Skip to main content

How Angular Preventing Cross Site Scripting (XSS) and CSRF Attacks?


How does Angular 2 handle with XSS or CSRF? 
How Angular prevents this Attacks?
The Cross Site Scripting (XSS) attack is a type of injection and attackers inject your web applications using the client side scripts and malicious code into web pages.

An attacker can insert vulnerability scripts and malicious code in your web applications.
The Angular treats all values as un-trusted by default. This is the great advantages of Angular.

Stayed Informed – Angular 4 docs and Angular 5 docs

When a value is Inserted Vulnerability into the DOM from –
1.     A Template
2.     Property
3.     Attribute
4.     Style
5.     Class Binding
6.     Interpolation
7.     And so on.

Angular recognizes the value as unsafe and automatically sanitizes and removes the script tag and other security vulnerabilities.

Angular provides built-in, values as untrusted by default, anti XSS and CSRF/XSRF protection.
The CookieXSRFStrategy class takes care of preventing XSS and CSRF/XSRF attacks.
The DomSanitizationService takes care of removing the dangerous bits in order to prevent XSS attacks.

Angular applications must follow the same security principles as regular web applications -
1.     You should avoid direct use of the DOM APIs.
2.     You should enable Content Security Policy (CSP) and configure your web server to return appropriate CSP HTTP headers.
3.     You should Use the offline template compiler.
4.     You should Use Server Side XSS protection.
5.     You should Use DOM Sanitizer.
6.     You should Preventing CSRF or XSRF attacks.

Angular defines the following security -

HTML is used when interpreting a value as HTML i.e.
<div [innerHTML]="UNTRUSTED"></div>
OR
<input value="UNTRUSTED">

Style is used when binding CSS into the style property i.e.
<div [style]="height:UNTRUSTED"></div>

URL is used for URL properties i.e.
<a [href]="UNTRUSTED-URL"></a>
OR
<script [src]="UNTRUSTED-URL"></script>
OR
<iframe src="UNTRUSTED-URL" />

Resource URL is a URL that will be loaded and executed i.e.
<script>var value='UNTRUSTED';</script>


<p class="e2e-inner-html-interpolated">{{htmlSnippet}}</p>
<p class="e2e-inner-html-bound" [innerHTML]="htmlSnippet"></p>




Example
export const BROWSER_SANITIZATION_PROVIDERS: Array<any> = [
  {provide: Sanitizer, useExisting: DomSanitizer},
  {provide: DomSanitizer, useClass: DomSanitizerImpl},
];

@NgModule({
  providers: [
    BROWSER_SANITIZATION_PROVIDERS
    ...
  ],
  exports: [CommonModule, ApplicationModule]
})
export class BrowserModule {}


DOM sanitization - Use to clean untrusted parts of values -
export enum SecurityContext { NONE, HTML, STYLE, SCRIPT, URL, RESOURCE_URL }

export abstract class DomSanitizer implements Sanitizer {
  abstract sanitize(context: SecurityContext, value: SafeValue|string|null): string|null;
  abstract bypassSecurityTrustHtml(value: string): SafeHtml;
  abstract bypassSecurityTrustStyle(value: string): SafeStyle;
  abstract bypassSecurityTrustScript(value: string): SafeScript;
  abstract bypassSecurityTrustUrl(value: string): SafeUrl;
  abstract bypassSecurityTrustResourceUrl(value: string): SafeResourceUrl;
}


The DOM Sanitize Methods –
sanitize(ctx: SecurityContext, value: SafeValue|string|null): string|null {
  if (value == null) return null;
 
  switch (ctx) {
    case SecurityContext.NONE:
      return value as string;
     
    case SecurityContext.HTML:
      if (value instanceof SafeHtmlImpl) return value.changingThisBreaksApplicationSecurity;
      this.checkNotSafeValue(value, 'HTML');
      return sanitizeHtml(this._doc, String(value));
     
    case SecurityContext.STYLE:
      if (value instanceof SafeStyleImpl) return value.changingThisBreaksApplicationSecurity;
      this.checkNotSafeValue(value, 'Style');
      return sanitizeStyle(value as string);
     
    case SecurityContext.SCRIPT:
      if (value instanceof SafeScriptImpl) return value.changingThisBreaksApplicationSecurity;
      this.checkNotSafeValue(value, 'Script');
      throw new Error('unsafe value used in a script context');
     
    case SecurityContext.URL:
      if (value instanceof SafeResourceUrlImpl || value instanceof SafeUrlImpl) {
        // Allow resource URLs in URL contexts, they are strictly more trusted.
        return value.changingThisBreaksApplicationSecurity;
      }
      this.checkNotSafeValue(value, 'URL');
      return sanitizeUrl(String(value));
     
    case SecurityContext.RESOURCE_URL:
      if (value instanceof SafeResourceUrlImpl) {
        return value.changingThisBreaksApplicationSecurity;
      }
      this.checkNotSafeValue(value, 'ResourceURL');
      throw new Error(
          'unsafe value used in a resource URL context (see http://g.co/ng/security#xss)');
         
    default:
      throw new Error(`Unexpected SecurityContext ${ctx} (see http://g.co/ng/security#xss)`);
  }
}



I hope you are enjoying with this post! Please share with you friends. Thank you so much!
By Anil Singh | Rating of this article (*****)

Popular posts from this blog

39 Best Object Oriented JavaScript Interview Questions and Answers

Most Popular 37 Key Questions for JavaScript Interviews. What is Object in JavaScript? What is the Prototype object in JavaScript and how it is used? What is "this"? What is its value? Explain why "self" is needed instead of "this". What is a Closure and why are they so useful to us? Explain how to write class methods vs. instance methods. Can you explain the difference between == and ===? Can you explain the difference between call and apply? Explain why Asynchronous code is important in JavaScript? Can you please tell me a story about JavaScript performance problems? Tell me your JavaScript Naming Convention? How do you define a class and its constructor? What is Hoisted in JavaScript? What is function overloadin

Angular 2, 4, 5, 6, 7, 8 and 9 Interview Questions and Answers -Books

» Are you preparing for Angular Interview? Buy this book (Including Angular 8, 7, 6, 5,4, 2) Interview Q/A Interview Q/A Interview Q/A Interview Q/A Interview Q/A Interview Q/A Interview Q/A » A Complete Guide Book of Angular 9 This is a concise, complete overview of the key aspects of Angular 9. It is fully up to date with the latest release of Angular. This article provide all the important aspects required for angular developers looking for brief and useful content... Posted In Angular 9 » A Complete Guide Book of Angular 8 This is a concise, complete overview of the key aspects of Angular 9. It is fully up to date with the latest release of Angular. This article provide all the important aspects required for angular developers looking for brief and useful content... Posted In Angular 8 » A Complete Guide Book of Angular 7 This is a concise, complete overview of the key aspects of Angular 7. It is fully up to date with the latest release of Angular. This

25 Best Vue.js 2 Interview Questions and Answers

What Is Vue.js? The Vue.js is a progressive JavaScript framework and used to building the interactive user interfaces and also it’s focused on the view layer only (front end). The Vue.js is easy to integrate with other libraries and others existing projects. Vue.js is very popular for Single Page Applications developments. The Vue.js is lighter, smaller in size and so faster. It also supports the MVVM ( Model-View-ViewModel ) pattern. The Vue.js is supporting to multiple Components and libraries like - ü   Tables and data grids ü   Notifications ü   Loader ü   Calendar ü   Display time, date and age ü   Progress Bar ü   Tooltip ü   Overlay ü   Icons ü   Menu ü   Charts ü   Map ü   Pdf viewer ü   And so on The Vue.js was developed by “ Evan You ”, an Ex Google software engineer. The latest version is Vue.js 2. The Vue.js 2 is very similar to Angular because Evan You was inspired by Angular and the Vue.js 2 components looks like -

nullinjectorerror no provider for httpclient angular 17

In Angular 17 where the standalone true option is set by default, the app.config.ts file is generated in src/app/ and provideHttpClient(). We can be added to the list of providers in app.config.ts Step 1:   To provide HttpClient in a standalone app we could do this in the app.config.ts file, app.config.ts: import { ApplicationConfig } from '@angular/core'; import { provideRouter } from '@angular/router'; import { routes } from './app.routes'; import { provideClientHydration } from '@angular/platform-browser'; //This (provideHttpClient) will help us to resolve the issue  import {provideHttpClient} from '@angular/common/http'; export const appConfig: ApplicationConfig = {   providers: [ provideRouter(routes),  provideClientHydration(), provideHttpClient ()      ] }; The appConfig const is used in the main.ts file, see the code, main.ts : import { bootstrapApplication } from '@angular/platform-browser'; import { appConfig } from '

List of Countries, Nationalities and their Code In Excel File

Download JSON file for this List - Click on JSON file    Countries List, Nationalities and Code Excel ID Country Country Code Nationality Person 1 UNITED KINGDOM GB British a Briton 2 ARGENTINA AR Argentinian an Argentinian 3 AUSTRALIA AU Australian an Australian 4 BAHAMAS BS Bahamian a Bahamian 5 BELGIUM BE Belgian a Belgian 6 BRAZIL BR Brazilian a Brazilian 7 CANADA CA Canadian a Canadian 8 CHINA CN Chinese a Chinese 9 COLOMBIA CO Colombian a Colombian 10 CUBA CU Cuban a Cuban 11 DOMINICAN REPUBLIC DO Dominican a Dominican 12 ECUADOR EC Ecuadorean an Ecuadorean 13 EL SALVADOR