[dmarc-discuss] Is DMARC the right place for SMTP-TLS policy and reporting?
Chris Lamont Mankowski
makerofthings77 at gmail.com
Tue Jun 19 22:11:12 PDT 2012
I don't think it's accurate to say this is about compliance verses S/MIME
because that conversation is tangential to why I started this thread;
I want to refocus on the part where SPF authenticates the sender, and DKIM
reports the outcome.
Considering that TLS occurs at approximately the same hop when a SPF record
is validated, and if SPF will be reported on via DKIM why shouldn't TLS be
evaluated similarly? TLS provides an alternative method of validation to
SPF that may be complimentary in some situations. In situations such as
legal or financial documents it could enhance overall security and trust in
John quoted my comment on how Google's planned MUA will show a special icon
for validated messages. Continuing on that train of thought: If TLS
policy is excluded from the DMARC spec, and MUAs end up showing a
validation icon, does that imply that when a message is sent TLS Secured
users will have yet another icon?
I'm envisioning a situation where a single email has so many validation
icons it looks like the message was sponsored by Nascar. Users will be
overwhelmed and won't be able to tell the difference.
The last time a significant user change was implemented someone invented
the EV HTTPS certificate (the green bar in the URL) that provides no
technical value other than the insurance that only applies to e-commerce
sites. I want to prevent a repeat of what I consider misguided history and
add some real security backbone to what is displayed to the end user.
- I want to define the version of TLS that was used (TLS 1.1 or newer in
- The cipher must be RSA2048 or DHE
- The hash must be SHA2 or newer
- The subject name (or SAN) must match the sending domain
- (optional) the cert must be trusted in the root store
- (optional) the cert must have a thumbprint equal to xxx (allows for
self signed certs)
- (optional) DNSSec is used for all certificate operations (to allow
full compatibility with .gov)
I think DMARC can cause great things in MUAs to occur, and I'm elated it's
being proposed but see that incorporating TLS policy and reporting as an
essential component before anything is displayed to the end user as being
On Wed, Jun 20, 2012 at 12:38 AM, John R. Levine <johnl at iecc.com> wrote:
> S/MIME could be an option for some industries, but I'm a finance vertical
>> and we are required to have a supervisory compliance agent review our
>> electronic communications. (See Smarsh.com or Proofpoint Archive as an
> Hmmn. If this is about compliance, I think it's considerably outside the
> scope of what DMARC is intended for. But I'll defer to Murray to explain.
> John Levine, johnl at iecc.com, Primary Perpetrator of "The Internet for
> Please consider the environment before reading this e-mail. http://jl.ly
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