feat: support creating store from the default Docker config file

file_store.go

@@ -27,6 +27,8 @@ import (
 
 // FileStore implements a credentials store using the docker configuration file
 // to keep the credentials in plain-text.
+//
+// Reference: https://docs.docker.com/engine/reference/commandline/cli/#docker-cli-configuration-file-configjson-properties
 type FileStore struct {
 	// DisablePut disables putting credentials in plaintext.
 	// If DisablePut is set to true, Put() will return ErrPlaintextPutDisabled.
@@ -45,6 +47,8 @@ var (
 )
 
 // NewFileStore creates a new file credentials store.
+//
+// Reference: https://docs.docker.com/engine/reference/commandline/cli/#docker-cli-configuration-file-configjson-properties
 func NewFileStore(configPath string) (*FileStore, error) {
 	cfg, err := config.Load(configPath)
 	if err != nil {

internal/config/config.go

@@ -89,7 +89,9 @@ func (ac AuthConfig) Credential() (auth.Credential, error) {
 }
 
 // Config represents a docker configuration file.
-// Reference: https://github.com/docker/cli/blob/v24.0.0-beta.2/cli/config/configfile/file.go#L17-L44
+// References:
+//   - https://docs.docker.com/engine/reference/commandline/cli/#docker-cli-configuration-file-configjson-properties
+//   - https://github.com/docker/cli/blob/v24.0.0-beta.2/cli/config/configfile/file.go#L17-L44
 type Config struct {
 	// path is the path to the config file.
 	path string

store.go

@@ -18,12 +18,20 @@ package credentials
 import (
 	"context"
 	"fmt"
+	"os"
+	"path/filepath"
 	"sync"
 
 	"github.com/oras-project/oras-credentials-go/internal/config"
 	"oras.land/oras-go/v2/registry/remote/auth"
 )
 
+const (
+	dockerConfigDirEnv   = "DOCKER_CONFIG"
+	dockerConfigFileDir  = ".docker"
+	dockerConfigFileName = "config.json"
+)
+
 // Store is the interface that any credentials store must implement.
 type Store interface {
 	// Get retrieves credentials from the store for the given server address.
@@ -69,7 +77,9 @@ type StoreOptions struct {
 //   - Linux: "pass" or "secretservice"
 //   - macOS: "osxkeychain"
 //
-// Reference: https://docs.docker.com/engine/reference/commandline/login/#credentials-store
+// References:
+//   - https://docs.docker.com/engine/reference/commandline/login/#credentials-store
+//   - https://docs.docker.com/engine/reference/commandline/cli/#docker-cli-configuration-file-configjson-properties
 func NewStore(configPath string, opts StoreOptions) (Store, error) {
 	cfg, err := config.Load(configPath)
 	if err != nil {
@@ -86,6 +96,24 @@ func NewStore(configPath string, opts StoreOptions) (Store, error) {
 	return ds, nil
 }
 
+// NewStoreFromDocker returns a Store based on the default docker config file.
+//   - If the $DOCKER_CONFIG environment variable is set,
+//     $DOCKER_CONFIG/config.json will be used.
+//   - Otherwise, the default location $HOME/.docker/config.json will be used.
+//
+// NewStoreFromDocker internally calls [credentials.NewStore].
+//
+// References:
+//   - https://docs.docker.com/engine/reference/commandline/cli/#configuration-files
+//   - https://docs.docker.com/engine/reference/commandline/cli/#change-the-docker-directory
+func NewStoreFromDocker(opt StoreOptions) (Store, error) {
+	configPath, err := getDockerConfigPath()
+	if err != nil {
+		return nil, err
+	}
+	return NewStore(configPath, opt)
+}
+
 // Get retrieves credentials from the store for the given server address.
 func (ds *dynamicStore) Get(ctx context.Context, serverAddress string) (auth.Credential, error) {
 	return ds.getStore(serverAddress).Get(ctx, serverAddress)
@@ -140,6 +168,21 @@ func (ds *dynamicStore) getStore(serverAddress string) Store {
 	return fs
 }
 
+// getDockerConfigPath returns the path to the default docker config file.
+func getDockerConfigPath() (string, error) {
+	// first try the environment variable
+	configDir := os.Getenv(dockerConfigDirEnv)
+	if configDir == "" {
+		// then try home directory
+		homeDir, err := os.UserHomeDir()
+		if err != nil {
+			return "", fmt.Errorf("failed to get user home directory: %w", err)
+		}
+		configDir = filepath.Join(homeDir, dockerConfigFileDir)
+	}
+	return filepath.Join(configDir, dockerConfigFileName), nil
+}
+
 // storeWithFallbacks is a store that has multiple fallback stores.
 type storeWithFallbacks struct {
 	stores []Store

store_test.go

@@ -413,3 +413,113 @@ func TestStoreWithFallbacks(t *testing.T) {
 		t.Fatal("incorrect credential after the delete")
 	}
 }
+
+func Test_getDockerConfigPath_env(t *testing.T) {
+	dir, err := os.Getwd()
+	if err != nil {
+		t.Fatal("os.Getwd() error =", err)
+	}
+	t.Setenv("DOCKER_CONFIG", dir)
+
+	got, err := getDockerConfigPath()
+	if err != nil {
+		t.Fatal("getDockerConfigPath() error =", err)
+	}
+	if want := filepath.Join(dir, "config.json"); got != want {
+		t.Errorf("getDockerConfigPath() = %v, want %v", got, want)
+	}
+}
+
+func Test_getDockerConfigPath_homeDir(t *testing.T) {
+	t.Setenv("DOCKER_CONFIG", "")
+
+	got, err := getDockerConfigPath()
+	if err != nil {
+		t.Fatal("getDockerConfigPath() error =", err)
+	}
+	homeDir, err := os.UserHomeDir()
+	if err != nil {
+		t.Fatal("os.UserHomeDir()")
+	}
+	if want := filepath.Join(homeDir, ".docker", "config.json"); got != want {
+		t.Errorf("getDockerConfigPath() = %v, want %v", got, want)
+	}
+}
+
+func TestNewStoreFromDocker(t *testing.T) {
+	// prepare test content
+	tempDir := t.TempDir()
+	configPath := filepath.Join(tempDir, "config.json")
+	t.Setenv("DOCKER_CONFIG", tempDir)
+
+	serverAddr1 := "test.example.com"
+	cred1 := auth.Credential{
+		Username: "foo",
+		Password: "bar",
+	}
+	config := configtest.Config{
+		AuthConfigs: map[string]configtest.AuthConfig{
+			serverAddr1: {
+				Auth: "Zm9vOmJhcg==",
+			},
+		},
+		SomeConfigField: 123,
+	}
+	jsonStr, err := json.Marshal(config)
+	if err != nil {
+		t.Fatalf("failed to marshal config: %v", err)
+	}
+	if err := os.WriteFile(configPath, jsonStr, 0666); err != nil {
+		t.Fatalf("failed to write config file: %v", err)
+	}
+
+	ctx := context.Background()
+
+	ds, err := NewStoreFromDocker(StoreOptions{AllowPlaintextPut: true})
+	if err != nil {
+		t.Fatal("NewStoreFromDocker() error =", err)
+	}
+
+	// test getting an existing credential
+	got, err := ds.Get(ctx, serverAddr1)
+	if err != nil {
+		t.Fatal("dynamicStore.Get() error =", err)
+	}
+	if want := cred1; got != want {
+		t.Errorf("dynamicStore.Get() = %v, want %v", got, want)
+	}
+
+	// test putting a new credential
+	serverAddr2 := "newtest.example.com"
+	cred2 := auth.Credential{
+		Username: "username",
+		Password: "password",
+	}
+	if err := ds.Put(ctx, serverAddr2, cred2); err != nil {
+		t.Fatal("dynamicStore.Get() error =", err)
+	}
+
+	// test getting the new credential
+	got, err = ds.Get(ctx, serverAddr2)
+	if err != nil {
+		t.Fatal("dynamicStore.Get() error =", err)
+	}
+	if want := cred2; got != want {
+		t.Errorf("dynamicStore.Get() = %v, want %v", got, want)
+	}
+
+	// test deleting the old credential
+	err = ds.Delete(ctx, serverAddr1)
+	if err != nil {
+		t.Fatal("dynamicStore.Delete() error =", err)
+	}
+
+	// verify delete
+	got, err = ds.Get(ctx, serverAddr1)
+	if err != nil {
+		t.Fatal("dynamicStore.Get() error =", err)
+	}
+	if want := auth.EmptyCredential; got != want {
+		t.Errorf("dynamicStore.Get() = %v, want %v", got, want)
+	}
+}