For the RDA, the catalogs themselves do not require authentication. However, any service or html/xml page used by a service (like dataset.xml for NCSS) will require authentication.

When you make a request to the server and the resource requires authentication, it will respond with a

HTTP 401 Unauthorized

and, included in those headers, will be something like:

WWW-Authenticate: Basic

For example:

curl -i "https://rda.ucar.edu/thredds/dodsC/files/g/ds084.1/2015/20150116/gfs.0p25.2015011600.f006.grib2.ascii?LatLon_Projection"
HTTP/1.1 401 Unauthorized
Date: Mon, 31 Jul 2017 13:45:40 GMT
Server: Apache/2.4.6 (CentOS)
Strict-Transport-Security: max-age=63072000; includeSubdomains; preload
Cache-Control: private
Expires: Wed, 31 Dec 1969 17:00:00 MST
WWW-Authenticate: Basic realm="THREDDS Data Server"
Content-Language: en
Content-Length: 994
Content-Type: text/html;charset=utf-8

So, if you get a 401, you check the WWW-Authenticate part of the header to see what type of authorization is required. Common possibilities include Basic, Digest, and OAuth, although there are others.

Once you get the 401, it's up to the client to decide what to do. In toolsUI, a log-in gui widget will appear:

but there are any number of ways of doing things (e.g. command line prompt, let user set credentials as part of Siphon API).

Now, where this gets a little tricky is when Siphon piggybacks on another library for access, like how we use netCDF4-Python to speak OPeNDAP (which then relies on netCDF-C). The C library does this for auth. Pretty gnarly, but we might be able to get away with detecting the case of a 401 trying to access an OPeNDAP resource, and insert the credentials into the DAP URL (case 2 in the previously linked netCDF-C doc on authentication). However, if the group running the OPeNDAP enabled server has their own authentication service and it involves a redirect (like NASA URS), then things really get fun (see section 4 of the netCDF-C doc), but thankfully NASA has some docs to help guide us for that.

Basic authentication #117

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mangecoeuropenedon Dec 16, 2016

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mangecoeur
openedon Dec 16, 2016