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fix(auth): strip -fips suffix from AWS service name in SigV4 signing - #18920
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This pull request adds support for AWS FIPS endpoints (such as sts-fips) by stripping the -fips suffix from the host name when determining the AWS service name in _generate_authentication_header_map. It also includes a corresponding unit test to verify authentication header generation with a FIPS STS endpoint. No review comments were provided, so there is no additional feedback.
macastelaz
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October 29, 2026 20:29
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🤖 I have created a release *beep* *boop* --- ## [2.62.1](google-auth-v2.62.0...google-auth-v2.62.1) (2026-11-02) ### Bug Fixes * **auth:** strip -fips suffix from AWS service name in SigV4 signing ([#18920](#18920)) ([2e1899e](2e1899e)) * **auth:** use an unencrypted key for mTLS certificate rotation ([#18709](#18709)) ([8166325](8166325)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please). Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
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When signing AWS STS GetCallerIdentity requests against regional FIPS endpoints (
sts-fips.{region}.amazonaws.com), theHostheader must remainsts-fips.{region}.amazonaws.com, whereas the AWS SigV4 credential scope and signing key derivation require the canonical service name (sts).Previously,
_generate_authentication_header_mapderivedservice_name = host.split(".")[0], which producedsts-fipsand caused AWS STS to reject the signed request withSignatureDoesNotMatch: Credential should be scoped to correct service: 'sts'.This change strips any trailing
-fipssuffix from the extracted hostname label when computingservice_name.Manual Testing
End-to-end reproduction script and observed pre-fix / post-fix output against GCP STS (
https://sts.googleapis.com/v1/token) and AWS STS (https://sts-fips.us-east-2.amazonaws.com):