Re: [dnsext] DNSSEC, robustness, and several DS records

["W.C.A. Wijngaards" <[e-mail]>]

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Hi,

On 05/11/2011 03:57 PM, Edward Lewis wrote:
> At 10:01 +0200 5/11/11, Stephane Bortzmeyer wrote:
>> But it seems there is an "exception". RFC 4509, section 3, says that
>> DS hashed with SHA-1 must be ignored when there is a DS for the same
>> key hashed with SHA-2. This is to avoid downgrade attacks.
> 
> The overriding policy is still "local policy rules."  It is fine for the

The policy that unbound uses for DS hash algorithm is this: it picks its
favorite (i.e. the strongest) algorithm from the set of available ones,
and ignores the others.  This works for algorithms other than SHA1 and
SHA2, and gives RFC 4509 behaviour for SHA1 and SHA2.

There would be algorithm protection if you checked all the available DS
hash algorithms.  But we did not implement this because RFC 4509 says
otherwise.

The favorite DS hash algorithm for unbound is the one with the highest
DS algorithm number.  This is an implementation trick.

Best regards,
   Wouter
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