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