1 /* Copyright (C) 1995-1998 Eric Young ([email protected])
2 * All rights reserved.
3 *
4 * This package is an SSL implementation written
5 * by Eric Young ([email protected]).
6 * The implementation was written so as to conform with Netscapes SSL.
7 *
8 * This library is free for commercial and non-commercial use as long as
9 * the following conditions are aheared to. The following conditions
10 * apply to all code found in this distribution, be it the RC4, RSA,
11 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
12 * included with this distribution is covered by the same copyright terms
13 * except that the holder is Tim Hudson ([email protected]).
14 *
15 * Copyright remains Eric Young's, and as such any Copyright notices in
16 * the code are not to be removed.
17 * If this package is used in a product, Eric Young should be given attribution
18 * as the author of the parts of the library used.
19 * This can be in the form of a textual message at program startup or
20 * in documentation (online or textual) provided with the package.
21 *
22 * Redistribution and use in source and binary forms, with or without
23 * modification, are permitted provided that the following conditions
24 * are met:
25 * 1. Redistributions of source code must retain the copyright
26 * notice, this list of conditions and the following disclaimer.
27 * 2. Redistributions in binary form must reproduce the above copyright
28 * notice, this list of conditions and the following disclaimer in the
29 * documentation and/or other materials provided with the distribution.
30 * 3. All advertising materials mentioning features or use of this software
31 * must display the following acknowledgement:
32 * "This product includes cryptographic software written by
33 * Eric Young ([email protected])"
34 * The word 'cryptographic' can be left out if the rouines from the library
35 * being used are not cryptographic related :-).
36 * 4. If you include any Windows specific code (or a derivative thereof) from
37 * the apps directory (application code) you must include an acknowledgement:
38 * "This product includes software written by Tim Hudson ([email protected])"
39 *
40 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
41 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
42 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
43 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
44 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
45 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
46 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
48 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
49 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50 * SUCH DAMAGE.
51 *
52 * The licence and distribution terms for any publically available version or
53 * derivative of this code cannot be changed. i.e. this code cannot simply be
54 * copied and put under another distribution licence
55 * [including the GNU Public Licence.] */
56
57 #include <openssl/dh.h>
58
59 #include <openssl/bn.h>
60 #include <openssl/err.h>
61
62 #include "internal.h"
63
64
dh_check_params_fast(const DH * dh)65 int dh_check_params_fast(const DH *dh) {
66 // Most operations scale with p and q.
67 if (BN_is_negative(dh->p) || !BN_is_odd(dh->p) ||
68 BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
69 OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PARAMETERS);
70 return 0;
71 }
72
73 // q must be bounded by p.
74 if (dh->q != NULL && (BN_is_negative(dh->q) || BN_ucmp(dh->q, dh->p) > 0)) {
75 OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PARAMETERS);
76 return 0;
77 }
78
79 // g must be an element of p's multiplicative group.
80 if (BN_is_negative(dh->g) || BN_is_zero(dh->g) ||
81 BN_ucmp(dh->g, dh->p) >= 0) {
82 OPENSSL_PUT_ERROR(DH, DH_R_INVALID_PARAMETERS);
83 return 0;
84 }
85
86 return 1;
87 }
88
DH_check_pub_key(const DH * dh,const BIGNUM * pub_key,int * out_flags)89 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *out_flags) {
90 *out_flags = 0;
91 if (!dh_check_params_fast(dh)) {
92 return 0;
93 }
94
95 BN_CTX *ctx = BN_CTX_new();
96 if (ctx == NULL) {
97 return 0;
98 }
99 BN_CTX_start(ctx);
100
101 int ok = 0;
102
103 // Check |pub_key| is greater than 1.
104 if (BN_cmp(pub_key, BN_value_one()) <= 0) {
105 *out_flags |= DH_CHECK_PUBKEY_TOO_SMALL;
106 }
107
108 // Check |pub_key| is less than |dh->p| - 1.
109 BIGNUM *tmp = BN_CTX_get(ctx);
110 if (tmp == NULL ||
111 !BN_copy(tmp, dh->p) ||
112 !BN_sub_word(tmp, 1)) {
113 goto err;
114 }
115 if (BN_cmp(pub_key, tmp) >= 0) {
116 *out_flags |= DH_CHECK_PUBKEY_TOO_LARGE;
117 }
118
119 if (dh->q != NULL) {
120 // Check |pub_key|^|dh->q| is 1 mod |dh->p|. This is necessary for RFC 5114
121 // groups which are not safe primes but pick a generator on a prime-order
122 // subgroup of size |dh->q|.
123 if (!BN_mod_exp_mont(tmp, pub_key, dh->q, dh->p, ctx, NULL)) {
124 goto err;
125 }
126 if (!BN_is_one(tmp)) {
127 *out_flags |= DH_CHECK_PUBKEY_INVALID;
128 }
129 }
130
131 ok = 1;
132
133 err:
134 BN_CTX_end(ctx);
135 BN_CTX_free(ctx);
136 return ok;
137 }
138
139
DH_check(const DH * dh,int * out_flags)140 int DH_check(const DH *dh, int *out_flags) {
141 *out_flags = 0;
142 if (!dh_check_params_fast(dh)) {
143 return 0;
144 }
145
146 // Check that p is a safe prime and if g is 2, 3 or 5, check that it is a
147 // suitable generator where:
148 // for 2, p mod 24 == 11
149 // for 3, p mod 12 == 5
150 // for 5, p mod 10 == 3 or 7
151 // should hold.
152 int ok = 0, r;
153 BN_CTX *ctx = NULL;
154 BN_ULONG l;
155 BIGNUM *t1 = NULL, *t2 = NULL;
156
157 ctx = BN_CTX_new();
158 if (ctx == NULL) {
159 goto err;
160 }
161 BN_CTX_start(ctx);
162 t1 = BN_CTX_get(ctx);
163 if (t1 == NULL) {
164 goto err;
165 }
166 t2 = BN_CTX_get(ctx);
167 if (t2 == NULL) {
168 goto err;
169 }
170
171 if (dh->q) {
172 if (BN_cmp(dh->g, BN_value_one()) <= 0) {
173 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
174 } else if (BN_cmp(dh->g, dh->p) >= 0) {
175 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
176 } else {
177 // Check g^q == 1 mod p
178 if (!BN_mod_exp_mont(t1, dh->g, dh->q, dh->p, ctx, NULL)) {
179 goto err;
180 }
181 if (!BN_is_one(t1)) {
182 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
183 }
184 }
185 r = BN_is_prime_ex(dh->q, BN_prime_checks_for_validation, ctx, NULL);
186 if (r < 0) {
187 goto err;
188 }
189 if (!r) {
190 *out_flags |= DH_CHECK_Q_NOT_PRIME;
191 }
192 // Check p == 1 mod q i.e. q divides p - 1
193 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) {
194 goto err;
195 }
196 if (!BN_is_one(t2)) {
197 *out_flags |= DH_CHECK_INVALID_Q_VALUE;
198 }
199 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
200 l = BN_mod_word(dh->p, 24);
201 if (l == (BN_ULONG)-1) {
202 goto err;
203 }
204 if (l != 11) {
205 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
206 }
207 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
208 l = BN_mod_word(dh->p, 10);
209 if (l == (BN_ULONG)-1) {
210 goto err;
211 }
212 if (l != 3 && l != 7) {
213 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
214 }
215 } else {
216 *out_flags |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR;
217 }
218
219 r = BN_is_prime_ex(dh->p, BN_prime_checks_for_validation, ctx, NULL);
220 if (r < 0) {
221 goto err;
222 }
223 if (!r) {
224 *out_flags |= DH_CHECK_P_NOT_PRIME;
225 } else if (!dh->q) {
226 if (!BN_rshift1(t1, dh->p)) {
227 goto err;
228 }
229 r = BN_is_prime_ex(t1, BN_prime_checks_for_validation, ctx, NULL);
230 if (r < 0) {
231 goto err;
232 }
233 if (!r) {
234 *out_flags |= DH_CHECK_P_NOT_SAFE_PRIME;
235 }
236 }
237 ok = 1;
238
239 err:
240 if (ctx != NULL) {
241 BN_CTX_end(ctx);
242 BN_CTX_free(ctx);
243 }
244 return ok;
245 }
246