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Security Analysis of Apple’s “Find My…” Protocol

Interesting research: “Who Can Find My Devices? Security and Privacy of Apple’s Crowd-Sourced Bluetooth Location Tracking System“:

Abstract: Overnight, Apple has turned its hundreds-of-million-device ecosystem into the world’s largest crowd-sourced location tracking network called offline finding (OF). OF leverages online finder devices to detect the presence of missing offline devices using Bluetooth and report an approximate location back to the owner via the Internet. While OF is not the first system of its kind, it is the first to commit to strong privacy goals. In particular, OF aims to ensure finder anonymity, untrackability of owner devices, and confidentiality of location reports. This paper presents the first comprehensive security and privacy analysis of OF. To this end, we recover the specifications of the closed-source OF protocols by means of reverse engineering. We experimentally show that unauthorized access to the location reports allows for accurate device tracking and retrieving a user’s top locations with an error in the order of 10 meters in urban areas. While we find that OF’s design achieves its privacy goals, we discover two distinct design and implementation flaws that can lead to a location correlation attack and unauthorized access to the location history of the past seven days, which could deanonymize users. Apple has partially addressed the issues following our responsible disclosure. Finally, we make our research artifacts publicly available.

There is also code available on GitHub, which allows arbitrary Bluetooth devices to be tracked via Apple’s Find My network.

Posted on March 15, 2021 at 6:16 AMView Comments

Friday Squid Blogging: On SQUIDS

A good tutorial:

But we can go beyond the polarization of electrons and really leverage the electron waviness. By interleaving thin layers of superconducting and normal materials, we can make the quantum electronic equivalents of transistors and diodes such as Superconducting Tunnel Junctions (SJTs) and Superconducting Quantum Interference Devices (affectionately known as SQUIDs). These devices take full advantage of the wave-like nature of electrons and can be used as building blocks for all sorts of novel electronics.

Because of the superconducting requirement, they need to be kept very cold, but quantum electronics have already revolutionized precision measurement. The most visible application has been in measuring the Cosmic Microwave Background (CMB). Observations of the CMB have shown that we live in an expanding Universe, determined the age of our Universe, and identified the fraction of it composed of dark matter and dark energy. Measurements of the CMB have transformed our understanding of the Universe we live in. These measurements have been largely enabled by SQUIDs and related superconducting electronics in their microwave cameras.

As usual, you can also use this squid post to talk about the security stories in the news that I haven’t covered.

Read my blog posting guidelines here.

Posted on March 12, 2021 at 4:10 PMView Comments

More on the Chinese Zero-Day Microsoft Exchange Hack

Nick Weaver has an excellent post on the Microsoft Exchange hack:

The investigative journalist Brian Krebs has produced a handy timeline of events and a few things stand out from the chronology. The attacker was first detected by one group on Jan. 5 and another on Jan. 6, and Microsoft acknowledged the problem immediately. During this time the attacker appeared to be relatively subtle, exploiting particular targets (although we generally lack insight into who was targeted). Microsoft determined on Feb. 18 that it would patch these vulnerabilities on the March 9th “Patch Tuesday” release of fixes.

Somehow, the threat actor either knew that the exploits would soon become worthless or simply guessed that they would. So, in late February, the attacker changed strategy. Instead of simply exploiting targeted Exchange servers, the attackers stepped up their pace considerably by targeting tens of thousands of servers to install the web shell, an exploit that allows attackers to have remote access to a system. Microsoft then released the patch with very little warning on Mar. 2, at which point the attacker simply sought to compromise almost every vulnerable Exchange server on the Internet. The result? Virtually every vulnerable mail server received the web shell as a backdoor for further exploitation, making the patch effectively useless against the Chinese attackers; almost all of the vulnerable systems were exploited before they were patched.

This is a rational strategy for any actor who doesn’t care about consequences. When a zero-day is confidential and undiscovered, the attacker tries to be careful, only using it on attackers of sufficient value. But if the attacker knows or has reason to believe their vulnerabilities may be patched, they will increase the pace of exploits and, once a patch is released, there is no reason to not try to exploit everything possible.

We know that Microsoft shares advance information about updates with some organizations. I have long believed that they give the NSA a few weeks’ notice to do basically what the Chinese did: use the exploit widely, because you don’t have to worry about losing the capability.

Estimates on the number of affected networks continues to rise. At least 30,000 in the US, and 100,000 worldwide. More?

And the vulnerabilities:

The Chinese actors were not using a single vulnerability but actually a sequence of four “zero-day” exploits. The first allowed an unauthorized user to basically tell the server “let me in, I’m the server” by tricking the server into contacting itself. After the unauthorized user gained entry, the hacker could use the second vulnerability, which used a malformed voicemail that, when interpreted by the server, allowed them to execute arbitrary commands. Two further vulnerabilities allow the attacker to write new files, which is a common primitive that attackers use to increase their access: An attacker uses a vulnerability to write a file and then uses the arbitrary command execution vulnerability to execute that file.

Using this access, the attackers could read anybody’s email or indeed take over the mail server completely. Critically, they would almost always do more, introducing a “web shell,” a program that would enable further remote exploitation even if the vulnerabilities are patched.

The details of that web shell matter. If it was sophisticated, it implies that the Chinese hackers were planning on installing it from the beginning of the operation. If it’s kind of slapdash, it implies a last-minute addition when they realized their exploit window was closing.

Now comes the criminal attacks. Any unpatched network is still vulnerable, and we know from history that lots of networks will remain vulnerable for a long time. Expect the ransomware gangs to weaponize this attack within days.

EDITED TO ADD (3/12): Right on schedule, criminal hacker groups are exploiting the vulnerabilities.

EDITED TO ADD (3/13): And now the ransomware.

Posted on March 10, 2021 at 6:28 AMView Comments

On Not Fixing Old Vulnerabilities

How is this even possible?

…26% of companies Positive Technologies tested were vulnerable to WannaCry, which was a threat years ago, and some even vulnerable to Heartbleed. “The most frequent vulnerabilities detected during automated assessment date back to 2013-­2017, which indicates a lack of recent software updates,” the reported stated.

26%!? One in four networks?

Even if we assume that the report is self-serving to the company that wrote it, and that the statistic is not generally representative, this is still a disaster. The number should be 0%.

WannaCry was a 2017 cyberattack, based on a NSA-discovered and Russia-stolen-and-published Windows vulnerability. It primarily affects older, no-longer-supported products like Windows 7. If we can’t keep our systems secure from these vulnerabilities, how are we ever going to secure them from new threats?

Posted on March 9, 2021 at 6:16 AMView Comments

Hacking Digitally Signed PDF Files

Interesting paper: “Shadow Attacks: Hiding and Replacing Content in Signed PDFs“:

Abstract: Digitally signed PDFs are used in contracts and invoices to guarantee the authenticity and integrity of their content. A user opening a signed PDF expects to see a warning in case of any modification. In 2019, Mladenov et al. revealed various parsing vulnerabilities in PDF viewer implementations.They showed attacks that could modify PDF documents without invalidating the signature. As a consequence, affected vendors of PDF viewers implemented countermeasures preventing all attacks.

This paper introduces a novel class of attacks, which we call shadow attacks. The shadow attacks circumvent all existing countermeasures and break the integrity protection of digitally signed PDFs. Compared to previous attacks, the shadow attacks do not abuse implementation issues in a PDF viewer. In contrast, shadow attacks use the enormous flexibility provided by the PDF specification so that shadow documents remain standard-compliant. Since shadow attacks abuse only legitimate features,they are hard to mitigate.

Our results reveal that 16 (including Adobe Acrobat and Foxit Reader) of the 29 PDF viewers tested were vulnerable to shadow attacks. We introduce our tool PDF-Attacker which can automatically generate shadow attacks. In addition, we implemented PDF-Detector to prevent shadow documents from being signed or forensically detect exploits after being applied to signed PDFs.

EDITED TO ADD (3/12): This was written about last summer.

Posted on March 8, 2021 at 6:10 AMView Comments

No, RSA Is Not Broken

I have been seeing this paper by cryptographer Peter Schnorr making the rounds: “Fast Factoring Integers by SVP Algorithms.” It describes a new factoring method, and its abstract ends with the provocative sentence: “This destroys the RSA cryptosystem.”

It does not. At best, it’s an improvement in factoring — and I’m not sure it’s even that. The paper is a preprint: it hasn’t been peer reviewed. Be careful taking its claims at face value.

Some discussion here.

I’ll append more analysis links to this post when I find them.

EDITED TO ADD (3/12): The latest version of the paper does not have the words “This destroys the RSA cryptosystem” in the abstract. Some more discussion.

Posted on March 5, 2021 at 10:48 AMView Comments

Sidebar photo of Bruce Schneier by Joe MacInnis.