[aklug] Re: Tor + Firefox

From: Christopher Howard <christopher.howard@frigidcode.com>
Date: Tue Feb 14 2012 - 17:10:19 AKST

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On 02/14/2012 03:44 PM, Arthur Corliss wrote:
> On Tue, 14 Feb 2012, Christopher Howard wrote:
>
>> Wikipedia's cert is not self-signed, but is signed by DigiCert
>> Inc. At present, I do not accept any self-signed certificates.
>
> Isn't that just a tad silly? For any site that you're merely a
> reader on (no logons, just browsing) how does rejecting self-signed
> certs make you any safer? CAs offer one marginally useful
> service: authentication of parties. If all you care about is the
> ability to peruse a site without a third party being able to
> monitor specific requests (never mind the obvious fact that
> CA-signed or not, they always know who you're connecting to,
> barring proxy services) then self-signed is perfectly fine. You
> still have transport encryption.
>

You're assumption that verifying origin of content is not important as
long as you are only reading ("perusing") it is not a valid one. First
of all, if a MITM were to occur (which is what would be happening if
you accepted a self-signed certificate belonging to someone who did
not actually control the domain with which you wanted to communicate)
the attacker would be able insert malicious content (dangerous
JavaScript, e.g.) or even completely replace the site.

Furthermore, the integrity of purely "informational" sites can often
be quiet significant. For example, I have complained to gentoo.org for
not providing HTTPS support for the documentation pages which give
information regarding the installation and verification of their code
signing keys (including the fingerprints). Similar things could be
said for names, phone numbers, addresses, news, and so on.

Obviously after you have decided to trust the self-signed cert, these
matters are not a concern. But when you first arrive at a site with a
self-signed cert, you must either go to some other measure to verify
the validity of the cert, or you must blindly accept it and gamble on
it not being a MITM. As a general rule, I am not willing to take the
latter course.

>> I trust the global CA because it is practical to do so and still
>> maintain reasonable security expectations. Finding a certificate
>> that has been assigned by a global CA gives me a reasonable
>> assurance that the host I am communicating with is one operated
>> by the person or group that owns the domain I am attempting to
>> contact. This is, of course, because global CAs when issuing
>> certificates will, at the least, do a domain registration
>> validation to ensure that the customer has control over the
>> domain he purports to own. Furthermore, global CAs interest in
>> preserving their reputations as CAs.
>
> Not to pile on, but given the recent CAs that have been hacked, how
> wise is it to trust a global CA? CAs offer a great service in
> theory, but it's the implementation that'll kill you. And I
> wouldn't be surprised if the "global" CAs are lax in many security
> aspects.
>

How many actual invalid certificates have been released, compared to
the total number of certificate issued? (Say, for the year.) I'm not
saying the global CA system is 100% perfect, but if it is even
99.9999% reliable then it makes sense to me.

And as I said, with browsers like Firefox, every time one of the
hacking incidents occurs, it comes up on the mailing lists, often with
a huge debate over whether the CA should be dropped from the default
list. So, if you see that particular CA is getting hacked more than
you like or implementing poor security practices, you are free to
delete that CA's cert from your collection.

>
> It works, but even they've demonstrated that it leaves you at risk
> in many circumstances. Just keep your eyes open, and understand
> that the mozilla committee isn't validating the IT solutions and
> security of any of the CAs out there. And when it fails, as it
> has, they're going to be *re*active, not proactive, and remove root
> CA certs only after their assumptions of their reliability has been
> proven wrong. Not before.
>

No arguments there. A person is free to be as proactive as he wants to
be in maintaining his CA cert collection.

- --
frigidcode.com
theologia.indicium.us
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Received on Tue Feb 14 17:07:38 2012

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