fix: correct underflow in random_updated_at

crates/price-estimation/src/native_price_cache.rs

@@ -197,9 +197,16 @@ impl Cache {
     /// in the past, to avoid spikes of expired prices all being fetched at
     /// once.
     fn random_updated_at(max_age: Duration, now: Instant, rng: &mut impl Rng) -> Instant {
-        let percent_expired = rng.random_range(50..=90);
-        let age = max_age.as_secs() * percent_expired / 100;
-        now - Duration::from_secs(age)
+        let percent_expired: u32 = rng.random_range(50..=90);
+
+        let age = max_age
+            .checked_mul(percent_expired)
+            .map(|age| age / 100)
+            .unwrap_or(Duration::MAX);
+
+        now.checked_sub(age)
+            .or_else(|| now.checked_sub(Duration::from_secs(1)))
+            .unwrap_or(now)
     }
 
     fn len(&self) -> usize {
@@ -1143,4 +1150,34 @@ mod tests {
             anyhow!("protocol")
         ))));
     }
+
+    #[test]
+    fn random_updated_at_underflow_check() {
+        let now = Instant::now();
+        let max_age = Duration::MAX;
+        let mut rng = rand::rng();
+
+        let updated_at = Cache::random_updated_at(max_age, now, &mut rng);
+
+        assert!(updated_at < now);
+        assert!(updated_at >= now - Duration::from_secs(1));
+    }
+
+    #[test]
+    fn random_updated_at_range() {
+        let now = Instant::now();
+        let max_age = Duration::from_secs(600);
+        let mut rng = rand::rng();
+
+        for _ in 0..100 {
+            let updated_at = Cache::random_updated_at(max_age, now, &mut rng);
+
+            let min_age = max_age * 50 / 100;
+            let max_age_check = max_age * 90 / 100;
+
+            assert!(updated_at < now);
+            assert!(updated_at <= now - min_age);
+            assert!(updated_at >= now - max_age_check);
+        }
+    }
 }