Handle addition overflow in /eth/v1/beacon/rewards/attestations/{epoch} (#15970)

* Handle addition overflow in `/eth/v1/beacon/rewards/attestations/{epoch}`

* Changelog

beacon-chain/rpc/eth/rewards/handlers.go

@@ -209,8 +209,13 @@ func (s *Server) attRewardsState(w http.ResponseWriter, r *http.Request) (state.
 		httputil.HandleError(w, "Attestation rewards are not supported for Phase 0", http.StatusNotFound)
 		return nil, false
 	}
-	currentEpoch := uint64(slots.ToEpoch(s.TimeFetcher.CurrentSlot()))
-	if requestedEpoch+1 >= currentEpoch {
+	currentEpoch := slots.ToEpoch(s.TimeFetcher.CurrentSlot())
+	bufferedEpoch, err := primitives.Epoch(requestedEpoch).SafeAdd(1)
+	if err != nil {
+		httputil.HandleError(w, "Could not increment epoch: "+err.Error(), http.StatusNotFound)
+		return nil, false
+	}
+	if bufferedEpoch >= currentEpoch {
 		httputil.HandleError(w,
 			"Attestation rewards are available after two epoch transitions to ensure all attestations have a chance of inclusion",
 			http.StatusNotFound)

beacon-chain/rpc/eth/rewards/handlers_test.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"math"
 	"net/http"
 	"net/http/httptest"
 	"strconv"
@@ -747,6 +748,18 @@ func TestAttestationRewards(t *testing.T) {
 		assert.Equal(t, http.StatusNotFound, e.Code)
 		assert.Equal(t, "Attestation rewards are available after two epoch transitions to ensure all attestations have a chance of inclusion", e.Message)
 	})
+	t.Run("epoch overflow", func(t *testing.T) {
+		url := "http://only.the.epoch.number.at.the.end.is.important/" + strconv.FormatUint(math.MaxUint64, 10)
+		request := httptest.NewRequest("POST", url, nil)
+		writer := httptest.NewRecorder()
+		writer.Body = &bytes.Buffer{}
+
+		s.AttestationRewards(writer, request)
+		assert.Equal(t, http.StatusNotFound, writer.Code)
+		e := &httputil.DefaultJsonError{}
+		require.NoError(t, json.Unmarshal(writer.Body.Bytes(), e))
+		assert.Equal(t, http.StatusNotFound, e.Code)
+	})
 }
 
 func TestSyncCommiteeRewards(t *testing.T) {

changelog/syjn99-attestation-epoch-overflow.md

@@ -0,0 +1,2 @@
+### Fixed 
+- Fix #15969: Handle addition overflow in `/eth/v1/beacon/rewards/attestations/{epoch}`.