support alicdn middleware

Signed-off-by: Shawnpku <chen8132@gmail.com>

registry/storage/driver/middleware/alicdn/middleware.go

@@ -0,0 +1,116 @@
+package middleware
+
+import (
+	"fmt"
+	"net/url"
+	"strings"
+	"time"
+
+	"github.com/docker/distribution/context"
+	storagedriver "github.com/docker/distribution/registry/storage/driver"
+	storagemiddleware "github.com/docker/distribution/registry/storage/driver/middleware"
+
+	"github.com/denverdino/aliyungo/cdn/auth"
+)
+
+// aliCdnStorageMiddleware provides a simple implementation of layerHandler that
+// constructs temporary signed AliCDN URLs from the storagedriver layer URL,
+// then issues HTTP Temporary Redirects to this AliCDN content URL.
+type aliCdnStorageMiddleware struct {
+	storagedriver.StorageDriver
+	baseURL   string
+	urlSigner *auth.URLSigner
+	duration  time.Duration
+}
+
+var _ storagedriver.StorageDriver = &aliCdnStorageMiddleware{}
+
+// newAliCdnLayerHandler constructs and returns a new AliCDN
+// LayerHandler implementation.
+// Required options: baseurl, authtype, privatekey
+// Optional options: duration
+func newAliCdnStorageMiddleware(storageDriver storagedriver.StorageDriver, options map[string]interface{}) (storagedriver.StorageDriver, error) {
+	// parse baseurl
+	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")
+	}
+	if !strings.Contains(baseURL, "://") {
+		baseURL = "https://" + baseURL
+	}
+	if _, err := url.Parse(baseURL); err != nil {
+		return nil, fmt.Errorf("invalid baseurl: %v", err)
+	}
+
+	// parse authtype
+	at, ok := options["authtype"]
+	if !ok {
+		return nil, fmt.Errorf("no authtype provided")
+	}
+	authType, ok := at.(string)
+	if !ok {
+		return nil, fmt.Errorf("authtype must be a string")
+	}
+	if authType != "a" && authType != "b" && authType != "c" {
+		return nil, fmt.Errorf("invalid authentication type")
+	}
+
+	// parse privatekey
+	pk, ok := options["privatekey"]
+	if !ok {
+		return nil, fmt.Errorf("no privatekey provided")
+	}
+	privateKey, ok := pk.(string)
+	if !ok {
+		return nil, fmt.Errorf("privatekey must be a string")
+	}
+
+	urlSigner := auth.NewURLSigner(authType, privateKey)
+
+	// parse duration
+	duration := 60 * time.Minute
+	d, ok := options["duration"]
+	if ok {
+		switch d := d.(type) {
+		case time.Duration:
+			duration = d
+		case string:
+			dur, err := time.ParseDuration(d)
+			if err != nil {
+				return nil, fmt.Errorf("invalid duration: %s", err)
+			}
+			duration = dur
+		}
+	}
+
+	return &aliCdnStorageMiddleware{
+		StorageDriver: storageDriver,
+		baseURL:       baseURL,
+		urlSigner:     urlSigner,
+		duration:      duration,
+	}, nil
+}
+
+// URLFor attempts to find a url which may be used to retrieve the file at the given path.
+// Returns an error if the file cannot be found.
+func (ac *aliCdnStorageMiddleware) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
+
+	if ac.StorageDriver.Name() != "oss" {
+		context.GetLogger(ctx).Warn("the AliCdn middleware does not support this backend storage driver")
+		return ac.StorageDriver.URLFor(ctx, path, options)
+	}
+	acURL, err := ac.urlSigner.Sign(ac.baseURL+path, time.Now().Add(ac.duration))
+	if err != nil {
+		return "", err
+	}
+	return acURL, nil
+}
+
+// init registers the alicdn layerHandler backend.
+func init() {
+	storagemiddleware.Register("alicdn", storagemiddleware.InitFunc(newAliCdnStorageMiddleware))
+}