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batch_verification.go
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batch_verification.go
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package signature
import (
"github.com/oasisprotocol/curve25519-voi/primitives/ed25519"
)
// BatchVerifier accumulates batch entries with Add, before performing
// batch verification with Verify.
type BatchVerifier struct {
verifier *ed25519.BatchVerifier
results []error
resultsMap map[int]int // verifier -> results mapping
hasError bool
}
// Reset resets a batch for reuse.
//
// Note: This method will reuse the internal entires slice to reduce memory
// reallocations. If the next batch is known to be significantly smaller
// it may be more memory efficient to simply create a new batch.
func (v *BatchVerifier) Reset() {
switch v.verifier {
case nil:
v.verifier = ed25519.NewBatchVerifier()
default:
v.verifier.Reset()
}
v.results = v.results[:0]
v.resultsMap = make(map[int]int)
v.hasError = false
}
// Add adds a (public key, context, message, signature) quad to the current
// batch.
//
// Note: Errors detected while preparing a entry for the validator will
// be stored in the verifier state, to be returned when the verification
// is done.
func (v *BatchVerifier) Add(
publicKey PublicKey,
context Context,
message []byte,
sig []byte,
) {
if v.resultsMap == nil {
v.Reset()
}
// In some cases we can skip doing the verification entirely, in
// which case, we pre-emptively tag the entry as a failure, and
// don't bother adding it to the actual batch verifier.
pushResult := func(err error) {
resIndex := len(v.results)
verIndex := len(v.resultsMap)
v.results = append(v.results, err)
switch err {
case nil:
v.resultsMap[verIndex] = resIndex
default:
v.hasError = true
}
}
if len(sig) != SignatureSize {
pushResult(ErrMalformedSignature)
return
}
if publicKey.IsBlacklisted() {
pushResult(ErrForbiddenPublicKey)
return
}
// Prepare the context using our janky domain separation.
data, err := PrepareSignerMessage(context, message)
if err != nil {
pushResult(err)
return
}
// Everything seems sensible, add to the verifier.
cachingVerifier.AddWithOptions(v.verifier, publicKey[:], data, sig, defaultOptions)
pushResult(nil)
}
// AddError adds an invalid entry to the current batch. This is useful
// to simplify the process of creating and processing a batch.
func (v *BatchVerifier) AddError(err error) {
if v.resultsMap == nil {
v.Reset()
}
v.results = append(v.results, err)
v.hasError = true
}
// Verify checks all entries in the current batch, returning true if all
// entries in the current batch are valid. If one or more signature is
// invalid, the returned error vector will provide information about
// each individual entry.
func (v *BatchVerifier) Verify() (bool, []error) {
if v.resultsMap == nil {
v.Reset()
}
allOk, validSigs := v.verifier.Verify(nil)
if !allOk {
switch len(v.resultsMap) {
case 0:
// This is a false negative. We don't always add to the batch,
// and the batch verifier treats verifying an empty batch as
// a failure.
allOk = true
default:
// Populate the signature verification failures.
for i, ok := range validSigs {
if !ok {
v.results[v.resultsMap[i]] = ErrVerifyFailed
}
}
}
}
// Copy so that nothing bad happens on verifier reuse.
ret := make([]error, 0, len(v.results))
ret = append(ret, v.results...)
return allOk && !v.hasError, ret
}
// NewBatchVerfier creates an empty BatchVerifier.
func NewBatchVerifier() *BatchVerifier {
return &BatchVerifier{
verifier: ed25519.NewBatchVerifier(),
resultsMap: make(map[int]int),
}
}
// NewBatchVerifierWithCapacity creates an empty BatchVerifier, with
// preallocations for a pre-determined batch size hint.
func NewBatchVerifierWithCapacity(n int) *BatchVerifier {
return &BatchVerifier{
verifier: ed25519.NewBatchVerifierWithCapacity(n),
results: make([]error, 0, n),
resultsMap: make(map[int]int),
}
}