Deployment news (comcast.net publishes TLSA RRs)
Today comcast.net published TLSA records for their MX hosts. comcast.net. IN MX 5 mx1.comcast.net. comcast.net. IN MX 5 mx2.comcast.net. _25._tcp.mx1.comcast.net. IN TLSA 3 1 1 90e2f742b459860c0bbf1343b5a36bc5842a3f45056d30bf25dbb475a62eca47 _25._tcp.mx2.comcast.net. IN TLSA 3 1 1 c8cb2faa4c0b92cb3fd37e61eb4671744055f123c14c0dd31e8d92c379f9f8a3 $ posttls-finger -c -Lsummary -o inet_protocols=ipv4 "[mx1.comcast.net]" posttls-finger: Verified TLS connection established to mx1.comcast.net[96.114.157.80]:25: TLSv1.2 with cipher DHE-RSA-AES256-SHA (256/256 bits) $ posttls-finger -c -Lsummary -o inet_protocols=ipv4 "[mx2.comcast.net]" posttls-finger: Verified TLS connection established to mx2.comcast.net[68.87.20.5]:25: TLSv1.2 with cipher DHE-RSA-AES256-SHA (256/256 bits) Congratulations and thanks to Comcast. They are the first major US email provider to do so. Let's hope their lead will be followed by many others. My ongoing survey has now found 9389 working DANE domains. Most of these are served by a few domain hosting providers: 5230 udmedia.de 955 nederhost.net 354 transip.email 47 mediaweb-it.net 45 mailbox.org 36 gr-webdesign.de 32 core-networks.de 32 wk-serv.net 30 set-hosting.de 30 dotplex.de The actual numbers of DANE-enabled hosted domains is much larger, for example udmedia alone reportedly has over 25 thousand. My lists of candidate domains to test are far from complete. Of these 9389, there are now 28 domains (up from 27 yesterday now that comcast.net is live) that are "large enough" to be listed in Google's email transparency report: conjur.com.br jpberlin.de comcast.net freebsd.org mypst.com.br lrz.de rrpproxy.net ietf.org registro.br posteo.de t-2.net isc.org societe.com ruhr-uni-bochum.de aanbodpagina.nl netbsd.org t-2.com tum.de xs4all.nl openssl.org bayern.de unitymedia.de debian.org samba.org bund.de lepartidegauche.fr eu.org torproject.org On the "problem" front. The following DNS hosters still have some issues with correct DNSSEC "denial of existence": #Domains Provider -------- ---------- 33 binero.se (resolution in progress) 28 isphuset.no (issue acknowledged) 15 axc.nl (notified) 11 papaki.gr (notified) 5 forpsi.net (notified) And 10 "small" domains currently publish incorrect TLSA records: bebidaliberada.com.br solucoesglobais.com.br nevodnet.com zx.com 1post.de geekify.de wx0.de tsimnet.eu konundrum.org www.co.tt If anyone reading this happens to know a usable contact for the above, please let them know their TLSA records need updates. Finally, I have a list of ~97000 domains that have DNSSEC and at least one "primary" MX host has DNSSEC, but no TLSA records are published as yet. These domains are good candidates for DANE deployment, it is just a matter of deciding out of whether to use "3 1 1" end-entity records or "2 0 1" trust-anchor records, and documenting a key/cert rotation procedure: https://tools.ietf.org/html/rfc7671#section-5.1 https://tools.ietf.org/html/rfc7671#section-5.2 As always, don't forget: https://dane.sys4.de/common_mistakes#3 https://dane.sys4.de/common_mistakes#6 https://tools.ietf.org/html/rfc7671#section-8.1 https://tools.ietf.org/html/rfc7671#section-8.4 -- Viktor.
On Tue, Nov 03, 2015 at 08:10:19PM +0000, Viktor Dukhovni wrote:
On the "problem" front. The following DNS hosters still have some issues with correct DNSSEC "denial of existence":
#Domains Provider -------- ---------- 33 binero.se (resolution in progress) 28 isphuset.no (issue acknowledged) 15 axc.nl (notified) 11 papaki.gr (notified) 5 forpsi.net (notified)
I'm told isphuset.no are expecting to resolve the issue this month. Also papaki.gr have upgraded their PowerDNS servers, and the issue is resolved for their domains. -- Viktor.
On Tue, Nov 03, 2015 at 08:10:19PM +0000, Viktor Dukhovni wrote:
#Domains Provider -------- ---------- 33 binero.se (resolution in progress) 28 isphuset.no (issue acknowledged) 15 axc.nl (notified) 5 forpsi.net (notified)
DNS at binero.se is now resolved. With ongoing scans in the mean-time, the number of affected domains I managed to find was briefly more than eighty, but now it is zero. The solution was actually a software update at neustar.biz (also known as UltraDNS.net) so this also addresses the same issue for all other ultradns.net customers (only one such domain in my scans, but my surveys are far from comprehensive). Progress continues. -- Viktor.
I have been attempting to push more people to use dane, but it is hard.
More and more server admins keep asking to not send email to their
domains without tls verification or certificate pinning, but none of
them have heard of dane. Most don't even have dnssec even.
Quoting Viktor Dukhovni
On Tue, Nov 03, 2015 at 08:10:19PM +0000, Viktor Dukhovni wrote:
#Domains Provider -------- ---------- 33 binero.se (resolution in progress) 28 isphuset.no (issue acknowledged) 15 axc.nl (notified) 5 forpsi.net (notified)
DNS at binero.se is now resolved. With ongoing scans in the mean-time, the number of affected domains I managed to find was briefly more than eighty, but now it is zero.
The solution was actually a software update at neustar.biz (also known as UltraDNS.net) so this also addresses the same issue for all other ultradns.net customers (only one such domain in my scans, but my surveys are far from comprehensive). Progress continues.
-- Viktor.
On Fri, Nov 20, 2015 at 09:12:49PM -0500, Patrick Domack wrote:
I have been attempting to push more people to use dane, but it is hard.
More and more server admins keep asking to not send email to their domains without tls verification or certificate pinning, but none of them have heard of dane. Most don't even have dnssec even.
Thanks for helping get the message out. Yes, it is difficult to get initial momentum. Still, certificate pinning scales exceedingly poorly, so it is worth trying. This is still fairly early in the adoption cycle. I need to get DANE TLS adopted into OpenSSL. Some initial code is awaiting internal team review... It will be important to see DANE support in more than Postfix and early adopter releases of Exim. The folks publishing TLSA records need only DNSSEC and some operational discipline, no need (at the same time) to deploy an MTA that can verify such records. They may need better DNSSEC tools. IIRC Microsoft significantly enhanced DNSSEC support in recent releases of ActiveDirectory. Adoption has grown from a hundred or so domains last summer to thousands now, but mostly small domains. I hope momentum will pick up once web.de and gmx.de go live. -- Viktor.
Quoting Viktor Dukhovni
On Fri, Nov 20, 2015 at 09:12:49PM -0500, Patrick Domack wrote:
I have been attempting to push more people to use dane, but it is hard.
More and more server admins keep asking to not send email to their domains without tls verification or certificate pinning, but none of them have heard of dane. Most don't even have dnssec even.
Thanks for helping get the message out. Yes, it is difficult to get initial momentum. Still, certificate pinning scales exceedingly poorly, so it is worth trying.
This is still fairly early in the adoption cycle. I need to get DANE TLS adopted into OpenSSL. Some initial code is awaiting internal team review... It will be important to see DANE support in more than Postfix and early adopter releases of Exim.
The folks publishing TLSA records need only DNSSEC and some operational discipline, no need (at the same time) to deploy an MTA that can verify such records. They may need better DNSSEC tools. IIRC Microsoft significantly enhanced DNSSEC support in recent releases of ActiveDirectory.
Adoption has grown from a hundred or so domains last summer to thousands now, but mostly small domains. I hope momentum will pick up once web.de and gmx.de go live.
Yes, I have noticed it is a big movement in germany. Have had a lot of people asking for help on setting up dane the last few months from there. But can't get any movement that is noticable here in the usa.
On Fri, Nov 20, 2015 at 09:48:43PM -0500, Patrick Domack wrote:
Yes, I have noticed it is a big movement in germany. Have had a lot of people asking for help on setting up dane the last few months from there. But can't get any movement that is noticable here in the usa.
I think that what's needed is getting software support for DANE into OpenSSL, mTLS and GnuTLS, plus adoption by the SMTP major appliance vendors, Ironport, Proofpoint, ... and of course Microsoft Exchange. There's still some work to do. Making it easier to update the DNS with the right records would also help, sadly there's no satisfactory and standard management interface with a decent access control model. So automating publication of TLSA records is difficult. Perhaps we need a new protocol by which a TLS server can securely pre-publish the next certificate without activating it (say include it in a new TLS extension), thus allowing the DNS server operator to automate TLSA record updates by querying the SMTP server (authenticated via the current records). If anyone has better ideas to automate coordination of DNS updates and key rotation, I'm all ears... -- Viktor.
Quoting Viktor Dukhovni
On Fri, Nov 20, 2015 at 09:48:43PM -0500, Patrick Domack wrote:
Yes, I have noticed it is a big movement in germany. Have had a lot of people asking for help on setting up dane the last few months from there. But can't get any movement that is noticable here in the usa.
Perhaps we need a new protocol by which a TLS server can securely pre-publish the next certificate without activating it (say include it in a new TLS extension), thus allowing the DNS server operator to automate TLSA record updates by querying the SMTP server (authenticated via the current records).
That sounds pretty difficult to adjust for, and would need a lot of changes. I like the current dnssec method, where we can publish multiple keys. I will generally publish a new key a month ahead of time for my ksk rollover, then rotate it, and then a month later remove the old key. The same method could be done for tlsa, by publishing multiple records. I have not tested if any software accepts this or not, but just publishing the new one a week ahead of time, rotating it, and removing the old one at the same or later time (in case of failback), to me sounds like the perferred method.
On Fri, Nov 20, 2015 at 10:38:14PM -0500, Patrick Domack wrote:
Perhaps we need a new protocol by which a TLS server can securely pre-publish the next certificate without activating it (say include it in a new TLS extension), thus allowing the DNS server operator to automate TLSA record updates by querying the SMTP server (authenticated via the current records).
That sounds pretty difficult to adjust for, and would need a lot of changes.
Well, it requires IETF action and software support on the server side, yes.
I like the current dnssec method, where we can publish multiple keys. I will generally publish a new key a month ahead of time for my ksk rollover, then rotate it, and then a month later remove the old key.
This works today, but automating the publication of the "future" TLSA record is the part that some will struggle with.
The same method could be done for tlsa, by publishing multiple records.
Not could, is. See: https://tools.ietf.org/html/rfc7671#section-8.1 ...
I have not tested if any software accepts this or not, but just publishing the new one a week ahead of time, rotating it, and removing the old one at the same or later time (in case of failback), to me sounds like the perferred method.
Yes, that's what section 8 of RFC7671 describes. And of course this is supported by Postfix and Exim, and will soon(ish) be supported by OpenSSL. The problem is that if certificate deployment is fully automated (see today's Let's Encrypt thread on this list), then prepublishing the next TLSA record becomes difficult. The work-arounds, are: * Keep the key the same while getting new certificates for it, publish "DANE-EE(3) SPKI(1) SHA2-256(1)" records, change keys manually, and go through the usual prepublication process for the key digest. * Switch to using "DANE-TA(2) SPKI(1) SHA2-256(1)" records, with a selector of SPKI rather that Cert, because with a third-party issuing CA, you have less control over when the CA cert might get re-issued to extend its life, or cross-sign it, ... Then you're good while the same CA (private key) continues to issue your certificates. The CA cert needs to appear in your chain even if it is a root CA. https://tools.ietf.org/html/rfc7671#section-5.2 -- Viktor.
participants (2)
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Patrick Domack -
Viktor Dukhovni