1/*
2 * Copyright (c) 2019-2021 Yubico AB. All rights reserved.
3 * Use of this source code is governed by a BSD-style
4 * license that can be found in the LICENSE file.
5 * SPDX-License-Identifier: BSD-2-Clause
6 */
7
8#include <openssl/bn.h>
9#include <openssl/obj_mac.h>
10
11#include "fido.h"
12#include "fido/eddsa.h"
13
14#if defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x3070000f
15EVP_PKEY *
16EVP_PKEY_new_raw_public_key(int type, ENGINE *e, const unsigned char *key,
17    size_t keylen)
18{
19	(void)type;
20	(void)e;
21	(void)key;
22	(void)keylen;
23
24	fido_log_debug("%s: unimplemented", __func__);
25
26	return (NULL);
27}
28
29int
30EVP_PKEY_get_raw_public_key(const EVP_PKEY *pkey, unsigned char *pub,
31    size_t *len)
32{
33	(void)pkey;
34	(void)pub;
35	(void)len;
36
37	fido_log_debug("%s: unimplemented", __func__);
38
39	return (0);
40}
41#endif /* LIBRESSL_VERSION_NUMBER */
42
43#if defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x3040000f
44int
45EVP_DigestVerify(EVP_MD_CTX *ctx, const unsigned char *sigret, size_t siglen,
46    const unsigned char *tbs, size_t tbslen)
47{
48	(void)ctx;
49	(void)sigret;
50	(void)siglen;
51	(void)tbs;
52	(void)tbslen;
53
54	fido_log_debug("%s: unimplemented", __func__);
55
56	return (0);
57}
58#endif /* LIBRESSL_VERSION_NUMBER < 0x3040000f */
59
60static int
61decode_coord(const cbor_item_t *item, void *xy, size_t xy_len)
62{
63	if (cbor_isa_bytestring(item) == false ||
64	    cbor_bytestring_is_definite(item) == false ||
65	    cbor_bytestring_length(item) != xy_len) {
66		fido_log_debug("%s: cbor type", __func__);
67		return (-1);
68	}
69
70	memcpy(xy, cbor_bytestring_handle(item), xy_len);
71
72	return (0);
73}
74
75static int
76decode_pubkey_point(const cbor_item_t *key, const cbor_item_t *val, void *arg)
77{
78	eddsa_pk_t *k = arg;
79
80	if (cbor_isa_negint(key) == false ||
81	    cbor_int_get_width(key) != CBOR_INT_8)
82		return (0); /* ignore */
83
84	switch (cbor_get_uint8(key)) {
85	case 1: /* x coordinate */
86		return (decode_coord(val, &k->x, sizeof(k->x)));
87	}
88
89	return (0); /* ignore */
90}
91
92int
93eddsa_pk_decode(const cbor_item_t *item, eddsa_pk_t *k)
94{
95	if (cbor_isa_map(item) == false ||
96	    cbor_map_is_definite(item) == false ||
97	    cbor_map_iter(item, k, decode_pubkey_point) < 0) {
98		fido_log_debug("%s: cbor type", __func__);
99		return (-1);
100	}
101
102	return (0);
103}
104
105eddsa_pk_t *
106eddsa_pk_new(void)
107{
108	return (calloc(1, sizeof(eddsa_pk_t)));
109}
110
111void
112eddsa_pk_free(eddsa_pk_t **pkp)
113{
114	eddsa_pk_t *pk;
115
116	if (pkp == NULL || (pk = *pkp) == NULL)
117		return;
118
119	freezero(pk, sizeof(*pk));
120	*pkp = NULL;
121}
122
123int
124eddsa_pk_from_ptr(eddsa_pk_t *pk, const void *ptr, size_t len)
125{
126	EVP_PKEY *pkey;
127
128	if (len < sizeof(*pk))
129		return (FIDO_ERR_INVALID_ARGUMENT);
130
131	memcpy(pk, ptr, sizeof(*pk));
132
133	if ((pkey = eddsa_pk_to_EVP_PKEY(pk)) == NULL) {
134		fido_log_debug("%s: eddsa_pk_to_EVP_PKEY", __func__);
135		return (FIDO_ERR_INVALID_ARGUMENT);
136	}
137
138	EVP_PKEY_free(pkey);
139
140	return (FIDO_OK);
141}
142
143EVP_PKEY *
144eddsa_pk_to_EVP_PKEY(const eddsa_pk_t *k)
145{
146	EVP_PKEY *pkey = NULL;
147
148	if ((pkey = EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, NULL, k->x,
149	    sizeof(k->x))) == NULL)
150		fido_log_debug("%s: EVP_PKEY_new_raw_public_key", __func__);
151
152	return (pkey);
153}
154
155int
156eddsa_pk_from_EVP_PKEY(eddsa_pk_t *pk, const EVP_PKEY *pkey)
157{
158	size_t len = 0;
159
160	if (EVP_PKEY_base_id(pkey) != EVP_PKEY_ED25519)
161		return (FIDO_ERR_INVALID_ARGUMENT);
162	if (EVP_PKEY_get_raw_public_key(pkey, NULL, &len) != 1 ||
163	    len != sizeof(pk->x))
164		return (FIDO_ERR_INTERNAL);
165	if (EVP_PKEY_get_raw_public_key(pkey, pk->x, &len) != 1 ||
166	    len != sizeof(pk->x))
167		return (FIDO_ERR_INTERNAL);
168
169	return (FIDO_OK);
170}
171
172int
173eddsa_verify_sig(const fido_blob_t *dgst, EVP_PKEY *pkey,
174    const fido_blob_t *sig)
175{
176	EVP_MD_CTX	*mdctx = NULL;
177	int		 ok = -1;
178
179	if (EVP_PKEY_base_id(pkey) != EVP_PKEY_ED25519) {
180		fido_log_debug("%s: EVP_PKEY_base_id", __func__);
181		goto fail;
182	}
183
184	/* EVP_DigestVerify needs ints */
185	if (dgst->len > INT_MAX || sig->len > INT_MAX) {
186		fido_log_debug("%s: dgst->len=%zu, sig->len=%zu", __func__,
187		    dgst->len, sig->len);
188		return (-1);
189	}
190
191	if ((mdctx = EVP_MD_CTX_new()) == NULL) {
192		fido_log_debug("%s: EVP_MD_CTX_new", __func__);
193		goto fail;
194	}
195
196	if (EVP_DigestVerifyInit(mdctx, NULL, NULL, NULL, pkey) != 1) {
197		fido_log_debug("%s: EVP_DigestVerifyInit", __func__);
198		goto fail;
199	}
200
201	if (EVP_DigestVerify(mdctx, sig->ptr, sig->len, dgst->ptr,
202	    dgst->len) != 1) {
203		fido_log_debug("%s: EVP_DigestVerify", __func__);
204		goto fail;
205	}
206
207	ok = 0;
208fail:
209	EVP_MD_CTX_free(mdctx);
210
211	return (ok);
212}
213
214int
215eddsa_pk_verify_sig(const fido_blob_t *dgst, const eddsa_pk_t *pk,
216    const fido_blob_t *sig)
217{
218	EVP_PKEY	*pkey;
219	int		 ok = -1;
220
221	if ((pkey = eddsa_pk_to_EVP_PKEY(pk)) == NULL ||
222	    eddsa_verify_sig(dgst, pkey, sig) < 0) {
223		fido_log_debug("%s: eddsa_verify_sig", __func__);
224		goto fail;
225	}
226
227	ok = 0;
228fail:
229	EVP_PKEY_free(pkey);
230
231	return (ok);
232}
233