fix(impersonate): exchange user JWTs with RFC 7523 jwt-bearer grant - #3675
#3675Open
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fix(impersonate): exchange user JWTs with RFC 7523 jwt-bearer grant#3675matiasbertani wants to merge 1 commit intogoogleapis:maingoogleapis/google-api-go-client:mainfrom matiasbertani:impersonate-jwt-bearer-grantmatiasbertani/google-api-go-client:impersonate-jwt-bearer-grantCopy head branch name to clipboard
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The user (Subject) flow exchanged the signJwt-signed JWT at oauth2.googleapis.com/token using the pre-RFC 7523 legacy grant (grant_type=assertion). Since mid-July 2026 that path rejects JWTs signed with recently-rotated system-managed keys with "invalid_grant: Invalid JWT Signature". Exchange with the standard urn:ietf:params:oauth:grant-type:jwt-bearer grant instead, matching google-auth-library-python's behavior for the same flow. Fixes googleapis#3671
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Fixes #3671
The user (Subject) flow exchanged the signJwt-signed JWT at oauth2.googleapis.com/token using the pre-RFC 7523 legacy grant (grant_type=assertion). Since mid-July 2026 that path rejects JWTs signed with recently-rotated system-managed keys with "invalid_grant: Invalid JWT Signature". Exchange with the standard urn:ietf:params:oauth:grant-type:jwt-bearer grant instead, matching google-auth-library-python's behavior for the same flow.