1 files changed, 434 insertions, 0 deletions

diff --git a/src/es256.c b/src/es256.c
new file mode 100644
index 0000000..c8fd9f4
--- /dev/null
+++ b/src/es256.c
@@ -0,0 +1,434 @@
+/*
+ * 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/ec.h>
+#include <openssl/evp.h>
+#include <openssl/obj_mac.h>
+
+#include <string.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(-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;
+
+        explicit_bzero(sk, sizeof(*sk));
+        free(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;
+
+        explicit_bzero(pk, sizeof(*pk));
+        free(pk);
+
+        *pkp = NULL;
+}
+
+int
+es256_pk_from_ptr(es256_pk_t *pk, const void *ptr, size_t len)
+{
+        if (len < sizeof(*pk))
+                return (FIDO_ERR_INVALID_ARGUMENT);
+
+        memcpy(pk, ptr, sizeof(*pk));
+
+        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 ||
+            (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_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          *ctx = 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)
+                goto fail;
+
+        if ((ctx = BN_CTX_new()) == NULL ||
+            (x = BN_CTX_get(ctx)) == NULL ||
+            (y = BN_CTX_get(ctx)) == NULL)
+                goto fail;
+
+        if (EC_POINT_get_affine_coordinates_GFp(g, q, x, y, ctx) == 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 (ctx != NULL)
+                BN_CTX_free(ctx);
+
+        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 || (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_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);
+}