/*
* Copyright (c) 2018 Yubico AB. All rights reserved.
* Use of this source code is governed by a BSD-style
* license that can be found in the LICENSE file.
*/
#include <openssl/bn.h>
#include <openssl/obj_mac.h>
#include "fido.h"
#include "fido/es256.h"
static int
decode_coord(const cbor_item_t *item, void *xy, size_t xy_len)
{
if (cbor_isa_bytestring(item) == false ||
cbor_bytestring_is_definite(item) == false ||
cbor_bytestring_length(item) != xy_len) {
fido_log_debug("%s: cbor type", __func__);
return (-1);
}
memcpy(xy, cbor_bytestring_handle(item), xy_len);
return (0);
}
static int
decode_pubkey_point(const cbor_item_t *key, const cbor_item_t *val, void *arg)
{
es256_pk_t *k = arg;
if (cbor_isa_negint(key) == false ||
cbor_int_get_width(key) != CBOR_INT_8)
return (0); /* ignore */
switch (cbor_get_uint8(key)) {
case 1: /* x coordinate */
return (decode_coord(val, &k->x, sizeof(k->x)));
case 2: /* y coordinate */
return (decode_coord(val, &k->y, sizeof(k->y)));
}
return (0); /* ignore */
}
int
es256_pk_decode(const cbor_item_t *item, es256_pk_t *k)
{
if (cbor_isa_map(item) == false ||
cbor_map_is_definite(item) == false ||
cbor_map_iter(item, k, decode_pubkey_point) < 0) {
fido_log_debug("%s: cbor type", __func__);
return (-1);
}
return (0);
}
cbor_item_t *
es256_pk_encode(const es256_pk_t *pk, int ecdh)
{
cbor_item_t *item = NULL;
struct cbor_pair argv[5];
int alg;
int ok = -1;
memset(argv, 0, sizeof(argv));
if ((item = cbor_new_definite_map(5)) == NULL)
goto fail;
/* kty */
if ((argv[0].key = cbor_build_uint8(1)) == NULL ||
(argv[0].value = cbor_build_uint8(2)) == NULL ||
!cbor_map_add(item, argv[0]))
goto fail;
/*
* "The COSEAlgorithmIdentifier used is -25 (ECDH-ES +
* HKDF-256) although this is NOT the algorithm actually
* used. Setting this to a different value may result in
* compatibility issues."
*/
if (ecdh)
alg = COSE_ECDH_ES256;
else
alg = COSE_ES256;
/* alg */
if ((argv[1].key = cbor_build_uint8(3)) == NULL ||
(argv[1].value = cbor_build_negint8((uint8_t)(-alg - 1))) == NULL ||
!cbor_map_add(item, argv[1]))
goto fail;
/* crv */
if ((argv[2].key = cbor_build_negint8(0)) == NULL ||
(argv[2].value = cbor_build_uint8(1)) == NULL ||
!cbor_map_add(item, argv[2]))
goto fail;
/* x */
if ((argv[3].key = cbor_build_negint8(1)) == NULL ||
(argv[3].value = cbor_build_bytestring(pk->x,
sizeof(pk->x))) == NULL || !cbor_map_add(item, argv[3]))
goto fail;
/* y */
if ((argv[4].key = cbor_build_negint8(2)) == NULL ||
(argv[4].value = cbor_build_bytestring(pk->y,
sizeof(pk->y))) == NULL || !cbor_map_add(item, argv[4]))
goto fail;
ok = 0;
fail:
if (ok < 0) {
if (item != NULL) {
cbor_decref(&item);
item = NULL;
}
}
for (size_t i = 0; i < 5; i++) {
if (argv[i].key)
cbor_decref(&argv[i].key);
if (argv[i].value)
cbor_decref(&argv[i].value);
}
return (item);
}
es256_sk_t *
es256_sk_new(void)
{
return (calloc(1, sizeof(es256_sk_t)));
}
void
es256_sk_free(es256_sk_t **skp)
{
es256_sk_t *sk;
if (skp == NULL || (sk = *skp) == NULL)
return;
freezero(sk, sizeof(*sk));
*skp = NULL;
}
es256_pk_t *
es256_pk_new(void)
{
return (calloc(1, sizeof(es256_pk_t)));
}
void
es256_pk_free(es256_pk_t **pkp)
{
es256_pk_t *pk;
if (pkp == NULL || (pk = *pkp) == NULL)
return;
freezero(pk, sizeof(*pk));
*pkp = NULL;
}
int
es256_pk_from_ptr(es256_pk_t *pk, const void *ptr, size_t len)
{
const uint8_t *p = ptr;
if (len < sizeof(*pk))
return (FIDO_ERR_INVALID_ARGUMENT);
if (len == sizeof(*pk) + 1 && *p == 0x04)
memcpy(pk, ++p, sizeof(*pk)); /* uncompressed format */
else
memcpy(pk, ptr, sizeof(*pk)); /* libfido2 x||y format */
return (FIDO_OK);
}
int
es256_pk_set_x(es256_pk_t *pk, const unsigned char *x)
{
memcpy(pk->x, x, sizeof(pk->x));
return (0);
}
int
es256_pk_set_y(es256_pk_t *pk, const unsigned char *y)
{
memcpy(pk->y, y, sizeof(pk->y));
return (0);
}
int
es256_sk_create(es256_sk_t *key)
{
EVP_PKEY_CTX *pctx = NULL;
EVP_PKEY_CTX *kctx = NULL;
EVP_PKEY *p = NULL;
EVP_PKEY *k = NULL;
const EC_KEY *ec;
const BIGNUM *d;
const int nid = NID_X9_62_prime256v1;
int n;
int ok = -1;
if ((pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_EC, NULL)) == NULL ||
EVP_PKEY_paramgen_init(pctx) <= 0 ||
EVP_PKEY_CTX_set_ec_paramgen_curve_nid(pctx, nid) <= 0 ||
EVP_PKEY_paramgen(pctx, &p) <= 0) {
fido_log_debug("%s: EVP_PKEY_paramgen", __func__);
goto fail;
}
if ((kctx = EVP_PKEY_CTX_new(p, NULL)) == NULL ||
EVP_PKEY_keygen_init(kctx) <= 0 || EVP_PKEY_keygen(kctx, &k) <= 0) {
fido_log_debug("%s: EVP_PKEY_keygen", __func__);
goto fail;
}
if ((ec = EVP_PKEY_get0_EC_KEY(k)) == NULL ||
(d = EC_KEY_get0_private_key(ec)) == NULL ||
(n = BN_num_bytes(d)) < 0 || (size_t)n > sizeof(key->d) ||
(n = BN_bn2bin(d, key->d)) < 0 || (size_t)n > sizeof(key->d)) {
fido_log_debug("%s: EC_KEY_get0_private_key", __func__);
goto fail;
}
ok = 0;
fail:
if (p != NULL)
EVP_PKEY_free(p);
if (k != NULL)
EVP_PKEY_free(k);
if (pctx != NULL)
EVP_PKEY_CTX_free(pctx);
if (kctx != NULL)
EVP_PKEY_CTX_free(kctx);
return (ok);
}
EVP_PKEY *
es256_pk_to_EVP_PKEY(const es256_pk_t *k)
{
BN_CTX *bnctx = NULL;
EC_KEY *ec = NULL;
EC_POINT *q = NULL;
EVP_PKEY *pkey = NULL;
BIGNUM *x = NULL;
BIGNUM *y = NULL;
const EC_GROUP *g = NULL;
const int nid = NID_X9_62_prime256v1;
int ok = -1;
if ((bnctx = BN_CTX_new()) == NULL)
goto fail;
BN_CTX_start(bnctx);
if ((x = BN_CTX_get(bnctx)) == NULL ||
(y = BN_CTX_get(bnctx)) == NULL)
goto fail;
if (BN_bin2bn(k->x, sizeof(k->x), x) == NULL ||
BN_bin2bn(k->y, sizeof(k->y), y) == NULL) {
fido_log_debug("%s: BN_bin2bn", __func__);
goto fail;
}
if ((ec = EC_KEY_new_by_curve_name(nid)) == NULL ||
(g = EC_KEY_get0_group(ec)) == NULL) {
fido_log_debug("%s: EC_KEY init", __func__);
goto fail;
}
if ((q = EC_POINT_new(g)) == NULL ||
EC_POINT_set_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
EC_KEY_set_public_key(ec, q) == 0) {
fido_log_debug("%s: EC_KEY_set_public_key", __func__);
goto fail;
}
if ((pkey = EVP_PKEY_new()) == NULL ||
EVP_PKEY_assign_EC_KEY(pkey, ec) == 0) {
fido_log_debug("%s: EVP_PKEY_assign_EC_KEY", __func__);
goto fail;
}
ec = NULL; /* at this point, ec belongs to evp */
ok = 0;
fail:
if (bnctx != NULL) {
BN_CTX_end(bnctx);
BN_CTX_free(bnctx);
}
if (ec != NULL)
EC_KEY_free(ec);
if (q != NULL)
EC_POINT_free(q);
if (ok < 0 && pkey != NULL) {
EVP_PKEY_free(pkey);
pkey = NULL;
}
return (pkey);
}
int
es256_pk_from_EC_KEY(es256_pk_t *pk, const EC_KEY *ec)
{
BN_CTX *bnctx = NULL;
BIGNUM *x = NULL;
BIGNUM *y = NULL;
const EC_POINT *q = NULL;
const EC_GROUP *g = NULL;
int ok = FIDO_ERR_INTERNAL;
int n;
if ((q = EC_KEY_get0_public_key(ec)) == NULL ||
(g = EC_KEY_get0_group(ec)) == NULL ||
(bnctx = BN_CTX_new()) == NULL)
goto fail;
BN_CTX_start(bnctx);
if ((x = BN_CTX_get(bnctx)) == NULL ||
(y = BN_CTX_get(bnctx)) == NULL)
goto fail;
if (EC_POINT_get_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
(n = BN_num_bytes(x)) < 0 || (size_t)n > sizeof(pk->x) ||
(n = BN_num_bytes(y)) < 0 || (size_t)n > sizeof(pk->y)) {
fido_log_debug("%s: EC_POINT_get_affine_coordinates_GFp",
__func__);
goto fail;
}
if ((n = BN_bn2bin(x, pk->x)) < 0 || (size_t)n > sizeof(pk->x) ||
(n = BN_bn2bin(y, pk->y)) < 0 || (size_t)n > sizeof(pk->y)) {
fido_log_debug("%s: BN_bn2bin", __func__);
goto fail;
}
ok = FIDO_OK;
fail:
if (bnctx != NULL) {
BN_CTX_end(bnctx);
BN_CTX_free(bnctx);
}
return (ok);
}
EVP_PKEY *
es256_sk_to_EVP_PKEY(const es256_sk_t *k)
{
BN_CTX *bnctx = NULL;
EC_KEY *ec = NULL;
EVP_PKEY *pkey = NULL;
BIGNUM *d = NULL;
const int nid = NID_X9_62_prime256v1;
int ok = -1;
if ((bnctx = BN_CTX_new()) == NULL)
goto fail;
BN_CTX_start(bnctx);
if ((d = BN_CTX_get(bnctx)) == NULL ||
BN_bin2bn(k->d, sizeof(k->d), d) == NULL) {
fido_log_debug("%s: BN_bin2bn", __func__);
goto fail;
}
if ((ec = EC_KEY_new_by_curve_name(nid)) == NULL ||
EC_KEY_set_private_key(ec, d) == 0) {
fido_log_debug("%s: EC_KEY_set_private_key", __func__);
goto fail;
}
if ((pkey = EVP_PKEY_new()) == NULL ||
EVP_PKEY_assign_EC_KEY(pkey, ec) == 0) {
fido_log_debug("%s: EVP_PKEY_assign_EC_KEY", __func__);
goto fail;
}
ec = NULL; /* at this point, ec belongs to evp */
ok = 0;
fail:
if (bnctx != NULL) {
BN_CTX_end(bnctx);
BN_CTX_free(bnctx);
}
if (ec != NULL)
EC_KEY_free(ec);
if (ok < 0 && pkey != NULL) {
EVP_PKEY_free(pkey);
pkey = NULL;
}
return (pkey);
}
int
es256_derive_pk(const es256_sk_t *sk, es256_pk_t *pk)
{
BIGNUM *d = NULL;
EC_KEY *ec = NULL;
EC_POINT *q = NULL;
const EC_GROUP *g = NULL;
const int nid = NID_X9_62_prime256v1;
int ok = -1;
if ((d = BN_bin2bn(sk->d, (int)sizeof(sk->d), NULL)) == NULL ||
(ec = EC_KEY_new_by_curve_name(nid)) == NULL ||
(g = EC_KEY_get0_group(ec)) == NULL ||
(q = EC_POINT_new(g)) == NULL) {
fido_log_debug("%s: get", __func__);
goto fail;
}
if (EC_POINT_mul(g, q, d, NULL, NULL, NULL) == 0 ||
EC_KEY_set_public_key(ec, q) == 0 ||
es256_pk_from_EC_KEY(pk, ec) != FIDO_OK) {
fido_log_debug("%s: set", __func__);
goto fail;
}
ok = 0;
fail:
if (d != NULL)
BN_clear_free(d);
if (q != NULL)
EC_POINT_free(q);
if (ec != NULL)
EC_KEY_free(ec);
return (ok);
}