Supporting insecure protocols in RMCP+

[Brad Bishop]

> On Apr 23, 2018, at 2:47 PM, Vernon Mauery <vernon.mauery at linux.intel.com> wrote:
> 
>> Patch Set 4:
>> 
>>> Given that RMCP+ is already insecure, unless it is a requirement to support 1, 2, 15, and 16, you may just want to support 3 and 17.
>> 
>> 1,2,3 are marked as mandatory in the specification. It should be a community decision to revoke support for 1,2. If the community is ok, it will need additional code changes.
> 
> tl;dr IPMI is old; let's drop the most insecure parts
> 
> Opening this up to a wider audience. I would like some community consensus on how we should deal with parts of specifications that don't make sense anymore.
> 

I agree.

However, if someone came along and tried to add this back in
(proving that there is at least one user in the world),
I would let them (provided its opt-in behavior).

> Tables in section 13.28:
> (authentication algorithm support)
> 00h: RAKP-none        Mandatory (recommend dropping support)
> 01h: RAKP-HMAC-SHA1   Mandatory (good, but not best; keep for now)
> 02h: RAKP-HMAC-MD5    Optional (not implemented; do not implement)
> 03h: RAKP-HMAC-SHA256 Optional (implemented; best available)
> 
> (integrity algorithm support)
> 00h: none             Mandatory (recommend dropping support)
> 01h: HMAC-SHA1-96     Mandatory (good, but not best; keep for now)
> 02h: HMAC-MD5-128     Optional (not implemented; do not implement)
> 03h: MD5-128          Optional (not implemented; do not implement)
> 04h: HMAC-SHA256-128  Optional (implemented; best available)
> 
> (confidentiality algorithm support)
> 00h: none             Mandatory (recommend dropping support)
> 01h: AES-CBC-128      Mandatory (implemented; best available)
> 02h: xRC4-128         Optional (not implemented; do not implement)
> 03h: xRC4-40          Optional (not implemented; do not implement)
> 
> The IPMI spec was written in a time when computing resources were minimal and before some of the real security awareness started. And as such, it contains some legacy stuff that should really be dropped or at the very least deprecated.
> 
> The IPMI spec only says that we must implement certain authentication, integrity, and confidentiality algorithms, it does not explicitly say what cipher suites must be implemented. But, if we implement every cipher suite that is available with the required algorithms, we would implement cipher suites 0, 1, 2, and 3. And if we added in sha256 integrity and authentication, we add in 15, 16, and 17.
> 
> Just for comparison, DCMI 1.5 requires only 3, with 17 as recommended and 8 as optional. This is a step up from IPMI's security recommendations, but still not best. I would say that 3 and 17 should be required, with the recommendation that 3 be deprecated (or disabled at runtime) in favor of 17 only.
> 
> I think we can all agree that cipher suite 0 is poison. It is a gaping open door with bright lights saying, "Hack me!" I would argue that cipher suites 1 and 2 are not much better. We have the computing resources to perform better security, so we should do it. As web browsers move along, they deprecate and then disable old versions of SSL/TLS. We should do the same. Just because at one point in history it was fine to authenticate with plaintext passwords, does not mean we should continue to do so. If you know better, do better.
> 
> Even if end users come to us and say that they MUST have cipher suite 1 or 2, I would argue that we should tell them to update their infrastructure rather than re-implement old insecure protocols.
> 
> 
> --Vernon