oss-sec mailing list archives

Re: OpenSSH key blacklisting


From: Vincent Danen <vdanen () linsec ca>
Date: Fri, 16 May 2008 11:53:25 -0600

* [2008-05-16 21:18:54 +0400] Solar Designer wrote:

Are any other distros, besides Debian, Ubuntu, and derived ones, going
to implement key blacklisting in OpenSSH - or are considering it?

We are considering it for Openwall GNU/*/Linux, and if our effort would
be reused by others, or if others join us in developing and/or testing
the patch, this would be a reason for us to go for it.

I don't think we'll take the Debian/Ubuntu patch as-is.  Rather, we are
likely to use a trivial binary encoding/compression method for the
partial fingerprints.  We'd also use smaller partial fingerprints.  With
the approach I have in mind, it'd take around 4.55 bytes per key to
store 48-bit partial fingerprints, bringing the installed file size for
3 arch types and 2 key types/sizes in under 1 MB (or just over 1 MB for
3 key types/sizes).

We (Mandriva) have kinda sat back to see what other vendors are going to
do.  A few people have asked us to incorporate the Ubuntu patch, but the
stance I've taken so far is that if upstream openssh is going to do it,
then we will too.  Otherwise I don't think we will, unless a number of
other vendors are going to do so.

We did send an announcement with more info to our security-announce
mailing list to give our users a head's up, but didn't think we needed
to push this on our users since very few will likely be affected.

--
Vincent Danen @ http://linsec.ca/

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