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1114 lines
37 KiB
1114 lines
37 KiB
package light
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import (
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"bytes"
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"context"
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"errors"
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"fmt"
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"sort"
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"sync"
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"time"
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"github.com/tendermint/tendermint/libs/log"
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tmmath "github.com/tendermint/tendermint/libs/math"
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tmsync "github.com/tendermint/tendermint/libs/sync"
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"github.com/tendermint/tendermint/light/provider"
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"github.com/tendermint/tendermint/light/store"
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"github.com/tendermint/tendermint/types"
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)
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type mode byte
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const (
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sequential mode = iota + 1
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skipping
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defaultPruningSize = 1000
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// For verifySkipping, when using the cache of headers from the previous batch,
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// they will always be at a height greater than 1/2 (normal verifySkipping) so to
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// find something in between the range, 9/16 is used.
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verifySkippingNumerator = 9
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verifySkippingDenominator = 16
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// 10s should cover most of the clients.
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// References:
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// - http://vancouver-webpages.com/time/web.html
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// - https://blog.codinghorror.com/keeping-time-on-the-pc/
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defaultMaxClockDrift = 10 * time.Second
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)
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// Option sets a parameter for the light client.
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type Option func(*Client)
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// SequentialVerification option configures the light client to sequentially
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// check the blocks (every block, in ascending height order). Note this is
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// much slower than SkippingVerification, albeit more secure.
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func SequentialVerification() Option {
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return func(c *Client) {
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c.verificationMode = sequential
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}
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}
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// SkippingVerification option configures the light client to skip blocks as
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// long as {trustLevel} of the old validator set signed the new header. The
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// verifySkipping algorithm from the specification is used for finding the minimal
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// "trust path".
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//
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// trustLevel - fraction of the old validator set (in terms of voting power),
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// which must sign the new header in order for us to trust it. NOTE this only
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// applies to non-adjacent headers. For adjacent headers, sequential
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// verification is used.
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func SkippingVerification(trustLevel tmmath.Fraction) Option {
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return func(c *Client) {
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c.verificationMode = skipping
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c.trustLevel = trustLevel
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}
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}
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// PruningSize option sets the maximum amount of light blocks that the light
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// client stores. When Prune() is run, all light blocks that are earlier than
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// the h amount of light blocks will be removed from the store.
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// Default: 1000. A pruning size of 0 will not prune the light client at all.
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func PruningSize(h uint16) Option {
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return func(c *Client) {
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c.pruningSize = h
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}
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}
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// ConfirmationFunction option can be used to prompt to confirm an action. For
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// example, remove newer headers if the light client is being reset with an
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// older header. No confirmation is required by default!
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func ConfirmationFunction(fn func(action string) bool) Option {
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return func(c *Client) {
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c.confirmationFn = fn
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}
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}
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// Logger option can be used to set a logger for the client.
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func Logger(l log.Logger) Option {
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return func(c *Client) {
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c.logger = l
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}
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}
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// MaxClockDrift defines how much new header's time can drift into
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// the future. Default: 10s.
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func MaxClockDrift(d time.Duration) Option {
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return func(c *Client) {
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c.maxClockDrift = d
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}
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}
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// Client represents a light client, connected to a single chain, which gets
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// light blocks from a primary provider, verifies them either sequentially or by
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// skipping some and stores them in a trusted store (usually, a local FS).
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//
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// Default verification: SkippingVerification(DefaultTrustLevel)
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type Client struct {
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chainID string
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trustingPeriod time.Duration // see TrustOptions.Period
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verificationMode mode
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trustLevel tmmath.Fraction
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maxClockDrift time.Duration
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// Mutex for locking during changes of the light clients providers
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providerMutex tmsync.Mutex
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// Primary provider of new headers.
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primary provider.Provider
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// Providers used to "witness" new headers.
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witnesses []provider.Provider
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// Where trusted light blocks are stored.
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trustedStore store.Store
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// Highest trusted light block from the store (height=H).
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latestTrustedBlock *types.LightBlock
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// See RemoveNoLongerTrustedHeadersPeriod option
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pruningSize uint16
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// See ConfirmationFunction option
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confirmationFn func(action string) bool
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// The light client keeps track of how many times it has requested a light
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// block from it's providers. When this exceeds the amount of witnesses the
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// light client will just return the last error sent by the providers
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// repeatRequests uint16
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logger log.Logger
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}
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// NewClient returns a new light client. It returns an error if it fails to
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// obtain the light block from the primary or they are invalid (e.g. trust
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// hash does not match with the one from the headers).
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//
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// Witnesses are providers, which will be used for cross-checking the primary
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// provider. At least one witness must be given when skipping verification is
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// used (default). A witness can become a primary iff the current primary is
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// unavailable.
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//
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// See all Option(s) for the additional configuration.
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func NewClient(
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ctx context.Context,
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chainID string,
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trustOptions TrustOptions,
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primary provider.Provider,
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witnesses []provider.Provider,
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trustedStore store.Store,
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options ...Option) (*Client, error) {
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if err := trustOptions.ValidateBasic(); err != nil {
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return nil, fmt.Errorf("invalid TrustOptions: %w", err)
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}
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c, err := NewClientFromTrustedStore(chainID, trustOptions.Period, primary, witnesses, trustedStore, options...)
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if err != nil {
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return nil, err
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}
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if c.latestTrustedBlock != nil {
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c.logger.Info("checking trusted light block using options")
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if err := c.checkTrustedHeaderUsingOptions(ctx, trustOptions); err != nil {
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return nil, err
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}
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}
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if c.latestTrustedBlock == nil || c.latestTrustedBlock.Height < trustOptions.Height {
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c.logger.Info("downloading trusted light block using options")
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if err := c.initializeWithTrustOptions(ctx, trustOptions); err != nil {
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return nil, err
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}
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}
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return c, err
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}
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// NewClientFromTrustedStore initializes existing client from the trusted store.
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//
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// See NewClient
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func NewClientFromTrustedStore(
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chainID string,
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trustingPeriod time.Duration,
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primary provider.Provider,
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witnesses []provider.Provider,
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trustedStore store.Store,
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options ...Option) (*Client, error) {
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c := &Client{
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chainID: chainID,
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trustingPeriod: trustingPeriod,
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verificationMode: skipping,
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trustLevel: DefaultTrustLevel,
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maxClockDrift: defaultMaxClockDrift,
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primary: primary,
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witnesses: witnesses,
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trustedStore: trustedStore,
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pruningSize: defaultPruningSize,
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confirmationFn: func(action string) bool { return true },
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logger: log.NewNopLogger(),
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}
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for _, o := range options {
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o(c)
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}
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// Validate the number of witnesses.
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if len(c.witnesses) < 1 {
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return nil, ErrNoWitnesses
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}
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// Validate trust level.
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if err := ValidateTrustLevel(c.trustLevel); err != nil {
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return nil, err
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}
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if err := c.restoreTrustedLightBlock(); err != nil {
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return nil, err
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}
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return c, nil
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}
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// restoreTrustedLightBlock loads the latest trusted light block from the store
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func (c *Client) restoreTrustedLightBlock() error {
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lastHeight, err := c.trustedStore.LastLightBlockHeight()
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if err != nil {
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return fmt.Errorf("can't get last trusted light block height: %w", err)
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}
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if lastHeight > 0 {
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trustedBlock, err := c.trustedStore.LightBlock(lastHeight)
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if err != nil {
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return fmt.Errorf("can't get last trusted light block: %w", err)
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}
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c.latestTrustedBlock = trustedBlock
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c.logger.Info("restored trusted light block", "height", lastHeight)
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}
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return nil
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}
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// if options.Height:
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//
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// 1) ahead of trustedLightBlock.Height => fetch light blocks (same height as
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// trustedLightBlock) from primary provider and check it's hash matches the
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// trustedLightBlock's hash (if not, remove trustedLightBlock and all the light blocks
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// before)
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//
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// 2) equals trustedLightBlock.Height => check options.Hash matches the
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// trustedLightBlock's hash (if not, remove trustedLightBlock and all the light blocks
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// before)
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//
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// 3) behind trustedLightBlock.Height => remove all the light blocks between
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// options.Height and trustedLightBlock.Height, update trustedLightBlock, then
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// check options.Hash matches the trustedLightBlock's hash (if not, remove
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// trustedLightBlock and all the light blocks before)
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//
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// The intuition here is the user is always right. I.e. if she decides to reset
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// the light client with an older header, there must be a reason for it.
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func (c *Client) checkTrustedHeaderUsingOptions(ctx context.Context, options TrustOptions) error {
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var primaryHash []byte
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switch {
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case options.Height > c.latestTrustedBlock.Height:
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h, err := c.lightBlockFromPrimary(ctx, c.latestTrustedBlock.Height)
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if err != nil {
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return err
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}
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primaryHash = h.Hash()
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case options.Height == c.latestTrustedBlock.Height:
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primaryHash = options.Hash
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case options.Height < c.latestTrustedBlock.Height:
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c.logger.Info("client initialized with old header (trusted is more recent)",
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"old", options.Height,
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"trustedHeight", c.latestTrustedBlock.Height,
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"trustedHash", c.latestTrustedBlock.Hash())
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action := fmt.Sprintf(
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"Rollback to %d (%X)? Note this will remove newer light blocks up to %d (%X)",
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options.Height, options.Hash,
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c.latestTrustedBlock.Height, c.latestTrustedBlock.Hash())
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if c.confirmationFn(action) {
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// remove all the headers (options.Height, trustedHeader.Height]
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err := c.cleanupAfter(options.Height)
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if err != nil {
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return fmt.Errorf("cleanupAfter(%d): %w", options.Height, err)
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}
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c.logger.Info("Rolled back to older header (newer headers were removed)",
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"old", options.Height)
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} else {
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return nil
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}
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primaryHash = options.Hash
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}
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if !bytes.Equal(primaryHash, c.latestTrustedBlock.Hash()) {
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c.logger.Info("previous trusted header's hash (h1) doesn't match hash from primary provider (h2)",
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"h1", c.latestTrustedBlock.Hash(), "h2", primaryHash)
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action := fmt.Sprintf(
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"Previous trusted header's hash %X doesn't match hash %X from primary provider. Remove all the stored light blocks?",
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c.latestTrustedBlock.Hash(), primaryHash)
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if c.confirmationFn(action) {
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err := c.Cleanup()
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if err != nil {
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return fmt.Errorf("failed to cleanup: %w", err)
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}
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} else {
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return errors.New("refused to remove the stored light blocks despite hashes mismatch")
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}
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}
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return nil
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}
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// initializeWithTrustOptions fetches the weakly-trusted light block from
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// primary provider.
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func (c *Client) initializeWithTrustOptions(ctx context.Context, options TrustOptions) error {
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// 1) Fetch and verify the light block.
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l, err := c.lightBlockFromPrimary(ctx, options.Height)
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if err != nil {
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return err
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}
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// NOTE: - Verify func will check if it's expired or not.
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// - h.Time is not being checked against time.Now() because we don't
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// want to add yet another argument to NewClient* functions.
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if err := l.ValidateBasic(c.chainID); err != nil {
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return err
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}
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if !bytes.Equal(l.Hash(), options.Hash) {
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return fmt.Errorf("expected header's hash %X, but got %X", options.Hash, l.Hash())
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}
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// 2) Ensure that +2/3 of validators signed correctly.
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err = l.ValidatorSet.VerifyCommitLight(c.chainID, l.Commit.BlockID, l.Height, l.Commit)
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if err != nil {
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return fmt.Errorf("invalid commit: %w", err)
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}
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// 3) Cross-verify with witnesses to ensure everybody has the same state.
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if err := c.compareFirstHeaderWithWitnesses(ctx, l.SignedHeader); err != nil {
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return err
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}
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// 4) Persist both of them and continue.
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return c.updateTrustedLightBlock(l)
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}
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// TrustedLightBlock returns a trusted light block at the given height (0 - the latest).
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//
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// It returns an error if:
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// - there are some issues with the trusted store, although that should not
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// happen normally;
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// - negative height is passed;
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// - header has not been verified yet and is therefore not in the store
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//
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// Safe for concurrent use by multiple goroutines.
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func (c *Client) TrustedLightBlock(height int64) (*types.LightBlock, error) {
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height, err := c.compareWithLatestHeight(height)
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if err != nil {
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return nil, err
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}
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return c.trustedStore.LightBlock(height)
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}
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func (c *Client) compareWithLatestHeight(height int64) (int64, error) {
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latestHeight, err := c.LastTrustedHeight()
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if err != nil {
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return 0, fmt.Errorf("can't get last trusted height: %w", err)
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}
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if latestHeight == -1 {
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return 0, errors.New("no headers exist")
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}
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switch {
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case height > latestHeight:
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return 0, fmt.Errorf("unverified header/valset requested (latest: %d)", latestHeight)
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case height == 0:
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return latestHeight, nil
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case height < 0:
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return 0, errors.New("negative height")
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}
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return height, nil
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}
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// Update attempts to advance the state by downloading the latest light
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// block and verifying it. It returns a new light block on a successful
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// update. Otherwise, it returns nil (plus an error, if any).
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func (c *Client) Update(ctx context.Context, now time.Time) (*types.LightBlock, error) {
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lastTrustedHeight, err := c.LastTrustedHeight()
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if err != nil {
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return nil, fmt.Errorf("can't get last trusted height: %w", err)
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}
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if lastTrustedHeight == -1 {
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// no light blocks yet => wait
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return nil, nil
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}
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latestBlock, err := c.lightBlockFromPrimary(ctx, 0)
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if err != nil {
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return nil, err
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}
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if latestBlock.Height > lastTrustedHeight {
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err = c.verifyLightBlock(ctx, latestBlock, now)
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if err != nil {
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return nil, err
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}
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c.logger.Info("advanced to new state", "height", latestBlock.Height, "hash", latestBlock.Hash())
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return latestBlock, nil
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}
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return nil, nil
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}
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|
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// VerifyLightBlockAtHeight fetches the light block at the given height
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// and verifies it. It returns the block immediately if it exists in
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// the trustedStore (no verification is needed).
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//
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// height must be > 0.
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//
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// It returns provider.ErrlightBlockNotFound if light block is not found by
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// primary.
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//
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// It will replace the primary provider if an error from a request to the provider occurs
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func (c *Client) VerifyLightBlockAtHeight(ctx context.Context, height int64, now time.Time) (*types.LightBlock, error) {
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if height <= 0 {
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return nil, errors.New("negative or zero height")
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}
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// Check if the light block is already verified.
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h, err := c.TrustedLightBlock(height)
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if err == nil {
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c.logger.Debug("header has already been verified", "height", height, "hash", h.Hash())
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// Return already trusted light block
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return h, nil
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}
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|
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// Request the light block from primary
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l, err := c.lightBlockFromPrimary(ctx, height)
|
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if err != nil {
|
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return nil, err
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}
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|
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return l, c.verifyLightBlock(ctx, l, now)
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}
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|
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// VerifyHeader verifies a new header against the trusted state. It returns
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// immediately if newHeader exists in trustedStore (no verification is
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// needed). Else it performs one of the two types of verification:
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//
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// SequentialVerification: verifies that 2/3 of the trusted validator set has
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// signed the new header. If the headers are not adjacent, **all** intermediate
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// headers will be requested. Intermediate headers are not saved to database.
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//
|
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// SkippingVerification(trustLevel): verifies that {trustLevel} of the trusted
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// validator set has signed the new header. If it's not the case and the
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// headers are not adjacent, verifySkipping is performed and necessary (not all)
|
|
// intermediate headers will be requested. See the specification for details.
|
|
// Intermediate headers are not saved to database.
|
|
// https://github.com/tendermint/spec/blob/master/spec/consensus/light-client.md
|
|
//
|
|
// If the header, which is older than the currently trusted header, is
|
|
// requested and the light client does not have it, VerifyHeader will perform:
|
|
// a) verifySkipping verification if nearest trusted header is found & not expired
|
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// b) backwards verification in all other cases
|
|
//
|
|
// It returns ErrOldHeaderExpired if the latest trusted header expired.
|
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//
|
|
// If the primary provides an invalid header (ErrInvalidHeader), it is rejected
|
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// and replaced by another provider until all are exhausted.
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//
|
|
// If, at any moment, a LightBlock is not found by the primary provider as part of
|
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// verification then the provider will be replaced by another and the process will
|
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// restart.
|
|
func (c *Client) VerifyHeader(ctx context.Context, newHeader *types.Header, now time.Time) error {
|
|
if newHeader == nil {
|
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return errors.New("nil header")
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}
|
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if newHeader.Height <= 0 {
|
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return errors.New("negative or zero height")
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}
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|
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// Check if newHeader already verified.
|
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l, err := c.TrustedLightBlock(newHeader.Height)
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if err == nil {
|
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// Make sure it's the same header.
|
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if !bytes.Equal(l.Hash(), newHeader.Hash()) {
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return fmt.Errorf("existing trusted header %X does not match newHeader %X", l.Hash(), newHeader.Hash())
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}
|
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c.logger.Debug("header has already been verified",
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"height", newHeader.Height, "hash", newHeader.Hash())
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return nil
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}
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|
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// Request the header and the vals.
|
|
l, err = c.lightBlockFromPrimary(ctx, newHeader.Height)
|
|
if err != nil {
|
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return fmt.Errorf("failed to retrieve light block from primary to verify against: %w", err)
|
|
}
|
|
|
|
if !bytes.Equal(l.Hash(), newHeader.Hash()) {
|
|
return fmt.Errorf("light block header %X does not match newHeader %X", l.Hash(), newHeader.Hash())
|
|
}
|
|
|
|
return c.verifyLightBlock(ctx, l, now)
|
|
}
|
|
|
|
func (c *Client) verifyLightBlock(ctx context.Context, newLightBlock *types.LightBlock, now time.Time) error {
|
|
c.logger.Info("verify light block", "height", newLightBlock.Height, "hash", newLightBlock.Hash())
|
|
|
|
var (
|
|
verifyFunc func(ctx context.Context, trusted *types.LightBlock, new *types.LightBlock, now time.Time) error
|
|
err error
|
|
)
|
|
|
|
switch c.verificationMode {
|
|
case sequential:
|
|
verifyFunc = c.verifySequential
|
|
case skipping:
|
|
verifyFunc = c.verifySkippingAgainstPrimary
|
|
default:
|
|
panic(fmt.Sprintf("Unknown verification mode: %b", c.verificationMode))
|
|
}
|
|
|
|
firstBlockHeight, err := c.FirstTrustedHeight()
|
|
if err != nil {
|
|
return fmt.Errorf("can't get first light block height: %w", err)
|
|
}
|
|
|
|
switch {
|
|
// Verifying forwards
|
|
case newLightBlock.Height >= c.latestTrustedBlock.Height:
|
|
err = verifyFunc(ctx, c.latestTrustedBlock, newLightBlock, now)
|
|
|
|
// Verifying backwards
|
|
case newLightBlock.Height < firstBlockHeight:
|
|
var firstBlock *types.LightBlock
|
|
firstBlock, err = c.trustedStore.LightBlock(firstBlockHeight)
|
|
if err != nil {
|
|
return fmt.Errorf("can't get first light block: %w", err)
|
|
}
|
|
err = c.backwards(ctx, firstBlock.Header, newLightBlock.Header)
|
|
|
|
// Verifying between first and last trusted light block
|
|
default:
|
|
var closestBlock *types.LightBlock
|
|
closestBlock, err = c.trustedStore.LightBlockBefore(newLightBlock.Height)
|
|
if err != nil {
|
|
return fmt.Errorf("can't get signed header before height %d: %w", newLightBlock.Height, err)
|
|
}
|
|
err = verifyFunc(ctx, closestBlock, newLightBlock, now)
|
|
}
|
|
if err != nil {
|
|
c.logger.Error("failed to verify", "err", err)
|
|
return err
|
|
}
|
|
|
|
// Once verified, save and return
|
|
return c.updateTrustedLightBlock(newLightBlock)
|
|
}
|
|
|
|
// see VerifyHeader
|
|
func (c *Client) verifySequential(
|
|
ctx context.Context,
|
|
trustedBlock *types.LightBlock,
|
|
newLightBlock *types.LightBlock,
|
|
now time.Time) error {
|
|
|
|
var (
|
|
verifiedBlock = trustedBlock
|
|
interimBlock *types.LightBlock
|
|
err error
|
|
trace = []*types.LightBlock{trustedBlock}
|
|
)
|
|
|
|
for height := trustedBlock.Height + 1; height <= newLightBlock.Height; height++ {
|
|
// 1) Fetch interim light block if needed.
|
|
if height == newLightBlock.Height { // last light block
|
|
interimBlock = newLightBlock
|
|
} else { // intermediate light blocks
|
|
interimBlock, err = c.lightBlockFromPrimary(ctx, height)
|
|
if err != nil {
|
|
return ErrVerificationFailed{From: verifiedBlock.Height, To: height, Reason: err}
|
|
}
|
|
}
|
|
|
|
// 2) Verify them
|
|
c.logger.Debug("verify adjacent newLightBlock against verifiedBlock",
|
|
"trustedHeight", verifiedBlock.Height,
|
|
"trustedHash", verifiedBlock.Hash(),
|
|
"newHeight", interimBlock.Height,
|
|
"newHash", interimBlock.Hash())
|
|
|
|
err = VerifyAdjacent(verifiedBlock.SignedHeader, interimBlock.SignedHeader, interimBlock.ValidatorSet,
|
|
c.trustingPeriod, now, c.maxClockDrift)
|
|
if err != nil {
|
|
err := ErrVerificationFailed{From: verifiedBlock.Height, To: interimBlock.Height, Reason: err}
|
|
|
|
switch errors.Unwrap(err).(type) {
|
|
case ErrInvalidHeader:
|
|
// If the target header is invalid, return immediately.
|
|
if err.To == newLightBlock.Height {
|
|
c.logger.Debug("target header is invalid", "err", err)
|
|
return err
|
|
}
|
|
|
|
// If some intermediate header is invalid, remove the primary and try again.
|
|
c.logger.Error("primary sent invalid header -> removing", "err", err, "primary", c.primary)
|
|
|
|
replacementBlock, removeErr := c.findNewPrimary(ctx, newLightBlock.Height, true)
|
|
if removeErr != nil {
|
|
c.logger.Debug("failed to replace primary. Returning original error", "err", removeErr)
|
|
return err
|
|
}
|
|
|
|
if !bytes.Equal(replacementBlock.Hash(), newLightBlock.Hash()) {
|
|
c.logger.Debug("replaced primary but new primary has a different block to the initial one")
|
|
return err
|
|
}
|
|
|
|
// attempt to verify header again
|
|
height--
|
|
|
|
continue
|
|
default:
|
|
return err
|
|
}
|
|
}
|
|
|
|
// 3) Update verifiedBlock
|
|
verifiedBlock = interimBlock
|
|
|
|
// 4) Add verifiedBlock to trace
|
|
trace = append(trace, verifiedBlock)
|
|
}
|
|
|
|
// Compare header with the witnesses to ensure it's not a fork.
|
|
// More witnesses we have, more chance to notice one.
|
|
//
|
|
// CORRECTNESS ASSUMPTION: there's at least 1 correct full node
|
|
// (primary or one of the witnesses).
|
|
return c.detectDivergence(ctx, trace, now)
|
|
}
|
|
|
|
// see VerifyHeader
|
|
//
|
|
// verifySkipping finds the middle light block between a trusted and new light block,
|
|
// reiterating the action until it verifies a light block. A cache of light blocks
|
|
// requested from source is kept such that when a verification is made, and the
|
|
// light client tries again to verify the new light block in the middle, the light
|
|
// client does not need to ask for all the same light blocks again.
|
|
func (c *Client) verifySkipping(
|
|
ctx context.Context,
|
|
source provider.Provider,
|
|
trustedBlock *types.LightBlock,
|
|
newLightBlock *types.LightBlock,
|
|
now time.Time) ([]*types.LightBlock, error) {
|
|
|
|
var (
|
|
blockCache = []*types.LightBlock{newLightBlock}
|
|
depth = 0
|
|
|
|
verifiedBlock = trustedBlock
|
|
trace = []*types.LightBlock{trustedBlock}
|
|
)
|
|
|
|
for {
|
|
c.logger.Debug("verify non-adjacent newHeader against verifiedBlock",
|
|
"trustedHeight", verifiedBlock.Height,
|
|
"trustedHash", verifiedBlock.Hash(),
|
|
"newHeight", blockCache[depth].Height,
|
|
"newHash", blockCache[depth].Hash())
|
|
|
|
err := Verify(verifiedBlock.SignedHeader, verifiedBlock.ValidatorSet, blockCache[depth].SignedHeader,
|
|
blockCache[depth].ValidatorSet, c.trustingPeriod, now, c.maxClockDrift, c.trustLevel)
|
|
switch err.(type) {
|
|
case nil:
|
|
// Have we verified the last header
|
|
if depth == 0 {
|
|
trace = append(trace, newLightBlock)
|
|
return trace, nil
|
|
}
|
|
// If not, update the lower bound to the previous upper bound
|
|
verifiedBlock = blockCache[depth]
|
|
// Remove the light block at the lower bound in the header cache - it will no longer be needed
|
|
blockCache = blockCache[:depth]
|
|
// Reset the cache depth so that we start from the upper bound again
|
|
depth = 0
|
|
// add verifiedBlock to the trace
|
|
trace = append(trace, verifiedBlock)
|
|
|
|
case ErrNewValSetCantBeTrusted:
|
|
// do add another header to the end of the cache
|
|
if depth == len(blockCache)-1 {
|
|
pivotHeight := verifiedBlock.Height + (blockCache[depth].Height-verifiedBlock.
|
|
Height)*verifySkippingNumerator/verifySkippingDenominator
|
|
interimBlock, providerErr := source.LightBlock(ctx, pivotHeight)
|
|
switch providerErr {
|
|
case nil:
|
|
blockCache = append(blockCache, interimBlock)
|
|
|
|
// if the error is benign, the client does not need to replace the primary
|
|
case provider.ErrLightBlockNotFound, provider.ErrNoResponse:
|
|
return nil, err
|
|
|
|
// all other errors such as ErrBadLightBlock or ErrUnreliableProvider are seen as malevolent and the
|
|
// provider is removed
|
|
default:
|
|
return nil, ErrVerificationFailed{From: verifiedBlock.Height, To: pivotHeight, Reason: providerErr}
|
|
}
|
|
|
|
}
|
|
depth++
|
|
|
|
default:
|
|
return nil, ErrVerificationFailed{From: verifiedBlock.Height, To: blockCache[depth].Height, Reason: err}
|
|
}
|
|
}
|
|
}
|
|
|
|
// verifySkippingAgainstPrimary does verifySkipping plus it compares new header with
|
|
// witnesses and replaces primary if it sends the light client an invalid header
|
|
func (c *Client) verifySkippingAgainstPrimary(
|
|
ctx context.Context,
|
|
trustedBlock *types.LightBlock,
|
|
newLightBlock *types.LightBlock,
|
|
now time.Time) error {
|
|
|
|
trace, err := c.verifySkipping(ctx, c.primary, trustedBlock, newLightBlock, now)
|
|
|
|
switch errors.Unwrap(err).(type) {
|
|
case ErrInvalidHeader:
|
|
// If the target header is invalid, return immediately.
|
|
invalidHeaderHeight := err.(ErrVerificationFailed).To
|
|
if invalidHeaderHeight == newLightBlock.Height {
|
|
c.logger.Debug("target header is invalid", "err", err)
|
|
return err
|
|
}
|
|
|
|
// If some intermediate header is invalid, remove the primary and try again.
|
|
c.logger.Error("primary sent invalid header -> replacing", "err", err, "primary", c.primary)
|
|
replacementBlock, removeErr := c.findNewPrimary(ctx, newLightBlock.Height, true)
|
|
if removeErr != nil {
|
|
c.logger.Error("failed to replace primary. Returning original error", "err", removeErr)
|
|
return err
|
|
}
|
|
|
|
if !bytes.Equal(replacementBlock.Hash(), newLightBlock.Hash()) {
|
|
c.logger.Debug("replaced primary but new primary has a different block to the initial one. Returning original error")
|
|
return err
|
|
}
|
|
|
|
// attempt to verify the header again
|
|
return c.verifySkippingAgainstPrimary(ctx, trustedBlock, replacementBlock, now)
|
|
case nil:
|
|
// Compare header with the witnesses to ensure it's not a fork.
|
|
// More witnesses we have, more chance to notice one.
|
|
//
|
|
// CORRECTNESS ASSUMPTION: there's at least 1 correct full node
|
|
// (primary or one of the witnesses).
|
|
if cmpErr := c.detectDivergence(ctx, trace, now); cmpErr != nil {
|
|
return cmpErr
|
|
}
|
|
default:
|
|
return err
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// LastTrustedHeight returns a last trusted height. -1 and nil are returned if
|
|
// there are no trusted headers.
|
|
//
|
|
// Safe for concurrent use by multiple goroutines.
|
|
func (c *Client) LastTrustedHeight() (int64, error) {
|
|
return c.trustedStore.LastLightBlockHeight()
|
|
}
|
|
|
|
// FirstTrustedHeight returns a first trusted height. -1 and nil are returned if
|
|
// there are no trusted headers.
|
|
//
|
|
// Safe for concurrent use by multiple goroutines.
|
|
func (c *Client) FirstTrustedHeight() (int64, error) {
|
|
return c.trustedStore.FirstLightBlockHeight()
|
|
}
|
|
|
|
// ChainID returns the chain ID the light client was configured with.
|
|
//
|
|
// Safe for concurrent use by multiple goroutines.
|
|
func (c *Client) ChainID() string {
|
|
return c.chainID
|
|
}
|
|
|
|
// Primary returns the primary provider.
|
|
//
|
|
// NOTE: provider may be not safe for concurrent access.
|
|
func (c *Client) Primary() provider.Provider {
|
|
c.providerMutex.Lock()
|
|
defer c.providerMutex.Unlock()
|
|
return c.primary
|
|
}
|
|
|
|
// Witnesses returns the witness providers.
|
|
//
|
|
// NOTE: providers may be not safe for concurrent access.
|
|
func (c *Client) Witnesses() []provider.Provider {
|
|
c.providerMutex.Lock()
|
|
defer c.providerMutex.Unlock()
|
|
return c.witnesses
|
|
}
|
|
|
|
// Cleanup removes all the data (headers and validator sets) stored. Note: the
|
|
// client must be stopped at this point.
|
|
func (c *Client) Cleanup() error {
|
|
c.logger.Info("removing all light blocks")
|
|
c.latestTrustedBlock = nil
|
|
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 {
|
|
if err := c.trustedStore.SaveLightBlock(l); err != nil {
|
|
return fmt.Errorf("failed to save trusted header: %w", err)
|
|
}
|
|
|
|
if c.pruningSize > 0 {
|
|
if err := c.trustedStore.Prune(c.pruningSize); err != nil {
|
|
return fmt.Errorf("prune: %w", err)
|
|
}
|
|
}
|
|
|
|
if c.latestTrustedBlock == nil || l.Height > c.latestTrustedBlock.Height {
|
|
c.latestTrustedBlock = l
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// backwards verification (see VerifyHeaderBackwards func in the spec) verifies
|
|
// headers before a trusted header. If a sent header is invalid the primary is
|
|
// replaced with another provider and the operation is repeated.
|
|
func (c *Client) backwards(
|
|
ctx context.Context,
|
|
trustedHeader *types.Header,
|
|
newHeader *types.Header) error {
|
|
|
|
var (
|
|
verifiedHeader = trustedHeader
|
|
interimHeader *types.Header
|
|
)
|
|
|
|
for verifiedHeader.Height > newHeader.Height {
|
|
interimBlock, err := c.lightBlockFromPrimary(ctx, verifiedHeader.Height-1)
|
|
if err != nil {
|
|
return fmt.Errorf("failed to obtain the header at height #%d: %w", verifiedHeader.Height-1, err)
|
|
}
|
|
interimHeader = interimBlock.Header
|
|
c.logger.Debug("verify newHeader against verifiedHeader",
|
|
"trustedHeight", verifiedHeader.Height,
|
|
"trustedHash", verifiedHeader.Hash(),
|
|
"newHeight", interimHeader.Height,
|
|
"newHash", interimHeader.Hash())
|
|
if err := VerifyBackwards(interimHeader, verifiedHeader); err != nil {
|
|
// verification has failed
|
|
c.logger.Error("backwards verification failed, replacing primary...", "err", err, "primary", c.primary)
|
|
|
|
// the client tries to see if it can get a witness to continue with the request
|
|
newPrimarysBlock, replaceErr := c.findNewPrimary(ctx, newHeader.Height, true)
|
|
if replaceErr != nil {
|
|
c.logger.Debug("failed to replace primary. Returning original error", "err", replaceErr)
|
|
return err
|
|
}
|
|
|
|
// before continuing we must check that they have the same target header to validate
|
|
if !bytes.Equal(newPrimarysBlock.Hash(), newHeader.Hash()) {
|
|
c.logger.Debug("replaced primary but new primary has a different block to the initial one")
|
|
// return the original error
|
|
return err
|
|
}
|
|
|
|
// try again with the new primary
|
|
return c.backwards(ctx, verifiedHeader, newPrimarysBlock.Header)
|
|
}
|
|
verifiedHeader = interimHeader
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
// lightBlockFromPrimary retrieves the lightBlock from the primary provider
|
|
// at the specified height. This method also handles provider behavior as follows:
|
|
//
|
|
// 1. If the provider does not respond or does not have the block, it tries again
|
|
// with a different provider
|
|
// 2. If all providers return the same error, the light client forwards the error to
|
|
// where the initial request came from
|
|
// 3. If the provider provides an invalid light block, is deemed unreliable or returns
|
|
// any other error, the primary is permanently dropped and is replaced by a witness.
|
|
func (c *Client) lightBlockFromPrimary(ctx context.Context, height int64) (*types.LightBlock, error) {
|
|
c.providerMutex.Lock()
|
|
l, err := c.primary.LightBlock(ctx, height)
|
|
c.providerMutex.Unlock()
|
|
|
|
switch err {
|
|
case nil:
|
|
// Everything went smoothly. We reset the lightBlockRequests and return the light block
|
|
return l, nil
|
|
|
|
case provider.ErrNoResponse, provider.ErrLightBlockNotFound:
|
|
// we find a new witness to replace the primary
|
|
c.logger.Debug("error from light block request from primary, replacing...", "error", err, "primary", c.primary)
|
|
return c.findNewPrimary(ctx, height, false)
|
|
|
|
default:
|
|
// The light client has most likely received either provider.ErrUnreliableProvider or provider.ErrBadLightBlock
|
|
// These errors mean that the light client should drop the primary and try with another provider instead
|
|
c.logger.Error("error from light block request from primary, removing...", "error", err, "primary", c.primary)
|
|
return c.findNewPrimary(ctx, height, true)
|
|
}
|
|
}
|
|
|
|
// NOTE: requires a providerMutex lock
|
|
func (c *Client) removeWitnesses(indexes []int) error {
|
|
// check that we will still have witnesses remaining
|
|
if len(c.witnesses) <= len(indexes) {
|
|
return ErrNoWitnesses
|
|
}
|
|
|
|
// we need to make sure that we remove witnesses by index in the reverse
|
|
// order so as to not affect the indexes themselves
|
|
sort.Ints(indexes)
|
|
for i := len(indexes) - 1; i >= 0; i-- {
|
|
c.witnesses[indexes[i]] = c.witnesses[len(c.witnesses)-1]
|
|
c.witnesses = c.witnesses[:len(c.witnesses)-1]
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
type witnessResponse struct {
|
|
lb *types.LightBlock
|
|
witnessIndex int
|
|
err error
|
|
}
|
|
|
|
// findNewPrimary concurrently sends a light block request, promoting the first witness to return
|
|
// a valid light block as the new primary. The remove option indicates whether the primary should be
|
|
// entire removed or just appended to the back of the witnesses list. This method also handles witness
|
|
// errors. If no witness is available, it returns the last error of the witness.
|
|
func (c *Client) findNewPrimary(ctx context.Context, height int64, remove bool) (*types.LightBlock, error) {
|
|
c.providerMutex.Lock()
|
|
defer c.providerMutex.Unlock()
|
|
|
|
if len(c.witnesses) <= 1 {
|
|
return nil, ErrNoWitnesses
|
|
}
|
|
|
|
var (
|
|
witnessResponsesC = make(chan witnessResponse, len(c.witnesses))
|
|
witnessesToRemove []int
|
|
lastError error
|
|
wg sync.WaitGroup
|
|
)
|
|
|
|
// send out a light block request to all witnesses
|
|
subctx, cancel := context.WithCancel(ctx)
|
|
defer cancel()
|
|
for index := range c.witnesses {
|
|
wg.Add(1)
|
|
go func(witnessIndex int, witnessResponsesC chan witnessResponse) {
|
|
defer wg.Done()
|
|
|
|
lb, err := c.witnesses[witnessIndex].LightBlock(subctx, height)
|
|
witnessResponsesC <- witnessResponse{lb, witnessIndex, err}
|
|
}(index, witnessResponsesC)
|
|
}
|
|
|
|
// process all the responses as they come in
|
|
for i := 0; i < cap(witnessResponsesC); i++ {
|
|
response := <-witnessResponsesC
|
|
switch response.err {
|
|
// success! We have found a new primary
|
|
case nil:
|
|
cancel() // cancel all remaining requests to other witnesses
|
|
|
|
wg.Wait() // wait for all goroutines to finish
|
|
|
|
// if we are not intending on removing the primary then append the old primary to the end of the witness slice
|
|
if !remove {
|
|
c.witnesses = append(c.witnesses, c.primary)
|
|
}
|
|
|
|
// promote respondent as the new primary
|
|
c.logger.Debug("found new primary", "primary", c.witnesses[response.witnessIndex])
|
|
c.primary = c.witnesses[response.witnessIndex]
|
|
|
|
// add promoted witness to the list of witnesses to be removed
|
|
witnessesToRemove = append(witnessesToRemove, response.witnessIndex)
|
|
|
|
// remove witnesses marked as bad (the client must do this before we alter the witness slice and change the indexes
|
|
// of witnesses). Removal is done in descending order
|
|
if err := c.removeWitnesses(witnessesToRemove); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// return the light block that new primary responded with
|
|
return response.lb, nil
|
|
|
|
// process benign errors by logging them only
|
|
case provider.ErrNoResponse, provider.ErrLightBlockNotFound:
|
|
lastError = response.err
|
|
c.logger.Debug("error on light block request from witness",
|
|
"error", response.err, "primary", c.witnesses[response.witnessIndex])
|
|
continue
|
|
|
|
// process malevolent errors like ErrUnreliableProvider and ErrBadLightBlock by removing the witness
|
|
default:
|
|
lastError = response.err
|
|
c.logger.Error("error on light block request from witness, removing...",
|
|
"error", response.err, "primary", c.witnesses[response.witnessIndex])
|
|
witnessesToRemove = append(witnessesToRemove, response.witnessIndex)
|
|
}
|
|
}
|
|
|
|
return nil, lastError
|
|
}
|
|
|
|
// compareFirstHeaderWithWitnesses concurrently compares h with all witnesses. If any
|
|
// witness reports a different header than h, the function returns an error.
|
|
func (c *Client) compareFirstHeaderWithWitnesses(ctx context.Context, h *types.SignedHeader) error {
|
|
compareCtx, cancel := context.WithCancel(ctx)
|
|
defer cancel()
|
|
|
|
c.providerMutex.Lock()
|
|
defer c.providerMutex.Unlock()
|
|
|
|
if len(c.witnesses) < 1 {
|
|
return ErrNoWitnesses
|
|
}
|
|
|
|
errc := make(chan error, len(c.witnesses))
|
|
for i, witness := range c.witnesses {
|
|
go c.compareNewHeaderWithWitness(compareCtx, errc, h, witness, i)
|
|
}
|
|
|
|
witnessesToRemove := make([]int, 0, len(c.witnesses))
|
|
|
|
// handle errors from the header comparisons as they come in
|
|
for i := 0; i < cap(errc); i++ {
|
|
err := <-errc
|
|
|
|
switch e := err.(type) {
|
|
case nil:
|
|
continue
|
|
case errConflictingHeaders:
|
|
c.logger.Error(fmt.Sprintf(`witness #%d has a different header. Please check primary is correct
|
|
and remove witness. Otherwise, use a different primary`, e.WitnessIndex), "witness", c.witnesses[e.WitnessIndex])
|
|
return err
|
|
case errBadWitness:
|
|
// If witness sent us an invalid header, then remove it. If it didn't
|
|
// respond or couldn't find the block, then we ignore it and move on to
|
|
// the next witness.
|
|
if _, ok := e.Reason.(provider.ErrBadLightBlock); ok {
|
|
c.logger.Info("Witness sent an invalid light block, removing...", "witness", c.witnesses[e.WitnessIndex])
|
|
witnessesToRemove = append(witnessesToRemove, e.WitnessIndex)
|
|
}
|
|
}
|
|
}
|
|
|
|
// remove all witnesses that misbehaved
|
|
return c.removeWitnesses(witnessesToRemove)
|
|
}
|