April 2020 - dane-users

Overview of outbound DANE for SMTP support
by Knubben, B.S.J. (Bart) - Forum Standaardisatie 26 May '21

26 May '21

Hi, We made the following overview of products/services with outbound DANE support (i.e. DANE verification). Any remarks/additions are welcome. I. Supported: - Postfix (since version 2.11.0, January 2014): http://www.postfix.org/TLS_README.html#client_tls_dane - Halon (since version 3.4-r2, November 2015): https://halon.io/dane and https://wiki.halon.io/DANE - OpenSSL (since version 1.1.0, August 2016): https://www.openssl.org/docs/manmaster/man3/SSL_CTX_dane_enable.html and https://www.openssl.org/docs/manmaster/man1/openssl-s_client.html - Cloudmark (since version 5.2, March 2017): https://blog.cloudmark.com/2017/03/27/dane-and-email-security/ - Exim (since version 4.91, April 2018): https://www.exim.org/exim-html-current/doc/html/spec_html/ch-encrypted_smtp… - Mail-in-a-Box (uses Postfix): https://github.com/mail-in-a-box/mailinabox/blob/master/security.md - ldns (uses OpenSSL): https://www.nlnetlabs.nl/documentation/ldns/dane_8h.html II. Requested: - Cisco: Bug ID: CSCuo87918 - [ Feature Request] TLS DANE Support for Email Security Appliance, https://bst.cloudapps.cisco.com/bugsearch/bug/CSCuo87918/ - MS O365: https://office365.uservoice.com/forums/273493-office-365-admin/suggestions/… and https://office365.uservoice.com/forums/289138-office-365-security-complianc… - Fortinet: https://fortinet.uservoice.com/forums/23797-fortipartner-feature-requests/s… - Protonmail: https://protonmail.uservoice.com/forums/284483-feedback/suggestions/3433882… and https://protonmail.uservoice.com/forums/284483-feedback/suggestions/1659360… BTW a simple outbound DANE test can be found on https://havedane.net. -- Best regards, Bart Knubben Dutch Standardisation Forum https://www.forumstandaardisatie.nl/content/english Dit bericht kan informatie bevatten die niet voor u is bestemd. Indien u niet de geadresseerde bent of dit bericht abusievelijk aan u is toegezonden, wordt u verzocht dat aan de afzender te melden en het bericht te verwijderen. De Staat aanvaardt geen aansprakelijkheid voor schade, van welke aard ook, die verband houdt met risico's verbonden aan het elektronisch verzenden van berichten. This message may contain information that is not intended for you. If you are not the addressee or if this message was sent to you by mistake, you are requested to inform the sender and delete the message. The State accepts no liability for damage of any kind resulting from the risks inherent in the electronic transmission of messages.

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Upcoming Glibc changes and DANE support in Postfix, Exim, and perhaps other MTAs
by Viktor Dukhovni 15 Apr '20

15 Apr '20

On Tue, Apr 14, 2020 at 05:59:51PM -0400, Viktor Dukhovni wrote: > but if that is incompatible with other stub resolver libraries on the > same machine, you may need a private musl-specific configuration file. > > My money is on this being unnecessary. I'll let [you] know what I find > from dns-operations, and if possible perhaps a RIPE ATLAS probe, > assuming they support enabling AD=1. Apparently sufficiently recent glibc supports soliciting and censoring the AD-bit. https://gnutoolchain-gerrit.osci.io/r/c/glibc/+/461/3/NEWS * The DNS stub resolver will optionally send the AD (authenticated data) bit in queries if the trust-ad option is set via the options directive in /etc/resolv.conf (or if RES_TRUSTAD is set in _res.options). In this mode, the AD bit, as provided by the name server, is available to applications which call res_search and related functions. In the default mode, the AD bit is not set in queries, and it is automatically cleared in responses, indicating a lack of DNSSEC validation. (Therefore, the name servers and the network path to them are treated as untrusted.) I read this to mean that the new "trust-ad" option, if set, causes the glibc stub resolver to set AD=1 in queries, but otherwise, causes it to strip the AD bit from replies. I don't yet have access to systems with this recent a glibc to confirm the above, but this is likely relevant to Postfix and Exim administrators who enable DANE. You may need to explicitly add the "trust-ad" option to your /etc/resolv.conf, while of course also making sure that all the listed nameservers are local (loopback interface). -- Viktor.

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ANN: Support of DANE and DNSSEC in Office 365 Exchange Online
by Patrick Ben Koetter 07 Apr '20

07 Apr '20

All, I'm extremely pleased to post that Microsoft has announced today they will support DANE <https://techcommunity.microsoft.com/t5/exchange-team-blog/support-of-dane-a…> and DNSSEC in Office 365 Exchange Online. Their first step will be to support outbound DANE by end of 2020 and they plan to add inbound support for DANE by end of 2021. Please note that they will also implement support for TLSRPT <https://tools.ietf.org/html/rfc8460>, which is a good thing[tm] if you run strict TLS policies for your email platform. Well done, Microsoft! It's great to see a big player step forward, adopt DANE and make email more secure. p@rick -- [*] sys4 AG https://sys4.de, +49 (89) 30 90 46 64 Schleißheimer Straße 26/MG,80333 München Sitz der Gesellschaft: München, Amtsgericht München: HRB 199263 Vorstand: Patrick Ben Koetter, Marc Schiffbauer, Wolfgang Stief Aufsichtsratsvorsitzender: Florian Kirstein

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Deprecating DNSSEC algorithms 5 (RSASHA1) and 7 (RSASHA1-NSEC3-SHA1)
by Viktor Dukhovni 06 Apr '20

06 Apr '20

Given the recent advances in SHA-1 collision attacks, https://www.dns.cam.ac.uk/news/2020-01-09-sha-mbles.html https://sha-mbles.github.io/ it is time to deprecate the remaining DNSSEC SHA-1 based DNSKEY algorithms. If you've deployed inbound DANE by publishing signed TLSA records for your MX hosts, but your underlying DNSSEC deployment uses DNSKEY algorithms other than 13 (recommended), 8 (popular) or 10 (fine, though not widely used), then you should migrate your domains to algorithm 13 (preferred) or 8. This should be done while the attacks are still costly, and have somewhat limited applicability. Algorithms 5 (RSASHA1) and 7 (RSASHA1-NSEC3-SHA1) may not be quite dead, but they are significantly wounded. If/when you do decide to switch algorithms, please perform the migration with care. Algorithm rollovers can be tricky. The basic process is: 1. Publish and activate a ZSK for the new algorithm. Your zone should now be double-signed, which each record having two RRSIGs. Don't forget to bump the SOA. 2. Wait for at least 2 maximum TTLs after the primary and all secondary nameservers have started serving the updated zone. 3. Publish and activate a KSK for the new algorithm. This KSK adds a second signature to your zone apex DNSKEY RRset. Don't forget to bump the SOA. 4. Wait for at least 2 maximum TTLs after the primary and all secondary nameservers have started serving the updated zone. 5. Arrange for the parent zone to publish DS records matching the new KSK in addition to DS RRs matching the KSKs for the previous algorithm. 6. Wait for at least 2 parent zone TTLs after all nameservers for the parent zone have started serving the new DS RRset. 7. Request deletion of the DS RRs for the old algorithm. 8. Wait for at least 2 parent zone TTLs after all nameservers for the parent zone have starting serving the new DS RRset. 9. Remove the old KSKs from your DNSKEY RRset after checking that the DS RRset with just the new algorithm matches your new KSK. 10. Wait for at least 2 maximum TTLs after the primary and all secondary nameservers have started serving the updated zone. 11. Deactivate the old ZSKs leaving the zone signed only under the new ZSKs. 12. Wait for at least 2 maximum TTLs after the primary and all secondary nameservers have started serving the updated zone. 13. Remove the old ZSKs from your DNSKEY RRset. The reason for all this is to maintain the followin invariants: A. Each algorithm mentioned in the parent zone DS RRset must have a matching KSK in the zone's DNSKEY RRset. B. Each KSK algorithm appearing in the zone's DNSKEY RRset must have a corresponding ZSK signature for each record in the zone. Therefore, new algorithms are introduced from the ZSK up, while old algorithms are removed from the DS RRset down. The various "wait" steps are needed to ensure that resolvers using cached data are able to validate your changing zone at all times. Presently, the DANE survey database shows ~230 thousand domains using algorithms 5 and 7. It would be great to see this number substantially reduced over the coming months. -- Viktor.

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Update on stats 2020-03
by Viktor Dukhovni 01 Apr '20

01 Apr '20

Summary: The DANE domain count is now 1,877,704. The number of domains that return DNSSEC-validated replies in response to MX queries is 10,922,412. Thus DANE TLSA is deployed on ~17.19% of domains with DNSSEC. Credits: The coverage of DNSSEC domains continues to improve with ongoing data support from Paul Vixie of Farsight Security. Credits also due to ICANN for gTLD data via CZDS, and to the TLD registries for .CH, .COM, .DK, .FR, .INFO, .IS, .LI, .NL, .NU, .ORG and .SE. More data sources of ccTLD signed delegations welcome. As of today I count 1,877,704 domains with correct SMTP DANE TLSA records at every primary MX host that accepts connections[1]. As expected, the bulk of the DANE domains are hosted by the DNS/email hosting providers who've enabled DANE support for the customer domains they host. The top 20 MX host providers by domain count are below. 1035802 one.com 136509 transip.nl 100753 domeneshop.no 88719 loopia.se 71404 infomaniak.ch 38325 active24.com 31059 vevida.com 30605 antagonist.nl 27536 webreus.nl 26933 web4u.cz 26278 zxcs.nl 24969 udmedia.de 17444 bhosted.nl 15192 flexfilter.nl 13854 onebit.cz 9816 protonmail.ch 5810 netzone.ch 5631 previder.nl 5477 soverin.net 4872 zonemx.eu The real numbers are surely larger, because I don't have access to the full zone data for most ccTLDs, especially .no/.cz/.de/.eu/.be. Speaking of countries, the IPv4 GeoIP distribution of DANE-enabled MX hosts shows the below top 20 countries (each unique IP address is counted, so multi-homed MX hosts are perhaps somewhat over-represented). 6347 TOTAL 2111 DE, Germany 1273 US, United States 919 NL, Netherlands 540 FR, France 261 GB, United Kingdom 215 CZ, Czechia 154 CA, Canada 87 CH, Switzerland 82 SG, Singapore 79 SE, Sweden 71 DK, Denmark 47 IE, Ireland 45 AU, Australia 41 AT, Austria 32 JP, Japan 28 IN, India 28 BR, Brazil 27 PL, Poland 25 RU, Russia 24 FI, Finland IPv6 is less common than IPv4 for MX hosts, and the top 20 countries by DANE MX host IPv6 GeoIP are: 3247 TOTAL 1324 DE, Germany 559 US, United States 467 NL, Netherlands 270 FR, France 124 CZ, Czechia 99 GB, United Kingdom 39 SE, Sweden 39 CH, Switzerland 39 CA, Canada 35 SG, Singapore 25 RU, Russia 24 AT, Austria 20 IE, Ireland 16 ID, Indonesia 16 DK, Denmark 15 AU, Australia 14 NO, Norway 14 JP, Japan 11 FI, Finland 11 BR, Brazil There are 5361 unique zones in which the underlying MX hosts are found, this counts each of the above providers as just one zone, so is a measure of the breadth of adoption in terms of organizations deploying DANE SMTP. The number of published MX host TLSA RRsets found is 8115. These cover 9040 distinct MX hosts (some MX hosts share the same TLSA records through CNAMEs). The number of domains that at some point were listed in Gmail's email transparency report is 334 (this is my ad-hoc criterion for a domain being a large-enough actively used email domain). Of these, 160 are in recent (last 90 days of) reports: univie.ac.at lrz.de hierinloggen.nl gmx.at mail.de intermax.nl nic.br mailserver4.de kingsquare.nl registro.br mensa.de mailplus.nl gmx.ch posteo.de minbzk.nl hostpoint.ch ruhr-uni-bochum.de mindef.nl infomaniak.ch tum.de mm1.nl open.ch uni-erlangen.de ouderportaal.nl protonmail.ch unitybox.de overheid.nl anubisnetworks.com unitymedia.de pathe.nl clubedominante.com web.de politie.nl comeseetv.com westlotto.de previder.nl fmc-na.com dk-hostmaster.dk rijksoverheid.nl frenchtogether.com egmontpublishing.dk rotterdam.nl gmx.com netic.dk ru.nl habr.com star.dk rvo.nl hotelsinduitsland.com stil.dk schoudercom.nl infomaniak.com uni-c.dk schuurman-schoenen.nl ingthink.com tilburguniversity.edu ssonet.nl kpn.com emta.ee truetickets.nl leszexpertsfle.com lugeja.ee uvt.nl mail.com rmit.ee xs4all.nl mammoetmail.com rediris.es zorgmail.nl one.com uv.es domeneshop.no primexbt.com litebit.eu handelsbanken.no protonmail.com web200.eu uib.no solvinity.com zone.eu webcruitermail.no t-2.com ac-strasbourg.fr atelkamera.nu telfort.com compagnie-des-sens.fr goget.nu thalesgroup.com octopuce.fr aegee.org trashmail.com web200.hu debian.org xfinity.com comcast.net freebsd.org xfinityhomesecurity.com dns-oarc.net gentoo.org xfinitymobile.com gmx.net ietf.org active24.cz habramail.net isc.org atlas.cz hr-manager.net mailbox.org centrum.cz inexio.net netbsd.org cuni.cz mpssec.net openssl.org itesco.cz procurios.net ozlabs.org klubpevnehozdravi.cz riseup.net samba.org krypton.cz t-2.net slackbuilds.org onebit.cz transip.net torproject.org optimail.cz xs4all.net whatpulse.org smtp.cz xworks.net asf.com.pt virusfree.cz belastingdienst.nl boplatssyd-automail.se volny.cz bhosted.nl handelsbanken.se bayern.de bluerail.nl loopia.se bund.de boozyshop.nl minmyndighetspost.se elster.de corpoflow.nl personligalmanacka.se fau.de dictu.nl skatteverket.se freenet.de digid.nl theletter.se gmx.de ezorg.nl govtrack.us jpberlin.de gerryweber.nl ru.ac.za kabelmail.de Of the ~1.88 million domains, 4504 have "partial" TLSA records, that cover only a subset of the (secondary) MX hosts. While this protects traffic to some of the MX hosts, such domains are still vulnerable to the usual active attacks via the remaining MX hosts. The number of domains with incorrect TLSA records or failure to advertise STARTTLS (even though TLSA records are published) stands today at 465. Some of these have additional MX hosts that don't have broken TLSA records, so mail can still arrive via the remaining MX hosts. To avoid email outages, please make sure to monitor the validity of your own TLSA records, and implement a reliable key rotation procedure. See: https://dane.sys4.de/common_mistakes https://github.com/internetstandards/toolbox-wiki/blob/master/DANE-for-SMTP… https://mail.sys4.de/pipermail/dane-users/2018-February/000440.html https://community.letsencrypt.org/t/please-avoid-3-0-1-and-3-0-2-dane-tlsa-… https://mail.sys4.de/pipermail/dane-users/2017-August/000417.html https://github.com/baknu/DANE-for-SMTP/wiki/2.-Implementation-resources http://tools.ietf.org/html/rfc7671#section-8.1 http://tools.ietf.org/html/rfc7671#section-8.4 After eliminating parked domains that do not accept email, the number of "real" email domains with bad DNSSEC support stands at 2050. The top 13 name server operators with problem domains are: 616 mijnhostingpartner.nl (fix expected any day now, but may be delayed) 559 registrar-servers.com (a.k.a. Neustar, continuing to grow slowly) 71 ebola.cz 70 movenext.nl 47 metaregistrar.nl 44 axc.nl 43 cdmon.net 37 hyp.net 34 flevohost.nl 30 tiscomhosting.nl 28 hostnet.nl 22 infracom.nl 18 is.nl If anyone has good contacts at some of these providers, please encourage them to remediate not only the broken domains (I can send them a list), but also the root cause that makes the breakage possible. Eleven of the domains all whose nameservers have broken denial of existence appear in the last 120 days of Google transparency reports: coren-sp.gov.br trt01.gov.br trtrio.gov.br trt1.jus.br trtrj.jus.br flytoyourheart.com topdecorationworld.com bncr.fi.cr mobily.com.sa sauditelecom.com.sa threadteaching.co.uk -- Viktor. [1] Some domains deliberately include MX hosts that are always down, presumably as a hurdle to botnet SMTP code that gives up where real MTAs might persist. I am not a fan of this type of defence (it can also impose undue latency on legitimate email). However, provided the dead hosts still have TLSA records, (which don't need to match anything, just need to exist and be well-formed) there's no loss of security.

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