Eap: Fix check for invaild message hadling

[Jojeker]

Hello :)

We want to submit some patches that target the EAP message parsing and the handling for authentication. There are three issues that we identified and fixed in this series:

1. An invalid message type (which leads to anullptr is not handled correctly for the authentication functions (e.g. NasMm::receiveAuthenticationRequestEap), since the IE might evalute to nullptr although the message is not valid. This leads to segmentation faults during execution.

2. An EAP message with invalid length fields (a length < 2 for attributes) leads to an unbounded read in readOctetString, since the last bound is smaller then the first bound.

3. They enum type bounds for EAP structs are not checked upon parsing, although they provide an early information on processing. This is relevant for parsing the concrete EAPAttributes.

We are happy to provide concrete pcap traces if necessary.

Cheers

[aligungr]

Thanks