Angular 4 handle XSS CSRF Attacks

Angular Security Principles - Angular Security!

Security Principles For Angular's 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.

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)`);
  }
}



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ANIL SINGH

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