webhook: new flag to configure the webhook server's minimum TLS version

[alebedev87]

Issue

N/A

Description

The goal of this PR is to support environments where TLS versions other than 1.3 are still used, mainly FIPS enabled systems. The boringcrypto enabled builds check for the maximum FIPS TLS version which is set to TLS1.2.

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

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[johngmyers]

We definitely shouldn't support 1.0 or 1.1

[alebedev87]

Yeah, these ones are too outdated for now. I added them since the controller-runtime still supports them. I'm fine to remove them along with "" as it turns into 1.0.

[alebedev87]

1.0, 1.1 removed.

[johngmyers]

I think we should revert #2457 and make 1.2 the minimum version across the board. @oliviassss ?

[johngmyers]

My opinion is that we should not be exposing this as configuration; administrators should not have to bother with this kind of stuff.

On the other hand, we probably should cater somewhat for people who are constrained to work within the idiotic FIPS-140 stuff.

If there are problematic ciphers in the Go's default TLS 1.2 support (I would suggest we check) then we can just hardcode-disable those.

[oliviassss]

@johngmyers, yeah I agree 1.0 and 1.1 are outdated, AWS is also deprecating the 1.0 and 1.1 for the API endpoints: https://aws.amazon.com/blogs/security/tls-1-2-required-for-aws-endpoints/. And we could make 1.2 the minimum.

But I'm just a bit concerned about the 1.2 compatibility with k8s 1.22+ (since we are supporting k8s 1.22+). By checking the changelogs, seems like TLS 1.2 is the min supported version since k8s 1.3?

[alebedev87]

But I'm just a bit concerned about the 1.2 compatibility with k8s 1.22+ (since we are supporting k8s 1.22+). By checking the changelogs, seems like TLS 1.2 is the min supported version since k8s 1.3?

Looking at KubeleConfiguration, the minimum TLS version is set to "" by default in 1.27 (API ref) which is later turn into TLS1.2 thanks to kubernetes/component-base/cli/flag#TLSVersion used by kubelet here. Which explains why I didn't see any problems with other controller-runtime based workloads which don't set TLSMinVersion on the latest Kubernetes releases.

So, TLS1.2 seems to be a safe default however it's indeed only intermediate security TLS profile. Maybe it still makes some sense to be in the modern profile by default (TLS1.3) and let some exotic environments like FIPS set TLS1.2. I don't have a strong opinion though, a revert to 1.2 by default would do the thing for me too.

[alebedev87]

"", 1.0, 1.1 versions removed, just in case we would decide to move on with the configurable approach.

[oliviassss]

@alebedev87, thanks, I think it's better to set TLS default version as 1.2, so it fits all the environments including FIPS, and allow the configuration for 1.3 for users who want stricter TLS version.

[alebedev87]

@oliviassss : so this PR still makes sense. You would like me to change the default version to TLS1.2?

[johngmyers]

Filed #3318

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PR needs rebase.

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[alebedev87]

Closing since #3318 reset the minimum TLS version to 1.2.