[19187] in Kerberos_V5_Development
Re: Suppressing conf/integ flags in krb5 GSS tokens
daemon@ATHENA.MIT.EDU (Simo Sorce)
Mon Jun 1 10:46:48 2015
Message-ID: <1433169987.19096.251.camel@willson.usersys.redhat.com>
From: Simo Sorce <simo@redhat.com>
To: Nico Williams <nico@cryptonector.com>
Date: Mon, 01 Jun 2015 10:46:27 -0400
In-Reply-To: <1433166717.19096.250.camel@willson.usersys.redhat.com>
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On Mon, 2015-06-01 at 09:51 -0400, Simo Sorce wrote:
> On Sun, 2015-05-31 at 23:03 -0500, Nico Williams wrote:
> > On Sun, May 31, 2015 at 01:59:24PM -0400, Greg Hudson wrote:
> > > Comments?
> >
> > Heimdal's SPNEGO implementation neither checks the the GSS_C_INTEG_FLAG
> > ret_flag, nor requests it as a req_flag. Heimdal's SPNEGO discovers
> > integrity support by calling gss_get_mic(): if it returns GSS_S_UNAVAIL,
> > then integrity support is not provided, otherwise it is. Heimdal also
> > assumes that if a MIC is received then integrity support must be
> > available.
> >
> > I believe calling GSS_GetMIC() and GSS_VerifyMIC() even when
> > GSS_C_INTEG_FLAG is not set in ret_flags is perfectly permissible in
> > RFC2743.
>
> I think this is fine, and if you receive a MIC you have no other option
> (well, except fail).
>
> > Disabling the MIC in SPNEGO when GSS_C_INTEG_FLAG is not set in
> > ret_flags, combined with the new cred options, is likely (I think) to
> > fail to interop with Microsoft's SPNEGO when used in the application
> > protocol in question. It ought to fail to interop, but who know,
> > perhaps MSFT's SPNEGO will not require the MIC in this protocol because
> > it's running over TLS, but I'd not bet on it. The Heimdal approach
> > seems better.
>
> Keep in mind we tested this, with the patch we sent Greg.
> It works with all flags turned off and no special handling for MIC,
> today.
I take this back, thinking again, the code where we exercised this uses
its own SPNEGO layer :/
Simo.
--
Simo Sorce * Red Hat, Inc * New York
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