security(server): store keyed hash of auth token in session cookie - #10691
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The session cookie is signed by starlette (tamper-proof) but not encrypted, so anyone holding the cookie could base64-decode it and read the raw auth token. Store HMAC-SHA256(secret, token) instead, so a leaked cookie no longer leaks the token or can be replayed as a bearer token / ?access_token= query param. The secret is still random per server process, but can now be pinned via MARIMO_SESSION_SECRET so sessions survive restarts or are shared across replicas. No new dependencies; stdlib hmac/hashlib only.
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dmadisetti
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Sep 1, 2026
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The session cookie is signed by starlette (tamper-proof) but not
encrypted, so anyone holding the cookie could base64-decode it and read
the raw auth token. Store HMAC-SHA256(secret, token) instead, so a
leaked cookie no longer leaks the token or can be replayed as a bearer
token / ?access_token= query param.
The secret is still random per server process, but can now be pinned
via MARIMO_SESSION_SECRET so sessions survive restarts or are shared
across replicas. No new dependencies; stdlib hmac/hashlib only.
Technically, the cookie is exactly as sensitive as the token itself so this does not add added protection when auth tokens are randomly generated, but in case any downstream user's use the same token each time, this can be another layer of defense in depth.