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Date: Thu, 15 Aug 2013 14:31:19 +0400
Subject: Re: HTTPS

On 15-Aug-2013 01:22:33 -0600, Kurt Seifried wrote:

 >>> everyone should be enabling HTTPS where possible,

 >> Very dangerous mistake. HTTPS should be used only for
 >> non-anonymous access, otherwise plain HTTP is preferred.
 >> In any case, let the users choose whether they want to
 >> use it.

 > This is literally the first time I've ever heard anyone say this,
 > I'm curious though, can you explain your reasoning/evidence for
 > this statement?

The reasoning is simple:
1. Not all interceptions and modifications are evil.
2. Some sites are much more evil than interceptors.

 > You do realize HTTPS can be just as "anonymous" (ignoring the
 > fact you have the persons IP/time stamp, browser string, etc =)
 > as normal HTTP.

Yes. And, just in case: HTTPS is used to bypass content-filtering
proxies (ones that cut ads|malware|etc).

 >> Compare to FTP vs SCP/SFTP: first is for getting files from
 >> anyone (into /incoming) and giving files for everyone (from
 >> /pub), second is for transferring your own files. Obviously,
 >> I presume FTP daemon to be configured for anonymous-only access.

 > Now I'm just confused.


 >>> intercepting and modifying HTTP is trivial.

 >> Yes. But intercepting and modifying HTTPS requires just an
 >> ability to issue client-trusted certificates (sufficient for
 >> 99% of HTTPS applications), so the content signing should
 >> always be preferred over distributor validation.

 > And now I'm seriously confused. For clients that do not validate
 > hostnames it would be true that you could get an HTTPS cert for
 > any domain name and use it,

The valid HTTPS certificate doesn't mean getting valid content - it
only means you've connected to (most likely) the right server.

 > this would also work for the case where you first use HTTP to get
 > a redirect to HTTPS

The most annoying behavior... Should be used only when the visitor
wants to log in. IMHO.

 > (the attacker intercepts the HTTP and sends you to an attacker
 > controlled HTTPS).

Unlike SSH, the HTTPS clients (which usually are the browsers) do not
cache the visited servers' certificates, fully relying on issuing CA's
honesty. This introduces a risk of false sence of security.

Hmmmm... It seems that keeping self-signed certificates is even more
safe than relying on "trusted" CAs...

 > Hence ALWAYS using HTTPS!

Ok. But NEVER force the visitors of your site to use it :-)

 > I really suspect you have misunderstood what encrypted network
 > protocols are for. Typically they address three major problems:
 > integrity (attackers modifying traffic en route), confidentiality
 > (by encrypting it)

Do public data really need that?

 > and as an offshoot of these two properties, and the magic of key
 > exchanges you can also handle authentication securely, if desired.

How many sites do use the HTTPS client certificates for authentication?
My estimation: less than 1%, as most use trivial username + password
over the encrypted connection.

Alexey V. Vissarionov aka Gremlin from Kremlin <gremlin ПРИ gremlin ТЧК ru>
GPG key ID: 0xEF3B1FA8, keyserver: hkp://
GPG key fingerprint: 8832 FE9F A791 F796 8AC9 6E4E 909D AC45 EF3B 1FA8

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