Re: [v6ops] [EXTERNAL] Re: Improving ND security

Fernando Gont <fernando@gont.com.ar> Mon, 03 August 2020 18:53 UTC

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To: "Templin (US), Fred L" <Fred.L.Templin@boeing.com>, "Pascal Thubert (pthubert)" <pthubert@cisco.com>
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From: Fernando Gont <fernando@gont.com.ar>
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Subject: Re: [v6ops] [EXTERNAL] Re: Improving ND security
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Hi, Fred,

On 3/8/20 13:45, Templin (US), Fred L wrote:
[....]
>> This message was sent from outside of Boeing. Please do not click links or open attachments unless you recognize the sender and
>> know that the content is safe.
>> On 3/8/20 11:22, Templin (US), Fred L wrote:
>>> Here’s another think about SEND. RFC3971 SEND says that it works in
>>> conjunction with Cryptographically Generated addresses (CGA) per RFC3972. But, CGAs are
>>> cumbersome to work with as the source and destination addresses of IPv6 packets,
>>> and SEND hints that it can be used without CGA but does not tell how to do so.
>>
>> Of the top of my head, CGAs are a core part of send.
> 
> That is fine; we can accommodate CGAs in OMNI, cumbersome as they are.
> I have this on my TODO list for after the adoption call.

Why "cumbersome"?



>>> But then, RFC4380 offers a “poor-man’s” alternative to SEND/CGA. It
>>> places a message authentication code in the encapsulation headers of IPv6 ND messages so
>>> that the messages can pass a rudimentary authentication check.
>>
>> You mean the Teredo spec? If so, I don't think it includes any sort of
>> poor-man's SEND-CGA.
> 
> It provides for message authentication, 

But what's special about SEND/CGAs is that they tie the address to a key...


> and it is widely-deployed which suggests
> to me that the vendors who support it believe it is secure. 

I'm sure others probably know better, but... I think Teredo is mostly MS 
+ Miredo. (when it comes to implementation)

And Re: deployment, IIRC Teredo has been phased out.



> So, if it is secure enough for RFC4380, then shouldn't it also be secure enough for OMNI?

I believe Auth in Teredo is a totally different thing from SEND/CGAs.

Regarding OMIN, I Haven read the draft/spec, yet...




>>> So someone with
>>> security experience please help me out here – is RFC4380 authentication an acceptably
>>> secure  replacement for SEND/CGA that might be easier to work with and less
>>> cumbersome?
>>
>> Nope. Tee point of CGAs is that they allow you to prove address
>> ownership. There's nothing in RFC4380 that provides the same or similar
>> functionality.
> 
> Why do we have to prove address ownership

Well, that's one of the goals of SEND/CGAs. :-)


> and use a whacky address format like CGA?

The *address format* is not really whacky. At the end of the day, it's a 
random number, with the specific property that it's part of the hash of 
a public key.

looking at a CGA, you probably wouldn't be able to tell CGA from RFC7217.



> There is nothing in the OMNI spec that needs or wants CGAs in any fashion
> unless they are absolutely required for security. Isn't it enough to prove message
> authentication using the mechanisms of RFC4380 without having to accommodate
> the excess baggage of CGAs??

Both are different things.

One thing is to authenticate the contents of a message. And a different 
one is to be able to tell that one specific host is "authorized" to use 
one specific address...


-- 
Fernando Gont
e-mail: fernando@gont.com.ar || fgont@si6networks.com
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1