chore: refine the user inputs for RCE potentials

Author: kaixuanxu

.github/actions/validate-template/action.yml

@@ -28,5 +28,11 @@ runs:
 
     - name: Validate template
       id: validate-template
-      run: echo "::set-output name=result::$(deno run --allow-read ${{ github.action_path }}/src/main.ts ${{ inputs.path }} ${{ inputs.directory }})"
+      env:
+        INPUT_PATH: ${{ inputs.path }}
+        INPUT_DIRECTORY: ${{ inputs.directory }}
+        ACTION_PATH: ${{ github.action_path }}
+      run: |
+        result=$(deno run --allow-read "${ACTION_PATH}/src/main.ts" "${INPUT_PATH}" "${INPUT_DIRECTORY}")
+        echo "result=${result}" >> "$GITHUB_OUTPUT"
       shell: bash

.github/actions/validate-template/src/main.ts

@@ -1,19 +1,121 @@
 import { writeAllSync } from 'https://deno.land/[email protected]/streams/mod.ts';
+import { resolve, normalize } from 'https://deno.land/[email protected]/path/mod.ts';
 import validate from './validate.ts';
 
 const DEFAULT_TEMPLATE_DIRECTORY = 'templates';
 
-const main = () => {
-	const PROJECT_ROOT = Deno.args[0];
-	const TEMPLATE_DIRECTORY = Deno.args[1];
-	const TEMPLATES_PATH = `${PROJECT_ROOT}/${
-		TEMPLATE_DIRECTORY ?? DEFAULT_TEMPLATE_DIRECTORY
-	}`;
-	const result = validate(TEMPLATES_PATH);
+/**
+ * Validates that a path component is safe and does not contain:
+ * - Path traversal sequences (../)
+ * - Null bytes
+ * - Shell metacharacters that could be used for injection
+ * - Absolute paths when not expected
+ */
+const validatePathComponent = (input: string | undefined, name: string, required: boolean): string | undefined => {
+	if (input === undefined || input === '') {
+		if (required) {
+			throw new Error(`${name} is required but was not provided`);
+		}
+		return undefined;
+	}
+
+	// Check for null bytes (can be used to bypass security checks)
+	if (input.includes('\0')) {
+		throw new Error(`${name} contains invalid null bytes`);
+	}
+
+	// Check for path traversal attempts
+	const normalized = normalize(input);
+	if (normalized.includes('..') || input.includes('..')) {
+		throw new Error(`${name} contains path traversal sequences (..)`);
+	}
+
+	// Check for dangerous shell metacharacters
+	const dangerousChars = /[;&|`$(){}[\]<>!#*?~\n\r]/;
+	if (dangerousChars.test(input)) {
+		throw new Error(`${name} contains potentially dangerous characters`);
+	}
+
+	// Check for excessively long paths (DoS prevention)
+	const MAX_PATH_LENGTH = 4096;
+	if (input.length > MAX_PATH_LENGTH) {
+		throw new Error(`${name} exceeds maximum allowed length of ${MAX_PATH_LENGTH} characters`);
+	}
+
+	return input;
+};
+
+/**
+ * Validates that the resolved path is within the expected base directory
+ */
+const validatePathWithinBase = (basePath: string, targetPath: string): void => {
+	const resolvedBase = resolve(basePath);
+	const resolvedTarget = resolve(targetPath);
+
+	if (!resolvedTarget.startsWith(resolvedBase)) {
+		throw new Error(`Target path escapes the project root directory`);
+	}
+};
+
+/**
+ * Validates that the path exists and is a directory
+ */
+const validateDirectoryExists = (path: string): void => {
+	try {
+		const stat = Deno.statSync(path);
+		if (!stat.isDirectory) {
+			throw new Error(`Path exists but is not a directory: ${path}`);
+		}
+	} catch (error) {
+		if (error instanceof Deno.errors.NotFound) {
+			throw new Error(`Directory does not exist: ${path}`);
+		}
+		throw error;
+	}
+};
+
+const outputError = (message: string): void => {
+	const result = { status: 'error', detail: message };
 	writeAllSync(
 		Deno.stdout,
 		new TextEncoder().encode(JSON.stringify(result)),
 	);
 };
 
+const main = () => {
+	try {
+		// Validate PROJECT_ROOT
+		const PROJECT_ROOT = validatePathComponent(Deno.args[0], 'Project root path', true);
+		if (!PROJECT_ROOT) {
+			throw new Error('Project root path is required');
+		}
+
+		// Validate TEMPLATE_DIRECTORY (optional)
+		const TEMPLATE_DIRECTORY = validatePathComponent(Deno.args[1], 'Template directory', false)
+			?? DEFAULT_TEMPLATE_DIRECTORY;
+
+		// Validate the template directory name itself
+		validatePathComponent(TEMPLATE_DIRECTORY, 'Template directory', false);
+
+		// Construct and validate the full templates path
+		const TEMPLATES_PATH = `${PROJECT_ROOT}/${TEMPLATE_DIRECTORY}`;
+
+		// Ensure the templates path stays within the project root
+		validatePathWithinBase(PROJECT_ROOT, TEMPLATES_PATH);
+
+		// Verify the directory exists
+		validateDirectoryExists(TEMPLATES_PATH);
+
+		const result = validate(TEMPLATES_PATH);
+		writeAllSync(
+			Deno.stdout,
+			new TextEncoder().encode(JSON.stringify(result)),
+		);
+	} catch (error) {
+		const errorMessage = error instanceof Error ? error.message : 'Unknown error occurred';
+		outputError(errorMessage);
+		Deno.exit(1);
+	}
+};
+
 main();