mbedtls/configs/config-ccm-psk-dtls1_2.h

/**
 * \file config-ccm-psk-dtls1_2.h
 *
 * \brief Small configuration for DTLS 1.2 with PSK and AES-CCM ciphersuites
 */
/*
 *  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.
 */
/*
 * Minimal configuration for DTLS 1.2 with PSK and AES-CCM ciphersuites
 *
 * Distinguishing features:
 * - Optimized for small code size, low bandwidth (on an unreliable transport),
 *   and low RAM usage.
 * - No asymmetric cryptography (no certificates, no Diffie-Hellman key
 *   exchange).
 * - Fully modern and secure (provided the pre-shared keys are generated and
 *   stored securely).
 * - Very low record overhead with CCM-8.
 * - Includes several optional DTLS features typically used in IoT.
 *
 * See README.txt for usage instructions.
 */

/* System support */
//#define MBEDTLS_HAVE_TIME /* Optionally used in Hello messages */
/* Other MBEDTLS_HAVE_XXX flags irrelevant for this configuration */

/* Mbed TLS modules */
#define MBEDTLS_AES_C
#define MBEDTLS_CCM_C
#define MBEDTLS_CIPHER_C
#define MBEDTLS_CTR_DRBG_C
#define MBEDTLS_ENTROPY_C
#define MBEDTLS_MD_C
#define MBEDTLS_NET_C
#define MBEDTLS_SHA256_C
#define MBEDTLS_SSL_CLI_C
#define MBEDTLS_SSL_COOKIE_C
#define MBEDTLS_SSL_SRV_C
#define MBEDTLS_SSL_TLS_C
#define MBEDTLS_TIMING_C

/* TLS protocol feature support */
#define MBEDTLS_KEY_EXCHANGE_PSK_ENABLED
#define MBEDTLS_SSL_PROTO_TLS1_2
#define MBEDTLS_SSL_PROTO_DTLS
#define MBEDTLS_SSL_DTLS_ANTI_REPLAY
#define MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE
#define MBEDTLS_SSL_DTLS_CONNECTION_ID
#define MBEDTLS_SSL_DTLS_HELLO_VERIFY
#define MBEDTLS_SSL_MAX_FRAGMENT_LENGTH

/*
 * Use only CCM_8 ciphersuites, and
 * save ROM and a few bytes of RAM by specifying our own ciphersuite list
 */
#define MBEDTLS_SSL_CIPHERSUITES                        \
    MBEDTLS_TLS_PSK_WITH_AES_256_CCM_8,             \
    MBEDTLS_TLS_PSK_WITH_AES_128_CCM_8

/*
 * Save RAM at the expense of interoperability: do this only if you control
 * both ends of the connection!  (See comments in "mbedtls/ssl.h".)
 * The optimal size here depends on the typical size of records.
 */
#define MBEDTLS_SSL_IN_CONTENT_LEN              256
#define MBEDTLS_SSL_OUT_CONTENT_LEN             256

/* Save RAM at the expense of ROM */
#define MBEDTLS_AES_ROM_TABLES

/* Save some RAM by adjusting to your exact needs */
#define MBEDTLS_PSK_MAX_LEN    16 /* 128-bits keys are generally enough */

/*
 * You should adjust this to the exact number of sources you're using: default
 * is the "platform_entropy_poll" source, but you may want to add other ones
 * Minimum is 2 for the entropy test suite.
 */
#define MBEDTLS_ENTROPY_MAX_SOURCES 2

/* These defines are present so that the config modifying scripts can enable
 * them during tests/scripts/test-ref-configs.pl */
//#define MBEDTLS_USE_PSA_CRYPTO
//#define MBEDTLS_PSA_CRYPTO_C

/* Error messages and TLS debugging traces
 * (huge code size increase, needed for tests/ssl-opt.sh) */
//#define MBEDTLS_DEBUG_C
//#define MBEDTLS_ERROR_C