Properly support a TLS-wrapped OCSP responder

[Asgavar]

What this PR does / why we need it:

Current implementation of OCSP stapling makes use of the DNS caching machinery¹, which results in resty.http not seeing the actual host name of the OCSP responder. On HTTP level, this is already mitigated via overriding the Host header, but if a given responder operates on a HTTPS endpoint (a setup which, admittedly, isn't very popular due to its chicken-and-egg caveats involved but is nonetheless legal²) the connection will fail to be established. A relevant (and a bit redacted) excerpt from logs:

2023/07/02 18:13:23 [info] 112#112: *29039 [lua] dns.lua:32: cache_set(): cache set for 'my.ocsp.responder' with value of [10.1.2.3, 10.4.5.6, 10.7.8.9] and ttl of 30., context: ngx.timer, client: 127.0.0.1, server: 0.0.0.0:442
2023/07/02 18:13:23 [error] 112#112: *29039 lua ssl certificate does not match host "10.1.2.3", context: ngx.timer, client: 127.0.0.1, server: 0.0.0.0:442
2023/07/02 18:13:23 [error] 112#112: *29039 [lua] certificate.lua:143: fetch_and_cache_ocsp_response(): could not get OCSP response: certificate host mismatch, context: ngx.timer, client: 127.0.0.1, server: 0.0.0.0:442

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• CVE Report (Scanner found CVE and adding report)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation only

Which issue/s this PR fixes

Haven't seen any that'd touch this problem.

How Has This Been Tested?

I've test-drive deployed this patch to an instance serving certs from an in-house CA having its OCSP responder operating on HTTPS (and putting a https:// OCSP URLs in the certs themselves) and apparently this change suffices for the stapling process to properly work.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have added unit and/or e2e tests to cover my changes.
• All new and existing tests passed.

Footnotes

1. https://github.com/kubernetes/ingress-nginx/blob/ebb6314/rootfs/etc/nginx/lua/certificate.lua#L81 ↩

2. https://datatracker.ietf.org/doc/html/rfc2560#appendix-A.1.1 ↩

[linux-foundation-easycla]

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• ✅ login: Asgavar / name: Artur Juraszek (a4efb40)

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[Asgavar]

/meow

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@Asgavar:

In response to this:

/meow

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[rikatz]

/ok-to-test

[rikatz]

/lgtm
/approve
Thank you!

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Asgavar, rikatz

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