Add fallback to non-compliant truncated HMAC for compatibiltiy
In case truncated HMAC must be used but the Mbed TLS peer hasn't been updated
yet, one can use the compile-time option MBEDTLS_SSL_TRUNCATED_HMAC_COMPAT to
temporarily fall back to the old, non-compliant implementation of the truncated
HMAC extension.
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index fa72454..bc77b21 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -77,6 +77,10 @@
#error "MBEDTLS_DHM_C defined, but not all prerequisites"
#endif
+#if defined(MBEDTLS_SSL_TRUNCATED_HMAC_COMPAT) && !defined(MBEDTLS_SSL_TRUNCATED_HMAC)
+#error "MBEDTLS_SSL_TRUNCATED_HMAC_COMPAT defined, but not all prerequisites"
+#endif
+
#if defined(MBEDTLS_CMAC_C) && \
!defined(MBEDTLS_AES_C) && !defined(MBEDTLS_DES_C)
#error "MBEDTLS_CMAC_C defined, but not all prerequisites"