1 /*
2 * Copyright 2019-2020 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 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 */
ossl_ffc_validate_public_key(const FFC_PARAMS * params,const BIGNUM * pub_key,int * ret)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 */
ossl_ffc_validate_private_key(const BIGNUM * upper,const BIGNUM * priv,int * ret)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