Why do browsers show ugly errors for untrusted SSL certificates?

When faced by an untrusted certificate, every single browser I know displays a blaring error like this:

Why is that?

This strongly discourages web developers to use an awesome technology like SSL out of fears that users will find the website extremely shady. Ilegitimate (ie: phishing) sites do fine on HTTP, so that can't be a concern.

Why do they make it look like such a big deal? Isn't having SSL even if untrusted better than not having it at al开发者_StackOverflowl?

It looks like I am being misunderstood. I am taking issue with the fact that HTTP sites cannot be more secure than an HTTPS site, even if untrusted. HTTP doesn't do encryption or identification. Phishers can make their sites on HTTP and no warnings are shown. In good faith, I am at the very least encrypting traffic. How can that be a bad thing?

They do that because a SSL certificate isn't just meant to secure the communication over the wire. It is also a means to identify the source of the content that is being secured (secured content coming from a man in the middle attack via a fake cert isn't very helpful).

Unless you have a third party validate that you are who you say you are, there's no good reason to trust that your information (which is being sent over SSL) is any more secure than if you weren't using SSL in the first place.

SSL provides for secure communication between client and server by allowing mutual authentication, the use of digital signatures for integrity, and encryption for privacy.

(apache ssl docs)

Yep, I don't see anything about third party certificate authorities that all browsers should recognize as "legit." Of course, that's just the way the world is, so if you don't want people to see a scary page, you've got to get a cert signed by someone the browsers will recognize.

or

If you're just using SSL for a small group of individuals or for in-house stuff, you can have people install your root cert in their browser as a trusted cert. This would work fairly well on a lan, where a network admin could install it across the entire network.

It may sound awkward to suggest sending your cert to people to install, but if you think about it, what do you trust more: a cert that came with your browser because that authority paid their dues, or a cert sent to you personally by your server admin / account manager / inside contact?

Just for shits and giggles I thought I'd include the text displayed by the "Help me understand" link in the screenshot in the OP...

When you connect to a secure website, the server hosting that site presents your browser with something called a "certificate" to verify its identity. This certificate contains identity information, such as the address of the website, which is verified by a third party that your computer trusts. By checking that the address in the certificate matches the address of the website, it is possible to verify that you are securely communicating with the website you intended, and not a third party (such as an attacker on your network).

For a domain mismatch (for example trying to go to a subdomain on a non-wildcard cert), this paragraph follows:

In this case, the address listed in the certificate does not match the address of the website your browser tried to go to. One possible reason for this is that your communications are being intercepted by an attacker who is presenting a certificate for a different website, which would cause a mismatch. Another possible reason is that the server is set up to return the same certificate for multiple websites, including the one you are attempting to visit, even though that certificate is not valid for all of those websites. Chromium can say for sure that you reached , but cannot verify that that is the same site as foo.admin.example.com which you intended to reach. If you proceed, Chromium will not check for any further name mismatches. In general, it is best not to proceed past this point.

If the cert isn't signed by a trusted authority, these paragraphs follow instead:

In this case, the certificate has not been verified by a third party that your computer trusts. Anyone can create a certificate claiming to be whatever website they choose, which is why it must be verified by a trusted third party. Without that verification, the identity information in the certificate is meaningless. It is therefore not possible to verify that you are communicating with admin.example.com instead of an attacker who generated his own certificate claiming to be admin.example.com. You should not proceed past this point.

If, however, you work in an organization that generates its own certificates, and you are trying to connect to an internal website of that organization using such a certificate, you may be able to solve this problem securely. You can import your organization's root certificate as a "root certificate", and then certificates issued or verified by your organization will be trusted and you will not see this error next time you try to connect to an internal website. Contact your organization's help staff for assistance in adding a new root certificate to your computer.

Those last paragraphs make a pretty good answer to this question I think. ;)

The whole point of SSL is that you can verify that the site is who it says it is. If the certificate cannot be trusted, then it's highly likely that the site is not who it says it is.

An encrypted connection is really just a side-benefit in that respect (that is, you can encrypt the connection without the use of certificates).

People assume that https connections are secure, good enough for their credit card details and important passwords. A man-in-the-middle can intercept the SSL connection to your bank or paypal and provide you with their own self-signed or different certificate instead of the bank's real certificate. It's important to warn people loudly if such an attack might be taking place.

If an attacker uses a false certificate for the bank's domain, and gets it signed by some dodgy CA that does not check things properly, he may be able to intercept SSL traffic to your bank and you will be none the wiser, just a little poorer. Without the popup warning, there's no need for a dodgy CA, and internet banking and e-commerce would be totally unsafe.

Why is that?

Because most people don't read. They don't what what https means. A big error is MANDATORY to make people read it.

This strongly discourages web developers to use an awesome technology like SSL out of fears that users will find the website extremely shady.

No it doesn't. Do you have any evidence for that? That claim is ridiculous.

This strongly encourages developers and users to know whom they are dealing with.

"fears that users will find the website extremely shady"

What does this even mean? Do you mean "fears that lack of a certificate means that users will find the website extremely shady"?

That's not a "fear": that's the goal.

The goal is that "lack of a certificate means that users will find the website extremely shady" That's the purpose.

Judging from your comments, I can see that you're confused between what you think people are saying and what they are really saying.

Why do they make it look like such a big deal? Isn't having SSL even if untrusted better than not having it at all?

But why do they have to show the error? Sure, an "untrusted" cert can't be guaranteed to be more secure than no SSL, but it can't be less secure.

If you are solely interested in an encrypted connection, yes this is true. But SSL is designed for an additional goal: identification. Thus, certificates.

I am not talking about certs that don't match the domain (yes, that is pretty bad). I am talking about certs signed by authorities not in the browser's trusted CA's (eg: self-signed)

How can you trust the certificate if it is not trusted by anyone you trust?

Edit

The need to prevent man-in-the-middle attacks arises because you are trying to establish a privileged connection.

What you need to understand is that with plain HTTP, there is absolutely no promise of security, and anyone can read the contents passed over the connection. Therefore, you don't pass any sensitive information. There is no need for a warning because you are not transferring sensitive information.

When you use HTTPS, the browser assumes you will be transferring sensitive information, otherwise you would be using plain HTTP. Therefore, it makes a big fuss when it cannot verify the server's identity.

Why is that?

Because if there's a site that's pretending to be a legit site, you really want to know about it as a user!

Look, a secure connection to the attacker is no damn good at all, and every man and his dog can make a self-signed certificate. There's no inherent trust in a self-signed cert from anyone, except for the trust roots you've got installed in your browser. The default set of trust roots is picked (carefully!) by the browser maker with the aim that only CAs who only act in a way to secure trust will be trusted by the system, and this mostly works. You can add your own trust roots too, and if you're using a private CA for testing then you should.

This strongly discourages web developers to use an awesome technology like SSL out of fears that users will find the website extremely shady. Ilegitimate (ie: phishing) sites do fine on HTTP, so that can't be a concern.

What?! You can get a legit certificate for very little. You can set up your own trust root for free (plus some work). Anyone developing and moaning about this issue is just being lazy and/or over-cheap and I've no sympathy for such attitudes.

Ideally a browser would look for information that you want kept secure (such as things that look like credit card numbers) and throw that sort of warning up if there was an attempt to send that data over an insecure or improperly-secured channel. Alas, it's hard to know from just inspection whether data is private or not; just as there's no such thing as an EVIL bit, there's also no PRIVATE bit. (Maybe a pervasive metadata system could do it… Yeah, right. Forget it.) So they just do the best they can and flag up situations where it is extremely likely that there's a problem.

Why do they make it look like such a big deal? Isn't having SSL even if untrusted better than not having it at all?

What threat model are you dealing with?

Browser makers have focused on the case where anyone can synthesize an SSL certificate (because that's indeed the case) and DNS hacks are all too common; what the combination of these means is that you can't know that the IP address you've got for a host name corresponds to the legitimate owner of that domain, and anyone can claim to own that domain. Ah, but you instead trust a CA to at least check that they're issuing the certificate to the right person and that in turn is enough (plus a few other things) to make it possible to work out whether you're talking to the legitimate owner of the domain; it provides a basis for all the rest of the trust involved in a secure conversation. Hopefully the bank will have used other unblockable communications (e.g., a letter sent by post) to tell people to check that the identity of the site is right (EV certs help a little here) but that's still a bit of a band-aid given how unsuspicious some users are.

The problems with this come from CAs who don't apply proper checks (frankly, they ought to be kicked off the gravy train for failing their duty) and users who'll tell anyone anything. You can't stop them from deliberately posting their own CC# on a public message board run by some shady characters from Smolensk^[1], no matter how stupid an idea that is…

^[1] Not that there's anything wrong with that city. The point would be the same if you substituted with Tallahassee, Ballarat, Lagos, Chonqing, Bogota, Salerno, Durban, Mumbai, … There are scum all over.