3 ms·

> So it didn't matter how many times we rotated our secrets I'm confused, did you rotate your certs or your secrets?

by groestl 3y ago

charcircuit 3y ago
The private key of a cert is a secret that is not reused between certs.
- groestl 3y ago
  Says who?
- comprambler 3y ago
  The private key is definitely reused between certs unless you go through a process of rekeying which requires a new CSR.
  - charcircuit 3y ago
    It's technically possible to reuse it, but letsencrypt / certbot do not reuse it by default. You have to go out of your way and do extra work to reuse a CSR when renewing a cert.
    - woodruffw 3y ago
      The original poster didn't mention LE or anything else that uses ACME. It's pretty easy to reuse a key in a bespoke PKI setup; the X.509 builder APIs that I've used make it trivial. Which doesn't make it a good idea, of course.
franga2000 3y ago
Can you do one without the other? The public key is derived from the secret/private key, so changing one means also changing the other...
- groestl 3y ago
  But a (public key) certificate is not a public key. A cert is a public key A (to private key a), signed by another key b, of which public key B is known. To rotate a cert means resigning the public key A (which is still derived from the same private key a). Edit: relevant, especially flow2k's answer, which explains why this is _not_ just security theater https://security.stackexchange.com/questions/85963/what-is-the-purpose-of-frequently-rotating-tls-certificates-without-changing-und https://security.stackexchange.com/questions/85963/what-is-t...
  - franga2000 3y ago
    Ah, so basically just renewing before it's due, that makes sense. For some reason it didn't occur to me that rotate could mean that too. This does still leave the problem of the old certs being valid though. This only makes sense as a security practice if the certs are short-lived, which theirs apparently weren't. If the certs live much longer than the rotation window, this really is just security theatre. I do think thaumasiotes has a point and GP's company probably misinterpreted the rotation requirements and short lifespans were implied in the requirement.
    - groestl 3y ago
      > If the certs live much longer than the rotation window, this really is just security theatre. That's very true. > and GP's company probably misinterpreted the rotation requirements and short lifespans were implied in the requirement. Or GP didn't know that the company was indeed using short expiration times, and somehow confused it with certificate revocation (called "cancelled" in the post).
kevin_nisbet 3y ago
Sorry about the imprecise language, this system rotated both together.

> So it didn't matter how many times we rotated our secrets I'm confused, did you rotate your certs or your secrets?

charcircuit 3y ago

The private key of a cert is a secret that is not reused between certs.

groestl 3y ago
Says who?
comprambler 3y ago
The private key is definitely reused between certs unless you go through a process of rekeying which requires a new CSR.
- charcircuit 3y ago
  It's technically possible to reuse it, but letsencrypt / certbot do not reuse it by default. You have to go out of your way and do extra work to reuse a CSR when renewing a cert.
  - woodruffw 3y ago
    The original poster didn't mention LE or anything else that uses ACME. It's pretty easy to reuse a key in a bespoke PKI setup; the X.509 builder APIs that I've used make it trivial. Which doesn't make it a good idea, of course.

franga2000 3y ago

Can you do one without the other? The public key is derived from the secret/private key, so changing one means also changing the other...

groestl 3y ago
But a (public key) certificate is not a public key. A cert is a public key A (to private key a), signed by another key b, of which public key B is known. To rotate a cert means resigning the public key A (which is still derived from the same private key a). Edit: relevant, especially flow2k's answer, which explains why this is _not_ just security theater https://security.stackexchange.com/questions/85963/what-is-the-purpose-of-frequently-rotating-tls-certificates-without-changing-und https://security.stackexchange.com/questions/85963/what-is-t...
- franga2000 3y ago
  Ah, so basically just renewing before it's due, that makes sense. For some reason it didn't occur to me that rotate could mean that too. This does still leave the problem of the old certs being valid though. This only makes sense as a security practice if the certs are short-lived, which theirs apparently weren't. If the certs live much longer than the rotation window, this really is just security theatre. I do think thaumasiotes has a point and GP's company probably misinterpreted the rotation requirements and short lifespans were implied in the requirement.
  - groestl 3y ago
    > If the certs live much longer than the rotation window, this really is just security theatre. That's very true. > and GP's company probably misinterpreted the rotation requirements and short lifespans were implied in the requirement. Or GP didn't know that the company was indeed using short expiration times, and somehow confused it with certificate revocation (called "cancelled" in the post).

kevin_nisbet 3y ago

Sorry about the imprecise language, this system rotated both together.