crypto/dh/dh_check.c

   1 /*
   2  * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the Apache License 2.0 (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_locl.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  */
  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     if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
  35         DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_MODULUS_TOO_SMALL);
  36     if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
  37         DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_MODULUS_TOO_LARGE);
  38
  39     return errflags == 0;
  40 }
  41
  42 int DH_check_params(const DH *dh, int *ret)
  43 {
  44     int ok = 0;
  45     BIGNUM *tmp = NULL;
  46     BN_CTX *ctx = NULL;
  47
  48     *ret = 0;
  49     ctx = BN_CTX_new();
  50     if (ctx == NULL)
  51         goto err;
  52     BN_CTX_start(ctx);
  53     tmp = BN_CTX_get(ctx);
  54     if (tmp == NULL)
  55         goto err;
  56
  57     if (!BN_is_odd(dh->p))
  58         *ret |= DH_CHECK_P_NOT_PRIME;
  59     if (BN_is_negative(dh->g) || BN_is_zero(dh->g) || BN_is_one(dh->g))
  60         *ret |= DH_NOT_SUITABLE_GENERATOR;
  61     if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
  62         goto err;
  63     if (BN_cmp(dh->g, tmp) >= 0)
  64         *ret |= DH_NOT_SUITABLE_GENERATOR;
  65     if (BN_num_bits(dh->p) < DH_MIN_MODULUS_BITS)
  66         *ret |= DH_MODULUS_TOO_SMALL;
  67     if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS)
  68         *ret |= DH_MODULUS_TOO_LARGE;
  69
  70     ok = 1;
  71  err:
  72     BN_CTX_end(ctx);
  73     BN_CTX_free(ctx);
  74     return ok;
  75 }
  76
  77 /*-
  78  * Check that p is a safe prime and
  79  * g is a suitable generator.
  80  */
  81 int DH_check_ex(const DH *dh)
  82 {
  83     int errflags = 0;
  84
  85     if (!DH_check(dh, &errflags))
  86         return 0;
  87
  88     if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
  89         DHerr(DH_F_DH_CHECK_EX, DH_R_NOT_SUITABLE_GENERATOR);
  90     if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)
  91         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_Q_NOT_PRIME);
  92     if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)
  93         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_Q_VALUE);
  94     if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)
  95         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_J_VALUE);
  96     if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
  97         DHerr(DH_F_DH_CHECK_EX, DH_R_UNABLE_TO_CHECK_GENERATOR);
  98     if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
  99         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_PRIME);
 100     if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
 101         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_SAFE_PRIME);
 102     if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
 103         DHerr(DH_F_DH_CHECK_EX, DH_R_MODULUS_TOO_SMALL);
 104     if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
 105         DHerr(DH_F_DH_CHECK_EX, DH_R_MODULUS_TOO_LARGE);
 106
 107     return errflags == 0;
 108 }
 109
 110 int DH_check(const DH *dh, int *ret)
 111 {
 112     int ok = 0, r;
 113     BN_CTX *ctx = NULL;
 114     BIGNUM *t1 = NULL, *t2 = NULL;
 115
 116     if (!DH_check_params(dh, ret))
 117         return 0;
 118
 119     ctx = BN_CTX_new();
 120     if (ctx == NULL)
 121         goto err;
 122     BN_CTX_start(ctx);
 123     t1 = BN_CTX_get(ctx);
 124     t2 = BN_CTX_get(ctx);
 125     if (t2 == NULL)
 126         goto err;
 127
 128     if (dh->q) {
 129         if (BN_cmp(dh->g, BN_value_one()) <= 0)
 130             *ret |= DH_NOT_SUITABLE_GENERATOR;
 131         else if (BN_cmp(dh->g, dh->p) >= 0)
 132             *ret |= DH_NOT_SUITABLE_GENERATOR;
 133         else {
 134             /* Check g^q == 1 mod p */
 135             if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
 136                 goto err;
 137             if (!BN_is_one(t1))
 138                 *ret |= DH_NOT_SUITABLE_GENERATOR;
 139         }
 140         r = BN_is_prime_ex(dh->q, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
 141         if (r < 0)
 142             goto err;
 143         if (!r)
 144             *ret |= DH_CHECK_Q_NOT_PRIME;
 145         /* Check p == 1 mod q  i.e. q divides p - 1 */
 146         if (!BN_div(t1, t2, dh->p, dh->q, ctx))
 147             goto err;
 148         if (!BN_is_one(t2))
 149             *ret |= DH_CHECK_INVALID_Q_VALUE;
 150         if (dh->j && BN_cmp(dh->j, t1))
 151             *ret |= DH_CHECK_INVALID_J_VALUE;
 152     }
 153
 154     r = BN_is_prime_ex(dh->p, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
 155     if (r < 0)
 156         goto err;
 157     if (!r)
 158         *ret |= DH_CHECK_P_NOT_PRIME;
 159     else if (!dh->q) {
 160         if (!BN_rshift1(t1, dh->p))
 161             goto err;
 162         r = BN_is_prime_ex(t1, DH_NUMBER_ITERATIONS_FOR_PRIME, ctx, NULL);
 163         if (r < 0)
 164             goto err;
 165         if (!r)
 166             *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
 167     }
 168     ok = 1;
 169  err:
 170     BN_CTX_end(ctx);
 171     BN_CTX_free(ctx);
 172     return ok;
 173 }
 174
 175 int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
 176 {
 177     int errflags = 0;
 178
 179     if (!DH_check_pub_key(dh, pub_key, &errflags))
 180         return 0;
 181
 182     if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
 183         DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_SMALL);
 184     if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
 185         DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_LARGE);
 186     if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
 187         DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_INVALID);
 188
 189     return errflags == 0;
 190 }
 191
 192 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
 193 {
 194     int ok = 0;
 195     BIGNUM *tmp = NULL;
 196     BN_CTX *ctx = NULL;
 197
 198     *ret = 0;
 199     ctx = BN_CTX_new();
 200     if (ctx == NULL)
 201         goto err;
 202     BN_CTX_start(ctx);
 203     tmp = BN_CTX_get(ctx);
 204     if (tmp == NULL || !BN_set_word(tmp, 1))
 205         goto err;
 206     if (BN_cmp(pub_key, tmp) <= 0)
 207         *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
 208     if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
 209         goto err;
 210     if (BN_cmp(pub_key, tmp) >= 0)
 211         *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
 212
 213     if (dh->q != NULL) {
 214         /* Check pub_key^q == 1 mod p */
 215         if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx))
 216             goto err;
 217         if (!BN_is_one(tmp))
 218             *ret |= DH_CHECK_PUBKEY_INVALID;
 219     }
 220
 221     ok = 1;
 222  err:
 223     BN_CTX_end(ctx);
 224     BN_CTX_free(ctx);
 225     return ok;
 226 }