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openssl/ssl/tls13_enc.c
Matt Caswell 0871754499 Make sure we use the correct cipher when using the early_secret 
Reviewed-by: Ben Kaduk <kaduk@mit.edu>
(Merged from https://github.com/openssl/openssl/pull/3926)
2017-08-31 15:02:58 +01:00

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/*
* 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 "internal/cryptlib.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];
/*
* Given a |secret|; a |label| of length |labellen|; and |data| of length
* |datalen| (e.g. typically a hash of the handshake messages), derive a new
* secret |outlen| bytes long and store it in the location pointed to be |out|.
* The |data| value may be zero length. Returns 1 on success 0 on failure.
*/
int tls13_hkdf_expand(SSL *s, const EVP_MD *md, const unsigned char *secret,
const unsigned char *label, size_t labellen,
const unsigned char *data, size_t datalen,
unsigned char *out, size_t outlen)
{
const unsigned char label_prefix[] = "tls13 ";
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, data, (data == NULL) ? 0 : datalen)
|| !WPACKET_get_total_written(&pkt, &hkdflabellen)
|| !WPACKET_finish(&pkt)) {
EVP_PKEY_CTX_free(pctx);
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 |secret| generate a |key| of length |keylen| bytes. Returns 1 on
* success 0 on failure.
*/
int tls13_derive_key(SSL *s, const EVP_MD *md, const unsigned char *secret,
unsigned char *key, size_t keylen)
{
static const unsigned char keylabel[] = "key";
return tls13_hkdf_expand(s, md, secret, keylabel, sizeof(keylabel) - 1,
NULL, 0, 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 EVP_MD *md, const unsigned char *secret,
unsigned char *iv, size_t ivlen)
{
static const unsigned char ivlabel[] = "iv";
return tls13_hkdf_expand(s, md, secret, ivlabel, sizeof(ivlabel) - 1,
NULL, 0, iv, ivlen);
}
int tls13_derive_finishedkey(SSL *s, const EVP_MD *md,
const unsigned char *secret,
unsigned char *fin, size_t finlen)
{
static const unsigned char finishedlabel[] = "finished";
return tls13_hkdf_expand(s, md, secret, finishedlabel,
sizeof(finishedlabel) - 1, NULL, 0, fin, finlen);
}
/*
* 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.
*/
int tls13_generate_secret(SSL *s, const EVP_MD *md,
const unsigned char *prevsecret,
const unsigned char *insecret,
size_t insecretlen,
unsigned char *outsecret)
{
size_t mdlen, prevsecretlen;
int ret;
EVP_PKEY_CTX *pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_HKDF, NULL);
static const char derived_secret_label[] = "derived";
unsigned char preextractsec[EVP_MAX_MD_SIZE];
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 {
EVP_MD_CTX *mctx = EVP_MD_CTX_new();
unsigned char hash[EVP_MAX_MD_SIZE];
/* The pre-extract derive step uses a hash of no messages */
if (mctx == NULL
|| EVP_DigestInit_ex(mctx, md, NULL) <= 0
|| EVP_DigestFinal_ex(mctx, hash, NULL) <= 0) {
EVP_MD_CTX_free(mctx);
EVP_PKEY_CTX_free(pctx);
return 0;
}
EVP_MD_CTX_free(mctx);
/* Generate the pre-extract secret */
if (!tls13_hkdf_expand(s, md, prevsecret,
(unsigned char *)derived_secret_label,
sizeof(derived_secret_label) - 1, hash, mdlen,
preextractsec, mdlen)) {
EVP_PKEY_CTX_free(pctx);
return 0;
}
prevsecret = preextractsec;
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);
if (prevsecret == preextractsec)
OPENSSL_cleanse(preextractsec, mdlen);
return ret == 0;
}
/*
* 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, ssl_handshake_md(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)
{
const EVP_MD *md = ssl_handshake_md(s);
*secret_size = EVP_MD_size(md);
return tls13_generate_secret(s, md, prev, NULL, 0, out);
}
/*
* Generates the mac for the Finished message. Returns the length of the MAC or
* 0 on error.
*/
size_t tls13_final_finish_mac(SSL *s, const char *str, size_t slen,
unsigned char *out)
{
const EVP_MD *md = ssl_handshake_md(s);
unsigned char hash[EVP_MAX_MD_SIZE];
size_t hashlen, ret = 0;
EVP_PKEY *key = NULL;
EVP_MD_CTX *ctx = EVP_MD_CTX_new();
if (!ssl_handshake_hash(s, hash, sizeof(hash), &hashlen))
goto err;
if (str == s->method->ssl3_enc->server_finished_label)
key = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL,
s->server_finished_secret, hashlen);
else
key = EVP_PKEY_new_mac_key(EVP_PKEY_HMAC, NULL,
s->client_finished_secret, hashlen);
if (key == NULL
|| ctx == NULL
|| EVP_DigestSignInit(ctx, NULL, md, NULL, key) <= 0
|| EVP_DigestSignUpdate(ctx, hash, hashlen) <= 0
|| EVP_DigestSignFinal(ctx, out, &hashlen) <= 0)
goto err;
ret = hashlen;
err:
EVP_PKEY_free(key);
EVP_MD_CTX_free(ctx);
return ret;
}
/*
* There isn't really a key block in TLSv1.3, but we still need this function
* for initialising the cipher and hash. Returns 1 on success or 0 on failure.
*/
int tls13_setup_key_block(SSL *s)
{
const EVP_CIPHER *c;
const EVP_MD *hash;
int mac_type = NID_undef;
s->session->cipher = s->s3->tmp.new_cipher;
if (!ssl_cipher_get_evp
(s->session, &c, &hash, &mac_type, NULL, NULL, 0)) {
SSLerr(SSL_F_TLS13_SETUP_KEY_BLOCK, SSL_R_CIPHER_OR_HASH_UNAVAILABLE);
return 0;
}
s->s3->tmp.new_sym_enc = c;
s->s3->tmp.new_hash = hash;
return 1;
}
static int derive_secret_key_and_iv(SSL *s, int sending, const EVP_MD *md,
const EVP_CIPHER *ciph,
const unsigned char *insecret,
const unsigned char *hash,
const unsigned char *label,
size_t labellen, unsigned char *secret,
unsigned char *iv, EVP_CIPHER_CTX *ciph_ctx)
{
unsigned char key[EVP_MAX_KEY_LENGTH];
size_t ivlen, keylen, taglen;
size_t hashlen = EVP_MD_size(md);
if (!tls13_hkdf_expand(s, md, insecret, label, labellen, hash, hashlen,
secret, hashlen)) {
SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_INTERNAL_ERROR);
goto err;
}
/* TODO(size_t): convert me */
keylen = EVP_CIPHER_key_length(ciph);
if (EVP_CIPHER_mode(ciph) == EVP_CIPH_CCM_MODE) {
uint32_t algenc;
ivlen = EVP_CCM_TLS_IV_LEN;
if (s->s3->tmp.new_cipher == NULL) {
/* We've not selected a cipher yet - we must be doing early data */
algenc = s->session->cipher->algorithm_enc;
} else {
algenc = s->s3->tmp.new_cipher->algorithm_enc;
}
if (algenc & (SSL_AES128CCM8 | SSL_AES256CCM8))
taglen = EVP_CCM8_TLS_TAG_LEN;
else
taglen = EVP_CCM_TLS_TAG_LEN;
} else {
ivlen = EVP_CIPHER_iv_length(ciph);
taglen = 0;
}
if (!tls13_derive_key(s, md, secret, key, keylen)
|| !tls13_derive_iv(s, md, secret, iv, ivlen)) {
SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_INTERNAL_ERROR);
goto err;
}
if (EVP_CipherInit_ex(ciph_ctx, ciph, NULL, NULL, NULL, sending) <= 0
|| !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_IVLEN, ivlen, NULL)
|| (taglen != 0 && !EVP_CIPHER_CTX_ctrl(ciph_ctx, EVP_CTRL_AEAD_SET_TAG,
taglen, NULL))
|| EVP_CipherInit_ex(ciph_ctx, NULL, NULL, key, NULL, -1) <= 0) {
SSLerr(SSL_F_DERIVE_SECRET_KEY_AND_IV, ERR_R_EVP_LIB);
goto err;
}
return 1;
err:
OPENSSL_cleanse(key, sizeof(key));
return 0;
}
int tls13_change_cipher_state(SSL *s, int which)
{
static const unsigned char client_early_traffic[] = "c e traffic";
static const unsigned char client_handshake_traffic[] = "c hs traffic";
static const unsigned char client_application_traffic[] = "c ap traffic";
static const unsigned char server_handshake_traffic[] = "s hs traffic";
static const unsigned char server_application_traffic[] = "s ap traffic";
static const unsigned char exporter_master_secret[] = "exp master";
static const unsigned char resumption_master_secret[] = "res master";
unsigned char *iv;
unsigned char secret[EVP_MAX_MD_SIZE];
unsigned char hashval[EVP_MAX_MD_SIZE];
unsigned char *hash = hashval;
unsigned char *insecret;
unsigned char *finsecret = NULL;
const char *log_label = NULL;
EVP_CIPHER_CTX *ciph_ctx;
size_t finsecretlen = 0;
const unsigned char *label;
size_t labellen, hashlen = 0;
int ret = 0;
const EVP_MD *md = NULL;
const EVP_CIPHER *cipher = NULL;
if (which & SSL3_CC_READ) {
if (s->enc_read_ctx != NULL) {
EVP_CIPHER_CTX_reset(s->enc_read_ctx);
} else {
s->enc_read_ctx = EVP_CIPHER_CTX_new();
if (s->enc_read_ctx == NULL) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
goto err;
}
}
ciph_ctx = s->enc_read_ctx;
iv = s->read_iv;
RECORD_LAYER_reset_read_sequence(&s->rlayer);
} else {
if (s->enc_write_ctx != NULL) {
EVP_CIPHER_CTX_reset(s->enc_write_ctx);
} else {
s->enc_write_ctx = EVP_CIPHER_CTX_new();
if (s->enc_write_ctx == NULL) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
goto err;
}
}
ciph_ctx = s->enc_write_ctx;
iv = s->write_iv;
RECORD_LAYER_reset_write_sequence(&s->rlayer);
}
if (((which & SSL3_CC_CLIENT) && (which & SSL3_CC_WRITE))
|| ((which & SSL3_CC_SERVER) && (which & SSL3_CC_READ))) {
if (which & SSL3_CC_EARLY) {
EVP_MD_CTX *mdctx = NULL;
long handlen;
void *hdata;
unsigned int hashlenui;
const SSL_CIPHER *sslcipher = SSL_SESSION_get0_cipher(s->session);
insecret = s->early_secret;
label = client_early_traffic;
labellen = sizeof(client_early_traffic) - 1;
log_label = CLIENT_EARLY_LABEL;
handlen = BIO_get_mem_data(s->s3->handshake_buffer, &hdata);
if (handlen <= 0) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE,
SSL_R_BAD_HANDSHAKE_LENGTH);
goto err;
}
if (s->early_data_state == SSL_EARLY_DATA_CONNECTING
&& s->max_early_data > 0
&& s->session->ext.max_early_data == 0) {
/*
* If we are attempting to send early data, and we've decided to
* actually do it but max_early_data in s->session is 0 then we
* must be using an external PSK.
*/
if (!ossl_assert(s->psksession != NULL
&& s->max_early_data ==
s->psksession->ext.max_early_data)) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE,
ERR_R_INTERNAL_ERROR);
goto err;
}
sslcipher = SSL_SESSION_get0_cipher(s->psksession);
}
if (sslcipher == NULL) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, SSL_R_BAD_PSK);
goto err;
}
/*
* We need to calculate the handshake digest using the digest from
* the session. We haven't yet selected our ciphersuite so we can't
* use ssl_handshake_md().
*/
mdctx = EVP_MD_CTX_new();
if (mdctx == NULL) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_MALLOC_FAILURE);
goto err;
}
cipher = EVP_get_cipherbynid(SSL_CIPHER_get_cipher_nid(sslcipher));
md = ssl_md(sslcipher->algorithm2);
if (md == NULL || !EVP_DigestInit_ex(mdctx, md, NULL)
|| !EVP_DigestUpdate(mdctx, hdata, handlen)
|| !EVP_DigestFinal_ex(mdctx, hashval, &hashlenui)) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
EVP_MD_CTX_free(mdctx);
goto err;
}
hashlen = hashlenui;
EVP_MD_CTX_free(mdctx);
} else if (which & SSL3_CC_HANDSHAKE) {
insecret = s->handshake_secret;
finsecret = s->client_finished_secret;
finsecretlen = EVP_MD_size(ssl_handshake_md(s));
label = client_handshake_traffic;
labellen = sizeof(client_handshake_traffic) - 1;
log_label = CLIENT_HANDSHAKE_LABEL;
/*
* The handshake hash used for the server read/client write handshake
* traffic secret is the same as the hash for the server
* write/client read handshake traffic secret. However, if we
* processed early data then we delay changing the server
* read/client write cipher state until later, and the handshake
* hashes have moved on. Therefore we use the value saved earlier
* when we did the server write/client read change cipher state.
*/
hash = s->handshake_traffic_hash;
} else {
insecret = s->master_secret;
label = client_application_traffic;
labellen = sizeof(client_application_traffic) - 1;
log_label = CLIENT_APPLICATION_LABEL;
/*
* For this we only use the handshake hashes up until the server
* Finished hash. We do not include the client's Finished, which is
* what ssl_handshake_hash() would give us. Instead we use the
* previously saved value.
*/
hash = s->server_finished_hash;
}
} else {
/* Early data never applies to client-read/server-write */
if (which & SSL3_CC_HANDSHAKE) {
insecret = s->handshake_secret;
finsecret = s->server_finished_secret;
finsecretlen = EVP_MD_size(ssl_handshake_md(s));
label = server_handshake_traffic;
labellen = sizeof(server_handshake_traffic) - 1;
log_label = SERVER_HANDSHAKE_LABEL;
} else {
insecret = s->master_secret;
label = server_application_traffic;
labellen = sizeof(server_application_traffic) - 1;
log_label = SERVER_APPLICATION_LABEL;
}
}
if (!(which & SSL3_CC_EARLY)) {
md = ssl_handshake_md(s);
cipher = s->s3->tmp.new_sym_enc;
if (!ssl3_digest_cached_records(s, 1)
|| !ssl_handshake_hash(s, hashval, sizeof(hashval), &hashlen)) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
goto err;
}
}
/*
* Save the hash of handshakes up to now for use when we calculate the
* client application traffic secret
*/
if (label == server_application_traffic)
memcpy(s->server_finished_hash, hashval, hashlen);
if (label == server_handshake_traffic)
memcpy(s->handshake_traffic_hash, hashval, hashlen);
if (label == client_application_traffic) {
/*
* We also create the resumption master secret, but this time use the
* hash for the whole handshake including the Client Finished
*/
if (!tls13_hkdf_expand(s, ssl_handshake_md(s), insecret,
resumption_master_secret,
sizeof(resumption_master_secret) - 1,
hashval, hashlen, s->session->master_key,
hashlen)) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
goto err;
}
s->session->master_key_length = hashlen;
/* Now we create the exporter master secret */
if (!tls13_hkdf_expand(s, ssl_handshake_md(s), insecret,
exporter_master_secret,
sizeof(exporter_master_secret) - 1,
hash, hashlen, s->exporter_master_secret,
hashlen)) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
goto err;
}
}
if (!derive_secret_key_and_iv(s, which & SSL3_CC_WRITE, md, cipher,
insecret, hash, label, labellen, secret, iv,
ciph_ctx)) {
goto err;
}
if (label == server_application_traffic)
memcpy(s->server_app_traffic_secret, secret, hashlen);
else if (label == client_application_traffic)
memcpy(s->client_app_traffic_secret, secret, hashlen);
if (!ssl_log_secret(s, log_label, secret, hashlen)) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
goto err;
}
if (finsecret != NULL
&& !tls13_derive_finishedkey(s, ssl_handshake_md(s), secret,
finsecret, finsecretlen)) {
SSLerr(SSL_F_TLS13_CHANGE_CIPHER_STATE, ERR_R_INTERNAL_ERROR);
goto err;
}
ret = 1;
err:
OPENSSL_cleanse(secret, sizeof(secret));
return ret;
}
int tls13_update_key(SSL *s, int sending)
{
static const unsigned char application_traffic[] = "traffic upd";
const EVP_MD *md = ssl_handshake_md(s);
size_t hashlen = EVP_MD_size(md);
unsigned char *insecret, *iv;
unsigned char secret[EVP_MAX_MD_SIZE];
EVP_CIPHER_CTX *ciph_ctx;
int ret = 0;
if (s->server == sending)
insecret = s->server_app_traffic_secret;
else
insecret = s->client_app_traffic_secret;
if (sending) {
iv = s->write_iv;
ciph_ctx = s->enc_write_ctx;
RECORD_LAYER_reset_write_sequence(&s->rlayer);
} else {
iv = s->read_iv;
ciph_ctx = s->enc_read_ctx;
RECORD_LAYER_reset_read_sequence(&s->rlayer);
}
if (!derive_secret_key_and_iv(s, sending, ssl_handshake_md(s),
s->s3->tmp.new_sym_enc, insecret, NULL,
application_traffic,
sizeof(application_traffic) - 1, secret, iv,
ciph_ctx))
goto err;
memcpy(insecret, secret, hashlen);
ret = 1;
err:
OPENSSL_cleanse(secret, sizeof(secret));
return ret;
}
int tls13_alert_code(int code)
{
if (code == SSL_AD_MISSING_EXTENSION)
return code;
return tls1_alert_code(code);
}
int tls13_export_keying_material(SSL *s, unsigned char *out, size_t olen,
const char *label, size_t llen,
const unsigned char *context,
size_t contextlen, int use_context)
{
unsigned char exportsecret[EVP_MAX_MD_SIZE];
static const unsigned char exporterlabel[] = "exporter";
unsigned char hash[EVP_MAX_MD_SIZE], data[EVP_MAX_MD_SIZE];
const EVP_MD *md = ssl_handshake_md(s);
EVP_MD_CTX *ctx = EVP_MD_CTX_new();
unsigned int hashsize, datalen;
int ret = 0;
if (ctx == NULL || !SSL_is_init_finished(s))
goto err;
if (!use_context)
contextlen = 0;
if (EVP_DigestInit_ex(ctx, md, NULL) <= 0
|| EVP_DigestUpdate(ctx, context, contextlen) <= 0
|| EVP_DigestFinal_ex(ctx, hash, &hashsize) <= 0
|| EVP_DigestInit_ex(ctx, md, NULL) <= 0
|| EVP_DigestFinal_ex(ctx, data, &datalen) <= 0
|| !tls13_hkdf_expand(s, md, s->exporter_master_secret,
(const unsigned char *)label, llen,
data, datalen, exportsecret, hashsize)
|| !tls13_hkdf_expand(s, md, exportsecret, exporterlabel,
sizeof(exporterlabel) - 1, hash, hashsize,
out, olen))
goto err;
ret = 1;
err:
EVP_MD_CTX_free(ctx);
return ret;
}
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