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/* $OpenBSD: tls12_key_schedule.c,v 1.1 2021/05/05 10:05:27 jsing Exp $ */
/*
* Copyright (c) 2021 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/evp.h>
#include "bytestring.h"
#include "ssl_locl.h"
struct tls12_key_block {
CBS client_write_mac_key;
CBS server_write_mac_key;
CBS client_write_key;
CBS server_write_key;
CBS client_write_iv;
CBS server_write_iv;
uint8_t *key_block;
size_t key_block_len;
};
struct tls12_key_block *
tls12_key_block_new(void)
{
return calloc(1, sizeof(struct tls12_key_block));
}
static void
tls12_key_block_clear(struct tls12_key_block *kb)
{
CBS_init(&kb->client_write_mac_key, NULL, 0);
CBS_init(&kb->server_write_mac_key, NULL, 0);
CBS_init(&kb->client_write_key, NULL, 0);
CBS_init(&kb->server_write_key, NULL, 0);
CBS_init(&kb->client_write_iv, NULL, 0);
CBS_init(&kb->server_write_iv, NULL, 0);
freezero(kb->key_block, kb->key_block_len);
kb->key_block = NULL;
kb->key_block_len = 0;
}
void
tls12_key_block_free(struct tls12_key_block *kb)
{
if (kb == NULL)
return;
tls12_key_block_clear(kb);
freezero(kb, sizeof(struct tls12_key_block));
}
void
tls12_key_block_client_write(struct tls12_key_block *kb, CBS *mac_key,
CBS *key, CBS *iv)
{
CBS_dup(&kb->client_write_mac_key, mac_key);
CBS_dup(&kb->client_write_key, key);
CBS_dup(&kb->client_write_iv, iv);
}
void
tls12_key_block_server_write(struct tls12_key_block *kb, CBS *mac_key,
CBS *key, CBS *iv)
{
CBS_dup(&kb->server_write_mac_key, mac_key);
CBS_dup(&kb->server_write_key, key);
CBS_dup(&kb->server_write_iv, iv);
}
int
tls12_key_block_generate(struct tls12_key_block *kb, SSL *s,
const EVP_AEAD *aead, const EVP_CIPHER *cipher, const EVP_MD *mac_hash)
{
size_t mac_key_len = 0, key_len = 0, iv_len = 0;
uint8_t *key_block = NULL;
size_t key_block_len = 0;
CBS cbs;
/*
* Generate a TLSv1.2 key block and partition into individual secrets,
* as per RFC 5246 section 6.3.
*/
tls12_key_block_clear(kb);
/* Must have AEAD or cipher/MAC pair. */
if (aead == NULL && (cipher == NULL || mac_hash == NULL))
goto err;
if (aead != NULL) {
key_len = EVP_AEAD_key_length(aead);
/* AEAD fixed nonce length. */
if (aead == EVP_aead_aes_128_gcm() ||
aead == EVP_aead_aes_256_gcm())
iv_len = 4;
else if (aead == EVP_aead_chacha20_poly1305())
iv_len = 12;
else
goto err;
} else if (cipher != NULL && mac_hash != NULL) {
/*
* A negative integer return value will be detected via the
* EVP_MAX_* checks against the size_t variables below.
*/
mac_key_len = EVP_MD_size(mac_hash);
key_len = EVP_CIPHER_key_length(cipher);
iv_len = EVP_CIPHER_iv_length(cipher);
/* Special handling for GOST... */
if (EVP_MD_type(mac_hash) == NID_id_Gost28147_89_MAC)
mac_key_len = 32;
}
if (mac_key_len > EVP_MAX_MD_SIZE)
goto err;
if (key_len > EVP_MAX_KEY_LENGTH)
goto err;
if (iv_len > EVP_MAX_IV_LENGTH)
goto err;
key_block_len = 2 * mac_key_len + 2 * key_len + 2 * iv_len;
if ((key_block = calloc(1, key_block_len)) == NULL)
goto err;
if (!tls1_generate_key_block(s, key_block, key_block_len))
goto err;
kb->key_block = key_block;
kb->key_block_len = key_block_len;
key_block = NULL;
key_block_len = 0;
/* Partition key block into individual secrets. */
CBS_init(&cbs, kb->key_block, kb->key_block_len);
if (!CBS_get_bytes(&cbs, &kb->client_write_mac_key, mac_key_len))
goto err;
if (!CBS_get_bytes(&cbs, &kb->server_write_mac_key, mac_key_len))
goto err;
if (!CBS_get_bytes(&cbs, &kb->client_write_key, key_len))
goto err;
if (!CBS_get_bytes(&cbs, &kb->server_write_key, key_len))
goto err;
if (!CBS_get_bytes(&cbs, &kb->client_write_iv, iv_len))
goto err;
if (!CBS_get_bytes(&cbs, &kb->server_write_iv, iv_len))
goto err;
if (CBS_len(&cbs) != 0)
goto err;
return 1;
err:
tls12_key_block_clear(kb);
freezero(key_block, key_block_len);
return 0;
}
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