4 ms·

It’s irritating that the “something you have” for most things can’t be “a laptop with a TPM.” It’s functionally equivalent to phone-based MFA. The only improve

• jsnell 5y ago
  Not quite equivalent. When an attacker compromises your laptop, they'll get all of the factors in one go: steal all your bearer tokens, steal your password with a key logger, and operate the TPM remotely.
  • alisonkisk 5y ago
  • vorpalhex 5y ago
    They would have to break your hard drive encryption AND have the laptop itself. Doable by a nation state? Sure. By Bob the mugger? No. That is fine for 98% of users.
    • tdeck 5y ago
      I think the parent comment was referring to a scenario where the attacker has code executing on your laptop, not necessarily a physical seizure of the device.
      • vorpalhex 5y ago
        That would mean the parent does not understand how a TPM operates. Several other commentors have provided good explanations to correct that fault.
    • raxxorrax 5y ago
      Not really sure of the capabilities of nation states. They buy the tools private companies come up with. But I think this is exaggerated security anyway. You want to keep stuff accessible. Binding anything to specific hardware is a terrible idea. My bank does that and it really sucks as a security mechanism.
  • littlecranky67 5y ago
    Isn't the idea that you cannot compromise the TPM remotely? At least Apples SecureEnclave require physical access and the fingerprint.
    • jsnell 5y ago
      You cannot compromise the TPM(e.g. read the keys stored in it, decrement increment-only counters), but most of the point of a TPM is that programs can call an interface and have the TPM perform operations using those keys. If someone compromises the machine enough to be able to run arbitrary code, they can issue those TPM operations remotely just the same as the legit software. What you describe is somewhat related, in that one can use a combination of a TPM + some kind of a biometric sensor to build a system like TouchID or Windows Hello, and that combination would not be remotely operable. But if e.g. your mTLS client cert is stored in the TPM, you certainly would not expect to swipe a fingerprint reader on every connection that the browser establishes to the mTLS domains.
      • littlecranky67 5y ago
        Thats why most of those TPMs have a requirement of physical interaction, i.e. you need to press a key on a Yubikey, or put a fingerprint down on an iPhone before they start this operation.
    • heavyset_go 5y ago
      I think the idea is that you cannot impersonate a specific TPM remotely. Get root on a system, though, and you can do whatever you want with the hardware you now have access to, including using its TPM for your own purposes.
      • littlecranky67 5y ago
        But thats exactly how it doesn't work - you are referring to Software-level TPMs. I.e. the SecureEnclave in iPhones work in a way that you can always put keys INTO the TPM chip, but cannot read it out back later, but rather have the SecureEnclave perform the crypto on chip (requiring some form of authentication, like a fingerprint read or a button press on Yubikeys). Even a full-root access should not compromise that.
• deathanatos 5y ago
  To add to what jsnell said, the Yubikey requires a tap. A physical interaction from someone sitting at a laptop, which is something a trojan cannot accomplish, and a tiny barrier from the human that doesn't materially contribute to fatigue. Now, I don't really know how much of a difference it makes for trojans, since presumably the resulting token/cookie/etc. could just be compromised in place. One might hope is scoped or at least of a more limited lifetime, I suppose. (Compromise by trojan is one of those "all roads seem to end in pwned" events to me.) I will note that it at least requires some authentication to happen prior to compromise, so if some IDS is blaring off alarm bells, all hope might not be lost if the device can be cut off fast enough. (The point here, though, vs. MS Authenticator, is that Authenticator adds nothing but massive amounts of friction over the supposed Yubikey state of affairs. Edit: although, see another of my comments: apparently MS Authenticator's behavior is configurable — for uh, some reason —_so I've switched it to "less annoying" mode. So, I'll forgive MS a touch, but AIUI it's the default to fatigue the user…)
• raxxorrax 5y ago
  Or a laptop without a TPM? Those devices are often much cleaner than the usual phone.