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96 lines
2.7 KiB
96 lines
2.7 KiB
package lite
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import (
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"github.com/tendermint/tendermint/types"
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liteErr "github.com/tendermint/tendermint/lite/errors"
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)
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var _ Certifier = (*DynamicCertifier)(nil)
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// DynamicCertifier uses a StaticCertifier for Certify, but adds an
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// Update method to allow for a change of validators.
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//
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// You can pass in a FullCommit with another validator set,
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// and if this is a provably secure transition (< 1/3 change,
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// sufficient signatures), then it will update the
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// validator set for the next Certify call.
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// For security, it will only follow validator set changes
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// going forward.
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type DynamicCertifier struct {
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cert *StaticCertifier
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lastHeight int64
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}
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// NewDynamic returns a new dynamic certifier.
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func NewDynamicCertifier(chainID string, vals *types.ValidatorSet, height int64) *DynamicCertifier {
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return &DynamicCertifier{
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cert: NewStaticCertifier(chainID, vals),
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lastHeight: height,
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}
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}
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// ChainID returns the chain id of this certifier.
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// Implements Certifier.
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func (dc *DynamicCertifier) ChainID() string {
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return dc.cert.ChainID()
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}
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// Validators returns the validators of this certifier.
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func (dc *DynamicCertifier) Validators() *types.ValidatorSet {
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return dc.cert.vSet
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}
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// Hash returns the hash of this certifier.
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func (dc *DynamicCertifier) Hash() []byte {
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return dc.cert.Hash()
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}
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// LastHeight returns the last height of this certifier.
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func (dc *DynamicCertifier) LastHeight() int64 {
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return dc.lastHeight
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}
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// Certify will verify whether the commit is valid and will update the height if it is or return an
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// error if it is not.
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// Implements Certifier.
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func (dc *DynamicCertifier) Certify(check Commit) error {
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err := dc.cert.Certify(check)
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if err == nil {
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// update last seen height if input is valid
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dc.lastHeight = check.Height()
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}
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return err
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}
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// Update will verify if this is a valid change and update
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// the certifying validator set if safe to do so.
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//
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// Returns an error if update is impossible (invalid proof or IsTooMuchChangeErr)
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func (dc *DynamicCertifier) Update(fc FullCommit) error {
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// ignore all checkpoints in the past -> only to the future
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h := fc.Height()
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if h <= dc.lastHeight {
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return liteErr.ErrPastTime()
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}
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// first, verify if the input is self-consistent....
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err := fc.ValidateBasic(dc.ChainID())
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if err != nil {
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return err
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}
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// now, make sure not too much change... meaning this commit
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// would be approved by the currently known validator set
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// as well as the new set
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commit := fc.Commit.Commit
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err = dc.Validators().VerifyCommitAny(fc.Validators, dc.ChainID(), commit.BlockID, h, commit)
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if err != nil {
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return liteErr.ErrTooMuchChange()
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}
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// looks good, we can update
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dc.cert = NewStaticCertifier(dc.ChainID(), fc.Validators)
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dc.lastHeight = h
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return nil
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}
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