Check if TLS certificate and key file have been modified

[LeviHarrison]

This PR adds the capability to check the hashes of the client certificate and key files to see if they've been modified, as is already done with the CA file.

Fixes https://github.com/prometheus/prometheus/issues/9512

[roidelapluie]

I think we should only store the cert, you can not change the key without changing the cert.

[LeviHarrison]

The issue with that would be if someone were to change only the key, yes, the TLS configuration would be invalid, but instead of getting (what I think would be) a private key does not match public key error, they would continue to get whatever error they had before or nothing, because the configuration wouldn't be updated.

[fpetkovski]

We are also hitting this problem, anything we can help with to move the PR forward?

[LeviHarrison]

Apologies, I just need to find time to work on this.

[simonpasquier]

@LeviHarrison do you want me to pick up the work? This bug is becoming a significant issue for us right now.

[roidelapluie]

@LeviHarrison do you want me to pick up the work? This bug is becoming a significant issue for us right now.

Yes, I think you can review&rebase

[simonpasquier]

Rebased on top of main, I didn't change anything to the PR except for resolving the conflicts. Thanks a lot @LeviHarrison!

[simonpasquier]

@roidelapluie PTAL

[simonpasquier]

@roidelapluie friendly ping :)

[roidelapluie]

Thanks!