OAuth2-protected REST APIs usage
Content:
Requesting an OAuth2 token
Before using any REST API protected by OAuth2, you must request a token to the Cosmos Tokens Generator you muat have installed somewhere. This is a service that will be listening in TCP/13000 port (in FIWARE Lab, this is cosmos.lab.fiware.org:13000. You can do this using any REST client of your choice, the easiest way is using the curl command:
$ curl -k -X POST "https://<tokens_generator_host>:13000/cosmos-auth/v1/token" -H "Content-Type: application/x-www-form-urlencoded" -d "grant_type=password&username=<registered_email_in_imd>&password=<password_in_idm>"
{"access_token": "qjHPUcnW6leYAqr3Xw34DWLQlja0Ix", "token_type": "Bearer", "expires_in": 3600, "refresh_token": "V2Wlk7aFCnElKlW9BOmRzGhBtqgR2z"}
As you can see, some Identity Manager credentials are required in the payload, in the form of a password-based grant type. This is because the Cosmos Tokens Generator relies on an Identiy Manager instance.
Using the token with WebHDFS
Once the access token is got (in the example above, it is qjHPUcnW6leYAqr3Xw34DWLQlja0Ix), simply add it to the original WebHDFS request by using the `X-Auth-Token` header:
$ curl -X GET "http://<namenode_or_httpfs_host>:<50070_or_14000>/webhdfs/v1/user/<your_cosmos_username>/path/to/the/data?op=liststatus&user.name=<your_cosmos_username>" -H "X-Auth-Token: qjHPUcnW6leYAqr3Xw34DWLQlja0Ix"
{"FileStatuses":{"FileStatus":[...]}}
If you try the above request with a random token the server will return the token is not valid; that's because you have not authenticated properly:
$ curl -X GET "http://<namenode_or_httpfs_host>:<50070_or_14000>/webhdfs/v1/user/<your_cosmos_username>/path/to/the/data?op=liststatus&user.name=<your_cosmos_username>" -H "X-Auth-Token: randomtoken93487345"
User token not authorized
The same way, if using a valid token but trying to access another HDFS userspace, you will get the same answer; that's because you are not authorized to access any HDFS userspace but the one owned by you:
$ curl -X GET "http://<namenode_or_httpfs_host>:<50070_or_14000>/webhdfs/v1/user/<other_cosmos_username>/path/to/the/data?op=liststatus&user.name=<other_cosmos_username>" -H "X-Auth-Token: qjHPUcnW6leYAqr3Xw34DWLQlja0Ix"
User token not authorized