1 /*
2 * Copyright 1995-2019 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 <stdio.h>
11 #include "internal/cryptlib.h"
12 #include <openssl/bn.h>
13 #include "dh_local.h"
14
15 # define DH_NUMBER_ITERATIONS_FOR_PRIME 64
16
17 /*-
18 * Check that p and g are suitable enough
19 *
20 * p is odd
21 * 1 < g < p - 1
22 */
DH_check_params_ex(const DH * dh)23 int DH_check_params_ex(const DH *dh)
24 {
25 int errflags = 0;
26
27 if (!DH_check_params(dh, &errflags))
28 return 0;
29
30 if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
31 DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_CHECK_P_NOT_PRIME);
32 if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
33 DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_NOT_SUITABLE_GENERATOR);
34
35 return errflags == 0;
36 }
37
DH_check_params(const DH * dh,int * ret)38 int DH_check_params(const DH *dh, int *ret)
39 {
40 int ok = 0;
41 BIGNUM *tmp = NULL;
42 BN_CTX *ctx = NULL;
43
44 *ret = 0;
45 ctx = BN_CTX_new();
46 if (ctx == NULL)
47 goto err;
48 BN_CTX_start(ctx);
49 tmp = BN_CTX_get(ctx);
50 if (tmp == NULL)
51 goto err;
52
53 if (!BN_is_odd(dh->p))
54 *ret |= DH_CHECK_P_NOT_PRIME;
55 if (BN_is_negative(dh->g) || BN_is_zero(dh->g) || BN_is_one(dh->g))
56 *ret |= DH_NOT_SUITABLE_GENERATOR;
57 if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
58 goto err;
59 if (BN_cmp(dh->g, tmp) >= 0)
60 *ret |= DH_NOT_SUITABLE_GENERATOR;
61
62 ok = 1;
63 err:
64 BN_CTX_end(ctx);
65 BN_CTX_free(ctx);
66 return ok;
67 }
68
69 /*-
70 * Check that p is a safe prime and
71 * g is a suitable generator.
72 */
DH_check_ex(const DH * dh)73 int DH_check_ex(const DH *dh)
74 {
75 int errflags = 0;
76
77 if (!DH_check(dh, &errflags))
78 return 0;
79
80 if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
81 DHerr(DH_F_DH_CHECK_EX, DH_R_NOT_SUITABLE_GENERATOR);
82 if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)
83 DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_Q_NOT_PRIME);
84 if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)
85 DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_Q_VALUE);
86 if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)
87 DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_J_VALUE);
88 if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
89 DHerr(DH_F_DH_CHECK_EX, DH_R_UNABLE_TO_CHECK_GENERATOR);
90 if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
91 DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_PRIME);
92 if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
93 DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_SAFE_PRIME);
94
95 return errflags == 0;
96 }
97
DH_check(const DH * dh,int * ret)98 int DH_check(const DH *dh, int *ret)
99 {
100 int ok = 0, r;
101 BN_CTX *ctx = NULL;
102 BIGNUM *t1 = NULL, *t2 = NULL;
103
104 if (!DH_check_params(dh, ret))
105 return 0;
106
107 ctx = BN_CTX_new();
108 if (ctx == NULL)
109 goto err;
110 BN_CTX_start(ctx);
111 t1 = BN_CTX_get(ctx);
112 t2 = BN_CTX_get(ctx);
113 if (t2 == NULL)
114 goto err;
115
116 if (dh->q) {
117 if (BN_cmp(dh->g, BN_value_one()) <= 0)
118 *ret |= DH_NOT_SUITABLE_GENERATOR;
119 else if (BN_cmp(dh->g, dh->p) >= 0)
120 *ret |= DH_NOT_SUITABLE_GENERATOR;
121 else {
122 /* Check g^q == 1 mod p */
123 if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
124 goto err;
125 if (!BN_is_one(t1))
126 *ret |= DH_NOT_SUITABLE_GENERATOR;
127 }
128 r = BN_is_prime_ex(dh->q, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
129 if (r < 0)
130 goto err;
131 if (!r)
132 *ret |= DH_CHECK_Q_NOT_PRIME;
133 /* Check p == 1 mod q i.e. q divides p - 1 */
134 if (!BN_div(t1, t2, dh->p, dh->q, ctx))
135 goto err;
136 if (!BN_is_one(t2))
137 *ret |= DH_CHECK_INVALID_Q_VALUE;
138 if (dh->j && BN_cmp(dh->j, t1))
139 *ret |= DH_CHECK_INVALID_J_VALUE;
140 }
141
142 r = BN_is_prime_ex(dh->p, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
143 if (r < 0)
144 goto err;
145 if (!r)
146 *ret |= DH_CHECK_P_NOT_PRIME;
147 else if (!dh->q) {
148 if (!BN_rshift1(t1, dh->p))
149 goto err;
150 r = BN_is_prime_ex(t1, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
151 if (r < 0)
152 goto err;
153 if (!r)
154 *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
155 }
156 ok = 1;
157 err:
158 BN_CTX_end(ctx);
159 BN_CTX_free(ctx);
160 return ok;
161 }
162
DH_check_pub_key_ex(const DH * dh,const BIGNUM * pub_key)163 int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
164 {
165 int errflags = 0;
166
167 if (!DH_check_pub_key(dh, pub_key, &errflags))
168 return 0;
169
170 if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
171 DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_SMALL);
172 if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
173 DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_LARGE);
174 if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
175 DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_INVALID);
176
177 return errflags == 0;
178 }
179
DH_check_pub_key(const DH * dh,const BIGNUM * pub_key,int * ret)180 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
181 {
182 int ok = 0;
183 BIGNUM *tmp = NULL;
184 BN_CTX *ctx = NULL;
185
186 *ret = 0;
187 ctx = BN_CTX_new();
188 if (ctx == NULL)
189 goto err;
190 BN_CTX_start(ctx);
191 tmp = BN_CTX_get(ctx);
192 if (tmp == NULL || !BN_set_word(tmp, 1))
193 goto err;
194 if (BN_cmp(pub_key, tmp) <= 0)
195 *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
196 if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
197 goto err;
198 if (BN_cmp(pub_key, tmp) >= 0)
199 *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
200
201 if (dh->q != NULL) {
202 /* Check pub_key^q == 1 mod p */
203 if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx))
204 goto err;
205 if (!BN_is_one(tmp))
206 *ret |= DH_CHECK_PUBKEY_INVALID;
207 }
208
209 ok = 1;
210 err:
211 BN_CTX_end(ctx);
212 BN_CTX_free(ctx);
213 return ok;
214 }
215