Thursday, March 15th 2018
CTS Labs Posts Some Clarifications on AMD "Zen" Vulnerabilities
CTS-Labs the research group behind the AMD "Zen" CPU vulnerabilities, posted an addendum to its public-release of the whitepaper, in an attempt to dispel some of the criticism in their presentation in the absence of technical details (which they shared with AMD and other big tech firms). In their clarification whitepaper, quoted below, they get into slightly more technical details on each of the four vulnerability classes.
Clarification About the Recent Vulnerabilities
[CTS Labs] would like to address the many technical points and misunderstandings with a few technical clarifications about the vulnerabilities. The vulnerabilities described in our site are second-stage vulnerabilities. What this means is that the vulnerabilities are mostly relevant for enterprise networks, organizations and cloud providers.
Computers on enterprise networks occasionally get compromised - whether through phishing attempts, zero-day exploits or employees downloading the wrong file. High-security enterprise networks are equipped to deal with these kinds of "every-day" attacks. They do this by keeping their systems up to date, enabling security features, and employing additional measures such as endpoint security solutions.
The vulnerabilities described in amdflaws.com could give an attacker that has already gained initial foothold into one or more computers in the enterprise a significant advantage against IT and security teams.
The only thing the attacker would need after the initial local compromise is local admin privileges and an affected machine. To clarify misunderstandings - there is no need for physical access, no digital signatures, no additional vulnerability to reflash an unsigned BIOS. Buy a computer from the store, run the exploits as admin - and they will work (on the affected models as described on the site).
Attackers in possession of these vulnerabilities would receive the following additional capabilities:
These are the machines we have tested the vulnerabilities on. On our site, every red circle in the vulnerabilities map represents a working PoC that was tested in our lab.
This is the list of hardware that has been tested in our lab:
Requirements
Requirements:
The MASTERKEY set of vulnerabilities enable an attacker to execute unsigned code inside the PSP. Totaling a complete compromise of the Secure Processor. The exploit reflashes the BIOS to take advantage of the vulnerability:
Requirements:
The CHIMERA set of vulnerabilities are a set Manufacturer Backdoors left on the AMD Chipset, developed by Taiwanese company ASMedia.
Source:
Safe Firmware
[CTS Labs] would like to address the many technical points and misunderstandings with a few technical clarifications about the vulnerabilities. The vulnerabilities described in our site are second-stage vulnerabilities. What this means is that the vulnerabilities are mostly relevant for enterprise networks, organizations and cloud providers.
Computers on enterprise networks occasionally get compromised - whether through phishing attempts, zero-day exploits or employees downloading the wrong file. High-security enterprise networks are equipped to deal with these kinds of "every-day" attacks. They do this by keeping their systems up to date, enabling security features, and employing additional measures such as endpoint security solutions.
The vulnerabilities described in amdflaws.com could give an attacker that has already gained initial foothold into one or more computers in the enterprise a significant advantage against IT and security teams.
The only thing the attacker would need after the initial local compromise is local admin privileges and an affected machine. To clarify misunderstandings - there is no need for physical access, no digital signatures, no additional vulnerability to reflash an unsigned BIOS. Buy a computer from the store, run the exploits as admin - and they will work (on the affected models as described on the site).
Attackers in possession of these vulnerabilities would receive the following additional capabilities:
- Persistency: Attackers could load malware into the AMD Secure Processor before the CPU starts. From this position they can prevent further BIOS updates and remain hidden from security products. This level of persistency is extreme - even if you reinstall the OS or try to reflash the BIOS - it won't work. The only way to remove the attacker from the chip, would be to start soldering out chips. (we have seen a motherboard that had a socket where you can switch chips - then you could just put a new SPI chip).
- Stealth: Sitting inside the AMD Secure Processor or the AMD Chipset is, at the moment, outside the reach of virtually all security products. AMD chips could become a safe haven for attackers to operate from.
- Network Credential Theft: The ability to bypass Microsoft Credentials Guard and steal network credentials, for example credentials left by the IT department on the affected machine. We have a PoC version of mimikatz that works even with Credential Guard enabled. Stealing domain credentials could help attackers to move to higher value targets in the network.
- Specific AMD Secure Processor features for cloud providers, such as Secure Encrypted Virtualization, could be circumvented or disabled by these vulnerabilities.
These are the machines we have tested the vulnerabilities on. On our site, every red circle in the vulnerabilities map represents a working PoC that was tested in our lab.
This is the list of hardware that has been tested in our lab:
- BIOSTAR B350 GT3 Ryzen Motherboard.
- GIGABYTE AB350-GAMING 3
- HP EliteDesk 705 G3 SFF Ryzen Pro machine
- HP Envy X360 Ryzen Mobile Laptop
- TYAN B8026T70AV16E8HR EPYC SERVER
- GIGABYTE MZ31-AR0 EPYC SERVER
Requirements
- Physical access is not required. An attacker would only need to be able to run an EXE with local admin privileges on the machine.
- Write to SMM memory, leading to code execution in SMM.
- Reading and/or tampering with Credential Guard VTL-1 memory through the PSP.
- Ryzenfall-4, which achieves code execution inside the PSP, leads to all the attacker capabilities described above, as well as the capability to tamper with the PSP and its security features.
- An attacker can use RYZENFALL or FALLOUT to bypass Windows Credential Guard, steal network credentials, and then use these to move laterally through Windows-based enterprise networks
Requirements:
- Physical access is not required. An attacker would only need to be able to run an EXE with local admin privileges on the machine.
- Wait for reboot.
The MASTERKEY set of vulnerabilities enable an attacker to execute unsigned code inside the PSP. Totaling a complete compromise of the Secure Processor. The exploit reflashes the BIOS to take advantage of the vulnerability:
- On some motherboards - this works out of the box. This is because PSP firmware is often ignored by BIOS signature checks.
- In other cases - RYZENFALL #1-2 could be used as a prerequisite for MASTERKEY to achieve code execution in SMM and bypass BIOS signature checks made in SMM code.
- Even if all else fails, we believe using RYZENFALL-4 to write to SPI flash from inside the PSP is probably possible.
Requirements:
- Physical access is not required. An attacker would only need to be able to run an EXE with local admin privileges on the machine.
The CHIMERA set of vulnerabilities are a set Manufacturer Backdoors left on the AMD Chipset, developed by Taiwanese company ASMedia.
- This allows for an attacker to inject malicious code into the chip and take over the chipset (Read/Write/Execute).
- One set of backdoors in implemented in firmware, while the other is implemented in the actual logic gates of the chip (ASIC). Both yield to the same impact.
89 Comments on CTS Labs Posts Some Clarifications on AMD "Zen" Vulnerabilities
Real definition of an exploit or flaw is privilege escalation while not having any admin rights to begin with. That's what real exploits or flaws are. That you can gain admin access to an otherwise secure system. And all the "you just flash a BIOS". Motherboards often die when you flash them with official and specifically designed BIOS for the board. And these people make it sound like you can just patch any BIOS easily and make it a persistent threat/backdoor. It means the attacker needs to specifically know what motherboard you're using, what BIOS version you're using and modify it accordingly. That's again one huge load of "IF" to make it feasible for a mass deployment on home user systems that often have admin rights but are too much work for a targeted attack just so you end up finding bunch of gay porn on the system.
In all honesty, majority of companies and home users shouldn't really worry about it. Sure, if it can be fixed, AMD should work on eliminating these issues, but I wouldn't really worry about it. Companies that employ good policy of running workstations that clueless normies use under restricted policies and they are fine. As for normies with home computers, if you run OS in limited mode, good for you. If not, use a good antivirus and you should be fine as well.
It seems whole lot of panic for nothing here. Spectre and Meltdown were of higher concern because they wee true exploits that didn't require admin rights. You could poke the data from caches without any iirc.
Just go kill yourself already CTS clowns.
Interesting.
Edit: this is not enabled yet for the main site post view (in case you were looking for those hidden posts)
TPU never wrote anything positive about AMD. Wondering if the staff is payed by Intel, Nvidia and CTS labs.
watch the youtube video.
Even with admin rights there's tons of protection on various platforms, not to mention AV are also a last line of defense.
just no wizzard you know full well that bot-moderation is about the worst thing on the internet it never works its always wrong and its more trouble then its worth
--- on topic
and I am with xor this garbage should not be given the time of day it should not be on techpowerup along with several other craptacular articles that have been put up as of late cts has repeately proven they aren't worthy of the most basic respect granted to even amature security researchers and this is turning into a bunch of parroting
- some of the flaws seems to be similar to some that were already discovered in the Project zero of Google
- the flaw linked to the Asmedia chip could be a vulnerability on every board using an asmedia ASM1142 or even ASM1042
- of course exlpoiting those flaws means that you were already screw to begin with.
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