1 /*
2 * Copyright (c) 2022 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/ecdsa.h>
10 #include <openssl/obj_mac.h>
11
12 #include "fido.h"
13 #include "fido/es384.h"
14
15 #if OPENSSL_VERSION_NUMBER >= 0x30000000
16 #define get0_EC_KEY(x) EVP_PKEY_get0_EC_KEY((x))
17 #else
18 #define get0_EC_KEY(x) EVP_PKEY_get0((x))
19 #endif
20
21 static int
decode_coord(const cbor_item_t * item,void * xy,size_t xy_len)22 decode_coord(const cbor_item_t *item, void *xy, size_t xy_len)
23 {
24 if (cbor_isa_bytestring(item) == false ||
25 cbor_bytestring_is_definite(item) == false ||
26 cbor_bytestring_length(item) != xy_len) {
27 fido_log_debug("%s: cbor type", __func__);
28 return (-1);
29 }
30
31 memcpy(xy, cbor_bytestring_handle(item), xy_len);
32
33 return (0);
34 }
35
36 static int
decode_pubkey_point(const cbor_item_t * key,const cbor_item_t * val,void * arg)37 decode_pubkey_point(const cbor_item_t *key, const cbor_item_t *val, void *arg)
38 {
39 es384_pk_t *k = arg;
40
41 if (cbor_isa_negint(key) == false ||
42 cbor_int_get_width(key) != CBOR_INT_8)
43 return (0); /* ignore */
44
45 switch (cbor_get_uint8(key)) {
46 case 1: /* x coordinate */
47 return (decode_coord(val, &k->x, sizeof(k->x)));
48 case 2: /* y coordinate */
49 return (decode_coord(val, &k->y, sizeof(k->y)));
50 }
51
52 return (0); /* ignore */
53 }
54
55 int
es384_pk_decode(const cbor_item_t * item,es384_pk_t * k)56 es384_pk_decode(const cbor_item_t *item, es384_pk_t *k)
57 {
58 if (cbor_isa_map(item) == false ||
59 cbor_map_is_definite(item) == false ||
60 cbor_map_iter(item, k, decode_pubkey_point) < 0) {
61 fido_log_debug("%s: cbor type", __func__);
62 return (-1);
63 }
64
65 return (0);
66 }
67
68 es384_pk_t *
es384_pk_new(void)69 es384_pk_new(void)
70 {
71 return (calloc(1, sizeof(es384_pk_t)));
72 }
73
74 void
es384_pk_free(es384_pk_t ** pkp)75 es384_pk_free(es384_pk_t **pkp)
76 {
77 es384_pk_t *pk;
78
79 if (pkp == NULL || (pk = *pkp) == NULL)
80 return;
81
82 freezero(pk, sizeof(*pk));
83 *pkp = NULL;
84 }
85
86 int
es384_pk_from_ptr(es384_pk_t * pk,const void * ptr,size_t len)87 es384_pk_from_ptr(es384_pk_t *pk, const void *ptr, size_t len)
88 {
89 const uint8_t *p = ptr;
90 EVP_PKEY *pkey;
91
92 if (len < sizeof(*pk))
93 return (FIDO_ERR_INVALID_ARGUMENT);
94
95 if (len == sizeof(*pk) + 1 && *p == 0x04)
96 memcpy(pk, ++p, sizeof(*pk)); /* uncompressed format */
97 else
98 memcpy(pk, ptr, sizeof(*pk)); /* libfido2 x||y format */
99
100 if ((pkey = es384_pk_to_EVP_PKEY(pk)) == NULL) {
101 fido_log_debug("%s: es384_pk_to_EVP_PKEY", __func__);
102 explicit_bzero(pk, sizeof(*pk));
103 return (FIDO_ERR_INVALID_ARGUMENT);
104 }
105
106 EVP_PKEY_free(pkey);
107
108 return (FIDO_OK);
109 }
110
111 EVP_PKEY *
es384_pk_to_EVP_PKEY(const es384_pk_t * k)112 es384_pk_to_EVP_PKEY(const es384_pk_t *k)
113 {
114 BN_CTX *bnctx = NULL;
115 EC_KEY *ec = NULL;
116 EC_POINT *q = NULL;
117 EVP_PKEY *pkey = NULL;
118 BIGNUM *x = NULL;
119 BIGNUM *y = NULL;
120 const EC_GROUP *g = NULL;
121 int ok = -1;
122
123 if ((bnctx = BN_CTX_new()) == NULL)
124 goto fail;
125
126 BN_CTX_start(bnctx);
127
128 if ((x = BN_CTX_get(bnctx)) == NULL ||
129 (y = BN_CTX_get(bnctx)) == NULL)
130 goto fail;
131
132 if (BN_bin2bn(k->x, sizeof(k->x), x) == NULL ||
133 BN_bin2bn(k->y, sizeof(k->y), y) == NULL) {
134 fido_log_debug("%s: BN_bin2bn", __func__);
135 goto fail;
136 }
137
138 if ((ec = EC_KEY_new_by_curve_name(NID_secp384r1)) == NULL ||
139 (g = EC_KEY_get0_group(ec)) == NULL) {
140 fido_log_debug("%s: EC_KEY init", __func__);
141 goto fail;
142 }
143
144 if ((q = EC_POINT_new(g)) == NULL ||
145 EC_POINT_set_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
146 EC_KEY_set_public_key(ec, q) == 0) {
147 fido_log_debug("%s: EC_KEY_set_public_key", __func__);
148 goto fail;
149 }
150
151 if ((pkey = EVP_PKEY_new()) == NULL ||
152 EVP_PKEY_assign_EC_KEY(pkey, ec) == 0) {
153 fido_log_debug("%s: EVP_PKEY_assign_EC_KEY", __func__);
154 goto fail;
155 }
156
157 ec = NULL; /* at this point, ec belongs to evp */
158
159 ok = 0;
160 fail:
161 if (bnctx != NULL) {
162 BN_CTX_end(bnctx);
163 BN_CTX_free(bnctx);
164 }
165
166 if (ec != NULL)
167 EC_KEY_free(ec);
168 if (q != NULL)
169 EC_POINT_free(q);
170
171 if (ok < 0 && pkey != NULL) {
172 EVP_PKEY_free(pkey);
173 pkey = NULL;
174 }
175
176 return (pkey);
177 }
178
179 int
es384_pk_from_EC_KEY(es384_pk_t * pk,const EC_KEY * ec)180 es384_pk_from_EC_KEY(es384_pk_t *pk, const EC_KEY *ec)
181 {
182 BN_CTX *bnctx = NULL;
183 BIGNUM *x = NULL;
184 BIGNUM *y = NULL;
185 const EC_POINT *q = NULL;
186 EC_GROUP *g = NULL;
187 size_t dx;
188 size_t dy;
189 int ok = FIDO_ERR_INTERNAL;
190 int nx;
191 int ny;
192
193 if ((q = EC_KEY_get0_public_key(ec)) == NULL ||
194 (g = EC_GROUP_new_by_curve_name(NID_secp384r1)) == NULL ||
195 (bnctx = BN_CTX_new()) == NULL)
196 goto fail;
197
198 BN_CTX_start(bnctx);
199
200 if ((x = BN_CTX_get(bnctx)) == NULL ||
201 (y = BN_CTX_get(bnctx)) == NULL)
202 goto fail;
203
204 if (EC_POINT_is_on_curve(g, q, bnctx) != 1) {
205 fido_log_debug("%s: EC_POINT_is_on_curve", __func__);
206 ok = FIDO_ERR_INVALID_ARGUMENT;
207 goto fail;
208 }
209
210 if (EC_POINT_get_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
211 (nx = BN_num_bytes(x)) < 0 || (size_t)nx > sizeof(pk->x) ||
212 (ny = BN_num_bytes(y)) < 0 || (size_t)ny > sizeof(pk->y)) {
213 fido_log_debug("%s: EC_POINT_get_affine_coordinates_GFp",
214 __func__);
215 goto fail;
216 }
217
218 dx = sizeof(pk->x) - (size_t)nx;
219 dy = sizeof(pk->y) - (size_t)ny;
220
221 if ((nx = BN_bn2bin(x, pk->x + dx)) < 0 || (size_t)nx > sizeof(pk->x) ||
222 (ny = BN_bn2bin(y, pk->y + dy)) < 0 || (size_t)ny > sizeof(pk->y)) {
223 fido_log_debug("%s: BN_bn2bin", __func__);
224 goto fail;
225 }
226
227 ok = FIDO_OK;
228 fail:
229 EC_GROUP_free(g);
230
231 if (bnctx != NULL) {
232 BN_CTX_end(bnctx);
233 BN_CTX_free(bnctx);
234 }
235
236 return (ok);
237 }
238
239 int
es384_pk_from_EVP_PKEY(es384_pk_t * pk,const EVP_PKEY * pkey)240 es384_pk_from_EVP_PKEY(es384_pk_t *pk, const EVP_PKEY *pkey)
241 {
242 const EC_KEY *ec;
243
244 if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC ||
245 (ec = get0_EC_KEY(pkey)) == NULL)
246 return (FIDO_ERR_INVALID_ARGUMENT);
247
248 return (es384_pk_from_EC_KEY(pk, ec));
249 }
250
251 int
es384_verify_sig(const fido_blob_t * dgst,EVP_PKEY * pkey,const fido_blob_t * sig)252 es384_verify_sig(const fido_blob_t *dgst, EVP_PKEY *pkey,
253 const fido_blob_t *sig)
254 {
255 EVP_PKEY_CTX *pctx = NULL;
256 int ok = -1;
257
258 if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC) {
259 fido_log_debug("%s: EVP_PKEY_base_id", __func__);
260 goto fail;
261 }
262
263 if ((pctx = EVP_PKEY_CTX_new(pkey, NULL)) == NULL ||
264 EVP_PKEY_verify_init(pctx) != 1 ||
265 EVP_PKEY_verify(pctx, sig->ptr, sig->len, dgst->ptr,
266 dgst->len) != 1) {
267 fido_log_debug("%s: EVP_PKEY_verify", __func__);
268 goto fail;
269 }
270
271 ok = 0;
272 fail:
273 EVP_PKEY_CTX_free(pctx);
274
275 return (ok);
276 }
277
278 int
es384_pk_verify_sig(const fido_blob_t * dgst,const es384_pk_t * pk,const fido_blob_t * sig)279 es384_pk_verify_sig(const fido_blob_t *dgst, const es384_pk_t *pk,
280 const fido_blob_t *sig)
281 {
282 EVP_PKEY *pkey;
283 int ok = -1;
284
285 if ((pkey = es384_pk_to_EVP_PKEY(pk)) == NULL ||
286 es384_verify_sig(dgst, pkey, sig) < 0) {
287 fido_log_debug("%s: es384_verify_sig", __func__);
288 goto fail;
289 }
290
291 ok = 0;
292 fail:
293 EVP_PKEY_free(pkey);
294
295 return (ok);
296 }
297