simplify initialization of light client (#6530)

cmd/tendermint/commands/light.go

@@ -1,7 +1,6 @@
 package commands
 
 import (
-	"bufio"
 	"context"
 	"errors"
 	"fmt"
@@ -148,25 +147,7 @@ func runProxy(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("can't parse trust level: %w", err)
 	}
 
-	options := []light.Option{
-		light.Logger(logger),
-		light.ConfirmationFunction(func(action string) bool {
-			fmt.Println(action)
-			scanner := bufio.NewScanner(os.Stdin)
-			for {
-				scanner.Scan()
-				response := scanner.Text()
-				switch response {
-				case "y", "Y":
-					return true
-				case "n", "N":
-					return false
-				default:
-					fmt.Println("please input 'Y' or 'n' and press ENTER")
-				}
-			}
-		}),
-	}
+	options := []light.Option{light.Logger(logger)}
 
 	if sequential {
 		options = append(options, light.SequentialVerification())
@@ -174,31 +155,21 @@ func runProxy(cmd *cobra.Command, args []string) error {
 		options = append(options, light.SkippingVerification(trustLevel))
 	}
 
-	var c *light.Client
-	if trustedHeight > 0 && len(trustedHash) > 0 { // fresh installation
-		c, err = light.NewHTTPClient(
-			context.Background(),
-			chainID,
-			light.TrustOptions{
-				Period: trustingPeriod,
-				Height: trustedHeight,
-				Hash:   trustedHash,
-			},
-			primaryAddr,
-			witnessesAddrs,
-			dbs.New(db),
-			options...,
-		)
-	} else { // continue from latest state
-		c, err = light.NewHTTPClientFromTrustedStore(
-			chainID,
-			trustingPeriod,
-			primaryAddr,
-			witnessesAddrs,
-			dbs.New(db),
-			options...,
-		)
-	}
+	// Initiate the light client. If the trusted store already has blocks in it, this
+	// will be used else we use the trusted options.
+	c, err := light.NewHTTPClient(
+		context.Background(),
+		chainID,
+		light.TrustOptions{
+			Period: trustingPeriod,
+			Height: trustedHeight,
+			Hash:   trustedHash,
+		},
+		primaryAddr,
+		witnessesAddrs,
+		dbs.New(db),
+		options...,
+	)
 	if err != nil {
 		return err
 	}

light/client.go

@@ -92,15 +92,6 @@ func PruningSize(h uint16) Option {
 	}
 }
 
-// ConfirmationFunction option can be used to prompt to confirm an action. For
-// example, remove newer headers if the light client is being reset with an
-// older header. No confirmation is required by default!
-func ConfirmationFunction(fn func(action string) bool) Option {
-	return func(c *Client) {
-		c.confirmationFn = fn
-	}
-}
-
 // Logger option can be used to set a logger for the client.
 func Logger(l log.Logger) Option {
 	return func(c *Client) {
@@ -155,14 +146,8 @@ type Client struct {
 	// Highest trusted light block from the store (height=H).
 	latestTrustedBlock *types.LightBlock
 
-	// See RemoveNoLongerTrustedHeadersPeriod option
+	// See PruningSize option
 	pruningSize uint16
-	// See ConfirmationFunction option
-	confirmationFn func(action string) bool
-	// The light client keeps track of how many times it has requested a light
-	// block from it's providers. When this exceeds the amount of witnesses the
-	// light client will just return the last error sent by the providers
-	// repeatRequests uint16
 
 	logger log.Logger
 }
@@ -186,35 +171,62 @@ func NewClient(
 	trustedStore store.Store,
 	options ...Option) (*Client, error) {
 
+	// Check whether the trusted store already has a trusted block. If so, then create
+	// a new client from the trusted store instead of the trust options.
+	lastHeight, err := trustedStore.LastLightBlockHeight()
+	if err != nil {
+		return nil, err
+	}
+	if lastHeight > 0 {
+		return NewClientFromTrustedStore(
+			chainID, trustOptions.Period, primary, witnesses, trustedStore, options...,
+		)
+	}
+
+	// Validate trust options
 	if err := trustOptions.ValidateBasic(); err != nil {
 		return nil, fmt.Errorf("invalid TrustOptions: %w", err)
 	}
 
-	c, err := NewClientFromTrustedStore(chainID, trustOptions.Period, primary, witnesses, trustedStore, options...)
-	if err != nil {
+	// Validate the number of witnesses.
+	if len(witnesses) < 1 {
+		return nil, ErrNoWitnesses
+	}
+
+	c := &Client{
+		chainID:          chainID,
+		trustingPeriod:   trustOptions.Period,
+		verificationMode: skipping,
+		trustLevel:       DefaultTrustLevel,
+		maxClockDrift:    defaultMaxClockDrift,
+		maxBlockLag:      defaultMaxBlockLag,
+		primary:          primary,
+		witnesses:        witnesses,
+		trustedStore:     trustedStore,
+		pruningSize:      defaultPruningSize,
+		logger:           log.NewNopLogger(),
+	}
+
+	for _, o := range options {
+		o(c)
+	}
+
+	// Validate trust level.
+	if err := ValidateTrustLevel(c.trustLevel); err != nil {
 		return nil, err
 	}
 
-	if c.latestTrustedBlock != nil {
-		c.logger.Info("checking trusted light block using options")
-		if err := c.checkTrustedHeaderUsingOptions(ctx, trustOptions); err != nil {
-			return nil, err
-		}
+	// Use the trusted hash and height to fetch the first weakly-trusted block
+	// from the primary provider. Assert that all the witnesses have the same block
+	if err := c.initializeWithTrustOptions(ctx, trustOptions); err != nil {
+		return nil, err
 	}
 
-	if c.latestTrustedBlock == nil || c.latestTrustedBlock.Height < trustOptions.Height {
-		c.logger.Info("downloading trusted light block using options")
-		if err := c.initializeWithTrustOptions(ctx, trustOptions); err != nil {
-			return nil, err
-		}
-	}
-
-	return c, err
+	return c, nil
 }
 
-// NewClientFromTrustedStore initializes existing client from the trusted store.
-//
-// See NewClient
+// NewClientFromTrustedStore initializes an existing client from the trusted store.
+// It does not check that the providers have the same trusted block.
 func NewClientFromTrustedStore(
 	chainID string,
 	trustingPeriod time.Duration,
@@ -234,7 +246,6 @@ func NewClientFromTrustedStore(
 		witnesses:        witnesses,
 		trustedStore:     trustedStore,
 		pruningSize:      defaultPruningSize,
-		confirmationFn:   func(action string) bool { return true },
 		logger:           log.NewNopLogger(),
 	}
 
@@ -252,6 +263,7 @@ func NewClientFromTrustedStore(
 		return nil, err
 	}
 
+	// Check that the trusted store has at least one block and
 	if err := c.restoreTrustedLightBlock(); err != nil {
 		return nil, err
 	}
@@ -265,126 +277,48 @@ func (c *Client) restoreTrustedLightBlock() error {
 	if err != nil {
 		return fmt.Errorf("can't get last trusted light block height: %w", err)
 	}
-
-	if lastHeight > 0 {
-		trustedBlock, err := c.trustedStore.LightBlock(lastHeight)
-		if err != nil {
-			return fmt.Errorf("can't get last trusted light block: %w", err)
-		}
-		c.latestTrustedBlock = trustedBlock
-		c.logger.Info("restored trusted light block", "height", lastHeight)
+	if lastHeight <= 0 {
+		return errors.New("trusted store is empty")
 	}
 
-	return nil
-}
-
-// if options.Height:
-//
-//     1) ahead of trustedLightBlock.Height => fetch light blocks (same height as
-//     trustedLightBlock) from primary provider and check it's hash matches the
-//     trustedLightBlock's hash (if not, remove trustedLightBlock and all the light blocks
-//     before)
-//
-//     2) equals trustedLightBlock.Height => check options.Hash matches the
-//     trustedLightBlock's hash (if not, remove trustedLightBlock and all the light blocks
-//     before)
-//
-//     3) behind trustedLightBlock.Height => remove all the light blocks between
-//     options.Height and trustedLightBlock.Height, update trustedLightBlock, then
-//     check options.Hash matches the trustedLightBlock's hash (if not, remove
-//     trustedLightBlock and all the light blocks before)
-//
-// The intuition here is the user is always right. I.e. if she decides to reset
-// the light client with an older header, there must be a reason for it.
-func (c *Client) checkTrustedHeaderUsingOptions(ctx context.Context, options TrustOptions) error {
-	var primaryHash []byte
-	switch {
-	case options.Height > c.latestTrustedBlock.Height:
-		h, err := c.lightBlockFromPrimary(ctx, c.latestTrustedBlock.Height)
-		if err != nil {
-			return err
-		}
-		primaryHash = h.Hash()
-	case options.Height == c.latestTrustedBlock.Height:
-		primaryHash = options.Hash
-	case options.Height < c.latestTrustedBlock.Height:
-		c.logger.Info("client initialized with old header (trusted is more recent)",
-			"old", options.Height,
-			"trustedHeight", c.latestTrustedBlock.Height,
-			"trustedHash", c.latestTrustedBlock.Hash())
-
-		action := fmt.Sprintf(
-			"Rollback to %d (%X)? Note this will remove newer light blocks up to %d (%X)",
-			options.Height, options.Hash,
-			c.latestTrustedBlock.Height, c.latestTrustedBlock.Hash())
-		if c.confirmationFn(action) {
-			// remove all the headers (options.Height, trustedHeader.Height]
-			err := c.cleanupAfter(options.Height)
-			if err != nil {
-				return fmt.Errorf("cleanupAfter(%d): %w", options.Height, err)
-			}
-
-			c.logger.Info("Rolled back to older header (newer headers were removed)",
-				"old", options.Height)
-		} else {
-			return nil
-		}
-
-		primaryHash = options.Hash
-	}
-
-	if !bytes.Equal(primaryHash, c.latestTrustedBlock.Hash()) {
-		c.logger.Info("previous trusted header's hash (h1) doesn't match hash from primary provider (h2)",
-			"h1", c.latestTrustedBlock.Hash(), "h2", primaryHash)
-
-		action := fmt.Sprintf(
-			"Previous trusted header's hash %X doesn't match hash %X from primary provider. Remove all the stored light blocks?",
-			c.latestTrustedBlock.Hash(), primaryHash)
-		if c.confirmationFn(action) {
-			err := c.Cleanup()
-			if err != nil {
-				return fmt.Errorf("failed to cleanup: %w", err)
-			}
-		} else {
-			return errors.New("refused to remove the stored light blocks despite hashes mismatch")
-		}
+	trustedBlock, err := c.trustedStore.LightBlock(lastHeight)
+	if err != nil {
+		return fmt.Errorf("can't get last trusted light block: %w", err)
 	}
+	c.latestTrustedBlock = trustedBlock
+	c.logger.Info("restored trusted light block", "height", lastHeight)
 
 	return nil
 }
 
 // initializeWithTrustOptions fetches the weakly-trusted light block from
-// primary provider.
+// primary provider, matches it to the trusted hash, and sets it as the
+// lastTrustedBlock. It then asserts that all witnesses have the same light block.
 func (c *Client) initializeWithTrustOptions(ctx context.Context, options TrustOptions) error {
-	// 1) Fetch and verify the light block.
+	// 1) Fetch and verify the light block. Note that we do not verify the time of the first block
 	l, err := c.lightBlockFromPrimary(ctx, options.Height)
 	if err != nil {
 		return err
 	}
 
-	// NOTE: - Verify func will check if it's expired or not.
-	//       - h.Time is not being checked against time.Now() because we don't
-	//         want to add yet another argument to NewClient* functions.
-	if err := l.ValidateBasic(c.chainID); err != nil {
-		return err
-	}
-
-	if !bytes.Equal(l.Hash(), options.Hash) {
+	// 2) Assert that the hashes match
+	if !bytes.Equal(l.Header.Hash(), options.Hash) {
 		return fmt.Errorf("expected header's hash %X, but got %X", options.Hash, l.Hash())
 	}
 
-	// 2) Ensure that +2/3 of validators signed correctly.
+	// 3) Ensure that +2/3 of validators signed correctly. This also sanity checks that the
+	// chain ID is the same.
 	err = l.ValidatorSet.VerifyCommitLight(c.chainID, l.Commit.BlockID, l.Height, l.Commit)
 	if err != nil {
 		return fmt.Errorf("invalid commit: %w", err)
 	}
 
-	// 3) Cross-verify with witnesses to ensure everybody has the same state.
+	// 4) Cross-verify with witnesses to ensure everybody has the same state.
 	if err := c.compareFirstHeaderWithWitnesses(ctx, l.SignedHeader); err != nil {
 		return err
 	}
 
-	// 4) Persist both of them and continue.
+	// 5) Persist both of them and continue.
 	return c.updateTrustedLightBlock(l)
 }
 
@@ -885,37 +819,6 @@ func (c *Client) Cleanup() error {
 	return c.trustedStore.Prune(0)
 }
 
-// cleanupAfter deletes all headers & validator sets after +height+. It also
-// resets latestTrustedBlock to the latest header.
-func (c *Client) cleanupAfter(height int64) error {
-	prevHeight := c.latestTrustedBlock.Height
-
-	for {
-		h, err := c.trustedStore.LightBlockBefore(prevHeight)
-		if err == store.ErrLightBlockNotFound || (h != nil && h.Height <= height) {
-			break
-		} else if err != nil {
-			return fmt.Errorf("failed to get header before %d: %w", prevHeight, err)
-		}
-
-		err = c.trustedStore.DeleteLightBlock(h.Height)
-		if err != nil {
-			c.logger.Error("can't remove a trusted header & validator set", "err", err,
-				"height", h.Height)
-		}
-
-		prevHeight = h.Height
-	}
-
-	c.latestTrustedBlock = nil
-	err := c.restoreTrustedLightBlock()
-	if err != nil {
-		return err
-	}
-
-	return nil
-}
-
 func (c *Client) updateTrustedLightBlock(l *types.LightBlock) error {
 	c.logger.Debug("updating trusted light block", "light_block", l)
 

light/client_test.go

@@ -57,7 +57,6 @@ var (
 		3: h3,
 	}
 	l1       = &types.LightBlock{SignedHeader: h1, ValidatorSet: vals}
-	l2       = &types.LightBlock{SignedHeader: h2, ValidatorSet: vals}
 	fullNode = mockp.New(
 		chainID,
 		headerSet,
@@ -458,7 +457,7 @@ func TestClient_Cleanup(t *testing.T) {
 }
 
 // trustedHeader.Height == options.Height
-func TestClientRestoresTrustedHeaderAfterStartup1(t *testing.T) {
+func TestClientRestoresTrustedHeaderAfterStartup(t *testing.T) {
 	// 1. options.Hash == trustedHeader.Hash
 	{
 		trustedStore := dbs.New(dbm.NewMemDB())
@@ -520,184 +519,13 @@ func TestClientRestoresTrustedHeaderAfterStartup1(t *testing.T) {
 		l, err := c.TrustedLightBlock(1)
 		assert.NoError(t, err)
 		if assert.NotNil(t, l) {
-			assert.Equal(t, l.Hash(), header1.Hash())
+			// client take the trusted store and ignores the trusted options
+			assert.Equal(t, l.Hash(), l1.Hash())
 			assert.NoError(t, l.ValidateBasic(chainID))
 		}
 	}
 }
 
-// trustedHeader.Height < options.Height
-func TestClientRestoresTrustedHeaderAfterStartup2(t *testing.T) {
-	// 1. options.Hash == trustedHeader.Hash
-	{
-		trustedStore := dbs.New(dbm.NewMemDB())
-		err := trustedStore.SaveLightBlock(l1)
-		require.NoError(t, err)
-
-		c, err := light.NewClient(
-			ctx,
-			chainID,
-			light.TrustOptions{
-				Period: 4 * time.Hour,
-				Height: 2,
-				Hash:   h2.Hash(),
-			},
-			fullNode,
-			[]provider.Provider{fullNode},
-			trustedStore,
-			light.Logger(log.TestingLogger()),
-		)
-		require.NoError(t, err)
-
-		// Check we still have the 1st header (+header+).
-		l, err := c.TrustedLightBlock(1)
-		assert.NoError(t, err)
-		assert.NotNil(t, l)
-		assert.Equal(t, l.Hash(), h1.Hash())
-		assert.NoError(t, l.ValidateBasic(chainID))
-	}
-
-	// 2. options.Hash != trustedHeader.Hash
-	// This could happen if previous provider was lying to us.
-	{
-		trustedStore := dbs.New(dbm.NewMemDB())
-		err := trustedStore.SaveLightBlock(l1)
-		require.NoError(t, err)
-
-		// header1 != header
-		diffHeader1 := keys.GenSignedHeader(chainID, 1, bTime.Add(1*time.Hour), nil, vals, vals,
-			hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys))
-
-		diffHeader2 := keys.GenSignedHeader(chainID, 2, bTime.Add(2*time.Hour), nil, vals, vals,
-			hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys))
-
-		primary := mockp.New(
-			chainID,
-			map[int64]*types.SignedHeader{
-				1: diffHeader1,
-				2: diffHeader2,
-			},
-			valSet,
-		)
-
-		c, err := light.NewClient(
-			ctx,
-			chainID,
-			light.TrustOptions{
-				Period: 4 * time.Hour,
-				Height: 2,
-				Hash:   diffHeader2.Hash(),
-			},
-			primary,
-			[]provider.Provider{primary},
-			trustedStore,
-			light.Logger(log.TestingLogger()),
-		)
-		require.NoError(t, err)
-
-		// Check we no longer have the invalid 1st header (+header+).
-		l, err := c.TrustedLightBlock(1)
-		assert.Error(t, err)
-		assert.Nil(t, l)
-	}
-}
-
-// trustedHeader.Height > options.Height
-func TestClientRestoresTrustedHeaderAfterStartup3(t *testing.T) {
-	// 1. options.Hash == trustedHeader.Hash
-	{
-		// load the first three headers into the trusted store
-		trustedStore := dbs.New(dbm.NewMemDB())
-		err := trustedStore.SaveLightBlock(l1)
-		require.NoError(t, err)
-
-		err = trustedStore.SaveLightBlock(l2)
-		require.NoError(t, err)
-
-		c, err := light.NewClient(
-			ctx,
-			chainID,
-			trustOptions,
-			fullNode,
-			[]provider.Provider{fullNode},
-			trustedStore,
-			light.Logger(log.TestingLogger()),
-		)
-		require.NoError(t, err)
-
-		// Check we still have the 1st light block.
-		l, err := c.TrustedLightBlock(1)
-		assert.NoError(t, err)
-		assert.NotNil(t, l)
-		assert.Equal(t, l.Hash(), h1.Hash())
-		assert.NoError(t, l.ValidateBasic(chainID))
-
-		// Check we no longer have 2nd light block.
-		l, err = c.TrustedLightBlock(2)
-		assert.Error(t, err)
-		assert.Nil(t, l)
-
-		l, err = c.TrustedLightBlock(3)
-		assert.Error(t, err)
-		assert.Nil(t, l)
-	}
-
-	// 2. options.Hash != trustedHeader.Hash
-	// This could happen if previous provider was lying to us.
-	{
-		trustedStore := dbs.New(dbm.NewMemDB())
-		err := trustedStore.SaveLightBlock(l1)
-		require.NoError(t, err)
-
-		// header1 != header
-		header1 := keys.GenSignedHeader(chainID, 1, bTime.Add(1*time.Hour), nil, vals, vals,
-			hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys))
-
-		header2 := keys.GenSignedHeader(chainID, 2, bTime.Add(2*time.Hour), nil, vals, vals,
-			hash("app_hash"), hash("cons_hash"), hash("results_hash"), 0, len(keys))
-		err = trustedStore.SaveLightBlock(&types.LightBlock{
-			SignedHeader: header2,
-			ValidatorSet: vals,
-		})
-		require.NoError(t, err)
-
-		primary := mockp.New(
-			chainID,
-			map[int64]*types.SignedHeader{
-				1: header1,
-			},
-			valSet,
-		)
-
-		c, err := light.NewClient(
-			ctx,
-			chainID,
-			light.TrustOptions{
-				Period: 4 * time.Hour,
-				Height: 1,
-				Hash:   header1.Hash(),
-			},
-			primary,
-			[]provider.Provider{primary},
-			trustedStore,
-			light.Logger(log.TestingLogger()),
-		)
-		require.NoError(t, err)
-
-		// Check we have swapped invalid 1st light block (+lightblock+) with correct one (+lightblock2+).
-		l, err := c.TrustedLightBlock(1)
-		assert.NoError(t, err)
-		assert.NotNil(t, l)
-		assert.Equal(t, l.Hash(), header1.Hash())
-		assert.NoError(t, l.ValidateBasic(chainID))
-
-		// Check we no longer have invalid 2nd light block (+lightblock2+).
-		l, err = c.TrustedLightBlock(2)
-		assert.Error(t, err)
-		assert.Nil(t, l)
-	}
-}
-
 func TestClient_Update(t *testing.T) {
 	c, err := light.NewClient(
 		ctx,