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136 lines
3.7 KiB
136 lines
3.7 KiB
package lite
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import (
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"bytes"
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"time"
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"github.com/pkg/errors"
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tmmath "github.com/tendermint/tendermint/libs/math"
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"github.com/tendermint/tendermint/types"
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)
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var (
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// DefaultTrustLevel - new header can be trusted if at least one correct old
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// validator signed it.
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DefaultTrustLevel = tmmath.Fraction{Numerator: 1, Denominator: 3}
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)
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// Verify verifies the new header (h2) against the old header (h1). It ensures that:
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//
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// a) h1 can still be trusted (if not, ErrOldHeaderExpired is returned);
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// b) h2 is valid;
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// c) either h2.ValidatorsHash equals h1NextVals.Hash()
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// OR trustLevel ([1/3, 1]) of last trusted validators (h1NextVals) signed
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// correctly (if not, ErrNewValSetCantBeTrusted is returned);
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// c) more than 2/3 of new validators (h2Vals) have signed h2 (if not,
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// ErrNotEnoughVotingPowerSigned is returned).
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func Verify(
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chainID string,
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h1 *types.SignedHeader,
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h1NextVals *types.ValidatorSet,
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h2 *types.SignedHeader,
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h2Vals *types.ValidatorSet,
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trustingPeriod time.Duration,
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now time.Time,
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trustLevel tmmath.Fraction) error {
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if err := ValidateTrustLevel(trustLevel); err != nil {
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return err
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}
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// Ensure last header can still be trusted.
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if HeaderExpired(h1, trustingPeriod, now) {
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return ErrOldHeaderExpired{h1.Time.Add(trustingPeriod), now}
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}
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if err := verifyNewHeaderAndVals(chainID, h2, h2Vals, h1, now); err != nil {
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return err
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}
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if h2.Height == h1.Height+1 {
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if !bytes.Equal(h2.ValidatorsHash, h1NextVals.Hash()) {
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err := errors.Errorf("expected old header next validators (%X) to match those from new header (%X)",
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h1NextVals.Hash(),
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h2.ValidatorsHash,
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)
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return err
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}
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} else {
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// Ensure that +`trustLevel` (default 1/3) or more of last trusted validators signed correctly.
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err := h1NextVals.VerifyCommitTrusting(chainID, h2.Commit.BlockID, h2.Height, h2.Commit, trustLevel)
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if err != nil {
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switch e := err.(type) {
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case types.ErrNotEnoughVotingPowerSigned:
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return ErrNewValSetCantBeTrusted{e}
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default:
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return e
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}
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}
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}
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// Ensure that +2/3 of new validators signed correctly.
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err := h2Vals.VerifyCommit(chainID, h2.Commit.BlockID, h2.Height, h2.Commit)
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if err != nil {
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return err
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}
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return nil
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}
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func verifyNewHeaderAndVals(
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chainID string,
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h2 *types.SignedHeader,
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h2Vals *types.ValidatorSet,
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h1 *types.SignedHeader,
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now time.Time) error {
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if err := h2.ValidateBasic(chainID); err != nil {
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return errors.Wrap(err, "h2.ValidateBasic failed")
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}
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if h2.Height <= h1.Height {
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return errors.Errorf("expected new header height %d to be greater than one of old header %d",
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h2.Height,
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h1.Height)
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}
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if !h2.Time.After(h1.Time) {
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return errors.Errorf("expected new header time %v to be after old header time %v",
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h2.Time,
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h1.Time)
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}
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if !h2.Time.Before(now) {
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return errors.Errorf("new header has a time from the future %v (now: %v)",
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h2.Time,
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now)
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}
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if !bytes.Equal(h2.ValidatorsHash, h2Vals.Hash()) {
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return errors.Errorf("expected new header validators (%X) to match those that were supplied (%X)",
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h2.ValidatorsHash,
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h2Vals.Hash(),
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)
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}
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return nil
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}
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// ValidateTrustLevel checks that trustLevel is within the allowed range [1/3,
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// 1]. If not, it returns an error. 1/3 is the minimum amount of trust needed
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// which does not break the security model.
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func ValidateTrustLevel(lvl tmmath.Fraction) error {
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if lvl.Numerator*3 < lvl.Denominator || // < 1/3
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lvl.Numerator > lvl.Denominator || // > 1
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lvl.Denominator == 0 {
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return errors.Errorf("trustLevel must be within [1/3, 1], given %v", lvl)
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}
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return nil
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}
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// HeaderExpired return true if the given header expired.
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func HeaderExpired(h *types.SignedHeader, trustingPeriod time.Duration, now time.Time) bool {
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expirationTime := h.Time.Add(trustingPeriod)
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return !expirationTime.After(now)
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}
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