ci: trigger the PR checks on the retargeted base

The reservation releases on a failed write so a republish can repair the
half that never landed. But each ingest minted a fresh row id, so a retry
after a partial failure (row stored, queue write failed) stored the same
signed content a second time. A replay in a degraded state could repeat a
landed side effect until a budget refused it.

The row id for a verified event is now derived from the replay key, so the
retry's insert dedupes on the existing ON CONFLICT instead of duplicating.
The queue entry still retries, which is the repair the release exists for.
Unsigned events keep a random id: they carry no replay key by design, and
deduplicating unauthenticated content would let an attacker pre-send a
victim's expected event and have the genuine one dropped.

Two existing tests pinned the duplicate write and now assert the deduped
shape: the partial-failure republish repairs the queue entry while the
row stays at one, and the restart readmission's residual effect is a
duplicate queue entry (a refetch), not a second record. The new test
asserts both the retry reaches the writes (WriteFailed, not Replayed) and
the row count stays at one.

crates/gitlawb-core/src/http_sig.rs

@@ -122,15 +122,48 @@ impl HttpSignature {
         })
     }
 
-    /// Reject if the `created` timestamp is more than 5 minutes from now.
+    /// Reject a `created` timestamp outside the acceptance window, which is
+    /// ASYMMETRIC: up to 5 minutes into the past, but only 60 seconds into the
+    /// future.
+    ///
+    /// The two directions are two comparisons rather than one distance, because
+    /// they are not the same event. A signature that arrives late is ordinary:
+    /// clocks run slow, requests queue, and networks are not instant, so the
+    /// past side keeps the full 300-second allowance. A signature stamped ahead
+    /// of this node's clock is not ordinary, and folding both sides into an
+    /// `abs()` let a signer extend its own validity: signed at T with
+    /// `created = T + 300`, it stayed acceptable until roughly T + 600, so the
+    /// effective window was double the one this function advertises. The
+    /// forward tolerance exists only to absorb honest drift between two hosts,
+    /// which is what 60 seconds buys; it is the same allowance the gossip
+    /// path's freshness check uses for the same reason.
     pub fn check_created(&self) -> Result<()> {
+        const MAX_AGE_SECS: i64 = 300;
+        const MAX_FUTURE_SECS: i64 = 60;
+
         let now = Utc::now().timestamp();
-        let skew = (now - self.created).abs();
-        if skew > 300 {
+
+        // Saturating, not plain subtraction. `created` is parsed as an
+        // unrestricted i64 straight from the Signature-Input header, so a
+        // sender picks it: at i64::MIN the past-side subtraction overflows,
+        // which panics a debug build and wraps a release one into an absurd
+        // value that can read as acceptable. Saturating gives the answer the
+        // check wants at both extremes, since a timestamp that far away is
+        // refused by whichever side it saturates toward.
+        let age = now.saturating_sub(self.created);
+        if age > MAX_AGE_SECS {
             return Err(Error::HttpSignature(format!(
-                "clock skew too large: {skew}s (max 300s)"
+                "clock skew too large: created {age}s in the past (max {MAX_AGE_SECS}s)"
             )));
         }
+
+        let ahead = self.created.saturating_sub(now);
+        if ahead > MAX_FUTURE_SECS {
+            return Err(Error::HttpSignature(format!(
+                "clock skew too large: created {ahead}s in the future (max {MAX_FUTURE_SECS}s)"
+            )));
+        }
+
         Ok(())
     }
 
@@ -456,6 +489,75 @@ mod tests {
         assert!(sig.check_created().is_err());
     }
 
+    /// Build a parseable signature whose `created` is `offset` seconds from now
+    /// (negative for the past), so a test can pin one side of the window.
+    fn sig_created_at_offset(offset: i64) -> HttpSignature {
+        let kp = Keypair::generate();
+        let did = kp.did();
+        let created = Utc::now().timestamp() + offset;
+        let sig_input = format!(
+            r#"sig1=("@method" "@path" "content-digest");keyid="{did}";alg="ed25519";created={created}"#
+        );
+        HttpSignature::parse(&sig_input, "sig1=:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA:").unwrap()
+    }
+
+    /// Build a signature at an ABSOLUTE `created`, so a test can drive the
+    /// extremes an offset from now cannot reach.
+    fn sig_created_absolute(created: i64) -> HttpSignature {
+        let kp = Keypair::generate();
+        let did = kp.did();
+        let sig_input = format!(
+            r#"sig1=("@method" "@path" "content-digest");keyid="{did}";alg="ed25519";created={created}"#
+        );
+        HttpSignature::parse(&sig_input, "sig1=:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA:").unwrap()
+    }
+
+    /// `created` is parsed as an unrestricted i64 from a header the sender
+    /// writes, so the window check has to survive both ends of the type. Before
+    /// the saturating form this panicked with "attempt to subtract with
+    /// overflow" on the past side, which is a debug-build crash any client
+    /// could trigger by sending one header value.
+    #[test]
+    fn extreme_created_values_are_refused_rather_than_overflowing() {
+        for created in [i64::MIN, i64::MIN + 1, i64::MAX - 1, i64::MAX] {
+            let err = sig_created_absolute(created)
+                .check_created()
+                .expect_err("an extreme created must be refused, not accepted");
+            let msg = err.to_string();
+            assert!(
+                msg.contains("past") || msg.contains("future"),
+                "created={created} must be refused by a named direction, got: {msg}"
+            );
+        }
+    }
+
+    #[test]
+    fn created_301s_in_past_rejected() {
+        let err = sig_created_at_offset(-301).check_created().unwrap_err();
+        assert!(err.to_string().contains("past"), "{err}");
+    }
+
+    #[test]
+    fn created_299s_in_past_accepted() {
+        assert!(sig_created_at_offset(-299).check_created().is_ok());
+    }
+
+    #[test]
+    fn created_61s_in_future_rejected() {
+        let err = sig_created_at_offset(61).check_created().unwrap_err();
+        assert!(err.to_string().contains("future"), "{err}");
+    }
+
+    #[test]
+    fn created_30s_in_future_accepted() {
+        assert!(sig_created_at_offset(30).check_created().is_ok());
+    }
+
+    #[test]
+    fn created_exactly_now_accepted() {
+        assert!(sig_created_at_offset(0).check_created().is_ok());
+    }
+
     #[test]
     fn fresh_signature_passes_clock_skew() {
         let kp = Keypair::generate();

crates/gitlawb-node/src/metrics.rs

@@ -13,6 +13,9 @@
 //!     `gitlawb_webhook_deliveries_total{result}`
 //!   * is inbound gossip being admitted or shed, and for which reason?
 //!     `gitlawb_gossip_ingest_events_total{outcome}`
+//!   * is the gossip replay seen-set full, and therefore admitting events it
+//!     cannot deduplicate?
+//!     `gitlawb_gossip_replay_guard_saturated_total`
 //!   * how big are the packs we're sending and receiving? —
 //!     `gitlawb_pack_size_bytes`
 //!   * a single `gitlawb_info{version, did}` gauge = 1, for joins/dashboards
@@ -35,8 +38,8 @@
 use std::sync::OnceLock;
 
 use prometheus::{
-    Encoder, Histogram, HistogramOpts, IntCounterVec, IntGauge, IntGaugeVec, Opts, Registry,
-    TextEncoder,
+    Encoder, Histogram, HistogramOpts, IntCounter, IntCounterVec, IntGauge, IntGaugeVec, Opts,
+    Registry, TextEncoder,
 };
 
 /// The single, process-wide metrics registry. Initialized by [`init`].
@@ -52,6 +55,7 @@ static AUTH_FAILURES: OnceLock<IntCounterVec> = OnceLock::new();
 static SYNC_PROCESSED: OnceLock<IntCounterVec> = OnceLock::new();
 static WEBHOOK_DELIVERIES: OnceLock<IntCounterVec> = OnceLock::new();
 static GOSSIP_INGEST: OnceLock<IntCounterVec> = OnceLock::new();
+static GOSSIP_REPLAY_GUARD_SATURATED: OnceLock<IntCounter> = OnceLock::new();
 static PACK_SIZE: OnceLock<Histogram> = OnceLock::new();
 static PEERS_CONNECTED: OnceLock<IntGauge> = OnceLock::new();
 /// 1 when the node started without its p2p identity because the key storage
@@ -191,6 +195,18 @@ fn init_inner(version: &str, node_did: &str) {
         .set(gossip_ingest)
         .expect("set GOSSIP_INGEST once");
 
+    let gossip_replay_guard_saturated = IntCounter::with_opts(Opts::new(
+        "gitlawb_gossip_replay_guard_saturated_total",
+        "Inbound gossip ref-updates admitted without being recorded because the replay seen-set was at capacity",
+    ))
+    .expect("gitlawb_gossip_replay_guard_saturated_total definition");
+    registry
+        .register(Box::new(gossip_replay_guard_saturated.clone()))
+        .expect("register gitlawb_gossip_replay_guard_saturated_total");
+    GOSSIP_REPLAY_GUARD_SATURATED
+        .set(gossip_replay_guard_saturated)
+        .expect("set GOSSIP_REPLAY_GUARD_SATURATED once");
+
     let pack_size = Histogram::with_opts(
         HistogramOpts::new(
             "gitlawb_pack_size_bytes",
@@ -307,7 +323,8 @@ pub fn record_webhook_delivery(result: &str) {
 
 /// Record what the gossip ingest path decided about one inbound ref-update.
 /// `outcome` ∈ {accepted, unsigned_admitted, write_failed, rejected,
-/// source_rate_limited, author_rate_limited, unsigned_source_rate_limited}.
+/// source_rate_limited, author_rate_limited, unsigned_source_rate_limited,
+/// replayed, stale_timestamp}.
 ///
 /// `accepted` is reserved for signature-verified events. An unsigned event that
 /// survives the rolling-upgrade window is `unsigned_admitted`, so the
@@ -332,6 +349,38 @@ pub fn record_gossip_ingest(outcome: &str) {
     }
 }
 
+/// Record one inbound gossip ref-update that the replay seen-set could not
+/// record because it was at capacity.
+///
+/// Label-less on purpose: there is one degradation mode and nothing about it
+/// varies per event, so a label would only add cardinality.
+///
+/// This is an alert-worthy signal, not a debug counter, and it is the ONLY way
+/// the degraded state is visible. At capacity the guard fails open, which means
+/// the event is admitted and `gitlawb_gossip_ingest_events_total{outcome=
+/// "accepted"}` counts it exactly as it counts a healthy admission. Fail-open is
+/// the right policy (a saturated set that dropped all fresh gossip would convert
+/// a loud resource attack into quiet mesh-wide censorship), but it is not a free
+/// one: while this counter is moving, a captured signature can again be replayed
+/// against the freshness window's full 10 minutes, spending a `peer_exists`
+/// round trip and a debit from the victim author's budget on every replay.
+pub fn record_gossip_replay_guard_saturated() {
+    if let Some(c) = GOSSIP_REPLAY_GUARD_SATURATED.get() {
+        c.inc();
+    }
+}
+
+/// Test-only: current `gitlawb_gossip_replay_guard_saturated_total` value (0 if
+/// the registry is not initialized). Lets the seen-set tests assert the
+/// saturation signal fires without scraping the encoded text.
+#[cfg(test)]
+pub fn replay_guard_saturated_count_for_test() -> u64 {
+    GOSSIP_REPLAY_GUARD_SATURATED
+        .get()
+        .map(|c| c.get())
+        .unwrap_or(0)
+}
+
 /// Record a pack body size observation (bytes).
 pub fn observe_pack_size(bytes: f64) {
     if let Some(h) = PACK_SIZE.get() {
@@ -434,6 +483,11 @@ mod tests {
         record_auth_failure("test/route", "test_reason");
         record_sync_processed("done");
         record_webhook_delivery("ok");
+        // `record_gossip_replay_guard_saturated` is deliberately NOT called
+        // here. It is a label-less process-wide counter and the seen-set test
+        // that asserts it asserts a before/after delta, so an increment from a
+        // second test running concurrently in this binary would be a flake with
+        // no diagnostic value.
         record_gossip_ingest("accepted");
         observe_pack_size(1024.0);
         set_peers_connected(0);