Exploring Apache Knox - part III

This is the third in a series of blog posts exploring some of the security features of Apache Knox. The previous post looked at accessing a file stored in HDFS via Apache Knox, where the Apache Knox gateway authenticated the user using a (JWT) token obtained from the Knox token service. However, the token enforcement in the Knox REST API is not tightly coupled to the Knox token service, a third-party JWT provider can be used instead. In this post, we will show how to authenticate a user to Apache Knox using a token obtained from the Apache CXF Security Token Service (STS).

1) Deploy the Apache CXF STS in docker

Apache CXF ships with a powerful and flexible STS that can issue, renew, validate, cancel tokens of different types via the (SOAP) WS-Trust interface. In addition, it also has a flexible REST interface. I created a sample github project which builds the CXF STS with the REST interface enabled:

• sts-rest: Project to deploy a CXF REST STS web application in docker

The STS is configured to authenticate users via HTTP Basic authentication, and it can issue both JWT and SAML tokens. Clone the project, and then build and deploy the project in docker using Apache Tomcat as follows:

• mvn clean install
• docker build -t coheigea/cxf-sts-rest .
• docker run -p 8080:8080 coheigea/cxf-sts-rest

To test it's working correctly, open a browser and obtain a SAML and JWT token respectively via the following GET requests (authenticating using "alice" and "security"):

• http://localhost:8080/cxf-sts-rest/SecurityTokenService/token/saml
• http://localhost:8080/cxf-sts-rest/SecurityTokenService/token/jwt

2) Invoking on the REST API of Apache Knox using a token issued by the STS

Now we'll look at how to modify the previous tutorial so that the REST API is secured by a token issued by the Apache CXF STS, instead of the Knox token service. To start with, follow the first tutorial to set up Apache Knox as well as the backend Apache Hadoop cluster we are trying to obtain a file from. Then follow part (2) of the previous tutorial to set up the "sandbox-token" topology. Now copy "conf/topologies/sandbox-token.xml" to "conf/topologies/sandbox-token-cxf.xml". We need to make a few changes to the "JWTProvider" to support validating tokens issued by the CXF STS.

Edit "conf/topologies/sandbox-token.xml" and add the following parameters to the "JWTProvider", i.e.:
"knox.token.verification.pem" is the PEM encoding of the certificate to be used to verify the signature on the received token. You can obtain this in the sts-rest project in github here, simply paste in the content between the "-----BEGIN/END CERTIFICATE-----" into the parameter vaue. "jwt.expected.issuer" is a constraint on the "iss" claim of the token.

Now save the topology file and we can get a token from CXF STS using curl as follows:

• curl -u alice:security -H "Accept: text/plain" http://localhost:8080/cxf-sts-rest/SecurityTokenService/token/jwt

Save the (raw) token that is returned. Then invoke on the REST API using the token as follows:

• curl -kL -H "Authorization: Bearer <access token>" https://localhost:8443/gateway/sandbox-token-cxf/webhdfs/v1/data/LICENSE.txt?op=OPEN