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Will Pfleger df3f28a2c4 feat(relay): add NIP-FI shadow mode for HTTP, WebSocket and admin (#8034)
Stack: this PR → #8062

🤖 Follows #8028 (merged).

Adds `BUZZ_NIP_FI_MODE=shadow`. The relay loads and validates the full
enforce configuration (issuers, communities, lifetimes, command
issuers), evaluates NIP-FI evidence wherever enforce would decide, and
records what enforce would have done, while every request, upgrade and
session behaves exactly as in `off`. The one approved exception is admin
disconnect: shadow verifies the command and returns `200`, where Off has
no verifier and returns `503`. It lets an operator measure the
would-deny rate, including Hosts missing from `BUZZ_NIP_FI_COMMUNITIES`,
before switching to `enforce`.

- **Mode predicates.** `NipFiMode` gains `is_off`, `restricts`,
`evaluates`, `enforces`, `denies_unconditionally` and `observes_only`,
built on two exhaustive `match` bases (`restricts`, `evaluates`);
`is_off` is a `matches!` and the rest derive from the bases, so a new
mode cannot silently fall into one side. Every call site uses them,
including the Git membership-lookup failure from #8005, which uses
`restricts()` so shadow keeps Off's body. A test scans each crate's
`src/` and fails on any `NipFiMode::<variant>` in production code
outside the predicate definitions and the env parser, which catches
`==`, `matches!` on any number of lines, `if let` and or-patterns.
- **Startup.** Shadow goes through enforce's path, so every enforce
startup refusal applies, including the required connection lifetime.
Missing-setting errors name the configured mode through one formatter
(`mode_requires`); the enforce text is byte-identical. Shadow builds the
assertion verifier and claims command replays under its own Redis
prefix, both through the production `AppState::new`.
- **HTTP and Blossom.** `admit_nip_fi_http` keeps Off's result in shadow
and additionally replays enforce in enforce's order: first the router
guard's steps (community, then assertion), then the handler's steps
(NIP-98, pairing, deny set) on the same NIP-98 proof, through
`evaluate_enforce_steps`, which enforce shares. A Host mapped in config
but missing from the communities table, with a valid assertion, records
an admit, because enforce's guard passes and its 404 is not a NIP-FI
denial. A dev-mode `X-Pubkey` identity is marked unsigned and is never
an enforce proof, so shadow records it as a `nip98` would-deny. On
bridge and Blossom routes, the strict proof check (payload tag, Blossom
`Strict`) runs as a separate pure check that consumes no replay entry
and records on its own series, so it never counts as an admission
verdict. Shadow records exactly one verdict for every identity,
community or credential refusal enforce would make, with Off's status,
body and challenge unchanged: bridge, workflows, Blossom, Git transport
and settings, GIF search and share, and invite minting record the
`community` would-deny when the Host is unmapped. Git's missing or
malformed credentials still reject before any database work, and shadow
records the enforce verdict for that failed proof. The router guard
stays transparent in shadow.
- **WebSocket, root and audio.** The upgrade check evaluates the
attached assertion once. An upgrade enforce would refuse records that
would-deny; otherwise the assertion goes into a shadow-only session
object and the upgrade returns as in Off. The assertion never reaches
the connection, the identity registries, the admission gate, terminal
frames or cancellation. Each session records at most one admission
verdict. **Pairing** is recorded on both ingresses right after a valid
NIP-42 proof, before ordinary relay policy, where enforce pairs: a key
mismatch or claimless assertion is a `pairing` denial. **The deny-set
check** runs where enforce runs it, after registration: a hit is a
`deny_set` denial, and a clean read keeps the session pending and
registered. **The admit** is recorded only when the connection is
actually admitted: on root at the AUTH commit, after ordinary policy; on
audio when the participant join transaction commits, after relay
membership, channel membership, the final ban and membership decision,
mesh routing and the join's own checks, and before publication. A NIP-42
failure, which comes before pairing, and any refusal between pairing and
the admit (ordinary policy, mesh, or a join refusal inside the join
transaction) retires the observer when the refusal is decided, before
any refusal frame, rollback or cleanup is awaited, so it leaves no
record even if the deadline passes during that cleanup. A record-only
deadline task, armed at upgrade with enforce's
`compute_session_deadline`, records `expired` when enforce would have
closed an admitted session. If the deadline passes while the session is
still pending, that is its single admission verdict, a denial with
`stage=deadline`, and a later AUTH records nothing. A deny for the key
(admin or cross-pod) records `revoked` on an admitted session; if it
arrives after the deny-set check but before the admit, including a deny
refused for capacity, the session keeps a pending-revocation mark and
records the admit followed by exactly one `revoked` end, matching
enforce's phase-independent close, and the deadline cannot take that
end. The phase, the mark and retirement change together under one
session lock. Each session records at most one end. The session holds
the socket's cancellation token for recording only: once the socket is
cancelled, no transition records anything, even while connection
references remain (a cancel fence; the token never feeds a close
action). Upgrade would-denies carry the ingress route, `ws` or `audio`.
- **Admin disconnect.** Shadow verifies the command and records the deny
entry, so later admissions record would-denies, but closes no session;
the response stays `{"disconnected": true}`. Shadow publishes cross-pod
on its own channel, `buzz:nip-fi:shadow-disconnect`, which only shadow
pods subscribe to, so no enforce pod (including older builds that know
only `buzz:nip-fi:disconnect`) acts on a shadow command. Shadow pods
also keep listening on `buzz:nip-fi:disconnect`, so their deny record
includes enforce's real disconnects. Shadow claims command replays under
`buzz:nip-fi:shadow-command:{hash}`: replays are still rejected within
shadow, and a shadow accept never uses up the enforce claim. Enforce and
Off keep the same channel, keys and close behavior.
- **NIP-11.** Shadow serves the same document as enforce, including
`limitation.federated_identity`, because clients only attach evidence to
a relay that advertises it.

## Recording

| Series | Labels | One increment per |
|---|---|---|
| `buzz_nip_fi_shadow_total` | `route` (`http`, `ws`, `audio`), `stage`,
`outcome`, `community` | decision enforce would make: an HTTP admission,
a refused upgrade, a session's NIP-FI AUTH decision, or its deadline
passing before AUTH (`stage=deadline`) |
| `buzz_nip_fi_shadow_strict_proof_total` | `route` (`bridge`,
`blossom`), `outcome` (`pass`, `rejected`), `community` | strict NIP-98
side check |
| `buzz_nip_fi_shadow_session_end_total` | `route` (`ws`, `audio`),
`reason` (`expired`, `revoked`), `community` | admitted session enforce
would have ended (admitted sessions only) |
| `buzz_nip_fi_shadow_disconnect_total` | `route` (`admin`,
`cross_pod`), `outcome` | disconnect-path event, in place of the real
disconnect, lag, capacity and poison counters |

`community` is the configured canonical URI or `unmapped`, never the raw
`Host`; an unmapped or empty Host records `stage=community,
outcome=unavailable`. A shadow pod never moves an enforce disconnect or
failure counter. Strict-proof rates use their own `pass + rejected`
total, and session-end rates divide by the `admit` count for the same
route. There is no per-verdict `info` log; a would-deny writes a `debug`
line with no token, claim or issuer. The pre-existing enforce `debug`
line for the proven NIP-98 key is shared and also fires in shadow. Admin
commands rejected for a bad header, body or proof, a replay, or a
dependency error record no shadow verdict; only capacity rejection is
counted.

## Not observed

- Handler-side path-validation exits: an invalid Git owner or repo name
on default-branch, a media path that is not a valid hash, and a Git pack
URL with a query string record nothing from the handler. The router
guard still records what enforce would refuse at the guard (for example
a missing assertion), because enforce refuses those requests before it
validates the path.
- A refusal that is not a NIP-FI decision, such as a tenant-binding 404
behind a passing guard, or an ordinary WebSocket refusal after pairing
(a ban, membership or join refusal before admission).

## Follow-ups

- A bounded `route` label per HTTP surface (bridge, Blossom, Git, …) on
`buzz_nip_fi_shadow_total`; today every HTTP verdict carries
`route=http`.
- One shared helper for the ten copied `observe_unbound` recording
hooks, stacked on this PR.

The shadow recorder and session suites and the root pairing witness run
in `just test-unit` and the `scripts/run-tests.sh` fallback; the
`AppState::new` shadow witness, which exercises the command verifier
against real Redis, runs in the `external_infra_redis` lane. NIP-FI env
tests recover a poisoned env lock so one panic cannot cascade.

---------

Signed-off-by: Will Pfleger <pfleger.will@gmail.com>
Signed-off-by: Will Pfleger <wpfleger@block.xyz>
Signed-off-by: Duncan <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>
Signed-off-by: Hayt <211b96e6a2b7f45fd4047988976c7bbbeeda0c15f3ae7b32eec20834b5a55118@buzz.block.builderlab.xyz>
Co-authored-by: Duncan <dcfd242e557282d7a1e2cf2e6877522682f1e5c6156dc92ca7d90eaedd3b0f95@buzz.block.builderlab.xyz>
Co-authored-by: Hayt <211b96e6a2b7f45fd4047988976c7bbbeeda0c15f3ae7b32eec20834b5a55118@buzz.block.builderlab.xyz>
2026-10-02 18:32:17 -04:00
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