About a week ago a colleague asked me to help resurrect some code I had written to use our work ID badges to look up information on the card owner in order to log into a system for a demonstration.
The ID badges are basically mifare cards so can be read by a NFC reader. The content of the cards is encrypted, but each card has a unique ID. Unfortunately the security team will not share the mapping of these IDs to actual people, but since this is for a demonstration that will only be given by a relatively small number of people it’s not a problem to set up a list of mappings our selves.
The original version of this code used nfc-eventd and some java code to the IDs then do a lookup in a little database to convert these to email addresses. It worked but was a bit of a pig to setup and move between machines as it required a number of different apps and config files so I decided to have a go at rewriting it all in Node-RED.
To do this I was going to need 2 new nodes, one to read the NFC card and one to look up details in the LDAP. Both of these actually proved reasonable easy and quick to write as there are existing Node NPM modules that do most of the heavy lifting. The flow has a couple of extra bit, it uses a mongodb to store the id to email address mappings and if there is no match it uses websockets to populate a field in a separate web page to enter a email address to update the database.
I did a first pass using the nfc npm and it worked but there was no way to shut the connection to the NFC reader down in the code which meant I couldn’t clean up properly when Node-RED shut down or when the node needed to be restarted.
The nfc on npmjs.org is actually a bit out of date compared to the git repository it’s hosted in. So I moved over to using the upstream version of the code. This changed the API a little and still didn’t have a mechanism to allow the interface to be stopped. I forked the project and after a little bit of playing I ended up with some working shutdown code.
The only call back is for when at NFC tag is detected and it polls in tight loop so the stream of data from the node is way too high to feed into a Node-RED flow really. The Node-RED wrapper rate limits to only reporting the same tag once every 10 seconds. This is good enough for the original problem I was looking to solve but I still think it can be done better. I’m planning on adding call backs for tag seen and when it is removed, this is similar to how nfc-eventd works. I also want to look at doing NDEF decoding.
You can install the current version of the node with:
npm install https://github.com/hardillb/node-red-contrib-nfc/archive/master.tar.gz
It depends on libnfc which should work on the Linux and OSx and I’ve even seen instructions to build it for Windows.
Once I’ve got a bit further I’ll add it to npmjs.org.
It just needed a config dialog creating to take a base DN and a filter and a connection setup that takes a server, port and if needed a bind DN and password. The filter is a mustache template so values can be passed in.
This node is pretty much done, you can find the code on github here and the node can be installed with the following:
npm install node-red-node-ldap
Like the NFC node openldap should be available for Linux and OSx and there looks to be a Windows port