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/atomic"

    ch "github.com/dexon-foundation/dexon/swarm/chunk"
    "github.com/dexon-foundation/dexon/swarm/storage/encryption"
    "golang.org/x/crypto/sha3"
)

type hasherStore struct {
    store     ChunkStore
    toEncrypt bool
    hashFunc  SwarmHasher
    hashSize  int           // content hash size
    refSize   int64         // reference size (content hash + possibly encryption key)
    errC      chan error    // global error channel
    doneC     chan struct{} // closed by Close() call to indicate that count is the final number of chunks
    quitC     chan struct{} // closed to quit unterminated routines
    // nrChunks is used with atomic functions
    // it is required to be at the end of the struct to ensure 64bit alignment for arm architecture
    // see: https://golang.org/pkg/sync/atomic/#pkg-note-BUG
    nrChunks uint64 // number of chunks to store
}

// 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(store ChunkStore, hashFunc SwarmHasher, toEncrypt bool) *hasherStore {
    hashSize := hashFunc().Size()
    refSize := int64(hashSize)
    if toEncrypt {
        refSize += encryption.KeyLength
    }

    h := &hasherStore{
        store:     store,
        toEncrypt: toEncrypt,
        hashFunc:  hashFunc,
        hashSize:  hashSize,
        refSize:   refSize,
        errC:      make(chan error),
        doneC:     make(chan struct{}),
        quitC:     make(chan struct{}),
    }

    return h
}

// 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
    var encryptionKey encryption.Key
    if h.toEncrypt {
        var err error
        c, encryptionKey, err = h.encryptChunkData(chunkData)
        if err != nil {
            return nil, err
        }
    }
    chunk := h.createChunk(c)
    h.storeChunk(ctx, chunk)

    return Reference(append(chunk.Address(), 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) {
    addr, encryptionKey, err := parseReference(ref, h.hashSize)
    if err != nil {
        return nil, err
    }

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

    chunkData := ChunkData(chunk.Data())
    toDecrypt := (encryptionKey != nil)
    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.doneC)
}

// 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 {
    defer close(h.quitC)
    var nrStoredChunks uint64 // number of stored chunks
    var done bool
    doneC := h.doneC
    for {
        select {
        // if context is done earlier, just return with the error
        case <-ctx.Done():
            return ctx.Err()
        // doneC is closed if all chunks have been submitted, from then we just wait until all of them are also stored
        case <-doneC:
            done = true
            doneC = nil
        // a chunk has been stored, if err is nil, then successfully, so increase the stored chunk counter
        case err := <-h.errC:
            if err != nil {
                return err
            }
            nrStoredChunks++
        }
        // if all the chunks have been submitted and all of them are stored, then we can return
        if done {
            if nrStoredChunks >= atomic.LoadUint64(&h.nrChunks) {
                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) *chunk {
    hash := h.createHash(chunkData)
    chunk := NewChunk(hash, chunkData)
    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))
    }

    key, encryptedSpan, encryptedData, err := h.encrypt(chunkData)
    if err != nil {
        return nil, nil, err
    }
    c := make(ChunkData, len(encryptedSpan)+len(encryptedData))
    copy(c[:8], encryptedSpan)
    copy(c[8:], encryptedData)
    return c, key, 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, decryptedData, err := h.decrypt(chunkData, encryptionKey)
    if err != nil {
        return nil, err
    }

    // removing extra bytes which were just added for padding
    length := ChunkData(decryptedSpan).Size()
    for length > ch.DefaultSize {
        length = length + (ch.DefaultSize - 1)
        length = length / ch.DefaultSize
        length *= uint64(h.refSize)
    }

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

    return c, nil
}

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

func (h *hasherStore) encrypt(chunkData ChunkData) (encryption.Key, []byte, []byte, error) {
    key := encryption.GenerateRandomKey(encryption.KeyLength)
    encryptedSpan, err := h.newSpanEncryption(key).Encrypt(chunkData[:8])
    if err != nil {
        return nil, nil, nil, err
    }
    encryptedData, err := h.newDataEncryption(key).Encrypt(chunkData[8:])
    if err != nil {
        return nil, nil, nil, err
    }
    return key, encryptedSpan, encryptedData, nil
}

func (h *hasherStore) decrypt(chunkData ChunkData, key encryption.Key) ([]byte, []byte, error) {
    encryptedSpan, err := h.newSpanEncryption(key).Encrypt(chunkData[:8])
    if err != nil {
        return nil, nil, err
    }
    encryptedData, err := h.newDataEncryption(key).Encrypt(chunkData[8:])
    if err != nil {
        return nil, nil, err
    }
    return encryptedSpan, encryptedData, nil
}

func (h *hasherStore) newSpanEncryption(key encryption.Key) encryption.Encryption {
    return encryption.New(key, 0, uint32(ch.DefaultSize/h.refSize), sha3.NewLegacyKeccak256)
}

func (h *hasherStore) newDataEncryption(key encryption.Key) encryption.Encryption {
    return encryption.New(key, int(ch.DefaultSize), 0, sha3.NewLegacyKeccak256)
}

func (h *hasherStore) storeChunk(ctx context.Context, chunk *chunk) {
    atomic.AddUint64(&h.nrChunks, 1)
    go func() {
        select {
        case h.errC <- h.store.Put(ctx, chunk):
        case <-h.quitC:
        }
    }()
}

func parseReference(ref Reference, hashSize int) (Address, encryption.Key, error) {
    encryptedRefLength := hashSize + encryption.KeyLength
    switch len(ref) {
    case AddressLength:
        return Address(ref), nil, nil
    case encryptedRefLength:
        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, encryptedRefLength, len(ref))
    }
}