pkg/homedir: new function GetRuntimeDirUser()

[NO NEW TESTS NEEDED] moved from Podman

Signed-off-by: Giuseppe Scrivano <[email protected]>

Author: giuseppe

pkg/homedir/homedir_others.go

@@ -27,3 +27,8 @@ func StickRuntimeDirContents(files []string) ([]string, error) {
 func GetConfigHome() (string, error) {
 	return "", errors.New("homedir.GetRootlessConfigHomeDir() is not supported on this system")
 }
+
+// GetRuntimeDirUser is unsupported on non-linux system.
+func GetRuntimeDirUser(rootless bool, rootlessUID int) (string, error) {
+	return "", errors.New("homedir.GetRuntimeDirUser() is not supported on this system")
+}

pkg/homedir/homedir_unix.go

@@ -11,11 +11,13 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"sync"
 	"syscall"
 
 	"github.com/containers/storage/pkg/unshare"
+	"github.com/sirupsen/logrus"
 )
 
 // Key returns the env var name for the user's home dir based on
@@ -101,6 +103,8 @@ func stick(f string) error {
 var (
 	rootlessConfigHomeDirOnce sync.Once
 	rootlessConfigHomeDir     string
+	rootlessRuntimeDirOnce    sync.Once
+	rootlessRuntimeDir        string
 )
 
 // GetConfigHome returns XDG_CONFIG_HOME.
@@ -134,3 +138,65 @@ func GetConfigHome() (string, error) {
 
 	return rootlessConfigHomeDir, nil
 }
+
+// GetRuntimeDirUser returns the runtime directory for the specified user.
+// If the environment variable is not set, the function will attempt to use common locations.
+// rootless: A boolean flag indicating whether rootless  the process is running as rootless or not.
+// rootlessUID: An integer representing the user ID for the rootless user.
+func GetRuntimeDirUser(rootless bool, rootlessUID int) (string, error) {
+	var rootlessRuntimeDirError error
+
+	if !rootless {
+		return "", nil
+	}
+
+	rootlessRuntimeDirOnce.Do(func() {
+		runtimeDir := os.Getenv("XDG_RUNTIME_DIR")
+
+		if runtimeDir != "" {
+			rootlessRuntimeDir, rootlessRuntimeDirError = filepath.EvalSymlinks(runtimeDir)
+			return
+		}
+
+		uid := strconv.Itoa(rootlessUID)
+		if runtimeDir == "" {
+			tmpDir := filepath.Join("/run", "user", uid)
+			if err := os.MkdirAll(tmpDir, 0o700); err != nil {
+				logrus.Debug(err)
+			}
+			st, err := os.Stat(tmpDir)
+			if err == nil && int(st.Sys().(*syscall.Stat_t).Uid) == os.Geteuid() && (st.Mode().Perm()&0o700 == 0o700) {
+				runtimeDir = tmpDir
+			}
+		}
+		if runtimeDir == "" {
+			tmpDir := filepath.Join(os.TempDir(), fmt.Sprintf("storage-run-%s", uid))
+			if err := os.MkdirAll(tmpDir, 0o700); err != nil {
+				logrus.Debug(err)
+			}
+			st, err := os.Stat(tmpDir)
+			if err == nil && int(st.Sys().(*syscall.Stat_t).Uid) == os.Geteuid() && (st.Mode().Perm()&0o700 == 0o700) {
+				runtimeDir = tmpDir
+			}
+		}
+		if runtimeDir == "" {
+			home := os.Getenv("HOME")
+			if home == "" {
+				rootlessRuntimeDirError = errors.New("neither XDG_RUNTIME_DIR nor HOME was set non-empty")
+				return
+			}
+			resolvedHome, err := filepath.EvalSymlinks(home)
+			if err != nil {
+				rootlessRuntimeDirError = fmt.Errorf("cannot resolve %s: %w", home, err)
+				return
+			}
+			runtimeDir = filepath.Join(resolvedHome, "rundir")
+		}
+		rootlessRuntimeDir = runtimeDir
+	})
+
+	if rootlessRuntimeDirError != nil {
+		return "", rootlessRuntimeDirError
+	}
+	return rootlessRuntimeDir, nil
+}