I am in the process of updating an existing and working TLS 1.2 build from Mbed TLS v3.0.0 to TLS 1.3 from Mbed TLS v3.6.0, and I am seeing very slow TLS handshakes, specifically the Server Hello and Certificate Verify steps. The former is averaging about 1.4 seconds, and the latter is averaging about 0.9 seconds. Everything else looks good, but I am seeing a New Session Ticket being sent out with every new socket that is opened, and I didn’t see this behavior in TLS 1.2. I’m not sure if this problem is related or not.
This is running on an ARM Cortex-M4
Here is my current config. Please let me know what else I should provide!
#define MBEDTLS_HAVE_ASM
#define MBEDTLS_HAVE_TIME
#define MBEDTLS_PLATFORM_MEMORY
#define MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
#define MBEDTLS_PLATFORM_PRINTF_ALT debug_printf
#define MBEDTLS_PLATFORM_SNPRINTF_ALT _io_snprintf
#define MBEDTLS_PLATFORM_ZEROIZE_ALT _mem_zero
#define MBEDTLS_DEPRECATED_REMOVED
#define MBEDTLS_TIMING_ALT
#define MBEDTLS_ENTROPY_HARDWARE_ALT
#define MBEDTLS_CIPHER_MODE_CBC
#define MBEDTLS_CIPHER_MODE_CFB
#define MBEDTLS_CIPHER_MODE_CTR
#define MBEDTLS_CIPHER_MODE_OFB
#define MBEDTLS_CIPHER_PADDING_PKCS7
#define MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS
#define MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN
#define MBEDTLS_CIPHER_PADDING_ZEROS
#define MBEDTLS_ECP_DP_SECP256R1_ENABLED
#define MBEDTLS_ECP_NIST_OPTIM
#define MBEDTLS_ECDSA_DETERMINISTIC
#define MBEDTLS_KEY_EXCHANGE_DHE_PSK_ENABLED
#define MBEDTLS_KEY_EXCHANGE_ECDHE_PSK_ENABLED
#define MBEDTLS_KEY_EXCHANGE_RSA_PSK_ENABLED
#define MBEDTLS_KEY_EXCHANGE_RSA_ENABLED
#define MBEDTLS_KEY_EXCHANGE_DHE_RSA_ENABLED
#define MBEDTLS_KEY_EXCHANGE_ECDHE_RSA_ENABLED
#define MBEDTLS_KEY_EXCHANGE_ECDHE_ECDSA_ENABLED
#define MBEDTLS_KEY_EXCHANGE_ECDH_ECDSA_ENABLED
#define MBEDTLS_KEY_EXCHANGE_ECDH_RSA_ENABLED
#define MBEDTLS_PK_PARSE_EC_EXTENDED
#define MBEDTLS_PK_PARSE_EC_COMPRESSED
#define MBEDTLS_GENPRIME
#define MBEDTLS_NO_PLATFORM_ENTROPY
#define MBEDTLS_PK_RSA_ALT_SUPPORT
#define MBEDTLS_PKCS1_V15
#define MBEDTLS_PKCS1_V21
#define MBEDTLS_PSA_CRYPTO_CLIENT
#define MBEDTLS_SSL_ALL_ALERT_MESSAGES
#define MBEDTLS_SSL_CONTEXT_SERIALIZATION
#define MBEDTLS_SSL_ENCRYPT_THEN_MAC
#define MBEDTLS_SSL_EXTENDED_MASTER_SECRET
#define MBEDTLS_SSL_KEEP_PEER_CERTIFICATE
#define MBEDTLS_SSL_RENEGOTIATION
#define MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
#define MBEDTLS_SSL_PROTO_TLS1_2
#define MBEDTLS_SSL_PROTO_TLS1_3
#define MBEDTLS_SSL_TLS1_3_COMPATIBILITY_MODE
#define MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_ENABLED
#define MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_EPHEMERAL_ENABLED
#define MBEDTLS_SSL_TLS1_3_KEY_EXCHANGE_MODE_PSK_EPHEMERAL_ENABLED
#define MBEDTLS_SSL_EARLY_DATA
#define MBEDTLS_SSL_ALPN
#define MBEDTLS_SSL_SESSION_TICKETS
#define MBEDTLS_SSL_VARIABLE_BUFFER_LENGTH
#define MBEDTLS_THREADING_ALT
#define MBEDTLS_USE_PSA_CRYPTO
#define MBEDTLS_PSA_CRYPTO_CONFIG
#define MBEDTLS_VERSION_FEATURES
#define MBEDTLS_X509_RSASSA_PSS_SUPPORT
#define MBEDTLS_AESNI_C
#define MBEDTLS_AESCE_C
#define MBEDTLS_AES_C
#define MBEDTLS_ASN1_PARSE_C
#define MBEDTLS_ASN1_WRITE_C
#define MBEDTLS_BASE64_C
#define MBEDTLS_BIGNUM_C
#define MBEDTLS_CCM_C
#define MBEDTLS_CIPHER_C
#define MBEDTLS_CTR_DRBG_C
#define MBEDTLS_DES_C
#define MBEDTLS_DHM_C
#define MBEDTLS_ECDH_C
#define MBEDTLS_ECDSA_C
#define MBEDTLS_ECP_C
#define MBEDTLS_ENTROPY_C
#define MBEDTLS_ERROR_C
#define MBEDTLS_GCM_C
#define MBEDTLS_HMAC_DRBG_C
#define MBEDTLS_LMS_C
#define MBEDTLS_MD_C
#define MBEDTLS_MD5_C
#define MBEDTLS_OID_C
#define MBEDTLS_PADLOCK_C
#define MBEDTLS_PEM_PARSE_C
#define MBEDTLS_PEM_WRITE_C
#define MBEDTLS_PK_C
#define MBEDTLS_PK_PARSE_C
#define MBEDTLS_PK_WRITE_C
#define MBEDTLS_PKCS7_C
#define MBEDTLS_PKCS12_C
#define MBEDTLS_PLATFORM_C
#define MBEDTLS_PSA_CRYPTO_C
#define MBEDTLS_RSA_C
#define MBEDTLS_SHA1_C
#define MBEDTLS_SHA224_C
#define MBEDTLS_SHA256_C
#define MBEDTLS_SHA384_C
#define MBEDTLS_SHA512_C
#define MBEDTLS_SHA3_C
#define MBEDTLS_SSL_CACHE_C
#define MBEDTLS_SSL_TICKET_C
#define MBEDTLS_SSL_CLI_C
#define MBEDTLS_SSL_SRV_C
#define MBEDTLS_SSL_TLS_C
#define MBEDTLS_THREADING_C
#define MBEDTLS_VERSION_C
#define MBEDTLS_X509_USE_C
#define MBEDTLS_X509_CRT_PARSE_C
#define MBEDTLS_X509_CRL_PARSE_C
#define MBEDTLS_X509_CSR_PARSE_C
#define MBEDTLS_X509_CREATE_C
#define MBEDTLS_X509_CRT_WRITE_C
#define MBEDTLS_X509_CSR_WRITE_C
#define MBEDTLS_ECP_WINDOW_SIZE 4 /**< Maximum window size used */
#define MBEDTLS_ECP_FIXED_POINT_OPTIM 1 /**< Enable fixed-point speed-up */
#define MBEDTLS_PLATFORM_CALLOC_MACRO _my_calloc /**< Default allocator macro to use, can be undefined. See MBEDTLS_PLATFORM_STD_CALLOC for requirements. */
#define MBEDTLS_PLATFORM_FREE_MACRO _mem_free /**< Default free macro to use, can be undefined. See MBEDTLS_PLATFORM_STD_FREE for requirements. */
#define MBEDTLS_PLATFORM_TIME_MACRO mbedtls_getSecsSinceEpoch /**< Default time macro to use, can be undefined. MBEDTLS_HAVE_TIME must be enabled */
#define MBEDTLS_PLATFORM_TIME_TYPE_MACRO uint32_t /**< Default time macro to use, can be undefined. MBEDTLS_HAVE_TIME must be enabled */
#define MBEDTLS_SSL_CACHE_DEFAULT_TIMEOUT 86400 /**< 1 day */
#define MBEDTLS_SSL_CACHE_DEFAULT_MAX_ENTRIES 50 /**< Maximum entries in cache */
#define MBEDTLS_SSL_IN_CONTENT_LEN 16384
#define MBEDTLS_SSL_OUT_CONTENT_LEN 16384
#define MBEDTLS_SSL_MAX_EARLY_DATA_SIZE 1024
#define MBEDTLS_SSL_TLS1_3_DEFAULT_NEW_SESSION_TICKETS 1