Perfect MITM Attacks With No-Check SSL Certs

StartCom writes "In a previous article I reported about Man-In-The-Middle attacks and spotlighted an example showing that they really happen. MITM attacks just got easier. In the attack described previously, untrusted certificates from an unknown issuer were used. Want to make the attack perfect with no error and a fully trusted certificate? No problem, just head over to one of Comodo's resellers. Screenshots and disclosure provided at the link."

Comments

Don't do this at home

[moro_666]

While the link is already being slashdotted ...

I hope the article author understands that unless he's really lucky, he is in deep legal trouble already. It's not the first time that the messenger was slaughtered, although the message was honorable.

Gotta think over the SSL certs one more. I never really liked the mechanism behind it, i like it even less now.

Re:Don't do this at home

[Anonymous Coward]

source of the slashdotted page :

----
In a previous article I reported about Man-In-The-Middle (MITM) attacks and if they really happen. Unfortunately it does happen as some testimonials confirm. Now itâ(TM)s even easier because in the attack described previously, untrusted certificates from an unknown issuer were used. Want to make the attack perfect with no error and fully trusted certificate? No problem, just head over to one of Comodoâ(TM)s resellers.

In an unrelated event which was briefly mentioned at the dev.tech.crypto mailing list of Mozilla, something strange happened. During my attempt to verify and understand who stands behind the sending of fraudulent âoereminderâ email messages tricking our customers, I created a certificate from the source I was following. And my certificate was issued without any further questions.

This prompted me to create another certificate through them, but this time by using a domain name which should never be issued to me. For the purpose of testing, I selected the domain mozilla.com (Iâ(TM)m certain they will forgive me). Five minutes later I was in the possession of a legitimate certificate issued to mozilla.com - no questions asked - no verification checks done - no control validation - no subscriber agreement presented, nothing.

With the understanding about MITM attacks, the severity of this practice is obvious. No encryption is worth anything if an attacker can implant himself between the client and the server. With a completely legitimate and trusted certificate, the attack is perfect. No warning and no error.

--
there you go, have a nice xmas and slashdot less

Re:Don't do this at home

[cp.tar]

Oh, dear. So who certifies the certifiers?

Re:Don't do this at home

[Anonymous Coward]

Pesronally I'd like VISA and Mastercard to give me Root CA certs to use for purchasing on line - then if they foul up and someone gets a dodgy cert then they pick up the bill.

As it is, I don't think anyone would be liable (except yourself) to pick up the cost of shenanigans

Re:Don't do this at home

[betterunixthanunix]

The problem with the system you described is that it relies on end users to understand what is happening. Most FF or IE users have no understanding of what a certificate even is, how it works, or how a MITM attack works. If you told end users that they would pay for identification services, every scam artist on earth would be setting up their own CA and charging users for the root signing certificate, which would then be used for MITM attacks. Worse, the idea that end users could try and verify self-signed certificates is preposterous also, and again, scam artists would be all over it.

From a security standpoint, the current system is pretty much the best you can hope for. People who presumably know what they are doing select your CA roots for you; a mistake there is equivalent to a buffer overflow that allows an attacker to install a key logger. The CAs, wishing to remain in business, have an incentive to do some level of checking on who they issue certificates to: if it became known that a CA was just signing any CSR, with no checks whatsoever, software makers would stop shipping their public key, and legitimate users would not pay for a signature. This, by the way, is the incentive for site owners to buy signatures from competent CAs: an incompetent CA is likely to not have their public key shipped with popular software, so their signatures are worthless.

It's not common for a CA public key to be removed from a software package, because of the ruckus it would create (potentially thousands of websites suddenly having untrusted certificates), but if a CA has truly incompetent practices, then yes, their public key will be removed. In general, software makers try to hold CAs to high standards to get their public key shipped with the software in the first place, so unless the CA itself allows its practices to worsen, it is unlikely that they would find themselves in that position.

Trusting a third party for security is tough, but if you are smart enough to be aware of that, then you should also be aware that you can personally add or remove CA public keys from any software that you use. If you feel that Comodo is untrustworthy, remove their public key, and every time you get a warning, report it to the owner of the website you were trying to visit.

Re:Don't do this at home

[iammani]

Folks who are surprised should definitely check out the list of Certificate Authorities. In Firefox Prefences -> Advanced -> Encryption -> View Certificates -> Authorities Tab

The first one is TÃoeRKTRUST Elektronik Sertifika HizmetSaÄYlayıcısı.

And its much worse in IE -- Internet Option-> Certificates -> Trusted Root Cert. Autho. I have not heard of 25% of the Authorities.

As the wise put it, security is only as strong as the weakest link.

Re:Don't do this at home

[TheLink]

And they don't care about security (nor do the users).

That's why self-signed certs aren't really more risky than CA signed certs in practice.

http://it.slashdot.org/comments.pl?sid=1041927&cid=25890305

http://ask.slashdot.org/comments.pl?sid=534356&cid=23199022

I've probably posted others, but I bet "everyone" is still going to leave the dozens of CA certs in their browsers, and Mozilla and friends aren't going to do the SSH style thing - warn user if the cert changes for whatever reason- even if it's a valid cert.

I'd like to know if my bank's cert suddenly changed from the old cert to some cert signed by some CA in Elbonia. :)

Really now.

[cp.tar]

The example cited is "RESOLVED INVALID". The link to the "perfect attack" seems to be slashdotted. And at the time I started writing this comment, there have been no comments whatsoever.

Does this mean that Slashdotters have all swarmed the link trying to find out how to execute the perfect attack? Are we seeing a new trend here, with people actually reading TFAs?

Or is it that too many people have Greasemonkey scripts filtering out kdawson's posts?

Re:Really now.

[ghmh]

Apparently the perfect attack is actually 'Slashdot in the Middle'

Re:Really now.

[daveewart]

The example cited is "RESOLVED INVALID"

That's because the behaviour reported in the bug (the actual MITM attack) is *not* a problem with Firefox as suspected by the reporter: Firefox was behaving correctly by identifying the SSL certificates as invalid. It is however an interesting report of a MITM attack.

OK, which CA must leave the trusted list?

[Anonymous Coward]

There's only one way the CA system can work: Responsibility and repercussions. If a certificate authority signs forged certificates, then it can no longer be trusted and must be removed from the list of trusted CAs. To trust an untrustworthy CA is a security bug and should trigger updates from all browser developers which remove the offending CA. Make the CAs work for their money.

Re:OK, which CA must leave the trusted list?

[timeOday]

How can we trust that the list of trusted CAs is valid and up to date? Who maintains this list? Me? You? The Scam Artists? A central trust agency? The Government?

Go ahead and accuse me of not being libertarian, but yes, I think making and enforcing standards for CAs is a good role for the government. I would never put my money in an unregulated bank, or send premiums to an unregulated insurer, or go to a back-alley doctor.

Re:OK, which CA must leave the trusted list?

[Vellmont]

but yes, I think making and enforcing standards for CAs is a good role for the government.

Which "the government" are you talking about here? You might have noticed the internet is worldwide, and there's no single authority to control it. Browser makers are also free to put whatever CA's root certificates in their browsers that they wish (along with all anyone else who distributes software that uses an x509 certificate).

Re:OK, which CA must leave the trusted list?

[timeOday]

I guess this is my fault for mentioning libertariansm in the first place. For the record, I think it's a great idea in an imaginary perfect world where everybody has complete access to all information, dishonesty is abolished, natural resources are infinite (so each of us can breathe our own air, etc), and everybody starts life on equal footing (access to education, proclivity to illness, etc). Which is to say, it's exactly as practical as Communism and every other idealization that never seems to get fully proven or disproven because it can never actually exist.

Another reference

[Slite01]

While the original blog is slashdotted, please enjoy this link to Google Groups: http://groups.google.com/group/mozilla.dev.tech.crypto/browse_thread/thread/9c0cc829204487bf?pli=1

Re:Sensationalist - reroute & self signed cert

[bunratty]

In the perfect attack, the certificate is issued by a trusted certificate authority, so no warning is shown. It truly is a perfect MITM attack. We do know exactly who is issuing certificates without verifying the identify of the individuals requesting them. It's time for browser makers to remove some trusted CAs from their lists so users can be secure.

Big trouble at PositiveSSL.

[Animats]

The article is confusing, and the author declines to name the certificate issuer that's the problem. But the screenshot gives the details. It's PositiveSSL. He really did get PositiveSSL to issue him a Comodo-authorized cert in the name of "www.mozilla.com". Try this link and look at the certificate details.

It looks like certificates with this issuer information need to be rejected:

• CN = PositiveSSL CA
• O = Comodo CA Limited
• L = Salford
• ST = Greater Manchester
• C = GB

I loaded all current Comodo certificate revocation lists, and this bogus certificate has not been revoked.

Some Comodo CA root certificate needs to be removed from the approved list.

Addtrust, and Comodo.

[Animats]

Looking at this cert further, it's a very wierd certificate. "Issuer" of ""www.mozilla.com" has "O=Comodo CA Limited". That's descended from "Positive SSL CA", for which "Issuer" has "O = The USERTRUST Network". That's descended from "UTN-USERFirst-Hardware", for which Issuer has "O = AddTrust AB". That's descended from "AddTrust External CA Root". Why is a Comodo cert being issued under AddTrust? Comodo is a root CA itself, with its own root certs in major browsers. Something is not right here.

So who's AddTrust? Their web site says "Under Reconstruction". This does not look good. Checking the Internet Archive, we find "JOIN THE ADDTRUST FAMILY Gain an edge over your competitors by providing co-branded PKI services"

AddTrust went beyond using resellers. They apparently allowed subordinate CAs to issue certs in AddTrust's name: AddTrust's rapid Trust Service Provider (Licensee) start-up package allows you to deliver cutting-edge public key infrastructure (PKI) services cost-effectively and in a way that best complements your business model. Literally within months you can start selling pre-packaged outsourced PKI services allowing your customers ... AddTrust's globally recognized PKI brand is designed for co-branding with companies recognized for high-quality IT services and products. ... Rather than relying on external certification authorities, you can easily provide high-end certificates yourself by becoming an AddTrust-licensed Trust Service Provider. This allows you to decide how much of the underlying secure infrastructure you want to run and invest in yourself.

The relationship between Comodo and AddTrust is mentioned in this email. Robin Aldin of Comodo wrote: There is no ongoing relationship with AddTrust AB, Sweden. I'm not even sure if AddTrust AB still exists as a company. I think AddTrust may exist now only as a brand of ScandTrust AB. Sweden - although Comodo does have the right to continue using the root CA certificates which we purchased from them and which bear the AddTrust name.

So the party ultimately responsible for this certificate is out of business?

Firefox is right to warn.

[tjstork]

The company that I worked at used a MITM attack with self signed certificates to read everyone's HTTPS stuff during the financial crisis. I was quite surprised to find that my bank and my broker's certificates were rejected by my Firefox, and that, upon inspection, the issuer was actually my company. IE, company issued, didn't warn me, and neither did Chrome, and I have to confess that when Firefox complained, I would often switch to Chrome, because it didn't. Then, one day I looked at the certificate in Firefox, and I discovered just what that warning meant. My company was spying on me.