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95 lines
2.5 KiB
95 lines
2.5 KiB
package light
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import (
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"github.com/tendermint/tendermint/types"
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lightErr "github.com/tendermint/tendermint/light/errors"
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)
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var _ Certifier = &Dynamic{}
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// Dynamic uses a Static 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 Dynamic struct {
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cert *Static
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lastHeight int
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}
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// NewDynamic returns a new dynamic certifier.
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func NewDynamic(chainID string, vals *types.ValidatorSet, height int) *Dynamic {
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return &Dynamic{
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cert: NewStatic(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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func (c *Dynamic) ChainID() string {
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return c.cert.ChainID()
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}
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// Validators returns the validators of this certifier.
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func (c *Dynamic) Validators() *types.ValidatorSet {
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return c.cert.vSet
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}
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// Hash returns the hash of this certifier.
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func (c *Dynamic) Hash() []byte {
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return c.cert.Hash()
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}
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// LastHeight returns the last height of this certifier.
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func (c *Dynamic) LastHeight() int {
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return c.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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func (c *Dynamic) Certify(check Commit) error {
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err := c.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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c.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 (c *Dynamic) 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 <= c.lastHeight {
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return lightErr.ErrPastTime()
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}
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// first, verify if the input is self-consistent....
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err := fc.ValidateBasic(c.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 = c.Validators().VerifyCommitAny(fc.Validators, c.ChainID(),
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commit.BlockID, h, commit)
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if err != nil {
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return lightErr.ErrTooMuchChange()
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}
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// looks good, we can update
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c.cert = NewStatic(c.ChainID(), fc.Validators)
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c.lastHeight = h
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return nil
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}
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