fix(bfld security): close HIGH privacy-bypass in process_to_frame (identity surface leaked despite restrictive class) + JSON-injection (#1075)

* fix(bfld): route process_to_frame payload through PrivacyGate (ADR-141 privacy bypass)

BfldPipeline::process_to_frame stamped the frame header with the active
privacy class but serialized the caller-supplied BfldPayload UNCHANGED via
BfldFrame::from_payload. This let a frame labeled Anonymous(2) or
Restricted(3) carry the full identity-leaky compressed_angle_matrix
(+ amplitude/phase proxies, csi_delta) that PrivacyGate::demote is documented
and tested (privacy_gate_demote.rs) to strip at exactly those classes.

A NetworkSink accepts class >= Derived(1), so such a frame would publish the
beamforming angle matrix — the identity surface — across the node boundary
despite its restrictive class byte. The class byte lied about payload content.

Fix: after building the frame at the active class, apply PrivacyGate::demote to
the same class. demote() strips sections by target-class threshold (independent
of any class transition), so a same-class demote performs no class change but
brings the payload into policy compliance. Research classes (Raw/Derived) keep
the full payload — demote is a no-op there.

Pinned by three fails-on-old tests in pipeline_to_frame.rs:
- process_to_frame_at_anonymous_strips_identity_leaky_sections (FAILED pre-fix)
- process_to_frame_in_privacy_mode_strips_amplitude_and_phase (FAILED pre-fix)
- process_to_frame_at_derived_preserves_full_payload (guards against over-strip)
The pre-existing round-trip test is updated to assert the gated payload.

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

* fix(bfld): JSON-escape zone_id in MQTT state-topic payload

render_events emitted the zone_activity payload as format!("\"{zone}\"") with no
escaping, while ha_discovery.rs already escapes operator-controlled strings via
push_str_field. A zone name containing a double-quote or backslash therefore
produced malformed / injectable JSON on the state topic that Home Assistant
parses (e.g. zone `a"b` -> payload `"a"b"`).

Fix: add json_string_literal() mirroring ha_discovery's escaping (", \, \n, \r,
\t, control chars) and use it for the zone payload. Value-identical for normal
zone names (living_room etc.).

Pinned by zone_payload_escapes_json_metacharacters (FAILED pre-fix); the
existing zone_payload_is_json_string_with_quotes still passes unchanged.

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

* docs(adr-141): record bfld privacy+security review findings + CHANGELOG

Document the two fixed bugs (process_to_frame privacy-bypass; zone_id JSON
injection) and the dimensions confirmed clean (event-field gating, witness/hash
framing, fail-closed) in ADR-141, plus CHANGELOG [Unreleased] Security/Fixed
entries.

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

v2/crates/wifi-densepose-bfld/src/mqtt_topics.rs

@@ -135,10 +135,13 @@ pub fn render_events(event: &BfldEvent) -> Vec<TopicMessage> {
 
     if let Some(zone) = &event.zone_id {
         // Emit a JSON string so consumers can distinguish "no zone" (omitted)
-        // from "single-zone deployment" (always the same zone string).
+        // from "single-zone deployment" (always the same zone string). The zone
+        // name is operator-controlled; escape JSON metacharacters so a name
+        // containing a quote or backslash cannot produce malformed/injected
+        // JSON. Mirrors ha_discovery.rs::push_str_field's escaping.
         out.push(TopicMessage {
             topic: TopicMessage::ruview_topic(node, "zone_activity"),
-            payload: format!("\"{zone}\""),
+            payload: json_string_literal(zone),
         });
     }
 
@@ -155,3 +158,26 @@ pub fn render_events(event: &BfldEvent) -> Vec<TopicMessage> {
 
     out
 }
+
+/// Wrap `value` in JSON double-quote delimiters, escaping the metacharacters
+/// that would otherwise break out of the string literal (`"`, `\`, control
+/// chars, and the bare `\n`/`\r`/`\t` whitespace). Kept in lockstep with
+/// `ha_discovery::push_str_field` so state-topic and discovery payloads escape
+/// identically.
+fn json_string_literal(value: &str) -> String {
+    let mut out = String::with_capacity(value.len() + 2);
+    out.push('"');
+    for ch in value.chars() {
+        match ch {
+            '"' => out.push_str("\\\""),
+            '\\' => out.push_str("\\\\"),
+            '\n' => out.push_str("\\n"),
+            '\r' => out.push_str("\\r"),
+            '\t' => out.push_str("\\t"),
+            c if (c as u32) < 0x20 => out.push_str(&format!("\\u{:04x}", c as u32)),
+            c => out.push(c),
+        }
+    }
+    out.push('"');
+    out
+}

v2/crates/wifi-densepose-bfld/src/pipeline.rs

@@ -141,6 +141,15 @@ impl BfldPipeline {
     /// builds the frame via [`BfldFrame::from_payload`] so the CRC covers the
     /// section-prefixed bytes.
     ///
+    /// The emitted frame's payload is forced into compliance with the active
+    /// privacy class via [`crate::PrivacyGate::demote`]: at `Anonymous` the
+    /// identity-leaky `compressed_angle_matrix` and `csi_delta` sections are
+    /// stripped, and at `Restricted` the amplitude/phase proxies are stripped
+    /// too. This closes the gap (ADR-141) where a frame stamped with a
+    /// restrictive class byte could otherwise carry the full high-information
+    /// BFI payload across a [`crate::NetworkSink`]. Research classes (`Raw`,
+    /// `Derived`) keep the full payload — `demote` is a no-op there.
+    ///
     /// Returns `None` whenever the gate drops the underlying event (Reject or
     /// Recalibrate), so `process_to_frame` is a strict subset of `process`.
     pub fn process_to_frame(
@@ -151,11 +160,21 @@ impl BfldPipeline {
         embedding: Option<IdentityEmbedding>,
     ) -> Option<BfldFrame> {
         let timestamp_ns = inputs.timestamp_ns;
+        let active_class = self.current_privacy_class();
         let _gate_signal = self.process(inputs, embedding)?;
         let mut header = header_template;
         header.timestamp_ns = timestamp_ns;
-        header.privacy_class = self.current_privacy_class().as_u8();
-        Some(BfldFrame::from_payload(header, &payload))
+        header.privacy_class = active_class.as_u8();
+        let frame = BfldFrame::from_payload(header, &payload);
+        // Enforce the payload-content policy for the stamped class. The frame
+        // is already at `active_class`, so this is a same-class demotion: it
+        // performs no class change but strips the sections that class forbids.
+        // demote() only fails on InvalidDemote (target < source), which cannot
+        // happen here because source == target, so the expect is unreachable.
+        Some(
+            crate::PrivacyGate::demote(frame, active_class)
+                .expect("same-class demote is always valid"),
+        )
     }
 
     /// `true` if `enable_privacy_mode()` has been called more recently than

v2/crates/wifi-densepose-bfld/tests/mqtt_topic_routing.rs

@@ -127,6 +127,38 @@ fn zone_payload_is_json_string_with_quotes() {
     assert_eq!(zone.payload, "\"living_room\"");
 }
 
+#[test]
+fn zone_payload_escapes_json_metacharacters() {
+    // A zone name containing a double-quote or backslash must not break out of
+    // the JSON string literal it is emitted into. ha_discovery.rs already
+    // escapes operator-controlled strings via push_str_field; render_events
+    // must do the same for parity so the state-topic payload is always valid
+    // JSON that Home Assistant can parse.
+    let ev = BfldEvent::with_privacy_gating(
+        "seed-01".into(),
+        0,
+        true,
+        0.1,
+        1,
+        0.9,
+        Some(r#"living"room\back"#.into()),
+        PrivacyClass::Anonymous,
+        None,
+        None,
+    );
+    let msgs = render_events(&ev);
+    let zone = msgs
+        .iter()
+        .find(|m| m.topic.contains("zone_activity"))
+        .expect("zone_activity topic");
+    // Expected: the inner quote and backslash are backslash-escaped, wrapped in
+    // one pair of unescaped delimiter quotes -> a single valid JSON string.
+    assert_eq!(zone.payload, r#""living\"room\\back""#);
+    // And it must parse as JSON back to the original zone string.
+    let parsed: String = serde_json::from_str(&zone.payload).expect("valid JSON string");
+    assert_eq!(parsed, r#"living"room\back"#);
+}
+
 #[test]
 fn identity_risk_payload_is_fixed_precision_decimal() {
     let msgs = render_events(&sample_event(PrivacyClass::Anonymous, false));

v2/crates/wifi-densepose-bfld/tests/pipeline_to_frame.rs

@@ -88,6 +88,11 @@ fn process_to_frame_returns_none_under_sustained_high_risk() {
 
 #[test]
 fn process_to_frame_round_trips_through_bytes() {
+    // Default pipeline class is Anonymous(2). The frame must round-trip through
+    // wire bytes with no CRC error; the payload it carries is the privacy-gated
+    // (angle-matrix-stripped) form, not the raw input — see
+    // process_to_frame_at_anonymous_strips_identity_leaky_sections for the
+    // content assertion. This test pins byte/CRC consistency only.
     let mut p = BfldPipeline::new(BfldConfig::new("seed-01"));
     let frame = p
         .process_to_frame(
@@ -100,7 +105,10 @@ fn process_to_frame_round_trips_through_bytes() {
     let bytes = frame.to_bytes();
     let parsed = BfldFrame::from_bytes(&bytes).expect("frame must round-trip");
     let parsed_payload = parsed.parse_payload().expect("payload must round-trip");
-    assert_eq!(parsed_payload, typed_payload());
+    // Round-trip preserves whatever the privacy gate left in place.
+    assert_eq!(parsed_payload, frame.parse_payload().unwrap());
+    // And the identity surface is gone at Anonymous.
+    assert!(parsed_payload.compressed_angle_matrix.is_empty());
 }
 
 #[test]
@@ -141,6 +149,94 @@ fn process_to_frame_preserves_header_template_identity_fields() {
     assert_eq!({ frame.header.channel }, 36);
 }
 
+// --- ADR-141 privacy-gate-correctness regression -------------------------
+//
+// `process_to_frame` stamps the frame with the pipeline's privacy_class but
+// (pre-fix) serialized the caller-supplied payload UNCHANGED. That let a frame
+// labeled Anonymous(2) / Restricted(3) carry the full identity-leaky
+// `compressed_angle_matrix` (+ amplitude/phase/csi_delta) that
+// `PrivacyGate::demote` is documented (privacy_gate_demote.rs) to strip at
+// exactly those classes. A NetworkSink accepts class >= Derived, so such a
+// frame would publish the beamforming angle matrix (identity surface) to the
+// network despite its restrictive class byte. These tests pin that the payload
+// content matches what the stamped class permits.
+
+#[test]
+fn process_to_frame_at_anonymous_strips_identity_leaky_sections() {
+    // Default pipeline class is Anonymous(2): the angle matrix and csi_delta
+    // MUST NOT survive into the emitted frame, matching PrivacyGate::demote.
+    let mut p = BfldPipeline::new(BfldConfig::new("seed-01"));
+    let mut leaky = typed_payload();
+    leaky.csi_delta = Some(vec![0x55; 24]);
+    let frame = p
+        .process_to_frame(
+            inputs(1_700_000_000_000_000_000, [0.1, 0.1, 0.1, 0.1]),
+            header_template(),
+            leaky,
+            Some(embedding()),
+        )
+        .expect("low-risk frame must be emitted");
+    assert_eq!({ frame.header.privacy_class }, PrivacyClass::Anonymous.as_u8());
+    let payload = frame.parse_payload().expect("payload parses");
+    assert!(
+        payload.compressed_angle_matrix.is_empty(),
+        "Anonymous frame must NOT carry the compressed_angle_matrix (identity surface)",
+    );
+    assert!(
+        payload.csi_delta.is_none(),
+        "Anonymous frame must NOT carry csi_delta",
+    );
+    // Aggregate sensing sections survive.
+    assert_eq!(payload.snr_vector.len(), 8);
+    assert_eq!(payload.amplitude_proxy.len(), 16);
+}
+
+#[test]
+fn process_to_frame_in_privacy_mode_strips_amplitude_and_phase() {
+    // privacy_mode -> Restricted(3): amplitude + phase proxies must ALSO drop.
+    let mut p = BfldPipeline::new(
+        BfldConfig::new("seed-01").with_privacy_class(PrivacyClass::Anonymous),
+    );
+    p.enable_privacy_mode();
+    let frame = p
+        .process_to_frame(
+            inputs(0, [0.1, 0.1, 0.1, 0.1]),
+            header_template(),
+            typed_payload(),
+            Some(embedding()),
+        )
+        .expect("frame emitted");
+    assert_eq!({ frame.header.privacy_class }, PrivacyClass::Restricted.as_u8());
+    let payload = frame.parse_payload().expect("payload parses");
+    assert!(payload.compressed_angle_matrix.is_empty(), "angle matrix stripped at Restricted");
+    assert!(payload.amplitude_proxy.is_empty(), "amplitude stripped at Restricted");
+    assert!(payload.phase_proxy.is_empty(), "phase stripped at Restricted");
+    assert_eq!(payload.snr_vector.len(), 8, "snr_vector survives");
+}
+
+#[test]
+fn process_to_frame_at_derived_preserves_full_payload() {
+    // Derived(1) is a research mode that legitimately keeps the angle matrix.
+    // The strip must NOT over-fire at classes below Anonymous.
+    let mut p = BfldPipeline::new(
+        BfldConfig::new("seed-01").with_privacy_class(PrivacyClass::Derived),
+    );
+    let frame = p
+        .process_to_frame(
+            inputs(0, [0.1, 0.1, 0.1, 0.1]),
+            header_template(),
+            typed_payload(),
+            Some(embedding()),
+        )
+        .expect("frame emitted");
+    assert_eq!({ frame.header.privacy_class }, PrivacyClass::Derived.as_u8());
+    let payload = frame.parse_payload().expect("payload parses");
+    assert_eq!(
+        payload, typed_payload(),
+        "Derived research frame keeps the full payload unchanged",
+    );
+}
+
 #[test]
 fn process_to_frame_uses_input_timestamp_not_template_timestamp() {
     let mut p = BfldPipeline::new(BfldConfig::new("seed-01"));