Add a Docker Credentials label support for windows

Signed-off-by: Nassim 'Nass' Eddequiouaq <eddequiouaq.nassim@gmail.com>

wincred/wincred_windows.go

@@ -3,6 +3,8 @@ package wincred
 import (
 	winc "github.com/danieljoos/wincred"
 	"github.com/docker/docker-credential-helpers/credentials"
+	"bytes"
+	"strings"
 )
 
 // Wincred handles secrets using the Windows credential service.
@@ -14,6 +16,8 @@ func (h Wincred) Add(creds *credentials.Credentials) error {
 	g.UserName = creds.Username
 	g.CredentialBlob = []byte(creds.Secret)
 	g.Persist = winc.PersistLocalMachine
+	g.Attributes = []winc.CredentialAttribute{winc.CredentialAttribute{"label", []byte(creds.Label)}}
+
 	return g.Write()
 }
 
@@ -38,8 +42,8 @@ func (h Wincred) Get(serverURL string) (string, string, error) {
 	return g.UserName, string(g.CredentialBlob), nil
 }
 
-// List returns the stored URLs and corresponding usernames.
-func (h Wincred) List() (map[string]string, error) {
+// List returns the stored URLs and corresponding usernames for a given credentials label.
+func (h Wincred) List(credsLabel string) (map[string]string, error) {
 	creds, err := winc.List()
 	if err != nil {
 		return nil, err
@@ -47,7 +51,16 @@ func (h Wincred) List() (map[string]string, error) {
 
 	resp := make(map[string]string)
 	for i := range creds {
+		attrs = creds[i].Attributes
+		for _, attr := range attrs {
+			if !strings.Compare(attr.Keyword, "label") &&
+				!bytes.Compare(attr.Value, []byte(credentials.CredsLabel)) {
+
 				resp[creds[i].TargetName] = creds[i].UserName
 			}
+		}
+
+	}
+
 	return resp, nil
 }

wincred/wincred_windows_test.go

@@ -8,11 +8,13 @@ import (
 
 func TestWinCredHelper(t *testing.T) {
 	creds := &credentials.Credentials{
+		Label: credentials.CredsLabel,
 		ServerURL: "https://foobar.docker.io:2376/v1",
 		Username:  "foobar",
 		Secret:    "foobarbaz",
 	}
 	creds1 := &credentials.Credentials{
+		Label: credentials.CredsLabel,
 		ServerURL: "https://foobar.docker.io:2376/v2",
 		Username:  "foobarbaz",
 		Secret:    "foobar",
@@ -36,14 +38,14 @@ func TestWinCredHelper(t *testing.T) {
 		t.Fatalf("expected %s, got %s\n", "foobarbaz", secret)
 	}
 
-	auths, err := helper.List()
+	auths, err := helper.List(credentials.CredsLabel)
 	if err != nil || len(auths) == 0 {
 		t.Fatal(err)
 	}
 
 	helper.Add(creds1)
 	defer helper.Delete(creds1.ServerURL)
-	newauths, err := helper.List()
+	newauths, err := helper.List(credentials.CredsLabel)
 	if err != nil {
 		t.Fatal(err)
 	}