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 */
ossl_ffc_validate_public_key_partial(const FFC_PARAMS * params,const BIGNUM * pub_key,int * ret)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 */
ossl_ffc_validate_public_key(const FFC_PARAMS * params,const BIGNUM * pub_key,int * ret)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 */
ossl_ffc_validate_private_key(const BIGNUM * upper,const BIGNUM * priv,int * ret)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