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Date: Thu, 15 Aug 2013 06:40:14 -0400
From: Donald Stufft <>
Subject: Re: HTTPS

On Aug 15, 2013, at 6:31 AM, wrote:

> 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.

#1 is technically true but because there's no way to programmatically
determine if a interception or modification is "evil" systems should
default to disallow and allow the user to allow it (by trusting another
CA for instance for the interceptor).

I don't understand how #2 relates to HTTPS at all, TLS doesn't state
anything about the safety of the server you're connecting to only
the safety of the transport. 

>> 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).

This is a false dichotomy. There are plenty of ways to do content-filtering
proxies with HTTPS in a way that will still work.

>>> 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.
> Why?
>>>> 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.

It means you've connected to the right server and no attacker in the
middle has modified the data (nor can they see the data). It makes
no assertion about if the data the server gave you is correct, it only
protects the transport.

>> 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.

This doesn't reflect the state of browser security. You basically need
forced HTTPS or a number of attacks are possible against a typical site.

>> (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…

Or you can use public key pinning via headers like "Public-Key-Pins",
or TLS extensions like TACK. And if you don't want to trust the CAs
there are also solutions like convergence.

>> Hence ALWAYS using HTTPS!
> Ok. But NEVER force the visitors of your site to use it :-)

Completely disagree. HTTPS should by the default and all traffic
should be forced over 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?

Just because data is public doesn't mean you don't want to be assured
that nobody has modified the data between the server and your
computer. It also completely misses the fact that just because data is
public it doesn't mean you want third parties to be able to see that you're
accessing that data.

>> 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

Donald Stufft
PGP: 0x6E3CBCE93372DCFA // 7C6B 7C5D 5E2B 6356 A926 F04F 6E3C BCE9 3372 DCFA

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