A basic CorDapp to demonstrate how you can integrate access control lists into your CorDapps.

There are three Corda nodes in this demo; PartyA, PartyB and PartyC. There is also a web server which acts as the business network operator. In this scenario, the business network operator does not operate a Corda node. Instead, it serves an access control list via an API end-point.

The business network operator can load in to memory a file containing an access control. This list will then be served via the API end-point. The list is simply a list of serialised CordaX500 names delineated by new lines. New names can be added via the console. Names can also be deleted via the console. Any changes to the list will be reflected in the list which the API end-point serves.

In this scenario, via the flow framework, the three nodes have the capability to send each other "pings" and reply with "pongs". The three nodes in this scenario operate a CordaService which polls the business network operator's API end-point on a fixed interval. Each time the access control list is downloaded, the node's cache is updated with the new access control list. Before any of the nodes can start a flow to sender "ping", the access control list is checked to see if the recipient is on the list.

The server module implements a simple API end-point which serves the "acl.txt" file. The file is read every time a request is sent to the /acl end-point. Additional lines can be added to the "acl.txt" file while the server is running. Care must be taken to ensure that the CordaX500Names in the "acl.txt" file are well formed. If are not well formed then the web server will return a 500 Internal Error.

The client works by polling the /acl end-point every second and then updating a whitelist held within a CordaService. Both the PingFlow and the PongFlow checks to see whether counter-parties are on the white-list.

Start the server and the clients. You must start the server before the client Corda nodes:

./gradlew clean deployNodes
./gradlew runServer
cd build/nodes
./runnodes

The access control list can be seen at http://localhost:8000/acl. Only PartyA is on the whitelist initially. When all the nodes have started then try to send a ping from PartyA to PartyB:

start PingFlow target: PartyB

It should fail as PartyB is not on the white list:

🚫   Done
☠   O=PartyB, L=New York, C=US is not on the whitelist.

Now, add PartyB to the whitelist by opening "acl.txt" in the project root and adding O=PartyB, L=New York, C=US to the file on a new line. Then, send another ping to PartyB:

start PingFlow target: PartyB

The flow should successfully complete:

Sending PING to O=PartyB, L=New York, C=US
Received PONG from O=PartyB, L=New York, C=US

✅   Done

That's it!