Add SHA256 and AES256 security levels for SNMP polling

[mikygee]

Hello,
At the moment only SHA128 and AES128 are supported.
Many devices now support AES256 and SHA256, they should be also used.
Regards

Additional informations
http://www.net-snmp.org/wiki/index.php/Strong_Authentication_or_Encryption

[netniV]

Unfortunately, this is one where as much as we really want this ourselves, we are reliant on the libraries out there and I don't believe that NetSNMP fully support it last I heard. @cigamit or @TheWitness may correct me on that as they follow them a lot better than I do.

[bmfmancini]

@netniV

Actually I think as of 5.8 it does

Question: Authentication

Does it support anything stronger than SHA1?
Answer

Yes. Net-SNMP 5.8 and later support all the authentication protocols defined in [RFC7860|https://tools.ietf.org/html/rfc7860], w hich are:

SHA-192
SHA-256
SHA-284
SHA-512

Question: Encryption

Does Net-SNMP support AES192 or AES256?
Answer

The short answer is Yes, starting with release 5.8 AES193 and AES256 are an optional configure option.

There are two separate parts to the long answer:

source:http://www.net-snmp.org/wiki/index.php/Strong_Authentication_or_Encryption

[TheWitness]

Yea, it's supported in the SNMP library for now. We were holding off on this till 1.3. Been really busy though. It's a small project, but involves both Cacti and Spine.

[TheWitness]

Interesting that there is a full php implementation of SNMP that covers this, which is pretty cool.

#3818