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https://issues.apache.org/jira/browse/COUCHDB-431?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13042512#comment-13042512
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Alex Chaffee commented on COUCHDB-431:
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Sorry for using unclear language -- you're absolutely right, I'm talking about
adding headers per *service* (i.e. host-and-port), not per *database* in
Couchese.
You're also quite right about the danger of '*' -- I used it as shorthand but
it would be more sensible to use the real domain name of your host -- which
would actually take care of the attack vector you mentioned.
I'm confused about your "dynamically generated header" paragraph. The CORS
header must match the domain name(s) of the valid web site(s), which seems
pretty static to me. Or are you just saying again that you'd like the header to
vary per database? Note that a single Access-Control-Allow-Origin header can
contain multiple hostnames (if I read the spec at http://www.w3.org/TR/cors
correctly) so you could serve two sites from the same service with
"Access-Control-Allow-Origin: site1.com site2.com". (Assuming the browsers
implement the spec correctly, of course! :-))
Here's my use case: I want to write an app that goes directly from JavaScript
in a web browser to a CouchDB service running on localhost (and eventually, on
an optional public server). It seems like a perfect fit and it's frustrating
that it doesn't work, especially since it's just for lack of a single HTTP
header. I'm currently building a simple Ruby HTTP server to sit between the
browser and Couch, but there's really no reason for that third tier.
Got any ideas on how to smuggle in a response header without your ACL patch?
> 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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