Coverage Report

Created: 2022-04-27 14:33

/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
 */
6
7
#include <openssl/bn.h>
8
#include <openssl/ecdsa.h>
9
#include <openssl/obj_mac.h>
10
11
#include "fido.h"
12
#include "fido/es256.h"
13
14
#if OPENSSL_VERSION_NUMBER >= 0x30000000
15
#define get0_EC_KEY(x)  EVP_PKEY_get0_EC_KEY((x))
16
#else
17
12
#define get0_EC_KEY(x)  EVP_PKEY_get0((x))
18
#endif
19
20
static const int es256_nid = NID_X9_62_prime256v1;
21
22
static int
23
decode_coord(const cbor_item_t *item, void *xy, size_t xy_len)
24
10.0k
{
25
10.0k
        if (cbor_isa_bytestring(item) == false ||
26
10.0k
            cbor_bytestring_is_definite(item) == false ||
27
10.0k
            cbor_bytestring_length(item) != xy_len) {
28
71
                fido_log_debug("%s: cbor type", __func__);
29
71
                return (-1);
30
71
        }
31
32
9.96k
        memcpy(xy, cbor_bytestring_handle(item), xy_len);
33
34
9.96k
        return (0);
35
10.0k
}
36
37
static int
38
decode_pubkey_point(const cbor_item_t *key, const cbor_item_t *val, void *arg)
39
25.5k
{
40
25.5k
        es256_pk_t *k = arg;
41
42
25.5k
        if (cbor_isa_negint(key) == false ||
43
25.5k
            cbor_int_get_width(key) != CBOR_INT_8)
44
12.5k
                return (0); /* ignore */
45
46
13.0k
        switch (cbor_get_uint8(key)) {
47
5.08k
        case 1: /* x coordinate */
48
5.08k
                return (decode_coord(val, &k->x, sizeof(k->x)));
49
4.94k
        case 2: /* y coordinate */
50
4.94k
                return (decode_coord(val, &k->y, sizeof(k->y)));
51
13.0k
        }
52
53
2.99k
        return (0); /* ignore */
54
13.0k
}
55
56
int
57
es256_pk_decode(const cbor_item_t *item, es256_pk_t *k)
58
5.18k
{
59
5.18k
        if (cbor_isa_map(item) == false ||
60
5.18k
            cbor_map_is_definite(item) == false ||
61
5.18k
            cbor_map_iter(item, k, decode_pubkey_point) < 0) {
62
143
                fido_log_debug("%s: cbor type", __func__);
63
143
                return (-1);
64
143
        }
65
66
5.03k
        return (0);
67
5.18k
}
68
69
cbor_item_t *
70
es256_pk_encode(const es256_pk_t *pk, int ecdh)
71
3.11k
{
72
3.11k
        cbor_item_t             *item = NULL;
73
3.11k
        struct cbor_pair         argv[5];
74
3.11k
        int                      alg;
75
3.11k
        int                      ok = -1;
76
77
3.11k
        memset(argv, 0, sizeof(argv));
78
79
3.11k
        if ((item = cbor_new_definite_map(5)) == NULL)
80
12
                goto fail;
81
82
        /* kty */
83
3.10k
        if ((argv[0].key = cbor_build_uint8(1)) == NULL ||
84
3.10k
            (argv[0].value = cbor_build_uint8(2)) == NULL ||
85
3.10k
            !cbor_map_add(item, argv[0]))
86
36
                goto fail;
87
88
        /*
89
         * "The COSEAlgorithmIdentifier used is -25 (ECDH-ES +
90
         * HKDF-256) although this is NOT the algorithm actually
91
         * used. Setting this to a different value may result in
92
         * compatibility issues."
93
         */
94
3.06k
        if (ecdh)
95
2.97k
                alg = COSE_ECDH_ES256;
96
91
        else
97
91
                alg = COSE_ES256;
98
99
        /* alg */
100
3.06k
        if ((argv[1].key = cbor_build_uint8(3)) == NULL ||
101
3.06k
            (argv[1].value = cbor_build_negint8((uint8_t)(-alg - 1))) == NULL ||
102
3.06k
            !cbor_map_add(item, argv[1]))
103
39
                goto fail;
104
105
        /* crv */
106
3.02k
        if ((argv[2].key = cbor_build_negint8(0)) == NULL ||
107
3.02k
            (argv[2].value = cbor_build_uint8(1)) == NULL ||
108
3.02k
            !cbor_map_add(item, argv[2]))
109
32
                goto fail;
110
111
        /* x */
112
2.99k
        if ((argv[3].key = cbor_build_negint8(1)) == NULL ||
113
2.99k
            (argv[3].value = cbor_build_bytestring(pk->x,
114
2.98k
            sizeof(pk->x))) == NULL || !cbor_map_add(item, argv[3]))
115
32
                goto fail;
116
117
        /* y */
118
2.96k
        if ((argv[4].key = cbor_build_negint8(2)) == NULL ||
119
2.96k
            (argv[4].value = cbor_build_bytestring(pk->y,
120
2.95k
            sizeof(pk->y))) == NULL || !cbor_map_add(item, argv[4]))
121
34
                goto fail;
122
123
2.93k
        ok = 0;
124
3.11k
fail:
125
3.11k
        if (ok < 0) {
126
185
                if (item != NULL) {
127
173
                        cbor_decref(&item);
128
173
                        item = NULL;
129
173
                }
130
185
        }
131
132
18.6k
        for (size_t i = 0; i < 5; i++) {
133
15.5k
                if (argv[i].key)
134
15.1k
                        cbor_decref(&argv[i].key);
135
15.5k
                if (argv[i].value)
136
15.0k
                        cbor_decref(&argv[i].value);
137
15.5k
        }
138
139
3.11k
        return (item);
140
2.93k
}
141
142
es256_sk_t *
143
es256_sk_new(void)
144
7.52k
{
145
7.52k
        return (calloc(1, sizeof(es256_sk_t)));
146
7.52k
}
147
148
void
149
es256_sk_free(es256_sk_t **skp)
150
7.52k
{
151
7.52k
        es256_sk_t *sk;
152
153
7.52k
        if (skp == NULL || (sk = *skp) == NULL)
154
29
                return;
155
156
7.49k
        freezero(sk, sizeof(*sk));
157
7.49k
        *skp = NULL;
158
7.49k
}
159
160
es256_pk_t *
161
es256_pk_new(void)
162
14.8k
{
163
14.8k
        return (calloc(1, sizeof(es256_pk_t)));
164
14.8k
}
165
166
void
167
es256_pk_free(es256_pk_t **pkp)
168
29.3k
{
169
29.3k
        es256_pk_t *pk;
170
171
29.3k
        if (pkp == NULL || (pk = *pkp) == NULL)
172
14.5k
                return;
173
174
14.8k
        freezero(pk, sizeof(*pk));
175
14.8k
        *pkp = NULL;
176
14.8k
}
177
178
int
179
es256_pk_from_ptr(es256_pk_t *pk, const void *ptr, size_t len)
180
514
{
181
514
        const uint8_t   *p = ptr;
182
514
        EVP_PKEY        *pkey;
183
184
514
        if (len < sizeof(*pk))
185
458
                return (FIDO_ERR_INVALID_ARGUMENT);
186
187
56
        if (len == sizeof(*pk) + 1 && *p == 0x04)
188
2
                memcpy(pk, ++p, sizeof(*pk)); /* uncompressed format */
189
54
        else
190
54
                memcpy(pk, ptr, sizeof(*pk)); /* libfido2 x||y format */
191
192
56
        if ((pkey = es256_pk_to_EVP_PKEY(pk)) == NULL) {
193
41
                fido_log_debug("%s: es256_pk_to_EVP_PKEY", __func__);
194
41
                explicit_bzero(pk, sizeof(*pk));
195
41
                return (FIDO_ERR_INVALID_ARGUMENT);
196
41
        }
197
198
15
        EVP_PKEY_free(pkey);
199
200
15
        return (FIDO_OK);
201
56
}
202
203
int
204
es256_pk_set_x(es256_pk_t *pk, const unsigned char *x)
205
91
{
206
91
        memcpy(pk->x, x, sizeof(pk->x));
207
208
91
        return (0);
209
91
}
210
211
int
212
es256_pk_set_y(es256_pk_t *pk, const unsigned char *y)
213
91
{
214
91
        memcpy(pk->y, y, sizeof(pk->y));
215
216
91
        return (0);
217
91
}
218
219
int
220
es256_sk_create(es256_sk_t *key)
221
7.46k
{
222
7.46k
        EVP_PKEY_CTX    *pctx = NULL;
223
7.46k
        EVP_PKEY_CTX    *kctx = NULL;
224
7.46k
        EVP_PKEY        *p = NULL;
225
7.46k
        EVP_PKEY        *k = NULL;
226
7.46k
        const EC_KEY    *ec;
227
7.46k
        const BIGNUM    *d;
228
7.46k
        int              n;
229
7.46k
        int              ok = -1;
230
231
7.46k
        if ((pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL)) == NULL ||
232
7.46k
            EVP_PKEY_paramgen_init(pctx) <= 0 ||
233
7.46k
            EVP_PKEY_CTX_set_ec_paramgen_curve_nid(pctx, es256_nid) <= 0 ||
234
7.46k
            EVP_PKEY_paramgen(pctx, &p) <= 0) {
235
131
                fido_log_debug("%s: EVP_PKEY_paramgen", __func__);
236
131
                goto fail;
237
131
        }
238
239
7.32k
        if ((kctx = EVP_PKEY_CTX_new(p, NULL)) == NULL ||
240
7.32k
            EVP_PKEY_keygen_init(kctx) <= 0 || EVP_PKEY_keygen(kctx, &k) <= 0) {
241
103
                fido_log_debug("%s: EVP_PKEY_keygen", __func__);
242
103
                goto fail;
243
103
        }
244
245
7.22k
        if ((ec = EVP_PKEY_get0_EC_KEY(k)) == NULL ||
246
7.22k
            (d = EC_KEY_get0_private_key(ec)) == NULL ||
247
7.22k
            (n = BN_num_bytes(d)) < 0 || (size_t)n > sizeof(key->d) ||
248
7.22k
            (n = BN_bn2bin(d, key->d)) < 0 || (size_t)n > sizeof(key->d)) {
249
99
                fido_log_debug("%s: EC_KEY_get0_private_key", __func__);
250
99
                goto fail;
251
99
        }
252
253
7.12k
        ok = 0;
254
7.46k
fail:
255
7.46k
        if (p != NULL)
256
7.32k
                EVP_PKEY_free(p);
257
7.46k
        if (k != NULL)
258
7.22k
                EVP_PKEY_free(k);
259
7.46k
        if (pctx != NULL)
260
7.43k
                EVP_PKEY_CTX_free(pctx);
261
7.46k
        if (kctx != NULL)
262
7.29k
                EVP_PKEY_CTX_free(kctx);
263
264
7.46k
        return (ok);
265
7.12k
}
266
267
EVP_PKEY *
268
es256_pk_to_EVP_PKEY(const es256_pk_t *k)
269
4.39k
{
270
4.39k
        BN_CTX          *bnctx = NULL;
271
4.39k
        EC_KEY          *ec = NULL;
272
4.39k
        EC_POINT        *q = NULL;
273
4.39k
        EVP_PKEY        *pkey = NULL;
274
4.39k
        BIGNUM          *x = NULL;
275
4.39k
        BIGNUM          *y = NULL;
276
4.39k
        const EC_GROUP  *g = NULL;
277
4.39k
        int              ok = -1;
278
279
4.39k
        if ((bnctx = BN_CTX_new()) == NULL)
280
14
                goto fail;
281
282
4.38k
        BN_CTX_start(bnctx);
283
284
4.38k
        if ((x = BN_CTX_get(bnctx)) == NULL ||
285
4.38k
            (y = BN_CTX_get(bnctx)) == NULL)
286
37
                goto fail;
287
288
4.34k
        if (BN_bin2bn(k->x, sizeof(k->x), x) == NULL ||
289
4.34k
            BN_bin2bn(k->y, sizeof(k->y), y) == NULL) {
290
26
                fido_log_debug("%s: BN_bin2bn", __func__);
291
26
                goto fail;
292
26
        }
293
294
4.32k
        if ((ec = EC_KEY_new_by_curve_name(es256_nid)) == NULL ||
295
4.32k
            (g = EC_KEY_get0_group(ec)) == NULL) {
296
34
                fido_log_debug("%s: EC_KEY init", __func__);
297
34
                goto fail;
298
34
        }
299
300
4.28k
        if ((q = EC_POINT_new(g)) == NULL ||
301
4.28k
            EC_POINT_set_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
302
4.28k
            EC_KEY_set_public_key(ec, q) == 0) {
303
678
                fido_log_debug("%s: EC_KEY_set_public_key", __func__);
304
678
                goto fail;
305
678
        }
306
307
3.60k
        if ((pkey = EVP_PKEY_new()) == NULL ||
308
3.60k
            EVP_PKEY_assign_EC_KEY(pkey, ec) == 0) {
309
20
                fido_log_debug("%s: EVP_PKEY_assign_EC_KEY", __func__);
310
20
                goto fail;
311
20
        }
312
313
3.58k
        ec = NULL; /* at this point, ec belongs to evp */
314
315
3.58k
        ok = 0;
316
4.39k
fail:
317
4.39k
        if (bnctx != NULL) {
318
4.38k
                BN_CTX_end(bnctx);
319
4.38k
                BN_CTX_free(bnctx);
320
4.38k
        }
321
322
4.39k
        if (ec != NULL)
323
718
                EC_KEY_free(ec);
324
4.39k
        if (q != NULL)
325
4.26k
                EC_POINT_free(q);
326
327
4.39k
        if (ok < 0 && pkey != NULL) {
328
11
                EVP_PKEY_free(pkey);
329
11
                pkey = NULL;
330
11
        }
331
332
4.39k
        return (pkey);
333
3.58k
}
334
335
int
336
es256_pk_from_EC_KEY(es256_pk_t *pk, const EC_KEY *ec)
337
6.99k
{
338
6.99k
        BN_CTX          *bnctx = NULL;
339
6.99k
        BIGNUM          *x = NULL;
340
6.99k
        BIGNUM          *y = NULL;
341
6.99k
        const EC_POINT  *q = NULL;
342
6.99k
        EC_GROUP        *g = NULL;
343
6.99k
        size_t           dx;
344
6.99k
        size_t           dy;
345
6.99k
        int              ok = FIDO_ERR_INTERNAL;
346
6.99k
        int              nx;
347
6.99k
        int              ny;
348
349
6.99k
        if ((q = EC_KEY_get0_public_key(ec)) == NULL ||
350
6.99k
            (g = EC_GROUP_new_by_curve_name(es256_nid)) == NULL ||
351
6.99k
            (bnctx = BN_CTX_new()) == NULL)
352
31
                goto fail;
353
354
6.96k
        BN_CTX_start(bnctx);
355
356
6.96k
        if ((x = BN_CTX_get(bnctx)) == NULL ||
357
6.96k
            (y = BN_CTX_get(bnctx)) == NULL)
358
83
                goto fail;
359
360
6.88k
        if (EC_POINT_is_on_curve(g, q, bnctx) != 1) {
361
0
                fido_log_debug("%s: EC_POINT_is_on_curve", __func__);
362
0
                ok = FIDO_ERR_INVALID_ARGUMENT;
363
0
                goto fail;
364
0
        }
365
366
6.88k
        if (EC_POINT_get_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
367
6.88k
            (nx = BN_num_bytes(x)) < 0 || (size_t)nx > sizeof(pk->x) ||
368
6.88k
            (ny = BN_num_bytes(y)) < 0 || (size_t)ny > sizeof(pk->y)) {
369
29
                fido_log_debug("%s: EC_POINT_get_affine_coordinates_GFp",
370
29
                    __func__);
371
29
                goto fail;
372
29
        }
373
374
6.85k
        dx = sizeof(pk->x) - (size_t)nx;
375
6.85k
        dy = sizeof(pk->y) - (size_t)ny;
376
377
6.85k
        if ((nx = BN_bn2bin(x, pk->x + dx)) < 0 || (size_t)nx > sizeof(pk->x) ||
378
6.85k
            (ny = BN_bn2bin(y, pk->y + dy)) < 0 || (size_t)ny > sizeof(pk->y)) {
379
68
                fido_log_debug("%s: BN_bn2bin", __func__);
380
68
                goto fail;
381
68
        }
382
383
6.78k
        ok = FIDO_OK;
384
6.99k
fail:
385
6.99k
        EC_GROUP_free(g);
386
387
6.99k
        if (bnctx != NULL) {
388
6.96k
                BN_CTX_end(bnctx);
389
6.96k
                BN_CTX_free(bnctx);
390
6.96k
        }
391
392
6.99k
        return (ok);
393
6.78k
}
394
395
int
396
es256_pk_from_EVP_PKEY(es256_pk_t *pk, const EVP_PKEY *pkey)
397
12
{
398
12
        const EC_KEY *ec;
399
400
12
        if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC ||
401
12
            (ec = get0_EC_KEY(pkey)) == NULL)
402
0
                return (FIDO_ERR_INVALID_ARGUMENT);
403
404
12
        return (es256_pk_from_EC_KEY(pk, ec));
405
12
}
406
407
EVP_PKEY *
408
es256_sk_to_EVP_PKEY(const es256_sk_t *k)
409
3.55k
{
410
3.55k
        BN_CTX          *bnctx = NULL;
411
3.55k
        EC_KEY          *ec = NULL;
412
3.55k
        EVP_PKEY        *pkey = NULL;
413
3.55k
        BIGNUM          *d = NULL;
414
3.55k
        int              ok = -1;
415
416
3.55k
        if ((bnctx = BN_CTX_new()) == NULL)
417
11
                goto fail;
418
419
3.54k
        BN_CTX_start(bnctx);
420
421
3.54k
        if ((d = BN_CTX_get(bnctx)) == NULL ||
422
3.54k
            BN_bin2bn(k->d, sizeof(k->d), d) == NULL) {
423
27
                fido_log_debug("%s: BN_bin2bn", __func__);
424
27
                goto fail;
425
27
        }
426
427
3.51k
        if ((ec = EC_KEY_new_by_curve_name(es256_nid)) == NULL ||
428
3.51k
            EC_KEY_set_private_key(ec, d) == 0) {
429
11
                fido_log_debug("%s: EC_KEY_set_private_key", __func__);
430
11
                goto fail;
431
11
        }
432
433
3.50k
        if ((pkey = EVP_PKEY_new()) == NULL ||
434
3.50k
            EVP_PKEY_assign_EC_KEY(pkey, ec) == 0) {
435
21
                fido_log_debug("%s: EVP_PKEY_assign_EC_KEY", __func__);
436
21
                goto fail;
437
21
        }
438
439
3.48k
        ec = NULL; /* at this point, ec belongs to evp */
440
441
3.48k
        ok = 0;
442
3.55k
fail:
443
3.55k
        if (bnctx != NULL) {
444
3.54k
                BN_CTX_end(bnctx);
445
3.54k
                BN_CTX_free(bnctx);
446
3.54k
        }
447
448
3.55k
        if (ec != NULL)
449
21
                EC_KEY_free(ec);
450
451
3.55k
        if (ok < 0 && pkey != NULL) {
452
11
                EVP_PKEY_free(pkey);
453
11
                pkey = NULL;
454
11
        }
455
456
3.55k
        return (pkey);
457
3.48k
}
458
459
int
460
es256_derive_pk(const es256_sk_t *sk, es256_pk_t *pk)
461
7.12k
{
462
7.12k
        BIGNUM          *d = NULL;
463
7.12k
        EC_KEY          *ec = NULL;
464
7.12k
        EC_POINT        *q = NULL;
465
7.12k
        const EC_GROUP  *g = NULL;
466
7.12k
        int              ok = -1;
467
468
7.12k
        if ((d = BN_bin2bn(sk->d, (int)sizeof(sk->d), NULL)) == NULL ||
469
7.12k
            (ec = EC_KEY_new_by_curve_name(es256_nid)) == NULL ||
470
7.12k
            (g = EC_KEY_get0_group(ec)) == NULL ||
471
7.12k
            (q = EC_POINT_new(g)) == NULL) {
472
140
                fido_log_debug("%s: get", __func__);
473
140
                goto fail;
474
140
        }
475
476
6.98k
        if (EC_POINT_mul(g, q, d, NULL, NULL, NULL) == 0 ||
477
6.98k
            EC_KEY_set_public_key(ec, q) == 0 ||
478
6.98k
            es256_pk_from_EC_KEY(pk, ec) != FIDO_OK) {
479
210
                fido_log_debug("%s: set", __func__);
480
210
                goto fail;
481
210
        }
482
483
6.77k
        ok = 0;
484
7.12k
fail:
485
7.12k
        if (d != NULL)
486
7.08k
                BN_clear_free(d);
487
7.12k
        if (q != NULL)
488
6.98k
                EC_POINT_free(q);
489
7.12k
        if (ec != NULL)
490
7.05k
                EC_KEY_free(ec);
491
492
7.12k
        return (ok);
493
6.77k
}
494
495
int
496
es256_verify_sig(const fido_blob_t *dgst, EVP_PKEY *pkey,
497
    const fido_blob_t *sig)
498
46
{
499
46
        EVP_PKEY_CTX    *pctx = NULL;
500
46
        int              ok = -1;
501
502
46
        if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC) {
503
0
                fido_log_debug("%s: EVP_PKEY_base_id", __func__);
504
0
                goto fail;
505
0
        }
506
507
46
        if ((pctx = EVP_PKEY_CTX_new(pkey, NULL)) == NULL ||
508
46
            EVP_PKEY_verify_init(pctx) != 1 ||
509
46
            EVP_PKEY_verify(pctx, sig->ptr, sig->len, dgst->ptr,
510
46
            dgst->len) != 1) {
511
46
                fido_log_debug("%s: EVP_PKEY_verify", __func__);
512
46
                goto fail;
513
46
        }
514
515
0
        ok = 0;
516
46
fail:
517
46
        EVP_PKEY_CTX_free(pctx);
518
519
46
        return (ok);
520
0
}
521
522
int
523
es256_pk_verify_sig(const fido_blob_t *dgst, const es256_pk_t *pk,
524
    const fido_blob_t *sig)
525
39
{
526
39
        EVP_PKEY        *pkey;
527
39
        int              ok = -1;
528
529
39
        if ((pkey = es256_pk_to_EVP_PKEY(pk)) == NULL ||
530
39
            es256_verify_sig(dgst, pkey, sig) < 0) {
531
39
                fido_log_debug("%s: es256_verify_sig", __func__);
532
39
                goto fail;
533
39
        }
534
535
0
        ok = 0;
536
39
fail:
537
39
        EVP_PKEY_free(pkey);
538
539
39
        return (ok);
540
0
}