[OpenAFS] Migrating away from single DES

Tue, 15 Sep 2020 13:33:25 -0400

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Hi Rainer,

The DES only limitation of the afs/cell@REALM service principal was
removed in the 2013 release of OpenAFS 1.4.15 and 1.6.5.  Since those
releases neither the server ticket key nor the session key are
restricted to the des-cbc-crc encryption type.  All cells should be
upgraded to current versions of OpenAFS on the servers and should rekey
the afs/cell@REALM service principal with the aes256-cts-hmac-sha1-96
encryption type.

This includes cells that have deployed gssklogd.  If the KeyFile
contains a des-cbc-crc key, the cell is vulnerable to the Brute Force
Attacks described by

  http://www.openafs.org/pages/security/OPENAFS-SA-2013-003.txt

Changing the service principal encryption type protects against this
brute force attack.  However, it is important to note that even when an
aes256-cts-hmac-sha1-96 session key is negotiated, the OpenAFS client
and server will derive from that key a 56-bit key to use for the fcrypt
encryption type used by rxkad for wire security.

Jeffrey Altman

On 9/15/2020 12:32 PM, r. l. (rainer.laatsch@t-online.de) wrote:
> The simplest solution: use=C2=A0 gssklog=C2=A0 of D.E.Engert.=C2=A0 The=
 token then
> comes from an AFS vlservers KeyFile
>=20
> and not from an entry afs/**@*** in some krb5kdc. Just run some gssklog=
d
> and switch from aklog to
>=20
> gssklog in your profiles. Some times ago, even CERN.ch used it.
>=20
> The original tarfile can still be found at
>=20
> =C2=A0 http://www.hep.man.ac.uk/u/masj/gssklog/
>=20
> or try my updated version at
>=20
> =C2=A0 http://95.217.219.185/ContribAFS/Gssklog-0.11.tar
>=20
> The binaries were done on ScientificLinux-6.10 with a newer KRB5 in
> /opt/krb5/
>=20
> and a static compilation of openafs (had to fix hcrypto and roken libs
> there)
>=20
>=20
> Best regards
>=20
> R. Laatsch
>=20
>=20
>=20
>=20
>=20
>=20
>=20
>=20
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>=20
> On 2020-09-14 10:32, ProbaNet SRLS wrote:
>> Hello!
>>
>> =C2=A0=C2=A0=C2=A0=C2=A0 Recent releases of krb5 (> 1.18) no longer su=
pport single des
>> encryption (the "allow_weak_crypto =3D yes" option in krb5.conf client=

>> side has no longer effect), so now we get this error with "aklog -d":
>>
>> ---
>>
>> Kerberos error code returned by get_cred : -1765328370
>> aklog: Couldn't get XXXXX AFS tickets:
>> aklog: KDC has no support for encryption type while getting AFS ticket=
s
>>
>> ---
>>
>> How should we proceed?
>>
>>
>> Stefano
>>
>> _______________________________________________
>> OpenAFS-info mailing list
>> OpenAFS-info@openafs.org
>> https://lists.openafs.org/mailman/listinfo/openafs-info
> _______________________________________________
> OpenAFS-info mailing list
> OpenAFS-info@openafs.org
> https://lists.openafs.org/mailman/listinfo/openafs-info

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fn:Jeffrey Altman
n:Altman;Jeffrey
org:AuriStor, Inc.
adr:;;255 W 94TH ST STE 6B;New York;NY;10025-6985;United States
email;internet:jaltman@auristor.com
title:CEO
tel;work:+1-212-769-9018
url:https://www.linkedin.com/in/jeffreyaltman/
version:2.1
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