Operational Notification: RPZ crashes (BIND 9.10)

AA-01265

Summary:

Numerous defects have been found in the BIND 9.10 implementation of Response Policy Zones (RPZ) which can lead to a crash of the named process.

Posting date: 
10 Jun 2015
Program Impacted: 
BIND
Versions affected: 

9.10.0 through 9.10.2 (inclusive)
The defect also affects the BIND 9 Subscription Edition, which is only available to ISC BIND Support customers; versions 9.9.3-S1 through 9.9.7-S1 (inclusive) are affected.

Description:

ISC has received multiple reports of named crashes related to handling of Response Policy Zones (RPZ) in BIND 9.10 including (but not limited to) reports from operators who are using the Spamhaus RPZ feed.

Our developers have analyzed the reported crashes (which are in the form of assertion failures, i.e., a controlled shutdown), and they have identified multiple defects in the handling of Response Policy Zones which are addressed by new patches.  These patches are being made available in coordination with this notification.

The most commonly-encountered crash happens when all of the following occur on a server with one or more slave RPZs:

  1. A slave RPZ zone transfer (IXFR) is initiated; and
  2. The transfer fails for any reason, and named falls back to AXFR.

Impact:

Only servers with RPZs are affected, most critically those with one or more slave RPZs.

Workarounds:

The only safe workaround would be to convert all "type slave" RPZs to "type master", and then to retrieve zone updates out-of-band.  This would avoid the more likely crashes, but the problems in the RPZ code would still exist, and could be manifested in unanticipated ways.

Solution:  Upgrade to the patched BIND 9.10.2-P1 release, provided with this Notification.  ISC BIND Subscription customers will want to upgrade to 9.9.7-S3, which was released on 2015-06-11.

Acknowledgements:  ISC would like to thank the several reporters for reporting this issue; with special mention of our friends at the Spamhaus Project for their kind assistance in troubleshooting.

Do you still have questions?  Questions regarding this advisory should go to support@isc.org

Note: ISC patches only currently supported versions: http://www.isc.org/software/bind/versions. In this case the EOL versions were not affected.

ISC Disclosure Policies:  Additional information on our Operational Notifications can be found at: https://www.isc.org/software/notifications, and Phased Disclosure Process at: https://www.isc.org/security-vulnerability-disclosure-policy

This Knowledge Base article https://kb.isc.org/article/AA-01265 is the complete and official operational notification document.

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