crypto/dh/dh_check.c

   1 /*
   2  * Copyright 1995-2017 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_locl.h"
  14
  15 /*-
  16  * Check that p and g are suitable enough
  17  *
  18  * p is odd
  19  * 1 < g < p - 1
  20  */
  21 int DH_check_params_ex(const DH *dh)
  22 {
  23     int errflags = 0;
  24
  25     (void)DH_check_params(dh, &errflags);
  26
  27     if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
  28         DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_CHECK_P_NOT_PRIME);
  29     if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
  30         DHerr(DH_F_DH_CHECK_PARAMS_EX, DH_R_NOT_SUITABLE_GENERATOR);
  31
  32     return errflags == 0;
  33 }
  34
  35 int DH_check_params(const DH *dh, int *ret)
  36 {
  37     int ok = 0;
  38     BIGNUM *tmp = NULL;
  39     BN_CTX *ctx = NULL;
  40
  41     *ret = 0;
  42     ctx = BN_CTX_new();
  43     if (ctx == NULL)
  44         goto err;
  45     BN_CTX_start(ctx);
  46     tmp = BN_CTX_get(ctx);
  47     if (tmp == NULL)
  48         goto err;
  49
  50     if (!BN_is_odd(dh->p))
  51         *ret |= DH_CHECK_P_NOT_PRIME;
  52     if (BN_is_negative(dh->g) || BN_is_zero(dh->g) || BN_is_one(dh->g))
  53         *ret |= DH_NOT_SUITABLE_GENERATOR;
  54     if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
  55         goto err;
  56     if (BN_cmp(dh->g, tmp) >= 0)
  57         *ret |= DH_NOT_SUITABLE_GENERATOR;
  58
  59     ok = 1;
  60  err:
  61     if (ctx != NULL) {
  62         BN_CTX_end(ctx);
  63         BN_CTX_free(ctx);
  64     }
  65     return ok;
  66 }
  67
  68 /*-
  69  * Check that p is a safe prime and
  70  * if g is 2, 3 or 5, check that it is a suitable generator
  71  * where
  72  * for 2, p mod 24 == 11
  73  * for 3, p mod 12 == 5
  74  * for 5, p mod 10 == 3 or 7
  75  * should hold.
  76  */
  77 int DH_check_ex(const DH *dh)
  78 {
  79     int errflags = 0;
  80
  81     (void)DH_check(dh, &errflags);
  82
  83     if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
  84         DHerr(DH_F_DH_CHECK_EX, DH_R_NOT_SUITABLE_GENERATOR);
  85     if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)
  86         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_Q_NOT_PRIME);
  87     if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)
  88         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_Q_VALUE);
  89     if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)
  90         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_INVALID_J_VALUE);
  91     if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
  92         DHerr(DH_F_DH_CHECK_EX, DH_R_UNABLE_TO_CHECK_GENERATOR);
  93     if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
  94         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_PRIME);
  95     if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
  96         DHerr(DH_F_DH_CHECK_EX, DH_R_CHECK_P_NOT_SAFE_PRIME);
  97
  98     return errflags == 0;
  99 }
 100
 101 int DH_check(const DH *dh, int *ret)
 102 {
 103     int ok = 0, r;
 104     BN_CTX *ctx = NULL;
 105     BN_ULONG l;
 106     BIGNUM *t1 = NULL, *t2 = NULL;
 107
 108     *ret = 0;
 109     ctx = BN_CTX_new();
 110     if (ctx == NULL)
 111         goto err;
 112     BN_CTX_start(ctx);
 113     t1 = BN_CTX_get(ctx);
 114     t2 = BN_CTX_get(ctx);
 115     if (t2 == NULL)
 116         goto err;
 117
 118     if (dh->q) {
 119         if (BN_cmp(dh->g, BN_value_one()) <= 0)
 120             *ret |= DH_NOT_SUITABLE_GENERATOR;
 121         else if (BN_cmp(dh->g, dh->p) >= 0)
 122             *ret |= DH_NOT_SUITABLE_GENERATOR;
 123         else {
 124             /* Check g^q == 1 mod p */
 125             if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx))
 126                 goto err;
 127             if (!BN_is_one(t1))
 128                 *ret |= DH_NOT_SUITABLE_GENERATOR;
 129         }
 130         r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
 131         if (r < 0)
 132             goto err;
 133         if (!r)
 134             *ret |= DH_CHECK_Q_NOT_PRIME;
 135         /* Check p == 1 mod q  i.e. q divides p - 1 */
 136         if (!BN_div(t1, t2, dh->p, dh->q, ctx))
 137             goto err;
 138         if (!BN_is_one(t2))
 139             *ret |= DH_CHECK_INVALID_Q_VALUE;
 140         if (dh->j && BN_cmp(dh->j, t1))
 141             *ret |= DH_CHECK_INVALID_J_VALUE;
 142
 143     } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
 144         l = BN_mod_word(dh->p, 24);
 145         if (l == (BN_ULONG)-1)
 146             goto err;
 147         if (l != 11)
 148             *ret |= DH_NOT_SUITABLE_GENERATOR;
 149     } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
 150         l = BN_mod_word(dh->p, 10);
 151         if (l == (BN_ULONG)-1)
 152             goto err;
 153         if ((l != 3) && (l != 7))
 154             *ret |= DH_NOT_SUITABLE_GENERATOR;
 155     } else
 156         *ret |= DH_UNABLE_TO_CHECK_GENERATOR;
 157
 158     r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
 159     if (r < 0)
 160         goto err;
 161     if (!r)
 162         *ret |= DH_CHECK_P_NOT_PRIME;
 163     else if (!dh->q) {
 164         if (!BN_rshift1(t1, dh->p))
 165             goto err;
 166         r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
 167         if (r < 0)
 168             goto err;
 169         if (!r)
 170             *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
 171     }
 172     ok = 1;
 173  err:
 174     if (ctx != NULL) {
 175         BN_CTX_end(ctx);
 176         BN_CTX_free(ctx);
 177     }
 178     return ok;
 179 }
 180
 181 int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
 182 {
 183     int errflags = 0;
 184
 185     (void)DH_check(dh, &errflags);
 186
 187     if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
 188         DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_SMALL);
 189     if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
 190         DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_TOO_LARGE);
 191     if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
 192         DHerr(DH_F_DH_CHECK_PUB_KEY_EX, DH_R_CHECK_PUBKEY_INVALID);
 193
 194     return errflags == 0;
 195 }
 196
 197 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
 198 {
 199     int ok = 0;
 200     BIGNUM *tmp = NULL;
 201     BN_CTX *ctx = NULL;
 202
 203     *ret = 0;
 204     ctx = BN_CTX_new();
 205     if (ctx == NULL)
 206         goto err;
 207     BN_CTX_start(ctx);
 208     tmp = BN_CTX_get(ctx);
 209     if (tmp == NULL || !BN_set_word(tmp, 1))
 210         goto err;
 211     if (BN_cmp(pub_key, tmp) <= 0)
 212         *ret |= DH_CHECK_PUBKEY_TOO_SMALL;
 213     if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
 214         goto err;
 215     if (BN_cmp(pub_key, tmp) >= 0)
 216         *ret |= DH_CHECK_PUBKEY_TOO_LARGE;
 217
 218     if (dh->q != NULL) {
 219         /* Check pub_key^q == 1 mod p */
 220         if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx))
 221             goto err;
 222         if (!BN_is_one(tmp))
 223             *ret |= DH_CHECK_PUBKEY_INVALID;
 224     }
 225
 226     ok = 1;
 227  err:
 228     if (ctx != NULL) {
 229         BN_CTX_end(ctx);
 230         BN_CTX_free(ctx);
 231     }
 232     return ok;
 233 }