35 lines
1.8 KiB
SQL
35 lines
1.8 KiB
SQL
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-- Bind a session cookie to a browser-held ECDSA keypair (DPoP, RFC 9449).
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--
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-- Each browser session that supports Web Crypto generates a P-256 keypair
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-- with `extractable: false` and stores it in IndexedDB. The public-key JWK
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-- thumbprint (RFC 7638, base64url-encoded SHA-256) is sent with the login
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-- request and stored here. Middleware then requires every subsequent
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-- request on the session to carry a valid DPoP proof signed by the paired
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-- private key. Stealing the cookie alone gets an attacker nothing — the
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-- private key never leaves the browser's crypto subsystem.
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--
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-- Nullable because:
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-- * pre-DPoP sessions created before this feature landed;
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-- * app-password / Nextcloud-client sessions (Basic Auth, no browser,
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-- no Web Crypto) will always have NULL here and are exempted at the
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-- middleware;
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-- * browsers without SubtleCrypto (very rare in 2026) fail the client-
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-- side keypair generation and log in unbound (fail-open per the
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-- `docs/plan/dpop.md` threat model).
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--
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-- Immutable per-session: set at INSERT time, never updated. That's the
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-- point — otherwise an attacker could downgrade a bound session by
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-- clearing the column.
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--
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-- Length is 43 characters for a base64url-encoded SHA-256 (32 bytes ×
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-- 4/3 = 43 chars, no padding). Cap at 64 to leave a little slack in
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-- case we later support larger thumbprints (e.g. SHA-384 for P-384).
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--
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-- No index needed — the column is read alongside the session row by
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-- primary key in the auth middleware, never queried in isolation.
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ALTER TABLE auth.sessions
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ADD COLUMN IF NOT EXISTS dpop_jkt VARCHAR(64);
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COMMENT ON COLUMN auth.sessions.dpop_jkt IS
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'DPoP JWK thumbprint (RFC 7638) binding this session to a browser-held keypair. NULL for app-password / legacy / unbound sessions.';
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