SSL and internet security news

Monthly Archive: January 2019

Evaluating the GCHQ Exceptional Access Proposal

The so-called Crypto Wars have been going on for 25 years now. Basically, the FBI — and some of their peer agencies in the UK, Australia, and elsewhere — argue that the pervasive use of civilian encryption is hampering their ability to solve crimes and that they need the tech companies to make their systems susceptible to government eavesdropping. Sometimes their complaint is about communications systems, like voice or messaging apps. Sometimes it’s about end-user devices. On the other side of this debate is pretty much all technologists working in computer security and cryptography, who argue that adding eavesdropping features fundamentally makes those systems less secure.

A recent entry in this debate is a proposal by Ian Levy and Crispin Robinson, both from the UK’s GCHQ (the British signals-intelligence agency — basically, its NSA). It’s actually a positive contribution to the discourse around backdoors; most of the time government officials broadly demand that the tech companies figure out a way to meet their requirements, without providing any details. Levy and Robinson write:

In a world of encrypted services, a potential solution could be to go back a few decades. It’s relatively easy for a service provider to silently add a law enforcement participant to a group chat or call. The service provider usually controls the identity system and so really decides who’s who and which devices are involved — they’re usually involved in introducing the parties to a chat or call. You end up with everything still being end-to-end encrypted, but there’s an extra ‘end’ on this particular communication. This sort of solution seems to be no more intrusive than the virtual crocodile clips that our democratically elected representatives and judiciary authorise today in traditional voice intercept solutions and certainly doesn’t give any government power they shouldn’t have.

On the surface, this isn’t a big ask. It doesn’t affect the encryption that protects the communications. It only affects the authentication that assures people of whom they are talking to. But it’s no less dangerous a backdoor than any others that have been proposed: It exploits a security vulnerability rather than fixing it, and it opens all users of the system to exploitation of that same vulnerability by others.

In a blog post, cryptographer Matthew Green summarized the technical problems with this GCHQ proposal. Basically, making this backdoor work requires not only changing the cloud computers that oversee communications, but it also means changing the client program on everyone’s phone and computer. And that change makes all of those systems less secure. Levy and Robinson make a big deal of the fact that their backdoor would only be targeted against specific individuals and their communications, but it’s still a general backdoor that could be used against anybody.

The basic problem is that a backdoor is a technical capability — a vulnerability — that is available to anyone who knows about it and has access to it. Surrounding that vulnerability is a procedural system that tries to limit access to that capability. Computers, especially internet-connected computers, are inherently hackable, limiting the effectiveness of any procedures. The best defense is to not have the vulnerability at all.

That old physical eavesdropping system Levy and Robinson allude to also exploits a security vulnerability. Because telephone conversations were unencrypted as they passed through the physical wires of the phone system, the police were able to go to a switch in a phone company facility or a junction box on the street and manually attach alligator clips to a specific pair and listen in to what that phone transmitted and received. It was a vulnerability that anyone could exploit — not just the police — but was mitigated by the fact that the phone company was a monolithic monopoly, and physical access to the wires was either difficult (inside a phone company building) or obvious (on the street at a junction box).

The functional equivalent of physical eavesdropping for modern computer phone switches is a requirement of a 1994 U.S. law called CALEA — and similar laws in other countries. By law, telephone companies must engineer phone switches that the government can eavesdrop, mirroring that old physical system with computers. It is not the same thing, though. It doesn’t have those same physical limitations that make it more secure. It can be administered remotely. And it’s implemented by a computer, which makes it vulnerable to the same hacking that every other computer is vulnerable to.

This isn’t a theoretical problem; these systems have been subverted. The most public incident dates from 2004 in Greece. Vodafone Greece had phone switches with the eavesdropping feature mandated by CALEA. It was turned off by default in the Greek phone system, but the NSA managed to surreptitiously turn it on and use it to eavesdrop on the Greek prime minister and over 100 other high-ranking dignitaries.

There’s nothing distinct about a phone switch that makes it any different from other modern encrypted voice or chat systems; any remotely administered backdoor system will be just as vulnerable. Imagine a chat program added this GCHQ backdoor. It would have to add a feature that added additional parties to a chat from somewhere in the system — and not by the people at the endpoints. It would have to suppress any messages alerting users to another party being added to that chat. Since some chat programs, like iMessage and Signal, automatically send such messages, it would force those systems to lie to their users. Other systems would simply never implement the “tell me who is in this chat conversation” feature­which amounts to the same thing.

And once that’s in place, every government will try to hack it for its own purposes­ — just as the NSA hacked Vodafone Greece. Again, this is nothing new. In 2010, China successfully hacked the back-door mechanism Google put in place to meet law-enforcement requests. In 2015, someone — we don’t know who — hacked an NSA backdoor in a random-number generator used to create encryption keys, changing the parameters so they could also eavesdrop on the communications. There are certainly other stories that haven’t been made public.

Simply adding the feature erodes public trust. If you were a dissident in a totalitarian country trying to communicate securely, would you want to use a voice or messaging system that is known to have this sort of backdoor? Who would you bet on, especially when the cost of losing the bet might be imprisonment or worse: the company that runs the system, or your country’s government intelligence agency? If you were a senior government official, or the head of a large multinational corporation, or the security manager or a critical technician at a power plant, would you want to use this system?

Of course not.

Two years ago, there was a rumor of a WhatsApp backdoor. The details are complicated, and calling it a backdoor or a vulnerability is largely inaccurate — but the resultant confusion caused some people to abandon the encrypted messaging service.

Trust is fragile, and transparency is essential to trust. And while Levy and Robinson state that “any exceptional access solution should not fundamentally change the trust relationship between a service provider and its users,” this proposal does exactly that. Communications companies could no longer be honest about what their systems were doing, and we would have no reason to trust them if they tried.

In the end, all of these exceptional access mechanisms, whether they exploit existing vulnerabilities that should be closed or force vendors to open new ones, reduce the security of the underlying system. They reduce our reliance on security technologies we know how to do well — cryptography — to computer security technologies we are much less good at. Even worse, they replace technical security measures with organizational procedures. Whether it’s a database of master keys that could decrypt an iPhone or a communications switch that orchestrates who is securely chatting with whom, it is vulnerable to attack. And it will be attacked.

The foregoing discussion is a specific example of a broader discussion that we need to have, and it’s about the attack/defense balance. Which should we prioritize? Should we design our systems to be open to attack, in which case they can be exploited by law enforcement — and others? Or should we design our systems to be as secure as possible, which means they will be better protected from hackers, criminals, foreign governments and — unavoidably — law enforcement as well?

This discussion is larger than the FBI’s ability to solve crimes or the NSA’s ability to spy. We know that foreign intelligence services are targeting the communications of our elected officials, our power infrastructure, and our voting systems. Do we really want some foreign country penetrating our lawful-access backdoor in the same way the NSA penetrated Greece’s?

I have long maintained that we need to adopt a defense-dominant strategy: We should prioritize our need for security over our need for surveillance. This is especially true in the new world of physically capable computers. Yes, it will mean that law enforcement will have a harder time eavesdropping on communications and unlocking computing devices. But law enforcement has other forensic techniques to collect surveillance data in our highly networked world. We’d be much better off increasing law enforcement’s technical ability to investigate crimes in the modern digital world than we would be to weaken security for everyone. The ability to surreptitiously add ghost users to a conversation is a vulnerability, and it’s one that we would be better served by closing than exploiting.

This essay originally appeared on Lawfare.com.

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Prices for Zero-Day Exploits Are Rising

Companies are willing to pay ever-increasing amounts for good zero-day exploits against hard-to-break computers and applications:

On Monday, market-leading exploit broker Zerodium said it would pay up to $2 million for zero-click jailbreaks of Apple’s iOS, $1.5 million for one-click iOS jailbreaks, and $1 million for exploits that take over secure messaging apps WhatsApp and iMessage. Previously, Zerodium was offering $1.5 million, $1 million, and $500,000 for the same types of exploits respectively. The steeper prices indicate not only that the demand for these exploits continues to grow, but also that reliably compromising these targets is becoming increasingly hard.

Note that these prices are for offensive uses of the exploit. Zerodium — and others — sell exploits to companies who make surveillance tools and cyber-weapons for governments. Many companies have bug bounty programs for those who want the exploit used for defensive purposes — i.e., fixed — but they pay orders of magnitude less. This is a problem.

Back in 2014, Dan Geer said that that the US should corner the market on software vulnerabilities:

“There is no doubt that the U.S. Government could openly corner the world vulnerability market,” said Geer, “that is, we buy them all and we make them all public. Simply announce ‘Show us a competing bid, and we’ll give you [10 times more].’ Sure, there are some who will say ‘I hate Americans; I sell only to Ukrainians,’ but because vulnerability finding is increasingly automation-assisted, the seller who won’t sell to the Americans knows that his vulns can be rediscovered in due course by someone who will sell to the Americans who will tell everybody, thus his need to sell his product before it outdates is irresistible.”

I don’t know about the 10x, but in theory he’s right. There’s no other way to solve this.

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El Chapo’s Encryption Defeated by Turning His IT Consultant

Impressive police work:

In a daring move that placed his life in danger, the I.T. consultant eventually gave the F.B.I. his system’s secret encryption keys in 2011 after he had moved the network’s servers from Canada to the Netherlands during what he told the cartel’s leaders was a routine upgrade.

A Dutch article says that it’s a BlackBerry system.

El Chapo had his IT person install “…spyware called FlexiSPY on the ‘special phones’ he had given to his wife, Emma Coronel Aispuro, as well as to two of his lovers, including one who was a former Mexican lawmaker.” That same software was used by the FBI when his IT person turned over the keys. Yet again we learn the lesson that a backdoor can be used against you.

And it doesn’t have to be with the IT person’s permission. A good intelligence agency can use the IT person’s authorizations without his knowledge or consent. This is why the NSA hunts sysadmins.

Slashdot thread. Hacker News thread. Boing Boing post.

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Alex Stamos on Content Moderation and Security

Former Facebook CISO Alex Stamos argues that increasing political pressure on social media platforms to moderate content will give them a pretext to turn all end-to-end crypto off — which would be more profitable for them and bad for society.

If we ask tech companies to fix ancient societal ills that are now reflected online with moderation, then we will end up with huge, democratically-unaccountable organizations controlling our lives in ways we never intended. And those ills will still exist below the surface.

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Using a Fake Hand to Defeat Hand-Vein Biometrics

Nice work:

One attraction of a vein based system over, say, a more traditional fingerprint system is that it may be typically harder for an attacker to learn how a user’s veins are positioned under their skin, rather than lifting a fingerprint from a held object or high quality photograph, for example.

But with that said, Krissler and Albrecht first took photos of their vein patterns. They used a converted SLR camera with the infrared filter removed; this allowed them to see the pattern of the veins under the skin.

“It’s enough to take photos from a distance of five meters, and it might work to go to a press conference and take photos of them,” Krissler explained. In all, the pair took over 2,500 pictures to over 30 days to perfect the process and find an image that worked.

They then used that image to make a wax model of their hands which included the vein detail.

Slashdot thread.

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Security Vulnerabilities in Cell Phone Systems

Good essay on the inherent vulnerabilities in the cell phone standards and the market barriers to fixing them.

So far, industry and policymakers have largely dragged their feet when it comes to blocking cell-site simulators and SS7 attacks. Senator Ron Wyden, one of the few lawmakers vocal about this issue, sent a letter in August encouraging the Department of Justice to “be forthright with federal courts about the disruptive nature of cell-site simulators.” No response has ever been published.

The lack of action could be because it is a big task — there are hundreds of companies and international bodies involved in the cellular network. The other reason could be that intelligence and law enforcement agencies have a vested interest in exploiting these same vulnerabilities. But law enforcement has other effective tools that are unavailable to criminals and spies. For example, the police can work directly with phone companies, serving warrants and Title III wiretap orders. In the end, eliminating these vulnerabilities is just as valuable for law enforcement as it is for everyone else.

As it stands, there is no government agency that has the power, funding and mission to fix the problems. Large companies such as AT&T, Verizon, Google and Apple have not been public about their efforts, if any exist.

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Machine Learning to Detect Software Vulnerabilities

No one doubts that artificial intelligence (AI) and machine learning (ML) will transform cybersecurity. We just don’t know how, or when. While the literature generally focuses on the different uses of AI by attackers and defenders ­ and the resultant arms race between the two ­ I want to talk about software vulnerabilities.

All software contains bugs. The reason is basically economic: The market doesn’t want to pay for quality software. With a few exceptions, such as the space shuttle, the market prioritizes fast and cheap over good. The result is that any large modern software package contains hundreds or thousands of bugs.

Some percentage of bugs are also vulnerabilities, and a percentage of those are exploitable vulnerabilities, meaning an attacker who knows about them can attack the underlying system in some way. And some percentage of those are discovered and used. This is why your computer and smartphone software is constantly being patched; software vendors are fixing bugs that are also vulnerabilities that have been discovered and are being used.

Everything would be better if software vendors found and fixed all bugs during the design and development process, but, as I said, the market doesn’t reward that kind of delay and expense. AI, and machine learning in particular, has the potential to forever change this trade-off.

The problem of finding software vulnerabilities seems well-suited for ML systems. Going through code line by line is just the sort of tedious problem that computers excel at, if we can only teach them what a vulnerability looks like. There are challenges with that, of course, but there is already a healthy amount of academic literature on the topic — and research is continuing. There’s every reason to expect ML systems to get better at this as time goes on, and some reason to expect them to eventually become very good at it.

Finding vulnerabilities can benefit both attackers and defenders, but it’s not a fair fight. When an attacker’s ML system finds a vulnerability in software, the attacker can use it to compromise systems. When a defender’s ML system finds the same vulnerability, he or she can try to patch the system or program network defenses to watch for and block code that tries to exploit it.

But when the same system is in the hands of a software developer who uses it to find the vulnerability before the software is ever released, the developer fixes it so it can never be used in the first place. The ML system will probably be part of his or her software design tools and will automatically find and fix vulnerabilities while the code is still in development.

Fast-forward a decade or so into the future. We might say to each other, “Remember those years when software vulnerabilities were a thing, before ML vulnerability finders were built into every compiler and fixed them before the software was ever released? Wow, those were crazy years.” Not only is this future possible, but I would bet on it.

Getting from here to there will be a dangerous ride, though. Those vulnerability finders will first be unleashed on existing software, giving attackers hundreds if not thousands of vulnerabilities to exploit in real-world attacks. Sure, defenders can use the same systems, but many of today’s Internet of Things systems have no engineering teams to write patches and no ability to download and install patches. The result will be hundreds of vulnerabilities that attackers can find and use.

But if we look far enough into the horizon, we can see a future where software vulnerabilities are a thing of the past. Then we’ll just have to worry about whatever new and more advanced attack techniques those AI systems come up with.

This essay previously appeared on SecurityIntelligence.com.

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New Attack Against Electrum Bitcoin Wallets

This is clever:

How the attack works:

  • Attacker added tens of malicious servers to the Electrum wallet network.
  • Users of legitimate Electrum wallets initiate a Bitcoin transaction.
  • If the transaction reaches one of the malicious servers, these servers reply with an error message that urges users to download a wallet app update from a malicious website (GitHub repo).
  • User clicks the link and downloads the malicious update.
  • When the user opens the malicious Electrum wallet, the app asks the user for a two-factor authentication (2FA) code. This is a red flag, as these 2FA codes are only requested before sending funds, and not at wallet startup.
  • The malicious Electrum wallet uses the 2FA code to steal the user’s funds and transfer them to the attacker’s Bitcoin addresses.

The problem here is that Electrum servers are allowed to trigger popups with custom text inside users’ wallets.

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