swarm/storage: Add multihash support when datalength header = 0

swarm/storage/resource.go

@@ -532,7 +532,16 @@ func (self *ResourceHandler) parseUpdate(chunkdata []byte) (*Signature, uint32,
 	namelength := int(headerlength) - cursor + 4
 	name = string(chunkdata[cursor : cursor+namelength])
 	cursor += namelength
-	intdatalength := int(datalength)
+	var intdatalength int
+	if datalength == 0 {
+		intdatalength = isMultihash(chunkdata[cursor:])
+		multihashboundary := cursor + intdatalength
+		if len(chunkdata) != multihashboundary && len(chunkdata) < multihashboundary+signatureLength {
+			return nil, 0, 0, "", nil, errors.New("Corrupt multihash data")
+		}
+	} else {
+		intdatalength = int(datalength)
+	}
 	data = make([]byte, intdatalength)
 	copy(data, chunkdata[cursor:cursor+intdatalength])
 
@@ -553,7 +562,19 @@ func (self *ResourceHandler) parseUpdate(chunkdata []byte) (*Signature, uint32,
 // It is the caller's responsibility to make sure that this data is not stale.
 //
 // A resource update cannot span chunks, and thus has max length 4096
+
+func (self *ResourceHandler) UpdateMultihash(ctx context.Context, name string, data []byte) (Key, error) {
+	if isMultihash(data) == 0 {
+		return nil, errors.New("Invalid multihash")
+	}
+	return self.update(ctx, name, data, true)
+}
+
 func (self *ResourceHandler) Update(ctx context.Context, name string, data []byte) (Key, error) {
+	return self.update(ctx, name, data, false)
+}
+
+func (self *ResourceHandler) update(ctx context.Context, name string, data []byte, multihash bool) (Key, error) {
 
 	var signaturelength int
 	if self.validator != nil {
@@ -618,7 +639,11 @@ func (self *ResourceHandler) Update(ctx context.Context, name string, data []byt
 		}
 	}
 
-	chunk := newUpdateChunk(key, signature, nextperiod, version, name, data)
+	var datalength int
+	if !multihash {
+		datalength = len(data)
+	}
+	chunk := newUpdateChunk(key, signature, nextperiod, version, name, data, datalength)
 
 	// send the chunk
 	self.Put(chunk)
@@ -703,7 +728,7 @@ func getAddressFromDataSig(datahash common.Hash, signature Signature) (common.Ad
 }
 
 // create an update chunk
-func newUpdateChunk(key Key, signature *Signature, period uint32, version uint32, name string, data []byte) *Chunk {
+func newUpdateChunk(key Key, signature *Signature, period uint32, version uint32, name string, data []byte, datalength int) *Chunk {
 
 	// no signatures if no validator
 	var signaturelength int
@@ -714,11 +739,9 @@ func newUpdateChunk(key Key, signature *Signature, period uint32, version uint32
 	// prepend version and period to allow reverse lookups
 	headerlength := len(name) + 4 + 4
 
-	// also prepend datalength
-	datalength := len(data)
-
+	actualdatalength := len(data)
 	chunk := NewChunk(key, nil)
-	chunk.SData = make([]byte, 4+signaturelength+headerlength+datalength) // initial 4 are uint16 length descriptors for headerlength and datalength
+	chunk.SData = make([]byte, 4+signaturelength+headerlength+actualdatalength) // initial 4 are uint16 length descriptors for headerlength and datalength
 
 	// data header length does NOT include the header length prefix bytes themselves
 	cursor := 0
@@ -830,3 +853,31 @@ func (self *ResourceHandler) keyDataHash(key Key, data []byte) common.Hash {
 	hasher.Write(data)
 	return common.BytesToHash(hasher.Sum(nil))
 }
+
+// if first byte is the start of a multihash this function will try to parse it
+// if successful it returns the length of multihash data, 0 otherwise
+func isMultihash(data []byte) int {
+	cursor := 0
+	hashtype, c := binary.Uvarint(data)
+	log.Trace("ismultihash", "hashtype", hashtype, "c", c)
+	if c == 0 {
+		log.Debug("Corrupt multihash data, hashtype is unreadable")
+		return 0
+	}
+	cursor += c
+	hashlength, c := binary.Uvarint(data[cursor:])
+	log.Trace("ismultihash", "hashlength", hashlength, "c", c)
+	if c == 0 {
+		log.Debug("Corrupt multihash data, hashlength is unreadable")
+		return 0
+	}
+	cursor += c
+	// we cheekily assume hashlength < maxint
+	inthashlength := int(hashlength)
+	log.Trace("ismultihash", "datalen", len(data), "hashlength", inthashlength, "cursor", c)
+	if len(data[cursor:]) < inthashlength {
+		log.Debug("Corrupt multihash data, hash does not align with data boundary")
+		return 0
+	}
+	return cursor + inthashlength
+}

swarm/storage/resource_test.go

@@ -15,6 +15,8 @@ import (
 	"testing"
 	"time"
 
+	"github.com/multiformats/go-multihash"
+
 	"github.com/ethereum/go-ethereum/accounts/abi/bind"
 	"github.com/ethereum/go-ethereum/accounts/abi/bind/backends"
 	"github.com/ethereum/go-ethereum/common"
@@ -107,7 +109,7 @@ func TestResourceReverse(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	chunk := newUpdateChunk(key, &sig, period, version, safeName, data)
+	chunk := newUpdateChunk(key, &sig, period, version, safeName, data, len(data))
 
 	// check that we can recover the owner account from the update chunk's signature
 	checksig, checkperiod, checkversion, checkname, checkdata, err := rh.parseUpdate(chunk.SData)
@@ -456,3 +458,99 @@ func (self *testValidator) checkAccess(name string, address common.Address) (boo
 func (self *testValidator) nameHash(name string) common.Hash {
 	return self.hashFunc(name)
 }
+
+func TestResourceMultihash(t *testing.T) {
+
+	// signer containing private key
+	//	signer, err := newTestSigner()
+	//	if err != nil {
+	//		t.Fatal(err)
+	//	}
+
+	// make fake backend, set up rpc and create resourcehandler
+	backend := &fakeBackend{
+		blocknumber: int64(startBlock),
+	}
+
+	// set up rpc and create resourcehandler
+	rh, _, _, teardownTest, err := setupTest(backend, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer teardownTest()
+
+	// create a new resource
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	_, err = rh.NewResource(ctx, safeName, resourceFrequency)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// we're naïvely assuming keccak256 for swarm hashes
+	// if it ever changes this test should also change
+	swarmhashbytes := rh.nameHash("foo")
+	swarmhashmulti, err := multihash.Encode(swarmhashbytes.Bytes(), multihash.KECCAK_256)
+	if err != nil {
+		t.Fatal(err)
+	}
+	swarmhashkey, err := rh.UpdateMultihash(ctx, safeName, swarmhashmulti)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	sha1bytes := make([]byte, multihash.DefaultLengths[multihash.SHA1])
+	sha1multi, err := multihash.Encode(sha1bytes, multihash.SHA1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sha1key, err := rh.UpdateMultihash(ctx, safeName, sha1multi)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// invalid multihashes
+	_, err = rh.UpdateMultihash(ctx, safeName, swarmhashmulti[1:])
+	if err == nil {
+		t.Fatalf("Expected update to fail with first byte skipped")
+	}
+	_, err = rh.UpdateMultihash(ctx, safeName, swarmhashmulti[:len(swarmhashmulti)-2])
+	if err == nil {
+		t.Fatalf("Expected update to fail with last byte skipped")
+	}
+
+	swarmhashchunk, err := rh.ChunkStore.(*resourceChunkStore).localStore.(*LocalStore).memStore.Get(swarmhashkey)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, _, _, _, data, err := rh.parseUpdate(swarmhashchunk.SData)
+	if err != nil {
+		t.Fatal(err)
+	}
+	swarmhashdecode, err := multihash.Decode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(swarmhashdecode.Digest, swarmhashbytes.Bytes()) {
+		t.Fatalf("Decoded SHA1 hash '%x' does not match original hash '%x'", swarmhashdecode.Digest, swarmhashbytes.Bytes())
+	}
+	sha1chunk, err := rh.ChunkStore.(*resourceChunkStore).localStore.(*LocalStore).memStore.Get(sha1key)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, _, _, _, data, err = rh.parseUpdate(sha1chunk.SData)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sha1decode, err := multihash.Decode(data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !bytes.Equal(sha1decode.Digest, sha1bytes) {
+		t.Fatalf("Decoded SHA1 hash '%x' does not match original hash '%x'", sha1decode.Digest, sha1bytes)
+	}
+
+	// test with signed data
+	//	rh2, err := NewResourceHandler(datadir, &testCloudStore{}, rh.ethClient, Signer)
+	//	swarmhashsignedkey, err := rh2.UpdateMultihash(ctx, safeName, swarmhashmulti)
+}