nx_no_cookie_session.nx

nx_no_cookie_session.nx -- Ed25519-signed short-lived session token. V-MODAUTH-5 per NISHI_MODERN_AUTH_CHARTER §7. Replaces cookie- session sessions with a self-contained signed token. Per the NO-COOKIE / NO-TRACKING CARDINAL (C1 §1): NEVER a cookie. Token lifecycle: 1. After OPAQUE login succeeds, server calls nx_ncs_mint_token() with (user_id, realm_id) + short TTL. 2. Server returns base64(token) in JSON body. Client stores in sessionStorage (NOT localStorage — clears on tab close) OR holds in CLI process memory. 3. Client sends per-request: `X-Nishi-Session: <base64-token>`. 4. Server calls nx_ncs_validate_token() per protected request. 5. On expiry (~15min), client calls /wiki/admin/refresh-token to get a new token signed over the same user_id but fresh nonce + bumped expiry (no passphrase re-prompt). 6. Logout = client discards token. Server stateless; no invalidation list (per C10 full-privacy: no per-session server-side correlation). Token bound to short TTL minimizes leak-window risk. Token wire format (152 bytes BINARY; ~204 chars base64): offset 0..32 user_id_hash SHA-256("realm|||user_handle") offset 32..64 realm_id_hash SHA-256(NxAuthContext.realm_id) offset 64..72 expires_at_unix big-endian i64 seconds since epoch offset 72..88 nonce 16 random bytes (CSPRNG) offset 88..152 ed25519_sig signature over bytes[0..88] with server's long-term Ed25519 key SIGNATURE BINDING: server's Ed25519 pubkey is the SOLE authority here. Token holder = anyone with the right signed bytes within TTL. We do NOT bind to client cert (deferred V-MODAUTH-2 mTLS path) or client_pubkey. Short TTL is the leak-window control. COMPOSES per "avoid duplicate primitives" cardinal: nx_ed25519_signature ed25519_sign_full + ed25519_verify_full nx_csprng nonce randomness sha256 user_id + realm_id hash derivation helpers