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/*
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* Copyright (C) 2017 Red Hat, Inc.
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*
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* Author: Nikos Mavrogiannopoulos
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*
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* This file is part of GnuTLS.
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*
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* The GnuTLS is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public License
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* as published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>
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*
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*/
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/* TLS 1.3 secret key derivation handling.
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*/
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#include <config.h>
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#include "gnutls_int.h"
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#include <nettle/hkdf.h>
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#include <nettle/hmac.h>
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#include "secrets.h"
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/* HKDF-Extract(0,0) or HKDF-Extract(0, PSK) */
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int _tls13_init_secret(gnutls_session_t session, const uint8_t *psk, size_t psk_size)
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{
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session->key.proto.tls13.temp_secret_size = session->security_parameters.prf->output_size;
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return _tls13_init_secret2(session->security_parameters.prf,
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psk, psk_size,
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session->key.proto.tls13.temp_secret);
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}
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int _tls13_init_secret2(const mac_entry_st *prf,
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const uint8_t *psk, size_t psk_size,
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void *out)
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{
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char buf[128];
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if (unlikely(prf == NULL))
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return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
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/* when no PSK, use the zero-value */
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if (psk == NULL) {
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psk_size = prf->output_size;
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if (unlikely(psk_size >= sizeof(buf)))
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return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
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memset(buf, 0, psk_size);
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psk = (uint8_t*) buf;
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}
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return gnutls_hmac_fast(prf->id,
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"", 0,
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psk, psk_size,
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out);
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}
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/* HKDF-Extract(Prev-Secret, key) */
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int _tls13_update_secret(gnutls_session_t session, const uint8_t *key, size_t key_size)
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{
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return gnutls_hmac_fast(session->security_parameters.prf->id,
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session->key.proto.tls13.temp_secret, session->key.proto.tls13.temp_secret_size,
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key, key_size,
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session->key.proto.tls13.temp_secret);
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}
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/* Derive-Secret(Secret, Label, Messages) */
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int _tls13_derive_secret2(const mac_entry_st *prf,
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const char *label, unsigned label_size,
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const uint8_t *tbh, size_t tbh_size,
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const uint8_t secret[MAX_HASH_SIZE],
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void *out)
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{
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uint8_t digest[MAX_HASH_SIZE];
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int ret;
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unsigned digest_size;
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if (unlikely(prf == NULL))
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return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
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if (unlikely(label_size >= sizeof(digest)))
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return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
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digest_size = prf->output_size;
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ret = gnutls_hash_fast((gnutls_digest_algorithm_t) prf->id,
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tbh, tbh_size, digest);
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if (ret < 0)
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return gnutls_assert_val(ret);
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return _tls13_expand_secret2(prf, label, label_size, digest, digest_size, secret, digest_size, out);
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}
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/* Derive-Secret(Secret, Label, Messages) */
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int _tls13_derive_secret(gnutls_session_t session,
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const char *label, unsigned label_size,
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const uint8_t *tbh, size_t tbh_size,
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const uint8_t secret[MAX_HASH_SIZE],
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void *out)
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{
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if (unlikely(session->security_parameters.prf == NULL))
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return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
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return _tls13_derive_secret2(session->security_parameters.prf, label, label_size, tbh, tbh_size,
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secret,
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out);
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}
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/* HKDF-Expand-Label(Secret, Label, HashValue, Length) */
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int _tls13_expand_secret2(const mac_entry_st *prf,
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const char *label, unsigned label_size,
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const uint8_t *msg, size_t msg_size,
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const uint8_t secret[MAX_HASH_SIZE],
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unsigned out_size,
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void *out)
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{
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uint8_t tmp[256] = "tls13 ";
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gnutls_buffer_st str;
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int ret;
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if (unlikely(label_size >= sizeof(tmp)-6))
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return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
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_gnutls_buffer_init(&str);
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ret = _gnutls_buffer_append_prefix(&str, 16, out_size);
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if (ret < 0) {
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gnutls_assert();
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goto cleanup;
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}
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memcpy(&tmp[6], label, label_size);
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ret = _gnutls_buffer_append_data_prefix(&str, 8, tmp, label_size+6);
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if (ret < 0) {
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gnutls_assert();
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goto cleanup;
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}
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ret = _gnutls_buffer_append_data_prefix(&str, 8, msg, msg_size);
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if (ret < 0) {
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gnutls_assert();
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goto cleanup;
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}
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switch (prf->id) {
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case GNUTLS_MAC_SHA256:{
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struct hmac_sha256_ctx ctx;
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hmac_sha256_set_key(&ctx, SHA256_DIGEST_SIZE, secret);
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hkdf_expand(&ctx, (nettle_hash_update_func*)hmac_sha256_update,
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(nettle_hash_digest_func*)hmac_sha256_digest, SHA256_DIGEST_SIZE,
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str.length, str.data, out_size, out);
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break;
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}
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case GNUTLS_MAC_SHA384:{
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struct hmac_sha384_ctx ctx;
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hmac_sha384_set_key(&ctx, SHA384_DIGEST_SIZE, secret);
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hkdf_expand(&ctx, (nettle_hash_update_func*)hmac_sha384_update,
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(nettle_hash_digest_func*)hmac_sha384_digest, SHA384_DIGEST_SIZE,
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str.length, str.data, out_size, out);
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break;
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}
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default:
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gnutls_assert();
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ret = GNUTLS_E_INTERNAL_ERROR;
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goto cleanup;
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}
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#if 0
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_gnutls_hard_log("INT: hkdf label: %d,%s\n",
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out_size,
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_gnutls_bin2hex(str.data, str.length,
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(char*)tmp, sizeof(tmp), NULL));
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_gnutls_hard_log("INT: secret expanded for '%.*s': %d,%s\n",
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(int)label_size, label, out_size,
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_gnutls_bin2hex(out, out_size,
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(char*)tmp, sizeof(tmp), NULL));
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#endif
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ret = 0;
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cleanup:
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_gnutls_buffer_clear(&str);
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return ret;
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}
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int _tls13_expand_secret(gnutls_session_t session,
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const char *label, unsigned label_size,
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const uint8_t *msg, size_t msg_size,
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const uint8_t secret[MAX_CIPHER_KEY_SIZE],
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unsigned out_size,
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void *out)
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{
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if (unlikely(session->security_parameters.prf == NULL))
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return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
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return _tls13_expand_secret2(session->security_parameters.prf,
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label, label_size,
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msg, msg_size, secret,
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out_size, out);
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}
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