Scenes:
In the process of front-end and back-end interaction, the front-end usesv-html or { {}}When rendering, the webpage automatically executes its malicious code, such as page pop-ups, jumps to phishing websites, etc.
solution:
Let’s talk about the solution first, and its principle will be explained below.
Since I am a vue project, I use `vue-dompurify-html`This targeted library, if you are using other frameworks , just search DOMPurify directly.
`vue-dompurify-html` is a Vue-specific third-party library that provides a Vue directive for cleaning and purifying HTML using DOMPurify in Vue content. This library encapsulates the functionality of the DOMPurify library, making it easier to integrate and use in Vue projects.
Simplifies the process of sanitizing user input in Vue components without having to manually create filters.
Here is an example using `vue-dompurify-html`:
1. 安装 `vue-dompurify-html`：
npm install vue-dompurify-html
2. 在main.js中引入
import Vue from 'vue'
import VueDOMPurifyHTML from 'vue-dompurify-html'
Vue.use(VueDOMPurifyHTML)
3. 在模板中应用指令：
<div v-dompurify-html="userContent"></div>
In the above example, we first import `vue-dompurify-html` and register it as a global directive for Vue. Then, at the point in the template where user input needs to be sanitized, we use the v-dompurify-html directive and pass the value of the userContent variable as the argument to the directive. This directive will automatically use DOMPurify to sanitize and safely render user input.
By using `vue-dompurify-html`, you can easily sanitize and sanitize user-entered HTML content in Vue components, prevent XSS attacks, and improve the security of your application. This library is related to DOMPurify, but is integrated specifically for Vue to provide a cleaner, more intuitive way to use it.
How the front end is attacked and how to prevent it
principle:
Front-end code (HTML, CSS, and JavaScript) executes in the browser. When a user accesses a web page, the browser downloads the corresponding front-end code and parses and executes it in the user's browser. This means that if a web page contains malicious front-end code, the browser will execute it unconditionally.
In an XSS attack, an attacker inserts malicious code into an injection point in a trusted web page, causing the browser to execute it as legitimate code when parsing the web page. This is due to the working principle of the browser and the characteristics of the front end.
The browser works by parsing HTML into a DOM (Document Object Model) tree, parsing CSS into style rules, and finally parsing and executing JavaScript code. During the execution of JavaScript code, the browser will execute the code contained in the `<script>` tag and execute the event handler function (such as `onmouseover`) accordingly.
So, if malicious front-end code is successfully inserted into a web page and delivered to the user's browser, the browser will unconditionally parse and execute the code, resulting in a successful XSS attack.
Ways of attack:
In addition to the `<script>` tag and the `onclick` event handler, XSS attackers may use the following methods to inject malicious code:
1. Use other HTML event handlers: XSS attackers can inject malicious code into other HTML event handlers, such as `onmouseover`, `onload`, `onerror`, etc. When the user triggers the corresponding event, the malicious code is executed.
2. Use HTML attributes: XSS attackers can use HTML attributes, such as `src`, `href`, `data`, etc., to inject malicious content. For example, inject a link with malicious code in the `src` attribute of an image.
3. Use special characters and encodings: XSS attackers can use various character and encoding techniques to bypass input filtering and validation mechanisms to inject malicious code. For example, use Unicode encoding, HTML entity encoding, JavaScript character encoding, etc.
4. Exploiting browser features: There are some specific features and vulnerabilities in browsers that XSS attackers can exploit to execute malicious code. For example, inject malicious code into browser jumps (such as `location.href`) or exploit DOM-type XSS vulnerabilities.
5. Exploiting improper handling of input and output context: XSS attackers may exploit the application's improper handling of user input and output to achieve attacks by injecting malicious code. For example, user input is not escaped and sanitized properly, or user data is output in an unsafe context.
These are just some common XSS attack methods. Attackers may use more techniques and vulnerabilities to inject malicious code. Therefore, front-end development requires a variety of defensive measures to prevent XSS attacks, including input validation and filtering, output encoding, using secure cookies, setting Content Security Policy (CSP), using secure DOM operations, etc.
How to prevent:
Here are some best practices and solutions for preventing XSS attacks on the front end:
1. Input validation and filtering: Perform enhanced validation and appropriate filtering of user input. Use a whitelist mechanism to verify and accept legitimate input data, and strictly limit and reject input that may contain malicious code.
2. Output encoding: When displaying user input as text, use appropriate encoding methods to escape special characters to ensure that they Displayed only as text and not interpreted as HTML or JavaScript code. For example, use HTML entity encoding or a specialized encoding library such as `htmlspecialchars`.
3. Prevent direct execution of user input: Avoid executing user input directly as JavaScript code, including using user input as dynamically generated scripts, event handlers, or URL parameters. Use appropriate parsing and processing methods to ensure input security.
4. Content Security Policy (CSP): By configuring the appropriate CSP, restrict the browser to only load resources from specified sources, thereby Reduce the execution of malicious scripts outside of trusted content sources. CSP prevents cross-site scripting and other types of attacks and is an effective security layer.
5. Use safe DOM operations: Avoid using operations such as `innerHTML` and `outerHTML` to directly insert unvalidated user data. Instead, use DOM manipulation methods (such as `createElement`, `appendChild`, etc.) to create and manipulate DOM elements.
6. HTTP-only Cookie: Store sensitive information in HTTP-only Cookie to prevent XSS attackers from accessing and stealing the user's authentication credentials through JavaScript.
7. Data cleaning and verification on the client side: In addition to server-side verification, data can also be cleaned and verified on the client side to reduce the risk of malicious code injection.
8. Maintain the latest versions of front-end frameworks and libraries: Keep up to date and use the latest versions of front-end frameworks and libraries, which often include security fixes and enhancements.
9. Safe programming practices: Follow safe programming practices, such as avoiding the use of `eval`, avoiding splicing SQL queries, etc., as well as strict code review and security testing.
10. Monitoring and logging: Set up appropriate monitoring and logging mechanisms to detect and respond to potential attack activities in a timely manner for further investigation and response.
A combination of these defenses can enhance the security of your application and reduce the risk of XSS attacks. At the same time, it is also recommended to conduct regular security testing and vulnerability scanning to maintain the security of the application and respond to new threats in a timely manner.