sameorigin

Sameorigin is a term used in web security to describe policy directives that restrict certain operations to the same origin. An origin is defined by the combination of the URL’s scheme, host, and port. The concept is most often encountered in the context of protecting a page from being embedded or accessed by other origins.

The same-origin policy is a core browser security mechanism. It prevents scripts loaded from one origin from reading or manipulating resources from a different origin, helping to limit cross-origin data leakage and a range of attacks. Sameorigin-related directives implement practical restrictions for specific interactions, such as framing or script access, to reduce exposure to cross-origin risks.

One common usage is the HTTP header X-Frame-Options with the value SAMEORIGIN. This directive instructs browsers to allow the page to be displayed in a frame only if the framing page shares the same origin. It is a widely supported, though older, method for mitigating clickjacking. The sameorigin concept is also reflected in modern Content Security Policy (CSP) through the frame-ancestors directive, where frame-ancestors 'self' serves a similar purpose.

In CSP terms, 'self' indicates resources or frames from the same origin are allowed, while other origins can be explicitly disallowed or permitted with specific directives. The use of SAMEORIGIN or frame-ancestors 'self' helps prevent others from embedding the content in potentially harmful contexts.

Limitations exist: sameorigin protections primarily address framing and direct cross-origin scripting access, but they do not replace CORS for cross-origin resource sharing or address all cross-origin risks. They are part of a layered approach to web security and should be used in conjunction with other protections.