Entries Tagged "SSL"

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DROWN Attack

Earlier this week, we learned of yet another attack against SSL/TLS where an attacker can force people to use insecure algorithms. It’s called DROWN. Here’s a good news article on the attack, the technical paper describing the attack, and a very good technical blog post by Matthew Green.

As an aside, I am getting pretty annoyed at all the marketing surrounding vulnerabilities these days. Vulnerabilities do not need a catchy name, a dedicated website — even thought it’s a very good website — and a logo.

Posted on March 3, 2016 at 2:09 PMView Comments

FREAK: Security Rollback Attack Against SSL

This week, we learned about an attack called “FREAK” — “Factoring Attack on RSA-EXPORT Keys” — that can break the encryption of many websites. Basically, some sites’ implementations of secure sockets layer technology, or SSL, contain both strong encryption algorithms and weak encryption algorithms. Connections are supposed to use the strong algorithms, but in many cases an attacker can force the website to use the weaker encryption algorithms and then decrypt the traffic. From Ars Technica:

In recent days, a scan of more than 14 million websites that support the secure sockets layer or transport layer security protocols found that more than 36 percent of them were vulnerable to the decryption attacks. The exploit takes about seven hours to carry out and costs as little as $100 per site.

This is a general class of attack I call “security rollback” attacks. Basically, the attacker forces the system users to revert to a less secure version of their protocol. Think about the last time you used your credit card. The verification procedure involved the retailer’s computer connecting with the credit card company. What if you snuck around to the back of the building and severed the retailer’s phone lines? Most likely, the retailer would have still accepted your card, but defaulted to making a manual impression of it and maybe looking at your signature. The result: you’ll have a much easier time using a stolen card.

In this case, the security flaw was designed in deliberately. Matthew Green writes:

Back in the early 1990s when SSL was first invented at Netscape Corporation, the United States maintained a rigorous regime of export controls for encryption systems. In order to distribute crypto outside of the U.S., companies were required to deliberately “weaken” the strength of encryption keys. For RSA encryption, this implied a maximum allowed key length of 512 bits.

The 512-bit export grade encryption was a compromise between dumb and dumber. In theory it was designed to ensure that the NSA would have the ability to “access” communications, while allegedly providing crypto that was still “good enough” for commercial use. Or if you prefer modern terms, think of it as the original “golden master key.”

The need to support export-grade ciphers led to some technical challenges. Since U.S. servers needed to support both strong and weak crypto, the SSL designers used a “cipher suite” negotiation mechanism to identify the best cipher both parties could support. In theory this would allow “strong” clients to negotiate “strong” ciphersuites with servers that supported them, while still providing compatibility to the broken foreign clients.

And that’s the problem. The weak algorithms are still there, and can be exploited by attackers.

Fixes are coming. Companies like Apple are quickly rolling out patches. But the vulnerability has been around for over a decade, and almost has certainly used by national intelligence agencies and criminals alike.

This is the generic problem with government-mandated backdoors, key escrow, “golden keys,” or whatever you want to call them. We don’t know how to design a third-party access system that checks for morality; once we build in such access, we then have to ensure that only the good guys can do it. And we can’t. Or, to quote the Economist: “…mathematics applies to just and unjust alike; a flaw that can be exploited by Western governments is vulnerable to anyone who finds it.”

This essay previously appeared on the Lawfare blog.

EDITED TO ADD: Microsoft Windows is vulnerable.

Posted on March 6, 2015 at 10:46 AMView Comments

A New Free CA

Announcing Let’s Encrypt, a new free certificate authority. This is a joint project of EFF, Mozilla, Cisco, Akamai, and the University of Michigan.

This is an absolutely fantastic idea.

The anchor for any TLS-protected communication is a public-key certificate which demonstrates that the server you’re actually talking to is the server you intended to talk to. For many server operators, getting even a basic server certificate is just too much of a hassle. The application process can be confusing. It usually costs money. It’s tricky to install correctly. It’s a pain to update.

Let’s Encrypt is a new free certificate authority, built on a foundation of cooperation and openness, that lets everyone be up and running with basic server certificates for their domains through a simple one-click process.


The key principles behind Let’s Encrypt are:

  • Free: Anyone who owns a domain can get a certificate validated for that domain at zero cost.
  • Automatic: The entire enrollment process for certificates occurs painlessly during the server’s native installation or configuration process, while renewal occurs automatically in the background.
  • Secure: Let’s Encrypt will serve as a platform for implementing modern security techniques and best practices.
  • Transparent: All records of certificate issuance and revocation will be available to anyone who wishes to inspect them.
  • Open: The automated issuance and renewal protocol will be an open standard and as much of the software as possible will be open source.
  • Cooperative: Much like the underlying Internet protocols themselves, Let’s Encrypt is a joint effort to benefit the entire community, beyond the control of any one organization.

Slashdot thread. Hacker News thread.

EDITED TO ADD (11/19): Good post. And EFF’s blog post.

Posted on November 18, 2014 at 12:38 PMView Comments

The Human Side of Heartbleed

The announcement on April 7 was alarming. A new Internet vulnerability called Heartbleed could allow hackers to steal your logins and passwords. It affected a piece of security software that is used on half a million websites worldwide. Fixing it would be hard: It would strain our security infrastructure and the patience of users everywhere.

It was a software insecurity, but the problem was entirely human.

Software has vulnerabilities because it’s written by people, and people make mistakes — thousands of mistakes. This particular mistake was made in 2011 by a German graduate student who was one of the unpaid volunteers working on a piece of software called OpenSSL. The update was approved by a British consultant.

In retrospect, the mistake should have been obvious, and it’s amazing that no one caught it. But even though thousands of large companies around the world used this critical piece of software for free, no one took the time to review the code after its release.

The mistake was discovered around March 21, 2014, and was reported on April 1 by Neel Mehta of Google’s security team, who quickly realized how potentially devastating it was. Two days later, in an odd coincidence, researchers at a security company called Codenomicon independently discovered it.

When a researcher discovers a major vulnerability in a widely used piece of software, he generally discloses it responsibly. Why? As soon as a vulnerability becomes public, criminals will start using it to hack systems, steal identities, and generally create mayhem, so we have to work together to fix the vulnerability quickly after it’s announced.

The researchers alerted some of the larger companies quietly so that they could fix their systems before the public announcement. (Who to tell early is another very human problem: If you tell too few, you’re not really helping, but if you tell too many, the secret could get out.) Then Codenomicon announced the vulnerability.

One of the biggest problems we face in the security community is how to communicate these sorts of vulnerabilities. The story is technical, and people often don’t know how to react to the risk. In this case, the Codenomicon researchers did well. They created a public website explaining (in simple terms) the vulnerability and how to fix it, and they created a logo — a red bleeding heart — that every news outlet used for coverage of the story.

The first week of coverage varied widely, as some people panicked and others downplayed the threat. This wasn’t surprising: There was a lot of uncertainty about the risk, and it wasn’t immediately obvious how disastrous the vulnerability actually was.

The major Internet companies were quick to patch vulnerable systems. Individuals were less likely to update their passwords, but by and large, that was OK.

True to form, hackers started exploiting the vulnerability within minutes of the announcement. We assume that governments also exploited the vulnerability while they could. I’m sure the U.S. National Security Agency had advance warning.

By now, it’s largely over. There are still lots of unpatched systems out there. (Many of them are embedded hardware systems that can’t be patched.) The risk of attack is still there, but minimal. In the end, the actual damage was also minimal, although the expense of restoring security was great.

The question that remains is this: What should we expect in the future — are there more Heartbleeds out there?

Yes. Yes there are. The software we use contains thousands of mistakes — many of them security vulnerabilities. Lots of people are looking for these vulnerabilities: Researchers are looking for them. Criminals and hackers are looking for them. National intelligence agencies in the United States, the United Kingdom, China, Russia, and elsewhere are looking for them. The software vendors themselves are looking for them.

What happens when a vulnerability is found depends on who finds it. If the vendor finds it, it quietly fixes it. If a researcher finds it, he or she alerts the vendor and then reports it to the public. If a national intelligence agency finds the vulnerability, it either quietly uses it to spy on others or — if we’re lucky — alerts the vendor. If criminals and hackers find it, they use it until a security company notices and alerts the vendor, and then it gets fixed — usually within a month.

Heartbleed was unique because there was no single fix. The software had to be updated, and then websites had to regenerate their encryption keys and get new public-key certificates. After that, people had to update their passwords. This multi-stage process had to take place publicly, which is why the announcement happened the way it did.

Yes, it’ll happen again. But most of the time, it’ll be easier to deal with than this.

This essay previously appeared on The Mark News.

Posted on June 4, 2014 at 6:23 AMView Comments

Forged SSL Certificates Pervasive on the Internet

About 0.2% of all SSL certificates are forged. This is the first time I’ve ever seen a number based on real data. News article:

Of 3.45 million real-world connections made to Facebook servers using the transport layer security (TLS) or secure sockets layer protocols, 6,845, or about 0.2 percent of them, were established using forged certificates.

Actual paper.

EDITED TO ADD (6/13): I’m mis-characterizing the study. The study really says that 0.2% of HTTPS traffic to Facebook is intercepted and re-signed, and the vast majority of that interception and resigning happens either on the user’s local computer (by way of trusted security software which is acting scanning proxy) or locally on a private network behind a corporation’s intercepting proxy/firewall. Only a small percentage of intercepted traffic is a result of malware or other nefarious activity.

Posted on May 16, 2014 at 6:43 AMView Comments

More on Heartbleed

This is an update to my earlier post.

Cloudflare is reporting that it’s very difficult, if not practically impossible, to steal SSL private keys with this attack.

Here’s the good news: after extensive testing on our software stack, we have been unable to successfully use Heartbleed on a vulnerable server to retrieve any private key data. Note that is not the same as saying it is impossible to use Heartbleed to get private keys. We do not yet feel comfortable saying that. However, if it is possible, it is at a minimum very hard. And, we have reason to believe based on the data structures used by OpenSSL and the modified version of NGINX that we use, that it may in fact be impossible.

The reasoning is complicated, and I suggest people read the post. What I have heard from people who actually ran the attack against a various servers is that what you get is a huge variety of cruft, ranging from indecipherable binary to useless log messages to peoples’ passwords. The variability is huge.

This xkcd comic is a very good explanation of how the vulnerability works. And this post by Dan Kaminsky is worth reading.

I have a lot to say about the human aspects of this: auditing of open-source code, how the responsible disclosure process worked in this case, the ease with which anyone could weaponize this with just a few lines of script, how we explain vulnerabilities to the public — and the role that impressive logo played in the process — and our certificate issuance and revocation process. This may be a massive computer vulnerability, but all of the interesting aspects of it are human.

EDITED TO ADD (4/12): We have one example of someone successfully retrieving an SSL private key using Heartbleed. So it’s possible, but it seems to be much harder than we originally thought.

And we have a story where two anonymous sources have claimed that the NSA has been exploiting Heartbleed for two years.

EDITED TO ADD (4/12): Hijacking user sessions with Heartbleed. And a nice essay on the marketing and communications around the vulnerability

EDITED TO ADD (4/13): The US intelligence community has denied prior knowledge of Heatbleed. The statement is word-game free:

NSA was not aware of the recently identified vulnerability in OpenSSL, the so-called Heartbleed vulnerability, until it was made public in a private sector cybersecurity report. Reports that say otherwise are wrong.

The statement also says:

Unless there is a clear national security or law enforcement need, this process is biased toward responsibly disclosing such vulnerabilities.

Since when is “law enforcement need” included in that decision process? This national security exception to law and process is extending much too far into normal police work.

Another point. According to the original Bloomberg article:


Certainly a plausible statement. But if those millions didn’t discover something obvious like Heartbleed, shouldn’t we investigate them for incompetence?

Finally — not related to the NSA — this is good information on which sites are still vulnerable, including historical data.

Posted on April 11, 2014 at 1:10 PMView Comments


Heartbleed is a catastrophic bug in OpenSSL:

“The Heartbleed bug allows anyone on the Internet to read the memory of the systems protected by the vulnerable versions of the OpenSSL software. This compromises the secret keys used to identify the service providers and to encrypt the traffic, the names and passwords of the users and the actual content. This allows attackers to eavesdrop communications, steal data directly from the services and users and to impersonate services and users.

Basically, an attacker can grab 64K of memory from a server. The attack leaves no trace, and can be done multiple times to grab a different random 64K of memory. This means that anything in memory — SSL private keys, user keys, anything — is vulnerable. And you have to assume that it is all compromised. All of it.

“Catastrophic” is the right word. On the scale of 1 to 10, this is an 11.

Half a million sites are vulnerable, including my own. Test your vulnerability here.

The bug has been patched. After you patch your systems, you have to get a new public/private key pair, update your SSL certificate, and then change every password that could potentially be affected.

At this point, the probability is close to one that every target has had its private keys extracted by multiple intelligence agencies. The real question is whether or not someone deliberately inserted this bug into OpenSSL, and has had two years of unfettered access to everything. My guess is accident, but I have no proof.

This article is worth reading. Hacker News thread is filled with commentary. XKCD cartoon.

EDITED TO ADD (4/9): Has anyone looked at all the low-margin non-upgradable embedded systems that use OpenSSL? An upgrade path that involves the trash, a visit to Best Buy, and a credit card isn’t going to be fun for anyone.

EDITED TO ADD (4/10): I’m hearing that the CAs are completely clogged, trying to reissue so many new certificates. And I’m not sure we have anything close to the infrastructure necessary to revoke half a million certificates.

Possible evidence that Heartbleed was exploited last year.

EDITED TO ADD (4/10): I wonder if there is going to be some backlash from the mainstream press and the public. If nothing really bad happens — if this turns out to be something like the Y2K bug — then we are going to face criticisms of crying wolf.

EDITED TO ADD (4/11): Brian Krebs and Ed Felten on how to protect yourself from Heartbleed.

Posted on April 9, 2014 at 5:03 AMView Comments

A Fraying of the Public/Private Surveillance Partnership

The public/private surveillance partnership between the NSA and corporate data collectors is starting to fray. The reason is sunlight. The publicity resulting from the Snowden documents has made companies think twice before allowing the NSA access to their users’ and customers’ data.

Pre-Snowden, there was no downside to cooperating with the NSA. If the NSA asked you for copies of all your Internet traffic, or to put backdoors into your security software, you could assume that your cooperation would forever remain secret. To be fair, not every corporation cooperated willingly. Some fought in court. But it seems that a lot of them, telcos and backbone providers especially, were happy to give the NSA unfettered access to everything. Post-Snowden, this is changing. Now that many companies’ cooperation has become public, they’re facing a PR backlash from customers and users who are upset that their data is flowing to the NSA. And this is costing those companies business.

How much is unclear. In July, right after the PRISM revelations, the Cloud Security Alliance reported that US cloud companies could lose $35 billion over the next three years, mostly due to losses of foreign sales. Surely that number has increased as outrage over NSA spying continues to build in Europe and elsewhere. There is no similar report for software sales, although I have attended private meetings where several large US software companies complained about the loss of foreign sales. On the hardware side, IBM is losing business in China. The US telecom companies are also suffering: AT&T is losing business worldwide.

This is the new reality. The rules of secrecy are different, and companies have to assume that their responses to NSA data demands will become public. This means there is now a significant cost to cooperating, and a corresponding benefit to fighting.

Over the past few months, more companies have woken up to the fact that the NSA is basically treating them as adversaries, and are responding as such. In mid-October, it became public that the NSA was collecting e-mail address books and buddy lists from Internet users logging into different service providers. Yahoo, which didn’t encrypt those user connections by default, allowed the NSA to collect much more of its data than Google, which did. That same day, Yahoo announced that it would implement SSL encryption by default for all of its users. Two weeks later, when it became public that the NSA was collecting data on Google users by eavesdropping on the company’s trunk connections between its data centers, Google announced that it would encrypt those connections.

We recently learned that Yahoo fought a government order to turn over data. Lavabit fought its order as well. Apple is now tweaking the government. And we think better of those companies because of it.

Now Lavabit, which closed down its e-mail service rather than comply with the NSA’s request for the master keys that would compromise all of its customers, has teamed with Silent Circle to develop a secure e-mail standard that is resistant to these kinds of tactics.

The Snowden documents made it clear how much the NSA relies on corporations to eavesdrop on the Internet. The NSA didn’t build a massive Internet eavesdropping system from scratch. It noticed that the corporate world was already eavesdropping on every Internet user — surveillance is the business model of the Internet, after all — and simply got copies for itself.

Now, that secret ecosystem is breaking down. Supreme Court Justice Louis Brandeis wrote about transparency, saying “Sunlight is said to be the best of disinfectants.” In this case, it seems to be working.

These developments will only help security. Remember that while Edward Snowden has given us a window into the NSA’s activities, these sorts of tactics are probably also used by other intelligence services around the world. And today’s secret NSA programs become tomorrow’s PhD theses, and the next day’s criminal hacker tools. It’s impossible to build an Internet where the good guys can eavesdrop, and the bad guys cannot. We have a choice between an Internet that is vulnerable to all attackers, or an Internet that is safe from all attackers. And a safe and secure Internet is in everyone’s best interests, including the US’s.

This essay previously appeared on TheAtlantic.com.

Posted on November 14, 2013 at 6:21 AMView Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.