chainkit: expose getblockheader

cmd/lncli/chainrpc_active.go

@@ -25,6 +25,7 @@ func chainCommands() []cli.Command {
 				getBlockCommand,
 				getBestBlockCommand,
 				getBlockHashCommand,
+				getBlockHeaderCommand,
 			},
 		},
 	}
@@ -113,6 +114,45 @@ func getBlock(ctx *cli.Context) error {
 	return nil
 }
 
+var getBlockHeaderCommand = cli.Command{
+	Name:        "getblockheader",
+	Usage:       "Get a block header.",
+	Category:    "On-chain",
+	Description: "Returns a block header with a particular block hash.",
+	ArgsUsage:   "hash",
+	Action:      actionDecorator(getBlockHeader),
+}
+
+func getBlockHeader(ctx *cli.Context) error {
+	ctxc := getContext()
+	args := ctx.Args()
+
+	// Display the command's help message if we do not have the expected
+	// number of arguments/flags.
+	if !args.Present() {
+		return cli.ShowCommandHelp(ctx, "getblockheader")
+	}
+
+	blockHash, err := chainhash.NewHashFromStr(args.First())
+	if err != nil {
+		return err
+	}
+
+	req := &chainrpc.GetBlockHeaderRequest{BlockHash: blockHash[:]}
+
+	client, cleanUp := getChainClient(ctx)
+	defer cleanUp()
+
+	resp, err := client.GetBlockHeader(ctxc, req)
+	if err != nil {
+		return err
+	}
+
+	printRespJSON(resp)
+
+	return nil
+}
+
 var getBestBlockCommand = cli.Command{
 	Name:     "getbestblock",
 	Category: "On-chain",

cmd/lncli/neutrino_active.go

@@ -155,16 +155,16 @@ func isBanned(ctx *cli.Context) error {
 	return nil
 }
 
-var getBlockHeaderCommand = cli.Command{
+var getBlockHeaderNeutrinoCommand = cli.Command{
 	Name:        "getblockheader",
 	Usage:       "Get a block header.",
 	Category:    "Neutrino",
 	Description: "Returns a block header with a particular block hash.",
 	ArgsUsage:   "hash",
-	Action:      actionDecorator(getBlockHeader),
+	Action:      actionDecorator(getBlockHeaderNeutrino),
 }
 
-func getBlockHeader(ctx *cli.Context) error {
+func getBlockHeaderNeutrino(ctx *cli.Context) error {
 	ctxc := getContext()
 	args := ctx.Args()
 
@@ -239,7 +239,7 @@ func neutrinoCommands() []cli.Command {
 				addPeerCommand,
 				disconnectPeerCommand,
 				isBannedCommand,
-				getBlockHeaderCommand,
+				getBlockHeaderNeutrinoCommand,
 				getCFilterCommand,
 			},
 		},

contractcourt/channel_arbitrator_test.go

@@ -187,6 +187,10 @@ func (*mockChainIO) GetBlock(blockHash *chainhash.Hash) (*wire.MsgBlock, error)
 	return nil, nil
 }
 
+func (*mockChainIO) GetBlockHeader(*chainhash.Hash) (*wire.BlockHeader, error) {
+	return nil, nil
+}
+
 type chanArbTestCtx struct {
 	t *testing.T
 

docs/release-notes/release-notes-0.17.1.md

@@ -36,6 +36,10 @@
   instead.
 
 ## RPC Additions
+
+* [`chainrpc` `GetBlockHeader`](https://github.com/lightningnetwork/lnd/pull/8111)
+  can be used to get block headers with any chain backend.
+
 ## lncli Additions
 
 # Improvements

itest/lnd_onchain_test.go

@@ -26,6 +26,7 @@ func testChainKit(ht *lntest.HarnessTest) {
 	// during execution. By calling sub-test functions as seen below we
 	// avoid the need to start separate nodes.
 	testChainKitGetBlock(ht)
+	testChainKitGetBlockHeader(ht)
 	testChainKitGetBlockHash(ht)
 	testChainKitSendOutputsAnchorReserve(ht)
 }
@@ -58,6 +59,49 @@ func testChainKitGetBlock(ht *lntest.HarnessTest) {
 	require.Equal(ht, expected, actual)
 }
 
+// testChainKitGetBlockHeader ensures that given a block hash, the RPC endpoint
+// returns the correct target block header.
+func testChainKitGetBlockHeader(ht *lntest.HarnessTest) {
+	// Get best block hash.
+	bestBlockRes := ht.Alice.RPC.GetBestBlock(nil)
+
+	var (
+		bestBlockHash   chainhash.Hash
+		bestBlockHeader wire.BlockHeader
+		msgBlock        = &wire.MsgBlock{}
+	)
+	err := bestBlockHash.SetBytes(bestBlockRes.BlockHash)
+	require.NoError(ht, err)
+
+	// Retrieve the best block by hash.
+	getBlockReq := &chainrpc.GetBlockRequest{
+		BlockHash: bestBlockHash[:],
+	}
+	getBlockRes := ht.Alice.RPC.GetBlock(getBlockReq)
+
+	// Deserialize the block which was retrieved by hash.
+	blockReader := bytes.NewReader(getBlockRes.RawBlock)
+	err = msgBlock.Deserialize(blockReader)
+	require.NoError(ht, err)
+
+	// Retrieve the block header for the best block.
+	getBlockHeaderReq := &chainrpc.GetBlockHeaderRequest{
+		BlockHash: bestBlockHash[:],
+	}
+	getBlockHeaderRes := ht.Alice.RPC.GetBlockHeader(getBlockHeaderReq)
+
+	// Deserialize the block header which was retrieved by hash.
+	blockHeaderReader := bytes.NewReader(getBlockHeaderRes.RawBlockHeader)
+	err = bestBlockHeader.Deserialize(blockHeaderReader)
+	require.NoError(ht, err)
+
+	// Ensure the header of the best block is the same as retrieved block
+	// header.
+	expected := bestBlockHeader
+	actual := msgBlock.Header
+	require.Equal(ht, expected, actual)
+}
+
 // testChainKitGetBlockHash ensures that given a block height, the RPC endpoint
 // returns the correct target block hash.
 func testChainKitGetBlockHash(ht *lntest.HarnessTest) {

lnrpc/chainrpc/chain_server.go

@@ -46,6 +46,10 @@ var (
 			Entity: "onchain",
 			Action: "read",
 		}},
+		"/chainrpc.ChainKit/GetBlockHeader": {{
+			Entity: "onchain",
+			Action: "read",
+		}},
 		"/chainrpc.ChainKit/GetBestBlock": {{
 			Entity: "onchain",
 			Action: "read",
@@ -293,6 +297,31 @@ func (s *Server) GetBlock(_ context.Context,
 	return &GetBlockResponse{RawBlock: rawBlock}, nil
 }
 
+// GetBlockHeader returns a block header given the corresponding block hash.
+func (s *Server) GetBlockHeader(_ context.Context,
+	in *GetBlockHeaderRequest) (*GetBlockHeaderResponse, error) {
+
+	// We'll start by reconstructing the RPC request into what the
+	// underlying chain functionality expects.
+	var blockHash chainhash.Hash
+	copy(blockHash[:], in.BlockHash)
+
+	blockHeader, err := s.cfg.Chain.GetBlockHeader(&blockHash)
+	if err != nil {
+		return nil, err
+	}
+
+	// Serialize block header for RPC response.
+	var headerBuf bytes.Buffer
+	err = blockHeader.Serialize(&headerBuf)
+	if err != nil {
+		return nil, err
+	}
+	rawHeader := headerBuf.Bytes()
+
+	return &GetBlockHeaderResponse{RawBlockHeader: rawHeader}, nil
+}
+
 // GetBestBlock returns the latest block hash and current height of the valid
 // most-work chain.
 func (s *Server) GetBestBlock(_ context.Context,