4 ms·

How is this method any different from encrypting the private key without any secure enclave? Isn't it just using a password derived key?

arianvanp 10mo ago
The key is stored encrypted with a unique symmetric key that only your secure enclave knows until the point that you export it. It then re-encrypts it with the password. Until you export it it's just as strong as an enclave-generated one. Obviously don't keep the exported password encrypted key around and don't use a weak password for export.
- gruez 10mo ago
  >The key is stored encrypted with a unique symmetric key that only your secure enclave knows until the point that you export it. It then re-encrypts it with the password. But what's the security benefit of this compared to having a keyfile? So far as I can tell from the commands you provided, there's no real difference, aside from a hacker having to modify their stealer script slightly.
  - arianvanp 10mo ago
    Why is it more secure: a key file on disk is decrypted into memory every time you enter your passphrase. It means the key is around in plain text in the memory of ssh or ssh-agent. Which means it's extractable by an attacker. An exportable key does all the signing inside the secure enclave and never exposes the decrypted key to OS memory. The exported key you can keep in a safe for disaster recovery. You shouldn't keep it on your computer of course.
    - traceroute66 10mo ago
      > The exported key you can keep in a safe for disaster recovery. No. Your "disaster recovery" should be either a second device with a Secure Enclave, or a Yubikey. Making it exportable from the Secure Enclave defeats the whole purpose.
    - gruez 10mo ago
      >It means the key is around in plain text in the memory of ssh or ssh-agent. Which means it's extractable by an attacker. An exportable key does all the signing inside the secure enclave and never exposes the decrypted key to OS memory. But malware can just tell the secure enclave to export the key? Yes, they'll have to write new code to do that, but it's not particularly hard (it's 1 line code from your example above), and it's security through obscurity.
      - monocularvision 10mo ago
        The malware would have to prompt for biometric authentication before exporting.
        Nextgrid 10mo ago
        So it just has to wait until you’re about to do a legitimate operation requiring authentication, intercept that to export the key, and cancel the real one with a bogus error (and you’ll just try again without any second thoughts). MacOS has also no concept of secure desktop/etc where the OS can use some privileged UI to explicitly tell you what you are signing and prompt for PIN/biometrics. It’s in fact a well-known problem where legitimate dialogs for system/Apple ID password have no distinguishing features from fake ones.
        grosswait 10mo ago
        Couldn’t any type of dialogue be faked? What are you suggesting is possible but not implemented?
        Nextgrid 10mo ago
        Generally dialogs that require sensitive input provide some way for the user to ensure they are issued by the OS and not a random program. Windows historically used the Secure Attention Key (that's why domain-linked machines used to require pressing Ctrl+Alt+Del to login, to train users to only enter credentials in secure contexts) which is a key combo that the OS always intercepts and thus once pressed you can be assured you are typing into a trusted UI and not a piece of malware emulating the trusted UI. Of course, this was back in the day when computers were primarily a productivity tool and not an ad delivery vehicle, so it's unlikely this problem will ever be solved.
    - deleted 10mo ago
      [deleted]
  - conradev 10mo ago
    Unlike a TPM and like a YubiKey, you can configure the secure enclave to require presence (via Touch ID) so that a stealer script would be stopped with a prompt.
    - lxgr 10mo ago
      Until the next time you touch your Touch ID for any other operation. It seems realistic for an attacker script to anticipate that and open its own prompt at the right moment (i.e. with your finger already on the way to the button).
- deleted 10mo ago
  [deleted]

arianvanp 10mo ago

The key is stored encrypted with a unique symmetric key that only your secure enclave knows until the point that you export it. It then re-encrypts it with the password. Until you export it it's just as strong as an enclave-generated one. Obviously don't keep the exported password encrypted key around and don't use a weak password for export.

gruez 10mo ago
>The key is stored encrypted with a unique symmetric key that only your secure enclave knows until the point that you export it. It then re-encrypts it with the password. But what's the security benefit of this compared to having a keyfile? So far as I can tell from the commands you provided, there's no real difference, aside from a hacker having to modify their stealer script slightly.
- arianvanp 10mo ago
  Why is it more secure: a key file on disk is decrypted into memory every time you enter your passphrase. It means the key is around in plain text in the memory of ssh or ssh-agent. Which means it's extractable by an attacker. An exportable key does all the signing inside the secure enclave and never exposes the decrypted key to OS memory. The exported key you can keep in a safe for disaster recovery. You shouldn't keep it on your computer of course.
  - traceroute66 10mo ago
    > The exported key you can keep in a safe for disaster recovery. No. Your "disaster recovery" should be either a second device with a Secure Enclave, or a Yubikey. Making it exportable from the Secure Enclave defeats the whole purpose.
  - gruez 10mo ago
    >It means the key is around in plain text in the memory of ssh or ssh-agent. Which means it's extractable by an attacker. An exportable key does all the signing inside the secure enclave and never exposes the decrypted key to OS memory. But malware can just tell the secure enclave to export the key? Yes, they'll have to write new code to do that, but it's not particularly hard (it's 1 line code from your example above), and it's security through obscurity.
    - monocularvision 10mo ago
      The malware would have to prompt for biometric authentication before exporting.
      - Nextgrid 10mo ago
        So it just has to wait until you’re about to do a legitimate operation requiring authentication, intercept that to export the key, and cancel the real one with a bogus error (and you’ll just try again without any second thoughts). MacOS has also no concept of secure desktop/etc where the OS can use some privileged UI to explicitly tell you what you are signing and prompt for PIN/biometrics. It’s in fact a well-known problem where legitimate dialogs for system/Apple ID password have no distinguishing features from fake ones.
        grosswait 10mo ago
        Couldn’t any type of dialogue be faked? What are you suggesting is possible but not implemented?
        Nextgrid 10mo ago
        Generally dialogs that require sensitive input provide some way for the user to ensure they are issued by the OS and not a random program. Windows historically used the Secure Attention Key (that's why domain-linked machines used to require pressing Ctrl+Alt+Del to login, to train users to only enter credentials in secure contexts) which is a key combo that the OS always intercepts and thus once pressed you can be assured you are typing into a trusted UI and not a piece of malware emulating the trusted UI. Of course, this was back in the day when computers were primarily a productivity tool and not an ad delivery vehicle, so it's unlikely this problem will ever be solved.
  - deleted 10mo ago
    [deleted]
- conradev 10mo ago
  Unlike a TPM and like a YubiKey, you can configure the secure enclave to require presence (via Touch ID) so that a stealer script would be stopped with a prompt.
  - lxgr 10mo ago
    Until the next time you touch your Touch ID for any other operation. It seems realistic for an attacker script to anticipate that and open its own prompt at the right moment (i.e. with your finger already on the way to the button).
deleted 10mo ago
[deleted]