Fwd: Operational Notification: Extremely large zone transfers can result in corrupted journal files or server process termination

[Klaus Darilion]

What is an "extraordinarily large zone transfer"? We do have regularly 
AXFR and IXFRs around 2GB. Is this "extraordinarily large"?

regards
Klaus



-------- Weitergeleitete Nachricht --------
Betreff: 	Operational Notification: Extremely large zone transfers can 
result in corrupted journal files or server process termination
Datum: 	Wed, 4 Jul 2018 17:41:10 -0800
Von: 	Michael McNally <mcnally at isc.org>
An: 	bind-announce at lists.isc.org



Summary:

    In versions of BIND released prior to July 2018 (before BIND
    9.9.13, 9.10.8, 9.11.4, 9.12.2, and BIND 9.13.1) it is possible
    for extraordinarily large zone transfers to cause several related
    problems, with possible outcomes including corrupted journal
    files or server exit due to assertion failure.

Posting date:        03 July 2018
Program Impacted:    BIND
Versions affected:   9.0.x -> 9.8.8, 9.9.0 -> 9.9.12, 9.10.0 -> 9.10.7,
                      9.11.0 -> 9.11.3, 9.12.0 -> 9.12.1, and versions
                      9.13.0 -> 9.13.1 of the 9.13 development branch

Description:

    A problem in named can potentially lead to corrupted journal
    files when handling extraordinarily large zone transfers.

Impact:

    This problem potentially affects authoritative servers providing
    slave service for zones if the server accepts zone data via
    incremental zone transfer (IXFR) from a master source or if a
    large zone transfer (AXFR) is received and ixfr-from-differences
    is not set to "no" (the default setting is "yes", and possible
    values are "yes", "no", "slave", and "master").

    We warned of a similar class of problems in 2016 in this previous
    Operational Notification "A party that is allowed control over
    zone data can overwhelm a server by transferring huge quantities
    of data." (https://kb.isc.org/article/AA-01390)

Workarounds:

    Like any unvalidated input, zone transfers are a potential source
    of risk for servers under any circumstances.  BIND therefore
    supports a variety of mechanisms to control zone transfer
    permissions.  Permission to transfer can be restricted to trusted
    servers using IP-address-based ACLs or shared secrets (TSIG keys)
    or both.  Under most circumstances a slave server should not
    encounter this defect when receiving data from a trusted server,
    but it can be prevented entirely by forbidding incremental zone
    transfer as a zone data transfer mechanism.  It may be preferable
    to instead set a reasonable limit for the number of records which
    may be in a zone (using the max-records parameter) which should
    also prevent accidentally encountering this defect.

    Servers which must accept zone data from untrusted sources (for
    example, when seconding zones for other parties) are at slightly
    higher risk if a party decides to deliberately feed a dangerously
    large zone transfer.  Operators of servers which must accept
    untrusted zone data should consider limiting zone size using
    max-records, setting "ixfr-from-differences no;", or upgrading
    to a version of BIND which will reject dangerously large transfers.

Active exploits:

    No known active exploits.

Solution:

    It is our opinion that most customers do not need to worry about
    this issue unless they accept zone data via zone transfer from
    untrusted sources, but we have included changes in upcoming
    maintenance releases of BIND which will prevent the condition
    from being reached.

    Maintenance releases of BIND issued on or after 4 July 2018 will
    contain change #4984, which will cause BIND to reject an
    extraordinarily large IXFR if it is potentially large enough to
    corrupt the journal file. These release candidates are available
    now via https://www.isc.org/downloads and the change will be
    included in future versions of BIND

     BIND 9 version 9.9.13rc2
     BIND 9 version 9.10.8rc2
     BIND 9 version 9.11.4rc2
     BIND 9 version 9.12.2rc2


Do you still have questions?  Questions regarding this advisory
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If you are unable to use encrypted email, you may also report new
issues at: https://www.isc.org/community/report-bug/.

Note:

    ISC patches only currently supported versions. When possible we
    indicate EOL versions affected.  (For current information on
    which versions are actively supported, please see
    http://www.isc.org/downloads/).

ISC Security Vulnerability Disclosure Policy:

    Details of our current security advisory policy and practice can
    be found here: https://kb.isc.org/article/AA-00861

This Knowledge Base article https://kb.isc.org/article/AA-01627
is the complete and official security advisory document.

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