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https://issues.apache.org/jira/browse/COUCHDB-431?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13041182#comment-13041182
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Alex Chaffee commented on COUCHDB-431:
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I just encountered this issue myself, and I haven't thought through all the
implications, but isn't there an easier way to crack this nut? If we add a
"response_headers" config setting to the normal database httpd config, and the
server adds those headers to every HTTP response, then that's it. Admins can
then implement a coarse form of CORS on a per-database level with a simple
"{response_headers: {'Access-Control-Allow-Origin': '*'}}".
If more fine-grained control is needed (e.g. allow CORS for some client IP#s
but not others) then a patch like Jason's would be needed. But ACL systems are
notoriously difficult to design and implement. My solution leaves access
control up to the local admin, and also makes it clear just how simple CORS
actually is -- it's not hard security, just a message from the server that
tells the client "here's the data, and here's a hint about how I think you
should use it" (which hint is ignored by everybody except web browsers).
(cf. Mozilla: "The Cross-Origin Resource Sharing standard works by adding new
HTTP headers that allow servers to describe the set of origins that are
permitted to read that information using a web browser. Firefox supports these
headers and enforces the restrictions they establish."
https://developer.mozilla.org/en/http_access_control )
Thoughts?
> 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: Randall Leeds
> Priority: Minor
> Attachments:
> 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
>
>
> 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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