.. Copyright (C) Internet Systems Consortium, Inc. ("ISC")
..
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Notes for BIND 9.20.5
---------------------

Security Fixes
~~~~~~~~~~~~~~

- DNS-over-HTTPS flooding fixes. :cve:`2024-12705`

  Fix DNS-over-HTTPS implementation issues that arise under heavy
  query load. Optimize resource usage for :iscman:`named` instances that
  accept queries over DNS-over-HTTPS.

  Previously, :iscman:`named` processed all incoming HTTP/2 data at
  once, which could overwhelm the server, especially when dealing with
  clients that sent requests but did not wait for responses. That has been
  fixed. Now, :iscman:`named` handles HTTP/2 data in smaller chunks and
  throttles reading until the remote side reads the response data. It
  also throttles clients that send too many requests at once.

  In addition, :iscman:`named` now evaluates excessive streams opened by
  clients that include no DNS data, which is considered "flooding." It
  logs these clients and drops connections from them. :gl:`#4795`

  In some cases, :iscman:`named` could leave DNS-over-HTTPS
  connections in the `CLOSE_WAIT` state indefinitely. That has also been
  fixed. :gl:`#5083`

  ISC would like to thank Jean-François Billaud for his assistance with
  investigating this issue.

- Limit additional section processing for large RDATA sets.
  :cve:`2024-11187`

  When answering queries, don't add data to the additional section if
  the answer has more than 13 names in the RDATA. This limits the number
  of lookups into the database(s) during a single client query, reducing
  the query-processing load. :gl:`#5034`

  ISC would like to thank Toshifumi Sakaguchi for bringing this
  vulnerability to our attention.

New Features
~~~~~~~~~~~~

- Add Extended DNS Error Code 22 - No Reachable Authority.

  When the resolver is trying to query an authoritative server and
  eventually times out, a SERVFAIL answer is given to the client. Add
  the Extended DNS Error Code 22 - No Reachable Authority to the
  response. :gl:`#2268`

- Add a new option to configure the maximum number of outgoing queries
  per client request.

  The configuration option :any:`max-query-count` sets how many outgoing
  queries per client request are allowed. The existing
  :any:`max-recursion-queries` value is the number of permissible queries for a
  single name and is reset on every CNAME redirection. This new option
  is a global limit on the client request. The default is 200.

  The default for :any:`max-recursion-queries` is changed from 32 to
  50. This allows :any:`named` to send a few more queries
  while looking up a single name. :gl:`#4980` :gl:`#4921`

- Use the Server Name Indication (SNI) extension for all outgoing TLS
  connections.

  This improves compatibility with other DNS server software.
  :gl:`#5099`

Feature Changes
~~~~~~~~~~~~~~~

- Performance optimization for NSEC3 lookups introduced in BIND 9.20.2 was
  reverted to avoid risks associated with a complex code change. :gl:`#5108`

- The configuration clauses ``parental-agents`` and ``primaries`` are renamed to
  :any:`remote-servers`.

  The top blocks ``primaries`` and ``parental-agents`` are no longer
  preferred and should be renamed to :any:`remote-servers`. The zone
  statements :any:`parental-agents` and :any:`primaries` are still used, and may
  refer to any :any:`remote-servers` top block. :gl:`#4544`

- Add `none` parameter to :namedconf:ref:`query-source` and
  :namedconf:ref:`query-source-v6` to disable IPv4 or IPv6 upstream queries but
  allow listening to queries from clients on IPv4 or IPv6. :gl:`#4981`

Bug Fixes
~~~~~~~~~

- Fix :iscman:`nsupdate` hang when processing a large update.

  To mitigate DNS flood attacks over a single TCP connection, throttle
  the connection when the other side does not read the data. Throttling
  should only occur on server-side sockets, but erroneously also
  happened for :iscman:`nsupdate`, which acts as a client. When
  :iscman:`nsupdate` started throttling the connection, it never
  attempted to read again. This has been fixed. :gl:`#4910`

- Fix possible assertion failure when reloading server while processing
  update policy rules. :gl:`#5006`

- Preserve cache across reconfig when using :any:`attach-cache`.

  When the :any:`attach-cache` option is used in the ``options`` block with an
  arbitrary name, it causes all views to use the same cache. Previously,
  this configuration caused the cache to be deleted and a new cache
  to be created every time the server was reconfigured. This has been fixed.
  :gl:`#5061`

- Resolve the spurious drops in performance due to glue cache.

  For performance reasons, the returned glue records are cached on the
  first use.  The current implementation could randomly cause a
  performance drop and increased memory use.  This has been fixed.
  :gl:`#5064`

- Fix :iscman:`dnssec-signzone` signing non-DNSKEY RRsets with revoked keys.

  :any:`dnssec-signzone` was using revoked keys for signing RRsets other than
  DNSKEY.  This has been corrected. :gl:`#5070`

- Fix improper handling of unknown directives in ``resolv.conf``.

  The line after an unknown directive in ``resolv.conf`` could accidentally be
  skipped, potentially affecting :iscman:`dig`, :iscman:`host`,
  :iscman:`nslookup`, :iscman:`nsupdate`, or :iscman:`delv`. This has been
  fixed. :gl:`#5084`

- Fix response policy zones and catalog zones with an ``$INCLUDE`` statement
  defined.

  Response policy zones (RPZ) and catalog zones were not working
  correctly if they had an ``$INCLUDE`` statement defined. This has been
  fixed. :gl:`#5111`