DAT-3: Lower Bound Check in Timestamp Validation

light-client/src/errors.rs

@@ -100,6 +100,8 @@ pub enum Error {
     ),
     #[error("OutOfTrustingPeriod: current={0} deadline={1}")]
     OutOfTrustingPeriod(Time, Time),
+    #[error("CurrentTimeBeforeTrustedState: current={0} trusted={1}")]
+    CurrentTimeBeforeTrustedState(Time, Time),
     #[error("HeaderFromFuture: current={0} drift={1:?} header_ts={2}")]
     HeaderFromFuture(Time, core::time::Duration, Time),
     #[error("VerifyMembershipError: err={0:?}")]

light-client/src/misc.rs

@@ -11,6 +11,12 @@ pub fn validate_state_timestamp_within_trusting_period(
     trusting_period: Duration,
     trusted_consensus_state_timestamp: Time,
 ) -> Result<(), Error> {
+    if current_timestamp.lt(&trusted_consensus_state_timestamp) {
+        return Err(Error::CurrentTimeBeforeTrustedState(
+            current_timestamp,
+            trusted_consensus_state_timestamp,
+        ));
+    }
     let trusting_period_end =
         (trusted_consensus_state_timestamp + trusting_period).map_err(Error::TimeError)?;
     if !trusting_period_end.gt(&current_timestamp) {
@@ -81,6 +87,11 @@ mod test {
                 3,
                 trusted_state_timestamp,
             );
+            validate_and_assert_trusted_ts_error(
+                current_timestamp,
+                3,
+                current_timestamp + Duration::new(0, 1),
+            );
         }
 
         // clock drift
@@ -174,4 +185,26 @@ mod test {
             panic!("expected error");
         }
     }
+
+    fn validate_and_assert_trusted_ts_error(
+        current_timestamp: OffsetDateTime,
+        trusting_period: u64,
+        trusted_state_timestamp: OffsetDateTime,
+    ) {
+        let result = validate_state_timestamp_within_trusting_period(
+            Time::from_unix_timestamp_nanos(current_timestamp.unix_timestamp_nanos() as u128)
+                .unwrap(),
+            Duration::from_nanos(trusting_period),
+            Time::from_unix_timestamp_nanos(trusted_state_timestamp.unix_timestamp_nanos() as u128)
+                .unwrap(),
+        );
+        if let Err(e) = result {
+            match e {
+                Error::CurrentTimeBeforeTrustedState(_, _) => {}
+                _ => panic!("unexpected error: {e}"),
+            }
+        } else {
+            panic!("expected error");
+        }
+    }
 }