Use new EVP_MAC API for HMAC implementation

Use new EVP_MAC API for HMAC implementation

The old API is deprecated in OpenSSL 3.0 and the new API does not yet
exist in OpenSSL 1.1. Emulating the new API would be more complex than
just having two implementations. So this switches to a new hmac
implementation for OpenSSL 3.0.

Unfortunately the new API does not have an easy to reset an HMAC,
so we need to keep the key around to emulate a reset functionality.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Max Fillinger <maximilian.fillinger@foxcrypto.com>
Message-Id: <20211019183127.614175-2-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg23013.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>