t *this,chunk_t *value)
149 {
150 value->len = this->p_len;
151 value->ptr = mpz_export(NULL, NULL, 1, value->len, 1, 0, this->ya);
152 if (value->ptr == NULL)
153 {
154 value->len = 0;
155 }
156 }
157
158 METHOD(diffie_hellman_t, get_shared_secret, bool,
159 private_gmp_diffie_hellman_t *this, chunk_t *secret)
160 {
161 if (!this->computed)
162 {
163 return FALSE;
164 }
165 secret->len = this->p_len;
166 secret->ptr = mpz_export(NULL, NULL, 1, secret->len, 1, 0, this->zz);
167 if (secret->ptr == NULL)
168 {
169 return FALSE;
170 }
171 return TRUE;
172 }
173
174 METHOD(diffie_hellman_t, get_dh_group, diffie_hellman_group_t,
175 private_gmp_diffie_hellman_t *this)
176 {
177 return this->group;
178 }
179
180 METHOD(diffie_hellman_t, destroy, void,
181 private_gmp_diffie_hellman_t *this)
182 {
183 mpz_clear(this->p);
184 mpz_clear(this->xa);
185 mpz_clear(this->ya);
186 mpz_clear(this->yb);
187 mpz_clear(this->zz);
188 mpz_clear(this->g);
189 free(this);
190 }
191
192 /**
193 * Generic internal constructor
194 */
195 static gmp_diffie_hellman_t *create_generic(diffie_hellman_group_t group,
196 size_t exp_len, chunk_t g, chunk_t p)
197 {
198 private_gmp_diffie_hellman_t *this;
199 chunk_t random;
200 rng_t *rng;
201
202 INIT(this,
203 .public = {
204 .dh = {
205 .get_shared_secret = _get_shared_secret,
206 .set_other_public_value = _set_other_public_value,
207 .get_my_public_value = _get_my_public_value,
208 .get_dh_group = _get_dh_group,
209 .destroy = _destroy,
210 },
211 },
212 .group = group,
213 .p_len = p.len,
214 );
215
216 mpz_init(this->p);
217 mpz_init(this->yb);
218 mpz_init(this->ya);
219 mpz_init(this->xa);
220 mpz_init(this->zz);
221 mpz_init(this->g);
222 mpz_import(this->g, g.len, 1, 1, 1, 0, g.ptr);
223 mpz_import(this->p, p.len, 1, 1, 1, 0, p.ptr);
224
225 rng = lib->crypto->create_rng(lib->crypto, RNG_STRONG);
226 if (!rng)
227 {
228 DBG1(DBG_LIB, "no RNG found for quality %N", rng_quality_names,
229 RNG_STRONG);
230 destroy(this);
231 return NULL;
232 }
233 if (!rng->allocate_bytes(rng, exp_len, &random))
234 {
235 DBG1(DBG_LIB, "failed to allocate DH secret");
236 rng->destroy(rng);
237 destroy(this);
238 return NULL;
239 }
240 rng->destroy(rng);
241
242 if (exp_len == this->p_len)
243 {
244 /* achieve bitsof(p)-1 by setting MSB to 0 */
245 *random.ptr &= 0x7F;
246 }
247 mpz_import(this->xa, random.len, 1, 1, 1, 0, random.ptr);
248 chunk_free(&random);
249 DBG2(DBG_LIB, "size of DH secret exponent: %u bits",
250 mpz_sizeinbase(this->xa, 2));
251
252 mpz_powm(this->ya, this->g, this->xa, this->p);
253
254 return &this->public;
255 }
256
257 /*
258 * Described in header.
259 */
260 gmp_diffie_hellman_t *gmp_diffie_hellman_create(diffie_hellman_group_t group)
261 {
262 diffie_hellman_params_t *params;
263
264 params = diffie_hellman_get_params(group);
265 if (!params)
266 {
267 return NULL;
268 }
269 return create_generic(group, params->exp_len,
270 params->generator, params->prime);
271 }
272
273
274 gmp_diffie_hellman_t *gmp_diffie_hellman_create_custom(
275 diffie_hellman_group_t group, chunk_t g, chunk_t p)
276 {
277 if (group == MODP_CUSTOM)
278 {
279 return create_generic(MODP_CUSTOM, p.len, g, p);
280 }
281 return NULL;
282 }