crypto/dh/dh_check.c

   1 /*
   2  * Copyright 1995-2020 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 /*
  11  * DH low level APIs are deprecated for public use, but still ok for
  12  * internal use.
  13  */
  14 #include "internal/deprecated.h"
  15
  16 #include <stdio.h>
  17 #include "internal/cryptlib.h"
  18 #include <openssl/bn.h>
  19 #include "dh_local.h"
  20 #include "crypto/dh.h"
  21
  22 /*-
  23  * Check that p and g are suitable enough
  24  *
  25  * p is odd
  26  * 1 < g < p - 1
  27  */
  28 int DH_check_params_ex(const DH *dh)
  29 {
  30     int errflags = 0;
  31
  32     if (!DH_check_params(dh, &errflags))
  33         return 0;
  34
  35     if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
  36         ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);
  37     if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
  38         ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);
  39     if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
  40         ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
  41     if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
  42         ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
  43
  44     return errflags == 0;
  45 }
  46
  47 #ifdef FIPS_MODULE
  48 int DH_check_params(const DH *dh, int *ret)
  49 {
  50     int nid;
  51
  52     *ret = 0;
  53     /*
  54      * SP800-56A R3 Section 5.5.2 Assurances of Domain Parameter Validity
  55      * (1a) The domain parameters correspond to any approved safe prime group.
  56      */
  57     nid = DH_get_nid((DH *)dh);
  58     if (nid != NID_undef)
  59         return 1;
  60     /*
  61      * OR
  62      * (2b) FFC domain params conform to FIPS-186-4 explicit domain param
  63      * validity tests.
  64      */
  65     return ossl_ffc_params_FIPS186_4_validate(dh->libctx, &dh->params,
  66                                               FFC_PARAM_TYPE_DH, ret, NULL);
  67 }
  68 #else
  69 int DH_check_params(const DH *dh, int *ret)
  70 {
  71     int ok = 0;
  72     BIGNUM *tmp = NULL;
  73     BN_CTX *ctx = NULL;
  74
  75     *ret = 0;
  76     ctx = BN_CTX_new();
  77     if (ctx == NULL)
  78         goto err;
  79     BN_CTX_start(ctx);
  80     tmp = BN_CTX_get(ctx);
  81     if (tmp == NULL)
  82         goto err;
  83
  84     if (!BN_is_odd(dh->params.p))
  85         *ret |= DH_CHECK_P_NOT_PRIME;
  86     if (BN_is_negative(dh->params.g)
  87         || BN_is_zero(dh->params.g)
  88         || BN_is_one(dh->params.g))
  89         *ret |= DH_NOT_SUITABLE_GENERATOR;
  90     if (BN_copy(tmp, dh->params.p) == NULL || !BN_sub_word(tmp, 1))
  91         goto err;
  92     if (BN_cmp(dh->params.g, tmp) >= 0)
  93         *ret |= DH_NOT_SUITABLE_GENERATOR;
  94     if (BN_num_bits(dh->params.p) < DH_MIN_MODULUS_BITS)
  95         *ret |= DH_MODULUS_TOO_SMALL;
  96     if (BN_num_bits(dh->params.p) > OPENSSL_DH_MAX_MODULUS_BITS)
  97         *ret |= DH_MODULUS_TOO_LARGE;
  98
  99     ok = 1;
 100  err:
 101     BN_CTX_end(ctx);
 102     BN_CTX_free(ctx);
 103     return ok;
 104 }
 105 #endif /* FIPS_MODULE */
 106
 107 /*-
 108  * Check that p is a safe prime and
 109  * g is a suitable generator.
 110  */
 111 int DH_check_ex(const DH *dh)
 112 {
 113     int errflags = 0;
 114
 115     if (!DH_check(dh, &errflags))
 116         return 0;
 117
 118     if ((errflags & DH_NOT_SUITABLE_GENERATOR) != 0)
 119         ERR_raise(ERR_LIB_DH, DH_R_NOT_SUITABLE_GENERATOR);
 120     if ((errflags & DH_CHECK_Q_NOT_PRIME) != 0)
 121         ERR_raise(ERR_LIB_DH, DH_R_CHECK_Q_NOT_PRIME);
 122     if ((errflags & DH_CHECK_INVALID_Q_VALUE) != 0)
 123         ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_Q_VALUE);
 124     if ((errflags & DH_CHECK_INVALID_J_VALUE) != 0)
 125         ERR_raise(ERR_LIB_DH, DH_R_CHECK_INVALID_J_VALUE);
 126     if ((errflags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
 127         ERR_raise(ERR_LIB_DH, DH_R_UNABLE_TO_CHECK_GENERATOR);
 128     if ((errflags & DH_CHECK_P_NOT_PRIME) != 0)
 129         ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_PRIME);
 130     if ((errflags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
 131         ERR_raise(ERR_LIB_DH, DH_R_CHECK_P_NOT_SAFE_PRIME);
 132     if ((errflags & DH_MODULUS_TOO_SMALL) != 0)
 133         ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_SMALL);
 134     if ((errflags & DH_MODULUS_TOO_LARGE) != 0)
 135         ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
 136
 137     return errflags == 0;
 138 }
 139
 140 /* Note: according to documentation - this only checks the params */
 141 int DH_check(const DH *dh, int *ret)
 142 {
 143 #ifdef FIPS_MODULE
 144     return DH_check_params(dh, ret);
 145 #else
 146     int ok = 0, r;
 147     BN_CTX *ctx = NULL;
 148     BIGNUM *t1 = NULL, *t2 = NULL;
 149     int nid = DH_get_nid((DH *)dh);
 150
 151     *ret = 0;
 152     if (nid != NID_undef)
 153         return 1;
 154
 155     if (!DH_check_params(dh, ret))
 156         return 0;
 157
 158     ctx = BN_CTX_new();
 159     if (ctx == NULL)
 160         goto err;
 161     BN_CTX_start(ctx);
 162     t1 = BN_CTX_get(ctx);
 163     t2 = BN_CTX_get(ctx);
 164     if (t2 == NULL)
 165         goto err;
 166
 167     if (dh->params.q != NULL) {
 168         if (BN_cmp(dh->params.g, BN_value_one()) <= 0)
 169             *ret |= DH_NOT_SUITABLE_GENERATOR;
 170         else if (BN_cmp(dh->params.g, dh->params.p) >= 0)
 171             *ret |= DH_NOT_SUITABLE_GENERATOR;
 172         else {
 173             /* Check g^q == 1 mod p */
 174             if (!BN_mod_exp(t1, dh->params.g, dh->params.q, dh->params.p, ctx))
 175                 goto err;
 176             if (!BN_is_one(t1))
 177                 *ret |= DH_NOT_SUITABLE_GENERATOR;
 178         }
 179         r = BN_check_prime(dh->params.q, ctx, NULL);
 180         if (r < 0)
 181             goto err;
 182         if (!r)
 183             *ret |= DH_CHECK_Q_NOT_PRIME;
 184         /* Check p == 1 mod q  i.e. q divides p - 1 */
 185         if (!BN_div(t1, t2, dh->params.p, dh->params.q, ctx))
 186             goto err;
 187         if (!BN_is_one(t2))
 188             *ret |= DH_CHECK_INVALID_Q_VALUE;
 189         if (dh->params.j != NULL
 190             && BN_cmp(dh->params.j, t1))
 191             *ret |= DH_CHECK_INVALID_J_VALUE;
 192     }
 193
 194     r = BN_check_prime(dh->params.p, ctx, NULL);
 195     if (r < 0)
 196         goto err;
 197     if (!r)
 198         *ret |= DH_CHECK_P_NOT_PRIME;
 199     else if (dh->params.q == NULL) {
 200         if (!BN_rshift1(t1, dh->params.p))
 201             goto err;
 202         r = BN_check_prime(t1, ctx, NULL);
 203         if (r < 0)
 204             goto err;
 205         if (!r)
 206             *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
 207     }
 208     ok = 1;
 209  err:
 210     BN_CTX_end(ctx);
 211     BN_CTX_free(ctx);
 212     return ok;
 213 #endif /* FIPS_MODULE */
 214 }
 215
 216 int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
 217 {
 218     int errflags = 0;
 219
 220     if (!DH_check_pub_key(dh, pub_key, &errflags))
 221         return 0;
 222
 223     if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
 224         ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_SMALL);
 225     if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
 226         ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_LARGE);
 227     if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
 228         ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_INVALID);
 229
 230     return errflags == 0;
 231 }
 232
 233 /*
 234  * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
 235  */
 236 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
 237 {
 238     return ossl_ffc_validate_public_key(&dh->params, pub_key, ret);
 239 }
 240
 241 /*
 242  * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
 243  * To only be used with ephemeral FFC public keys generated using the approved
 244  * safe-prime groups.
 245  */
 246 int dh_check_pub_key_partial(const DH *dh, const BIGNUM *pub_key, int *ret)
 247 {
 248     return ossl_ffc_validate_public_key_partial(&dh->params, pub_key, ret);
 249 }
 250
 251 int dh_check_priv_key(const DH *dh, const BIGNUM *priv_key, int *ret)
 252 {
 253     int ok = 0;
 254     BIGNUM *two_powN = NULL, *upper;
 255
 256     *ret = 0;
 257     two_powN = BN_new();
 258     if (two_powN == NULL)
 259         return 0;
 260     if (dh->params.q == NULL)
 261         goto err;
 262     upper = dh->params.q;
 263
 264     /* Is it from an approved Safe prime group ?*/
 265     if (DH_get_nid((DH *)dh) != NID_undef) {
 266         if (!BN_lshift(two_powN, BN_value_one(), dh->length))
 267             goto err;
 268         if (BN_cmp(two_powN, dh->params.q) < 0)
 269             upper = two_powN;
 270     }
 271     if (!ossl_ffc_validate_private_key(upper, priv_key, ret))
 272         goto err;
 273
 274     ok = 1;
 275 err:
 276     BN_free(two_powN);
 277     return ok;
 278 }
 279
 280 /*
 281  * FFC pairwise check from SP800-56A R3.
 282  *    Section 5.6.2.1.4 Owner Assurance of Pair-wise Consistency
 283  */
 284 int dh_check_pairwise(const DH *dh)
 285 {
 286     int ret = 0;
 287     BN_CTX *ctx = NULL;
 288     BIGNUM *pub_key = NULL;
 289
 290     if (dh->params.p == NULL
 291         || dh->params.g == NULL
 292         || dh->priv_key == NULL
 293         || dh->pub_key == NULL)
 294         return 0;
 295
 296     ctx = BN_CTX_new_ex(dh->libctx);
 297     if (ctx == NULL)
 298         goto err;
 299     pub_key = BN_new();
 300     if (pub_key == NULL)
 301         goto err;
 302
 303     /* recalculate the public key = (g ^ priv) mod p */
 304     if (!dh_generate_public_key(ctx, dh, dh->priv_key, pub_key))
 305         goto err;
 306     /* check it matches the existing pubic_key */
 307     ret = BN_cmp(pub_key, dh->pub_key) == 0;
 308 err:
 309     BN_free(pub_key);
 310     BN_CTX_free(ctx);
 311     return ret;
 312 }