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Bug 1476013

Summary: Fix regression caused by CVE-2017-3142 fix (broken TSIG-secured transfers).
Product: Red Hat Enterprise Linux 7 Reporter: Thomas Gardner <thgardne>
Component: bindAssignee: Petr Menšík <pemensik>
Status: CLOSED ERRATA QA Contact: Petr Sklenar <psklenar>
Severity: high Docs Contact:
Priority: high    
Version: 7.5CC: pemensik, thozza
Target Milestone: rcKeywords: Patch
Target Release: ---   
Hardware: All   
OS: All   
Whiteboard:
Fixed In Version: bind-9.9.4-53.el7 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2018-04-10 11:56:55 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1420851, 1465928    
Attachments:
Description Flags
Modified upstream patch none

Description Thomas Gardner 2017-07-27 20:26:33 UTC
Description of problem:

Here, from the horse's mouth:

------------------------------------------------------------------------
Last week ISC issued special security patch releases of BIND to
address two TSIG issues (CVE-2017-3142 and CVE-2017-3143.)
Unfortunately in doing so we seem to have introduced a regression
which can cause interoperability issues with other DNS software.

RFC 2845 permits several alternatives for a server to return
AXFR (or IXFR) answers that span more than one message. According
to the RFC, the first and last message must be signed but signing
is optional for messages other than the first and last, so long as
at least every hundredth message is signed. BIND signs every outgoing
continuation message, as do some other DNS products, but the RFC does
not require this and some implementers have chosen differently.

Due to our changes for CVE-2017-3142 we have unintentionally caused
a problem with BIND's ability to receive an AXFR or IXFR in the case
where TSIG is used and not every message is signed. This causes
the latest releases of BIND to refuse TSIG-secured transfers and log
an error when BIND is receiving AXFR or IXFR data from a server that
does not sign every message if the AXFR or IXFR requires more than
two messages.

To clarify:

1. Zone transfer should still work properly when TSIG is not used.

2. Zone transfer should still work properly when TSIG *is* used
when transferring from a BIND master server or another server
that signs every message.

3. Problems may occur when transferring from another server if
TSIG is used *and* the AXFR or IXFR is more than two messages
in length *and* the master server does not sign every message.
NSD is an example of a popular DNS product that behaves in this
manner [note: NSD's behavior is in compliance with the requirements
of the RFC; it is BIND that has introduced a problem here.]

Replacement patch versions of BIND will be available shortly
to correct this regression.

We apologize for this error, which occurred because this
interoperability scenario was not properly anticipated in our testing.
New checks have been added to ensure that this aspect of zone transfer
behavior will be properly exercised in the testing done on future releases.

Michael McNally
ISC Security Officer
------------------------------------------------------------------------

Then, later from their release notes (7/21 18:08):

------------------------------------------------------------------------
Bug Fixes

    Fixed a bug that was introduced in an earlier development release which caused multi-packet AXFR and IXFR messages to fail validation if not all packets contained TSIG records; this caused interoperability problems with some other DNS implementations. [RT #45509]
------------------------------------------------------------------------

so it looks like they've fixed it.  I don't know how to track down a patch # for you, or I would.

Version-Release number of selected component (if applicable):

bind-9.9.4-50.el7_3.1

How reproducible:

100%

Steps to Reproduce:
1. Look at the case generated from customer.
2. Spend a couple hours verifying what he says is true, and (unsuccessfully) trying to track down a commit number for you.
3. File bug with what you've got.

Actual results:

Customer unhappy.

Expected results:

Customer not unhappy.

Additional info:

Comment 1 Petr Menšík 2017-08-01 13:04:11 UTC
Created attachment 1307570 [details]
Modified upstream patch

Comment 3 Petr Menšík 2017-08-01 13:16:24 UTC
Hi, thank you for tracking down the upstream commit. Link to upstream patch is https://source.isc.org/cgi-bin/gitweb.cgi?p=bind9.git;a=commit;h=2fc1b8102d4bf02162012c27ab95e98a7438bd8f

Comment 12 errata-xmlrpc 2018-04-10 11:56:55 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:0742