/*
* Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdlib.h>
#include "ssl_locl.h"
#include <openssl/evp.h>
#include <openssl/kdf.h>
#define TLS13_MAX_LABEL_LEN 246
/* Always filled with zeros */
static const unsigned char default_zeros[EVP_MAX_MD_SIZE];
static const unsigned char keylabel[] = "key";
static const unsigned char ivlabel[] = "iv";
/*
* Given a |secret|; a |label| of length |labellen|; and a |hash| of the
* handshake messages, derive a new secret |outlen| bytes long and store it in
* the location pointed to be |out|. The |hash| value may be NULL.
*
* Returns 1 on success 0 on failure.
*/
static int tls13_hkdf_expand(SSL *s, const unsigned char *secret,
const unsigned char *label, size_t labellen,
const unsigned char *hash,
unsigned char *out, size_t outlen)
{
const unsigned char label_prefix[] = "TLS 1.3, ";
const EVP_MD *md = ssl_handshake_md(s);
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
int ret;
size_t hkdflabellen;
size_t hashlen;
/*
* 2 bytes for length of whole HkdfLabel + 1 byte for length of combined
* prefix and label + bytes for the label itself + bytes for the hash
*/
unsigned char hkdflabel[sizeof(uint16_t) + sizeof(uint8_t) +
+ sizeof(label_prefix) + TLS13_MAX_LABEL_LEN
+ EVP_MAX_MD_SIZE];
WPACKET pkt;
if (pctx == NULL)
return 0;
hashlen = EVP_MD_size(md);
if (!WPACKET_init_static_len(&pkt, hkdflabel, sizeof(hkdflabel), 0)
|| !WPACKET_put_bytes_u16(&pkt, outlen)
|| !WPACKET_start_sub_packet_u8(&pkt)
|| !WPACKET_memcpy(&pkt, label_prefix, sizeof(label_prefix) - 1)
|| !WPACKET_memcpy(&pkt, label, labellen)
|| !WPACKET_close(&pkt)
|| !WPACKET_sub_memcpy_u8(&pkt, hash, (hash == NULL) ? 0 : hashlen)
|| !WPACKET_get_total_written(&pkt, &hkdflabellen)
|| !WPACKET_finish(&pkt)) {
WPACKET_cleanup(&pkt);
return 0;
}
ret = EVP_PKEY_derive_init(pctx) <= 0
|| EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXPAND_ONLY)
<= 0
|| EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
|| EVP_PKEY_CTX_set1_hkdf_key(pctx, secret, hashlen) <= 0
|| EVP_PKEY_CTX_add1_hkdf_info(pctx, hkdflabel, hkdflabellen) <= 0
|| EVP_PKEY_derive(pctx, out, &outlen) <= 0;
EVP_PKEY_CTX_free(pctx);
return ret == 0;
}
/*
* Given a input secret |insecret| and a |label| of length |labellen|, derive a
* new |secret|. This will be the length of the current hash output size and
* will be based on the current state of the handshake hashes.
*
* Returns 1 on success 0 on failure.
*/
int tls13_derive_secret(SSL *s, const unsigned char *insecret,
const unsigned char *label, size_t labellen,
unsigned char *secret)
{
unsigned char hash[EVP_MAX_MD_SIZE];
size_t hashlen;
if (!ssl3_digest_cached_records(s, 1))
return 0;
if (!ssl_handshake_hash(s, hash, sizeof(hash), &hashlen))
return 0;
return tls13_hkdf_expand(s, insecret, label, labellen, hash, secret,
hashlen);
}
/*
* Given a |secret| generate a |key| of length |keylen| bytes.
*
* Returns 1 on success 0 on failure.
*/
int tls13_derive_key(SSL *s, const unsigned char *secret, unsigned char *key,
size_t keylen)
{
return tls13_hkdf_expand(s, secret, keylabel, sizeof(keylabel) - 1, NULL,
key, keylen);
}
/*
* Given a |secret| generate an |iv| of length |ivlen| bytes.
*
* Returns 1 on success 0 on failure.
*/
int tls13_derive_iv(SSL *s, const unsigned char *secret, unsigned char *iv,
size_t ivlen)
{
return tls13_hkdf_expand(s, secret, ivlabel, sizeof(ivlabel) - 1, NULL,
iv, ivlen);
}
/*
* Given the previous secret |prevsecret| and a new input secret |insecret| of
* length |insecretlen|, generate a new secret and store it in the location
* pointed to by |outsecret|.
*
* Returns 1 on success 0 on failure.
*/
static int tls13_generate_secret(SSL *s, const unsigned char *prevsecret,
const unsigned char *insecret,
size_t insecretlen,
unsigned char *outsecret)
{
const EVP_MD *md = ssl_handshake_md(s);
size_t mdlen, prevsecretlen;
int ret;
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
if (pctx == NULL)
return 0;
mdlen = EVP_MD_size(md);
if (insecret == NULL) {
insecret = default_zeros;
insecretlen = mdlen;
}
if (prevsecret == NULL) {
prevsecret = default_zeros;
prevsecretlen = 0;
} else {
prevsecretlen = mdlen;
}
ret = EVP_PKEY_derive_init(pctx) <= 0
|| EVP_PKEY_CTX_hkdf_mode(pctx, EVP_PKEY_HKDEF_MODE_EXTRACT_ONLY)
<= 0
|| EVP_PKEY_CTX_set_hkdf_md(pctx, md) <= 0
|| EVP_PKEY_CTX_set1_hkdf_key(pctx, insecret, insecretlen) <= 0
|| EVP_PKEY_CTX_set1_hkdf_salt(pctx, prevsecret, prevsecretlen)
<= 0
|| EVP_PKEY_derive(pctx, outsecret, &mdlen)
<= 0;
EVP_PKEY_CTX_free(pctx);
return ret == 0;
}
/*
* Given an input secret |insecret| of length |insecretlen| generate the early
* secret.
*
* Returns 1 on success 0 on failure.
*/
int tls13_generate_early_secret(SSL *s, const unsigned char *insecret,
size_t insecretlen)
{
return tls13_generate_secret(s, NULL, insecret, insecretlen,
(unsigned char *)&s->early_secret);
}
/*
* Given an input secret |insecret| of length |insecretlen| generate the
* handshake secret. This requires the early secret to already have been
* generated.
*
* Returns 1 on success 0 on failure.
*/
int tls13_generate_handshake_secret(SSL *s, const unsigned char *insecret,
size_t insecretlen)
{
return tls13_generate_secret(s, s->early_secret, insecret, insecretlen,
(unsigned char *)&s->handshake_secret);
}
/*
* Given the handshake secret |prev| of length |prevlen| generate the master
* secret and store its length in |*secret_size|
*
* Returns 1 on success 0 on failure.
*/
int tls13_generate_master_secret(SSL *s, unsigned char *out,
unsigned char *prev, size_t prevlen,
size_t *secret_size)
{
*secret_size = EVP_MD_size(ssl_handshake_md(s));
return tls13_generate_secret(s, prev, NULL, 0, out);
}