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From "Robert Newson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-431) Support cross domain XMLHttpRequest (XHR) calls by implementing Access Control spec
Date Sat, 17 Sep 2011 19:37:09 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-431?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13107222#comment-13107222
] 

Robert Newson commented on COUCHDB-431:
---------------------------------------

Agreed, though I don't see any of those items in the thread so far. However, I'll drop it.

 I'm reading this part of the latest patch;

+set_default_headers(MochiReq) ->
+    case MochiReq:get_header_value("Origin") of
+    undefined -> 
+        erlang:put(cors_headers, []);
+    Origin ->
+        DefaultHeaders = [{"Access-Control-Allow-Origin", Origin},
+                          {"Access-Control-Allow-Credentials", "true"}],
+        erlang:put(cors_headers, DefaultHeaders)
+    end.
+

This does appear to grant access control to any sites that the request asks it to (just include
Origin: foo), that can't be right, can it? My meager understanding of CORS is that the server
should make this determination.

I'm *really* struggling with JIRA right now, it's constantly removing focus when I hit return
or use the shift key. Perhaps there's JS on the page that doesn't work with Chrome 14 but
it's making everything really painful. I'm going to refrain from further comments until I've
thoroughly read the CORS draft, and others should chip in too. I particularly would like Benoit
to correct my understanding of the above function.

> Support cross domain XMLHttpRequest (XHR) calls by implementing Access Control spec
> -----------------------------------------------------------------------------------
>
>                 Key: COUCHDB-431
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-431
>             Project: CouchDB
>          Issue Type: New Feature
>          Components: HTTP Interface
>    Affects Versions: 0.9
>            Reporter: James Burke
>            Assignee: Benoit Chesneau
>            Priority: Minor
>             Fix For: 1.2
>
>         Attachments: 0001-cors-support.-should-fix-COUCHDB-431-2.patch, 0001-cors-support.-should-fix-COUCHDB-431.patch,
0001-cors-support.-should-fix-COUCHDB-431.patch, 0001-cors-support.-should-fix-COUCHDB-431.patch,
0001-cors-support.-should-fix-COUCHDB-431.patch, A_0001-Generalize-computing-the-appropriate-headers-for-any.patch,
A_0002-Send-server-headers-for-externals-responses.patch, A_0003-Usably-correct-w3c-CORS-headers-for-valid-requests.patch,
A_0004-Respond-to-CORS-preflight-checks-HTTP-OPTIONS.patch, cors.html, cors_test.html, test_cors2-1.tgz,
test_cors2.tgz
>
>
> Historically, browsers have been restricted to making XMLHttpRequests (XHRs) to the same
origin (domain) as the web page making the request. However, the latest browsers now support
cross-domain requests by implementing the Access Control spec from the W3C:
> http://dev.w3.org/2006/waf/access-control/
> In order to keep older servers safe that assume browsers only do same-domain requests,
the Access Control spec requires the server to opt-in to allow cross domain requests by the
use of special HTTP headers and supporting some "pre-flight" HTTP calls.
> Why should CouchDB support this: in larger, high traffic site, it is common to serve
the static UI files from a separate, differently scaled server complex than the data access/API
server layer. Also, there are some API services that are meant to be centrally hosted, but
allow API consumers to use the API from different domains. In these cases, the UI in the browser
would need to do cross domain requests to access CouchDB servers that act as the API/data
access server layer.
> JSONP is not enough in these cases since it is limited to GET requests, so no POSTing
or PUTing of documents.
> Some information from Firefox's perspective (functionality available as of Firefox 3.5):
> https://developer.mozilla.org/en/HTTP_access_control
> And information on Safari/Webkit (functionality in latest WebKit and Safari 4):
> http://developer.apple.com/safari/library/documentation/AppleApplications/Conceptual/SafariJSProgTopics/Articles/XHR.html
> IE 8 also uses the Access Control spec, but the requests have to go through their XDomainRequest
object (XDR):
> http://msdn.microsoft.com/en-us/library/cc288060%28VS.85%29.aspx
> and I thought IE8 only allowed GET or POST requests through their XDR.
> But as far as CouchDB is concerned, implementing the Access Control headers should be
enough, and hopefully IE 9 will allow normal xdomain requests via XHR.

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