feat(pairing): delegated approval (§8b-1) — approve an unpaired device from the console

An identified-but-unpaired device that knocks on a pairing-required host is now held as a pending request the operator approves from the web console — pairing it with no PIN fetched out of band — instead of a flat reject. - core: Hello gains an optional trailing device name (len u8 || UTF-8, ≤64, same trailing-back-compat pattern as compositor/gamepad/bitrate). client-rs --name sends it; the connector sends None (fingerprint-derived label). - native_pairing: in-memory pending queue (note_pending dedups by fingerprint, evicts the least-recently-active past a 32 cap, 10-min TTL); approve_pending pins the fingerprint, deny drops it. Names are sanitized (strip control/ANSI/ bidi — untrusted wire input); add()/remove() roll back in-memory on a persist failure; pairing clears any stale pending knock. - m3: the require_pairing gate records the knock (sanitized label) before rejecting; anonymous (certless) clients record nothing. - mgmt: GET /native/pending, POST /native/pending/{id}/approve (optional {name}) and /deny; OpenAPI + tests; docs/api/openapi.json regenerated. - web: a "Waiting for approval" section on the Pairing page (live-poll, Approve/ Deny, error-surfaced via QueryState); en+de strings. - Also completes an in-progress NativeClient Sync refactor (receivers behind per-plane mutexes) that was left half-applied in the tree. Adversarially reviewed (4 lenses + 3-vote verify); the confirmed findings are fixed here. Validated live on the GNOME box: knock (with a wire name, and a malicious ANSI/bidi name that got neutralized) → pending → approve → the same identity streams real video. Full workspace tests + clippy + fmt green; web tsc clean. Roadmap §8b-1 marked done; §8b-2 (peer-push approval) is the client follow-up. See docs-site pairing page. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-12 19:14:05 +00:00
parent 9758751a4d
commit 99b4de32ee
14 changed files with 1250 additions and 109 deletions
@@ -454,13 +454,34 @@ async fn serve_session(
            punktfunk_core::ABI_VERSION
        );
        if opts.require_pairing {
-            let known = endpoint::peer_fingerprint(&conn)
-                .map(|fp| np.is_paired(&fingerprint_hex(&fp)))
+            let fp = endpoint::peer_fingerprint(&conn);
+            let known = fp
+                .as_ref()
+                .map(|fp| np.is_paired(&fingerprint_hex(fp)))
                .unwrap_or(false);
-            anyhow::ensure!(
-                known,
-                "unpaired client rejected (this host requires pairing — run the PIN ceremony first)"
-            );
+            if !known {
+                // Delegated approval (§8b-1): an identified-but-unpaired knock becomes a pending
+                // request the operator can approve from the console — no PIN fetched out of band.
+                // The label is the client's Hello name, else fingerprint-derived. An anonymous
+                // client (no certificate) has no identity to approve, so nothing is recorded.
+                if let Some(fp) = &fp {
+                    let fp_hex = fingerprint_hex(fp);
+                    // Sanitize the wire-supplied name before it reaches the log (untrusted: an
+                    // unpaired device could embed terminal escapes / bidi overrides); note_pending
+                    // stores the same sanitized form and derives a fingerprint label when empty.
+                    let label = crate::native_pairing::sanitize_device_name(
+                        hello.name.as_deref().unwrap_or(""),
+                        &fp_hex,
+                    );
+                    tracing::info!(name = %label, fingerprint = %fp_hex,
+                        "unpaired device knocked — held for approval in the console");
+                    np.note_pending(&label, &fp_hex);
+                }
+                anyhow::bail!(
+                    "unpaired client rejected (this host requires pairing — approve the device \
+                     in the console, or run the PIN ceremony)"
+                );
+            }
        }
        crate::encode::validate_dimensions(
            crate::encode::Codec::H265,
@@ -2206,6 +2227,100 @@ mod tests {
        std::env::temp_dir().join(format!("punktfunk-paired-test-{}.json", std::process::id()))
    }

+    /// Delegated approval (§8b-1) end to end in-process: an identified-but-unpaired client's
+    /// knock on a pairing-required host is held as a pending request (fingerprint-derived label —
+    /// the connector sends no Hello name); approving it pairs the fingerprint, and the same
+    /// identity then gets a session with no PIN ceremony.
+    #[test]
+    fn delegated_approval_admits_after_knock() {
+        use punktfunk_core::client::NativeClient;
+        use punktfunk_core::quic::endpoint;
+
+        let store =
+            std::env::temp_dir().join(format!("pf-approval-test-{}.json", std::process::id()));
+        let _ = std::fs::remove_file(&store);
+        let np = Arc::new(NativePairing::load_with(Some(store.clone()), None, false).unwrap());
+        let np_host = np.clone();
+        let host = std::thread::spawn(move || {
+            let rt = tokio::runtime::Builder::new_multi_thread()
+                .worker_threads(2)
+                .enable_all()
+                .build()
+                .unwrap();
+            rt.block_on(serve(
+                M3Options {
+                    port: 19779,
+                    source: M3Source::Synthetic,
+                    seconds: 0,
+                    frames: 25,
+                    max_sessions: 2, // the knock + the post-approval session
+                    max_concurrent: 1,
+                    require_pairing: true,
+                    allow_pairing: false,
+                    pairing_pin: None,
+                    paired_store: None, // unused: the shared `np` IS the store handle
+                },
+                np_host,
+            ))
+        });
+        std::thread::sleep(std::time::Duration::from_millis(500));
+        let timeout = std::time::Duration::from_secs(10);
+        let (cert, key) = endpoint::generate_identity().unwrap();
+        let mode = punktfunk_core::Mode {
+            width: 1280,
+            height: 720,
+            refresh_hz: 60,
+        };
+
+        // 1: the knock — an identified-but-unpaired connect is rejected, but lands in pending.
+        assert!(
+            NativeClient::connect(
+                "127.0.0.1",
+                19779,
+                mode,
+                CompositorPref::Auto,
+                GamepadPref::Auto,
+                0,
+                None,
+                Some((cert.clone(), key.clone())),
+                timeout
+            )
+            .is_err(),
+            "unpaired knock must still be rejected"
+        );
+        let expected_fp = fingerprint_hex(&endpoint::fingerprint_of_pem(&cert).unwrap());
+        let pend = np.pending();
+        assert_eq!(pend.len(), 1, "the knock must be held for approval");
+        assert_eq!(pend[0].fingerprint, expected_fp);
+        assert!(
+            pend[0].name.starts_with("device "),
+            "no Hello name → fingerprint-derived label, got {:?}",
+            pend[0].name
+        );
+
+        // 2: approve (with an operator label) → the same identity now gets a session, no PIN.
+        let approved = np
+            .approve_pending(pend[0].id, Some("Approved Device"))
+            .unwrap()
+            .expect("pending id must approve");
+        assert_eq!(approved.fingerprint, expected_fp);
+        let client = NativeClient::connect(
+            "127.0.0.1",
+            19779,
+            mode,
+            CompositorPref::Auto,
+            GamepadPref::Auto,
+            0,
+            None,
+            Some((cert, key)),
+            timeout,
+        )
+        .expect("approved identity gets a session");
+        drop(client);
+        let _ = std::fs::remove_file(&store);
+        host.join().unwrap().unwrap();
+    }
+
    /// The PIN pairing ceremony + the --require-pairing gate, end to end in-process:
    /// wrong PIN rejected; right PIN pairs and returns the host fingerprint; a paired
    /// identity gets a session on a pairing-required host; an anonymous client does not.
@@ -145,6 +145,9 @@ fn api_router_parts() -> (Router<Arc<MgmtState>>, utoipa::openapi::OpenApi) {
                .routes(routes!(disarm_native_pairing))
                .routes(routes!(list_native_clients))
                .routes(routes!(unpair_native_client))
+                .routes(routes!(list_pending_devices))
+                .routes(routes!(approve_pending_device))
+                .routes(routes!(deny_pending_device))
                .routes(routes!(stop_session))
                .routes(routes!(request_idr)),
        )
@@ -379,6 +382,29 @@ struct NativeClient {
    fingerprint: String,
 }

+/// An unpaired device that tried to connect while the host requires pairing — awaiting
+/// **delegated approval** (approve it here instead of fetching the host PIN out of band).
+#[derive(Serialize, ToSchema)]
+struct PendingDevice {
+    /// Id to address approve/deny (per-process; entries expire after ~10 minutes).
+    id: u32,
+    /// Best-effort device label (the client's own name, else fingerprint-derived).
+    #[schema(example = "Enrico's MacBook")]
+    name: String,
+    /// Hex SHA-256 of the device's certificate — what approval pins.
+    fingerprint: String,
+    /// Seconds since the device last knocked.
+    age_secs: u64,
+}
+
+/// Approve-pending-device request body. Send `{}` to keep the device's own name.
+#[derive(Deserialize, ToSchema)]
+struct ApprovePending {
+    /// Operator-chosen label for the device (defaults to the name it knocked with).
+    #[schema(example = "Living Room TV")]
+    name: Option<String>,
+}
+
 /// Error envelope for every non-2xx response.
 #[derive(Serialize, Deserialize, ToSchema)]
 struct ApiError {
@@ -885,6 +911,116 @@ async fn unpair_native_client(
    }
 }

+/// List devices awaiting pairing approval
+///
+/// Unpaired devices that tried to connect while the host requires pairing. Approve one to pair
+/// it without a PIN (delegated approval); entries expire after ~10 minutes.
+#[utoipa::path(
+    get,
+    path = "/native/pending",
+    tag = "native",
+    operation_id = "listPendingDevices",
+    responses(
+        (status = OK, description = "Devices awaiting approval (empty when none, or when the \
+                                     native host is not enabled)", body = Vec<PendingDevice>),
+        (status = UNAUTHORIZED, description = "Missing or invalid bearer token", body = ApiError),
+    )
+)]
+async fn list_pending_devices(State(st): State<Arc<MgmtState>>) -> Json<Vec<PendingDevice>> {
+    let pending = st
+        .native
+        .as_ref()
+        .map(|np| np.pending())
+        .unwrap_or_default();
+    Json(
+        pending
+            .into_iter()
+            .map(|p| PendingDevice {
+                id: p.id,
+                name: p.name,
+                fingerprint: p.fingerprint,
+                age_secs: p.age_secs,
+            })
+            .collect(),
+    )
+}
+
+/// Approve a pending device
+///
+/// Pairs the device's certificate fingerprint — it can connect immediately (no PIN). Optionally
+/// relabel it via the body; send `{}` to keep the name it knocked with.
+#[utoipa::path(
+    post,
+    path = "/native/pending/{id}/approve",
+    tag = "native",
+    operation_id = "approvePendingDevice",
+    params(("id" = u32, Path, description = "Pending-request id from the pending list")),
+    request_body = ApprovePending,
+    responses(
+        (status = OK, description = "Device paired", body = NativeClient),
+        (status = NOT_FOUND, description = "No pending request with that id (expired?)", body = ApiError),
+        (status = SERVICE_UNAVAILABLE, description = "Native host not enabled", body = ApiError),
+        (status = INTERNAL_SERVER_ERROR, description = "Could not persist the trust store", body = ApiError),
+        (status = UNAUTHORIZED, description = "Missing or invalid bearer token", body = ApiError),
+    )
+)]
+async fn approve_pending_device(
+    State(st): State<Arc<MgmtState>>,
+    Path(id): Path<u32>,
+    ApiJson(req): ApiJson<ApprovePending>,
+) -> Response {
+    let Some(np) = &st.native else {
+        return api_error(StatusCode::SERVICE_UNAVAILABLE, "native host not enabled");
+    };
+    match np.approve_pending(id, req.name.as_deref()) {
+        Ok(Some(client)) => {
+            tracing::info!(name = %client.name, fingerprint = %client.fingerprint,
+                "management API: pending device approved (delegated pairing)");
+            Json(NativeClient {
+                name: client.name,
+                fingerprint: client.fingerprint,
+            })
+            .into_response()
+        }
+        Ok(None) => api_error(
+            StatusCode::NOT_FOUND,
+            "no pending request with that id (it may have expired — have the device retry)",
+        ),
+        Err(e) => api_error(
+            StatusCode::INTERNAL_SERVER_ERROR,
+            &format!("could not persist trust store: {e}"),
+        ),
+    }
+}
+
+/// Deny a pending device
+///
+/// Drops the request. Not a blocklist — the device's next attempt knocks again.
+#[utoipa::path(
+    post,
+    path = "/native/pending/{id}/deny",
+    tag = "native",
+    operation_id = "denyPendingDevice",
+    params(("id" = u32, Path, description = "Pending-request id from the pending list")),
+    responses(
+        (status = NO_CONTENT, description = "Request dropped"),
+        (status = NOT_FOUND, description = "No pending request with that id", body = ApiError),
+        (status = SERVICE_UNAVAILABLE, description = "Native host not enabled", body = ApiError),
+        (status = UNAUTHORIZED, description = "Missing or invalid bearer token", body = ApiError),
+    )
+)]
+async fn deny_pending_device(State(st): State<Arc<MgmtState>>, Path(id): Path<u32>) -> Response {
+    let Some(np) = &st.native else {
+        return api_error(StatusCode::SERVICE_UNAVAILABLE, "native host not enabled");
+    };
+    if np.deny_pending(id) {
+        tracing::info!(id, "management API: pending device denied");
+        StatusCode::NO_CONTENT.into_response()
+    } else {
+        api_error(StatusCode::NOT_FOUND, "no pending request with that id")
+    }
+}
+
 /// Stop the active session
 ///
 /// Kicks the connected client: stops the video/audio stream threads and clears the launch
@@ -1344,6 +1480,77 @@ mod tests {
        assert_eq!(b["armed"], false);
    }

+    #[tokio::test]
+    async fn pending_devices_approve_and_deny() {
+        let np = Arc::new(
+            crate::native_pairing::NativePairing::load_with(
+                Some(
+                    std::env::temp_dir()
+                        .join(format!("pf-mgmt-pending-{}.json", std::process::id())),
+                ),
+                None,
+                false,
+            )
+            .unwrap(),
+        );
+        let app = test_app_native(test_state(), np.clone());
+
+        // Empty queue.
+        let (s, b) = send(&app, get_req("/api/v1/native/pending")).await;
+        assert_eq!(s, StatusCode::OK);
+        assert_eq!(b.as_array().unwrap().len(), 0);
+
+        // Two devices knock (what the QUIC gate records); they appear in the list.
+        np.note_pending("Enrico's MacBook", "aa11");
+        np.note_pending("device bb22cc33", "bb22");
+        let (_, b) = send(&app, get_req("/api/v1/native/pending")).await;
+        assert_eq!(b.as_array().unwrap().len(), 2);
+        assert_eq!(b[0]["name"], "Enrico's MacBook");
+        let approve_id = b[0]["id"].as_u64().unwrap();
+        let deny_id = b[1]["id"].as_u64().unwrap();
+
+        // Approve the first with an operator label → paired under that name, gone from pending.
+        let (s, b) = send(
+            &app,
+            post_json(
+                &format!("/api/v1/native/pending/{approve_id}/approve"),
+                serde_json::json!({"name": "Office MacBook"}),
+            ),
+        )
+        .await;
+        assert_eq!(s, StatusCode::OK);
+        assert_eq!(b["name"], "Office MacBook");
+        assert_eq!(b["fingerprint"], "aa11");
+        assert!(np.is_paired("AA11"), "approval pins the fingerprint");
+
+        // Deny the second → dropped, not paired; a re-deny is 404.
+        let deny = post_json(
+            &format!("/api/v1/native/pending/{deny_id}/deny"),
+            serde_json::json!({}),
+        );
+        assert_eq!(send(&app, deny).await.0, StatusCode::NO_CONTENT);
+        assert!(!np.is_paired("bb22"));
+        let (s, _) = send(
+            &app,
+            post_json(
+                &format!("/api/v1/native/pending/{deny_id}/deny"),
+                serde_json::json!({}),
+            ),
+        )
+        .await;
+        assert_eq!(s, StatusCode::NOT_FOUND);
+
+        // Queue is empty again; approving a stale id is 404 (keep `{}` = device's own name).
+        let (_, b) = send(&app, get_req("/api/v1/native/pending")).await;
+        assert_eq!(b.as_array().unwrap().len(), 0);
+        let (s, _) = send(
+            &app,
+            post_json("/api/v1/native/pending/123/approve", serde_json::json!({})),
+        )
+        .await;
+        assert_eq!(s, StatusCode::NOT_FOUND);
+    }
+
    #[tokio::test]
    async fn native_endpoints_report_disabled_without_native_host() {
        let app = test_app(test_state(), None);
@@ -1357,5 +1564,22 @@ mod tests {
        )
        .await;
        assert_eq!(s, StatusCode::SERVICE_UNAVAILABLE);
+        // Pending list reads as an empty array (like /native/clients), not a 503.
+        let (s, b) = send(&app, get_req("/api/v1/native/pending")).await;
+        assert_eq!(s, StatusCode::OK);
+        assert_eq!(b.as_array().unwrap().len(), 0);
+        // Approve/deny without a native host are 503.
+        let (s, _) = send(
+            &app,
+            post_json("/api/v1/native/pending/0/approve", serde_json::json!({})),
+        )
+        .await;
+        assert_eq!(s, StatusCode::SERVICE_UNAVAILABLE);
+        let (s, _) = send(
+            &app,
+            post_json("/api/v1/native/pending/0/deny", serde_json::json!({})),
+        )
+        .await;
+        assert_eq!(s, StatusCode::SERVICE_UNAVAILABLE);
    }
 }
@@ -47,10 +47,47 @@ struct Armed {
    expires_at: Option<Instant>,
 }

-/// Shared native-pairing state: the arming PIN window + the persistent trust store.
+/// An unpaired (but identified) device that knocked on a pairing-required host — held for
+/// **delegated approval** from the management console (roadmap §8b-1) instead of being silently
+/// forgotten. In-memory only: pending knocks don't survive a restart (the device just knocks
+/// again), and they expire after [`PENDING_TTL`].
+struct Pending {
+    id: u32,
+    name: String,
+    fp_hex: String,
+    requested_at: Instant,
+}
+
+#[derive(Default)]
+struct PendingState {
+    next_id: u32,
+    items: Vec<Pending>,
+}
+
+/// A pending-approval snapshot for the management API / web console.
+pub struct PendingRequest {
+    /// Per-process id used to address approve/deny (stable for the entry's lifetime).
+    pub id: u32,
+    /// Best-effort device label (the client's `Hello` name, else fingerprint-derived).
+    pub name: String,
+    /// Hex SHA-256 of the knocking client's certificate — what approval pins.
+    pub fingerprint: String,
+    /// Seconds since the (most recent) knock.
+    pub age_secs: u64,
+}
+
+/// Pending knocks older than this are dropped (the device retries; a stale entry shouldn't be
+/// approvable days later when the operator no longer remembers the context).
+const PENDING_TTL: Duration = Duration::from_secs(10 * 60);
+/// Cap on the pending list — a LAN scanner must not grow it unboundedly. Oldest entries drop.
+const PENDING_CAP: usize = 32;
+
+/// Shared native-pairing state: the arming PIN window + the persistent trust store + the
+/// pending-approval queue.
 pub struct NativePairing {
    arm: Mutex<Armed>,
    paired: Mutex<PairedState>,
+    pending: Mutex<PendingState>,
 }

 /// A snapshot for the management API / web console.
@@ -92,6 +129,48 @@ fn random_pin() -> String {
    format!("{:04}", rand::thread_rng().gen_range(0..10_000u32))
 }

+/// Sanitize a client-supplied device name before it's stored, listed, or logged. The name comes
+/// straight off the wire (the `Hello`/`PairRequest` of an *unpaired* device), so it's untrusted: a
+/// hostile LAN device could embed terminal escapes / control characters (log + console injection) or
+/// bidi overrides (`U+202E` etc.) to make a malicious device *look* like a trusted one in the
+/// approval UI. Strip C0/C1 controls and Unicode bidi/format controls, collapse whitespace, trim, and
+/// cap the length; an empty/all-control name falls back to a fingerprint-derived label.
+pub(crate) fn sanitize_device_name(name: &str, fp_hex: &str) -> String {
+    let cleaned: String = name
+        .chars()
+        .map(|c| if c == '\t' || c == '\n' { ' ' } else { c })
+        .filter(|&c| {
+            !c.is_control()
+                // Bidi/format controls that could spoof or reorder the displayed name.
+                && !('\u{202A}'..='\u{202E}').contains(&c) // LRE..RLO/PDF
+                && !('\u{2066}'..='\u{2069}').contains(&c) // LRI..PDI
+                && c != '\u{200E}' // LRM
+                && c != '\u{200F}' // RLM
+                && c != '\u{061C}' // ALM
+                && c != '\u{FEFF}' // BOM / zero-width no-break space
+        })
+        .collect();
+    // Collapse internal whitespace runs, trim, cap at the wire limit.
+    let collapsed = cleaned.split_whitespace().collect::<Vec<_>>().join(" ");
+    let mut trimmed = collapsed.as_str();
+    while trimmed.len() > NAME_MAX {
+        let mut cut = NAME_MAX;
+        while !trimmed.is_char_boundary(cut) {
+            cut -= 1;
+        }
+        trimmed = &trimmed[..cut];
+    }
+    let trimmed = trimmed.trim();
+    if trimmed.is_empty() {
+        format!("device {}", &fp_hex[..8.min(fp_hex.len())])
+    } else {
+        trimmed.to_string()
+    }
+}
+
+/// Max stored device-name length (matches the `Hello` wire cap, `quic::HELLO_NAME_MAX`).
+const NAME_MAX: usize = 64;
+
 impl NativePairing {
    /// Load the trust store. `store_path = None` uses the default config path. If `arm_at_start`
    /// (the CLI `--allow-pairing`/`--require-pairing` flags), arm immediately with `fixed_pin`
@@ -117,6 +196,7 @@ impl NativePairing {
        Ok(NativePairing {
            arm: Mutex::new(arm),
            paired: Mutex::new(PairedState { path, clients }),
+            pending: Mutex::new(PendingState::default()),
        })
    }

@@ -172,15 +252,33 @@ impl NativePairing {
        self.paired.lock().unwrap().clients.contains(fp_hex)
    }

-    /// Record a successful pairing (re-pairing the same fingerprint just updates the name).
+    /// Record a successful pairing (re-pairing the same fingerprint just updates the name —
+    /// matched case-insensitively, like every other fingerprint comparison here). The name is
+    /// sanitized (untrusted). On a persist failure the in-memory store is rolled back so it never
+    /// diverges from disk. Also clears any pending knock for this fingerprint (it's now paired).
    pub fn add(&self, name: &str, fp_hex: &str) -> Result<()> {
-        let mut p = self.paired.lock().unwrap();
-        p.clients.clients.retain(|c| c.fingerprint != fp_hex);
-        p.clients.clients.push(PairedClient {
-            name: name.to_string(),
-            fingerprint: fp_hex.to_string(),
-        });
-        save(&p)
+        let name = sanitize_device_name(name, fp_hex);
+        {
+            let mut p = self.paired.lock().unwrap();
+            let snapshot = p.clients.clients.clone(); // restore on a failed save
+            p.clients
+                .clients
+                .retain(|c| !c.fingerprint.eq_ignore_ascii_case(fp_hex));
+            p.clients.clients.push(PairedClient {
+                name,
+                fingerprint: fp_hex.to_string(),
+            });
+            if let Err(e) = save(&p) {
+                p.clients.clients = snapshot;
+                return Err(e);
+            }
+        }
+        // A device that knocked and is now paired shouldn't linger in the approval list.
+        let mut pending = self.pending.lock().unwrap();
+        pending
+            .items
+            .retain(|p| !p.fp_hex.eq_ignore_ascii_case(fp_hex));
+        Ok(())
    }

    /// The paired clients (for the management API's device list).
@@ -188,19 +286,122 @@ impl NativePairing {
        self.paired.lock().unwrap().clients.clients.clone()
    }

-    /// Remove a paired client by fingerprint. Returns whether one was removed.
+    /// Remove a paired client by fingerprint. Returns whether one was removed. On a persist
+    /// failure the in-memory store is rolled back (it never diverges from disk).
    pub fn remove(&self, fp_hex: &str) -> Result<bool> {
        let mut p = self.paired.lock().unwrap();
        let before = p.clients.clients.len();
+        let snapshot = p.clients.clients.clone();
        p.clients
            .clients
            .retain(|c| !c.fingerprint.eq_ignore_ascii_case(fp_hex));
        let removed = p.clients.clients.len() != before;
        if removed {
-            save(&p)?;
+            if let Err(e) = save(&p) {
+                p.clients.clients = snapshot;
+                return Err(e);
+            }
        }
        Ok(removed)
    }
+
+    // -- Delegated approval (roadmap §8b-1) --------------------------------
+
+    /// Drop expired pending knocks (called under the lock, mirroring [`Self::expire`]).
+    fn expire_pending(pending: &mut PendingState) {
+        pending
+            .items
+            .retain(|p| p.requested_at.elapsed() < PENDING_TTL);
+    }
+
+    /// Record an unpaired device's knock for delegated approval. Re-knocks from the same
+    /// fingerprint refresh the existing entry in place (same id; a connect-retry loop must not spam
+    /// the list); a fresh fingerprint gets a new id, evicting the **least-recently-active** entry
+    /// past [`PENDING_CAP`]. The name is sanitized (untrusted; see [`sanitize_device_name`]).
+    pub fn note_pending(&self, name: &str, fp_hex: &str) {
+        let name = sanitize_device_name(name, fp_hex);
+        let mut pending = self.pending.lock().unwrap();
+        Self::expire_pending(&mut pending);
+        if let Some(p) = pending
+            .items
+            .iter_mut()
+            .find(|p| p.fp_hex.eq_ignore_ascii_case(fp_hex))
+        {
+            p.requested_at = Instant::now();
+            p.name = name;
+            return;
+        }
+        if pending.items.len() >= PENDING_CAP {
+            // Evict the least-recently-active entry. NOT index 0: the in-place refresh above means
+            // Vec order no longer tracks recency, so pick the minimum `requested_at` explicitly.
+            if let Some(at) = pending
+                .items
+                .iter()
+                .enumerate()
+                .min_by_key(|(_, p)| p.requested_at)
+                .map(|(i, _)| i)
+            {
+                pending.items.remove(at);
+            }
+        }
+        let id = pending.next_id;
+        pending.next_id = pending.next_id.wrapping_add(1);
+        pending.items.push(Pending {
+            id,
+            name,
+            fp_hex: fp_hex.to_string(),
+            requested_at: Instant::now(),
+        });
+    }
+
+    /// The devices currently awaiting approval (for the management API).
+    pub fn pending(&self) -> Vec<PendingRequest> {
+        let mut pending = self.pending.lock().unwrap();
+        Self::expire_pending(&mut pending);
+        pending
+            .items
+            .iter()
+            .map(|p| PendingRequest {
+                id: p.id,
+                name: p.name.clone(),
+                fingerprint: p.fp_hex.clone(),
+                age_secs: p.requested_at.elapsed().as_secs(),
+            })
+            .collect()
+    }
+
+    /// Approve a pending knock: pair its fingerprint (under `name_override` if the operator
+    /// labeled it, else the knock's own name) and drop it from the queue. `Ok(None)` = no such
+    /// (or expired) id.
+    pub fn approve_pending(
+        &self,
+        id: u32,
+        name_override: Option<&str>,
+    ) -> Result<Option<PairedClient>> {
+        let entry = {
+            let mut pending = self.pending.lock().unwrap();
+            Self::expire_pending(&mut pending);
+            let Some(at) = pending.items.iter().position(|p| p.id == id) else {
+                return Ok(None);
+            };
+            pending.items.remove(at)
+        }; // pending lock released — add() takes the paired lock
+        let name = name_override.unwrap_or(&entry.name);
+        self.add(name, &entry.fp_hex)?;
+        Ok(Some(PairedClient {
+            name: name.to_string(),
+            fingerprint: entry.fp_hex,
+        }))
+    }
+
+    /// Deny (drop) a pending knock. Returns whether one was removed. The device's next knock
+    /// re-creates an entry — deny is "not now", not a blocklist.
+    pub fn deny_pending(&self, id: u32) -> bool {
+        let mut pending = self.pending.lock().unwrap();
+        let before = pending.items.len();
+        pending.items.retain(|p| p.id != id);
+        pending.items.len() != before
+    }
 }

 #[cfg(test)]
@@ -250,6 +451,101 @@ mod tests {
        let _ = std::fs::remove_file(&p);
    }

+    #[test]
+    fn pending_knock_approve_and_deny() {
+        let p = temp();
+        let _ = std::fs::remove_file(&p);
+        let np = NativePairing::load_with(Some(p.clone()), None, false).unwrap();
+        assert!(np.pending().is_empty());
+
+        // A knock appears; a re-knock from the same fingerprint refreshes (same id, new name)
+        // instead of duplicating.
+        np.note_pending("device aa11", "AA11");
+        np.note_pending("Bedroom TV", "aa11");
+        let pend = np.pending();
+        assert_eq!(pend.len(), 1, "re-knock dedups by fingerprint");
+        assert_eq!(pend[0].name, "Bedroom TV");
+        let id = pend[0].id;
+
+        // Deny drops it without pairing; the next knock gets a fresh id.
+        assert!(np.deny_pending(id));
+        assert!(!np.deny_pending(id));
+        assert!(np.pending().is_empty());
+        assert!(!np.is_paired("aa11"));
+
+        // Approve pairs the fingerprint (operator label wins) and clears the entry.
+        np.note_pending("device bb22", "BB22");
+        let id = np.pending()[0].id;
+        assert!(
+            np.approve_pending(9999, None).unwrap().is_none(),
+            "unknown id"
+        );
+        let client = np
+            .approve_pending(id, Some("Living Room"))
+            .unwrap()
+            .unwrap();
+        assert_eq!(client.name, "Living Room");
+        assert!(np.is_paired("bb22"), "approval pins the fingerprint");
+        assert!(np.pending().is_empty());
+        assert_eq!(np.list()[0].name, "Living Room");
+
+        // The cap evicts the oldest knock.
+        for i in 0..(PENDING_CAP + 3) {
+            np.note_pending("flood", &format!("f{i:03}"));
+        }
+        let pend = np.pending();
+        assert_eq!(pend.len(), PENDING_CAP);
+        assert_eq!(pend[0].fingerprint, "f003", "oldest entries evicted first");
+        let _ = std::fs::remove_file(&p);
+    }
+
+    #[test]
+    fn sanitize_strips_control_and_bidi() {
+        // ANSI escape + newline + a bidi override that could spoof the displayed name.
+        let dirty = "\u{1b}]0;evil\u{07}Good\nDevice\u{202E}xfp";
+        let clean = sanitize_device_name(dirty, "deadbeef00");
+        assert!(!clean.contains('\u{1b}') && !clean.contains('\n') && !clean.contains('\u{202E}'));
+        // ESC dropped (']' survives), BEL dropped, '\n'→space (Good Device), RLO dropped (no space).
+        assert_eq!(clean, "]0;evilGood Devicexfp");
+        // All-control / empty → fingerprint-derived fallback.
+        assert_eq!(
+            sanitize_device_name("\u{1b}\u{07}", "deadbeef00"),
+            "device deadbeef"
+        );
+        assert_eq!(sanitize_device_name("   ", "abc"), "device abc");
+        // Over-long names cap at a char boundary.
+        assert!(sanitize_device_name(&"x".repeat(200), "ab").len() <= 64);
+    }
+
+    #[test]
+    fn pairing_clears_a_pending_knock() {
+        let p = temp();
+        let _ = std::fs::remove_file(&p);
+        let np = NativePairing::load_with(Some(p.clone()), None, false).unwrap();
+        np.note_pending("Knocker", "cc44");
+        assert_eq!(np.pending().len(), 1);
+        // Pairing the same fingerprint (e.g. via the PIN ceremony) drops the stale pending entry.
+        np.add("Knocker", "CC44").unwrap();
+        assert!(
+            np.pending().is_empty(),
+            "a now-paired device must leave the approval list"
+        );
+        assert!(np.is_paired("cc44"));
+        let _ = std::fs::remove_file(&p);
+    }
+
+    #[test]
+    fn add_replaces_case_insensitively() {
+        let p = temp();
+        let _ = std::fs::remove_file(&p);
+        let np = NativePairing::load_with(Some(p.clone()), None, false).unwrap();
+        np.add("First", "AB12").unwrap();
+        np.add("Second", "ab12").unwrap(); // same device, different hex case
+        assert_eq!(np.list().len(), 1, "re-add must replace, not duplicate");
+        assert_eq!(np.list()[0].name, "Second");
+        let _ = std::fs::remove_file(&p);
+    }
+
    #[test]
    fn cli_flag_arms_with_no_expiry() {
        let p = temp();