mbedtls/library/ssl_cache.c
Pengyu Lv 5038a38695 ssl_cache: Return standard mbedtls error code
Signed-off-by: Pengyu Lv <pengyu.lv@arm.com>
2023-03-23 15:53:43 +08:00

424 lines
11 KiB
C

/*
* SSL session cache implementation
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* These session callbacks use a simple chained list
* to store and retrieve the session information.
*/
#include "common.h"
#if defined(MBEDTLS_SSL_CACHE_C)
#include "mbedtls/platform.h"
#include "mbedtls/ssl_cache.h"
#include "ssl_misc.h"
#include "mbedtls/error.h"
#include <string.h>
void mbedtls_ssl_cache_init(mbedtls_ssl_cache_context *cache)
{
memset(cache, 0, sizeof(mbedtls_ssl_cache_context));
cache->timeout = MBEDTLS_SSL_CACHE_DEFAULT_TIMEOUT;
cache->max_entries = MBEDTLS_SSL_CACHE_DEFAULT_MAX_ENTRIES;
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init(&cache->mutex);
#endif
}
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_cache_find_entry(mbedtls_ssl_cache_context *cache,
unsigned char const *session_id,
size_t session_id_len,
mbedtls_ssl_cache_entry **dst)
{
int ret = MBEDTLS_ERR_SSL_CACHE_NOT_FOUND;
#if defined(MBEDTLS_HAVE_TIME)
mbedtls_time_t t = mbedtls_time(NULL);
#endif
mbedtls_ssl_cache_entry *cur;
for (cur = cache->chain; cur != NULL; cur = cur->next) {
#if defined(MBEDTLS_HAVE_TIME)
if (cache->timeout != 0 &&
(int) (t - cur->timestamp) > cache->timeout) {
continue;
}
#endif
if (session_id_len != cur->session_id_len ||
memcmp(session_id, cur->session_id,
cur->session_id_len) != 0) {
continue;
}
break;
}
if (cur != NULL) {
*dst = cur;
ret = 0;
}
return ret;
}
int mbedtls_ssl_cache_get(void *data,
unsigned char const *session_id,
size_t session_id_len,
mbedtls_ssl_session *session)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ssl_cache_context *cache = (mbedtls_ssl_cache_context *) data;
mbedtls_ssl_cache_entry *entry;
#if defined(MBEDTLS_THREADING_C)
if ((ret = mbedtls_mutex_lock(&cache->mutex)) != 0) {
return ret;
}
#endif
ret = ssl_cache_find_entry(cache, session_id, session_id_len, &entry);
if (ret != 0) {
goto exit;
}
ret = mbedtls_ssl_session_load(session,
entry->session,
entry->session_len);
if (ret != 0) {
goto exit;
}
ret = 0;
exit:
#if defined(MBEDTLS_THREADING_C)
if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
ret = MBEDTLS_ERR_THREADING_MUTEX_ERROR;
}
#endif
return ret;
}
/* zeroize a cache entry */
static void ssl_cache_entry_zeroize(mbedtls_ssl_cache_entry *entry)
{
if (entry == NULL) {
return;
}
/* zeroize and free session structure */
if (entry->session != NULL) {
mbedtls_platform_zeroize(entry->session, entry->session_len);
mbedtls_free(entry->session);
}
/* zeroize the whole entry structure */
mbedtls_platform_zeroize(entry, sizeof(mbedtls_ssl_cache_entry));
}
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_cache_pick_writing_slot(mbedtls_ssl_cache_context *cache,
unsigned char const *session_id,
size_t session_id_len,
mbedtls_ssl_cache_entry **dst)
{
#if defined(MBEDTLS_HAVE_TIME)
mbedtls_time_t t = mbedtls_time(NULL), oldest = 0;
#endif /* MBEDTLS_HAVE_TIME */
mbedtls_ssl_cache_entry *old = NULL;
int count = 0;
mbedtls_ssl_cache_entry *cur, *last;
/* Check 1: Is there already an entry with the given session ID?
*
* If yes, overwrite it.
*
* If not, `count` will hold the size of the session cache
* at the end of this loop, and `last` will point to the last
* entry, both of which will be used later. */
last = NULL;
for (cur = cache->chain; cur != NULL; cur = cur->next) {
count++;
if (session_id_len == cur->session_id_len &&
memcmp(session_id, cur->session_id, cur->session_id_len) == 0) {
goto found;
}
last = cur;
}
/* Check 2: Is there an outdated entry in the cache?
*
* If so, overwrite it.
*
* If not, remember the oldest entry in `old` for later.
*/
#if defined(MBEDTLS_HAVE_TIME)
for (cur = cache->chain; cur != NULL; cur = cur->next) {
if (cache->timeout != 0 &&
(int) (t - cur->timestamp) > cache->timeout) {
goto found;
}
if (oldest == 0 || cur->timestamp < oldest) {
oldest = cur->timestamp;
old = cur;
}
}
#endif /* MBEDTLS_HAVE_TIME */
/* Check 3: Is there free space in the cache? */
if (count < cache->max_entries) {
/* Create new entry */
cur = mbedtls_calloc(1, sizeof(mbedtls_ssl_cache_entry));
if (cur == NULL) {
return MBEDTLS_ERR_SSL_ALLOC_FAILED;
}
/* Append to the end of the linked list. */
if (last == NULL) {
cache->chain = cur;
} else {
last->next = cur;
}
goto found;
}
/* Last resort: The cache is full and doesn't contain any outdated
* elements. In this case, we evict the oldest one, judged by timestamp
* (if present) or cache-order. */
#if defined(MBEDTLS_HAVE_TIME)
if (old == NULL) {
/* This should only happen on an ill-configured cache
* with max_entries == 0. */
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
}
#else /* MBEDTLS_HAVE_TIME */
/* Reuse first entry in chain, but move to last place. */
if (cache->chain == NULL) {
/* This should never happen */
return MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
}
old = cache->chain;
cache->chain = old->next;
old->next = NULL;
last->next = old;
#endif /* MBEDTLS_HAVE_TIME */
/* Now `old` points to the oldest entry to be overwritten. */
cur = old;
found:
/* If we're reusing an entry, free it first. */
if (cur->session != NULL) {
/* `ssl_cache_entry_zeroize` would break the chain,
* so we reuse `old` to record `next` temporarily. */
old = cur->next;
ssl_cache_entry_zeroize(cur);
cur->next = old;
}
#if defined(MBEDTLS_HAVE_TIME)
cur->timestamp = t;
#endif
*dst = cur;
return 0;
}
int mbedtls_ssl_cache_set(void *data,
unsigned char const *session_id,
size_t session_id_len,
const mbedtls_ssl_session *session)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ssl_cache_context *cache = (mbedtls_ssl_cache_context *) data;
mbedtls_ssl_cache_entry *cur;
size_t session_serialized_len;
unsigned char *session_serialized = NULL;
#if defined(MBEDTLS_THREADING_C)
if ((ret = mbedtls_mutex_lock(&cache->mutex)) != 0) {
return ret;
}
#endif
ret = ssl_cache_pick_writing_slot(cache,
session_id, session_id_len,
&cur);
if (ret != 0) {
goto exit;
}
/* Check how much space we need to serialize the session
* and allocate a sufficiently large buffer. */
ret = mbedtls_ssl_session_save(session, NULL, 0, &session_serialized_len);
if (ret != MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL) {
goto exit;
}
session_serialized = mbedtls_calloc(1, session_serialized_len);
if (session_serialized == NULL) {
ret = MBEDTLS_ERR_SSL_ALLOC_FAILED;
goto exit;
}
/* Now serialize the session into the allocated buffer. */
ret = mbedtls_ssl_session_save(session,
session_serialized,
session_serialized_len,
&session_serialized_len);
if (ret != 0) {
goto exit;
}
if (session_id_len > sizeof(cur->session_id)) {
ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
goto exit;
}
cur->session_id_len = session_id_len;
memcpy(cur->session_id, session_id, session_id_len);
cur->session = session_serialized;
cur->session_len = session_serialized_len;
session_serialized = NULL;
ret = 0;
exit:
#if defined(MBEDTLS_THREADING_C)
if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
ret = MBEDTLS_ERR_THREADING_MUTEX_ERROR;
}
#endif
if (session_serialized != NULL) {
mbedtls_platform_zeroize(session_serialized, session_serialized_len);
mbedtls_free(session_serialized);
session_serialized = NULL;
}
return ret;
}
int mbedtls_ssl_cache_remove(void *data,
unsigned char const *session_id,
size_t session_id_len)
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_ssl_cache_context *cache = (mbedtls_ssl_cache_context *) data;
mbedtls_ssl_cache_entry *entry;
mbedtls_ssl_cache_entry *prev;
#if defined(MBEDTLS_THREADING_C)
if ((ret = mbedtls_mutex_lock(&cache->mutex)) != 0) {
return ret;
}
#endif
ret = ssl_cache_find_entry(cache, session_id, session_id_len, &entry);
/* No valid entry found, exit with success */
if (ret != 0) {
ret = 0;
goto exit;
}
/* Now we remove the entry from the chain */
if (entry == cache->chain) {
cache->chain = entry->next;
goto free;
}
for (prev = cache->chain; prev->next != NULL; prev = prev->next) {
if (prev->next == entry) {
prev->next = entry->next;
break;
}
}
free:
ssl_cache_entry_zeroize(entry);
mbedtls_free(entry);
ret = 0;
exit:
#if defined(MBEDTLS_THREADING_C)
if (mbedtls_mutex_unlock(&cache->mutex) != 0) {
ret = MBEDTLS_ERR_THREADING_MUTEX_ERROR;
}
#endif
return ret;
}
#if defined(MBEDTLS_HAVE_TIME)
void mbedtls_ssl_cache_set_timeout(mbedtls_ssl_cache_context *cache, int timeout)
{
if (timeout < 0) {
timeout = 0;
}
cache->timeout = timeout;
}
#endif /* MBEDTLS_HAVE_TIME */
void mbedtls_ssl_cache_set_max_entries(mbedtls_ssl_cache_context *cache, int max)
{
if (max < 0) {
max = 0;
}
cache->max_entries = max;
}
void mbedtls_ssl_cache_free(mbedtls_ssl_cache_context *cache)
{
mbedtls_ssl_cache_entry *cur, *prv;
cur = cache->chain;
while (cur != NULL) {
prv = cur;
cur = cur->next;
ssl_cache_entry_zeroize(prv);
mbedtls_free(prv);
}
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_free(&cache->mutex);
#endif
cache->chain = NULL;
}
#endif /* MBEDTLS_SSL_CACHE_C */