6 ms·

Why? I think the best practice is that you should use different keys for different client devices, not that you should use different keys for different services

Why? I think the best practice is that you should use different keys for different client devices, not that you should use different keys for different services. A separate key per client allows a service to ban individual client devices if they get compromised, there's no practical scenario where a client device would want to ban individual services.

dmurray 5y ago
> A separate key per client allows a service to ban individual client devices if they get compromised This isn't possible with the "oh I synced your public keys from GitHub" pattern. The user might revoke a key later (we all rotate our keys every six months, right?), and remove it from GitHub but it can still be used to access your service. Maybe this is OK if you sync from GitHub on every access request (or cache for a short period), using it as a poor man's OAuth, but that's not what GP was proposing.
- keeganpoppen 5y ago
  but this is just a problem with copying the keys in general-- it has nothing to do with github specifically at all
- deleted 5y ago
  [deleted]
- judge2020 5y ago
  Solutions: https://gist.github.com/sivel/c68f601137ef9063efd7 https://gist.github.com/sivel/c68f601137ef9063efd7 - uses AuthorizedKeysCommand to make a remote server the authoritative source of your SSH keys, so (if you wanted to) you could make GitHub your key provider. https://github.com/ierror/ssh-permit-a38 https://github.com/ierror/ssh-permit-a38 - 3 years old but that's not necessarily an issue https://github.com/gravitational/teleport https://github.com/gravitational/teleport
- themacguffinman 5y ago
  Even if you had different keys to different services, you'd never revoke just one of those keys. If you're revoking a key because your client device was compromised: well, your other service keys on the same device are compromised too. If you're revoking a key because you regularly rotate your keys every 6 months: well, you're revoking all those other keys from all those other services at around the same frequency, separate service keys aren't helping you revoke less. There's never a practical scenario where you'd just revoke one service-client key-pair while the other service-client key-pairs are totally safe. Imagine your GitHub-specific private key was compromised somehow - a private key that has never left your laptop that also stores private keys for all your other services - do you think it's safe to only revoke your GitHub-specific key?
  - dmurray 5y ago
    This is exactly the problem. You need to revoke your key (maybe just one key, maybe lots of keys) but you can't revoke it from the new service, only from GitHub, because the process of authorizing you to the new service was append-only.
    - themacguffinman 5y ago
      It's not append-only. No one is suggesting that any new service must only pull keys from GitHub once and then it never changes. GitHub is just a convenient source to bootstrap from. You might need to go into your new service (possibly through another factor like physical access or web admin) and manually revoke compromised keys. I just don't think any of this is a reason to have a separate key for each service you use, that still seems rather unnecessary.

dmurray 5y ago

> A separate key per client allows a service to ban individual client devices if they get compromised This isn't possible with the "oh I synced your public keys from GitHub" pattern. The user might revoke a key later (we all rotate our keys every six months, right?), and remove it from GitHub but it can still be used to access your service. Maybe this is OK if you sync from GitHub on every access request (or cache for a short period), using it as a poor man's OAuth, but that's not what GP was proposing.

keeganpoppen 5y ago
but this is just a problem with copying the keys in general-- it has nothing to do with github specifically at all
deleted 5y ago
[deleted]
judge2020 5y ago
Solutions: https://gist.github.com/sivel/c68f601137ef9063efd7 https://gist.github.com/sivel/c68f601137ef9063efd7 - uses AuthorizedKeysCommand to make a remote server the authoritative source of your SSH keys, so (if you wanted to) you could make GitHub your key provider. https://github.com/ierror/ssh-permit-a38 https://github.com/ierror/ssh-permit-a38 - 3 years old but that's not necessarily an issue https://github.com/gravitational/teleport https://github.com/gravitational/teleport
themacguffinman 5y ago
Even if you had different keys to different services, you'd never revoke just one of those keys. If you're revoking a key because your client device was compromised: well, your other service keys on the same device are compromised too. If you're revoking a key because you regularly rotate your keys every 6 months: well, you're revoking all those other keys from all those other services at around the same frequency, separate service keys aren't helping you revoke less. There's never a practical scenario where you'd just revoke one service-client key-pair while the other service-client key-pairs are totally safe. Imagine your GitHub-specific private key was compromised somehow - a private key that has never left your laptop that also stores private keys for all your other services - do you think it's safe to only revoke your GitHub-specific key?
- dmurray 5y ago
  This is exactly the problem. You need to revoke your key (maybe just one key, maybe lots of keys) but you can't revoke it from the new service, only from GitHub, because the process of authorizing you to the new service was append-only.
  - themacguffinman 5y ago
    It's not append-only. No one is suggesting that any new service must only pull keys from GitHub once and then it never changes. GitHub is just a convenient source to bootstrap from. You might need to go into your new service (possibly through another factor like physical access or web admin) and manually revoke compromised keys. I just don't think any of this is a reason to have a separate key for each service you use, that still seems rather unnecessary.