328 lines
9.5 KiB
C
328 lines
9.5 KiB
C
/*
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* Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <string.h>
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#include <openssl/err.h>
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#include <openssl/rand.h>
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#include "ec_lcl.h"
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/* Length of Curve 25519 keys */
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#define EC_X25519_KEYLEN 32
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/* Group degree and order bits */
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#define EC_X25519_BITS 253
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/* Copy Curve25519 public key buffer, allocating is necessary */
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static int x25519_init_public(EC_POINT *pub, const void *src)
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{
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if (pub->custom_data == NULL) {
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pub->custom_data = OPENSSL_malloc(EC_X25519_KEYLEN);
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if (pub->custom_data == NULL)
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return 0;
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}
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if (src != NULL)
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memcpy(pub->custom_data, src, EC_X25519_KEYLEN);
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return 1;
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}
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/* Copy Curve25519 private key buffer, allocating is necessary */
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static int x25519_init_private(EC_KEY *dst, const void *src)
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{
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if (dst->custom_data == NULL) {
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dst->custom_data = OPENSSL_secure_malloc(EC_X25519_KEYLEN);
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if (dst->custom_data == NULL)
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return 0;
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}
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if (src != NULL)
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memcpy(dst->custom_data, src, EC_X25519_KEYLEN);
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return 1;
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}
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static int x25519_group_init(EC_GROUP *grp)
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{
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return 1;
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}
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static int x25519_group_copy(EC_GROUP *dst, const EC_GROUP *src)
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{
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return 1;
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}
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static int x25519_group_get_degree(const EC_GROUP *src)
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{
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return EC_X25519_BITS;
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}
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static int x25519_group_order_bits(const EC_GROUP *src)
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{
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return EC_X25519_BITS;
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}
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static int x25519_set_private(EC_KEY *eckey, const BIGNUM *priv_key)
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{
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if (BN_num_bytes(priv_key) > EC_X25519_KEYLEN)
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return 0;
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if (x25519_init_private(eckey, NULL))
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return 0;
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/* Convert BIGNUM form private key to internal format */
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if (BN_bn2lebinpad(priv_key, eckey->custom_data, EC_X25519_KEYLEN)
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!= EC_X25519_KEYLEN)
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return 0;
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return 1;
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}
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static int x25519_keycheck(const EC_KEY *eckey)
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{
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const char *pubkey;
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if (eckey->pub_key == NULL)
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return 0;
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pubkey = eckey->pub_key->custom_data;
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if (pubkey == NULL)
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return 0;
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if (eckey->custom_data != NULL) {
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uint8_t tmp[EC_X25519_KEYLEN];
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/* Check eckey->priv_key exists and matches eckey->custom_data */
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if (eckey->priv_key == NULL)
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return 0;
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if (BN_bn2lebinpad(eckey->priv_key, tmp, EC_X25519_KEYLEN)
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!= EC_X25519_KEYLEN
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|| CRYPTO_memcmp(tmp, eckey->custom_data,
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EC_X25519_KEYLEN) != 0) {
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OPENSSL_cleanse(tmp, EC_X25519_KEYLEN);
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return 0;
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}
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X25519_public_from_private(tmp, eckey->custom_data);
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if (CRYPTO_memcmp(pubkey, tmp, EC_X25519_KEYLEN) == 0)
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return 1;
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return 0;
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} else {
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return 1;
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}
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}
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static int x25519_keygenpub(EC_KEY *eckey)
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{
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X25519_public_from_private(eckey->pub_key->custom_data,
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eckey->custom_data);
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return 1;
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}
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static int x25519_keygen(EC_KEY *eckey)
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{
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unsigned char *key;
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if (x25519_init_private(eckey, NULL) == 0)
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return 0;
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key = eckey->custom_data;
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if (RAND_bytes(key, EC_X25519_KEYLEN) <= 0)
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return 0;
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key[0] &= 248;
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key[31] &= 127;
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key[31] |= 64;
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/*
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* Although the private key is kept as an array in eckey->custom_data
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* Set eckey->priv_key too so existing code which uses
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* EC_KEY_get0_private_key() still works.
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*/
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if (eckey->priv_key == NULL)
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eckey->priv_key = BN_secure_new();
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if (eckey->priv_key == NULL)
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return 0;
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if (BN_lebin2bn(eckey->custom_data, EC_X25519_KEYLEN, eckey->priv_key) ==
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NULL)
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return 0;
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if (eckey->pub_key == NULL)
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eckey->pub_key = EC_POINT_new(eckey->group);
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if (eckey->pub_key == NULL)
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return 0;
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return x25519_keygenpub(eckey);
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}
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static void x25519_keyfinish(EC_KEY *eckey)
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{
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OPENSSL_secure_free(eckey->custom_data);
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eckey->custom_data = NULL;
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}
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static int x25519_keycopy(EC_KEY *dest, const EC_KEY *src)
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{
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if (src->custom_data == NULL)
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return 0;
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return x25519_init_private(dest, src->custom_data);
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}
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static int x25519_oct2priv(EC_KEY *eckey, unsigned char *buf, size_t len)
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{
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if (len != EC_X25519_KEYLEN)
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return 0;
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if (x25519_init_private(eckey, buf) == 0)
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return 0;
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/*
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* Although the private key is kept as an array in eckey->custom_data
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* Set eckey->priv_key too so existing code which uses
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* EC_KEY_get0_private_key() still works.
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*/
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if (eckey->priv_key == NULL)
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eckey->priv_key = BN_secure_new();
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if (eckey->priv_key == NULL)
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return 0;
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if (BN_lebin2bn(buf, EC_X25519_KEYLEN, eckey->priv_key) == NULL)
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return 0;
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return 1;
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}
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static size_t x25519_priv2oct(const EC_KEY *eckey,
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unsigned char *buf, size_t len)
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{
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size_t keylen = EC_X25519_KEYLEN;
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if (eckey->custom_data == NULL)
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return 0;
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if (buf != NULL) {
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if (len < keylen)
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return 0;
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memcpy(buf, eckey->custom_data, keylen);
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}
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return keylen;
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}
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static int x25519_point_init(EC_POINT *pt)
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{
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return x25519_init_public(pt, NULL);
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}
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static void x25519_point_finish(EC_POINT *pt)
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{
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OPENSSL_free(pt->custom_data);
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pt->custom_data = NULL;
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}
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static void x25519_point_clear_finish(EC_POINT *pt)
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{
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OPENSSL_clear_free(pt->custom_data, EC_X25519_KEYLEN);
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pt->custom_data = NULL;
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}
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static int x25519_point_copy(EC_POINT *dst, const EC_POINT *src)
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{
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memcpy(dst->custom_data, src->custom_data, EC_X25519_KEYLEN);
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return 1;
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}
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static size_t x25519_point2oct(const EC_GROUP *grp, const EC_POINT *pt,
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point_conversion_form_t form,
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unsigned char *buf, size_t len, BN_CTX *ctx)
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{
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if (buf != NULL) {
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if (len < EC_X25519_KEYLEN)
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return 0;
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memcpy(buf, pt->custom_data, EC_X25519_KEYLEN);
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}
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return EC_X25519_KEYLEN;
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}
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static int x25519_oct2point(const EC_GROUP *grp, EC_POINT *pt,
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const unsigned char *buf, size_t len, BN_CTX *ctx)
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{
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unsigned char *pubkey = pt->custom_data;
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if (len != EC_X25519_KEYLEN)
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return 0;
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memcpy(pubkey, buf, EC_X25519_KEYLEN);
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/* Mask off MSB */
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pubkey[EC_X25519_KEYLEN - 1] &= 0x7F;
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return 1;
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}
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static int x25519_point_cmp(const EC_GROUP *group, const EC_POINT *a,
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const EC_POINT *b, BN_CTX *ctx)
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{
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/* Shouldn't happen as initialised to non-zero */
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if (a->custom_data == NULL || b->custom_data == NULL)
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return -1;
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if (CRYPTO_memcmp(a->custom_data, b->custom_data, EC_X25519_KEYLEN) == 0)
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return 0;
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return 1;
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}
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static int x25519_compute_key(unsigned char **psec, size_t *pseclen,
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const EC_POINT *pub_key, const EC_KEY *ecdh)
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{
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unsigned char *key;
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int ret = -1;
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if (ecdh->custom_data == NULL)
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return -1;
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key = OPENSSL_malloc(EC_X25519_KEYLEN);
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if (key == NULL)
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return 0;
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if (X25519(key, ecdh->custom_data, pub_key->custom_data) == 0)
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goto err;
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*psec = key;
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*pseclen = EC_X25519_KEYLEN;
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return 1;
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err:
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OPENSSL_clear_free(key, EC_X25519_KEYLEN);
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return ret;
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}
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const EC_METHOD *ec_x25519_meth(void)
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{
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static const EC_METHOD ret = {
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EC_FLAGS_CUSTOM_CURVE | EC_FLAGS_NO_SIGN,
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NID_undef,
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x25519_group_init, /* group_init */
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0, /* group_finish */
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0, /* group_clear_finish */
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x25519_group_copy, /* group_copy */
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0, /* group_set_curve */
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0, /* group_get_curve */
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x25519_group_get_degree,
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x25519_group_order_bits,
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0, /* group_check_discriminant */
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x25519_point_init,
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x25519_point_finish,
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x25519_point_clear_finish,
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x25519_point_copy,
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0, /* point_set_to_infinity */
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0, /* set_Jprojective_coordinates_GFp */
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0, /* get_Jprojective_coordinates_GFp */
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0, /* point_set_affine_coordinates */
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0, /* point_get_affine_coordinates */
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0, /* point_set_compressed_coordinates */
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x25519_point2oct,
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x25519_oct2point,
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0, /* simple_add */
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0, /* simple_dbl */
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0, /* simple_invert */
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0, /* simple_is_at_infinity */
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0, /* simple_is_on_curve */
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x25519_point_cmp,
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0, /* simple_make_affine */
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0, /* simple_points_make_affine */
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0, /* points_mul */
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0, /* precompute_mult */
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0, /* have_precompute_mult */
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0, /* field_mul */
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0, /* field_sqr */
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0, /* field_div */
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0, /* field_encode */
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0, /* field_decode */
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0, /* field_set_to_one */
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x25519_priv2oct,
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x25519_oct2priv,
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x25519_set_private,
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x25519_keygen,
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x25519_keycheck,
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x25519_keygenpub,
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x25519_keycopy,
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x25519_keyfinish,
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x25519_compute_key
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};
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return &ret;
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}
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