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Some Bitdefender products break HTTPS certificate revocation

Lucian Constantin | Feb. 27, 2015
This allows man-in-the-middle attackers with access to revoked, but otherwise valid, certificates to manipulate encrypted traffic.

Disabling the HTTPS scanning feature in Bitdefender products is "definitely not an option," Cosoi said. Aside from this functionality being needed to detect potential malware served from HTTPS websites, it's also used for parental control, identity protection and several other features, he said.

Eiram believes that while not critical, the issue is more serious than Bitdefender estimates. However, he praised the company for its fast response. A one to two week turnaround from a vendor is usually very quick and a solid response time, said the researcher, who's a member of the CVE Editorial Board.

The Bitdefender products generate separate self-signed root certificates for every system they're installed on, so they don't have the same flaw as Superfish or the other programs that were found to be using the poorly designed Komodia HTTPS interception library.

The company's products also check that certificates presented by websites are not expired, are for the correct domain and are issued by a trusted certificate authority, unlike PrivDog, a program that was recently found to intercept HTTPS traffic in an insecure manner.

In order to exploit the certificate revocation oversight in Bitdefender products attackers would need to have a legitimate certificate for a website that has been revoked, as well as its corresponding private key. They would also need to be in a position to intercept connections between affected users and that website.

This can be done through DNS hijacking, compromising routers, ARP spoofing, impersonating Wi-Fi access points -- known as evil twin attacks -- and other techniques. Depending on where the attack is executed it could affect a small number of users -- for example those on a local area network -- or a large population, if done higher up in the Internet infrastructure by someone like the NSA or a country's government.

It would be considerably harder than targeting users of PrivDog, Superfish or Komodia-based products, but far from impossible.

First of all, attackers injecting data into HTTPS traffic, like the malicious payloads mentioned by Bitdefender, is not the only threat, Eiram said. Extracting sensitive information from it, including authentication tokens that would allow attackers to take over accounts, would also be possible.

The compromise of certificate private keys is not uncommon. In 2011, the Electronic Frontier Foundation found 73,345 cases where certificates were revoked because their private keys had been compromised. In addition, the Heartbleed flaw discovered in OpenSSL last year allowed attackers to extract sensitive data from HTTPS servers, including SSL private keys.

Security blunders or compromises at certificate authorities can also result in fraudulent certificates being issued. In 2011, hackers issued nine fraudulent SSL certificates for domain names owned by Google, Yahoo, Skype, Mozilla and Microsoft after compromising a Comodo-affiliated certificate registration authority.


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