crypto/ffc/ffc_key_validate.c

   1 /*
   2  * Copyright 2019-2023 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 "internal/ffc.h"
  11
  12 /*
  13  * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
  14  * To only be used with ephemeral FFC public keys generated using the approved
  15  * safe-prime groups. (Checks that the public key is in the range [2, p - 1]
  16  *
  17  * ret contains 0 on success, or error flags (see FFC_ERROR_PUBKEY_TOO_SMALL)
  18  */
  19 int ossl_ffc_validate_public_key_partial(const FFC_PARAMS *params,
  20                                          const BIGNUM *pub_key, int *ret)
  21 {
  22     int ok = 0;
  23     BIGNUM *tmp = NULL;
  24     BN_CTX *ctx = NULL;
  25
  26     *ret = 0;
  27     if (params == NULL || pub_key == NULL || params->p == NULL) {
  28         *ret = FFC_ERROR_PASSED_NULL_PARAM;
  29         return 1;
  30     }
  31
  32     ctx = BN_CTX_new_ex(NULL);
  33     if (ctx == NULL)
  34         goto err;
  35
  36     BN_CTX_start(ctx);
  37     tmp = BN_CTX_get(ctx);
  38     /* Step(1): Verify pub_key >= 2 */
  39     if (tmp == NULL
  40         || !BN_set_word(tmp, 1))
  41         goto err;
  42     if (BN_cmp(pub_key, tmp) <= 0)
  43         *ret |= FFC_ERROR_PUBKEY_TOO_SMALL;
  44     /* Step(1): Verify pub_key <=  p-2 */
  45     if (BN_copy(tmp, params->p) == NULL
  46         || !BN_sub_word(tmp, 1))
  47         goto err;
  48     if (BN_cmp(pub_key, tmp) >= 0)
  49         *ret |= FFC_ERROR_PUBKEY_TOO_LARGE;
  50     ok = 1;
  51  err:
  52     if (ctx != NULL) {
  53         BN_CTX_end(ctx);
  54         BN_CTX_free(ctx);
  55     }
  56     return ok;
  57 }
  58
  59 /*
  60  * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
  61  */
  62 int ossl_ffc_validate_public_key(const FFC_PARAMS *params,
  63                                  const BIGNUM *pub_key, int *ret)
  64 {
  65     int ok = 0;
  66     BIGNUM *tmp = NULL;
  67     BN_CTX *ctx = NULL;
  68
  69     if (!ossl_ffc_validate_public_key_partial(params, pub_key, ret))
  70         return 0;
  71
  72     if (*ret == 0 && params->q != NULL) {
  73         ctx = BN_CTX_new_ex(NULL);
  74         if (ctx == NULL)
  75             goto err;
  76         BN_CTX_start(ctx);
  77         tmp = BN_CTX_get(ctx);
  78
  79         /* Check pub_key^q == 1 mod p */
  80         if (tmp == NULL
  81             || !BN_mod_exp(tmp, pub_key, params->q, params->p, ctx))
  82             goto err;
  83         if (!BN_is_one(tmp))
  84             *ret |= FFC_ERROR_PUBKEY_INVALID;
  85     }
  86
  87     ok = 1;
  88  err:
  89     if (ctx != NULL) {
  90         BN_CTX_end(ctx);
  91         BN_CTX_free(ctx);
  92     }
  93     return ok;
  94 }
  95
  96 /*
  97  * See SP800-56Ar3 Section 5.6.2.1.2: Owner assurance of Private key validity.
  98  * Verifies priv_key is in the range [1..upper-1]. The passed in value of upper
  99  * is normally params->q but can be 2^N for approved safe prime groups.
 100  * Note: This assumes that the domain parameters are valid.
 101  */
 102 int ossl_ffc_validate_private_key(const BIGNUM *upper, const BIGNUM *priv,
 103                                   int *ret)
 104 {
 105     int ok = 0;
 106
 107     *ret = 0;
 108
 109     if (priv == NULL || upper == NULL) {
 110         *ret = FFC_ERROR_PASSED_NULL_PARAM;
 111         goto err;
 112     }
 113     if (BN_cmp(priv, BN_value_one()) < 0) {
 114         *ret |= FFC_ERROR_PRIVKEY_TOO_SMALL;
 115         goto err;
 116     }
 117     if (BN_cmp(priv, upper) >= 0) {
 118         *ret |= FFC_ERROR_PRIVKEY_TOO_LARGE;
 119         goto err;
 120     }
 121     ok = 1;
 122 err:
 123     return ok;
 124 }