Teknik teratas untuk Melindungi Apl Web daripada Perlaksanaan JavaScript Tanpa Kebenaran

3. Sub-resource integrity (SRI)

This security feature helps browsers check if the resources obtained from a third party (for instance, a CDN) have been modified. It allows you to provide a cryptographic hash for these resources.

When the browser gets the resource, it compares its hash to the given hash. If the hash does not match, the resources will not be loaded, thereby protecting your app from malicious modifications.

How to implement SRI

Implementing SRI involves adding a cryptographic hash to the integrity attribute of your or tags. Here’s a step-by-step guide to setting up SRI:

Step 1: Generating the hash

You must generate a hash for the resource you want to include in your webpage. This can be done using a tool or online service like the Subresource Integrity Generator tool.

Step 2: Adding the hash to your resource

Once you have the hash, add it to the integrity attribute of the or < link>

Refer to the following code example.

<script src="https://example.com/script.js" integrity="sha384-oqVuAfXRKap7fdgcCY5uykM6+R9GqQ8K/uxqAtD6x48V2aB1xzA7e2h53sF2aAuM" crossorigin="anonymous"></script>

In this example, the integrity attribute contains the hash, and the crossorigin=”anonymous” attribute ensures the resource is fetched with CORS (cross-origin resource sharing).

You can use SRI for stylesheets, as well.

<link rel="stylesheet" href="https://example.com/styles.css" integrity="sha384-oqVuAfXRKap7fdgcCY5uykM6+R9GqQ8K/uxqAtD6x48V2aB1xzA7e2h53sF2aAuM" crossorigin="anonymous">

4. Secure JavaScript coding practices

Secure JavaScript coding practices are crucial for developing web apps robust against various attacks, XSS, and other malicious exploits. By following these best practices, developers can ensure their code is secure, maintainable, and less vulnerable to unauthorized execution.

Avoid using eval()

The eval() function is a significant security risk, as it executes a string of code, potentially allowing attackers to inject malicious scripts. Always avoid using eval() and similar functions like setTimeout(string) and setInterval(string).

Why these functions are dangerous:

• Arbitrary code execution: These functions can execute any code passed to them as a string. If an attacker successfully inserts a malicious string, it will operate in the same way as the remaining code of your script.
• Difficulty in code analysis: Using these functions makes it harder to analyze the code for security vulnerabilities. Static analysis tools cannot examine the strings that are passed through such functions.
• Dynamic code injection: Attackers can use these functions to inject and execute code dynamically that was not originally part of the app, bypassing traditional security measures.

Use strict mode

Enabling strict mode in JavaScript helps catch common coding mistakes and unsafe actions, such as assigning values to undeclared variables. This improves the security and stability of your code. To enable strict mode, add “use strict”; at the beginning of a script or a function.

"use strict";

function safeFunction() {
    // Code in strict mode.
    let secureVariable = "Secure";
    console.log(secureVariable);
}

safeFunction();

Advantages and implications of enabling strict mode:

• In strict mode, this is undefined in functions that are not called methods.
• Strict mode will throw an error if a function has duplicate parameter names or an object literal has duplicate property names.
• A with statement is not allowed in the strict mode because it makes code difficult to predict and optimize.

Refer to the following code example.

"use strict";

// Eliminates this coercion.
function showThis() {
    console.log(this); // In non-strict mode, this would be the global object; in strict mode, it's undefined.
}
showThis();

// Disallows duplicate property names or parameter values.
// This will throw an error in strict mode.
const obj = {
    prop: 1,
    prop: 2
};

// Prevents the use of with statement.
// This will throw an error in strict mode.
with (Math) {
    let x = cos(3.14);
}

Avoid inline JavaScript

Inline JavaScript can be significantly vulnerable to XSS attacks because it allows attackers to inject malicious scripts directly into your HTML. Instead, use external scripts to ensure all JavaScript is properly vetted and sanitized.

Avoid inline JavaScript because of:

• Ease of injection: Inline JavaScript is more susceptible to injection attacks because it is part of the HTML content.
• CSP compliance: Content security policies (CSP) can be more effectively enforced when JavaScript is kept in external files. Inline scripts often require the use of the unsafe-inline directive, which weakens CSP’s effectiveness.
• Maintainability: Keeping JavaScript in separate files makes the codebase easier to manage and maintain.

Refer to the following code example.

<!-- Insecure Inline JavaScript -->
<!-- <button onclick="alert('Clicked!')">Click Me</button> -->

<!-- Secure External JavaScript -->
<button id="secureButton">Click Me</button>
<script>
    document.getElementById('secureButton').addEventListener('click', function() {
        alert('Clicked!');
    });
</script>

5. Regular Security Audits and Updates

Regular audits are essential for maintaining the integrity and security of web apps. By continuously assessing your app’s security, you can identify and fix vulnerabilities that could be exploited to execute unauthorized JavaScript or other malicious actions.

Bagaimana untuk menjalankan audit keselamatan secara berkala

Pengimbasan keselamatan automatik

Gunakan alatan seperti OWASP ZAP atau Burp Suite untuk mengimbas kelemahan yang diketahui. Imbasan automatik menyediakan cara cepat untuk mengenal pasti isu keselamatan biasa.

Ulasan kod manual

Semak semula pangkalan kod anda secara manual untuk mengetahui isu yang mungkin terlepas oleh alatan automatik. Adalah lebih baik untuk menggunakan pembangun berpengalaman dan pakar keselamatan untuk ini.

Ujian penembusan

Upah penguji penembusan untuk mensimulasikan serangan pada apl anda, mendedahkan kelemahan yang mungkin tidak dapat dikesan oleh kaedah lain.

Kemas kini kebergantungan

Pastikan kebergantungan anda dikemas kini untuk membetulkan kelemahan yang diketahui dalam perpustakaan dan rangka kerja. Gunakan pengurus pakej seperti NPM atau pip untuk mengurus kemas kini.

Latihan keselamatan

Latih pasukan pembangunan anda secara berterusan tentang amalan keselamatan terkini dan kelemahan biasa. Ini akan memastikan pasukan anda dilengkapi untuk menulis kod selamat.

Menyimpulkan pemikiran

Terima kasih kerana membaca artikel ini. Kami berharap 5 teknik ini meningkatkan pertahanan apl anda terhadap pelaksanaan JavaScript yang tidak dibenarkan. Dengan melaksanakan strategi ini, anda boleh mengurangkan risiko serangan dan memastikan apl web yang lebih selamat dan selamat untuk pengguna anda. Ingat, kekal proaktif dan berwaspada dalam langkah keselamatan anda adalah kunci untuk melindungi aset digital anda.

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