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-rw-r--r--src/es256.c541
1 files changed, 541 insertions, 0 deletions
diff --git a/src/es256.c b/src/es256.c
new file mode 100644
index 0000000..17efb0a
--- /dev/null
+++ b/src/es256.c
@@ -0,0 +1,541 @@
+/*
+ * Copyright (c) 2018-2022 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.
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <openssl/bn.h>
+#include <openssl/ecdsa.h>
+#include <openssl/obj_mac.h>
+
+#include "fido.h"
+#include "fido/es256.h"
+
+#if OPENSSL_VERSION_NUMBER >= 0x30000000
+#define get0_EC_KEY(x) EVP_PKEY_get0_EC_KEY((x))
+#else
+#define get0_EC_KEY(x) EVP_PKEY_get0((x))
+#endif
+
+static const int es256_nid = NID_X9_62_prime256v1;
+
+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;
+ EVP_PKEY *pkey;
+
+ 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 */
+
+ if ((pkey = es256_pk_to_EVP_PKEY(pk)) == NULL) {
+ fido_log_debug("%s: es256_pk_to_EVP_PKEY", __func__);
+ explicit_bzero(pk, sizeof(*pk));
+ return (FIDO_ERR_INVALID_ARGUMENT);
+ }
+
+ EVP_PKEY_free(pkey);
+
+ 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;
+ 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, es256_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;
+ 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(es256_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;
+ EC_GROUP *g = NULL;
+ size_t dx;
+ size_t dy;
+ int ok = FIDO_ERR_INTERNAL;
+ int nx;
+ int ny;
+
+ if ((q = EC_KEY_get0_public_key(ec)) == NULL ||
+ (g = EC_GROUP_new_by_curve_name(es256_nid)) == 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_is_on_curve(g, q, bnctx) != 1) {
+ fido_log_debug("%s: EC_POINT_is_on_curve", __func__);
+ ok = FIDO_ERR_INVALID_ARGUMENT;
+ goto fail;
+ }
+
+ if (EC_POINT_get_affine_coordinates_GFp(g, q, x, y, bnctx) == 0 ||
+ (nx = BN_num_bytes(x)) < 0 || (size_t)nx > sizeof(pk->x) ||
+ (ny = BN_num_bytes(y)) < 0 || (size_t)ny > sizeof(pk->y)) {
+ fido_log_debug("%s: EC_POINT_get_affine_coordinates_GFp",
+ __func__);
+ goto fail;
+ }
+
+ dx = sizeof(pk->x) - (size_t)nx;
+ dy = sizeof(pk->y) - (size_t)ny;
+
+ if ((nx = BN_bn2bin(x, pk->x + dx)) < 0 || (size_t)nx > sizeof(pk->x) ||
+ (ny = BN_bn2bin(y, pk->y + dy)) < 0 || (size_t)ny > sizeof(pk->y)) {
+ fido_log_debug("%s: BN_bn2bin", __func__);
+ goto fail;
+ }
+
+ ok = FIDO_OK;
+fail:
+ EC_GROUP_free(g);
+
+ if (bnctx != NULL) {
+ BN_CTX_end(bnctx);
+ BN_CTX_free(bnctx);
+ }
+
+ return (ok);
+}
+
+int
+es256_pk_from_EVP_PKEY(es256_pk_t *pk, const EVP_PKEY *pkey)
+{
+ const EC_KEY *ec;
+
+ if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC ||
+ (ec = get0_EC_KEY(pkey)) == NULL)
+ return (FIDO_ERR_INVALID_ARGUMENT);
+
+ return (es256_pk_from_EC_KEY(pk, ec));
+}
+
+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;
+ 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(es256_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;
+ int ok = -1;
+
+ if ((d = BN_bin2bn(sk->d, (int)sizeof(sk->d), NULL)) == NULL ||
+ (ec = EC_KEY_new_by_curve_name(es256_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);
+}
+
+int
+es256_verify_sig(const fido_blob_t *dgst, EVP_PKEY *pkey,
+ const fido_blob_t *sig)
+{
+ EVP_PKEY_CTX *pctx = NULL;
+ int ok = -1;
+
+ if (EVP_PKEY_base_id(pkey) != EVP_PKEY_EC) {
+ fido_log_debug("%s: EVP_PKEY_base_id", __func__);
+ goto fail;
+ }
+
+ if ((pctx = EVP_PKEY_CTX_new(pkey, NULL)) == NULL ||
+ EVP_PKEY_verify_init(pctx) != 1 ||
+ EVP_PKEY_verify(pctx, sig->ptr, sig->len, dgst->ptr,
+ dgst->len) != 1) {
+ fido_log_debug("%s: EVP_PKEY_verify", __func__);
+ goto fail;
+ }
+
+ ok = 0;
+fail:
+ EVP_PKEY_CTX_free(pctx);
+
+ return (ok);
+}
+
+int
+es256_pk_verify_sig(const fido_blob_t *dgst, const es256_pk_t *pk,
+ const fido_blob_t *sig)
+{
+ EVP_PKEY *pkey;
+ int ok = -1;
+
+ if ((pkey = es256_pk_to_EVP_PKEY(pk)) == NULL ||
+ es256_verify_sig(dgst, pkey, sig) < 0) {
+ fido_log_debug("%s: es256_verify_sig", __func__);
+ goto fail;
+ }
+
+ ok = 0;
+fail:
+ EVP_PKEY_free(pkey);
+
+ return (ok);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-08 11:19:44 +0000