Have digital certificates become too unwieldy to be
trusted?
Such certificates are fundamental to the SSL security model
employed on the Web and ensure that users have a secure, encrypted
connection directly to the website they're visiting. But if
attackers hack into certificate authorities and issue false
certificates for legitimate websites, all bets are off, not least
when it comes to eavesdropping.
Beginning in July, for example, fraudulently obtained digital
certificates--issued by Dutch certificate authority DigiNotar--were
used to launch man-in-the-middle attacks against Gmail users.
Successful exploits would have resulted in attackers being able to
read targeted people's email.
"This attack illustrates one of the many security problems with
SSL: there are too many single points of trust," said Bruce
Schneier, chief security technology officer of BT, in a blog post.
In other words, subvert any of those points of trust and security
fails.
In the case of DigiNotar, the Dutch certificate authority (CA)
didn't discover--never mind own up to--its security breaches until
their scale had reached quite large proportions. Then again,
according to preliminary results of an audit into the breach
commissioned by the Dutch government, DigiNotar practiced poor
information security, including no centralized logging, no
centralization of critical components, out-of-date and unpatched
software, and an administrator password that could have been easily
compromised via a brute-force attack, said Chester Wisniewski, a
senior security advisor at Sophos Canada, in a blog post.
Furthermore, "all of the certificate servers belonged to one
Windows domain, allowing the compromise of one administrator
account to control everything," he said.
Based on those revelations, the Dutch government seized control of
DigiNotar, which is owned by Chicago-based Vasco. Dutch prosecutors
said they were evaluating whether to pursue DigiNotar officials for
criminal negligence.
Interestingly, the damaging exploit--at least in the time required
by businesses such as Google, Microsoft, and Mozilla to code
patches--resulted from the exploitation of a certificate authority
that saw revenues of less than 100,000 British pounds (USD 141,000)
for the first six months of 2011, according to a statement released
last week by Vasco. That statement also promised that DigiNotar
"expects to have a solution for its entire customer base before the
end of this business week" and that it "expects that the cost of
this action will be minimal."
In a subsequent, undated damage control letter to investors,
however, Vasco changed its tone, saying that while the company had
acquired DigiNotar in January 2011, and planned to fully integrate
the DigiNotar's products into its own by 2012, Vasco's own products
remained "100 percent DigiNotar-free."
In other words, DigiNotar appears to be doomed. On Friday, Mozilla
released an unprecedented statement saying that it was permanently
blocking every DigiNotar certificate, forever. "In an incident
earlier this year we worked with Comodo to block a set of
mis-issued certificates that were detected, contained, and reported
to us immediately," said Jonathan Nightingale, director of Firefox
engineering in a blog post. "In DigiNotar's case, by contrast, we
have no confidence that the problem had been contained.
Furthermore, their failure to notify leaves us deeply concerned
about our ability to protect our users from future breaches."
Google and Microsoft have likewise begun permanently blocking
DigiNotar's certificates.
DigiNotar was punished because it failed to come clean quickly.
"The integrity of the SSL system cannot be maintained in secrecy,"
said Nightingale. "Incidents like this one demonstrate the need for
active, immediate, and comprehensive communication between CAs and
software vendors to keep our collective users safe online."
But the exploit of DigiNotar shows how easy it is to subvert SSL,
as well as the serious repercussions that can result even when
clear lines of communication exist. Might that lead to reform--or
possibly regulation--of certificate authorities? "Now that someone
(presumably from Iran) has obtained a legit HTTPS cert for CIA.gov,
I wonder if the US gov will pay attention to this mess," said
Christopher Soghoian, a graduate fellow at the Center for Applied
Cybersecurity Research at Indiana University, via Twitter on
Saturday.
On Monday, Roel Schouwenberg, a senior antivirus researcher at
Kaspersky Lab, said in a blog post that the DigiNotar hack would
have a political impact equal to Stuxnet, and "put cyberwar on or
near the top of the political agenda of Western governments."
Furthermore, he suggested that DigiNotar wasn't an isolated event.
"With some 500 authorities out there globally it's hard to believe
DigiNotar is the only compromised CA out there."
Schouwenberg's prediction was prescient. On Tuesday, an attacker
claimed credit for the DigiNotar attacks, using the same
"Comodohacker" Pastebin account that had been used to claim credit
for the exploit of the Comodo certificate authority earlier this
year.
While the DigiNotar exploit was discovered, Comodohacker claims to
control more certificate authorities. "I have access to 4 more so
HIGH profile CAs, which I can issue certs from them too which I
will, I won't name them," according to the Pastebin post.
Comodohacker also claimed to have accessed the StartCom certificate
authority, but was blocked by a hardware security module.
Furthermore, the attacker claimed to have current access to
GlobalSign, and promised to demonstrate that soon.
Unfortunately, no quick fix appears to exist for SSL. "This
incident demonstrates in a real way the fragility of the SSL/TLS
certificate trust model in use on the net today," said Wisniewski
at Sophos. "I hope adoption of replacement technologies like Moxie
Marlinspike's Convergence take off in a meaningful way to provide
us with more confidence in the security of our communications."
Convergence is a proposal from Marlinspike that involves
crowdsourcing certificate verification, by comparing the
certificates that users around the world receive for a given
website, to help ascertain whether they're legitimate or not. But
the approach is relatively new, and so far only available as a
Firefox plug-in. Arguably, it's also just one step toward what will
need to be a major reform of the information security and business
practices of certificate authorities.
Source:
InformationWeek USA