feat: support credential function

registry.go

@@ -48,7 +48,7 @@ func Login(ctx context.Context, store Store, reg *remote.Registry, cred auth.Cre
 	if err := regClone.Ping(ctx); err != nil {
 		return fmt.Errorf("unable to ping the registry %s: %w", regClone.Reference.Registry, err)
 	}
-	hostname := mapHostname(regClone.Reference.Registry)
+	hostname := mapStoreRegistryName(regClone.Reference.Registry)
 	if err := store.Put(ctx, hostname, cred); err != nil {
 		return fmt.Errorf("unable to store the credential for %s: %w", hostname, err)
 	}
@@ -57,17 +57,39 @@ func Login(ctx context.Context, store Store, reg *remote.Registry, cred auth.Cre
 
 // Logout provides the logout functionality given the registry name.
 func Logout(ctx context.Context, store Store, registryName string) error {
-	registryName = mapHostname(registryName)
+	registryName = mapStoreRegistryName(registryName)
 	if err := store.Delete(ctx, registryName); err != nil {
 		return fmt.Errorf("unable to delete the credential for %s: %w", registryName, err)
 	}
 	return nil
 }
 
-func mapHostname(hostname string) string {
+// Credential returns a Credential() function that can be used by auth.Client.
+func Credential(store Store) func(context.Context, string) (auth.Credential, error) {
+	return func(ctx context.Context, reg string) (auth.Credential, error) {
+		reg = mapAuthenticationRegistryName(reg)
+		if reg == "" {
+			return auth.EmptyCredential, nil
+		}
+		return store.Get(ctx, reg)
+	}
+}
+
+func mapStoreRegistryName(registry string) string {
 	// The Docker CLI expects that the 'docker.io' credential
 	// will be added under the key "https://index.docker.io/v1/"
-	if hostname == "docker.io" {
+	// See: https://github.com/moby/moby/blob/v24.0.0-beta.2/registry/config.go#L25-L48
+	if registry == "docker.io" {
+		return "https://index.docker.io/v1/"
+	}
+	return registry
+}
+
+func mapAuthenticationRegistryName(hostname string) string {
+	// It is expected that the traffic targetting "registry-1.docker.io"
+	// will be redirected to "https://index.docker.io/v1/"
+	// See: https://github.com/moby/moby/blob/v24.0.0-beta.2/registry/config.go#L25-L48
+	if hostname == "registry-1.docker.io" {
 		return "https://index.docker.io/v1/"
 	}
 	return hostname

registry_test.go

@@ -159,21 +159,65 @@ func Test_mapHostname(t *testing.T) {
 		want string
 	}{
 		{
-			"map docker.io to https://index.docker.io/v1/",
-			"docker.io",
-			"https://index.docker.io/v1/",
+			name: "map docker.io to https://index.docker.io/v1/",
+			host: "docker.io",
+			want: "https://index.docker.io/v1/",
 		},
 		{
-			"do not map other host names",
-			"localhost:2333",
-			"localhost:2333",
+			name: "do not map other host names",
+			host: "localhost:2333",
+			want: "localhost:2333",
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			if got := mapHostname(tt.host); got != tt.want {
+			if got := mapStoreRegistryName(tt.host); got != tt.want {
 				t.Errorf("mapHostname() = %v, want %v", got, tt.want)
 			}
 		})
 	}
 }
+
+func TestCredential(t *testing.T) {
+	// create a test store
+	s := &testStore{}
+	s.storage = map[string]auth.Credential{
+		"localhost:2333":              {Username: "test_user", Password: "test_word"},
+		"https://index.docker.io/v1/": {Username: "user", Password: "word"},
+	}
+	// create a test client using Credential
+	testClient := &auth.Client{}
+	testClient.Credential = Credential(s)
+	tests := []struct {
+		name           string
+		registry       string
+		wantCredential auth.Credential
+	}{
+		{
+			name:           "get credentials for localhost:2333",
+			registry:       "localhost:2333",
+			wantCredential: auth.Credential{Username: "test_user", Password: "test_word"},
+		},
+		{
+			name:           "get credentials for registry-1.docker.io",
+			registry:       "registry-1.docker.io",
+			wantCredential: auth.Credential{Username: "user", Password: "word"},
+		},
+		{
+			name:           "get credentials for a registry not stored",
+			registry:       "localhost:6666",
+			wantCredential: auth.EmptyCredential,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := testClient.Credential(context.Background(), tt.registry)
+			if err != nil {
+				t.Errorf("could not get credential: %v", err)
+			}
+			if !reflect.DeepEqual(got, tt.wantCredential) {
+				t.Errorf("Credential() = %v, want %v", got, tt.wantCredential)
+			}
+		})
+	}
+}