Issuer with IRSA needs ambient credentials flag

[rossigee]

This should help reduce the amount of time people might waste trying to figure out how to resolve the following error:

error instantiating route53 challenge solver: unable to construct route53 provider: empty credentials; perhaps you meant to enable ambient credentials?

A couple of related bug reports:

• Using workload identity instead of exporting service account keys on GKE cert-manager#3009
• DNS01 Challenge via AWS Route53 on AWS EKS 1.15 not working cert-manager#3079

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[jetstack-bot]

Hi @rossigee. Thanks for your PR.

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[rossigee]

/assign @meyskens

[tstraley]

I'm curious if any of the maintainers can chime in here with why the Issuer and ClusterIssuer have different functionality here? Shouldn't either one be trying to use the modern AWS SDK to its full extent and collecting credentials from all supported sources?

[wallrj]

Thanks @rossigee

And apologies for the delayed review.
Judging by the number of issues mentioning the ambient-credentials flags,
this is a much needed addition to the documentation.

I was surprised at the lack of docs and when I went digging into the origin of this feature,
I found that that original author did write documentation for this:

• https://github.com/jetstack/cert-manager/blob/95883c47dd31ad6c0e7652a192e4c51981d67592/docs/user-guides/ambient-credentials.md
• Allow non-static AWS credentials for Route 53, gated by "ambient credentials" flags cert-manager#363

That document contains some important extra information about why ambient-credentials are disabled by default for Issuer.
Please review that document and copy over all the content that you think is still relevant.

Thanks.

[wallrj]

/ok-to-test

[tstraley]

I don't think this is quite correct. If assuming a role (like in the example above) and using static credentials, then the ambient credentials aren't necessary.

The ambient credentials ARE necessary when using AWS_WEB_IDENTITY_TOKEN_FILE (as is the case of IAM Role for Service Accounts) or IAM instance profile via instance metadata.

I'd argue that this documentation should be moved into the IRSA section below, as a result.

[wallrj]

I'm curious if any of the maintainers can chime in here with why the Issuer and ClusterIssuer have different functionality here? Shouldn't either one be trying to use the modern AWS SDK to its full extent and collecting credentials from all supported sources?

I found the answer in a document which we obviously forgot to port over to the new website:

https://github.com/jetstack/cert-manager/blob/95883c47dd31ad6c0e7652a192e4c51981d67592/docs/user-guides/ambient-credentials.md?plain=1#L33-L46

## When are Ambient Credentials used


Ambient credentials are supported for the 'route53' ACME dns01 provider.


They will only be used if no credentials are supplied, even if the supplied credentials are incorrect.


By default, they may be used by ClusterIssuers, but not regular issuers. The
`--issuer-ambient-credentials` and
`--cluster-issuer-ambient-credentials=false` flags on the cert-manager may be
used to override this behavior.


Note that ambient credentials are disabled for regular Issuers by default to
ensure unprivileged users who may create issuers cannot issue certificates
using any credentials cert-manager incidentally has access to.

So I suggest we add that to the current docs

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@rossigee: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

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pull-cert-manager-website-verify	f855dce	link	true	/test pull-cert-manager-website-verify

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