fix: generate valid EKS authentication token payload#4779
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Build the EKS bearer token from the presigned STS GetCallerIdentity URL directly instead of URL-encoding the whole presigned URL first. The AWS signer already returns a URL with encoded query parameters, and encoding the entire URL again makes the decoded token payload an encoded URL string rather than the presigned STS URL expected by EKS. Set the STS request path explicitly to "/" so the generated presigned URL matches the accepted EKS token payload shape. This fixes EKSAuthentication requests failing with 401 Unauthorized.
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/lgtm I'm trusting this since I don;t have an EKS cluster to validate on. We'll revert if it breaks people. |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: brendandburns, hwayoungjun The full list of commands accepted by this bot can be found here. The pull request process is described here DetailsNeeds approval from an approver in each of these files:
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Description
EKSAuthenticationcurrently URL-encodes the entire presigned STSGetCallerIdentityURL before building thek8s-aws-v1.bearer token.However, the presigned URL returned by the AWS signer already contains encoded query parameters. Encoding the entire URL again makes the decoded token payload an encoded URL string, rather than the presigned STS URL form used by
aws-iam-authenticatorand shown in the EKS docs.For example, the decoded token payload form is:
With the extra full-URL encoding step, the decoded payload instead becomes an encoded URL string:
I observed this causing EKS API requests using
EKSAuthenticationto fail with401 Unauthorized.This change builds the EKS bearer token from the presigned STS URL directly. It also sets the STS request path explicitly to
/, matching the working presigned URL form verified against EKS:Changes
/References
Amazon EKS docs show a decoded
k8s-aws-v1.token payload as a presigned STSGetCallerIdentityURL withX-Amz-Expires=60:https://docs.aws.amazon.com/eks/latest/best-practices/identity-and-access-management.html
aws-iam-authenticatordocuments the same token construction: base64url encode the signed STSGetCallerIdentityrequest URL and prefix it withk8s-aws-v1.:https://github.com/kubernetes-sigs/aws-iam-authenticator#api-authorization-from-outside-a-cluster
Validation
I verified this manually against a real EKS cluster by using
EKSAuthenticationto generate the bearer token and callingCoreV1Api.listNamespace().The previous token payload failed with
401 Unauthorized, while the updated payload succeeded in listing namespaces.