fix(idtoken): avoid double impersonation in tokenSourceFromBytes#3576
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quartzmo wants to merge 4 commits intogoogleapis:mainfrom
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fix(idtoken): avoid double impersonation in tokenSourceFromBytes#3576quartzmo wants to merge 4 commits intogoogleapis:mainfrom
quartzmo wants to merge 4 commits intogoogleapis:mainfrom
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This PR fixes a parallel double impersonation bug in the `idtoken` package. The library incorrectly does not use the `source_credentials` subfield in the JSON struct when constructing the inner client, and instead passes the entire credential JSON. This causes the lower layers (`htransport.NewClient`) to correctly (but unexpectedly for this context) build an authenticated HTTP client that is already impersonated, leading to self-impersonation when calling `generateIdToken`. This PR fixes the issue by extracting or recreating non-impersonated credentials before calling `impersonate.IDTokenSource`, avoiding the double wrap. Note: This PR does not add new unit tests for the call sequence because `impersonate.IDTokenSource` hardcodes the IAM credentials endpoint, making it impossible to intercept with a mock client or server without modifying that package. The existing unit tests in this package only cover type validation and do not successfully execute the full impersonation flow due to this same limitation. closes: googleapis#2301
hongalex
approved these changes
Apr 27, 2026
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This PR fixes a parallel double impersonation bug in the
idtokenpackage. The library incorrectly does not use thesource_credentialssubfield in the JSON struct when constructing the inner client, and instead passes the entire credential JSON. This causes the lower layers (htransport.NewClient) to correctly (but unexpectedly for this context) build an authenticated HTTP client that is already impersonated, leading to self-impersonation when callinggenerateIdToken.This PR fixes the issue by extracting or recreating non-impersonated credentials before calling
impersonate.IDTokenSource, avoiding the double wrap.Note: This PR does not add new unit tests for the call sequence because
impersonate.IDTokenSourcehardcodes the IAM credentials endpoint, making it impossible to intercept with a mock client or server without modifying that package. The existing unit tests in this package only cover type validation and do not successfully execute the full impersonation flow due to this same limitation.closes: #2301