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Re: [saag] NSA bug in Windows 10

Benjamin Kaduk <kaduk@mit.edu> Sat, 18 January 2020 02:26 UTC

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Date: Fri, 17 Jan 2020 18:25:57 -0800
From: Benjamin Kaduk <kaduk@mit.edu>
To: Dan Brown <danibrown@blackberry.com>
Cc: Peter Gutmann <pgut001@cs.auckland.ac.nz>, Phillip Hallam-Baker <phill@hallambaker.com>, IETF SAAG <saag@ietf.org>
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Subject: Re: [saag] NSA bug in Windows 10
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On Fri, Jan 17, 2020 at 06:54:27PM +0000, Dan Brown wrote:
> 
> > -----Original Message-----
> > From: Benjamin Kaduk <kaduk@mit.edu>
> > >
> > > If my presumption above is correct, then it seems that this part of
> > > RFC3280 was not followed in this bug, since the parameters were taken
> from
> > an
> > > untrustworthy in-band delivery.   That said, I wonder if RFC3280
> adequately
> > > emphasized this point? Could it have used a MUST?
> > 
> > I remember reading something that involved taking an existing signature
> made
> > by a trusted root from a legitimate certificate issued by that root, and
> re-using
> > that signature with different domain parameters.  That would seem to imply
> > that the trusted root is properly being used, but the validation code for
> the
> > signatures in the chain was flawed.
> 
> Well, that attack does not match what I read.  
> 
> In what I read, a fake root cert is sent, and the receiver uses it.    Some
> claim the bug is an incomplete match between the fake and real root cert,
> but I claim the real bug is using the received cert at all. 

It seems that I had read too quickly or not read enough.
Thanks everyone for correcting me, and sorry for spreading confusion.

-Ben

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