fix: use local and remote Docker credentials to pull image from private registry

internal/machine/docker/client.go

@@ -196,13 +196,27 @@ func (c *Client) RemoveContainer(ctx context.Context, id string, opts container.
 	return err
 }
 
+// PullOptions defines the options for pulling an image from a remote registry.
+// This is a copy of image.PullOptions from the Docker API without the PrivilegeFunc field that is non-serialisable.
+type PullOptions struct {
+	All bool
+	// RegistryAuth is the base64 encoded credentials for the registry.
+	RegistryAuth string
+	Platform     string
+}
+
 type PullImageMessage struct {
 	Message jsonmessage.JSONMessage
 	Err     error
 }
 
-func (c *Client) PullImage(ctx context.Context, image string) (<-chan PullImageMessage, error) {
-	stream, err := c.grpcClient.PullImage(ctx, &pb.PullImageRequest{Image: image})
+func (c *Client) PullImage(ctx context.Context, image string, opts PullOptions) (<-chan PullImageMessage, error) {
+	optsBytes, err := json.Marshal(opts)
+	if err != nil {
+		return nil, fmt.Errorf("marshal options: %w", err)
+	}
+
+	stream, err := c.grpcClient.PullImage(ctx, &pb.PullImageRequest{Image: image, Options: optsBytes})
 	if err != nil {
 		return nil, err
 	}

internal/machine/docker/server.go

@@ -8,12 +8,15 @@ import (
 	"io"
 	"log/slog"
 	"net/netip"
+	"os"
 	"regexp"
 	"slices"
 	"strconv"
 	"strings"
 
 	"github.com/distribution/reference"
+	dockercommand "github.com/docker/cli/cli/command"
+	dockerconfig "github.com/docker/cli/cli/config"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/container"
 	"github.com/docker/docker/api/types/filters"
@@ -266,7 +269,6 @@ func (s *Server) RemoveContainer(ctx context.Context, req *pb.RemoveContainerReq
 func (s *Server) PullImage(req *pb.PullImageRequest, stream grpc.ServerStreamingServer[pb.JSONMessage]) error {
 	ctx := stream.Context()
 
-	// TODO: replace with another JSON serializable type (PullOptions.PrivilegeFunc is not serializable).
 	var opts image.PullOptions
 	if len(req.Options) > 0 {
 		if err := json.Unmarshal(req.Options, &opts); err != nil {
@@ -274,6 +276,14 @@ func (s *Server) PullImage(req *pb.PullImageRequest, stream grpc.ServerStreaming
 		}
 	}
 
+	if opts.RegistryAuth == "" {
+		// Try to retrieve the authentication token for the image from the default local Docker config file.
+		dockerConfig := dockerconfig.LoadDefaultConfigFile(os.Stderr)
+		if encodedAuth, err := dockercommand.RetrieveAuthTokenFromImage(dockerConfig, req.Image); err == nil {
+			opts.RegistryAuth = encodedAuth
+		}
+	}
+
 	respBody, err := s.client.ImagePull(ctx, req.Image, opts)
 	if err != nil {
 		return status.Errorf(codes.Internal, err.Error())