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I've created a maven project to create a CORS enable thredds war: https://github.com/tkunicki-usgs/thredds-cors CORS is useful for working around single origin issues in browser apps. A CORS enabled server essentially tells the browser that it's ok to let code loaded from a different server utilize resources from the CORS enabled server. Tom Kunicki Center for Integrated Data Analytics U.S. Geological Survey 8505 Research Way Middleton, WI 53562 On Apr 24, 2013, at 2:11 PM, Dennis Heimbigner <dmh@xxxxxxxxxxxxxxxx> wrote: > Perhaps more concretely, the thredds server > currently supports access controls such as > passwords and client-side keys. How would > CORS affect those? > > =Dennis Heimbigner > Unidata > > Roberto De Almeida wrote: >> Hi, guys! >> In 2006 I wrote an implementation of an OPeNDAP client in Javascript called >> jsdap (https://code.google.com/p/jsdap/). At the time Javascript was still >> a toy language and the XML HTTP Request (XHR) was unable of handling binary >> data, but I managed to hack a full client that worked in all major browsers >> (including IE by injecting vbscript!). And while it was written more as a >> proof-of-concept the client is actually used in some data portals like >> http://www.ifremer.fr/oceanotronPortal/. (A Node.js OPeNDAP server was also >> added 3 years ago.) >> Fast forward 7 years and we now have a lot of new technologies on the >> table: a new XHR object with support for binary transfers, typed arrays and >> WebGL. I've been playing again with using Javascript as an OPeNDAP client, >> in particular to display real time information from OPeNDAP servers. I have >> set up a small OPeNDAP server on one of my VPS streaming the system load >> information: >> http://vps.dealmeida.net:5000/.dds >> http://vps.dealmeida.net:5000/.das >> This is an infinite dataset (try "curl http://vps.dealmeida.net:5000/.asc";), >> and it will keep streaming the data at one record per second until the >> connection is broken. Keep in mind that this is a regular OPeNDAP Sequence, >> and nothing was changed in the specification to make this work. >> Nevertheless, I'm not aware of OPeNDAP clients that can access the stream >> other than the development version of Pydap. >> On another machine I have a widget displaying the information on a real >> time graph: http://dealmeida.net/opendap-streaming/ >> You can see how everything was implemented on this Mercurial >> repository<http://code.dealmeida.net/opendap-streaming/src/356dde80f6e55603c2ab7e581244015663504fda?at=demo>. >> The >> data is displayed by fetching the .dods response and parsing it. We still >> need a few hacks to do this, but only because the data is being streamed >> (Mozilla handles it nice; Chrome cannot stream binary data, so it still >> fetches it as string). Handling regular OPeNDAP datasets should be pretty >> straightforward with the new XHR, and I plan to rewrite jsdap as soon as I >> have some free time. >> *Now to my request:* the only reason that the demo works -- having a page >> in one host displaying data from an OPeNDAP server on another -- is because >> I >> enabled<http://code.dealmeida.net/pydap/commits/4c2d38b5822ba8f5f61e83bcb23230a2ca7e5da1> >> CORS <http://en.wikipedia.org/wiki/Cross-origin_resource_sharing> on Pydap. >> By default, now all DODS, DAS and DDS responses from Pydap have the >> following additional headers: >> Access-Control-Allow-Origin: * >> Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type >> These headers (the first one, actually) allow the responses to be accessed >> through XHR from any host. As far as I know there is no downside in doing >> this. Even if your server use cookies for authenticating access to certain >> datasets the cookies *will not* be sent unless >> the Access-Control-Allow-Credentials header is set (and set to true), which >> would allow other sites to "steal" your data and download it by >> impersonating a logged user. >> My request is that all OPeNDAP servers enable CORS from any host by default >> today, at least in the DODS, DAS and DDS responses; and if not by default, >> at least as an option. This way, by the time Javascript matures enough so >> that its performance on the browser becomes comparable to desktop >> applications we can start building rich web applications that use all the >> data available through OPeNDAP. >> Some resources >> About CORS: http://en.wikipedia.org/wiki/Cross-origin_resource_sharing / >> https://developer.mozilla.org/en-US/docs/HTTP/Access_control_CORS >> Security concerns: >> https://code.google.com/p/html5security/wiki/CrossOriginRequestSecurity >> Thank you, >> Rob > > _______________________________________________ > thredds mailing list > thredds@xxxxxxxxxxxxxxxx > For list information or to unsubscribe, visit: > http://www.unidata.ucar.edu/mailing_lists/
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