The browser is in charge of setting the 'Origin' header and this would never be set to 'localhost' unless your browser is talking to the local machine. But you are right about the spoofing part in that malicious code outside the browser could technically set the origin to anything it wants. The purpose of the JavaScript origin is to allow access control via CORS <https://en.wikipedia.org/wiki/Cross-origin_resource_sharing> which is the method of safely allowing cross-origin requests as related to the same-origin policy <https://en.wikipedia.org/wiki/Cross-origin_resource_sharing>, but it is ultimately up to the browser to enforce this. There's a good answer about how 'CORS is not security <http://stackoverflow.com/questions/21058183/whats-to-stop-malicious-code-from-spoofing-the-origin-header-to-exploit-cors>' on Stack Overflow.
JavaScript does present the problem that the Client ID can be accessed in code but does make it more difficult for an attacker to use when combined with the allowed JavaScript origins above. There's another good question on Stack Overflow which discusses this here <http://stackoverflow.com/questions/24724238/how-do-client-side-js-libraries-for-oauth2-maintain-secure-authentication> . So yes, outside of the browser the security model is not infallible in the case of OAuth with pure JavaScript. On Friday, January 29, 2016 at 11:16:11 AM UTC-5, Ben Finkel wrote: > > When you create a Google API credential for a web app, you indicate > allowed Javascript Origins which is just a list of URIs. I'm trying to > understand what the purpose of these is. > > Does this restriction mean any code using my Client ID to access Public > Google APIs must originate from those sources? That doesn't seem helpful > for two reasons: > > 1) The first thing I do is add "http://localhost:8080"; so I can run code > from my development environment but of course every computer self > identifies as "localhost" so I've effectively negated any security from it. > > 1. > > 2) The Client ID is public knowledge (It's in my JS files which are > delivered to client devices) and spoofing the origin would be trivial for > a > malicious actor. > 2. > > Is it just meant as a small hurdle for malicious code to get around > and nothing more? > > Thanks in advance! > -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/5f3c95f3-986a-4aca-9a9a-036c61364ffe%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
