Support for custom authentication URL in proxying registry

Signed-off-by: Serge Dubrouski <sergeyfd@gmail.com>

registry/proxy/proxyauth.go

@@ -3,11 +3,12 @@ package proxy
 import (
 	"net/http"
 	"net/url"
+	"strings"
 
+	"github.com/docker/distribution/context"
 	"github.com/docker/distribution/registry/client/auth"
 )
 
-const tokenURL = "https://auth.docker.io/token"
 const challengeHeader = "Docker-Distribution-Api-Version"
 
 type userpass struct {
@@ -33,16 +34,43 @@ func (c credentials) SetRefreshToken(u *url.URL, service, token string) {
 }
 
 // configureAuth stores credentials for challenge responses
-func configureAuth(username, password string) (auth.CredentialStore, error) {
+func configureAuth(username, password, remoteURL string) (auth.CredentialStore, error) {
-	creds := map[string]userpass{
+	creds := map[string]userpass{}
-		tokenURL: {
+
+	authURLs, err := getAuthURLs(remoteURL)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, url := range authURLs {
+		context.GetLogger(context.Background()).Infof("Discovered token authentication URL: %s", url)
+		creds[url] = userpass{
 			username: username,
 			password: password,
-		},
 		}
+	}
+
 	return credentials{creds: creds}, nil
 }
 
+func getAuthURLs(remoteURL string) ([]string, error) {
+	authURLs := []string{}
+
+	resp, err := http.Get(remoteURL + "/v2/")
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	for _, c := range auth.ResponseChallenges(resp) {
+		if strings.EqualFold(c.Scheme, "bearer") {
+			authURLs = append(authURLs, c.Parameters["realm"])
+		}
+	}
+
+	return authURLs, nil
+}
+
 func ping(manager auth.ChallengeManager, endpoint, versionHeader string) error {
 	resp, err := http.Get(endpoint)
 	if err != nil {

registry/proxy/proxyregistry.go

@@ -91,7 +91,7 @@ func NewRegistryPullThroughCache(ctx context.Context, registry distribution.Name
 		return nil, err
 	}
 
-	cs, err := configureAuth(config.Username, config.Password)
+	cs, err := configureAuth(config.Username, config.Password, config.RemoteURL)
 	if err != nil {
 		return nil, err
 	}