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 } 125