pkg/homedir: new function SetXdgDirs

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/homedir/homedir.go

@@ -2,8 +2,11 @@ package homedir
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"path/filepath"
+
+	"github.com/containers/storage/pkg/unshare"
 )
 
 // GetDataHome returns XDG_DATA_HOME.
@@ -35,3 +38,47 @@ func GetCacheHome() (string, error) {
 	}
 	return filepath.Join(home, ".cache"), nil
 }
+
+// SetXdgDirs ensures the XDG_RUNTIME_DIR, DBUS_SESSION_BUS_ADDRESS and XDG_CONFIG_HOME env
+// variables are set when running as rootless.
+// containers/image uses XDG_RUNTIME_DIR to locate the auth file, XDG_CONFIG_HOME is
+// use for the containers.conf configuration file.
+func SetXdgDirs() error {
+	rootless := unshare.IsRootless()
+	if !rootless {
+		return nil
+	}
+
+	// Set up XDG_RUNTIME_DIR
+	runtimeDir := os.Getenv("XDG_RUNTIME_DIR")
+
+	if runtimeDir == "" {
+		var err error
+		runtimeDir, err = GetRuntimeDir()
+		if err != nil {
+			return err
+		}
+	}
+	if err := os.Setenv("XDG_RUNTIME_DIR", runtimeDir); err != nil {
+		return fmt.Errorf("cannot set XDG_RUNTIME_DIR: %w", err)
+	}
+
+	if os.Getenv("DBUS_SESSION_BUS_ADDRESS") == "" {
+		sessionAddr := filepath.Join(runtimeDir, "bus")
+		if _, err := os.Stat(sessionAddr); err == nil {
+			os.Setenv("DBUS_SESSION_BUS_ADDRESS", fmt.Sprintf("unix:path=%s", sessionAddr))
+		}
+	}
+
+	// Set up XDG_CONFIG_HOME
+	if cfgHomeDir := os.Getenv("XDG_CONFIG_HOME"); cfgHomeDir == "" {
+		cfgHomeDir, err := GetConfigHome()
+		if err != nil {
+			return err
+		}
+		if err := os.Setenv("XDG_CONFIG_HOME", cfgHomeDir); err != nil {
+			return fmt.Errorf("cannot set XDG_CONFIG_HOME: %w", err)
+		}
+	}
+	return nil
+}