TPM

10 Articles

Beating Bitlocker In 43 Seconds

February 6, 2024 by 68 Comments

How long does it take to steal your Bitlocker keys? Try 43 seconds, using less than $10 in hardware. Encrypting your hard drive is good security. If you’re running Windows, the most popular system is BitLocker, which has come with Windows since Vista. We’ve known for some time that Bitlocker could be defeated with direct access to the hardware. Microsoft claims that the process requires an attacker with skill and lengthy access to the hardware. [Stacksmashing] wanted to define lengthy, so he gave it a try. The result is a shockingly fast attack.

Anyone who uses Windows has probably run into Bitlocker. Your hard drive is encrypted, and Bitlocker runs silently in the background, decrypting data on demand.  The problem is key storage. In a simplified sense, encryption keys are stored in the Trusted Platform Module (TPM). When your computer boots, it reads the key from the TPM over the LPC (low pin count) bus, which is one of the last remnants of the original ISA bus.

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This Week In Security: Not A Vulnerability, BGP Bug Propogation, And Press Enter To Hack

September 1, 2023 by 6 Comments

Curl was recently notified of a CVE, CVE-2020-19909, rated at a hair-raising 9.8 on the CVSS scale. And PostgreSQL has CVE-2020-21469, clocking in with a 7.5 severity. You may notice something odd about those two vulnerabilities, but I promise the 2020 date is only the tip of the iceberg here.

Let’s start with PostgreSQL. That vulnerability was only present in version 12.2, which released in February of 2020, and was fixed with the 12.3 release in May of that same year. The problem is a stack buffer overflow, which doesn’t seem to enable code execution, but does cause a denial of service situation. To trigger the bug? Repeatedly send the PostgreSQL daemon the SIGHUP signal.

If you’re familiar with Linux signals, that might sound odd. See, the SIGHUP signal technically indicates the end of a user session, but most daemons use it to indicate a restart or reload request. And to send this signal, a user has to have elevated privileges — elevated enough to simply stop the daemon altogether. Put simply, it’s not a security vulnerability, just a minor bug.

And now on to curl — This one is just bizarre. The issue is a integer overflow in the --retry-delay argument, which specifies in seconds how often curl should retry a failing download. The value is multiplied by 1000 to convert to milliseconds, resulting in an overflow for very large values. The result of that overflow? A smaller value for the retry delay.

[Daniel Stenberg] makes the point that this tale is a wonderful demonstration of the brokenness of the CVE system and NVD’s handling of it. And in this case, it’s hard not to see this as negligence. We have to work really hard to construct a theoretical scenario where this bug could actually be exploited. The best I’ve been able to come up with is an online download tool, where the user can specify part of the target name and a timeout. If that tool had a check to ensure that the timeout was large enough to avoid excess traffic, this bug could bypass that check. Should we be assigning CVEs for that sort of convoluted, theoretical attack?

But here’s the thing, that attack scenario should rate something like a CVSS of 4.8 at absolute worst. NVD assigned this a 9.8. There’s no way you can squint at this bug hard enough to legitimately rank it that severe. At the time of writing, the NVD lists this as “UNDERGOING REANALYSIS”.
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Bypassing Bitlocker With A Logic Analzyer

August 25, 2023 by 27 Comments

Security Engineer [Guillaume Quéré] spends the day penetration testing systems for their employer and has pointed out and successfully exploited a rather obvious weakness in the BitLocker full volume encryption system, which as the linked article says, allows one to simply sniff the traffic between the discrete TPM chip and CPU via an SPI bus. The way Bitlocker works is to use a private key stored in the TPM chip to encrypt the full volume key that in turn was used to encrypt the volume data. This is all done by low-level device drivers in the Windows kernel and is transparent to the user.

TPM chip pins too small? Just find something else on the bus!

The whole point of BitLocker was to prevent access to data on the secured volume in the event of a physical device theft or loss. Simply pulling the drive and dropping it into a non-secured machine or some other adaptor would not provide any data without the key stored by the TPM. However, since that key must pass as plaintext from the TPM to the CPU during the boot sequence, [Guillaume] shows that it is quite straightforward — with very low-cost tools and free software — to simply locate and sniff out this TPM-to-CPU transaction and decode the datastream and locate the key. Using little more than a cheapo logic analyser hooked up to some conveniently large pins on a nearby flash chip (because the SCK, MISO, and MOSI pins are shared with the TPM) the simple TIS was decoded enough to lock onto the bytes of the TPM frame. This could then be decoded with a TPM stream decoder web app, courtesy of the TPM2-software community group. The command to look for is the TPM_CC.Unseal which is the request from the CPU to the TPM to send over that key we’re interested in. After that just grabbing and decoding the TPM response frame will immediately reveal the goods.

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This Week In Security: TPM And BootGuard, Drones, And Coverups

May 12, 2023 by 17 Comments

Full disk encryption is the go-to solution for hardening a laptop against the worst-case scenario of physical access. One way that encryption can be managed is through a Trusted Platform Module (TPM), a chip on the motherboard that manages the disk encryption key, and only hands it over for boot after the user has authenticated. We’ve seen some clever tricks deployed against these discrete TPMs, like sniffing the data going over the physical traces. So in theory, an integrated TPM might be more secure. Such a technique does exist, going by the name fTPM, or firmware TPM. It uses a Trusted Execution Environment, a TEE, to store and run the TPM code. And there’s another clever attack against that concept (PDF).

It’s chip glitching via a voltage fault. This particular attack works against AMD processors, and the voltage fault is triggered by injecting commands into the Serial Voltage Identification Interface 2.0 (SVI2). Dropping the voltage momentarily to the AMD Secure Processor (AMD-SP) can cause a key verification step to succeed even against an untrusted key, bypassing the need for an AMD Root Key (ARK) signed board firmware. That’s not a simple process, and pulling it off takes about $200 of gear, and about 3 hours. This exposes the CPU-unique seed, the board NVRAM, and all the protected TPM objects.

So how bad is this in the real world? If your disk encryption only relies on an fTPM, it’s pretty bad. The attack exposes that key and breaks encryption. For something like BitLocker that can also use a PIN, it’s a bit better, though to really offer more resistance, that needs to be a really long PIN: a 10 digit PIN falls to a GPU in just 4 minutes, in this scenario where it can be attacked offline. There is an obscure way to enable an “enhanced PIN”, a password, which makes that offline attack impractical with a secure password.

And if hardware glitching a computer seems to complicated, why not just use the leaked MSI keys? Now to be fair, this only seems to allow a bypass of Intel’s BootGuard, but it’s still a blow. MSI suffered a ransomware-style breach in March, but rather than encrypt data, the attackers simply threatened to release the copied data to the world. MSI apparently refused to pay up, and source code and signing keys are now floating in the dark corners of the Internet. There have been suggestions that this leak impacts the entire line of Intel processors, but it seems likely that MSI only had their own signing keys to lose. But that’s plenty bad, given the lack of a revocation system or automatic update procedure for MSI firmware. Continue reading “This Week In Security: TPM And BootGuard, Drones, And Coverups” →

The TPM module that Viktor designed, inserted into the motherboard

TPM Module Too Expensive? DIY Your Own Easily!

May 4, 2022 by 83 Comments

Since Windows 11 has announced its TPM module requirement, the prices for previously abundant and underappreciated TPM add-on boards for PC motherboards have skyrocketed. We’ve been getting chips and soldering them onto boards of our own design, instead – and [viktor]’s project is one more example of that. [Viktor] has checked online marketplace listings for a TPM module for his Gigabyte AORUS GAMING 3 motherboard, and found out they started at around 150EUR – which is almost as much as the motherboard itself costs. So, as any self-respecting hacker, he went the DIY way, and it went with hardly a hitch.

Following the schematic from the datasheet, he quickly made a simple KiCad layout, matching it to the pinout from his motherboard’s user manual, then ordered the boards from PCBWay and SLB9665 chips from eBay. After both arrived, [viktor] assembled the boards, and found one small mistake – he designed a module for 2.54mm pin headers, but his motherboard had 2.0mm headers. He wired up a small adapter to make his assembled V1.0 boards work, and Windows 11 installed without any TPM complaints. He shows that he’s designed a new, V1.1 version with an updated connector, too, and published its (untested but should work) design files for us on GitHub. These modules can vary, by manufacturer and motherboard series, but with each module published, a bunch of hackers can save money – and get a weekend project virtually guaranteed to work out.

Regardless of whether the goal of running Windows 11 is ultimately worthwhile, it has been achieved. With scalpers preying on people who just want to use their hardware with a new OS, rolling your own TPM PCB is a very attractive solution! Last time we covered a DIY TPM module for ASrock server motherboards, we had a vivid discussion in the comments, and if you’re looking to create your own TPM board, you could do worse than checking them out for advice and insights!

Build A TPM Module For Your Server

April 6, 2022 by 60 Comments

One of the big stories surrounding the announcement of Windows 11 was that it would require support for TPM 2.0, or Trusted Platform Module, to run. This takes the form of an on-board cryptographic processor, which Microsoft claims will help against malware, but which perhaps more importantly for Redmond, can be used to enforce DRM.  Part of the standard involves a hardware module, and [Zane] has built a couple of them for ASrock server motherboards.

The chip in question is the Infineon SLB9965, which with a bit of research was found to map more or less directly to the pins of the TPM socket on the motherboard. The interesting thing here lies in the background research it gives into TPMs, and furthermore the links to other resources dealing with the topic. The chances are that most readers needing a TPM will simply buy one, but all knowledge is useful when it comes to these things.

Our weekly security roundup has been keeping an eye on the use of TPMs for a while, and has even shown us some ways that people have used to bypass the modules.

This Week In Security: Fail2RCE, TPM Sniffing, Fishy Leaks, And Decompiling

July 30, 2021 by 10 Comments

Fail2ban is a great tool for dynamically blocking IP addresses that show bad behavior, like making repeated login attempts. It was just announced that a vulnerability could allow an attacker to take over a machine by being blocked by Fail2ban. The problem is in the mail-whois action, where an email is sent to the administrator containing the whois information. Whois information is potentially attacker controlled data, and Fail2ban doesn’t properly sterilize the input before piping it into the mail binary. Mailutils has a feature that uses the tilde key as an escape sequence, allowing commands to be run while composing a message. Fail2ban doesn’t sanitize those tilde commands, so malicious whois data can trivially run commands on the system. Whois is one of the old-school unix protocols that runs in the clear, so a MItM attack makes this particularly easy. If you use Fail2ban, make sure to update to 0.10.7 or 0.11.3, or purge any use of mail-whois from your active configs. Continue reading “This Week In Security: Fail2RCE, TPM Sniffing, Fishy Leaks, And Decompiling” →