117 lines
2.9 KiB
Go
117 lines
2.9 KiB
Go
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// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package encryption
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import (
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"crypto/rand"
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"encoding/binary"
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"fmt"
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"hash"
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)
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const KeyLength = 32
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type Key []byte
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type Encryption interface {
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Encrypt(data []byte, key Key) ([]byte, error)
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Decrypt(data []byte, key Key) ([]byte, error)
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}
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type encryption struct {
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padding int
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initCtr uint32
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hashFunc func() hash.Hash
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}
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func New(padding int, initCtr uint32, hashFunc func() hash.Hash) *encryption {
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return &encryption{
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padding: padding,
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initCtr: initCtr,
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hashFunc: hashFunc,
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}
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}
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func (e *encryption) Encrypt(data []byte, key Key) ([]byte, error) {
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length := len(data)
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isFixedPadding := e.padding > 0
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if isFixedPadding && length > e.padding {
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return nil, fmt.Errorf("Data length longer than padding, data length %v padding %v", length, e.padding)
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}
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paddedData := data
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if isFixedPadding && length < e.padding {
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paddedData = make([]byte, e.padding)
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copy(paddedData[:length], data)
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rand.Read(paddedData[length:])
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}
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return e.transform(paddedData, key), nil
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}
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func (e *encryption) Decrypt(data []byte, key Key) ([]byte, error) {
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length := len(data)
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if e.padding > 0 && length != e.padding {
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return nil, fmt.Errorf("Data length different than padding, data length %v padding %v", length, e.padding)
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}
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return e.transform(data, key), nil
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}
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func (e *encryption) transform(data []byte, key Key) []byte {
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dataLength := len(data)
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transformedData := make([]byte, dataLength)
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hasher := e.hashFunc()
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ctr := e.initCtr
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hashSize := hasher.Size()
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for i := 0; i < dataLength; i += hashSize {
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hasher.Write(key)
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ctrBytes := make([]byte, 4)
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binary.LittleEndian.PutUint32(ctrBytes, ctr)
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hasher.Write(ctrBytes)
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ctrHash := hasher.Sum(nil)
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hasher.Reset()
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hasher.Write(ctrHash)
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segmentKey := hasher.Sum(nil)
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hasher.Reset()
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segmentSize := min(hashSize, dataLength-i)
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for j := 0; j < segmentSize; j++ {
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transformedData[i+j] = data[i+j] ^ segmentKey[j]
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}
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ctr++
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}
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return transformedData
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}
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func GenerateRandomKey() (Key, error) {
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key := make([]byte, KeyLength)
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_, err := rand.Read(key)
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return key, err
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}
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func min(x, y int) int {
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if x < y {
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return x
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}
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return y
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}
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