Subject: Re: [nfsv4] Re: [PATCH 9 of 16] nfsd4: relax new lock seqid check

From: Chuck Lever <[email-masked]>
Date: Wed, 30 Nov 2005 14:08:15 -0500

David Robinson wrote:
> I wouldn't put to much faith in security thru randomization,
> if you really care about security you will use strong authentication
> and integrity checks, so rogue interjection of seqids
> would not be possible even if the values are well known.
> Of course you can throw privacy as well to keep it secret.

this is not to prevent interjection of sequence IDs.

the idea of field randomization is to prevent a client from giving away 
information to anyone watching on the wire.  in fact it is the default 
policy of OpenBSD that, whether or not any known exploit exists, you 
should always use randomized data in protocol fields that contain 
arbitrary data.

Linux has also adopted this to some extent.  ephemeral ports are chosen 
at random, as are TCP ISNs.  there's no reason not to do the same for 
ULP's such as NFS.
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