tree a5d996e42fdd141de3239df34ec644324fa354ae
parent a1491fe74f7f7d8b42512957cf5f705bbd9cfe54
author Jaeden Amero <jaeden@patater.com> 1559737928 +0100
committer Jaeden Amero <jaeden@patater.com> 1559740169 +0100

ssl: Don't access non-existent encrypt_then_mac field

When MBEDTLS_SSL_ENCRYPT_THEN_MAC is enabled, but not
MBEDTLS_SSL_SOME_MODES_USE_MAC, mbedtls_ssl_derive_keys() and
build_transforms() will attempt to use a non-existent `encrypt_then_mac`
field in the ssl_transform.

    Compile [ 93.7%]: ssl_tls.c
    [Error] ssl_tls.c@865,14: 'mbedtls_ssl_transform {aka struct mbedtls_ssl_transform}' ha
s no member named 'encrypt_then_mac'
    [ERROR] ./mbed-os/features/mbedtls/src/ssl_tls.c: In function 'mbedtls_ssl_derive_keys'
:
    ./mbed-os/features/mbedtls/src/ssl_tls.c:865:14: error: 'mbedtls_ssl_transform {aka str
uct mbedtls_ssl_transform}' has no member named 'encrypt_then_mac'
         transform->encrypt_then_mac = session->encrypt_then_mac;
                  ^~

Change mbedtls_ssl_derive_keys() and build_transforms() to only access
`encrypt_then_mac` if `encrypt_then_mac` is actually present.

Add a regression test to detect when we have regressions with
configurations that do not include any MAC ciphersuites.

Fixes d56ed2491be9 ("Reduce size of `ssl_transform` if no MAC ciphersuite is enabled")