The official guide for Mbed TLS to migrate from version 2.x to version 3.0 or greater can be found `here <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/docs/3.0-migration-guide.md>`__.
- Direct access to fields of structures (``struct`` types) declared in public headers is no longer supported.
- Appropriate accessor functions (getter/setter) must be used for the same. A temporary workaround would be to use ``MBEDTLS_PRIVATE`` macro (**not recommended**).
- For more details, refer to the official guide `here <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/docs/3.0-migration-guide.md#most-structure-fields-are-now-private>`__.
- The functions ``mbedtls_*_ret()`` (related to MD, SHA, RIPEMD, RNG, HMAC modules) was renamed to replace the corresponding functions without ``_ret`` appended and updated return value.
- For more details, refer to the official guide `here <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/docs/3.0-migration-guide.md#deprecated-functions-were-removed-from-hashing-modules>`__.
Following are some of the important config options deprecated by this update. The configs related to and/or dependent on these have also been deprecated.
-``MBEDTLS_SSL_PROTO_SSL3`` : Support for SSL 3.0
-``MBEDTLS_SSL_PROTO_TLS1`` : Support for TLS 1.0
-``MBEDTLS_SSL_PROTO_TLS1_1``: Support for TLS 1.1
-``MBEDTLS_SSL_PROTO_DTLS`` : Support for DTLS 1.1 (Only DTLS 1.2 is supported now)
-``MBEDTLS_DES_C`` : Support for 3DES ciphersuites
-``MBEDTLS_RC4_MODE`` : Support for RC4-based ciphersuites
..note:: This list includes only major options configurable through ``idf.py menuconfig``. For more details on deprecated options, refer to the official migration guide.
The Diffie-Hellman Key Exchange modes have now been disabled by default due to security risks (see warning text `here <https://github.com/espressif/mbedtls/blob/9bb5effc3298265f829878825d9bd38478e67514/include/mbedtls/dhm.h#L20>`__). Related configs are given below:
-``MBEDTLS_DHM_C`` : Support for the Diffie-Hellman-Merkle module
-``MBEDTLS_KEY_EXCHANGE_DHE_PSK`` : Support for Diffie-Hellman PSK (pre-shared-key) TLS authentication modes
-``MBEDTLS_KEY_EXCHANGE_DHE_RSA`` : Support for cipher suites with the prefix ``TLS-DHE-RSA-WITH-``
..note:: During the initial step of the handshake (i.e. ``client_hello``), the server selects a cipher from the list that the client publishes. As the DHE_PSK/DHE_RSA ciphers have now been disabled by the above change, the server would fall back to an alternative cipher; if in a rare case, it does not support any other cipher, the handshake would fail. To retrieve the list of ciphers supported by the server, one must attempt to connect with the server with a specific cipher from the client-side. Few utilities can help do this, e.g. ``sslscan``.
:cpp:func:`esp_crt_bundle_set()` API now requires one additional argument named ``bundle_size``. The return type of the API has also been changed to :cpp:type:`esp_err_t` from ``void``.
- The function :cpp:func:`esp_https_ota` now requires pointer to :cpp:type:`esp_https_ota_config_t` as argument instead of pointer to :cpp:type:`esp_http_client_config_t`.
The :cpp:type:`esp_tls_t` has now been made completely private. You cannot access its internal structures directly. Any necessary data that needs to be obtained from the esp-tls handle can be done through respective getter/setter functions. If there is a requirement of a specific getter/setter function please raise an issue on ESP-IDF.
The list of newly added getter/setter function is as as follows:
..list::
*:cpp:func:`esp_tls_get_ssl_context` - Obtain the ssl context of the underlying ssl stack from the esp-tls handle.
Function deprecations and recommended alternatives
- The function :cpp:func:`esp_tls_conn_http_new` has now been termed as deprecated. Please use the alternative function :cpp:func:`esp_tls_conn_http_new_sync` (or its asynchronous :cpp:func:`esp_tls_conn_http_new_async`). Note that the alternatives need an additional parameter :cpp:type:`esp_tls_t` which has to be initialized using the :cpp:func:`esp_tls_init` function.
