Adds support for content redirects for layer downloads

Includes a delegate implementation which redirects to the URL generated
by the storagedriver, and a cloudfront implementation.
Satisfies proposal #49

configuration/configuration.go

@@ -35,6 +35,9 @@ type Configuration struct {
 
 		// Secret specifies the secret key which HMAC tokens are created with.
 		Secret string `yaml:"secret"`
+
+		// LayerHandler specifies a middleware for serving image layers.
+		LayerHandler LayerHandler `yaml:"layerhandler"`
 	} `yaml:"http"`
 }
 
@@ -240,6 +243,58 @@ type NewRelicReporting struct {
 	Name string `yaml:"name"`
 }
 
+// LayerHandler defines the configuration for middleware layer serving
+type LayerHandler map[string]Parameters
+
+// Type returns the layerhandler type
+func (layerHandler LayerHandler) Type() string {
+	// Return only key in this map
+	for k := range layerHandler {
+		return k
+	}
+	return ""
+}
+
+// Parameters returns the Parameters map for a LayerHandler configuration
+func (layerHandler LayerHandler) Parameters() Parameters {
+	return layerHandler[layerHandler.Type()]
+}
+
+// UnmarshalYAML implements the yaml.Unmarshaler interface
+// Unmarshals a single item map into a Storage or a string into a Storage type with no parameters
+func (layerHandler *LayerHandler) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var storageMap map[string]Parameters
+	err := unmarshal(&storageMap)
+	if err == nil {
+		if len(storageMap) > 1 {
+			types := make([]string, 0, len(storageMap))
+			for k := range storageMap {
+				types = append(types, k)
+			}
+			return fmt.Errorf("Must provide exactly one layerhandler type. Provided: %v", types)
+		}
+		*layerHandler = storageMap
+		return nil
+	}
+
+	var storageType string
+	err = unmarshal(&storageType)
+	if err == nil {
+		*layerHandler = LayerHandler{storageType: Parameters{}}
+		return nil
+	}
+
+	return err
+}
+
+// MarshalYAML implements the yaml.Marshaler interface
+func (layerHandler LayerHandler) MarshalYAML() (interface{}, error) {
+	if layerHandler.Parameters() == nil {
+		return layerHandler.Type(), nil
+	}
+	return map[string]Parameters(layerHandler), nil
+}
+
 // Parse parses an input configuration yaml document into a Configuration struct
 // This should generally be capable of handling old configuration format versions
 //

registry/app.go

@@ -31,6 +31,8 @@ type App struct {
 
 	tokenProvider tokenProvider
 
+	layerHandler storage.LayerHandler
+
 	accessController auth.AccessController
 }
 
@@ -76,6 +78,16 @@ func NewApp(configuration configuration.Configuration) *App {
 		app.accessController = accessController
 	}
 
+	layerHandlerType := configuration.HTTP.LayerHandler.Type()
+
+	if layerHandlerType != "" {
+		lh, err := storage.GetLayerHandler(layerHandlerType, configuration.HTTP.LayerHandler.Parameters(), driver)
+		if err != nil {
+			panic(fmt.Sprintf("unable to configure layer handler (%s): %v", layerHandlerType, err))
+		}
+		app.layerHandler = lh
+	}
+
 	return app
 }
 

registry/layer.go

@@ -58,5 +58,11 @@ func (lh *layerHandler) GetLayer(w http.ResponseWriter, r *http.Request) {
 	}
 	defer layer.Close()
 
+	handler, err := lh.layerHandler.Resolve(layer)
+	if handler != nil {
+		handler.ServeHTTP(w, r)
+		return
+	}
+
 	http.ServeContent(w, r, layer.Digest().String(), layer.CreatedAt(), layer)
 }

storage/cloudfrontlayerhandler.go

@@ -0,0 +1,106 @@
+package storage
+
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"time"
+
+	"github.com/crowdmob/goamz/cloudfront"
+	"github.com/docker/distribution/storagedriver"
+)
+
+// cloudFrontLayerHandler provides an simple implementation of layerHandler that
+// constructs temporary signed CloudFront URLs from the storagedriver layer URL,
+// then issues HTTP Temporary Redirects to this CloudFront content URL.
+type cloudFrontLayerHandler struct {
+	cloudfront           *cloudfront.CloudFront
+	delegateLayerHandler *delegateLayerHandler
+}
+
+var _ LayerHandler = &cloudFrontLayerHandler{}
+
+// newCloudFrontLayerHandler constructs and returns a new CloudFront
+// LayerHandler implementation.
+// Required options: baseurl, privatekey, keypairid
+func newCloudFrontLayerHandler(storageDriver storagedriver.StorageDriver, options map[string]interface{}) (LayerHandler, error) {
+	base, ok := options["baseurl"]
+	if !ok {
+		return nil, fmt.Errorf("No baseurl provided")
+	}
+	baseURL, ok := base.(string)
+	if !ok {
+		return nil, fmt.Errorf("baseurl must be a string")
+	}
+	pk, ok := options["privatekey"]
+	if !ok {
+		return nil, fmt.Errorf("No privatekey provided")
+	}
+	pkPath, ok := pk.(string)
+	if !ok {
+		return nil, fmt.Errorf("privatekey must be a string")
+	}
+	kpid, ok := options["keypairid"]
+	if !ok {
+		return nil, fmt.Errorf("No keypairid provided")
+	}
+	keypairID, ok := kpid.(string)
+	if !ok {
+		return nil, fmt.Errorf("keypairid must be a string")
+	}
+
+	pkBytes, err := ioutil.ReadFile(pkPath)
+	if err != nil {
+		return nil, fmt.Errorf("Failed to read privatekey file: %s", err)
+	}
+
+	block, _ := pem.Decode([]byte(pkBytes))
+	if block == nil {
+		return nil, fmt.Errorf("Failed to decode private key as an rsa private key")
+	}
+	privateKey, err := x509.ParsePKCS1PrivateKey(block.Bytes)
+	if err != nil {
+		return nil, err
+	}
+
+	lh, err := newDelegateLayerHandler(storageDriver, options)
+	if err != nil {
+		return nil, err
+	}
+	dlh := lh.(*delegateLayerHandler)
+
+	cf := cloudfront.New(baseURL, privateKey, keypairID)
+
+	return &cloudFrontLayerHandler{cloudfront: cf, delegateLayerHandler: dlh}, nil
+}
+
+// Resolve returns an http.Handler which can serve the contents of the given
+// Layer, or an error if not supported by the storagedriver.
+func (lh *cloudFrontLayerHandler) Resolve(layer Layer) (http.Handler, error) {
+	layerURLStr, err := lh.delegateLayerHandler.urlFor(layer)
+	if err != nil {
+		return nil, err
+	}
+
+	layerURL, err := url.Parse(layerURLStr)
+	if err != nil {
+		return nil, err
+	}
+
+	cfURL, err := lh.cloudfront.CannedSignedURL(layerURL.Path, "", time.Now().Add(time.Minute))
+	if err != nil {
+		return nil, err
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, cfURL, http.StatusTemporaryRedirect)
+	}), nil
+}
+
+// init registers the cloudfront layerHandler backend.
+func init() {
+	RegisterLayerHandler("cloudfront", LayerHandlerInitFunc(newCloudFrontLayerHandler))
+}

storage/delegatelayerhandler.go

@@ -0,0 +1,84 @@
+package storage
+
+import (
+	"net/http"
+
+	"github.com/docker/distribution/digest"
+	"github.com/docker/distribution/storagedriver"
+)
+
+// delegateLayerHandler provides a simple implementation of layerHandler that
+// simply issues HTTP Temporary Redirects to the URL provided by the
+// storagedriver for a given Layer.
+type delegateLayerHandler struct {
+	storageDriver storagedriver.StorageDriver
+	pathMapper    *pathMapper
+}
+
+var _ LayerHandler = &delegateLayerHandler{}
+
+func newDelegateLayerHandler(storageDriver storagedriver.StorageDriver, options map[string]interface{}) (LayerHandler, error) {
+	return &delegateLayerHandler{storageDriver: storageDriver, pathMapper: defaultPathMapper}, nil
+}
+
+// Resolve returns an http.Handler which can serve the contents of the given
+// Layer, or an error if not supported by the storagedriver.
+func (lh *delegateLayerHandler) Resolve(layer Layer) (http.Handler, error) {
+	layerURL, err := lh.urlFor(layer)
+	if err != nil {
+		return nil, err
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		http.Redirect(w, r, layerURL, http.StatusTemporaryRedirect)
+	}), nil
+}
+
+// urlFor returns a download URL for the given layer, or the empty string if
+// unsupported.
+func (lh *delegateLayerHandler) urlFor(layer Layer) (string, error) {
+	blobPath, err := lh.resolveBlobPath(layer.Name(), layer.Digest())
+	if err != nil {
+		return "", err
+	}
+
+	layerURL, err := lh.storageDriver.URLFor(blobPath)
+	if err != nil {
+		return "", err
+	}
+
+	return layerURL, nil
+}
+
+// resolveBlobPath looks up the blob location in the repositories from a
+// layer/blob link file, returning blob path or an error on failure.
+func (lh *delegateLayerHandler) resolveBlobPath(name string, dgst digest.Digest) (string, error) {
+	pathSpec := layerLinkPathSpec{name: name, digest: dgst}
+	layerLinkPath, err := lh.pathMapper.path(pathSpec)
+
+	if err != nil {
+		return "", err
+	}
+
+	layerLinkContent, err := lh.storageDriver.GetContent(layerLinkPath)
+	if err != nil {
+		return "", err
+	}
+
+	// NOTE(stevvooe): The content of the layer link should match the digest.
+	// This layer of indirection is for name-based content protection.
+
+	linked, err := digest.ParseDigest(string(layerLinkContent))
+	if err != nil {
+		return "", err
+	}
+
+	bp := blobPathSpec{digest: linked}
+
+	return lh.pathMapper.path(bp)
+}
+
+// init registers the delegate layerHandler backend.
+func init() {
+	RegisterLayerHandler("delegate", LayerHandlerInitFunc(newDelegateLayerHandler))
+}

storage/layerhandler.go

@@ -0,0 +1,50 @@
+package storage
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/docker/distribution/storagedriver"
+)
+
+// LayerHandler provides middleware for serving the contents of a Layer.
+type LayerHandler interface {
+	// Resolve returns an http.Handler which can serve the contents of a given
+	// Layer if possible, or nil and an error when unsupported. This may
+	// directly serve the contents of the layer or issue a redirect to another
+	// URL hosting the content.
+	Resolve(layer Layer) (http.Handler, error)
+}
+
+// LayerHandlerInitFunc is the type of a LayerHandler factory function and is
+// used to register the contsructor for different LayerHandler backends.
+type LayerHandlerInitFunc func(storageDriver storagedriver.StorageDriver, options map[string]interface{}) (LayerHandler, error)
+
+var layerHandlers map[string]LayerHandlerInitFunc
+
+// RegisterLayerHandler is used to register an LayerHandlerInitFunc for
+// a LayerHandler backend with the given name.
+func RegisterLayerHandler(name string, initFunc LayerHandlerInitFunc) error {
+	if layerHandlers == nil {
+		layerHandlers = make(map[string]LayerHandlerInitFunc)
+	}
+	if _, exists := layerHandlers[name]; exists {
+		return fmt.Errorf("name already registered: %s", name)
+	}
+
+	layerHandlers[name] = initFunc
+
+	return nil
+}
+
+// GetLayerHandler constructs a LayerHandler
+// with the given options using the named backend.
+func GetLayerHandler(name string, options map[string]interface{}, storageDriver storagedriver.StorageDriver) (LayerHandler, error) {
+	if layerHandlers != nil {
+		if initFunc, exists := layerHandlers[name]; exists {
+			return initFunc(storageDriver, options)
+		}
+	}
+
+	return nil, fmt.Errorf("no layer handler registered with name: %s", name)
+}

storage/layerstore.go

@@ -95,7 +95,7 @@ func (ls *layerStore) newLayerUpload(lus LayerUploadState) LayerUpload {
 	}
 }
 
-// resolveBlobId looks up the blob location in the repositories from a
+// resolveBlobPath looks up the blob location in the repositories from a
 // layer/blob link file, returning blob path or an error on failure.
 func (ls *layerStore) resolveBlobPath(name string, dgst digest.Digest) (string, error) {
 	pathSpec := layerLinkPathSpec{name: name, digest: dgst}

storage/paths.go

@@ -44,6 +44,11 @@ type pathMapper struct {
 	version string // should be a constant?
 }
 
+var defaultPathMapper = &pathMapper{
+	root:    "/docker/registry/",
+	version: storagePathVersion,
+}
+
 // path returns the path identified by spec.
 func (pm *pathMapper) path(spec pathSpec) (string, error) {
 

storage/services.go

@@ -28,11 +28,8 @@ func NewServices(driver storagedriver.StorageDriver) *Services {
 
 	return &Services{
 		driver: driver,
-		pathMapper: &pathMapper{
 		// TODO(sday): This should be configurable.
-			root:    "/docker/registry/",
-			version: storagePathVersion,
-		},
+		pathMapper:       defaultPathMapper,
 		layerUploadStore: layerUploadStore,
 	}
 }