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")
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 56e9c8b..d9e777d 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -953,7 +953,8 @@
MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> derive keys" ) );
-#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC)
+#if defined(MBEDTLS_SSL_ENCRYPT_THEN_MAC) && \
+ defined(MBEDTLS_SSL_SOME_MODES_USE_MAC)
transform->encrypt_then_mac = session->encrypt_then_mac;
#endif
transform->minor_ver = ssl->minor_ver;