lite2/rpc: verify block results and validators (#4703)

Closes: #4695

Verify /block_results and /validators responses from an HTTP client using the light client.

Added count and total to /validators response.

Refs #3113

rpc/core/consensus.go

@@ -10,9 +10,11 @@ import (
 )
 
 // Validators gets the validator set at the given block height.
-// If no height is provided, it will fetch the current validator set.
-// Note the validators are sorted by their address - this is the canonical
-// order for the validators in the set as used in computing their Merkle root.
+//
+// If no height is provided, it will fetch the current validator set. Note the
+// validators are sorted by their address - this is the canonical order for the
+// validators in the set as used in computing their Merkle root.
+//
 // More: https://docs.tendermint.com/master/rpc/#/Info/validators
 func Validators(ctx *rpctypes.Context, heightPtr *int64, page, perPage int) (*ctypes.ResultValidators, error) {
 	// The latest validator that we know is the
@@ -41,7 +43,9 @@ func Validators(ctx *rpctypes.Context, heightPtr *int64, page, perPage int) (*ct
 
 	return &ctypes.ResultValidators{
 		BlockHeight: height,
-		Validators:  v}, nil
+		Validators:  v,
+		Count:       len(v),
+		Total:       totalCount}, nil
 }
 
 // DumpConsensusState dumps consensus state.

rpc/core/types/responses.go

@@ -122,10 +122,14 @@ type Peer struct {
 	RemoteIP         string               `json:"remote_ip"`
 }
 
-// Validators for a height
+// Validators for a height.
 type ResultValidators struct {
 	BlockHeight int64              `json:"block_height"`
 	Validators  []*types.Validator `json:"validators"`
+	// Count of actual validators in this result
+	Count int `json:"count"`
+	// Total number of validators
+	Total int `json:"total"`
 }
 
 // ConsensusParams for given height