Origin HTTP header not set to null after following cross-origin redirect

• Component: Page Loading
• Status: RESOLVED DUPLICATE

[Brad Hill]

The HTTP Origin header, described by https://tools.ietf.org/html/rfc6454, allows a server to determine a user agent's view of where a request originated from.

RFC6454 allows this header to be multi-valued on redirects, but CORS (http://w3.org/TR/cors) implicitly requires it to be single-valued (because it specifies an exact string match comparison).
All major user agents implement single-valued behavior, and because of this must set the header to 'null' when a redirect crosses same-origin boundaries.  If the value of the original Origin is preserved after a 3xx redirect, it may result in a confused deputy vulnerability that allows bypass of CSRF protections.

For example, the issue described at the following post is enabled by this incorrect behavior:

http://sakurity.com/blog/2015/03/05/RECONNECT.html

Test cases are available at the following URLs:

https://www.webappsec-test.info/~bhill2/OriginRedir/test.php?redircode=302
https://www.webappsec-test.info/~bhill2/OriginRedir/test.php?redircode=303
https://www.webappsec-test.info/~bhill2/OriginRedir/test.php?redircode=307
https://www.webappsec-test.info/~bhill2/OriginRedir/test.php?redircode=308

WebKit is vulnerable by not setting Origin to null on cross-origin redirects on any 3xx status code which preserves the GET/POST payload.

A similar issue was reported to Blink for status code 308, and has since been patched, see:

https://code.google.com/p/chromium/issues/detail?id=465517

[Radar WebKit Bug Importer]

<rdar://problem/20893169>

[Alexey Proskuryakov]

*** This bug has been marked as a duplicate of bug 144157 ***