witness

Documentation

Overview

Package witness is designed to make sure the checkpoints of verifiable logs are consistent and store/serve/sign them if so. It is expected that a separate feeder component would be responsible for the actual interaction with logs.

Index

• type LogInfo
• type Opts
• type Proof
  • func (p Proof) Marshal() string
  • func (p *Proof) Unmarshal(data []byte) error
• type Witness
  • func New(wo Opts) (*Witness, error)
  • func (w *Witness) GetCheckpoint(logID string) ([]byte, error)
  • func (w *Witness) GetLogs() ([]string, error)
  • func (w *Witness) Update(ctx context.Context, logID string, nextRaw []byte, cProof [][]byte) ([]byte, error)

Types

type LogInfo

type LogInfo struct {
	// The verifier for signatures from the log.
	SigV note.Verifier
	// The expected Origin string in the checkpoints.
	Origin string
	// The hash strategy that should be used in verifying consistency.
	Hasher merkle.LogHasher
}

LogInfo contains the information needed to verify log checkpoints.

type Opts

type Opts struct {
	Persistence persistence.LogStatePersistence
	Signers     []note.Signer
	KnownLogs   map[string]LogInfo
}

Opts is the options passed to a witness.

type Proof

type Proof [][]byte

Proof represents a common format proof.

Interpretation of the proof bytes is ecosystem dependent.

func (Proof) Marshal

func (p Proof) Marshal() string

Marshal returns the common format representation of this proof.

func (*Proof) Unmarshal

func (p *Proof) Unmarshal(data []byte) error

Unmarshal parses common proof format data and stores the result in the Proof struct.

type Witness

type Witness struct {
	Signers []note.Signer
	// At some point we might want to store this information in a table in
	// the database too but as I imagine it being populated from a static
	// config file it doesn't seem very urgent to do that.
	Logs map[string]LogInfo
	// contains filtered or unexported fields
}

Witness consists of a database for storing checkpoints, a signer, and a list of logs for which it stores and verifies checkpoints.

func New

func New(wo Opts) (*Witness, error)

New creates a new witness, which initially has no logs to follow.

func (*Witness) GetCheckpoint

func (w *Witness) GetCheckpoint(logID string) ([]byte, error)

GetCheckpoint gets a checkpoint for a given log, which is consistent with all other checkpoints for the same log signed by this witness.

func (*Witness) GetLogs

func (w *Witness) GetLogs() ([]string, error)

GetLogs returns a list of all logs the witness is aware of.

func (*Witness) Update

func (w *Witness) Update(ctx context.Context, logID string, nextRaw []byte, cProof [][]byte) ([]byte, error)

Update updates the latest checkpoint if nextRaw is consistent with the current latest one for this log.

It returns the latest cosigned checkpoint held by the witness, which is a signed version of nextRaw if the update was applied.

If an error occurs, this method will generally return an error with a status code: - codes.NotFound if the log is unknown - codes.InvalidArgument for general bad requests - codes.AlreadyExists if the checkpoint is smaller than the one the witness knows - codes.FailedPrecondition if the checkpoint is inconsistent with the one the witness knows