path: root/swarm/storage/hasherstore.go

// Copyright 2018 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 storage

import (
    "context"
    "fmt"
    "sync"

    "github.com/ethereum/go-ethereum/crypto/sha3"
    "github.com/ethereum/go-ethereum/swarm/storage/encryption"
)

type chunkEncryption struct {
    spanEncryption encryption.Encryption
    dataEncryption encryption.Encryption
}

type hasherStore struct {
    store           ChunkStore
    hashFunc        SwarmHasher
    chunkEncryption *chunkEncryption
    hashSize        int   // content hash size
    refSize         int64 // reference size (content hash + possibly encryption key)
    wg              *sync.WaitGroup
    closed          chan struct{}
}

func newChunkEncryption(chunkSize, refSize int64) *chunkEncryption {
    return &chunkEncryption{
        spanEncryption: encryption.New(0, uint32(chunkSize/refSize), sha3.NewKeccak256),
        dataEncryption: encryption.New(int(chunkSize), 0, sha3.NewKeccak256),
    }
}

// NewHasherStore creates a hasherStore object, which implements Putter and Getter interfaces.
// With the HasherStore you can put and get chunk data (which is just []byte) into a ChunkStore
// and the hasherStore will take core of encryption/decryption of data if necessary
func NewHasherStore(chunkStore ChunkStore, hashFunc SwarmHasher, toEncrypt bool) *hasherStore {
    var chunkEncryption *chunkEncryption

    hashSize := hashFunc().Size()
    refSize := int64(hashSize)
    if toEncrypt {
        refSize += encryption.KeyLength
        chunkEncryption = newChunkEncryption(DefaultChunkSize, refSize)
    }

    return &hasherStore{
        store:           chunkStore,
        hashFunc:        hashFunc,
        chunkEncryption: chunkEncryption,
        hashSize:        hashSize,
        refSize:         refSize,
        wg:              &sync.WaitGroup{},
        closed:          make(chan struct{}),
    }
}

// Put stores the chunkData into the ChunkStore of the hasherStore and returns the reference.
// If hasherStore has a chunkEncryption object, the data will be encrypted.
// Asynchronous function, the data will not necessarily be stored when it returns.
func (h *hasherStore) Put(ctx context.Context, chunkData ChunkData) (Reference, error) {
    c := chunkData
    size := chunkData.Size()
    var encryptionKey encryption.Key
    if h.chunkEncryption != nil {
        var err error
        c, encryptionKey, err = h.encryptChunkData(chunkData)
        if err != nil {
            return nil, err
        }
    }
    chunk := h.createChunk(c, size)

    h.storeChunk(ctx, chunk)

    return Reference(append(chunk.Addr, encryptionKey...)), nil
}

// Get returns data of the chunk with the given reference (retrieved from the ChunkStore of hasherStore).
// If the data is encrypted and the reference contains an encryption key, it will be decrypted before
// return.
func (h *hasherStore) Get(ctx context.Context, ref Reference) (ChunkData, error) {
    key, encryptionKey, err := parseReference(ref, h.hashSize)
    if err != nil {
        return nil, err
    }
    toDecrypt := (encryptionKey != nil)

    chunk, err := h.store.Get(ctx, key)
    if err != nil {
        return nil, err
    }

    chunkData := chunk.SData
    if toDecrypt {
        var err error
        chunkData, err = h.decryptChunkData(chunkData, encryptionKey)
        if err != nil {
            return nil, err
        }
    }
    return chunkData, nil
}

// Close indicates that no more chunks will be put with the hasherStore, so the Wait
// function can return when all the previously put chunks has been stored.
func (h *hasherStore) Close() {
    close(h.closed)
}

// Wait returns when
//    1) the Close() function has been called and
//    2) all the chunks which has been Put has been stored
func (h *hasherStore) Wait(ctx context.Context) error {
    <-h.closed
    h.wg.Wait()
    return nil
}

func (h *hasherStore) createHash(chunkData ChunkData) Address {
    hasher := h.hashFunc()
    hasher.ResetWithLength(chunkData[:8]) // 8 bytes of length
    hasher.Write(chunkData[8:])           // minus 8 []byte length
    return hasher.Sum(nil)
}

func (h *hasherStore) createChunk(chunkData ChunkData, chunkSize int64) *Chunk {
    hash := h.createHash(chunkData)
    chunk := NewChunk(hash, nil)
    chunk.SData = chunkData
    chunk.Size = chunkSize

    return chunk
}

func (h *hasherStore) encryptChunkData(chunkData ChunkData) (ChunkData, encryption.Key, error) {
    if len(chunkData) < 8 {
        return nil, nil, fmt.Errorf("Invalid ChunkData, min length 8 got %v", len(chunkData))
    }

    encryptionKey, err := encryption.GenerateRandomKey()
    if err != nil {
        return nil, nil, err
    }

    encryptedSpan, err := h.chunkEncryption.spanEncryption.Encrypt(chunkData[:8], encryptionKey)
    if err != nil {
        return nil, nil, err
    }
    encryptedData, err := h.chunkEncryption.dataEncryption.Encrypt(chunkData[8:], encryptionKey)
    if err != nil {
        return nil, nil, err
    }
    c := make(ChunkData, len(encryptedSpan)+len(encryptedData))
    copy(c[:8], encryptedSpan)
    copy(c[8:], encryptedData)
    return c, encryptionKey, nil
}

func (h *hasherStore) decryptChunkData(chunkData ChunkData, encryptionKey encryption.Key) (ChunkData, error) {
    if len(chunkData) < 8 {
        return nil, fmt.Errorf("Invalid ChunkData, min length 8 got %v", len(chunkData))
    }

    decryptedSpan, err := h.chunkEncryption.spanEncryption.Decrypt(chunkData[:8], encryptionKey)
    if err != nil {
        return nil, err
    }

    decryptedData, err := h.chunkEncryption.dataEncryption.Decrypt(chunkData[8:], encryptionKey)
    if err != nil {
        return nil, err
    }

    // removing extra bytes which were just added for padding
    length := ChunkData(decryptedSpan).Size()
    for length > DefaultChunkSize {
        length = length + (DefaultChunkSize - 1)
        length = length / DefaultChunkSize
        length *= h.refSize
    }

    c := make(ChunkData, length+8)
    copy(c[:8], decryptedSpan)
    copy(c[8:], decryptedData[:length])

    return c[:length+8], nil
}

func (h *hasherStore) RefSize() int64 {
    return h.refSize
}

func (h *hasherStore) storeChunk(ctx context.Context, chunk *Chunk) {
    h.wg.Add(1)
    go func() {
        <-chunk.dbStoredC
        h.wg.Done()
    }()
    h.store.Put(ctx, chunk)
}

func parseReference(ref Reference, hashSize int) (Address, encryption.Key, error) {
    encryptedKeyLength := hashSize + encryption.KeyLength
    switch len(ref) {
    case KeyLength:
        return Address(ref), nil, nil
    case encryptedKeyLength:
        encKeyIdx := len(ref) - encryption.KeyLength
        return Address(ref[:encKeyIdx]), encryption.Key(ref[encKeyIdx:]), nil
    default:
        return nil, nil, fmt.Errorf("Invalid reference length, expected %v or %v got %v", hashSize, encryptedKeyLength, len(ref))
    }

}