- Issued:
- 2010-04-20
- Updated:
- 2010-04-20
RHBA-2010:0357 - Bug Fix Advisory
Synopsis
krb5 bug fix update
Type/Severity
Bug Fix Advisory
Topic
Updated krb5 packages that improve cross-realm authentication are now
available for Red Hat Enterprise Linux 5.4 Extended Update Support.
Description
Kerberos V5 is a trusted-third-party network authentication system, which
can improve your network's security by eliminating the insecure practice of
cleartext passwords.
This update adds the following bug fix:
- when a Kerberos client seeks tickets for use with a service, it must
contact the Key Distribution Center (KDC) to obtain them. The client must
also determine which realm the service belongs to and it typically does
this with a combination of client configuration detail, DNS information and
guesswork.
If the service belongs to a realm other than the client's, cross-realm
authentication is required. Using a combination of client configuration and
guesswork, the client determines the trust relationship sequence which
forms the trusted path between the client's realm and the service's realm.
This may include one or more intermediate realms.
Anticipating the KDC has better knowledge of extant trust relationships,
the client then requests a ticket from the service's KDC, indicating it
will accept guidance from the service's KDC by setting a special flag in
the request. A KDC which recognizes the flag can, at its option, return a
ticket-granting ticket for the next realm along the trust path the client
should be following.
If the ticket-granting ticket returned by the service's KDC is for use with
a realm the client has already determined was in the trusted path, the
client accepts this as an optimization and continues. If, however, the
ticket is for use in a realm the client is not expecting, the client
responds incorrectly: it treats the case as an error rather than continuing
along the path suggested by the service's KDC.
For this update, the krb5 1.7 modifications which allow the client to trust
such KDCs to send them along the correct path, resulting in the client
obtaining the tickets it originally desired, were backported to krb 1.6.1
(the version shipped with Red Hat Enterprise Linux 5.4). (BZ#574387)
All users requiring consistent cross-realm authentication should install
this update, which addresses this issue.
Solution
Before applying this update, make sure all previously-released errata
relevant to your system have been applied.
This update is available via the Red Hat Network. Details on how to
use the Red Hat Network to apply this update are available at
http://kbase.redhat.com/faq/docs/DOC-11259
Affected Products
- Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.4 x86_64
- Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.4 ia64
- Red Hat Enterprise Linux for x86_64 - Extended Update Support 5.4 i386
- Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 5.4 s390x
- Red Hat Enterprise Linux for Power, big endian - Extended Update Support 5.4 ppc
Fixes
- BZ - 574387 - [RFE] Backport referral-chasing code within krb5-1.7 to RHEL5
CVEs
(none)
References
(none)
The Red Hat security contact is secalert@redhat.com. More contact details at https://access.redhat.com/security/team/contact/.