429 lines
12 KiB
C
429 lines
12 KiB
C
/*
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* TLS server tickets callbacks 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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#include "common.h"
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#if defined(MBEDTLS_SSL_TICKET_C)
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#include "mbedtls/platform.h"
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#include "mbedtls/ssl_internal.h"
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#include "mbedtls/ssl_ticket.h"
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#include "mbedtls/error.h"
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#include "mbedtls/platform_util.h"
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#include <string.h>
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/*
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* Initialize context
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*/
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void mbedtls_ssl_ticket_init(mbedtls_ssl_ticket_context *ctx)
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{
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memset(ctx, 0, sizeof(mbedtls_ssl_ticket_context));
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_mutex_init(&ctx->mutex);
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#endif
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}
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#define MAX_KEY_BYTES 32 /* 256 bits */
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#define TICKET_KEY_NAME_BYTES 4
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#define TICKET_IV_BYTES 12
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#define TICKET_CRYPT_LEN_BYTES 2
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#define TICKET_AUTH_TAG_BYTES 16
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#define TICKET_MIN_LEN (TICKET_KEY_NAME_BYTES + \
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TICKET_IV_BYTES + \
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TICKET_CRYPT_LEN_BYTES + \
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TICKET_AUTH_TAG_BYTES)
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#define TICKET_ADD_DATA_LEN (TICKET_KEY_NAME_BYTES + \
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TICKET_IV_BYTES + \
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TICKET_CRYPT_LEN_BYTES)
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/*
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* Generate/update a key
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*/
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MBEDTLS_CHECK_RETURN_CRITICAL
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static int ssl_ticket_gen_key(mbedtls_ssl_ticket_context *ctx,
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unsigned char index)
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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unsigned char buf[MAX_KEY_BYTES];
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mbedtls_ssl_ticket_key *key = ctx->keys + index;
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#if defined(MBEDTLS_HAVE_TIME)
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key->generation_time = (uint32_t) mbedtls_time(NULL);
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#endif
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if ((ret = ctx->f_rng(ctx->p_rng, key->name, sizeof(key->name))) != 0) {
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return ret;
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}
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if ((ret = ctx->f_rng(ctx->p_rng, buf, sizeof(buf))) != 0) {
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return ret;
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}
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/* With GCM and CCM, same context can encrypt & decrypt */
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ret = mbedtls_cipher_setkey(&key->ctx, buf,
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mbedtls_cipher_get_key_bitlen(&key->ctx),
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MBEDTLS_ENCRYPT);
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mbedtls_platform_zeroize(buf, sizeof(buf));
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return ret;
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}
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/*
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* Rotate/generate keys if necessary
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*/
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MBEDTLS_CHECK_RETURN_CRITICAL
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static int ssl_ticket_update_keys(mbedtls_ssl_ticket_context *ctx)
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{
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#if !defined(MBEDTLS_HAVE_TIME)
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((void) ctx);
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#else
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if (ctx->ticket_lifetime != 0) {
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uint32_t current_time = (uint32_t) mbedtls_time(NULL);
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uint32_t key_time = ctx->keys[ctx->active].generation_time;
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if (current_time >= key_time &&
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current_time - key_time < ctx->ticket_lifetime) {
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return 0;
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}
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ctx->active = 1 - ctx->active;
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return ssl_ticket_gen_key(ctx, ctx->active);
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} else
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#endif /* MBEDTLS_HAVE_TIME */
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return 0;
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}
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/*
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* Setup context for actual use
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*/
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int mbedtls_ssl_ticket_setup(mbedtls_ssl_ticket_context *ctx,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
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mbedtls_cipher_type_t cipher,
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uint32_t lifetime)
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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const mbedtls_cipher_info_t *cipher_info;
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ctx->f_rng = f_rng;
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ctx->p_rng = p_rng;
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ctx->ticket_lifetime = lifetime;
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cipher_info = mbedtls_cipher_info_from_type(cipher);
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if (cipher_info == NULL) {
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return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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}
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if (cipher_info->mode != MBEDTLS_MODE_GCM &&
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cipher_info->mode != MBEDTLS_MODE_CCM) {
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return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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}
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if (cipher_info->key_bitlen > 8 * MAX_KEY_BYTES) {
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return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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}
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int do_mbedtls_cipher_setup = 1;
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#if defined(MBEDTLS_USE_PSA_CRYPTO)
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ret = mbedtls_cipher_setup_psa(&ctx->keys[0].ctx,
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cipher_info, TICKET_AUTH_TAG_BYTES);
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switch (ret) {
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case 0:
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do_mbedtls_cipher_setup = 0;
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break;
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case MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE:
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/* We don't yet expect to support all ciphers through PSA,
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* so allow fallback to ordinary mbedtls_cipher_setup(). */
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do_mbedtls_cipher_setup = 1;
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break;
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default:
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return ret;
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}
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#endif /* MBEDTLS_USE_PSA_CRYPTO */
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if (do_mbedtls_cipher_setup) {
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if ((ret = mbedtls_cipher_setup(&ctx->keys[0].ctx, cipher_info))
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!= 0) {
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return ret;
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}
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}
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do_mbedtls_cipher_setup = 1;
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#if defined(MBEDTLS_USE_PSA_CRYPTO)
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do_mbedtls_cipher_setup = 0;
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ret = mbedtls_cipher_setup_psa(&ctx->keys[1].ctx,
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cipher_info, TICKET_AUTH_TAG_BYTES);
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if (ret != 0 && ret != MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE) {
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return ret;
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}
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if (ret == MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE) {
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do_mbedtls_cipher_setup = 1;
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}
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#endif /* MBEDTLS_USE_PSA_CRYPTO */
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if (do_mbedtls_cipher_setup) {
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if ((ret = mbedtls_cipher_setup(&ctx->keys[1].ctx, cipher_info))
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!= 0) {
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return ret;
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}
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}
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if ((ret = ssl_ticket_gen_key(ctx, 0)) != 0 ||
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(ret = ssl_ticket_gen_key(ctx, 1)) != 0) {
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return ret;
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}
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return 0;
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}
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/*
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* Create session ticket, with the following structure:
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*
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* struct {
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* opaque key_name[4];
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* opaque iv[12];
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* opaque encrypted_state<0..2^16-1>;
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* opaque tag[16];
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* } ticket;
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*
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* The key_name, iv, and length of encrypted_state are the additional
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* authenticated data.
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*/
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int mbedtls_ssl_ticket_write(void *p_ticket,
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const mbedtls_ssl_session *session,
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unsigned char *start,
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const unsigned char *end,
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size_t *tlen,
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uint32_t *ticket_lifetime)
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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mbedtls_ssl_ticket_context *ctx = p_ticket;
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mbedtls_ssl_ticket_key *key;
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unsigned char *key_name = start;
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unsigned char *iv = start + TICKET_KEY_NAME_BYTES;
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unsigned char *state_len_bytes = iv + TICKET_IV_BYTES;
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unsigned char *state = state_len_bytes + TICKET_CRYPT_LEN_BYTES;
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size_t clear_len, ciph_len;
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*tlen = 0;
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if (ctx == NULL || ctx->f_rng == NULL) {
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return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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}
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/* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
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* in addition to session itself, that will be checked when writing it. */
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MBEDTLS_SSL_CHK_BUF_PTR(start, end, TICKET_MIN_LEN);
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#if defined(MBEDTLS_THREADING_C)
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if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
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return ret;
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}
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#endif
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if ((ret = ssl_ticket_update_keys(ctx)) != 0) {
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goto cleanup;
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}
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key = &ctx->keys[ctx->active];
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*ticket_lifetime = ctx->ticket_lifetime;
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memcpy(key_name, key->name, TICKET_KEY_NAME_BYTES);
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if ((ret = ctx->f_rng(ctx->p_rng, iv, TICKET_IV_BYTES)) != 0) {
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goto cleanup;
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}
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/* Dump session state */
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if ((ret = mbedtls_ssl_session_save(session,
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state, end - state,
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&clear_len)) != 0 ||
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(unsigned long) clear_len > 65535) {
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goto cleanup;
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}
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MBEDTLS_PUT_UINT16_BE(clear_len, state_len_bytes, 0);
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/* Encrypt and authenticate */
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if ((ret = mbedtls_cipher_auth_encrypt_ext(&key->ctx,
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iv, TICKET_IV_BYTES,
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/* Additional data: key name, IV and length */
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key_name, TICKET_ADD_DATA_LEN,
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state, clear_len,
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state, end - state, &ciph_len,
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TICKET_AUTH_TAG_BYTES)) != 0) {
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goto cleanup;
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}
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if (ciph_len != clear_len + TICKET_AUTH_TAG_BYTES) {
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ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
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goto cleanup;
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}
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*tlen = TICKET_MIN_LEN + ciph_len - TICKET_AUTH_TAG_BYTES;
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cleanup:
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#if defined(MBEDTLS_THREADING_C)
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if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
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return MBEDTLS_ERR_THREADING_MUTEX_ERROR;
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}
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#endif
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return ret;
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}
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/*
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* Select key based on name
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*/
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static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
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mbedtls_ssl_ticket_context *ctx,
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const unsigned char name[4])
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{
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unsigned char i;
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for (i = 0; i < sizeof(ctx->keys) / sizeof(*ctx->keys); i++) {
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if (memcmp(name, ctx->keys[i].name, 4) == 0) {
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return &ctx->keys[i];
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}
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}
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return NULL;
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}
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/*
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* Load session ticket (see mbedtls_ssl_ticket_write for structure)
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*/
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int mbedtls_ssl_ticket_parse(void *p_ticket,
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mbedtls_ssl_session *session,
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unsigned char *buf,
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size_t len)
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{
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int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
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mbedtls_ssl_ticket_context *ctx = p_ticket;
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mbedtls_ssl_ticket_key *key;
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unsigned char *key_name = buf;
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unsigned char *iv = buf + TICKET_KEY_NAME_BYTES;
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unsigned char *enc_len_p = iv + TICKET_IV_BYTES;
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unsigned char *ticket = enc_len_p + TICKET_CRYPT_LEN_BYTES;
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size_t enc_len, clear_len;
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if (ctx == NULL || ctx->f_rng == NULL) {
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return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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}
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if (len < TICKET_MIN_LEN) {
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return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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}
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#if defined(MBEDTLS_THREADING_C)
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if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
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return ret;
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}
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#endif
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if ((ret = ssl_ticket_update_keys(ctx)) != 0) {
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goto cleanup;
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}
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enc_len = (enc_len_p[0] << 8) | enc_len_p[1];
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if (len != TICKET_MIN_LEN + enc_len) {
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ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
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goto cleanup;
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}
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/* Select key */
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if ((key = ssl_ticket_select_key(ctx, key_name)) == NULL) {
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/* We can't know for sure but this is a likely option unless we're
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* under attack - this is only informative anyway */
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ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
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goto cleanup;
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}
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/* Decrypt and authenticate */
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if ((ret = mbedtls_cipher_auth_decrypt_ext(&key->ctx,
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iv, TICKET_IV_BYTES,
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/* Additional data: key name, IV and length */
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key_name, TICKET_ADD_DATA_LEN,
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ticket, enc_len + TICKET_AUTH_TAG_BYTES,
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ticket, enc_len, &clear_len,
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TICKET_AUTH_TAG_BYTES)) != 0) {
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if (ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED) {
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ret = MBEDTLS_ERR_SSL_INVALID_MAC;
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}
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goto cleanup;
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}
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if (clear_len != enc_len) {
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ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
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goto cleanup;
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}
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/* Actually load session */
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if ((ret = mbedtls_ssl_session_load(session, ticket, clear_len)) != 0) {
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goto cleanup;
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}
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#if defined(MBEDTLS_HAVE_TIME)
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{
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/* Check for expiration */
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mbedtls_time_t current_time = mbedtls_time(NULL);
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if (current_time < session->start ||
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(uint32_t) (current_time - session->start) > ctx->ticket_lifetime) {
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ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
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goto cleanup;
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}
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}
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#endif
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cleanup:
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#if defined(MBEDTLS_THREADING_C)
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if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
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return MBEDTLS_ERR_THREADING_MUTEX_ERROR;
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}
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#endif
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return ret;
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}
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/*
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* Free context
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*/
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void mbedtls_ssl_ticket_free(mbedtls_ssl_ticket_context *ctx)
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{
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mbedtls_cipher_free(&ctx->keys[0].ctx);
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mbedtls_cipher_free(&ctx->keys[1].ctx);
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#if defined(MBEDTLS_THREADING_C)
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mbedtls_mutex_free(&ctx->mutex);
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#endif
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mbedtls_platform_zeroize(ctx, sizeof(mbedtls_ssl_ticket_context));
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}
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#endif /* MBEDTLS_SSL_TICKET_C */
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