security(ruview-swarm): fail-closed on NaN/Inf at the swarm-comm trust boundary + ADR-176 (#1096)

* fix(ruview-swarm): fail-closed on NaN/Inf at swarm-comm trust boundary (ADR-148)

Beyond-SOTA security review of the ADR-148 drone swarm control plane found
four IEEE-754 NaN/Inf fail-open / DoS bugs on data crossing the untrusted
swarm-comm boundary (receive_peer_state / receive_peer_detection accept full
DroneState/CsiDetection whose f64/f32 fields deserialize with no finite-check).

- HIGH: failsafe::tick collision-avoidance + battery checks fail-open on NaN
  (NaN < threshold == false silently disabled collision avoidance / kept a
  NaN-battery drone Nominal). Now fails closed to EmergencyDiverge / RTH.
- MED: geofence::check NaN-altitude bypass returned Safe through the
  point-in-polygon path. Now leading non-finite-coordinate guard -> HardBreach.
- MED/DoS: antijamming FhssRadio panicked with "% 0" on an empty deserialized
  channels_mhz. Now len==0 early-returns (benign 0.0 sentinel).
- LOW: multiview::fuse propagated a NaN victim_position into the fused
  "confirmed victim" location. Now requires finite confidence + position.

Each fix pinned by a fails-on-old / passes-on-new test (MEASURED: old code
returned Nominal/Safe or panicked). cargo test -p ruview-swarm
--no-default-features: 117 -> 123 passed, 0 failed. Workspace green; Python
deterministic proof unchanged (f8e76f21...46f7a, off the signal path).

Documented-not-fixed (ADR slot 176): Raft AppendEntries lacks Log-Matching
consistency check (topology/raft.rs); MavlinkSigner::verify uses non-constant
-time tag compare + no replay-window rejection (already doc-flagged).

Co-Authored-By: claude-flow <ruv@ruv.net>

* docs(adr): ADR-176 — ruview-swarm NaN-fail-open safety review

Records the 4 MEASURED fail-open safety bugs fixed in f671000d7 (collision
avoidance, battery RTH, geofence, anti-jamming %0 panic — all NaN/Inf
defeating a safety comparison at the swarm-comm trust boundary) + 6 pins,
5 clean-with-evidence dimensions, and the 2 genuine issues deferred to a
focused follow-up (Raft AppendEntries log-matching; MAVLink signer
constant-time + replay window).

Co-Authored-By: claude-flow <ruv@ruv.net>

docs/adr/ADR-176-ruview-swarm-nan-fail-open-safety-review.md

@@ -0,0 +1,103 @@
+# ADR-176: `ruview-swarm` NaN-Fail-Open Safety Review
+
+| Field | Value |
+|-------|-------|
+| **Status** | Accepted — 4 real safety bugs fixed + pinned; 2 issues documented for follow-up |
+| **Date** | 2026-06-15 |
+| **Deciders** | ruv |
+| **Codename** | **SWARM-FAILCLOSED** |
+| **Reviews** | ADR-148 (`ruview-swarm` drone swarm control plane) |
+| **Milestone** | #9 (ungated-crate security sweep) — crate 1 of 4 |
+
+## Context
+
+`ruview-swarm` (ADR-148) is the drone swarm control plane — hierarchical-mesh
+topology, Raft consensus, MARL, CSI sensing payload, MAVLink/PX4 command
+dispatch. It is the highest-stakes of the four never-reviewed v2 crates: a defect
+here can produce an **unsafe physical drone command**. It had no prior security
+ADR.
+
+### Trust-boundary map
+Untrusted input enters via `SwarmOrchestrator::receive_peer_state` /
+`receive_peer_detection`, which accept full `DroneState` / `CsiDetection` serde
+structs with **f64/f32 fields and no finite-check**, and via
+`SwarmConfig`/`FhssConfig`/`Geofence` deserialization. The MAVLink wire formats in
+`mavlink_messages.rs` are **integer-encoded** (i32 mm / u8) and provably cannot
+carry NaN — so the NaN class is reachable through the **serde struct path, not the
+MAVLink decode path**. Commands flow out to a `FlightController` (PX4/ArduPilot).
+
+The unifying bug class found: **IEEE-754 NaN/Inf silently defeating a safety
+comparison** (`NaN < threshold` evaluates to `false`), causing safety logic to
+**fail OPEN**. This is distinct from — but rhymes with — the NaN-state-poisoning
+class found earlier in calibration/vitals/geo (there, NaN latched into persistent
+state; here, NaN slips through a one-shot guard). Both are "non-finite input
+defeats logic," and the fix discipline is the same: **reject non-finite at the
+trust boundary, fail CLOSED.**
+
+## Decision
+
+Fix the four reachable fail-open bugs by making each safety predicate
+non-finite-aware and fail-closed, each pinned by a fails-on-old test. Document
+two further genuine issues that need larger, riskier changes rather than churning
+them in a security pass.
+
+### Findings fixed (all MEASURED fails-on-old)
+
+| # | Severity | File:line | Issue | Fix | Pin (old behavior) |
+|---|----------|-----------|-------|-----|--------------------|
+| F1a | **HIGH** | `failsafe/mod.rs:51` | `nearest_neighbor_dist < collision_dist_m` fails open on a NaN peer position → **collision avoidance silently disabled** | `!is_finite() ||` → `EmergencyDiverge` | `test_nan_neighbor_distance_fails_closed_to_diverge` (old → `Nominal`) |
+| F1b | **HIGH** | `failsafe/mod.rs:75` | NaN `battery_pct` bypasses every battery check → drone stays Nominal on unknown battery | `!is_finite() ||` → `ReturnToHome` | `test_nan_battery_fails_closed_to_rth` (old → `Nominal`) |
+| F2 | **MEDIUM** | `security/geofence.rs:33` | NaN `z` altitude skips the altitude-breach check and point-in-polygon returns `Safe` → silent geofence bypass | leading non-finite coord → `HardBreach` | `test_nan_altitude_fails_closed` (old → `Safe`) |
+| F3 | **MEDIUM/DoS** | `security/antijamming.rs:65,71,102` | empty deserialized `channels_mhz` → `% 0` **panic** in `next_hop`/`current_channel_mhz`/`evasive_hop`/`tick`, crashing the radio task | `len == 0` early-return (`0.0` sentinel) | `test_empty_channels_does_not_panic` (old → panic `divisor of zero`) |
+| F4 | **LOW** | `sensing/multiview.rs:70` | NaN `victim_position` passes the `is_some()` filter and propagates into the fused "confirmed victim" location dispatched to the swarm | require finite confidence + position (drop) | `test_nan_victim_position_dropped_from_fusion` (old → non-finite fused position) |
+
+### Dimensions confirmed clean (with evidence)
+- **MAVLink decode panic-safety** — `SwarmNodeState::decode(&[u8;20])` `try_into().unwrap()`s are over fixed const ranges of a fixed-size array → provably infallible; no arbitrary-length `&[u8]` decode path exists.
+- **UWB/GPS anti-spoofing NaN-safe** — `(gps_dist - uwb_dist).abs() <= tol` already fails CLOSED on a NaN range (counts as inconsistent → spoof rejected); covered by `test_spoofed_gps_invalid`.
+- **Bounded grid / no allocate-from-length-field** — `ProbabilityGrid` bounds-checks `cx/cy`; `pos_to_cell` uses saturating `as u32` (no UB).
+- **Mesh `nearest_k` NaN-safe sort** — `partial_cmp(..).unwrap_or(Equal)` cannot panic on NaN.
+- **No hardcoded secrets** — `MavlinkSigner` key is constructor-injected `[u8;32]`; grep-confirmed nothing embedded.
+
+### Documented, not fixed (genuine — deferred to avoid churn/regression risk)
+
+1. **Raft `AppendEntries` lacks the Log-Matching consistency check**
+   (`topology/raft.rs:187`). A follower appends a leader's entries when
+   `term >= current_term` **without validating `prev_log_index`/`prev_log_term`**,
+   so a malformed/byzantine leader can corrupt a follower's log — a genuine
+   consensus-safety gap. A correct fix reworks the log-append plus the
+   caller-side vote-tally contract (the existing `handle_message` delegates
+   tallying to the caller) — a larger change with test-rewrite risk, so it is
+   recorded here rather than rushed in a security pass.
+2. **`MavlinkSigner::verify` uses a non-constant-time tag `==` and has no
+   replay/timestamp-window rejection** (`security/mavlink_signing.rs:64`). The
+   module doc already flags the replay limitation as a demo/test simplification.
+   Hardening (constant-time compare + monotonic timestamp window) is a focused
+   follow-up.
+
+These two are the recommended scope of the next `ruview-swarm` hardening pass.
+
+## Validation
+
+- `cargo test -p ruview-swarm --no-default-features` → **117 → 123** passed, 0 failed (+6 pins).
+- All 6 new tests MEASURED fails-on-old (2× `Nominal`, `Safe`, panic `divisor of zero`, non-finite fused position); pass on the fix.
+- `cargo test --workspace --no-default-features` → **exit 0**, 0 failed.
+- `python archive/v1/data/proof/verify.py` → **VERDICT: PASS**, hash
+  `f8e76f21…46f7a` unchanged (ruview-swarm off the signal proof path).
+
+## Consequences
+
+### Positive
+- Four reachable fail-open paths in a *physical-safety* control plane (collision
+  avoidance, battery RTH, geofence, anti-jamming radio task) now fail CLOSED on
+  hostile/degenerate input, each regression-pinned.
+- Extends the "non-finite input defeats logic" defense from the state-poisoning
+  variant (calibration/vitals/geo) to the fail-open-comparison variant.
+
+### Negative / Neutral
+- Two genuine issues (Raft log-matching, MAVLink signer) remain open by choice —
+  see Documented-not-fixed; they define the next hardening pass.
+
+## Links
+- ADR-148 — `ruview-swarm` drone swarm control system
+- ADR-172 — core/cli review (where the NaN bug-class root question was settled NO)
+- ADR-127 — homecore review (sibling NaN/concurrency hardening)