+/*
+ * Written by Dr Stephen N Henson (steve@openssl.org) for the OpenSSL
+ * project.
+ */
+/* ====================================================================
+ * Copyright (c) 2016 The OpenSSL Project. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ * software must display the following acknowledgment:
+ * "This product includes software developed by the OpenSSL Project
+ * for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ * endorse or promote products derived from this software without
+ * prior written permission. For written permission, please contact
+ * licensing@OpenSSL.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ * nor may "OpenSSL" appear in their names without prior written
+ * permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ * acknowledgment:
+ * "This product includes software developed by the OpenSSL Project
+ * for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ */
+
+#include <string.h>
+#include <openssl/err.h>
+#include <openssl/rand.h>
+#include "ec_lcl.h"
+
+/* Length of Curve 25519 keys */
+#define EC_X25519_KEYLEN 32
+/* Group degree and order bits */
+#define EC_X25519_BITS 253
+
+/* Copy Curve25519 public key buffer, allocating is necessary */
+static int x25519_init_public(EC_POINT *pub, const void *src)
+{
+ if (pub->custom_data == NULL) {
+ pub->custom_data = OPENSSL_malloc(EC_X25519_KEYLEN);
+ if (pub->custom_data == NULL)
+ return 0;
+ }
+ if (src != NULL)
+ memcpy(pub->custom_data, src, EC_X25519_KEYLEN);
+ return 1;
+}
+
+/* Copy Curve25519 private key buffer, allocating is necessary */
+static int x25519_init_private(EC_KEY *dst, const void *src)
+{
+ if (dst->custom_data == NULL) {
+ dst->custom_data = OPENSSL_secure_malloc(EC_X25519_KEYLEN);
+ if (dst->custom_data == NULL)
+ return 0;
+ }
+ if (src != NULL)
+ memcpy(dst->custom_data, src, EC_X25519_KEYLEN);
+ return 1;
+}
+
+static int x25519_group_init(EC_GROUP *grp)
+{
+ return 1;
+}
+
+static int x25519_group_copy(EC_GROUP *dst, const EC_GROUP *src)
+{
+ return 1;
+}
+
+static int x25519_group_get_degree(const EC_GROUP *src)
+{
+ return EC_X25519_BITS;
+}
+
+static int x25519_group_order_bits(const EC_GROUP *src)
+{
+ return EC_X25519_BITS;
+}
+
+static int x25519_set_private(EC_KEY *eckey, const BIGNUM *priv_key)
+{
+ if (BN_num_bytes(priv_key) > EC_X25519_KEYLEN)
+ return 0;
+ if (x25519_init_private(eckey, NULL))
+ return 0;
+ /* Convert BIGNUM form private key to internal format */
+ if (BN_bn2lebinpad(priv_key, eckey->custom_data, EC_X25519_KEYLEN)
+ != EC_X25519_KEYLEN)
+ return 0;
+ return 1;
+}
+
+static int x25519_keycheck(const EC_KEY *eckey)
+{
+ const char *pubkey;
+ if (eckey->pub_key == NULL)
+ return 0;
+ pubkey = eckey->pub_key->custom_data;
+ if (pubkey == NULL)
+ return 0;
+ if (eckey->custom_data != NULL) {
+ uint8_t tmp[EC_X25519_KEYLEN];
+ /* Check eckey->priv_key exists and matches eckey->custom_data */
+ if (eckey->priv_key == NULL)
+ return 0;
+ if (BN_bn2lebinpad(eckey->priv_key, tmp, EC_X25519_KEYLEN)
+ != EC_X25519_KEYLEN
+ || CRYPTO_memcmp(tmp, eckey->custom_data,
+ EC_X25519_KEYLEN) != 0) {
+ OPENSSL_cleanse(tmp, EC_X25519_KEYLEN);
+ return 0;
+ }
+ X25519_public_from_private(tmp, eckey->custom_data);
+ if (CRYPTO_memcmp(pubkey, tmp, EC_X25519_KEYLEN) == 0)
+ return 1;
+ return 0;
+ } else {
+ return 1;
+ }
+}
+
+static int x25519_keygenpub(EC_KEY *eckey)
+{
+ X25519_public_from_private(eckey->pub_key->custom_data,
+ eckey->custom_data);
+ return 1;
+}
+
+static int x25519_keygen(EC_KEY *eckey)
+{
+ unsigned char *key;
+ if (x25519_init_private(eckey, NULL) == 0)
+ return 0;
+ key = eckey->custom_data;
+ if (RAND_bytes(key, EC_X25519_KEYLEN) <= 0)
+ return 0;
+ key[0] &= 248;
+ key[31] &= 127;
+ key[31] |= 64;
+ /*
+ * Although the private key is kept as an array in eckey->custom_data
+ * Set eckey->priv_key too so existing code which uses
+ * EC_KEY_get0_private_key() still works.
+ */
+ if (eckey->priv_key == NULL)
+ eckey->priv_key = BN_secure_new();
+ if (eckey->priv_key == NULL)
+ return 0;
+ if (BN_lebin2bn(eckey->custom_data, EC_X25519_KEYLEN, eckey->priv_key) ==
+ NULL)
+ return 0;
+ if (eckey->pub_key == NULL)
+ eckey->pub_key = EC_POINT_new(eckey->group);
+ if (eckey->pub_key == NULL)
+ return 0;
+ return x25519_keygenpub(eckey);
+}
+
+static void x25519_keyfinish(EC_KEY *eckey)
+{
+ OPENSSL_secure_free(eckey->custom_data);
+ eckey->custom_data = NULL;
+}
+
+static int x25519_keycopy(EC_KEY *dest, const EC_KEY *src)
+{
+ if (src->custom_data == NULL)
+ return 0;
+ return x25519_init_private(dest, src->custom_data);
+}
+
+static int x25519_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len)
+{
+ if (len != EC_X25519_KEYLEN)
+ return 0;
+ if (x25519_init_private(eckey, buf) == 0)
+ return 0;
+ /*
+ * Although the private key is kept as an array in eckey->custom_data
+ * Set eckey->priv_key too so existing code which uses
+ * EC_KEY_get0_private_key() still works.
+ */
+ if (eckey->priv_key == NULL)
+ eckey->priv_key = BN_secure_new();
+ if (eckey->priv_key == NULL)
+ return 0;
+ if (BN_lebin2bn(buf, EC_X25519_KEYLEN, eckey->priv_key) == NULL)
+ return 0;
+ return 1;
+}
+
+static size_t x25519_priv2oct(const EC_KEY *eckey,
+ unsigned char *buf, size_t len)
+{
+ size_t keylen = EC_X25519_KEYLEN;
+ if (eckey->custom_data == NULL)
+ return 0;
+ if (buf != NULL) {
+ if (len < keylen)
+ return 0;
+ memcpy(buf, eckey->custom_data, keylen);
+ }
+ return keylen;
+}
+
+static int x25519_point_init(EC_POINT *pt)
+{
+ return x25519_init_public(pt, NULL);
+}
+
+static void x25519_point_finish(EC_POINT *pt)
+{
+ OPENSSL_free(pt->custom_data);
+ pt->custom_data = NULL;
+}
+
+static void x25519_point_clear_finish(EC_POINT *pt)
+{
+ OPENSSL_clear_free(pt->custom_data, EC_X25519_KEYLEN);
+ pt->custom_data = NULL;
+}
+
+static int x25519_point_copy(EC_POINT *dst, const EC_POINT *src)
+{
+ memcpy(dst->custom_data, src->custom_data, EC_X25519_KEYLEN);
+ return 1;
+}
+
+static size_t x25519_point2oct(const EC_GROUP *grp, const EC_POINT *pt,
+ point_conversion_form_t form,
+ unsigned char *buf, size_t len, BN_CTX *ctx)
+{
+ if (buf != NULL) {
+ if (len < EC_X25519_KEYLEN)
+ return 0;
+ memcpy(buf, pt->custom_data, EC_X25519_KEYLEN);
+ }
+ return EC_X25519_KEYLEN;
+}
+
+static int x25519_oct2point(const EC_GROUP *grp, EC_POINT *pt,
+ const unsigned char *buf, size_t len, BN_CTX *ctx)
+{
+ unsigned char *pubkey = pt->custom_data;
+ if (len != EC_X25519_KEYLEN)
+ return 0;
+ memcpy(pubkey, buf, EC_X25519_KEYLEN);
+ /* Mask off MSB */
+ pubkey[EC_X25519_KEYLEN - 1] &= 0x7F;
+ return 1;
+}
+
+static int x25519_point_cmp(const EC_GROUP *group, const EC_POINT *a,
+ const EC_POINT *b, BN_CTX *ctx)
+{
+ /* Shouldn't happen as initialised to non-zero */
+ if (a->custom_data == NULL || b->custom_data == NULL)
+ return -1;
+
+ if (CRYPTO_memcmp(a->custom_data, b->custom_data, EC_X25519_KEYLEN) == 0)
+ return 0;
+
+ return 1;
+}
+
+static int x25519_compute_key(void *out, size_t outlen,
+ const EC_POINT *pub_key, const EC_KEY *ecdh,
+ void *(*KDF) (const void *in, size_t inlen,
+ void *out, size_t *outlen))
+{
+ unsigned char *key;
+ int ret = -1;
+ if (ecdh->custom_data == NULL)
+ return -1;
+ key = OPENSSL_malloc(EC_X25519_KEYLEN);
+ if (key == NULL)
+ return -1;
+ if (X25519(key, ecdh->custom_data, pub_key->custom_data) == 0)
+ goto err;
+ if (KDF) {
+ if (KDF(key, EC_X25519_KEYLEN, out, &outlen) == NULL)
+ goto err;
+ ret = outlen;
+ } else {
+ if (outlen > EC_X25519_KEYLEN)
+ outlen = EC_X25519_KEYLEN;
+ memcpy(out, key, outlen);
+ ret = outlen;
+ }
+
+ err:
+ OPENSSL_clear_free(key, EC_X25519_KEYLEN);
+ return ret;
+}
+
+const EC_METHOD *ec_x25519_meth(void)
+{
+ static const EC_METHOD ret = {
+ EC_FLAGS_CUSTOM_CURVE,
+ NID_undef,
+ x25519_group_init, /* group_init */
+ 0, /* group_finish */
+ 0, /* group_clear_finish */
+ x25519_group_copy, /* group_copy */
+ 0, /* group_set_curve */
+ 0, /* group_get_curve */
+ x25519_group_get_degree,
+ x25519_group_order_bits,
+ 0, /* group_check_discriminant */
+ x25519_point_init,
+ x25519_point_finish,
+ x25519_point_clear_finish,
+ x25519_point_copy,
+ 0, /* point_set_to_infinity */
+ 0, /* set_Jprojective_coordinates_GFp */
+ 0, /* get_Jprojective_coordinates_GFp */
+ 0, /* point_set_affine_coordinates */
+ 0, /* point_get_affine_coordinates */
+ 0, /* point_set_compressed_coordinates */
+ x25519_point2oct,
+ x25519_oct2point,
+ 0, /* simple_add */
+ 0, /* simple_dbl */
+ 0, /* simple_invert */
+ 0, /* simple_is_at_infinity */
+ 0, /* simple_is_on_curve */
+ x25519_point_cmp,
+ 0, /* simple_make_affine */
+ 0, /* simple_points_make_affine */
+ 0, /* points_mul */
+ 0, /* precompute_mult */
+ 0, /* have_precompute_mult */
+ 0, /* field_mul */
+ 0, /* field_sqr */
+ 0, /* field_div */
+ 0, /* field_encode */
+ 0, /* field_decode */
+ 0, /* field_set_to_one */
+ x25519_priv2oct,
+ x25519_oct2priv,
+ x25519_set_private,
+ x25519_keygen,
+ x25519_keycheck,
+ x25519_keygenpub,
+ x25519_keycopy,
+ x25519_keyfinish,
+ x25519_compute_key
+ };
+
+ return &ret;
+}
projects / openssl.git / commitdiff