Integrate auth.AccessController into registry app

This changeset integrates the AccessController into the main registry app. This
includes support for configuration and a test implementation, called "silly"
auth. Auth is only enabled if the configuration is present but takes measure to
ensure that configuration errors don't allow the appserver to start with open
access.

auth/silly/access.go

@@ -0,0 +1,89 @@
+// Package silly provides a simple authentication scheme that checks for the
+// existence of an Authorization header and issues access if is present and
+// non-empty.
+//
+// This package is present as an example implementation of a minimal
+// auth.AccessController and for testing. This is not suitable for any kind of
+// production security.
+package silly
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/docker/docker-registry/auth"
+)
+
+// accessController provides a simple implementation of auth.AccessController
+// that simply checks for a non-empty Authorization header. It is useful for
+// demonstration and testing.
+type accessController struct {
+	realm   string
+	service string
+}
+
+var _ auth.AccessController = &accessController{}
+
+func newAccessController(options map[string]interface{}) (auth.AccessController, error) {
+	realm, present := options["realm"]
+	if _, ok := realm.(string); !present || !ok {
+		return nil, fmt.Errorf(`"realm" must be set for silly access controller`)
+	}
+
+	service, present := options["service"]
+	if _, ok := service.(string); !present || !ok {
+		return nil, fmt.Errorf(`"service" must be set for silly access controller`)
+	}
+
+	return &accessController{realm: realm.(string), service: service.(string)}, nil
+}
+
+// Authorized simply checks for the existence of the authorization header,
+// responding with a bearer challenge if it doesn't exist.
+func (ac *accessController) Authorized(req *http.Request, accessRecords ...auth.Access) error {
+	if req.Header.Get("Authorization") == "" {
+		challenge := challenge{
+			realm:   ac.realm,
+			service: ac.service,
+		}
+
+		if len(accessRecords) > 0 {
+			var scopes []string
+			for _, access := range accessRecords {
+				scopes = append(scopes, fmt.Sprintf("%s:%s:%s", access.Type, access.Resource, access.Action))
+			}
+			challenge.scope = strings.Join(scopes, " ")
+		}
+
+		return &challenge
+	}
+
+	return nil
+}
+
+type challenge struct {
+	realm   string
+	service string
+	scope   string
+}
+
+func (ch *challenge) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	header := fmt.Sprintf("Bearer realm=%q,service=%q", ch.realm, ch.service)
+
+	if ch.scope != "" {
+		header = fmt.Sprintf("%s,scope=%q", header, ch.scope)
+	}
+
+	w.Header().Set("Authorization", header)
+	w.WriteHeader(http.StatusUnauthorized)
+}
+
+func (ch *challenge) Error() string {
+	return fmt.Sprintf("silly authentication challenge: %#v", ch)
+}
+
+// init registers the silly auth backend.
+func init() {
+	auth.Register("silly", auth.InitFunc(newAccessController))
+}

auth/silly/access_test.go

@@ -0,0 +1,58 @@
+package silly
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/docker/docker-registry/auth"
+)
+
+func TestSillyAccessController(t *testing.T) {
+	ac := &accessController{
+		realm:   "test-realm",
+		service: "test-service",
+	}
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := ac.Authorized(r); err != nil {
+			switch err := err.(type) {
+			case auth.Challenge:
+				err.ServeHTTP(w, r)
+				return
+			default:
+				t.Fatalf("unexpected error authorizing request: %v", err)
+			}
+		}
+
+		w.WriteHeader(http.StatusNoContent)
+	}))
+
+	resp, err := http.Get(server.URL)
+	if err != nil {
+		t.Fatalf("unexpected error during GET: %v", err)
+	}
+	defer resp.Body.Close()
+
+	// Request should not be authorized
+	if resp.StatusCode != http.StatusUnauthorized {
+		t.Fatalf("unexpected response status: %v != %v", resp.StatusCode, http.StatusUnauthorized)
+	}
+
+	req, err := http.NewRequest("GET", server.URL, nil)
+	if err != nil {
+		t.Fatalf("unexpected error creating new request: %v", err)
+	}
+	req.Header.Set("Authorization", "seriously, anything")
+
+	resp, err = http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("unexpected error during GET: %v", err)
+	}
+	defer resp.Body.Close()
+
+	// Request should not be authorized
+	if resp.StatusCode != http.StatusNoContent {
+		t.Fatalf("unexpected response status: %v != %v", resp.StatusCode, http.StatusNoContent)
+	}
+}