fix(gchat): bind add-on webhook verification to a configured identity - #787
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bensabic
approved these changes
Aug 5, 2026
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summary
endpoint-URL webhook verification accepted any
emailclaim matching the generic Workspace Add-on shape:/^service-\d+@gcp-sa-gsuiteaddons\.iam\.gserviceaccount\.com$/the
\d+is a GCP project number, and service agents areservice-{PROJECT_NUMBER}@gcp-sa-{SERVICE}...for the project that owns them. so that shape identifies "some Workspace Add-on", not this app's add-on, and it was the only thing standing between a public endpoint URL and a verified request. the method's own doc comment already stated the correct invariant, that the token is only trustworthy if it was issued to Google Chat itselfadds
workspaceAddOnServiceAccountEmail(envGOOGLE_CHAT_WORKSPACE_ADDON_SERVICE_ACCOUNT_EMAIL) and compares add-on identities exactly. when it is unset, add-on-shaped tokens are rejected rather than trusted by shape, with a log naming the option to setchat@system.gserviceaccount.comis untouched, so standalone Chat apps behave exactly as before. the project-number and Pub/Sub paths were already bound to exact identities and are unchangedbehavior
emailchat@system.gserviceaccount.comwhy not reject at construction
refusing to initialize when the option is absent would be the stricter-looking choice, but the adapter cannot tell Workspace Add-on mode from config alone, it only sees
endpointUrl. throwing there would break every ordinary endpoint-URL Chat app. rejecting add-on-shaped tokens at verification is the precise equivalent without the collateraltest plan
chat@system.gserviceaccount.comis still accepted with no add-on configemail_verified: falseis rejectedthe two rejection cases above returned 200 before this change and 401 after