Add checks for CNIBinDir ownership/permissions. (#606)

---------

Signed-off-by: Nashwan Azhari <nazhari@cloudbasesolutions.com>

.github/workflows/go.yaml

@@ -63,7 +63,9 @@ jobs:
 
       - name: go test
         working-directory: src/k8s
-        run: make go.unit
+        # NOTE: there are a handful of tests checking/setting
+        # root ownership so the tests must be run as root:
+        run: sudo make go.unit
 
   test-binary:
     name: Binaries

src/k8s/pkg/k8sd/setup/directories.go

@@ -1,16 +1,23 @@
 package setup
 
 import (
+	"errors"
 	"fmt"
+	"io/fs"
 	"os"
+	"syscall"
 
+	"github.com/canonical/k8s/pkg/log"
 	"github.com/canonical/k8s/pkg/snap"
 )
 
 // EnsureAllDirectories ensures all required configuration and state directories are created.
 func EnsureAllDirectories(snap snap.Snap) error {
+	if err := ensureCniBinDir(snap.CNIBinDir()); err != nil {
+		return err
+	}
+
 	for _, dir := range []string{
-		snap.CNIBinDir(),
 		snap.CNIConfDir(),
 		snap.ContainerdConfigDir(),
 		snap.ContainerdExtraConfigDir(),
@@ -32,3 +39,48 @@ func EnsureAllDirectories(snap snap.Snap) error {
 	}
 	return nil
 }
+
+// Ensures that the provided path is a directory with the appropriate
+// ownership/permissions for it to be used as the CNI binary directory.
+// https://github.com/canonical/k8s-snap/issues/567
+// https://github.com/cilium/cilium/issues/23838
+func ensureCniBinDir(cniBinDir string) error {
+	l := log.L().WithValues("cniBinDir", cniBinDir)
+	if cniBinDir == "" {
+		l.V(1).Info("Skipping creation of cni bin directory since it was not set")
+		return nil
+	}
+
+	var stat syscall.Stat_t
+	if err := syscall.Stat(cniBinDir, &stat); err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			return fmt.Errorf("failed to syscall.Stat(%q): %w", cniBinDir, err)
+		}
+
+		l.Info("Creating cni bin directory")
+		if err := os.MkdirAll(cniBinDir, 0o0700); err != nil {
+			return fmt.Errorf("failed to os.MkdirAll(%s): %w", cniBinDir, err)
+		}
+
+		if err := syscall.Stat(cniBinDir, &stat); err != nil {
+			return fmt.Errorf("failed to syscall.Stat(%q) newly-created cni bin dir: %w", cniBinDir, err)
+		}
+	}
+
+	if stat.Uid != 0 || stat.Gid != 0 {
+		l.Info("Ensuring ownership of cni bin directory")
+		if err := os.Chown(cniBinDir, 0, 0); err != nil {
+			return fmt.Errorf("failed to os.Chown(%q, 0, 0): %w", cniBinDir, err)
+		}
+	}
+
+	if (stat.Mode & 0o700) != 0o700 {
+		l.Info("Ensuring permissions of cni bin directory")
+		mode := os.FileMode(stat.Mode | 0o700)
+		if err := os.Chmod(cniBinDir, mode); err != nil {
+			return fmt.Errorf("failed to os.Chmod(%q, %o): %w", cniBinDir, mode, err)
+		}
+	}
+
+	return nil
+}