Coverage Report

Created: 2023-09-23 17:42

/libfido2/src/es256.c
Line
Count
Source (jump to first uncovered line)
1
/*
2
 * Copyright (c) 2018-2022 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/es256.h"
14
15
#if OPENSSL_VERSION_NUMBER >= 0x30000000
16
30
#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 const int es256_nid = NID_X9_62_prime256v1;
22
23
static int
24
decode_coord(const cbor_item_t *item, void *xy, size_t xy_len)
25
9.66k
{
26
9.66k
        if (cbor_isa_bytestring(item) == false ||
27
9.66k
            cbor_bytestring_is_definite(item) == false ||
28
9.66k
            cbor_bytestring_length(item) != xy_len) {
29
101
                fido_log_debug("%s: cbor type", __func__);
30
101
                return (-1);
31
101
        }
32
33
9.56k
        memcpy(xy, cbor_bytestring_handle(item), xy_len);
34
35
9.56k
        return (0);
36
9.66k
}
37
38
static int
39
decode_pubkey_point(const cbor_item_t *key, const cbor_item_t *val, void *arg)
40
24.8k
{
41
24.8k
        es256_pk_t *k = arg;
42
43
24.8k
        if (cbor_isa_negint(key) == false ||
44
24.8k
            cbor_int_get_width(key) != CBOR_INT_8)
45
12.5k
                return (0); /* ignore */
46
47
12.3k
        switch (cbor_get_uint8(key)) {
48
4.93k
        case 1: /* x coordinate */
49
4.93k
                return (decode_coord(val, &k->x, sizeof(k->x)));
50
4.73k
        case 2: /* y coordinate */
51
4.73k
                return (decode_coord(val, &k->y, sizeof(k->y)));
52
12.3k
        }
53
54
2.64k
        return (0); /* ignore */
55
12.3k
}
56
57
int
58
es256_pk_decode(const cbor_item_t *item, es256_pk_t *k)
59
5.04k
{
60
5.04k
        if (cbor_isa_map(item) == false ||
61
5.04k
            cbor_map_is_definite(item) == false ||
62
5.04k
            cbor_map_iter(item, k, decode_pubkey_point) < 0) {
63
173
                fido_log_debug("%s: cbor type", __func__);
64
173
                return (-1);
65
173
        }
66
67
4.86k
        return (0);
68
5.04k
}
69
70
cbor_item_t *
71
es256_pk_encode(const es256_pk_t *pk, int ecdh)
72
3.08k
{
73
3.08k
        cbor_item_t             *item = NULL;
74
3.08k
        struct cbor_pair         argv[5];
75
3.08k
        int                      alg;
76
3.08k
        int                      ok = -1;
77
78
3.08k
        memset(argv, 0, sizeof(argv));
79
80
3.08k
        if ((item = cbor_new_definite_map(5)) == NULL)
81
13
                goto fail;
82
83
        /* kty */
84
3.07k
        if ((argv[0].key = cbor_build_uint8(1)) == NULL ||
85
3.07k
            (argv[0].value = cbor_build_uint8(2)) == NULL ||
86
3.07k
            !cbor_map_add(item, argv[0]))
87
42
                goto fail;
88
89
        /*
90
         * "The COSEAlgorithmIdentifier used is -25 (ECDH-ES +
91
         * HKDF-256) although this is NOT the algorithm actually
92
         * used. Setting this to a different value may result in
93
         * compatibility issues."
94
         */
95
3.03k
        if (ecdh)
96
2.97k
                alg = COSE_ECDH_ES256;
97
61
        else
98
61
                alg = COSE_ES256;
99
100
        /* alg */
101
3.03k
        if ((argv[1].key = cbor_build_uint8(3)) == NULL ||
102
3.03k
            (argv[1].value = cbor_build_negint8((uint8_t)(-alg - 1))) == NULL ||
103
3.03k
            !cbor_map_add(item, argv[1]))
104
44
                goto fail;
105
106
        /* crv */
107
2.98k
        if ((argv[2].key = cbor_build_negint8(0)) == NULL ||
108
2.98k
            (argv[2].value = cbor_build_uint8(1)) == NULL ||
109
2.98k
            !cbor_map_add(item, argv[2]))
110
51
                goto fail;
111
112
        /* x */
113
2.93k
        if ((argv[3].key = cbor_build_negint8(1)) == NULL ||
114
2.93k
            (argv[3].value = cbor_build_bytestring(pk->x,
115
2.92k
            sizeof(pk->x))) == NULL || !cbor_map_add(item, argv[3]))
116
46
                goto fail;
117
118
        /* y */
119
2.89k
        if ((argv[4].key = cbor_build_negint8(2)) == NULL ||
120
2.89k
            (argv[4].value = cbor_build_bytestring(pk->y,
121
2.88k
            sizeof(pk->y))) == NULL || !cbor_map_add(item, argv[4]))
122
45
                goto fail;
123
124
2.84k
        ok = 0;
125
3.08k
fail:
126
3.08k
        if (ok < 0) {
127
241
                if (item != NULL) {
128
228
                        cbor_decref(&item);
129
228
                        item = NULL;
130
228
                }
131
241
        }
132
133
18.5k
        for (size_t i = 0; i < 5; i++) {
134
15.4k
                if (argv[i].key)
135
14.8k
                        cbor_decref(&argv[i].key);
136
15.4k
                if (argv[i].value)
137
14.7k
                        cbor_decref(&argv[i].value);
138
15.4k
        }
139
140
3.08k
        return (item);
141
2.84k
}
142
143
es256_sk_t *
144
es256_sk_new(void)
145
7.21k
{
146
7.21k
        return (calloc(1, sizeof(es256_sk_t)));
147
7.21k
}
148
149
void
150
es256_sk_free(es256_sk_t **skp)
151
7.21k
{
152
7.21k
        es256_sk_t *sk;
153
154
7.21k
        if (skp == NULL || (sk = *skp) == NULL)
155
31
                return;
156
157
7.18k
        freezero(sk, sizeof(*sk));
158
7.18k
        *skp = NULL;
159
7.18k
}
160
161
es256_pk_t *
162
es256_pk_new(void)
163
14.2k
{
164
14.2k
        return (calloc(1, sizeof(es256_pk_t)));
165
14.2k
}
166
167
void
168
es256_pk_free(es256_pk_t **pkp)
169
28.8k
{
170
28.8k
        es256_pk_t *pk;
171
172
28.8k
        if (pkp == NULL || (pk = *pkp) == NULL)
173
14.6k
                return;
174
175
14.1k
        freezero(pk, sizeof(*pk));
176
14.1k
        *pkp = NULL;
177
14.1k
}
178
179
int
180
es256_pk_from_ptr(es256_pk_t *pk, const void *ptr, size_t len)
181
521
{
182
521
        const uint8_t   *p = ptr;
183
521
        EVP_PKEY        *pkey;
184
185
521
        if (len < sizeof(*pk))
186
416
                return (FIDO_ERR_INVALID_ARGUMENT);
187
188
105
        if (len == sizeof(*pk) + 1 && *p == 0x04)
189
2
                memcpy(pk, ++p, sizeof(*pk)); /* uncompressed format */
190
103
        else
191
103
                memcpy(pk, ptr, sizeof(*pk)); /* libfido2 x||y format */
192
193
105
        if ((pkey = es256_pk_to_EVP_PKEY(pk)) == NULL) {
194
73
                fido_log_debug("%s: es256_pk_to_EVP_PKEY", __func__);
195
73
                explicit_bzero(pk, sizeof(*pk));
196
73
                return (FIDO_ERR_INVALID_ARGUMENT);
197
73
        }
198
199
32
        EVP_PKEY_free(pkey);
200
201
32
        return (FIDO_OK);
202
105
}
203
204
int
205
es256_pk_set_x(es256_pk_t *pk, const unsigned char *x)
206
61
{
207
61
        memcpy(pk->x, x, sizeof(pk->x));
208
209
61
        return (0);
210
61
}
211
212
int
213
es256_pk_set_y(es256_pk_t *pk, const unsigned char *y)
214
61
{
215
61
        memcpy(pk->y, y, sizeof(pk->y));
216
217
61
        return (0);
218
61
}
219
220
int
221
es256_sk_create(es256_sk_t *key)
222
7.15k
{
223
7.15k
        EVP_PKEY_CTX    *pctx = NULL;
224
7.15k
        EVP_PKEY_CTX    *kctx = NULL;
225
7.15k
        EVP_PKEY        *p = NULL;
226
7.15k
        EVP_PKEY        *k = NULL;
227
7.15k
        const EC_KEY    *ec;
228
7.15k
        const BIGNUM    *d;
229
7.15k
        int              n;
230
7.15k
        int              ok = -1;
231
232
7.15k
        if ((pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL)) == NULL ||
233
7.15k
            EVP_PKEY_paramgen_init(pctx) <= 0 ||
234
7.15k
            EVP_PKEY_CTX_set_ec_paramgen_curve_nid(pctx, es256_nid) <= 0 ||
235
7.15k
            EVP_PKEY_paramgen(pctx, &p) <= 0) {
236
102
                fido_log_debug("%s: EVP_PKEY_paramgen", __func__);
237
102
                goto fail;
238
102
        }
239
240
7.05k
        if ((kctx = EVP_PKEY_CTX_new(p, NULL)) == NULL ||
241
7.05k
            EVP_PKEY_keygen_init(kctx) <= 0 || EVP_PKEY_keygen(kctx, &k) <= 0) {
242
101
                fido_log_debug("%s: EVP_PKEY_keygen", __func__);
243
101
                goto fail;
244
101
        }
245
246
6.95k
        if ((ec = EVP_PKEY_get0_EC_KEY(k)) == NULL ||
247
6.95k
            (d = EC_KEY_get0_private_key(ec)) == NULL ||
248
6.95k
            (n = BN_num_bytes(d)) < 0 || (size_t)n > sizeof(key->d) ||
249
6.95k
            (n = BN_bn2bin(d, key->d)) < 0 || (size_t)n > sizeof(key->d)) {
250
118
                fido_log_debug("%s: EC_KEY_get0_private_key", __func__);
251
118
                goto fail;
252
118
        }
253
254
6.83k
        ok = 0;
255
7.15k
fail:
256
7.15k
        if (p != NULL)
257
7.05k
                EVP_PKEY_free(p);
258
7.15k
        if (k != NULL)
259
6.95k
                EVP_PKEY_free(k);
260
7.15k
        if (pctx != NULL)
261
7.11k
                EVP_PKEY_CTX_free(pctx);
262
7.15k
        if (kctx != NULL)
263
7.01k
                EVP_PKEY_CTX_free(kctx);
264
265
7.15k
        return (ok);
266
6.83k
}
267
268
EVP_PKEY *
269
es256_pk_to_EVP_PKEY(const es256_pk_t *k)
270
4.60k
{
271
4.60k
        BN_CTX          *bnctx = NULL;
272
4.60k
        EC_KEY          *ec = NULL;
273
4.60k
        EC_POINT        *q = NULL;
274
4.60k
        EVP_PKEY        *pkey = NULL;
275
4.60k
        BIGNUM          *x = NULL;
276
4.60k
        BIGNUM          *y = NULL;
277
4.60k
        const EC_GROUP  *g = NULL;
278
4.60k
        int              ok = -1;
279
280
4.60k
        if ((bnctx = BN_CTX_new()) == NULL)
281
23
                goto fail;
282
283
4.58k
        BN_CTX_start(bnctx);
284
285
4.58k
        if ((x = BN_CTX_get(bnctx)) == NULL ||
286
4.58k
            (y = BN_CTX_get(bnctx)) == NULL)
287
46
                goto fail;
288
289
4.53k
        if (BN_bin2bn(k->x, sizeof(k->x), x) == NULL ||
290
4.53k
            BN_bin2bn(k->y, sizeof(k->y), y) == NULL) {
291
64
                fido_log_debug("%s: BN_bin2bn", __func__);
292
64
                goto fail;
293
64
        }
294
295
4.47k
        if ((ec = EC_KEY_new_by_curve_name(es256_nid)) == NULL ||
296
4.47k
            (g = EC_KEY_get0_group(ec)) == NULL) {
297
43
                fido_log_debug("%s: EC_KEY init", __func__);
298
43
                goto fail;
299
43
        }
300
301
4.42k
        if ((q = EC_POINT_new(g)) == NULL ||
302
4.42k
            EC_POINT_set_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
303
4.42k
            EC_KEY_set_public_key(ec, q) == 0) {
304
660
                fido_log_debug("%s: EC_KEY_set_public_key", __func__);
305
660
                goto fail;
306
660
        }
307
308
3.76k
        if ((pkey = EVP_PKEY_new()) == NULL ||
309
3.76k
            EVP_PKEY_assign_EC_KEY(pkey, ec) == 0) {
310
37
                fido_log_debug("%s: EVP_PKEY_assign_EC_KEY", __func__);
311
37
                goto fail;
312
37
        }
313
314
3.73k
        ec = NULL; /* at this point, ec belongs to evp */
315
316
3.73k
        ok = 0;
317
4.60k
fail:
318
4.60k
        if (bnctx != NULL) {
319
4.58k
                BN_CTX_end(bnctx);
320
4.58k
                BN_CTX_free(bnctx);
321
4.58k
        }
322
323
4.60k
        if (ec != NULL)
324
714
                EC_KEY_free(ec);
325
4.60k
        if (q != NULL)
326
4.40k
                EC_POINT_free(q);
327
328
4.60k
        if (ok < 0 && pkey != NULL) {
329
25
                EVP_PKEY_free(pkey);
330
25
                pkey = NULL;
331
25
        }
332
333
4.60k
        return (pkey);
334
3.73k
}
335
336
int
337
es256_pk_from_EC_KEY(es256_pk_t *pk, const EC_KEY *ec)
338
6.70k
{
339
6.70k
        BN_CTX          *bnctx = NULL;
340
6.70k
        BIGNUM          *x = NULL;
341
6.70k
        BIGNUM          *y = NULL;
342
6.70k
        const EC_POINT  *q = NULL;
343
6.70k
        EC_GROUP        *g = NULL;
344
6.70k
        size_t           dx;
345
6.70k
        size_t           dy;
346
6.70k
        int              ok = FIDO_ERR_INTERNAL;
347
6.70k
        int              nx;
348
6.70k
        int              ny;
349
350
6.70k
        if ((q = EC_KEY_get0_public_key(ec)) == NULL ||
351
6.70k
            (g = EC_GROUP_new_by_curve_name(es256_nid)) == NULL ||
352
6.70k
            (bnctx = BN_CTX_new()) == NULL)
353
46
                goto fail;
354
355
6.66k
        BN_CTX_start(bnctx);
356
357
6.66k
        if ((x = BN_CTX_get(bnctx)) == NULL ||
358
6.66k
            (y = BN_CTX_get(bnctx)) == NULL)
359
74
                goto fail;
360
361
6.58k
        if (EC_POINT_is_on_curve(g, q, bnctx) != 1) {
362
0
                fido_log_debug("%s: EC_POINT_is_on_curve", __func__);
363
0
                ok = FIDO_ERR_INVALID_ARGUMENT;
364
0
                goto fail;
365
0
        }
366
367
6.58k
        if (EC_POINT_get_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
368
6.58k
            (nx = BN_num_bytes(x)) < 0 || (size_t)nx > sizeof(pk->x) ||
369
6.58k
            (ny = BN_num_bytes(y)) < 0 || (size_t)ny > sizeof(pk->y)) {
370
34
                fido_log_debug("%s: EC_POINT_get_affine_coordinates_GFp",
371
34
                    __func__);
372
34
                goto fail;
373
34
        }
374
375
6.55k
        dx = sizeof(pk->x) - (size_t)nx;
376
6.55k
        dy = sizeof(pk->y) - (size_t)ny;
377
378
6.55k
        if ((nx = BN_bn2bin(x, pk->x + dx)) < 0 || (size_t)nx > sizeof(pk->x) ||
379
6.55k
            (ny = BN_bn2bin(y, pk->y + dy)) < 0 || (size_t)ny > sizeof(pk->y)) {
380
80
                fido_log_debug("%s: BN_bn2bin", __func__);
381
80
                goto fail;
382
80
        }
383
384
6.47k
        ok = FIDO_OK;
385
6.70k
fail:
386
6.70k
        EC_GROUP_free(g);
387
388
6.70k
        if (bnctx != NULL) {
389
6.66k
                BN_CTX_end(bnctx);
390
6.66k
                BN_CTX_free(bnctx);
391
6.66k
        }
392
393
6.70k
        return (ok);
394
6.47k
}
395
396
int
397
es256_pk_from_EVP_PKEY(es256_pk_t *pk, const EVP_PKEY *pkey)
398
30
{
399
30
        const EC_KEY *ec;
400
401
30
        if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC ||
402
30
            (ec = get0_EC_KEY(pkey)) == NULL)
403
3
                return (FIDO_ERR_INVALID_ARGUMENT);
404
405
27
        return (es256_pk_from_EC_KEY(pk, ec));
406
30
}
407
408
EVP_PKEY *
409
es256_sk_to_EVP_PKEY(const es256_sk_t *k)
410
3.64k
{
411
3.64k
        BN_CTX          *bnctx = NULL;
412
3.64k
        EC_KEY          *ec = NULL;
413
3.64k
        EVP_PKEY        *pkey = NULL;
414
3.64k
        BIGNUM          *d = NULL;
415
3.64k
        int              ok = -1;
416
417
3.64k
        if ((bnctx = BN_CTX_new()) == NULL)
418
12
                goto fail;
419
420
3.63k
        BN_CTX_start(bnctx);
421
422
3.63k
        if ((d = BN_CTX_get(bnctx)) == NULL ||
423
3.63k
            BN_bin2bn(k->d, sizeof(k->d), d) == NULL) {
424
30
                fido_log_debug("%s: BN_bin2bn", __func__);
425
30
                goto fail;
426
30
        }
427
428
3.60k
        if ((ec = EC_KEY_new_by_curve_name(es256_nid)) == NULL ||
429
3.60k
            EC_KEY_set_private_key(ec, d) == 0) {
430
16
                fido_log_debug("%s: EC_KEY_set_private_key", __func__);
431
16
                goto fail;
432
16
        }
433
434
3.58k
        if ((pkey = EVP_PKEY_new()) == NULL ||
435
3.58k
            EVP_PKEY_assign_EC_KEY(pkey, ec) == 0) {
436
33
                fido_log_debug("%s: EVP_PKEY_assign_EC_KEY", __func__);
437
33
                goto fail;
438
33
        }
439
440
3.55k
        ec = NULL; /* at this point, ec belongs to evp */
441
442
3.55k
        ok = 0;
443
3.64k
fail:
444
3.64k
        if (bnctx != NULL) {
445
3.63k
                BN_CTX_end(bnctx);
446
3.63k
                BN_CTX_free(bnctx);
447
3.63k
        }
448
449
3.64k
        if (ec != NULL)
450
33
                EC_KEY_free(ec);
451
452
3.64k
        if (ok < 0 && pkey != NULL) {
453
19
                EVP_PKEY_free(pkey);
454
19
                pkey = NULL;
455
19
        }
456
457
3.64k
        return (pkey);
458
3.55k
}
459
460
int
461
es256_derive_pk(const es256_sk_t *sk, es256_pk_t *pk)
462
6.83k
{
463
6.83k
        BIGNUM          *d = NULL;
464
6.83k
        EC_KEY          *ec = NULL;
465
6.83k
        EC_POINT        *q = NULL;
466
6.83k
        const EC_GROUP  *g = NULL;
467
6.83k
        int              ok = -1;
468
469
6.83k
        if ((d = BN_bin2bn(sk->d, (int)sizeof(sk->d), NULL)) == NULL ||
470
6.83k
            (ec = EC_KEY_new_by_curve_name(es256_nid)) == NULL ||
471
6.83k
            (g = EC_KEY_get0_group(ec)) == NULL ||
472
6.83k
            (q = EC_POINT_new(g)) == NULL) {
473
151
                fido_log_debug("%s: get", __func__);
474
151
                goto fail;
475
151
        }
476
477
6.68k
        if (EC_POINT_mul(g, q, d, NULL, NULL, NULL) == 0 ||
478
6.68k
            EC_KEY_set_public_key(ec, q) == 0 ||
479
6.68k
            es256_pk_from_EC_KEY(pk, ec) != FIDO_OK) {
480
226
                fido_log_debug("%s: set", __func__);
481
226
                goto fail;
482
226
        }
483
484
6.45k
        ok = 0;
485
6.83k
fail:
486
6.83k
        if (d != NULL)
487
6.79k
                BN_clear_free(d);
488
6.83k
        if (q != NULL)
489
6.68k
                EC_POINT_free(q);
490
6.83k
        if (ec != NULL)
491
6.75k
                EC_KEY_free(ec);
492
493
6.83k
        return (ok);
494
6.45k
}
495
496
int
497
es256_verify_sig(const fido_blob_t *dgst, EVP_PKEY *pkey,
498
    const fido_blob_t *sig)
499
44
{
500
44
        EVP_PKEY_CTX    *pctx = NULL;
501
44
        int              ok = -1;
502
503
44
        if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC) {
504
0
                fido_log_debug("%s: EVP_PKEY_base_id", __func__);
505
0
                goto fail;
506
0
        }
507
508
44
        if ((pctx = EVP_PKEY_CTX_new(pkey, NULL)) == NULL ||
509
44
            EVP_PKEY_verify_init(pctx) != 1 ||
510
44
            EVP_PKEY_verify(pctx, sig->ptr, sig->len, dgst->ptr,
511
44
            dgst->len) != 1) {
512
44
                fido_log_debug("%s: EVP_PKEY_verify", __func__);
513
44
                goto fail;
514
44
        }
515
516
0
        ok = 0;
517
44
fail:
518
44
        EVP_PKEY_CTX_free(pctx);
519
520
44
        return (ok);
521
0
}
522
523
int
524
es256_pk_verify_sig(const fido_blob_t *dgst, const es256_pk_t *pk,
525
    const fido_blob_t *sig)
526
58
{
527
58
        EVP_PKEY        *pkey;
528
58
        int              ok = -1;
529
530
58
        if ((pkey = es256_pk_to_EVP_PKEY(pk)) == NULL ||
531
58
            es256_verify_sig(dgst, pkey, sig) < 0) {
532
58
                fido_log_debug("%s: es256_verify_sig", __func__);
533
58
                goto fail;
534
58
        }
535
536
0
        ok = 0;
537
58
fail:
538
58
        EVP_PKEY_free(pkey);
539
540
58
        return (ok);
541
0
}