CPUID - Security and Privacy Risks ‎

From Kicksecure

Figure: cpuid Screenshot 1 / 4 (more screenshots) (usage)


CPUID is a processor function that allowing software to discover the model and capabilities of the processor. This can be a security or privacy risk.

Two cases.

  • A) Remote CPUID: Even if the user has JavaScript enabled in their browser, websites cannot remotely detect the user's CPU model and capabilities.
  • B) Local CPUID: Unfortunately, locally running applications can use the non-privileged CPU instruction CPUID. This cannot be prevented. This issue is unspecific to Kicksecure ™.

The technical background of these two cases is being elaborated below.

CPUID Information[edit]


What information does CPUID give?

Any information that is related to Processor including the design of the Processor can be fetched using CPUID instructions. For example, we can get the following information using CPUID using different leaf values:

  • Processor Vendor name
  • Processor name, Serial number
  • Number of Cores
  • Features supported like AVX512
  • L1, L2 and L3 Cache Size
  • Cache Topology
  • Thermal and Power Management

CPUID Screenshots[edit]

Author of screenshots: screenshots.debian.net/package/cpuid

Figure: cpuid Screenshot 1 / 4


Figure: cpuid Screenshot 2 / 4


Figure: cpuid Screenshot 3 / 4


Figure: cpuid Screenshot 4 / 4


CPUID Technical Background[edit]

  • Importance of this wiki chapter: If the reader is time-poor, the rest of the text inside this box can be skipped.
  • Affected operating systems: All. This issue is unspecific to Kicksecure ™.
  • Affected computers: All Intel and AMD CPUs are affected since 1993.
  • Workarounds available? None. There are also no virtualizers capable to hide this information. Perhaps emulators might be able to hide this information since the CPU is fully emulated (as opposed to be being virtualized) but these are too slow to be considered for production use.
  • CPUID technical introduction: Quote cpuid man page (Underline added.):
    • The CPUID instruction can be directly executed by a program using inline assembler. However this device allows convenient access to all CPUs without changing process affinity. Most of the information in cpuid is reported by the kernel in cooked form either in /proc/cpuinfo or through subdirectories in /sys/devices/system/cpu. Direct CPUID access through this device should only be used in exceptional cases.

  • Remote websites: Cannot fingerprint the user to remotely detect the the user's CPU model and capabilities. There are no test pages that claim to do it. One websites might make a first impression that it can be done, but it's not possible, see cpuid visualizer . A different project, CPUID in JavaScript cannot do it either. While JavaScript is often viewed as synonym with the browser, JavaScript can also be used with out a browser. The CPUID in JavaScript program might work with JavaScript on a server but not with JavaScript in a browser.
    • Popular demand by many website owners: Many people asked about this generally on stackexchange (detecting hardware information using JavaScript) but nobody had a solution for CPU model and capabilities specifically.
    • No live demonstration available: There is no hosted web service that demonstrates this feature. At least a few of the many Browser Tests would implement this. Specifically likely the popular Fingerprint.com improve their service with CPUID if this was possible.
    • Specifically asking: This question has been specifically directed at only project that does something similar to this, which is CPUID in JavaScript. The project does not claim it works in browsers. Question for this specifically has been asked anyhow, see Can cpuid x86 in JavaScript run inside a browser?
    • AmIUnique feature request: detect CPUID using JavaScript - reply received in summary: Not possible.
    • Alternative browser API: Since this is not possible, an alternative browser API feature navigator.hardwareConcurrency was implemented by browsers vendors.
    • Alternative to CPUID: The closest alternative to CPU fingerprinting using CPUID that has been found is WebCPU .
  • Non-solutions: Even security-misc's hide-hardware-info.service cannot hide CPUID.
  • Future: The Kicksecure ™ project will not be able to fix the CPUID issue. At author if this wiki page is not aware of any virtualizer or kernel project which is interested in "hardware privacy". Very few related bug reports / feature requests exist. Users, researchers and developers interested in getting this issue fixed are encouraged to use the principles of Generic Bug Reporting and Free Support Principle, in short, reproduce, describe the issue without reference to Kicksecure ™ and contact upstream projects (such as virtualizers, kernel) directly.
  • Related: VM Fingerprinting
  • References:

cpuid usage[edit]

cpuid is a program that uses the processor's cpuid function and shows its result.

Note, that the availability or unavailability of the cpuid from the package repository is irrelevant. This is because the CPU's cupid function is a non-privileged instruction. Meaning, any other application could easily call the same CPU function.

Optional: Users interested to learn more or view their CPUID could use cpuid.

1. Open a terminal.

If you are using Kicksecure ™ inside Qubes, complete the following steps.

Qubes App Launcher (blue/grey "Q")Kicksecure ™ App Qube (commonly named kicksecure)Xfce Terminal

If you are using a graphical Kicksecure ™ with XFCE, run.

Start MenuXfce Terminal

2. Software installation

Install cpuid. To accomplish that, the following steps A. to D. need to be done.

A. Update the package lists.

sudo apt update

B. Upgrade the system.

sudo apt full-upgrade

C. Install the cpuid package.

Using apt command line parameter --no-install-recommends is in most cases optional.

sudo apt install --no-install-recommends cpuid

D. Done.

The procedure of installing cpuid is complete.

3. Run cpuid.


4. Done.

The process of showing information from the processor's cpuid function has been completed.

CPUID visualizer[edit]

/proc/cpuinfo versus cpuid[edit]

On Linux systems, there are at least two ways to access CPU information.

  • A) /proc/cpuinfo: Is a virtual file provided by the kernel providing information about the CPU.
  • B) cpuid: Is a program that queries the CPU's cpuid function directly to get information about the CPU.

CPUID Spoofing Testing[edit]

This wiki chapter documents ways to check if any potential ways of CPUID spoofing are effective. It does not provide instructions on how to perform CPUID spoofing which might be impossible on the Intel / AMD64 platform.

run twice and compare method:

1. Run cpuid (or an alternative, if any is available) before making any attempts of CPUID spoofing. Store its output in a text file cpuid1.txt.

2. Apply any possibly available steps to spoof the CPUID.

The user could experiment with emulators such as bochs, virtualizers such as VirtualBox and its settings [1] or other options.

3. Run cpuid again. Store its output in text file cpuid2.txt.

4. Compare the two text files.

Due to the lengthy output of cpuid with many different details, manually comparing the two files could be cumbersome and error-prone. Instead, using a file comparison tool of the user's choice is recommended.


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