| 1 | /*
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| 2 | * Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include "internal/ffc.h"
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| 11 |
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| 12 | /*
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| 13 | * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
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| 14 | * To only be used with ephemeral FFC public keys generated using the approved
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| 15 | * safe-prime groups. (Checks that the public key is in the range [2, p - 1]
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| 16 | *
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| 17 | * ret contains 0 on success, or error flags (see FFC_ERROR_PUBKEY_TOO_SMALL)
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| 18 | */
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| 19 | int ossl_ffc_validate_public_key_partial(const FFC_PARAMS *params,
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| 20 | const BIGNUM *pub_key, int *ret)
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| 21 | {
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| 22 | int ok = 0;
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| 23 | BIGNUM *tmp = NULL;
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| 24 | BN_CTX *ctx = NULL;
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| 25 |
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| 26 | *ret = 0;
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| 27 | if (params == NULL || pub_key == NULL || params->p == NULL) {
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| 28 | *ret = FFC_ERROR_PASSED_NULL_PARAM;
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| 29 | return 1;
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| 30 | }
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| 31 |
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| 32 | ctx = BN_CTX_new_ex(NULL);
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| 33 | if (ctx == NULL)
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| 34 | goto err;
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| 35 |
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| 36 | BN_CTX_start(ctx);
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| 37 | tmp = BN_CTX_get(ctx);
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| 38 | /* Step(1): Verify pub_key >= 2 */
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| 39 | if (tmp == NULL
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| 40 | || !BN_set_word(tmp, 1))
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| 41 | goto err;
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| 42 | if (BN_cmp(pub_key, tmp) <= 0)
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| 43 | *ret |= FFC_ERROR_PUBKEY_TOO_SMALL;
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| 44 | /* Step(1): Verify pub_key <= p-2 */
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| 45 | if (BN_copy(tmp, params->p) == NULL
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| 46 | || !BN_sub_word(tmp, 1))
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| 47 | goto err;
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| 48 | if (BN_cmp(pub_key, tmp) >= 0)
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| 49 | *ret |= FFC_ERROR_PUBKEY_TOO_LARGE;
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| 50 | ok = 1;
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| 51 | err:
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| 52 | if (ctx != NULL) {
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| 53 | BN_CTX_end(ctx);
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| 54 | BN_CTX_free(ctx);
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| 55 | }
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| 56 | return ok;
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| 57 | }
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| 58 |
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| 59 | /*
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| 60 | * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
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| 61 | */
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| 62 | int ossl_ffc_validate_public_key(const FFC_PARAMS *params,
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| 63 | const BIGNUM *pub_key, int *ret)
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| 64 | {
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| 65 | int ok = 0;
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| 66 | BIGNUM *tmp = NULL;
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| 67 | BN_CTX *ctx = NULL;
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| 68 |
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| 69 | if (!ossl_ffc_validate_public_key_partial(params, pub_key, ret))
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| 70 | return 0;
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| 71 |
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| 72 | if (*ret == 0 && params->q != NULL) {
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| 73 | ctx = BN_CTX_new_ex(NULL);
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| 74 | if (ctx == NULL)
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| 75 | goto err;
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| 76 | BN_CTX_start(ctx);
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| 77 | tmp = BN_CTX_get(ctx);
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| 78 |
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| 79 | /* Check pub_key^q == 1 mod p */
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| 80 | if (tmp == NULL
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| 81 | || !BN_mod_exp(tmp, pub_key, params->q, params->p, ctx))
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| 82 | goto err;
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| 83 | if (!BN_is_one(tmp))
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| 84 | *ret |= FFC_ERROR_PUBKEY_INVALID;
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| 85 | }
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| 86 |
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| 87 | ok = 1;
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| 88 | err:
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| 89 | if (ctx != NULL) {
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| 90 | BN_CTX_end(ctx);
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| 91 | BN_CTX_free(ctx);
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| 92 | }
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| 93 | return ok;
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| 94 | }
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| 95 |
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| 96 | /*
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| 97 | * See SP800-56Ar3 Section 5.6.2.1.2: Owner assurance of Private key validity.
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| 98 | * Verifies priv_key is in the range [1..upper-1]. The passed in value of upper
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| 99 | * is normally params->q but can be 2^N for approved safe prime groups.
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| 100 | * Note: This assumes that the domain parameters are valid.
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| 101 | */
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| 102 | int ossl_ffc_validate_private_key(const BIGNUM *upper, const BIGNUM *priv,
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| 103 | int *ret)
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| 104 | {
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| 105 | int ok = 0;
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| 106 |
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| 107 | *ret = 0;
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| 108 |
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| 109 | if (priv == NULL || upper == NULL) {
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| 110 | *ret = FFC_ERROR_PASSED_NULL_PARAM;
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| 111 | goto err;
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| 112 | }
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| 113 | if (BN_cmp(priv, BN_value_one()) < 0) {
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| 114 | *ret |= FFC_ERROR_PRIVKEY_TOO_SMALL;
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| 115 | goto err;
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| 116 | }
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| 117 | if (BN_cmp(priv, upper) >= 0) {
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| 118 | *ret |= FFC_ERROR_PRIVKEY_TOO_LARGE;
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| 119 | goto err;
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| 120 | }
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| 121 | ok = 1;
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| 122 | err:
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| 123 | return ok;
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| 124 | }
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