crypto/dh/dh_check.c

   1 /*
   2  * Copyright 1995-2024 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_ex(dh->libctx);
  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, q_good = 0;
 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     /* Don't do any checks at all with an excessively large modulus */
 156     if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
 157         ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
 158         *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_P_NOT_PRIME;
 159         return 0;
 160     }
 161
 162     if (!DH_check_params(dh, ret))
 163         return 0;
 164
 165     ctx = BN_CTX_new_ex(dh->libctx);
 166     if (ctx == NULL)
 167         goto err;
 168     BN_CTX_start(ctx);
 169     t1 = BN_CTX_get(ctx);
 170     t2 = BN_CTX_get(ctx);
 171     if (t2 == NULL)
 172         goto err;
 173
 174     if (dh->params.q != NULL) {
 175         if (BN_ucmp(dh->params.p, dh->params.q) > 0)
 176             q_good = 1;
 177         else
 178             *ret |= DH_CHECK_INVALID_Q_VALUE;
 179     }
 180
 181     if (q_good) {
 182         if (BN_cmp(dh->params.g, BN_value_one()) <= 0)
 183             *ret |= DH_NOT_SUITABLE_GENERATOR;
 184         else if (BN_cmp(dh->params.g, dh->params.p) >= 0)
 185             *ret |= DH_NOT_SUITABLE_GENERATOR;
 186         else {
 187             /* Check g^q == 1 mod p */
 188             if (!BN_mod_exp(t1, dh->params.g, dh->params.q, dh->params.p, ctx))
 189                 goto err;
 190             if (!BN_is_one(t1))
 191                 *ret |= DH_NOT_SUITABLE_GENERATOR;
 192         }
 193         r = BN_check_prime(dh->params.q, ctx, NULL);
 194         if (r < 0)
 195             goto err;
 196         if (!r)
 197             *ret |= DH_CHECK_Q_NOT_PRIME;
 198         /* Check p == 1 mod q  i.e. q divides p - 1 */
 199         if (!BN_div(t1, t2, dh->params.p, dh->params.q, ctx))
 200             goto err;
 201         if (!BN_is_one(t2))
 202             *ret |= DH_CHECK_INVALID_Q_VALUE;
 203         if (dh->params.j != NULL
 204             && BN_cmp(dh->params.j, t1))
 205             *ret |= DH_CHECK_INVALID_J_VALUE;
 206     }
 207
 208     r = BN_check_prime(dh->params.p, ctx, NULL);
 209     if (r < 0)
 210         goto err;
 211     if (!r)
 212         *ret |= DH_CHECK_P_NOT_PRIME;
 213     else if (dh->params.q == NULL) {
 214         if (!BN_rshift1(t1, dh->params.p))
 215             goto err;
 216         r = BN_check_prime(t1, ctx, NULL);
 217         if (r < 0)
 218             goto err;
 219         if (!r)
 220             *ret |= DH_CHECK_P_NOT_SAFE_PRIME;
 221     }
 222     ok = 1;
 223  err:
 224     BN_CTX_end(ctx);
 225     BN_CTX_free(ctx);
 226     return ok;
 227 #endif /* FIPS_MODULE */
 228 }
 229
 230 int DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
 231 {
 232     int errflags = 0;
 233
 234     if (!DH_check_pub_key(dh, pub_key, &errflags))
 235         return 0;
 236
 237     if ((errflags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
 238         ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_SMALL);
 239     if ((errflags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
 240         ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_TOO_LARGE);
 241     if ((errflags & DH_CHECK_PUBKEY_INVALID) != 0)
 242         ERR_raise(ERR_LIB_DH, DH_R_CHECK_PUBKEY_INVALID);
 243
 244     return errflags == 0;
 245 }
 246
 247 /*
 248  * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
 249  */
 250 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
 251 {
 252     /* Don't do any checks at all with an excessively large modulus */
 253     if (BN_num_bits(dh->params.p) > OPENSSL_DH_CHECK_MAX_MODULUS_BITS) {
 254         ERR_raise(ERR_LIB_DH, DH_R_MODULUS_TOO_LARGE);
 255         *ret = DH_MODULUS_TOO_LARGE | DH_CHECK_PUBKEY_INVALID;
 256         return 0;
 257     }
 258
 259     if (dh->params.q != NULL && BN_ucmp(dh->params.p, dh->params.q) < 0) {
 260         *ret |= DH_CHECK_INVALID_Q_VALUE | DH_CHECK_PUBKEY_INVALID;
 261         return 1;
 262     }
 263
 264     return ossl_ffc_validate_public_key(&dh->params, pub_key, ret);
 265 }
 266
 267 /*
 268  * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
 269  * To only be used with ephemeral FFC public keys generated using the approved
 270  * safe-prime groups.
 271  */
 272 int ossl_dh_check_pub_key_partial(const DH *dh, const BIGNUM *pub_key, int *ret)
 273 {
 274     return ossl_ffc_validate_public_key_partial(&dh->params, pub_key, ret)
 275            && *ret == 0;
 276 }
 277
 278 int ossl_dh_check_priv_key(const DH *dh, const BIGNUM *priv_key, int *ret)
 279 {
 280     int ok = 0;
 281     BIGNUM *two_powN = NULL, *upper;
 282
 283     *ret = 0;
 284     two_powN = BN_new();
 285     if (two_powN == NULL)
 286         return 0;
 287
 288     if (dh->params.q != NULL) {
 289         upper = dh->params.q;
 290 #ifndef FIPS_MODULE
 291     } else if (dh->params.p != NULL) {
 292         /*
 293          * We do not have q so we just check the key is within some
 294          * reasonable range, or the number of bits is equal to dh->length.
 295          */
 296         int length = dh->length;
 297
 298         if (length == 0) {
 299             length = BN_num_bits(dh->params.p) - 1;
 300             if (BN_num_bits(priv_key) <= length
 301                 && BN_num_bits(priv_key) > 1)
 302                 ok = 1;
 303         } else if (BN_num_bits(priv_key) == length) {
 304             ok = 1;
 305         }
 306         goto end;
 307 #endif
 308     } else {
 309         goto end;
 310     }
 311
 312     /* Is it from an approved Safe prime group ?*/
 313     if (DH_get_nid((DH *)dh) != NID_undef && dh->length != 0) {
 314         if (!BN_lshift(two_powN, BN_value_one(), dh->length))
 315             goto end;
 316         if (BN_cmp(two_powN, dh->params.q) < 0)
 317             upper = two_powN;
 318     }
 319     if (!ossl_ffc_validate_private_key(upper, priv_key, ret))
 320         goto end;
 321
 322     ok = 1;
 323 end:
 324     BN_free(two_powN);
 325     return ok;
 326 }
 327
 328 /*
 329  * FFC pairwise check from SP800-56A R3.
 330  *    Section 5.6.2.1.4 Owner Assurance of Pair-wise Consistency
 331  */
 332 int ossl_dh_check_pairwise(const DH *dh)
 333 {
 334     int ret = 0;
 335     BN_CTX *ctx = NULL;
 336     BIGNUM *pub_key = NULL;
 337
 338     if (dh->params.p == NULL
 339         || dh->params.g == NULL
 340         || dh->priv_key == NULL
 341         || dh->pub_key == NULL)
 342         return 0;
 343
 344     ctx = BN_CTX_new_ex(dh->libctx);
 345     if (ctx == NULL)
 346         goto err;
 347     pub_key = BN_new();
 348     if (pub_key == NULL)
 349         goto err;
 350
 351     /* recalculate the public key = (g ^ priv) mod p */
 352     if (!ossl_dh_generate_public_key(ctx, dh, dh->priv_key, pub_key))
 353         goto err;
 354     /* check it matches the existing public_key */
 355     ret = BN_cmp(pub_key, dh->pub_key) == 0;
 356 err:
 357     BN_free(pub_key);
 358     BN_CTX_free(ctx);
 359     return ret;
 360 }