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Unbound 1.19.3

This release has a number of bug fixes. The CNAME synthesized for a DNAME record uses the original TTL, of the DNAME record, and that means it can be cached for the TTL, instead of 0.

There is a fix that when a message was stored in cache, but one of the RRsets was not updated due to cache policy, it now restricts the message TTL if the cache version of the RRset has a shorter TTL. It avoids a bug where the message is not expired, but its contents is expired.

For dnstap, it logs type DoH and DoT correctly, if that is used for the message.

The b.root-servers.net address is updated in the default root hints.

When performing retries for failed sends, a retry at a smaller UDP size is now not performed when that attempt is not actually smaller, and at defaults, since the flag day changes, it is the same size. This makes it skip the step, it is useless because there is no reduction in size.

Clients with a valid DNS Cookie will bypass the ratelimit, if one is set. The value from ip-ratelimit-cookie is used for these queries.

Furthermore there is a fix to make correct EDE Prohibited answers for access control denials, and a fix for EDNS client subnet scope zero answers.

Features:

• Merge PR #973: Use the origin (DNAME) TTL for synthesized CNAMEs as per RFC 6672.

Bug Fixes:

• Fix unit test parse of origin syntax.
• Use 127.0.0.1 explicitly in tests to avoid delays and errors on newer systems.
• Fix #964: config.h.in~ backup file in release tar balls.
• Merge #968: Replace the obsolescent fgrep with grep -F in tests.
• Merge #971: fix 'WARNING: Message has 41 extra bytes at end'.
• Fix #969: [FR] distinguish Do53, DoT and DoH in the logs.
• Fix dnstap that assertion failed on logging other than UDP and TCP traffic. It lists it as TCP traffic.
• Fix to sync the tests script file common.sh.
• iana portlist update.
• Updated IPv4 and IPv6 address for b.root-servers.net in root hints.
• Update test script file common.sh.
• Fix tests to use new common.sh functions, wait_logfile and kill_from_pidfile.
• Fix #974: doc: default number of outgoing ports without libevent.
• Merge #975: Fixed some syntax errors in rpl files.
• Fix root_zonemd unit test, it checks that the root ZONEMD verifies, now that the root has a valid ZONEMD.
• Update example.conf with cookie options.
• Merge #980: DoH: reject non-h2 early. To fix #979: Improve errors for non-HTTP/2 DoH clients.
• Merge #985: Add DoH and DoT to dnstap message.
• Fix #983: Sha1 runtime insecure change was incomplete.
• Remove unneeded newlines and improve indentation in remote control code.
• Merge #987: skip edns frag retry if advertised udp payload size is not smaller.
• Fix unit test for #987 change in udp1xxx retry packet send.
• Merge #988: Fix NLnetLabs#981: dump_cache truncates large records.
• Fix to link with -lcrypt32 for OpenSSL 3.2.0 on Windows.
• Fix to link with libssp for libcrypto and getaddrinfo check for only header. Also update crosscompile to remove ssp for 32bit.
• Merge #993: Update b.root-servers.net also in example config file.
• Update workflow for ports to use newer openssl on windows compile.
• Fix warning for windres on resource files due to redefinition.
• Fix for #997: Print details for SSL certificate failure.
• Update error printout for duplicate trust anchors to include the trust anchor name (relates to #920).
• Update message TTL when using cached RRSETs. It could result in non-expired messages with expired RRSETs (non-usable messages by Unbound).
• Merge #999: Search for protobuf-c with pkg-config.
• Fix #1006: Can't find protobuf-c package since #999.
• Fix documentation for access-control in the unbound.conf man page.
• Merge #1010: Mention REFUSED has the TC bit set with unmatched allow_cookie acl in the manpage. It also fixes the code to match the documentation about clients with a valid cookie that bypass the ratelimit regardless of the allow_cookie acl.
• Document the suspend argument for process_ds_response().
• Move github workflows to use checkoutv4.
• Fix edns subnet replies for scope zero answers to not get stored in the global cache, and in cachedb, when the upstream replies without an EDNS record.
• Fix for #1022: Fix ede prohibited in access control refused answers.
• Fix unbound-control-setup.cmd to use 3072 bits so that certificates are long enough for newer OpenSSL versions.
• Fix TTL of synthesized CNAME when a DNAME is used from cache.
• Fix unbound-control-setup.cmd to have CA v3 basicConstraints, like unbound-control-setup.sh has.

Unbound 1.19.2

This security release fixes CVE-2024-1931.

NLnet Labs Unbound version 1.18.0 up to and including version 1.19.1 contain a vulnerability that can cause denial of service by a certain code path that can lead to an infinite loop.

Unbound 1.18.0 introduced a feature that removes EDE records from responses with size higher than the client's advertised buffer size. Before removing all the EDE records however, it would try to see if trimming the extra text fields on those records would result in an acceptable size while still retaining the EDE codes. Due to an unchecked condition, the code that trims the text of the EDE records could loop indefinitely. This happens when Unbound would reply with attached EDE information on a positive reply and the client's buffer size is smaller than the needed space to include EDE records.

The vulnerability can only be triggered when the 'ede: yes' option is used; non default configuration.

From version 1.19.2 on, the code is fixed to avoid looping indefinitely.

We would like to thank Fredrik Pettai and Patrik Lundin from SUNET for notifying us about the issue and working with us to identify the vulnerability.

Bug Fixes:

• Fix CVE-2024-1931, Denial of service when trimming EDE text on positive replies.

Unbound 1.19.1

This security release fixes two DNSSEC validation vulnerabilities: CVE-2023-50387 (referred here as the KeyTrap vulnerability) and CVE-2023-50868 (referred here as the NSEC3 vulnerability).

The KeyTrap vulnerability works by using a combination of Keys (also colliding Keys), Signatures and number of RRSETs on a malicious zone. Answers from that zone can force a DNSSEC validator down a very CPU intensive and time costly validation path.

The NSEC3 vulnerability uses specially crafted responses on a malicious zone with multiple NSEC3 RRSETs to force a DNSSEC validator down a very CPU intensive and time costly NSEC3 hash calculation path.

Both can force Unbound to spend an enormous time (comparative to regular traffic) validating a single specially crafted DNSSEC response while everything else is on hold for that thread. A trivially orchestrated attack could render all threads busy with such responses leading to denial of service.

From version 1.19.1 on, Unbound introduces suspension on DNSSEC response validations that seem to require more attempts than Unbound is willing to make per response validation run. Suspension means that Unbound will continue with other work before resuming a suspended validation offering CPU time between validation resumptions to other tasks. There is a backoff timer when suspending which is further influenced by the number of suspends already used and the amount of work currently in Unbound.

The introduced builtin limits in Unbound are:

• Max 4 DNSSEC key collissions are allowed when building chain of trust. More than that without a secure key treats the delegation as bogus.
• 8 validation attempts per RRSET (combination of keys + signatures). If more are needed and Unbound has yet to find a valid signature the RRSET is treated as bogus.
• More than 8 validation attempts per answer will suspend validation.
• 8 NSEC3 hash calculations are allowed before suspension. More than that will suspend validation.
• The limit of total suspensions is 16 after which the query will error out. Any completed RRSET validations populate the cache for use in future queries.

While under attack Unbound could show higher CPU load because of the needed validations but the suspend strategy would guarantee the CPU is not locked on any particular validation task.

We would like to thank Elias Heftrig, Haya Schulmann, Niklas Vogel, and Michael Waidner from the German National Research Center for Applied Cybersecurity ATHENE for discovering and responsibly disclosing the KeyTrap vulnerability.

We would like to thank Petr Špaček from ISC for discovering and responsibly disclosing the NSEC3 vulnerability.

Bug Fixes

• Fix CVE-2023-50387, DNSSEC verification complexity can be exploited to exhaust CPU resources and stall DNS resolvers.
• Fix CVE-2023-50868, NSEC3 closest encloser proof can exhaust CPU.

Unbound 1.19.0

This release fixes a number of bugs, and adds some smaller features. The redis-logical-db option and cachedb-no-store option can be used for cachedb configuration. The disable-edns-do option can be used for working around broken network parts. For DNS64 there is fallback to plain AAAA when no A record exists.

There is a bug fix that when the UDP interface keeps returning that sending is not possible, unbound does not loop endlessly and waits for the condition to go away.

Resource records of type A and AAAA that are an inappropriate length are removed from responses. This hardens against bad content.

Features

• Fix #850: [FR] Ability to use specific database in Redis, with new redis-logical-db configuration option.
• Merge #944: Disable EDNS DO. Disable the EDNS DO flag in upstream requests. This can be helpful for devices that cannot handle DNSSEC information. But it should not be enabled otherwise, because that would stop DNSSEC validation. The DNSSEC validation would not work for Unbound itself, and also not for downstream users. Default is no. The option is disable-edns-do: no
• Expose the script filename in the Python module environment 'mod_env' instead of the config_file structure which includes the linked list of scripts in a multi Python module setup; fixes #79.
• Expose the configured listening and outgoing interfaces, if any, as a list of strings in the Python 'config_file' class instead of the current Swig object proxy; fixes #79.
• Mailing list patches from Daniel Gröber for DNS64 fallback to plain AAAA when no A record exists for synthesis, and minor DNS64 code refactoring for better readability.
• Merge #951: Cachedb no store. The cachedb-no-store: yes option is used to stop cachedb from writing messages to the backend storage. It reads messages when data is available from the backend. The default is no.

Bug Fixes

• Fix for version generation race condition that ignored changes.
• Fix #942: 1.18.0 libunbound DNS regression when built without OpenSSL.
• Fix for WKS call to getservbyname that creates allocation on exit in unit test by testing numbers first and testing from the services list later.
• Fix autoconf 2.69 warnings in configure.
• Fix #927: unbound 1.18.0 make test error. Fix make test without SHA1.
• Merge #931: Prevent warnings from -Wmissing-prototypes.
• Fix to scrub resource records of type A and AAAA that have an inappropriate size. They are removed from responses.
• Fix to move msgparse_rrset_remove_rr code to util/msgparse.c.
• Fix to add EDE text when RRs have been removed due to length.
• Fix to set ede match in unit test for rr length removal.
• Fix to print EDE text in readable form in output logs.
• Fix send of udp retries when ENOBUFS is returned. It stops looping and also waits for the condition to go away. Reported by Florian Obser.
• Fix authority zone answers for obscured DNAMEs and delegations.
• Merge #936: Check for c99 with autoconf versions prior to 2.70.
• Fix to remove two c99 notations.
• Fix rpz tcp-only action with rpz triggers nsdname and nsip.
• Fix misplaced comment.
• Merge #881: Generalise the proxy protocol code.
• Fix #946: Forwarder returns servfail on upstream response noerror no data.
• Fix edns subnet so that queries with a source prefix of zero cause the recursor send no edns subnet option to the upstream.
• Fix that printout of EDNS options shows the EDNS cookie option by name.
• Fix infinite loop when reading multiple lines of input on a broken remote control socket. Addesses #947 and #948.
• Fix #949: "could not create control compt".
• Fix that cachedb does not warn when serve-expired is disabled about use of serve-expired-reply-ttl and serve-expired-client-timeout.
• Fix for #949: Fix pythonmod/ubmodule-tst.py for Python 3.x.
• Better fix for infinite loop when reading multiple lines of input on a broken remote control socket, by treating a zero byte line the same as transmission end. Addesses #947 and #948.
• For multi Python module setups, clean previously parsed module functions in main's dictionary, if any, so that only current module functions are registered.
• Fix #954: Inconsistent RPZ handling for A record returned along with CNAME.
• Fixes for the DNS64 patches.
• Update the dns64_lookup.rpl test for the DNS64 fallback patch.
• Merge #955 from buevsan: fix ipset wrong behavior.
• Update testdata/ipset.tdir test for ipset fix.
• Fix to print detailed errors when an SSL IO routine fails via SSL_get_error.
• Clearer configure text for missing protobuf-c development libraries.
• autoconf.
• Merge #930 from Stuart Henderson: add void to log_ident_revert_to_default declaration.
• Fix #941: dnscrypt doesn't work after upgrade to 1.18 with suggestion by dukeartem to also fix the udp_ancil with dnscrypt.
• Fix SSL compile failure for definition in log_crypto_err_io_code_arg.
• Fix SSL compile failure for other missing definitions in log_crypto_err_io_code_arg.
• Fix compilation without openssl, remove unused function warning.
• Mention flex and bison in README.md when building from repository source.