eth/filters: enforce topic-limit early on filter criterias (ethereum#…

…29535)

This PR adds a limit of 1000 to the "inner" topics in a filter-criteria

eth/filters/api.go

@@ -44,6 +44,9 @@ var (
 // The maximum number of topic criteria allowed, vm.LOG4 - vm.LOG0
 const maxTopics = 4
 
+// The maximum number of allowed topics within a topic criteria
+const maxSubTopics = 1000
+
 // filter is a helper struct that holds meta information over the filter type
 // and associated subscription in the event system.
 type filter struct {
@@ -620,7 +623,6 @@ func (args *TxFilterCriteria) UnmarshalJSON(data []byte) error {
 	// data is an array consisting of strings.
 	// JSON null values are converted to common.Hash{} and ignored by the filter manager.
 	if len(raw.SigHashes) > 0 {
-
 		parsed, err := decodeSigHashes(raw.SigHashes)
 		if err != nil {
 			return err
@@ -694,6 +696,10 @@ func decodeTopics(input []interface{}) ([][]common.Hash, error) {
 		return nil, nil
 	}
 
+	if len(input) > maxTopics {
+		return nil, errExceedMaxTopics
+	}
+
 	result := make([][]common.Hash, len(input))
 
 	for i, t := range input {
@@ -711,6 +717,9 @@ func decodeTopics(input []interface{}) ([][]common.Hash, error) {
 
 		case []interface{}:
 			// or case e.g. [null, "topic0", "topic1"]
+			if len(topic) > maxSubTopics {
+				return nil, errExceedMaxTopics
+			}
 			for _, rawTopic := range topic {
 				if rawTopic == nil {
 					// null component, match all