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Re: [Qemu-devel] [PATCH v4] vnc: disable VNC password authentication (se

From: Daniel P. Berrange
Subject: Re: [Qemu-devel] [PATCH v4] vnc: disable VNC password authentication (security type 2) when in FIPS mode
Date: Tue, 31 Jul 2012 21:12:57 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

On Tue, Jul 31, 2012 at 02:52:07PM -0500, Anthony Liguori wrote:
> Paul Moore <address@hidden> writes:
> > On Friday, June 08, 2012 05:38:12 PM Paul Moore wrote:
> >> FIPS 140-2 requires disabling certain ciphers, including DES, which is used
> >> by VNC to obscure passwords when they are sent over the network.  The
> >> solution for FIPS users is to disable the use of VNC password auth when the
> >> host system is operating in FIPS mode.
> >> 
> >> This patch causes QEMU to emit a message to stderr when the host system is
> >> running in FIPS mode and a VNC password was specified on the commend line.
> >> If the system is not running in FIPS mode, or is running in FIPS mode but
> >> VNC password authentication was not requested, QEMU operates normally.
> >> 
> >> Signed-off-by: Paul Moore <address@hidden>
> >
> > Hi Anthony,
> >
> > Any word on this patch?  Other than Daniel Berrange's reviewed-by tag, the 
> > discussion of the v4 patch has been quiet and I think we addressed all the 
> > other remaining issues in the discussion attached to the v2 patch
> > posting.
> I asked for the specific language in FIPS mandating this.  I don't see
> any other VNC server implementing a check like this.  I would rather do
> this in a more user friendly fashion like make it a config file option
> that a user can set while in fips mode.

The FIPS standard doesn't refer to particular applications like VNC.
As Paul says earlier, FIP 140-2 requires that DES (and certain other
ciphers) not be used in any applications which are running in a FIPS
compliant environment. Since VNC auth uses DES, this auth scheme
cannot be permitted in a FIPS environment.

The reason no other VNC server does this is almost certainly because
none of their developers have ever tried to have their code work in
a FIPS environment, so I don't think that's a relevant comparison.

I'm not really sure what addding more configuration options gains
us here. The choice of auth mode is already configurable. This patch
is about ensuring that the user is not allowed to configure it, if
FIPS mode is in effect (as indicated by the kernels syfs tunable).
So in fact adding config params doesn't really address this.

The proposed patch is already very straightforward, is using the
official interface exposed by the upstream kernel to userspace &
has negligable maintenence burden IMHO.

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