Update rpc client header

(cherry picked from commit 091fa517c9)

light/proxy/routes.go

@@ -25,6 +25,8 @@ func RPCRoutes(c *lrpc.Client) map[string]*rpcserver.RPCFunc {
 		"genesis":              rpcserver.NewRPCFunc(makeGenesisFunc(c), ""),
 		"genesis_chunked":      rpcserver.NewRPCFunc(makeGenesisChunkedFunc(c), ""),
 		"block":                rpcserver.NewRPCFunc(makeBlockFunc(c), "height"),
+		"header":               rpcserver.NewRPCFunc(makeHeaderFunc(c), "height"),
+		"header_by_hash":       rpcserver.NewRPCFunc(makeHeaderByHashFunc(c), "hash"),
 		"block_by_hash":        rpcserver.NewRPCFunc(makeBlockByHashFunc(c), "hash"),
 		"block_results":        rpcserver.NewRPCFunc(makeBlockResultsFunc(c), "height"),
 		"commit":               rpcserver.NewRPCFunc(makeCommitFunc(c), "height"),
@@ -109,6 +111,22 @@ func makeBlockFunc(c *lrpc.Client) rpcBlockFunc {
 	}
 }
 
+type rpcHeaderFunc func(ctx *rpctypes.Context, height *int64) (*ctypes.ResultHeader, error)
+
+func makeHeaderFunc(c *lrpc.Client) rpcHeaderFunc {
+	return func(ctx *rpctypes.Context, height *int64) (*ctypes.ResultHeader, error) {
+		return c.Header(ctx.Context(), height)
+	}
+}
+
+type rpcHeaderByHashFunc func(ctx *rpctypes.Context, hash []byte) (*ctypes.ResultHeader, error)
+
+func makeHeaderByHashFunc(c *lrpc.Client) rpcHeaderByHashFunc {
+	return func(ctx *rpctypes.Context, hash []byte) (*ctypes.ResultHeader, error) {
+		return c.HeaderByHash(ctx.Context(), hash)
+	}
+}
+
 type rpcBlockByHashFunc func(ctx *rpctypes.Context, hash []byte) (*ctypes.ResultBlock, error)
 
 func makeBlockByHashFunc(c *lrpc.Client) rpcBlockByHashFunc {

light/rpc/client.go

@@ -440,6 +440,40 @@ func (c *Client) BlockResults(ctx context.Context, height *int64) (*ctypes.Resul
 	return res, nil
 }
 
+// Header fetches and verifies the header directly via the light client
+func (c *Client) Header(ctx context.Context, height *int64) (*ctypes.ResultHeader, error) {
+	lb, err := c.updateLightClientIfNeededTo(ctx, height)
+	if err != nil {
+		return nil, err
+	}
+
+	return &ctypes.ResultHeader{Header: lb.Header}, nil
+}
+
+// HeaderByHash calls rpcclient#HeaderByHash and updates the client if it's falling behind.
+func (c *Client) HeaderByHash(ctx context.Context, hash tmbytes.HexBytes) (*ctypes.ResultHeader, error) {
+	res, err := c.next.HeaderByHash(ctx, hash)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := res.Header.ValidateBasic(); err != nil {
+		return nil, err
+	}
+
+	lb, err := c.updateLightClientIfNeededTo(ctx, &res.Header.Height)
+	if err != nil {
+		return nil, err
+	}
+
+	if !bytes.Equal(lb.Header.Hash(), res.Header.Hash()) {
+		return nil, fmt.Errorf("primary header hash does not match trusted header hash. (%X != %X)",
+			lb.Header.Hash(), res.Header.Hash())
+	}
+
+	return res, nil
+}
+
 func (c *Client) Commit(ctx context.Context, height *int64) (*ctypes.ResultCommit, error) {
 	// Update the light client if we're behind and retrieve the light block at the requested height
 	// or at the latest height if no height is provided.