macaroons: add BakeFromRootKey function

macaroons/bake.go

@@ -0,0 +1,68 @@
+package macaroons
+
+import (
+	"bytes"
+	"fmt"
+
+	"golang.org/x/net/context"
+	"gopkg.in/macaroon-bakery.v2/bakery"
+	"gopkg.in/macaroon.v2"
+)
+
+// inMemoryRootKeyStore is a simple implementation of bakery.RootKeyStore that
+// stores a single root key in memory.
+type inMemoryRootKeyStore struct {
+	rootKey []byte
+}
+
+// A compile-time check to ensure that inMemoryRootKeyStore implements
+// bakery.RootKeyStore.
+var _ bakery.RootKeyStore = (*inMemoryRootKeyStore)(nil)
+
+// Get returns the root key for the given id. If the item is not there, it
+// returns ErrNotFound.
+func (s *inMemoryRootKeyStore) Get(_ context.Context, id []byte) ([]byte,
+	error) {
+
+	if !bytes.Equal(id, DefaultRootKeyID) {
+		return nil, bakery.ErrNotFound
+	}
+
+	return s.rootKey, nil
+}
+
+// RootKey returns the root key to be used for making a new macaroon, and an id
+// that can be used to look it up later with the Get method.
+func (s *inMemoryRootKeyStore) RootKey(context.Context) ([]byte, []byte,
+	error) {
+
+	return s.rootKey, DefaultRootKeyID, nil
+}
+
+// BakeFromRootKey creates a new macaroon that is derived from the given root
+// key and permissions.
+func BakeFromRootKey(rootKey []byte,
+	permissions []bakery.Op) (*macaroon.Macaroon, error) {
+
+	if len(rootKey) != RootKeyLen {
+		return nil, fmt.Errorf("root key must be %d bytes, is %d",
+			RootKeyLen, len(rootKey))
+	}
+
+	rootKeyStore := &inMemoryRootKeyStore{
+		rootKey: rootKey,
+	}
+
+	service, err := NewService(rootKeyStore, "lnd", false)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create service: %w", err)
+	}
+
+	ctx := context.Background()
+	mac, err := service.NewMacaroon(ctx, DefaultRootKeyID, permissions...)
+	if err != nil {
+		return nil, fmt.Errorf("unable to create macaroon: %w", err)
+	}
+
+	return mac.M(), nil
+}

macaroons/bake_test.go

@@ -0,0 +1,58 @@
+package macaroons_test
+
+import (
+	"context"
+	"encoding/hex"
+	"testing"
+
+	"github.com/lightningnetwork/lnd/macaroons"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/grpc/metadata"
+	"gopkg.in/macaroon-bakery.v2/bakery"
+)
+
+// TestBakeFromRootKey tests that a macaroon can be baked from a root key
+// directly without needing to create a store or service first.
+func TestBakeFromRootKey(t *testing.T) {
+	// Create a test store and unlock it.
+	_, store := newTestStore(t)
+
+	pw := []byte("weks")
+	err := store.CreateUnlock(&pw)
+	require.NoError(t, err)
+
+	// Force the store to create a new random root key.
+	key, id, err := store.RootKey(defaultRootKeyIDContext)
+	require.NoError(t, err)
+	require.Len(t, key, 32)
+
+	tmpKey, err := store.Get(defaultRootKeyIDContext, id)
+	require.NoError(t, err)
+	require.Equal(t, key, tmpKey)
+
+	// Create a service that uses the root key store.
+	service, err := macaroons.NewService(store, "lnd", false)
+	require.NoError(t, err, "Error creating new service")
+	defer func() {
+		require.NoError(t, service.Close())
+	}()
+
+	// Call the BakeFromRootKey function that derives a macaroon directly
+	// from the root key.
+	perms := []bakery.Op{{Entity: "foo", Action: "bar"}}
+	mac, err := macaroons.BakeFromRootKey(key, perms)
+	require.NoError(t, err)
+
+	macaroonBytes, err := mac.MarshalBinary()
+	require.NoError(t, err)
+
+	md := metadata.New(map[string]string{
+		"macaroon": hex.EncodeToString(macaroonBytes),
+	})
+	macCtx := metadata.NewIncomingContext(context.Background(), md)
+
+	// The macaroon should be valid for the service, since the root key was
+	// the same.
+	err = service.ValidateMacaroon(macCtx, nil, "baz")
+	require.NoError(t, err)
+}