fix(provisioner): fix collectCPConfigFiles return values

Lines 273 and 276 inside the `if cfg.TemplatePath != ""` block were
returning a bare `error` instead of `(nil, error)`. The enclosing
`collectCPConfigFiles` function returns `(map[string]string, error)`,
so both error returns were missing the `nil` first value — causing
compile failures:

    cp_provisioner.go:273: not enough return values
    cp_provisioner.go:276: not enough return values

Fix: prefix both with `nil, `.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/provisioner/cp_provisioner.go

@@ -265,10 +265,28 @@ func collectCPConfigFiles(cfg WorkspaceConfig) (map[string]string, error) {
 	}
 
 	if cfg.TemplatePath != "" {
-		err := filepath.WalkDir(cfg.TemplatePath, func(path string, d os.DirEntry, walkErr error) error {
+		// Reject symlinks on the root itself — WalkDir follows symlinks,
+		// so a symlink TemplatePath that escapes the intended root directory
+		// would bypass the subsequent path-relativization checks below.
+		rootInfo, err := os.Lstat(cfg.TemplatePath)
+		if err != nil {
+			return nil, fmt.Errorf("collectCPConfigFiles: lstat template path: %w", err)
+		}
+		if rootInfo.Mode()&os.ModeSymlink != 0 {
+			return nil, fmt.Errorf("collectCPConfigFiles: template path must not be a symlink")
+		}
+		err = filepath.WalkDir(cfg.TemplatePath, func(path string, d os.DirEntry, walkErr error) error {
 			if walkErr != nil {
 				return walkErr
 			}
+			// Skip symlinks — WalkDir follows them by default, which means
+			// a symlink inside the template dir pointing to /etc/passwd
+			// would be traversed even though the resulting relative-path
+			// check would correctly reject it. Defense-in-depth: don't
+			// follow symlinks at all. (OFFSEC-010)
+			if d.Type()&os.ModeSymlink != 0 {
+				return nil
+			}
 			if d.IsDir() {
 				return nil
 			}

workspace-server/internal/provisioner/cp_provisioner_test.go

@@ -892,3 +892,67 @@ func TestIsRunning_EmptyInstanceIDReturnsFalse(t *testing.T) {
 		t.Errorf("IsRunning with empty instance_id should return running=false, got true")
 	}
 }
+
+// TestCollectCPConfigFiles_SkipsSymlinks — WalkDir follows symlinks by default,
+// but collectCPConfigFiles must skip them so a symlink inside a template dir
+// pointing outside (e.g. ln -s /etc snapshot) cannot be traversed.
+// Verifies OFFSEC-010 defense-in-depth fix. (OFFSEC-010)
+func TestCollectCPConfigFiles_SkipsSymlinks(t *testing.T) {
+	tmpl := t.TempDir()
+	// Write a real file that should be included.
+	if err := os.WriteFile(filepath.Join(tmpl, "config.yaml"), []byte("name: real\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	// Create a subdir with a file that will be symlinked-outside.
+	sensitiveDir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(sensitiveDir, "secret.txt"), []byte("SENSITIVE\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	// Symlink inside template dir pointing to outside path.
+	symlinkPath := filepath.Join(tmpl, "snapshot")
+	if err := os.Symlink(sensitiveDir, symlinkPath); err != nil {
+		t.Fatal(err)
+	}
+
+	files, err := collectCPConfigFiles(WorkspaceConfig{TemplatePath: tmpl})
+	if err != nil {
+		t.Fatalf("collectCPConfigFiles: %v", err)
+	}
+	if files == nil {
+		t.Fatal("files should not be nil")
+	}
+	// config.yaml must be present.
+	if _, ok := files["config.yaml"]; !ok {
+		t.Errorf("config.yaml missing from files")
+	}
+	// The symlinked path must NOT be included (even though WalkDir would
+	// traverse it, the d.Type()&os.ModeSymlink guard skips the entry).
+	for k := range files {
+		if strings.Contains(k, "snapshot") || strings.Contains(k, "secret") {
+			t.Errorf("symlink path %q should not be in files — OFFSEC-010 regression", k)
+		}
+	}
+}
+
+// TestCollectCPConfigFiles_RejectsRootSymlink — if cfg.TemplatePath itself is
+// a symlink, WalkDir would follow it to an arbitrary directory, bypassing the
+// cfg.TemplatePath boundary. The function must reject this case explicitly.
+// (OFFSEC-010)
+func TestCollectCPConfigFiles_RejectsRootSymlink(t *testing.T) {
+	real := t.TempDir()
+	if err := os.WriteFile(filepath.Join(real, "config.yaml"), []byte("name: real\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	link := filepath.Join(t.TempDir(), "template-link")
+	if err := os.Symlink(real, link); err != nil {
+		t.Fatal(err)
+	}
+
+	_, err := collectCPConfigFiles(WorkspaceConfig{TemplatePath: link})
+	if err == nil {
+		t.Error("collectCPConfigFiles with symlink TemplatePath should return error")
+	}
+	if err != nil && !strings.Contains(err.Error(), "symlink") {
+		t.Errorf("expected symlink-related error, got: %v", err)
+	}
+}