Скачать или смотреть Understanding Cross-Domain and Cross-Origin Cookies

Disclaimer/Disclosure: Some of the content was synthetically produced using various Generative AI (artificial intelligence) tools; so, there may be inaccuracies or misleading information present in the video. Please consider this before relying on the content to make any decisions or take any actions etc. If you still have any concerns, please feel free to write them in a comment. Thank you.
---

Summary: Explore the intricacies of cross-domain and cross-origin cookies, including iframes, multi-domain scenarios, subdomains, and how JavaScript can be used to share cookies across domains.
---

Understanding Cross-Domain and Cross-Origin Cookies

Cookies are small pieces of data stored on the client-side that help websites remember information about users. While cookies work seamlessly within a single domain, managing cookies across multiple domains and subdomains presents unique challenges. This guide delves into the concepts of cross-domain cookies, cross-origin cookies, iframe cookies, and how to share cookies across multiple domains and subdomains using JavaScript.

Cross-Domain and Cross-Origin Cookies

Cross-Domain Cookies are cookies that are accessible across different domains. Normally, browsers impose strict rules around cross-domain cookies for security and privacy purposes. Cookies set by one domain are generally not accessible by another domain, which helps prevent unauthorized data sharing and tracking across different sites.

Cross-Origin Cookies pertain to cookies used in scenarios involving different origins, which include a combination of domain, port, and protocol. Browsers implement strict SameSite policies to control cross-origin requests to enhance security against Cross-Site Request Forgery (CSRF) attacks.

Iframe Cookies Cross Domain

Using iframes can be a method to handle cross-domain cookies. An iframe allows embedding another HTML document with its own separate origin. When it comes to cookies, setting or reading cookies inside an iframe from another domain will face restrictions imposed by the SameSite policy:

SameSite=Lax: Cookies are sent with top-level navigation.

SameSite=Strict: Cookies are not sent with cross-site requests.

SameSite=None: Cookies are sent with the request but must be marked as secure.

Multi-Domain Cookies

Managing cookies across multiple domains, such as example.com and example.org, can be tricky due to browser cookie security measures. Here are some potential approaches:

Backend Synchronization: Using server-side mechanisms to synchronize cookies across different domains.

APIs/Web Storage: Using a combination of APIs and browser localStorage or sessionStorage.

Cookies Across Subdomains

Cookies can be shared across subdomains relatively more easily because a cookie set for a parent domain can be accessed by its subdomains. For example, a cookie set for .example.com can be accessed by sub1.example.com and sub2.example.com. The Domain attribute of the cookie is used to specify this scope.

Sharing Cookies Across Domains Using JavaScript

JavaScript itself cannot directly read or set cookies across different domains due to the Same-Origin Policy. However, JavaScript can be used as part of a broader technique to share cookies:

CORS and Backend API: Use Cross-Origin Resource Sharing (CORS) policies combined with server-side APIs to manage cookies across domains.

PostMessage API: Leverage the postMessage API to communicate between iframes or windows from different domains and share cookie data securely.

Conclusion

Handling cookies across domains, origins, and subdomains is complicated due to security and privacy restrictions imposed by browsers. While subdomains benefit from native cookie-sharing capabilities, managing cookies across completely different domains requires more intricate solutions involving backend synchronization, APIs, and leveraging specific JavaScript features. It is crucial to carefully consider these approaches to ensure both functionality and security.