client-go: make generating certificate/key permissions more restrictive (600)

[lanycrost]

What type of PR is this?

/kind bug

What this PR does / why we need it:

GenerateSelfSignedCertKeyWithFixtures function as well as in other places keys and certificates and directories will be generated with more restrictive permissions.

Which issue(s) this PR fixes:

Fixes #110992

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

apiserver generated self-signed certificate permissions will be more restrictive

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[cici37]

/remove-sig api-machinery

[cici37]

/remove-sig api-machinery

[dims]

/ok-to-test
/assign @liggitt

[aojea]

/assign @enj
Add Mo too, he commented in the reported issue

[liggitt]

looks like there's a unit test explicitly checking the old values that needs updating:

    copycerts_test.go:260: cert "ca.crt" should have mode 0644, has 0600
    copycerts_test.go:260: cert "front-proxy-ca.crt" should have mode 0644, has 0600
    copycerts_test.go:260: cert "sa.pub" should have mode 0644, has 0600
    copycerts_test.go:260: cert "etcd/ca.crt" should have mode 0644, has 0600

[liggitt]

This is the only change in this PR I think we should consider.

That said, this code path is producing fixture files to get checked in to source control... I don't have a good sense for how a user-only readable file will behave in systems where one actor is checking out from source control and another is running the tests

[liggitt]

Reading further, it looks like git only tracks the executable bit, and group/other permissions are solely governed by the user's umask when checking out.

That means that generating this with 0600 will likely produce fixtures with 0600 permissions, but that once they are committed and checked out, the file permissions will likely still be 0644. But since they are test fixture files being committed to source, that doesn't really matter anyway.

[lanycrost]

/retest

[lanycrost]

@liggitt Thanks for your valuable review. Regarding the fixture files, I understand your concern about user-only readable files and how they may behave in systems with multiple actors. It may be worthwhile to explore alternative approaches, such as generating the fixture files on the fly during testing, or having separate fixture files for each one. If I'm getting you right.

[liggitt]

Generating fixtures on the fly for unit tests was expensive on underpowered CI systems and led to problems. The fixtures this leads to are things like https://github.com/kubernetes/kubernetes/tree/master/cmd/kube-apiserver/app/testing/testdata which are never used in the context of a server which can be used to create real executing workloads, only unit/integration tests which are immediately torn down and deleted.

[liggitt]

/lgtm
/approve

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 79e28f126fd0b1d7749bfd85a831014cbc8afa54

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lanycrost, liggitt

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• staging/src/k8s.io/client-go/util/cert/OWNERS [liggitt]

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[cici37]

/triage accepted