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