Merge pull request #364 from ncdc/resumable-digest-optional

Use a build flag to disable resumable digests

digest/digester.go

@@ -2,12 +2,7 @@ package digest
 
 import (
 	"crypto/sha256"
-	"fmt"
 	"hash"
-
-	"github.com/jlhawn/go-crypto"          // For ResumableHash
-	_ "github.com/jlhawn/go-crypto/sha256" // For Resumable SHA256
-	_ "github.com/jlhawn/go-crypto/sha512" // For Resumable SHA384, SHA512
 )
 
 // Digester calculates the digest of written data. It is functionally
@@ -38,43 +33,22 @@ func (d *Digester) Digest() Digest {
 	return NewDigest(d.alg, d.Hash)
 }
 
+// ResumableHash is the common interface implemented by all resumable hash
+// functions.
+type ResumableHash interface {
+	// ResumableHash is a superset of hash.Hash
+	hash.Hash
+	// Len returns the number of bytes written to the Hash so far.
+	Len() uint64
+	// State returns a snapshot of the state of the Hash.
+	State() ([]byte, error)
+	// Restore resets the Hash to the given state.
+	Restore(state []byte) error
+}
+
 // ResumableDigester is a digester that can export its internal state and be
 // restored from saved state.
-type ResumableDigester struct {
-	alg string
-	crypto.ResumableHash
-}
-
-var resumableHashAlgs = map[string]crypto.Hash{
-	"sha256": crypto.SHA256,
-	"sha384": crypto.SHA384,
-	"sha512": crypto.SHA512,
-}
-
-// NewResumableDigester creates a new ResumableDigester with the given hashing
-// algorithm.
-func NewResumableDigester(alg string) (ResumableDigester, error) {
-	hash, supported := resumableHashAlgs[alg]
-	if !supported {
-		return ResumableDigester{}, fmt.Errorf("unsupported resumable hash algorithm: %s", alg)
-	}
-
-	return ResumableDigester{
-		alg:           alg,
-		ResumableHash: hash.New(),
-	}, nil
-}
-
-// NewCanonicalResumableDigester creates a ResumableDigester using the default
-// digest algorithm.
-func NewCanonicalResumableDigester() ResumableDigester {
-	return ResumableDigester{
-		alg:           "sha256",
-		ResumableHash: crypto.SHA256.New(),
-	}
-}
-
-// Digest returns the current digest for this resumable digester.
-func (d ResumableDigester) Digest() Digest {
-	return NewDigest(d.alg, d.ResumableHash)
+type ResumableDigester interface {
+	ResumableHash
+	Digest() Digest
 }

digest/digester_resumable.go

@@ -0,0 +1,52 @@
+// +build !noresumabledigest
+
+package digest
+
+import (
+	"fmt"
+
+	"github.com/jlhawn/go-crypto"
+	// For ResumableHash
+	_ "github.com/jlhawn/go-crypto/sha256" // For Resumable SHA256
+	_ "github.com/jlhawn/go-crypto/sha512" // For Resumable SHA384, SHA512
+)
+
+// resumableDigester implements ResumableDigester.
+type resumableDigester struct {
+	alg string
+	crypto.ResumableHash
+}
+
+var resumableHashAlgs = map[string]crypto.Hash{
+	"sha256": crypto.SHA256,
+	"sha384": crypto.SHA384,
+	"sha512": crypto.SHA512,
+}
+
+// NewResumableDigester creates a new ResumableDigester with the given hashing
+// algorithm.
+func NewResumableDigester(alg string) (ResumableDigester, error) {
+	hash, supported := resumableHashAlgs[alg]
+	if !supported {
+		return resumableDigester{}, fmt.Errorf("unsupported resumable hash algorithm: %s", alg)
+	}
+
+	return resumableDigester{
+		alg:           alg,
+		ResumableHash: hash.New(),
+	}, nil
+}
+
+// NewCanonicalResumableDigester creates a ResumableDigester using the default
+// digest algorithm.
+func NewCanonicalResumableDigester() ResumableDigester {
+	return resumableDigester{
+		alg:           "sha256",
+		ResumableHash: crypto.SHA256.New(),
+	}
+}
+
+// Digest returns the current digest for this resumable digester.
+func (d resumableDigester) Digest() Digest {
+	return NewDigest(d.alg, d.ResumableHash)
+}

registry/storage/layerstore.go

@@ -138,13 +138,16 @@ func (ls *layerStore) newLayerUpload(uuid, path string, startedAt time.Time) (di
 		return nil, err
 	}
 
-	return &layerWriter{
+	lw := &layerWriter{
 		layerStore:         ls,
 		uuid:               uuid,
 		startedAt:          startedAt,
-		resumableDigester:  digest.NewCanonicalResumableDigester(),
 		bufferedFileWriter: *fw,
-	}, nil
+	}
+
+	lw.setupResumableDigester()
+
+	return lw, nil
 }
 
 func (ls *layerStore) path(dgst digest.Digest) (string, error) {

registry/storage/layerwriter.go

@@ -87,6 +87,10 @@ func (lw *layerWriter) Cancel() error {
 }
 
 func (lw *layerWriter) Write(p []byte) (int, error) {
+	if lw.resumableDigester == nil {
+		return lw.bufferedFileWriter.Write(p)
+	}
+
 	// Ensure that the current write offset matches how many bytes have been
 	// written to the digester. If not, we need to update the digest state to
 	// match the current write position.
@@ -98,6 +102,10 @@ func (lw *layerWriter) Write(p []byte) (int, error) {
 }
 
 func (lw *layerWriter) ReadFrom(r io.Reader) (n int64, err error) {
+	if lw.resumableDigester == nil {
+		return lw.bufferedFileWriter.ReadFrom(r)
+	}
+
 	// Ensure that the current write offset matches how many bytes have been
 	// written to the digester. If not, we need to update the digest state to
 	// match the current write position.
@@ -113,8 +121,10 @@ func (lw *layerWriter) Close() error {
 		return lw.err
 	}
 
-	if err := lw.storeHashState(); err != nil {
-		return err
+	if lw.resumableDigester != nil {
+		if err := lw.storeHashState(); err != nil {
+			return err
+		}
 	}
 
 	return lw.bufferedFileWriter.Close()
@@ -261,22 +271,37 @@ func (lw *layerWriter) storeHashState() error {
 // validateLayer checks the layer data against the digest, returning an error
 // if it does not match. The canonical digest is returned.
 func (lw *layerWriter) validateLayer(dgst digest.Digest) (digest.Digest, error) {
-	// Restore the hasher state to the end of the upload.
-	if err := lw.resumeHashAt(lw.size); err != nil {
-		return "", err
+	var (
+		verified, fullHash bool
+		canonical          digest.Digest
+	)
+
+	if lw.resumableDigester != nil {
+		// Restore the hasher state to the end of the upload.
+		if err := lw.resumeHashAt(lw.size); err != nil {
+			return "", err
+		}
+
+		canonical = lw.resumableDigester.Digest()
+
+		if canonical.Algorithm() == dgst.Algorithm() {
+			// Common case: client and server prefer the same canonical digest
+			// algorithm - currently SHA256.
+			verified = dgst == canonical
+		} else {
+			// The client wants to use a different digest algorithm. They'll just
+			// have to be patient and wait for us to download and re-hash the
+			// uploaded content using that digest algorithm.
+			fullHash = true
+		}
+	} else {
+		// Not using resumable digests, so we need to hash the entire layer.
+		fullHash = true
 	}
 
-	var verified bool
-	canonical := lw.resumableDigester.Digest()
+	if fullHash {
+		digester := digest.NewCanonicalDigester()
 
-	if canonical.Algorithm() == dgst.Algorithm() {
-		// Common case: client and server prefer the same canonical digest
-		// algorithm - currently SHA256.
-		verified = dgst == canonical
-	} else {
-		// The client wants to use a different digest algorithm. They'll just
-		// have to be patient and wait for us to download and re-hash the
-		// uploaded content using that digest algorithm.
 		digestVerifier, err := digest.NewDigestVerifier(dgst)
 		if err != nil {
 			return "", err
@@ -288,10 +313,13 @@ func (lw *layerWriter) validateLayer(dgst digest.Digest) (digest.Digest, error)
 			return "", err
 		}
 
-		if _, err = io.Copy(digestVerifier, fr); err != nil {
+		tr := io.TeeReader(fr, digester)
+
+		if _, err = io.Copy(digestVerifier, tr); err != nil {
 			return "", err
 		}
 
+		canonical = digester.Digest()
 		verified = digestVerifier.Verified()
 	}
 

registry/storage/layerwriter_nonresumable.go

@@ -0,0 +1,6 @@
+// +build noresumabledigest
+
+package storage
+
+func (lw *layerWriter) setupResumableDigester() {
+}

registry/storage/layerwriter_resumable.go

@@ -0,0 +1,9 @@
+// +build !noresumabledigest
+
+package storage
+
+import "github.com/docker/distribution/digest"
+
+func (lw *layerWriter) setupResumableDigester() {
+	lw.resumableDigester = digest.NewCanonicalResumableDigester()
+}