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 0; 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 goto err; 45 } 46 /* Step(1): Verify pub_key <= p-2 */ 47 if (BN_copy(tmp, params->p) == NULL 48 || !BN_sub_word(tmp, 1)) 49 goto err; 50 if (BN_cmp(pub_key, tmp) >= 0) { 51 *ret |= FFC_ERROR_PUBKEY_TOO_LARGE; 52 goto err; 53 } 54 ok = 1; 55 err: 56 if (ctx != NULL) { 57 BN_CTX_end(ctx); 58 BN_CTX_free(ctx); 59 } 60 return ok; 61 } 62 63 /* 64 * See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation. 65 */ 66 int ossl_ffc_validate_public_key(const FFC_PARAMS *params, 67 const BIGNUM *pub_key, int *ret) 68 { 69 int ok = 0; 70 BIGNUM *tmp = NULL; 71 BN_CTX *ctx = NULL; 72 73 if (!ossl_ffc_validate_public_key_partial(params, pub_key, ret)) 74 return 0; 75 76 if (params->q != NULL) { 77 ctx = BN_CTX_new_ex(NULL); 78 if (ctx == NULL) 79 goto err; 80 BN_CTX_start(ctx); 81 tmp = BN_CTX_get(ctx); 82 83 /* Check pub_key^q == 1 mod p */ 84 if (tmp == NULL 85 || !BN_mod_exp(tmp, pub_key, params->q, params->p, ctx)) 86 goto err; 87 if (!BN_is_one(tmp)) { 88 *ret |= FFC_ERROR_PUBKEY_INVALID; 89 goto err; 90 } 91 } 92 93 ok = 1; 94 err: 95 if (ctx != NULL) { 96 BN_CTX_end(ctx); 97 BN_CTX_free(ctx); 98 } 99 return ok; 100 } 101 102 /* 103 * See SP800-56Ar3 Section 5.6.2.1.2: Owner assurance of Private key validity. 104 * Verifies priv_key is in the range [1..upper-1]. The passed in value of upper 105 * is normally params->q but can be 2^N for approved safe prime groups. 106 * Note: This assumes that the domain parameters are valid. 107 */ 108 int ossl_ffc_validate_private_key(const BIGNUM *upper, const BIGNUM *priv, 109 int *ret) 110 { 111 int ok = 0; 112 113 *ret = 0; 114 115 if (priv == NULL || upper == NULL) { 116 *ret = FFC_ERROR_PASSED_NULL_PARAM; 117 goto err; 118 } 119 if (BN_cmp(priv, BN_value_one()) < 0) { 120 *ret |= FFC_ERROR_PRIVKEY_TOO_SMALL; 121 goto err; 122 } 123 if (BN_cmp(priv, upper) >= 0) { 124 *ret |= FFC_ERROR_PRIVKEY_TOO_LARGE; 125 goto err; 126 } 127 ok = 1; 128 err: 129 return ok; 130 } 131