On 9 Jan 2019, at 1:34 pm, Viruthagiri Thirumavalavan
<giri(_at_)dombox(_dot_)org>
wrote:
Why do you think all MiTM attacker will have control over DNS?
Because they ARE IN THE MIDDLE. You can modify DNS responses as easily as
SMTP streams. Firewall vendors that strip STARTTLS will just modify the
DNS responses if this draft gets published.
If that's the case, then we have been fooled by STARTTLS saying it's
secure for the past 20 years.
Why do you think DANE requires signed and validated as secure DNSSEC
responses to the MX/SRV/AAAA/A lookups before it even attempts
a TLSA lookup? You need to know that the inputs have not been spoofed
before deciding if you can trust a CERT being presented.
If your SMTP service provider does not support DANE they DO NOT REALLY
CARE ABOUT SECURITY.
Mark
On Wed, Jan 9, 2019, 7:56 AM Mark Andrews <marka(_at_)isc(_dot_)org wrote:
On 9 Jan 2019, at 1:19 pm, Viruthagiri Thirumavalavan
<giri(_at_)dombox(_dot_)org>
wrote:
The simple answer is WE DO NOT *NEED* MTA-STS. Additionally it can be
spoofed
without DNSSEC. The only thing it does is reduce the number of
players involved
if you are not self hosting.
I get it. You are a fan of DNSSEC. But you should know that I'm not
against DNSSEC (or even STS for that matter). If you think like that, then
you have not read my proposal.
My proposal introduces SMTPS for better security and signal the port
via a prefix. But authentication steps should be given to either DNSSEC or
STS.
Also note, my proposal only trying to INTRODUCE the SMTPS via port 26..
It doesn't force anyone to use SMTPS.
If you use the prefix in your mx host like smtps-mx1.example.com, you
are saying that your server supports both port 26 and 25. Clients should
drop the connection if the certificate is invalid in either port.
Which will be defeated by a MiTM attack unless DNSSEC is used. Strip
the “smtps-“ prefixes from the responses and dummy up non “smtps-" records.
If you use the prefix in your mx host like starttls-mx1.example.com,
you are saying that your server supports only port 25. Clients should drop
the connection if the STARTTLS command not found in the EHLO response or
valid certificate not found.
Again it can be defeated by a MiTM attack. Same method.
On Wed, Jan 9, 2019 at 7:38 AM Viruthagiri Thirumavalavan
<giri(_at_)dombox(_dot_)(_dot_)org>
wrote:
Oh? In what way is it "pretty good"? Yes, SMTPS would hide the
initial 220
message, the EHLO and the response - but there's no info in those two
that
aren't already known after the 3-packet handshake and a few DNS PTR
queries
or obtained by other means - you're going to have a really hard time
claiming
that things like 8bitmime being advertised in the EHLO reply constitute
sensitive info.
Not every PTR queries resolves to the correct domain.
74.125.129.26 => jm-in-f26.1e100.net (A google IP address, but point
to a different domain owned by google)
I would be ok with indirectly someone getting the info rather than
directly providing it.
On Wed, Jan 9, 2019 at 7:27 AM Mark Andrews <marka(_at_)isc(_dot_)org>
wrote:
On 9 Jan 2019, at 12:42 pm, Viruthagiri Thirumavalavan <
giri(_at_)dombox(_dot_)org> wrote:
You just invalidated all my arguments even though I provided
sources.
So let me try in a different way.
If you think DNSSEC is so simple and not controversial, why do we
need MTA-STS?
The simple answer is WE DO NOT *NEED* MTA-STS. Additionally it can be
spoofed
without DNSSEC. The only thing it does is reduce the number of
players involved
if you are not self hosting.
On Wed, Jan 9, 2019, 7:02 AM Mark Andrews <marka(_at_)isc(_dot_)org
wrote:
On 9 Jan 2019, at 11:30 am, Viruthagiri Thirumavalavan <
giri(_at_)dombox(_dot_)org> wrote:
@Mark Andrews
First, When I mentioned "The former requires a HTTPS server and
the latter requires DNSSEC.", I didn't mean DNSSEC is HARD to implement. I
meant DNSSEC is CONTROVERSIAL
Read some of these articles.
https://sockpuppet.org/blog/2015/01/15/against-dnssec/
A whole heap of half truths and poor analysis. If that was
presented as a peer reviewed article it would not be published. You have
been had if you believe that blog post.
https://www.theregister.co.uk/2016/02/23/dnssec_more_problem_than_solution/
“Oh Dear, Big Responses, The World is Going To End!!!!!”. This is
click bait journalism. We have standard track RFCs which provide the
equivalent of TCP’s three way handshake for DNS/UDP. This has been
deployed for 4+ years now along with other measures for clients that don’t
implement the RFC. 8% of the TLD servers currently implement that RFC. It
is on by default in all current implementations of BIND (both client and
server side) and with the exception of a handful of (non RFC compliant)
servers it causes no issues.
Second, unless top domains like Google, Facebook etc. start to use
DNSSEC, you are gonna see questions like this.
https://security.stackexchange.com/questions/21121/if-dnssec-is-so-useful-why-is-its-deployment-non-existent-for-top-domains
28171 of 895949 zones which gave good answers from the alexa to 1M
are signed based on the run I started 2018-12-23T00:00:05Z. The EDNS
compliance testing I do also reports whether the returned result is signed
(ok,yes) or not (ok).
% awk '$13 ~ /signed=ok,yes/ {yes[$1] = 1} $13 ~ /signed=ok/ {
ok[$1] = 1} END { print length ( yes ) , length ( ok ) } '
reports/alexa1m.2018-12-23T00:00:05Z
28171 895949
%
So if you wanna convince others to use DNSSEC, you should start
with big brothers like Google.
Third, Yes DNSSEC is HARD. Maybe not for you. [You seem like a
person who knows your stuff]
No it isn’t. In Unbound it is a checkbox where the server generates
the DNSKEYs and choosing the algorithm. Are you saying ticking a checkbox
is HARD? There TLD’s with +70% of the delegated zones signed. You don’t
get to that level with “DNSSEC is HARD”. The only reason DNSSEC is not
deployed more is COMPLACENCY and FEAR OF SOMETHING NEW.
Neither if these reasons == HARD.
We are talking about mail servers here. Many of these users are
non-tech savvy users who depends on third-party mail hosting services like
G-Suite.
Which almost certainly are using STARTTLS today and maybe using DANE
today as well on the outbound side.
As an engineer you can do those stuffs easily. But a doctor can't
do that. Just because he can't configure DNSSEC doesn't mean he don't
deserve security
And he can get DNSSEC today. There are DNS hosting providers that
will do DNSSEC. Almost all the
TLDs support DNSSEC. There are DNS hosting providers that turn
DNSSEC ON BY DEFAULT. Arguing that you can’t deploy a DNSSEC signed zone
today even as a lay person doesn’t bear up to scrutiny.
Mark
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka(_at_)isc(_dot_)org
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka(_at_)isc(_dot_)org
--
Best Regards,
Viruthagiri Thirumavalavan
Dombox, Inc.
--
Best Regards,
Viruthagiri Thirumavalavan
Dombox, Inc.
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Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka(_at_)isc(_dot_)org
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742 INTERNET: marka(_at_)isc(_dot_)org