| |||||||||||||
Langley: False Start's FailureLangley: False Start's FailurePosted Apr 13, 2012 5:33 UTC (Fri) by nmav (subscriber, #34036)Parent article: Langley: False Start's Failure
This post describes the case of almost any extension or updates to TLS. If one wants to inter-operate with every server on the internet he has to support a fallback mode without any extensions and talk the 16-year old SSL 3.0. Browsers could mitigate by showing an informational message though, that either the connection is not optimal on this server (for false start), or notify it uses a protocol with known weaknesses (i.e. SSL 3.0). No browser does that, and as a result, the owners of broken servers have no incentive to change.
(Log in to post comments)
Langley: False Start's Failure Posted Apr 13, 2012 6:12 UTC (Fri) by hitmark (guest, #34609) [Link]
You mean messages like the "danger, Will Robinson!" style message that Firefox throws in my face each time it encounters a certificate with some issue or other?
Langley: False Start's Failure Posted Apr 13, 2012 9:48 UTC (Fri) by nmav (subscriber, #34036) [Link]
I don't know what kind of messages you refer to, but I suppose an issue in the certificate is quite important. Would you prefer not to know that the
session could be insecure?
Scary SSL warnings Posted Apr 13, 2012 10:28 UTC (Fri) by man_ls (subscriber, #15091) [Link] I for one would prefer if browsers could distinguish between insecure and unverified, so that every time I browse a non-critical page protected with a self-signed certificate I didn't get a scary warning (like in puszcza.gnu.org.ua/). This warning is the same as for a spoofed certificate, which don't present the same risks at all. Or with expired certificates which have a different set of issues.I understand that this scheme helps the prime-numbers mafia (aka the certification authorities racket), which for $17/year rents you a prime number that takes a few milliseconds of CPU time to generate. But I don't appreciate it. At least it seems that modern browsers now include CACert as a root authority, so perhaps the situation will unravel in a few years. Applying Hanlon's (or Heinlein's) razor), it must be easier to just pop up the warning than worry about how to make the distinction between a spoofed and a self-signed certificate.
Scary SSL warnings Posted Apr 13, 2012 11:26 UTC (Fri) by pataphysician (guest, #73773) [Link]
The errors are actually different, but only in the "Technical Details" area, which by default is not shown in detail. There is a firefox extension charmingly called MitM Me, that will allow you to set exactly how you want to handle self-signed certificates, from cutting down the number of clicks to authorize, all the way to completely quiet mode.
Scary SSL warnings Posted Apr 13, 2012 11:29 UTC (Fri) by Jan_Zerebecki (guest, #70319) [Link]
You could install an extension to your browser that used a different policy for certificate verification.
The default policy encoded in Firefox is like that for a good reason. Here is my try at explaining it, but it is my first try done in a hurry, so take it with a grain of salt: For the intended audience insecure and unverified are the same thing. Because the browser should never show them a page that is not secure if a https link is clicked, because they are assumed not to be able to notice it. As the Browser has no knowledge about if this site you entered is intended to be unverified of if it is just a spoofed self signed certificate the Browser can not differentiate between unverified and unsecure.
Does that sufficiently explain it and makes sense? I'm really interested, because your argument against what Firefox does is often told.
Scary SSL warnings Posted Apr 13, 2012 12:50 UTC (Fri) by ibukanov (subscriber, #3942) [Link]
A site with a self-signed certificate is not worse than a site without SSL. The problem is that many users were trained to look for the "s" after http and assumed that https means both secure and verified.
However, this is a lesser problem now with all those efforts the browsers invested in annotating the address line according to the verification status. For example, I tell to everyone among family/friends to look for colors on URL and just ignore http/https difference. If one need to do banking or enter a credit-card number, then the page URL should be green in FireFox. If it is just blue, be suspicious!
So I think it is time for browsers to change the policy and handle by default self-signed pages the same way as plain http pages and indeed stop that prime number scam.
Scary SSL warnings Posted Apr 13, 2012 13:22 UTC (Fri) by sorpigal (subscriber, #36106) [Link]
Just come up with a way to visually distinguished Verified vs Not-Verified in addition to SSL vs No-SSL and call it a day.
If browser vendors were really interested in communicating with users about whether they're safe then non-encrypted http connections would be flagged with a scary, red URL bar with a clickable information button which describes the dangers of browsing unencrypted. Saying that "Users expect https to be safe" is just making excuses; users expect "green" to mean safe, not S.
Scary SSL warnings Posted Apr 14, 2012 0:06 UTC (Sat) by josh (subscriber, #17465) [Link]
> Just come up with a way to visually distinguished Verified vs Not-Verified in addition to SSL vs No-SSL and call it a day.
If browsers had started out by never showing users the protocol (http versus https) and treating https with an unverifiable certificate as identical security to http, then sure, we could have opportunistic encryption today that would at least protect against passive packet sniffing, and users would know to look for the verification information rather than the protocol string. But with the state of browsers today, allowing https with an unverifiable certificate would let users get exploited.
Scary SSL warnings Posted Apr 14, 2012 12:27 UTC (Sat) by Jan_Zerebecki (guest, #70319) [Link]
The differentiation between http and https is also a technical part of the security. Take the following example:
Request 1 to https://example.com/ is verified to be signed by a trusted CA. This triggers the rainbows and padlocks in the UI, all went fine security wise. The user fills out a form on the page and sends it, now Request 2 is POSTed to the same URL. This time a self signed certificate is used because a MAn in the Middle attack happened. In your proposed change there is nothing available to let the Browser differentiate between a successful attack that uses a self-signed certificate and the correct certificate. That is because in the current scheme of things there is no client state about the identity of a site.
Poking holes in this argument is welcome.
HTTP Strict Transport Security changes this, but it doesn't have a mechanism for the initial distribution of the identity. One could put this HSTS information in DNSSEC (there are proposals for that). (Additionally allowing only the public key or the hash without HSTS in DNSSEC is IMHO important.)
That would solve most of the problems of the current system I know of. It doesn't need any flag day and can be used by those who want without cooperation from anyone else. It makes it easier for the untrained user to be more secure than the current mechanisms.
But there are downsides: It is much more complicated for the administrators of the system. (Although it scales, i.e. one knowledgeable person can ensure it works for basically unlimited systems once the procedures and software is in place. But if you trust your DNS Server operator he could do this for you and what is left is not really more complicated than it is now.) And the software neither on the client nor on the server is yet finished (never mind deployed).
What is left is the standardization, implementation work and convincing your browser vendor to ship such an implementation (not in that order). If that wasn't enough work I fully expect someone to find some legacy related use case that would prevent all of this (just as with IPv6, HTTP Pipelining, TCP ECN, etc...).
Probably that in the absence of saved HSTS records for a host you must decide between being vulnerable to downgrade to the current CA model or being disconnected from any HTTPS site in parts of the internet DNSSEC queries are broken in. That may be because fully (from the root) resolving without an intermediary is somehow filtered outside of your control (i.e. DNS is blocked) and the resolver assigned to you (also outside of your control) does strip or choke on DNSSEC.
Does anyone know if that is a problem in practice and how widespread it might be? Or any other problems with this way of solving it?
Scary SSL warnings Posted Apr 16, 2012 13:53 UTC (Mon) by nye (guest, #51576) [Link]
>The user fills out a form on the page and sends it, now Request 2 is POSTed to the same URL. This time a self signed certificate is used because a MAn in the Middle attack happened. In your proposed change there is nothing available to let the Browser differentiate between a successful attack that uses a self-signed certificate and the correct certificate. That is because in the current scheme of things there is no client state about the identity of a site.
Realistically, there should be.
Even aside from how you want to treat self-signed certificates, a browser should think something's up if the certificate for a given URL changes between two requests, unless the first certificate was right on the edge of its expiration date. Keeping a record of the certificate received on the last request would be an improvement even if you continue to treat self-signed certificates the same way.
Do any browsers currently do that?
Scary SSL warnings Posted Apr 13, 2012 20:09 UTC (Fri) by josh (subscriber, #17465) [Link]
> I for one would prefer if browsers could distinguish between insecure and unverified
"unverified" means "insecure"; if you don't verify certificates, a MITM attack can trivially substitute any other certificate and you'll accept it.
And these days you can get an SSL certificate for free that all browsers will accept (http://www.startssl.com/).
Scary SSL warnings Posted Apr 14, 2012 9:04 UTC (Sat) by man_ls (subscriber, #15091) [Link] Thanks for the pointer. Unverified and insecure are different, at least technically. I may have a secure connection which is not verified, possibly because I have verified it using some other means. But you are quite right that the difference is not well explained that way.
Scary SSL warnings Posted Apr 14, 2012 13:44 UTC (Sat) by Jan_Zerebecki (guest, #70319) [Link]
Taken outside of the context or as concepts unverified and insecure are different. But in the context of the current browser security model they are indistinguishable, even when one were to ignore any usability concerns and focus solely on the technical details. See my previous post in this thread for an example of a transaction that shows this.
The Firefox implementation as opposed to an implementation that doesn't allow you to save the site identity actually allows the user telling the browser he can distinguish unverified and verified sites. As adding the permanent exception can be used as trust on first use like known from SSH, because the exception is only valid for one host and certificate. (Although the implementation probably does not do pinning to only this verified key, but I didn't check. Does anyone know? But that can be solved by the host doing HSTS.) But using that safely requires complicated special knowledge which makes the scariness a necessity of good usability.
This means with Firefox you can have secure sites that are verified and different secure sites that are unverified, as long as you don't confuse them.
Scary SSL warnings Posted Apr 14, 2012 20:27 UTC (Sat) by dkg (subscriber, #55359) [Link] what do you mean by "secure" though? When pressed, most people usually unpack "secure" into a combination of "confidential" and "integrity-checked".TLS operates in a bi-directional stream communication, so the identity of the other party (the peer) is critical. "confidential" means "only myself and the peer can read this". But if you don't know who the peer is, you cannot have meaningful confidentiality. "only myself and some mystery party can read this" is not confidential. The mystery party could very well be an adversary. "integrity-checked" means "only the peer could have written what i'm reading". Again, if you don't know who the peer is, you cannot have meaningful integrity-checking. "Only some mystery party could have written this" is not integrity-checked. The mystery party could very well be an adversary. So without identity verification of the remote endpoint, your communications are neither integrity-checked nor confidential in any meaningful way. This is not to say that modern certificate management practices (in browsers or elsewhere) are good -- they're horrible and need serious improvement. But we shouldn't pretend that we can have secure communications without some form of strong verification of the peer's identity.
Scary SSL warnings Posted Apr 14, 2012 21:05 UTC (Sat) by man_ls (subscriber, #15091) [Link] If you are willing to get into these depths you have to acknowledge (as you implicitly did) that with current certificate management techniques, the remote end is not really verified, and communications are neither confidential nor integrity-checked. Browsers are only checking that the remote end has a certificate which was issued by one of the stored certification authorities or their subsidiaries. Users could be man-in-the-middled to death and would not know it, and recent security incidents with subordinate root certificates just prove the point.The real point is security is only important when it is needed. "Secure and verified" means, in this context, "Good enough so I can send credit card information through it". "Secure but unverified" stands for: "Good enough as long as you don't send important information". I don't need security to access https://puszcza.gnu.org.ua/. I need a little security for Facebook, although mostly I need some privacy: a MitM would only be a small worry (witness the firesheep experiments and how most people just continued browsing after a while). I need the strong version of security to connect to my bank -- and not the kind where my corporate network can MitM me. As long as we are stuck in the land of protocols, certificates, channels and networks we are losing sight of our real objective.
Scary SSL warnings Posted Apr 14, 2012 22:01 UTC (Sat) by dkg (subscriber, #55359) [Link] I agree with you that the current mechanisms don't provide reliable identity verification. That's why i contribute to projects like the monkeysphere, and why i'm glad that projects like convergence and sovereign keys exist. None of them are perfect, but they're pointing in the direction of improved identity verification infrastructure.However, I disagree with your focus on commerce and financial transactions as the only things in need of confidentiality and integrity-checking. Surveillance, censorship, invasive advertising, infiltration of private groups, and other forms of social control pose real and growing potential for abuse as we move more of our society online. Ubiquitous confidential and integrity-checked communication would make it much harder for any would-be abuser to succeed. Please don't encourage the idea that secured communications are only relevant for financial communications.
Scary SSL warnings Posted Apr 14, 2012 22:20 UTC (Sat) by man_ls (subscriber, #15091) [Link] Sorry about that. Of course: it was just an example of some information which I don't want others to see. I could have used my medical record, my private company files or even my webmail (and for people under certain governments this is a very real threat). For me Facebook is just a (barely used) form of entertainment, for others it can be the way to share vital confidential information.It is a pity that governments don't treat online communications with the same degree of respect as traditional mail or even telephone communications. Those technologies were easily abused but quite protected by law. Nowadays, if we are not allowed our privacy by way of the law, we must seek technical measures. But let's put things into perspective: I would not care so much if most of my traffic was MitMed, even on sites as lwn.net (except on those rarest of occasions when I enter my password or my credit card info). Security is a set of trade-offs: If I was to support something like HTTPS everywhere, I would prefer if browsers could act sensibly on self-signed certificates so websites did not rely on central authorities. Or if those projects you mention were practical alternatives to the prime numbers racket that are current certificate authorities -- from recent comments here on LWN.net it seems they are not there yet but advancing pretty fast.
Langley: False Start's Failure Posted Apr 13, 2012 18:39 UTC (Fri) by jhardin (guest, #3297) [Link] has to support a fallback mode without any extensionsAgreed. I don't see why they're just chucking the whole thing, though (modulo NPN). Why not keep the list of "problem servers" for which which False Start is not attempted, and if False Start fails with a server not on the list, add that server to the list and retry without False Start? That should be a fairly small change that would retain the benefits of False Start for the majority of the Internet (at least up until checking the dynamic exclusion list, which should remain short, takes longer than the time saved by using False Start), while avoiding recurring issues with non-deterministic problem sites.
|
|||||||||||||