Official Go implementation of the Ethereum protocol
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go-ethereum/beacon/merkle/merkle.go

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// Copyright 2022 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
// Package merkle implements proof verifications in binary merkle trees.
package merkle
import (
"crypto/sha256"
"errors"
"reflect"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/common/hexutil"
)
// Value represents either a 32 byte leaf value or hash node in a binary merkle tree/partial proof.
type Value [32]byte
// Values represent a series of merkle tree leaves/nodes.
type Values []Value
var valueT = reflect.TypeOf(Value{})
// UnmarshalJSON parses a merkle value in hex syntax.
func (m *Value) UnmarshalJSON(input []byte) error {
return hexutil.UnmarshalFixedJSON(valueT, input, m[:])
}
// VerifyProof verifies a Merkle proof branch for a single value in a
// binary Merkle tree (index is a generalized tree index).
func VerifyProof(root common.Hash, index uint64, branch Values, value Value) error {
hasher := sha256.New()
for _, sibling := range branch {
hasher.Reset()
if index&1 == 0 {
hasher.Write(value[:])
hasher.Write(sibling[:])
} else {
hasher.Write(sibling[:])
hasher.Write(value[:])
}
hasher.Sum(value[:0])
if index >>= 1; index == 0 {
return errors.New("branch has extra items")
}
}
if index != 1 {
return errors.New("branch is missing items")
}
if common.Hash(value) != root {
return errors.New("root mismatch")
}
return nil
}