[ldns-users] ldns-signzone ECDSA random failure

Matt Smith ldns at xtaz.co.uk
Tue Aug 18 08:51:26 UTC 2015

On Aug 18 10:12, W.C.A. Wijngaards wrote:
>Thank you for the details, I have worked out that the shorter RRSIG is
>wrong.  It is generated because ldns is omitting leading zeroes when
>generating the signature encoding, but the RFC mandates equal length
>parts (of length curvebits / 8).
>The fix is in git and basically adds leading zeroes to the created RRSIG
>Because ecdsa signatures have a randomised component, this only
>happens when the leading bytes randomly happen to be zero.
>The ldns_convert_ecdsa_rrsig_asn12rdf is therefore not capable of
>generating good signatures, and is removed, replaced with
>ldns_convert_ecdsa_rrsig_asn1len2rdf that takes the curve length as a
>function call parameter.
>Best regards, Wouter

Hi, excellent! Thank you very much for this. I've applied that patch 
from git and tested signing a zone around 20 times now and have seen no 
evidence of any failures this time. So it looks like the patch works 
fine. Hopefully there are enough other changes in the pipeline to make a 
new release worthwhile soon which would contain this patch.


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