[WIP] cmd/createShim: Add command for creating shim binaries

This command is meant to be used in toolbox containers and will be
disabled on the host. The created binaries are put in
/usr/libexec/toolbox/. The command utilizes the redirectPath function in
cmd/initContainer.go.

Author: martymichal

src/cmd/createShim.go

@@ -0,0 +1,137 @@
+/*
+ * Copyright © 2019 – 2020 Red Hat Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cmd
+
+/*
+	import (
+		"errors"
+		"fmt"
+		"os"
+		"strings"
+
+		"github.com/containers/toolbox/pkg/shell"
+		"github.com/containers/toolbox/pkg/utils"
+		"github.com/sirupsen/logrus"
+		"github.com/spf13/cobra"
+	)
+
+	var (
+		forbiddenBinaryShims = []string{
+			"toolbox",
+		}
+	)
+
+	var createShimCmd = &cobra.Command{
+		Use:     "create-shim",
+		Short:   "Create a binary shim for a command to be run on the host",
+		Hidden:  true,
+		Example: "asdasdasd",
+		Args:    cobra.ExactArgs(1),
+		RunE:    createShim,
+	}
+
+	func init() {
+		// flags := initContainerCmd.Flags()
+
+		createShimCmd.SetHelpFunc(createShimHelp)
+		rootCmd.AddCommand(createShimCmd)
+	}
+
+	func createShim(cmd *cobra.Command, args []string) error {
+		if !utils.IsInsideContainer() {
+			var builder strings.Builder
+			fmt.Fprintf(&builder, "the 'create-shim' command can only be used inside containers\n")
+			fmt.Fprintf(&builder, "Run '%s --help' for usage.", executableBase)
+
+			errMsg := builder.String()
+			return errors.New(errMsg)
+		}
+
+		shimBinary := fmt.Sprintf("/usr/libexec/toolbox/%s", args[0])
+
+		if !utils.PathExists(hostRunnerShim.containerPath) || !utils.PathExists(sudoShim.containerPath) {
+			var builder strings.Builder
+			fmt.Fprintf(&builder, "This toolbox container is not set up for creating binary shims\n")
+			fmt.Fprintf(&builder, "You're possibly trying to use a newer Toolbox in a container created with an older version\n")
+			fmt.Fprintf(&builder, "Try to update the Toolbox binary used by this container")
+
+			errMsg := builder.String()
+			return errors.New(errMsg)
+		}
+
+		if utils.PathExists(shimBinary) {
+			fmt.Printf("The requested shim binary already exists.\n")
+			return nil
+		}
+
+		err := redirectPath(shimBinary, hostRunnerShim.containerPath, false)
+		if err != nil {
+			return fmt.Errorf("Failed to create shim binary %s: %w", shimBinary, err)
+		}
+
+		return nil
+	}
+
+	func createShimHelp(cmd *cobra.Command, args []string) {
+		if utils.IsInsideContainer() {
+			if !utils.IsInsideToolboxContainer() {
+				fmt.Fprintf(os.Stderr, "Error: this is not a toolbox container\n")
+				return
+			}
+
+			if _, err := utils.ForwardToHost(); err != nil {
+				fmt.Fprintf(os.Stderr, "Error: %s\n", err)
+				return
+			}
+
+			return
+		}
+
+		if err := utils.ShowManual("toolbox-create-shim"); err != nil {
+			fmt.Fprintf(os.Stderr, "Error: %s\n", err)
+			return
+		}
+	}
+
+	func runOnHost(command string, commandLineArgs []string) (int, error) {
+		envOptions := utils.GetEnvOptionsForPreservedVariables()
+
+		var flatpakSpawnArgs []string
+
+		flatpakSpawnArgs = append(flatpakSpawnArgs, envOptions...)
+
+		flatpakSpawnArgs = append(flatpakSpawnArgs, []string{
+			"--host",
+			command,
+		}...)
+
+		flatpakSpawnArgs = append(flatpakSpawnArgs, commandLineArgs...)
+
+		logrus.Debug("Forwarding to host:")
+		logrus.Debugf("%s", command)
+		for _, arg := range commandLineArgs {
+			logrus.Debugf("%s", arg)
+		}
+
+		exitCode, err := shell.RunWithExitCode("flatpak-spawn", os.Stdin, os.Stdout, nil, flatpakSpawnArgs...)
+		if err != nil {
+			return exitCode, err
+		}
+
+		return exitCode, nil
+	}
+*/

src/meson.build

@@ -6,6 +6,7 @@ go_build_wrapper_program = find_program('go-build-wrapper')
 sources = files(
   'toolbox.go',
   'cmd/create.go',
+  'cmd/createShim.go',
   'cmd/enter.go',
   'cmd/help.go',
   'cmd/initContainer.go',