[OpenAFS] OpenAFS Security Releases 1.8.2, 1.6.23 available --> butc & backup security update question --> why only root?

[Jeffrey Altman]

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On 9/27/2018 9:11 AM, Giovanni Bracco wrote:
> I have made some tests - ok it works - but I wonder why the key
> autentication method is allowed only to root user
>=20
>> -localauth
>> All butc RPCs require superuser authentication.
>> This option must be run as root, and server key material must be prese=
nt.
>=20
> Our backup scripts, which have been running on a dedicated server for
> many years, run under a dedicated user with administrative powers.
>=20
> Why the availability of a admin token is not sufficient to run butc in =
a
> secure way?
>=20
> Giovanni

A user token can be used to authenticate outgoing connections such as
those from butc to the buserver or the volserver.  It cannot be used to
authenticate incoming connections to butc from the backup coordinator
command ("backup" or "afsbackup" depending upon the packaging.)

The privilege escalation attack is possible because of butc accepting
unauthenticated "anonymous" requests that would then result in RPCs
being issued as a privileged identity to the buserver and the volserver.
 To close the security hole butc must authenticate all incoming RPCs.
To do so butc must have knowledge of the cell-wide key because without
knowledge of that key it cannot decrypt the AFS token presented by the
RPC issuer.

Jeffrey Altman



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fn:Jeffrey Altman
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email;internet:jaltman@auristor.com
title:Founder and CEO
tel;work:+1-212-769-9018
note;quoted-printable:LinkedIn: https://www.linkedin.com/in/jeffreyaltman=
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