key.go

package merkletree

import (
	"math"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	poseidon "github.com/iden3/go-iden3-crypto/goldenposeidon"
)

// Key stores key of the leaf
type Key [32]byte

const (
	HashPoseidonAllZeroes = "0xc71603f33a1144ca7953db0ab48808f4c4055e3364a246c33c18a9786cb0b359"
)

// keyEthAddr is the common code for all the keys related to ethereum addresses.
func keyEthAddr(ethAddr common.Address, leafType leafType, key1Capacity [4]uint64) ([]byte, error) {
	ethAddrBI := new(big.Int).SetBytes(ethAddr.Bytes())
	ethAddrArr := scalar2fea(ethAddrBI)

	key1 := [8]uint64{
		ethAddrArr[0],
		ethAddrArr[1],
		ethAddrArr[2],
		ethAddrArr[3],
		ethAddrArr[4],
		0,
		uint64(leafType),
		0,
	}

	result, err := poseidon.Hash(key1, key1Capacity)
	if err != nil {
		return nil, err
	}

	return h4ToFilledByteSlice(result[:]), nil
}

func defaultCapIn() ([4]uint64, error) {
	capIn, err := stringToh4(HashPoseidonAllZeroes)
	if err != nil {
		return [4]uint64{}, err
	}

	return [4]uint64{capIn[0], capIn[1], capIn[2], capIn[3]}, nil
}

// KeyEthAddrBalance returns the key of balance leaf:
// hk0: H([0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0])
// key: H([ethAddr[0:4], ethAddr[4:8], ethAddr[8:12], ethAddr[12:16], ethAddr[16:20], 0, 0, 0], [hk0[0], hk0[1], hk0[2], hk0[3]])
func KeyEthAddrBalance(ethAddr common.Address) ([]byte, error) {
	capIn, err := defaultCapIn()
	if err != nil {
		return nil, err
	}

	return keyEthAddr(ethAddr, leafTypeBalance, capIn)
}

// KeyEthAddrNonce returns the key of nonce leaf:
// hk0: H([0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0])
// key: H([ethAddr[0:4], ethAddr[4:8], ethAddr[8:12], ethAddr[12:16], ethAddr[16:20], 0, 1, 0], [hk0[0], hk0[1], hk0[2], hk0[3]]
func KeyEthAddrNonce(ethAddr common.Address) ([]byte, error) {
	capIn, err := defaultCapIn()
	if err != nil {
		return nil, err
	}

	return keyEthAddr(ethAddr, leafTypeNonce, capIn)
}

// KeyContractCode returns the key of contract code leaf:
// hk0: H([0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, 0])
// key: H([ethAddr[0:4], ethAddr[4:8], ethAddr[8:12], ethAddr[12:16], ethAddr[16:20], 0, 2, 0], [hk0[0], hk0[1], hk0[2], hk0[3]]
func KeyContractCode(ethAddr common.Address) ([]byte, error) {
	capIn, err := defaultCapIn()
	if err != nil {
		return nil, err
	}

	return keyEthAddr(ethAddr, leafTypeCode, capIn)
}

// KeyContractStorage returns the key of contract storage position leaf:
// hk0: H([stoPos[0:4], stoPos[4:8], stoPos[8:12], stoPos[12:16], stoPos[16:20], stoPos[20:24], stoPos[24:28], stoPos[28:32], [0, 0, 0, 0])
// key: H([ethAddr[0:4], ethAddr[4:8], ethAddr[8:12], ethAddr[12:16], ethAddr[16:20], 0, 3, 0], [hk0[0], hk0[1], hk0[2], hk0[3])
func KeyContractStorage(ethAddr common.Address, storagePos []byte) ([]byte, error) {
	storageBI := new(big.Int).SetBytes(storagePos)

	storageArr := scalar2fea(storageBI)

	hk0, err := poseidon.Hash([8]uint64{
		storageArr[0],
		storageArr[1],
		storageArr[2],
		storageArr[3],
		storageArr[4],
		storageArr[5],
		storageArr[6],
		storageArr[7],
	}, [4]uint64{})
	if err != nil {
		return nil, err
	}

	return keyEthAddr(ethAddr, leafTypeStorage, hk0)
}

// hashContractBytecode computes the bytecode hash in order to add it to the
// state-tree.
func hashContractBytecode(code []byte) ([]uint64, error) {
	const (
		bytecodeElementsHash = 8
		bytecodeBytesElement = 7

		maxBytesToAdd = bytecodeElementsHash * bytecodeBytesElement
	)

	numHashes := int(math.Ceil(float64(len(code)) / float64(maxBytesToAdd)))

	tmpHash := [4]uint64{}
	var err error

	bytesPointer := 0
	for i := 0; i < numHashes; i++ {
		elementsToHash := [12]uint64{}

		if i != 0 {
			for j := 0; j < 4; j++ {
				elementsToHash[j] = tmpHash[j]
			}
		} else {
			for j := 0; j < 4; j++ {
				elementsToHash[j] = 0
			}
		}
		subsetBytecode := code[bytesPointer : int(math.Min(float64(len(code)-1), float64(bytesPointer+maxBytesToAdd)))+1]
		bytesPointer += maxBytesToAdd
		tmpElem := [7]byte{}
		counter := 0
		index := 4
		for j := 0; j < maxBytesToAdd; j++ {
			byteToAdd := []byte{0}

			if j < len(subsetBytecode) {
				byteToAdd = subsetBytecode[j : j+1]
			}
			tmpElem[counter] = byteToAdd[0]
			counter++

			if counter == bytecodeBytesElement {
				elementsToHash[index] = new(big.Int).SetBytes(tmpElem[:]).Uint64()
				index++
				tmpElem = [7]byte{}
				counter = 0
			}
		}
		tmpHash, err = poseidon.Hash([8]uint64{
			elementsToHash[4],
			elementsToHash[5],
			elementsToHash[6],
			elementsToHash[7],
			elementsToHash[8],
			elementsToHash[9],
			elementsToHash[10],
			elementsToHash[11],
		}, [4]uint64{
			elementsToHash[0],
			elementsToHash[1],
			elementsToHash[2],
			elementsToHash[3],
		})
		if err != nil {
			return nil, err
		}
	}
	return tmpHash[:], nil
}