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/* $OpenBSD: tls13_key_share.c,v 1.6 2020/04/18 14:07:56 jsing Exp $ */
/*
* Copyright (c) 2020 Joel Sing <jsing@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdlib.h>
#include <openssl/curve25519.h>
#include "bytestring.h"
#include "ssl_locl.h"
#include "tls13_internal.h"
struct tls13_key_share {
int nid;
uint16_t group_id;
EC_KEY *ecdhe;
EC_KEY *ecdhe_peer;
uint8_t *x25519_public;
uint8_t *x25519_private;
uint8_t *x25519_peer_public;
};
struct tls13_key_share *
tls13_key_share_new(uint16_t group_id)
{
struct tls13_key_share *ks;
int nid;
if ((nid = tls1_ec_curve_id2nid(group_id)) == 0)
return NULL;
if ((ks = calloc(1, sizeof(struct tls13_key_share))) == NULL)
return NULL;
ks->group_id = group_id;
ks->nid = nid;
return ks;
}
struct tls13_key_share *
tls13_key_share_new_nid(int nid)
{
uint16_t group_id;
if ((group_id = tls1_ec_nid2curve_id(nid)) == 0)
return NULL;
return tls13_key_share_new(group_id);
}
void
tls13_key_share_free(struct tls13_key_share *ks)
{
if (ks == NULL)
return;
EC_KEY_free(ks->ecdhe);
EC_KEY_free(ks->ecdhe_peer);
freezero(ks->x25519_public, X25519_KEY_LENGTH);
freezero(ks->x25519_private, X25519_KEY_LENGTH);
freezero(ks->x25519_peer_public, X25519_KEY_LENGTH);
freezero(ks, sizeof(*ks));
}
uint16_t
tls13_key_share_group(struct tls13_key_share *ks)
{
return ks->group_id;
}
int
tls13_key_share_peer_pkey(struct tls13_key_share *ks, EVP_PKEY *pkey)
{
if (ks->nid == NID_X25519 && ks->x25519_peer_public != NULL) {
if (!ssl_kex_dummy_ecdhe_x25519(pkey))
return 0;
} else if (ks->ecdhe_peer != NULL) {
if (!EVP_PKEY_set1_EC_KEY(pkey, ks->ecdhe_peer))
return 0;
} else {
return 0;
}
return 1;
}
static int
tls13_key_share_generate_ecdhe_ecp(struct tls13_key_share *ks)
{
EC_KEY *ecdhe = NULL;
int ret = 0;
if (ks->ecdhe != NULL)
goto err;
if ((ecdhe = EC_KEY_new()) == NULL)
goto err;
if (!ssl_kex_generate_ecdhe_ecp(ecdhe, ks->nid))
goto err;
ks->ecdhe = ecdhe;
ecdhe = NULL;
ret = 1;
err:
EC_KEY_free(ecdhe);
return ret;
}
static int
tls13_key_share_generate_x25519(struct tls13_key_share *ks)
{
uint8_t *public = NULL, *private = NULL;
int ret = 0;
if (ks->x25519_public != NULL || ks->x25519_private != NULL)
goto err;
if ((public = calloc(1, X25519_KEY_LENGTH)) == NULL)
goto err;
if ((private = calloc(1, X25519_KEY_LENGTH)) == NULL)
goto err;
X25519_keypair(public, private);
ks->x25519_public = public;
ks->x25519_private = private;
public = NULL;
private = NULL;
ret = 1;
err:
freezero(public, X25519_KEY_LENGTH);
freezero(private, X25519_KEY_LENGTH);
return ret;
}
int
tls13_key_share_generate(struct tls13_key_share *ks)
{
if (ks->nid == NID_X25519)
return tls13_key_share_generate_x25519(ks);
return tls13_key_share_generate_ecdhe_ecp(ks);
}
static int
tls13_key_share_public_ecdhe_ecp(struct tls13_key_share *ks, CBB *cbb)
{
if (ks->ecdhe == NULL)
return 0;
return ssl_kex_public_ecdhe_ecp(ks->ecdhe, cbb);
}
static int
tls13_key_share_public_x25519(struct tls13_key_share *ks, CBB *cbb)
{
if (ks->x25519_public == NULL)
return 0;
return CBB_add_bytes(cbb, ks->x25519_public, X25519_KEY_LENGTH);
}
int
tls13_key_share_public(struct tls13_key_share *ks, CBB *cbb)
{
CBB key_exchange;
if (!CBB_add_u16(cbb, ks->group_id))
goto err;
if (!CBB_add_u16_length_prefixed(cbb, &key_exchange))
goto err;
if (ks->nid == NID_X25519) {
if (!tls13_key_share_public_x25519(ks, &key_exchange))
goto err;
} else {
if (!tls13_key_share_public_ecdhe_ecp(ks, &key_exchange))
goto err;
}
if (!CBB_flush(cbb))
goto err;
return 1;
err:
return 0;
}
static int
tls13_key_share_peer_public_ecdhe_ecp(struct tls13_key_share *ks, CBS *cbs)
{
EC_KEY *ecdhe = NULL;
int ret = 0;
if (ks->ecdhe_peer != NULL)
goto err;
if ((ecdhe = EC_KEY_new()) == NULL)
goto err;
if (!ssl_kex_peer_public_ecdhe_ecp(ecdhe, ks->nid, cbs))
goto err;
ks->ecdhe_peer = ecdhe;
ecdhe = NULL;
ret = 1;
err:
EC_KEY_free(ecdhe);
return ret;
}
static int
tls13_key_share_peer_public_x25519(struct tls13_key_share *ks, CBS *cbs)
{
size_t out_len;
if (ks->x25519_peer_public != NULL)
return 0;
if (CBS_len(cbs) != X25519_KEY_LENGTH)
return 0;
return CBS_stow(cbs, &ks->x25519_peer_public, &out_len);
}
int
tls13_key_share_peer_public(struct tls13_key_share *ks, uint16_t group,
CBS *cbs)
{
if (ks->group_id != group)
return 0;
if (ks->nid == NID_X25519) {
if (!tls13_key_share_peer_public_x25519(ks, cbs))
return 0;
} else {
if (!tls13_key_share_peer_public_ecdhe_ecp(ks, cbs))
return 0;
}
return 1;
}
static int
tls13_key_share_derive_ecdhe_ecp(struct tls13_key_share *ks,
uint8_t **shared_key, size_t *shared_key_len)
{
if (ks->ecdhe == NULL || ks->ecdhe_peer == NULL)
return 0;
return ssl_kex_derive_ecdhe_ecp(ks->ecdhe, ks->ecdhe_peer,
shared_key, shared_key_len);
}
static int
tls13_key_share_derive_x25519(struct tls13_key_share *ks,
uint8_t **shared_key, size_t *shared_key_len)
{
uint8_t *sk = NULL;
int ret = 0;
if (ks->x25519_private == NULL || ks->x25519_peer_public == NULL)
goto err;
if ((sk = calloc(1, X25519_KEY_LENGTH)) == NULL)
goto err;
if (!X25519(sk, ks->x25519_private, ks->x25519_peer_public))
goto err;
*shared_key = sk;
*shared_key_len = X25519_KEY_LENGTH;
sk = NULL;
ret = 1;
err:
freezero(sk, X25519_KEY_LENGTH);
return ret;
}
int
tls13_key_share_derive(struct tls13_key_share *ks, uint8_t **shared_key,
size_t *shared_key_len)
{
if (*shared_key != NULL)
return 0;
*shared_key_len = 0;
if (ks->nid == NID_X25519)
return tls13_key_share_derive_x25519(ks, shared_key,
shared_key_len);
return tls13_key_share_derive_ecdhe_ecp(ks, shared_key,
shared_key_len);
}
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