Re: [dnsext] Clarifying the mandatory algorithm rules

[Edward Lewis <[e-mail]>]

At 8:30 -0400 12/10/10, Brian Dickson wrote:

>One is, whether all signatures are of equal importance.
>
>I'd say, SEP-related signatures (DS signatures, DNSKEY signatures) are much
>more critical, and should receive maximum protection, performance
>notwithstanding.

RFC 4034, section 2.1.1 says this:

# Bit 15 of the Flags field is the Secure Entry Point flag, described in
# [RFC3757].  If bit 15 has value 1, then the DNSKEY record holds a key
# intended for use as a secure entry point.  This flag is only zone signing
# or debugging software as to the intended use of this DNSKEY record;
# validators MUST NOT alter their behavior during the signature validation
# process in any way based on the setting of this bit.

All signatures are equal.

>I'd also say,  the fewer labels there are, the more important, for the
>same or similar reasoning.  The higher up the food chain, the bigger the
>target painted on the zone.

An attack to "steal" from example.co.tld. will be more effective if 
just that is "taken out" than if "tld." is taken out.  Why?  Who do 
you think is better defended?  How many will "fight back" if the 
attack goes to tld's infrastructure?

>Should this be addressed? If so, how?

I've already spent more time on this theoretical topic than I will 
ever spend on it in reality.

Can someone could actually demonstrate/deliver two RRSets for a 
name/class/type that validated against the same signature.  Even for 
RSA/MD5.  (Yes, I know MD5 is "broken" but every case I've heard of 
involves large, unstructured data.  Within the constraints of the 
DNS/DNSSEC protocol elements, can it be done?)

The restriction to the same owner/class/type is because the forgery 
would have to be tied to the question asked, RFC 2181 considerations. 
I'd be curious what is the minimum number of RR's needed in the 
forged set.  (Note - if the original set has one A record, the 
forgery can have more, many more.  If the minimum needed is absurdly 
high, then we can discount the odds that the forged set would 
accepted.)

(Wish we had put the RR's in set count in the RRSIG.)

-- 
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Edward Lewis             
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