Re: [Sidrops] trying to limit RP processing variability

Martin Hoffmann <martin@opennetlabs.com> Thu, 16 April 2020 15:55 UTC

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Date: Thu, 16 Apr 2020 17:55:31 +0200
From: Martin Hoffmann <martin@opennetlabs.com>
To: "Job Snijders" <job@ntt.net>
Cc: sidrops@ietf.org
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Subject: Re: [Sidrops] trying to limit RP processing variability
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Job Snijders wrote:
> On Thu, Apr 16, 2020, at 15:30, Randy Bush wrote:
> > >>> An attacker who can delete files can as easily replace them with
> > >>> something else with the same result.    
> > >> not really.  
> > > I cannot think of a case where an attack can manipulate the rsync
> > > exchange, impersonate the rsync server, or manipulate the file
> > > system of the legitimate rsync server in such a way that they can
> > > signal to an rsync client to delete existing files but not to
> > > replace them partially or completely. 
> > > 
> > > What am I missing?  
> > 
> > 6486 4.2
> > 
> >    fileList:
> >       This field is a sequence of FileAndHash objects.  There is one
> >       FileAndHash entry for each currently valid signed object that
> > has been published by the authority (at this publication point).
> > Each FileAndHash is an ordered pair consisting of the name of the
> > file in the repository publication point (directory) that contains
> > the object in question and a hash of the file's contents.
> >                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^  
> 
> I think I see an instance of miscommunication:
> 
> I think Martin's perspective is that whether the files are deleted or
> modified by MITM, the RP outcome is the same: the PP has to be
> tossed. I don't think Martin suggested that files can trivially be
> replaced, just that deletion or tampering have the same effect. 
> 
> Right?

Correct. This was solely about synchronisation of a publication point,
not yet about validation.

Kind regards,
Martin