385 lines
9.2 KiB
C
385 lines
9.2 KiB
C
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/*
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* SSL session cache implementation
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/*
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* These session callbacks use a simple chained list
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* to store and retrieve the session information.
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*/
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#include "common.h"
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#if defined(MBEDTLS_SSL_CACHE_C)
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#if defined(MBEDTLS_PLATFORM_C)
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#include "mbedtls/platform.h"
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#else
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#include <stdlib.h>
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#define mbedtls_calloc calloc
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#define mbedtls_free free
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#endif
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#include "mbedtls/ssl_cache.h"
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#include "ssl_misc.h"
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#include <string.h>
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void mbedtls_ssl_cache_init(mbedtls_ssl_cache_context *cache)
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{
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memset(cache, 0, sizeof(mbedtls_ssl_cache_context));
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cache->timeout = MBEDTLS_SSL_CACHE_DEFAULT_TIMEOUT;
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cache->max_entries = MBEDTLS_SSL_CACHE_DEFAULT_MAX_ENTRIES;
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_mutex_init(&cache->mutex);
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#endif
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}
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static int ssl_cache_find_entry(mbedtls_ssl_cache_context *cache,
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unsigned char const *session_id,
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size_t session_id_len,
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mbedtls_ssl_cache_entry **dst)
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{
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int ret = 1;
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#if defined(MBEDTLS_HAVE_TIME)
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mbedtls_time_t t = mbedtls_time(NULL);
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#endif
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mbedtls_ssl_cache_entry *cur;
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for (cur = cache->chain; cur != NULL; cur = cur->next) {
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#if defined(MBEDTLS_HAVE_TIME)
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if (cache->timeout != 0 &&
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(int)(t - cur->timestamp) > cache->timeout) {
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continue;
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}
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#endif
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if (session_id_len != cur->session_id_len ||
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memcmp(session_id, cur->session_id,
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cur->session_id_len) != 0) {
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continue;
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}
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break;
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}
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if (cur != NULL) {
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*dst = cur;
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ret = 0;
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}
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return (ret);
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}
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int mbedtls_ssl_cache_get(void *data,
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unsigned char const *session_id,
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size_t session_id_len,
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mbedtls_ssl_session *session)
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{
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int ret = 1;
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mbedtls_ssl_cache_context *cache = (mbedtls_ssl_cache_context *)data;
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mbedtls_ssl_cache_entry *entry;
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#if defined(MBEDTLS_THREADING_C)
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if (mbedtls_mutex_lock(&cache->mutex) != 0) {
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return (1);
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}
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#endif
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ret = ssl_cache_find_entry(cache, session_id, session_id_len, &entry);
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if (ret != 0) {
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goto exit;
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}
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ret = mbedtls_ssl_session_load(session,
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entry->session,
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entry->session_len);
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if (ret != 0) {
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goto exit;
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}
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ret = 0;
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exit:
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#if defined(MBEDTLS_THREADING_C)
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if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
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ret = 1;
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}
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#endif
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return (ret);
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}
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static int ssl_cache_pick_writing_slot(mbedtls_ssl_cache_context *cache,
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unsigned char const *session_id,
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size_t session_id_len,
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mbedtls_ssl_cache_entry **dst)
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{
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#if defined(MBEDTLS_HAVE_TIME)
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mbedtls_time_t t = mbedtls_time(NULL), oldest = 0;
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#endif /* MBEDTLS_HAVE_TIME */
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mbedtls_ssl_cache_entry *old = NULL;
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int count = 0;
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mbedtls_ssl_cache_entry *cur, *last;
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/* Check 1: Is there already an entry with the given session ID?
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*
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* If yes, overwrite it.
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*
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* If not, `count` will hold the size of the session cache
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* at the end of this loop, and `last` will point to the last
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* entry, both of which will be used later. */
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last = NULL;
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for (cur = cache->chain; cur != NULL; cur = cur->next) {
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count++;
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if (session_id_len == cur->session_id_len &&
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memcmp(session_id, cur->session_id, cur->session_id_len) == 0) {
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goto found;
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}
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last = cur;
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}
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/* Check 2: Is there an outdated entry in the cache?
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*
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* If so, overwrite it.
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*
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* If not, remember the oldest entry in `old` for later.
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*/
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#if defined(MBEDTLS_HAVE_TIME)
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for (cur = cache->chain; cur != NULL; cur = cur->next) {
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if (cache->timeout != 0 &&
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(int)(t - cur->timestamp) > cache->timeout) {
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goto found;
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}
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if (oldest == 0 || cur->timestamp < oldest) {
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oldest = cur->timestamp;
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old = cur;
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}
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}
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#endif /* MBEDTLS_HAVE_TIME */
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/* Check 3: Is there free space in the cache? */
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if (count < cache->max_entries) {
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/* Create new entry */
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cur = mbedtls_calloc(1, sizeof(mbedtls_ssl_cache_entry));
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if (cur == NULL) {
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return (1);
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}
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/* Append to the end of the linked list. */
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if (last == NULL) {
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cache->chain = cur;
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} else {
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last->next = cur;
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}
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goto found;
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}
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/* Last resort: The cache is full and doesn't contain any outdated
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* elements. In this case, we evict the oldest one, judged by timestamp
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* (if present) or cache-order. */
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#if defined(MBEDTLS_HAVE_TIME)
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if (old == NULL) {
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/* This should only happen on an ill-configured cache
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* with max_entries == 0. */
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return (1);
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}
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#else /* MBEDTLS_HAVE_TIME */
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/* Reuse first entry in chain, but move to last place. */
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if (cache->chain == NULL) {
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return (1);
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}
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old = cache->chain;
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cache->chain = old->next;
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old->next = NULL;
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last->next = old;
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#endif /* MBEDTLS_HAVE_TIME */
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/* Now `old` points to the oldest entry to be overwritten. */
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cur = old;
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found:
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#if defined(MBEDTLS_HAVE_TIME)
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cur->timestamp = t;
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#endif
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/* If we're reusing an entry, free it first. */
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if (cur->session != NULL) {
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mbedtls_free(cur->session);
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cur->session = NULL;
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cur->session_len = 0;
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memset(cur->session_id, 0, sizeof(cur->session_id));
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cur->session_id_len = 0;
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}
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*dst = cur;
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return (0);
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}
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int mbedtls_ssl_cache_set(void *data,
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unsigned char const *session_id,
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size_t session_id_len,
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const mbedtls_ssl_session *session)
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{
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int ret = 1;
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mbedtls_ssl_cache_context *cache = (mbedtls_ssl_cache_context *)data;
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mbedtls_ssl_cache_entry *cur;
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size_t session_serialized_len;
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unsigned char *session_serialized = NULL;
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#if defined(MBEDTLS_THREADING_C)
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if ((ret = mbedtls_mutex_lock(&cache->mutex)) != 0) {
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return (ret);
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}
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#endif
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ret = ssl_cache_pick_writing_slot(cache,
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session_id, session_id_len,
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&cur);
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if (ret != 0) {
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goto exit;
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}
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/* Check how much space we need to serialize the session
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* and allocate a sufficiently large buffer. */
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ret = mbedtls_ssl_session_save(session, NULL, 0, &session_serialized_len);
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if (ret != MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL) {
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ret = 1;
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goto exit;
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}
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session_serialized = mbedtls_calloc(1, session_serialized_len);
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if (session_serialized == NULL) {
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ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
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goto exit;
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}
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/* Now serialize the session into the allocated buffer. */
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ret = mbedtls_ssl_session_save(session,
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session_serialized,
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session_serialized_len,
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&session_serialized_len);
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if (ret != 0) {
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goto exit;
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}
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if (session_id_len > sizeof(cur->session_id)) {
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ret = 1;
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goto exit;
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}
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cur->session_id_len = session_id_len;
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memcpy(cur->session_id, session_id, session_id_len);
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cur->session = session_serialized;
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cur->session_len = session_serialized_len;
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session_serialized = NULL;
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ret = 0;
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exit:
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#if defined(MBEDTLS_THREADING_C)
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if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
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ret = 1;
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}
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#endif
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if (session_serialized != NULL) {
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mbedtls_platform_zeroize(session_serialized, session_serialized_len);
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}
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return (ret);
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}
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#if defined(MBEDTLS_HAVE_TIME)
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void mbedtls_ssl_cache_set_timeout(mbedtls_ssl_cache_context *cache, int timeout)
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{
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if (timeout < 0) {
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timeout = 0;
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}
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cache->timeout = timeout;
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}
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#endif /* MBEDTLS_HAVE_TIME */
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void mbedtls_ssl_cache_set_max_entries(mbedtls_ssl_cache_context *cache, int max)
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{
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if (max < 0) {
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max = 0;
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}
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cache->max_entries = max;
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}
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void mbedtls_ssl_cache_free(mbedtls_ssl_cache_context *cache)
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{
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mbedtls_ssl_cache_entry *cur, *prv;
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cur = cache->chain;
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while (cur != NULL) {
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prv = cur;
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cur = cur->next;
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mbedtls_free(prv->session);
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mbedtls_free(prv);
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}
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_mutex_free(&cache->mutex);
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#endif
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cache->chain = NULL;
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}
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#endif /* MBEDTLS_SSL_CACHE_C */
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