[whatwg] meta="encrypt" tag is needed

Aryeh Gregor Simetrical+w3c at gmail.com
Fri May 7 13:18:58 PDT 2010

On Fri, May 7, 2010 at 1:06 PM, Juuso Hukkanen <juuso_html5 at tele3d.net> wrote:
> You asked many questions, and unfortunately all you missed the
> auth="verisign" argument, which _is_ enough to prevent all practical (,even
> if they are all theoretical!,) man-in-the-middle attacks.

You haven't explained what it does.  Did you mean that the <meta> tag
should include a certificate as well as a public key?  If so, how is
that better than HTTPS?

> Maybe someone can show a _complete_ alternative Javascript & https solution
> about how those can be achieved in a computer or PDA-device without
> javascript support.

Just serve the page using HTTPS, and have a normal HTML form.  It will
transmit the username, and the password.  The server can  salt and
hash the password.  (You could also easily have the client salt and
hash the password using JavaScript before submission, but this doesn't
improve security once you're using HTTPS.)

> I am not suggesting replacing https with anything, government and business
> sites can and should keep on using it.  I am suggesting a small easy to use
> mini-encryption which would be enough for those 90% of sites should salt
> their passwords and encrypt sensitive data and but who currently aren't.

It is not sufficient, because it's trivially circumventable by a
man-in-the-middle attack.  It therefore provides no security against
any attacker.  It also provides no greater assurance of security on
the server side, because anyone who's competent enough to include this
meta tag will probably also be competent enough to hash and salt
passwords on their own.

> Most servers are already configured to read the requested pages before
> submitting those over the internet.

I'm not aware of any HTTP server that attempts to parse outgoing HTML
content.  Could you provide a specific example?  In particular, I'm
rather certain that neither Apache, nor IIS, nor lighttpd parse
outgoing HTML pages, and that accounts for most servers already.

> For example my above form-page has a
> small php-script inside which the server program must notice; as the
> PHP-program needs to compile the script. Client never sees the <?php echo
> $_SERVER['PHP_SELF']; ?> part but is instead shown an URL. To implement
> meta-encrypt tag would just require (on/off) configuring server program to
> read the header of requested page and see if there is a meta-encrypt tag in
> there the server calls a program which decrypts! the client submitted data.

This requires HTTP servers to implement an HTML parser, and to run it
every time a page is submitted.  They don't actually do this right
now.  HTML parsing is actually very complicated and slow -- have you
looked at the HTML parsing algorithm

> 1) Man-in-the-middle problem; which doesn't exists because
>        a) those are just academic mind games

If so, there's no reason for encryption at all.  You can just send the
content unencrypted if no one is going to intercept it.

>        b) if auth="verisign" is used as external CA

Saying who the CA is is not enough to certify it.  You need to provide
the actual certificate, e.g., in X.509 format
<http://en.wikipedia.org/wiki/X.509>.  To get a certificate, you will
typically have to pay a CA some sum of money, making it prohibitive
for casual sites.  What's the advantage over HTTPS at this point?

> 2) HTTPS = good (even if it is typically NOT used with forms

Many sites use HTTPS for everything, including login.  Most sites
don't, but that's mainly because 1) it's hard to get a certificate
(you don't solve this), and 2) it doesn't work well with shared
hosting (there are better solutions to this in progress).

> 3) password salting = webmasters duty to do it (which 50% forget), after

Then why will they remember to add the <meta> tag you suggest?
They'll just forget both.  This is a problem, but the only solution is
to have the browser act more securely by default, regardless of what
the webmaster does.

> 4) Declaring encrypt action doesn't fit into HTML (; then why is there a
> form method get/post)

HTML is the wrong place to do encryption, because once you receive the
page, it might have already been tampered with.  The entire connection
needs to be specified as secure-only from the beginning, such that the
client will abort if it receives unencrypted/unauthenticated content.
This is what HTTPS does.  By the time you get to the actual contents
of the document, it's impossible to know whether it's been secured.

You haven't explained yourself very clearly, but in summary, this is
what I think you're trying to do and why it doesn't work:

1) You're trying to provide protection against MITM attacks that's
easier to use than HTTPS.  This fails, because a) you still need a
certificate (the most annoying part of HTTPS), and b) an MITM could
just alter the outgoing HTTP request to remove the encryption request,
get the plaintext reply, and encrypt that itself, with the client none
the wiser.  (But you seem to say you don't think MITM is a serious
problem, so I don't know why your proposal includes encryption at

2) You're trying to provide a different way for authors to salt and
hash passwords.  This is a useful goal, but your proposal doesn't do
it, because there's no reason to believe authors will know to use the
<meta> tag if they don't already know to salt and hash on the server
side.  Mozilla's Account Manager
<https://mozillalabs.com/blog/2010/03/account-manager/> is a step in
this direction that aims to solve this problem and others, and
encourages webmasters to comply by making their non-compliance obvious
and (potentially) making their life easier.

You really need to explain 1) why your proposal is actually better
than HTTPS, and 2) why you think your tag will actually encourage more
authors to salt and hash their users' passwords.  Taking a defensive
or dismissive stance will not help your proposal.

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