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A comment on Let's Encrypt Has Issued a Billion Certificates. Parent comment

Re:Let's Encrypt Has Issued a Billion Certificates by tptacek on Friday February 28, 2020 @11:00AM (#22443643)
No it can't, because no mainstream browser supports or ever will support DANE.
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Re:Let's Encrypt Has Issued a Billion Certificates by alwillis on Friday February 28, 2020 @02:27PM (#22445550)
Notice I never mentioned browsers.

Breaking news: there are other applications on the internet other than browsers.

And some of them use TLSA records. It’s the de facto standard for for secure email, especially if you want guaranteed protection from downgrade attacks.

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Re:Let's Encrypt Has Issued a Billion Certificates by tptacek on Friday February 28, 2020 @02:32PM (#22445594)
Virtually no email sent on the Internet is protected by DANE, DNSSEC, or TLSA. Nor is it likely ever to be, since the major email providers standardized MTA-STS specifically to avoid DNSSEC, as you can see from the opening paragraphs of the standard.
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Re:Let's Encrypt Has Issued a Billion Certificates by alwillis on Friday February 28, 2020 @10:13PM (#22448504)
This is provably false.

DNSSEC, DANE and TLSA are widely used to secure SMTP servers. From the web page showing the nearly 2 million domains with signed MX and DANE records [1]:

The following graph depicts the number of domains that have deployed DANE/SMTP. Specifically, their zone is signed, their MX records all point to hosts that have DANE TLSA records.

Regarding MTA-STS, it's a work-around for the large global email providers that can’t implement DNSSEC for a variety of reasons.

Again, MTA-STS has problems, the main one is being susceptible to downgrade attacks because MTA-STS doesn’t use DNSSEC. An attacker can MiTM a connection preventing a TLS connection.

The MTA-STS RFC [2] confirms this:

    The DNS-Based Authentication of a Named Entities (DANE)TLSA
    record [RFC7672] is similar, in that DANE is also designed
    to upgrade unauthenticated encryption or plaintext
    transmission into authenticated, downgrade-resistant
    encrypted transmission.  DANE requires DNSSEC [RFC4033] for
    authentication; the mechanism described here instead relies
    on certification authorities (CAs) and does not require
    DNSSEC, at a cost of risking malicious downgrades.
There’s no dispute about any of this, so it’s not clear why you continue to make false and misleading statements about these technologies, regardless of your opinions about them.

You know the old saying: you’re entitled to your own opinion but not your own facts.

[1]: https://stats.dnssec-tools.org/#dnssec

[2]: https://tools.ietf.org/html/rfc8461#section-2

A more complete description I posted previously: https://news.ycombinator.com/item?id=22338742

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Re:Let's Encrypt Has Issued a Billion Certificates by tptacek on Friday February 28, 2020 @10:17PM (#22448520)
As you well know, since this is the third time you've tried to make this point, the overwhelming majority of those zones were signed automatically by their European registrars; these counts have no relationship to actual emails sent.

The entire idea behind STS protocols is to use continuity schemes to defeat downgrades. It's literally the only threat model.

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Re:Let's Encrypt Has Issued a Billion Certificates by alwillis on Friday February 28, 2020 @10:49PM (#22448669)
these counts have no relationship to actual emails sent

These domains wouldn’t have MX or TLSA records unless they were doing email.

Even if a zone is pre-signed, an admin has to intentionally create DANE records, which they wouldn’t do unless they were hosting SMTP servers.

But it does show the statement that DNSSEC, DANE and TLSA aren’t used for secure email to be utterly untrue.

MTA-STS has other issues:

    * Authenticates domain control via CA leap of faith

    * Vulnerable to MiTM at cert bootstrap

    * Vulnerable to weakest root CA, and unauthorized certs

    * Open to downgrade on first (or irregular) contact

    * Complex mix of HTTPS, unsigned DNS and SMTP
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Re:Let's Encrypt Has Issued a Billion Certificates by tptacek on Saturday February 29, 2020 @12:19AM (#22449031)
Horseshit. I have something like 50 domains on a popular retail registrar and every single one of them has an MX record, despite me never doing a single thing other than claiming the name; they come by default with new domains. If I was in the Netherlands, every one of them would have DNSSEC signatures too, because European registrars opt domains into DNSSEC by default.

I'm having a hard time articulating how silly it is to try to dunk on MTA-STS for being "vulnerable" to downgrade attacks; it's like trying to say that HSTS is vulnerable to SSL-stripping attacks. You have to not understand the idea behind the attack or the countermeasure to lead with that argument.

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Re:Let's Encrypt Has Issued a Billion Certificates by alwillis on Friday February 28, 2020 @11:48PM (#22448906)
Virtually no email sent on the Internet is protected by DANE, DNSSEC, or TLSA.

Here's a short list of domains that are using DNSSEC, DANE and TLSA to protect their email. I also provide a transcript of a utility that connects to and verifies the SMTP server and the DANE/TLSA records for openssl.org and could have done so for every domain on this list but there's no reason to get carried away.

* geektimes.com

* gmx.com

* mail.com

* comcast.net

* dd24.net

* debian.org

* freebsd.org

* gentoo.org

* ietf.org

* isc.org

* netbsd.org

* openssl.org

* samba.org

* torproject.org

There's a DANE TLS SMTP server checking tool: https://www.huque.com/bin/danecheck-smtp

Here's what it does: This application checks a DANE SMTP Service. It queries the MX record set for the given domain, looks up DANE TLSA records at the MX targets, connects to the target servers, negotiates STARTTLS, and then attempts to verify the TLS server certificate against the TLSA records.

Lets test openssl.org:

    Domain Name: openssl.org

    MX host: 50 mta.openssl.org

    #################################################################
    ### CHECKING MX HOST: mta.openssl.org
    #################################################################

    TLSA records found: 1
    TLSA: 3 1 1 6cf12d78fbf242909d01b96ab5590812954058dc32f8415f048fff064291921e

    Connecting to IPv6 address: 2001:608:c00:180::1:e6 port 25
    recv: 220-mta.openssl.org ESMTP Postfix
    recv: 220 mta.openssl.org ESMTP Postfix
    send: EHLO cheetara.huque.com
    recv: 250-mta.openssl.org
    recv: 250-PIPELINING
    recv: 250-SIZE 36700160
    recv: 250-VRFY
    recv: 250-ETRN
    recv: 250-STARTTLS
    recv: 250-ENHANCEDSTATUSCODES
    recv: 250-8BITMIME
    recv: 250 DSN
    send: STARTTLS
    recv: 220 2.0.0 Ready to start TLS
    TLSv1.2 handshake succeeded.
    Cipher: TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384
    Peer Certificate chain:
     0 Subject CN: mta.openssl.org
     Issuer  CN: Let's Encrypt Authority X3
      1 Subject CN: Let's Encrypt Authority X3
     Issuer  CN: DST Root CA X3
      SAN dNSName: mta.openssl.org
    DANE TLSA 3 1 1 [6cf12d78fbf2...] matched EE certificate at depth 0
    Validated Certificate chain:
     0 Subject CN: mta.openssl.org
       Issuer  CN: Let's Encrypt Authority X3
     SAN dNSName: mta.openssl.org

    Connecting to IPv4 address: 194.97.150.230 port 25
    recv: 220-mta.openssl.org ESMTP Postfix
    recv: 220 mta.openssl.org ESMTP Postfix
    send: EHLO cheetara.huque.com
    recv: 250-mta.openssl.org
    recv: 250-PIPELINING
    recv: 250-SIZE 36700160
    recv: 250-VRFY
    recv: 250-ETRN
    recv: 250-STARTTLS
    recv: 250-ENHANCEDSTATUSCODES
    recv: 250-8BITMIME
    recv: 250 DSN
    send: STARTTLS
    recv: 220 2.0.0 Ready to start TLS
    TLSv1.2 handshake succeeded.
    Cipher: TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384
    Peer Certificate chain:
     0 Subject CN: mta.openssl.org
       Issuer  CN: Let's Encrypt Authority X3
     1 Subject CN: Let's Encrypt Authority X3
       Issuer  CN: DST Root CA X3
     SAN dNSName: mta.openssl.org
    DANE TLSA 3 1 1 [6cf12d78fbf2...] matched EE certificate at depth 0
    Validated Certificate chain:
     0 Subject CN: mta.openssl.org
       Issuer  CN: Let's Encrypt Authority X3
     SAN dNSName: mta.openssl.org

    [0] Authentication succeeded for all (2) peers.
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Re:Let's Encrypt Has Issued a Billion Certificates by tptacek on Saturday February 29, 2020 @12:20AM (#22449036)
With the note that those are literally the best domain names you can come up with, and that you can go to the search bar below and look at my comments to see me running the Moz 500 through the same analysis, I feel like your list makes my point for me. Thanks.

DNSSEC standardization began in NINETEEN NINETY FIVE. That's twenty five years ago. They got GENTOO.ORG. That's the win you're crowing over. Congratulations! As goes GENTOO.ORG, so too goes the Internet.

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Re:Let's Encrypt Has Issued a Billion Certificates by fulafel on Monday March 02, 2020 @01:32AM (#22462166)
Internet protocol evolution is in a funny place currently. IPv6 is just as old and it's only recently been widely deployed. There's just so much inertia.
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