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verifier.go
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verifier.go
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package keccak
import (
"bytes"
"context"
"errors"
"fmt"
"io"
"github.com/ethereum-optimism/optimism/op-challenger/game/keccak/fetcher"
"github.com/ethereum-optimism/optimism/op-challenger/game/keccak/matrix"
keccakTypes "github.com/ethereum-optimism/optimism/op-challenger/game/keccak/types"
"github.com/ethereum-optimism/optimism/op-service/sources/batching/rpcblock"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/log"
lru "github.com/hashicorp/golang-lru/v2"
)
const validPreimageCacheSize = 500
type VerifierPreimageOracle interface {
fetcher.Oracle
GetProposalTreeRoot(ctx context.Context, block rpcblock.Block, ident keccakTypes.LargePreimageIdent) (common.Hash, error)
}
type Fetcher interface {
FetchInputs(ctx context.Context, blockHash common.Hash, oracle fetcher.Oracle, ident keccakTypes.LargePreimageIdent) ([]keccakTypes.InputData, error)
}
type PreimageVerifier struct {
log log.Logger
fetcher Fetcher
// knownValid caches the merkle tree roots that have been confirmed as valid.
// Invalid roots are not cached as those preimages will be ignored once the challenge is processed.
knownValid *lru.Cache[common.Hash, bool]
}
func NewPreimageVerifier(logger log.Logger, fetcher Fetcher) *PreimageVerifier {
// Can't error because size is hard coded
cache, _ := lru.New[common.Hash, bool](validPreimageCacheSize)
return &PreimageVerifier{
log: logger,
fetcher: fetcher,
knownValid: cache,
}
}
func (v *PreimageVerifier) CreateChallenge(ctx context.Context, blockHash common.Hash, oracle VerifierPreimageOracle, preimage keccakTypes.LargePreimageMetaData) (keccakTypes.Challenge, error) {
root, err := oracle.GetProposalTreeRoot(ctx, rpcblock.ByHash(blockHash), preimage.LargePreimageIdent)
if err != nil {
return keccakTypes.Challenge{}, fmt.Errorf("failed to get proposal merkle root: %w", err)
}
if valid, ok := v.knownValid.Get(root); ok && valid {
// We've already determined that the keccak transition is valid.
// Note that the merkle tree may have been validated by a different proposal but since the tree root
// commits to all the input data and the resulting keccak state matrix, any other proposal with the same
// root must also have the same inputs and correctly applied keccak.
// It is possible that this proposal can't be squeezed because the claimed data length doesn't match the
// actual length but the contracts enforce that and it can't be challenged on that basis.
return keccakTypes.Challenge{}, matrix.ErrValid
}
inputs, err := v.fetcher.FetchInputs(ctx, blockHash, oracle, preimage.LargePreimageIdent)
if err != nil {
return keccakTypes.Challenge{}, fmt.Errorf("failed to fetch leaves: %w", err)
}
readers := make([]io.Reader, 0, len(inputs))
var commitments []common.Hash
for _, input := range inputs {
readers = append(readers, bytes.NewReader(input.Input))
commitments = append(commitments, input.Commitments...)
}
challenge, err := matrix.Challenge(io.MultiReader(readers...), commitments)
if errors.Is(err, matrix.ErrValid) {
v.knownValid.Add(root, true)
return keccakTypes.Challenge{}, err
} else if err != nil {
return keccakTypes.Challenge{}, fmt.Errorf("failed to create challenge: %w", err)
}
return challenge, nil
}