The Geeky Gordo

Using AWS Lambda To Relay Jamf Pro Webhooks to Slack

I recently got interested in utilizing webhooks in Jamf Pro but had no idea where to start. I went and watched Bryson Tyrrell’s (https://twitter.com/bryson3gps) presentation from JNUC 2017 Webhooks Part Deaux! and then went over to take a peek at Jackalope on the Jamf Marketplace. I read the docs, I tried to figure out how to do this in AWS ElasticBeanstalk, but I just couldn’t get it going. Just too much going on to devote enough time to it. So, I went over to Zapier and signed up for their free account so I could get this going. I got it working, but I quickly got throttled because I decided to enable the “ComputerCheckIn” webhook to make sure it worked. I think we flooded the 100 connection limit within 30 seconds and wound up having thousands of items in Zapier.

Well, that wasn’t going to work, so I changed it to “ComputerAdded” and waited for my month of Zapier to renew so I’d get 100 new “zaps”. That worked, until we went over the 100 limit again and had to wait. There had to be a better way that wasn’t going to cost me a ton of money. So I went Googling and came across an article on how to use AWS Lambda to do what I wanted to do: AWS Lambda For Forwarding Webhook To Slack.

I walked through the steps outlined on the page to setup the function in Lambda and everything worked great until I got to the part where I was making requests out to Slack. Lambda had a problem with the request method. Specifically this line of code:

 var post_req = https.request(post_options, function(res) {

So another round of Googling and I came up with the Node.js docs page on HTTPS and I figured out how to properly make the call:

const req = https.request(post_options,
	(res) => res.on("data", () => callback(null, "OK")))
	req.on("error", (error) => callback(JSON.stringify(error)));
	req.write(post_data);
	req.end(); 

Once I was able to get past the https connection issues, I was able to utilize the rest of Patrick’s example to get my webhook from Jamf feeding into a Slack channel. We uploaded a custom emoji to our Slack channel and used the Slack documentation on basic message formatting and on attachments to get the notification to look how we wanted.

Ultimately we created two Lambda functions, one for ComputerAdded and another for ComputerInventoryComplete, each feeding into their own channel in our Slack. This was fairly easy to accomplish, the next step is to find a way to feed DataDog, or some other service, the ComputerCheckIn webhook so I can get a count of how many check-ins we have each day.

The code we used is below, but I wanted to point out one or two things. Where I got hung up the most was how to pull things like Computer Name or Serial Number from the JSON we were getting from the Jamf Pro server. Since the JSON contains two arrays, “webhook” and “event”, it took me a little bit to understand how to grab that data. To be honest, my skills here are lacking considerably so it took me longer than it should. Ultimately I figured out that you just have to dot walk to get the data you want. So to get the Computer Name it’s:

body.event.deviceName

“body” is the JSON object that we parse the webhook into. Once I figured that out I was all set to grab whatever data from the event, or webhook, array that I needed. Hopefully my head banging will help others not stumble quite so much.

Here’s the Node.js code we used as the template:

var https = require('https');

exports.handler = (event, context, callback) => {
    
    console.log("MYLOG" + JSON.stringify(event))
    
	var body = JSON.parse(event.body);
	var name = body.event.deviceName;
	var sernum = body.event.serialNumber;
	var user_name = body.event.username;
	var building = body.event.building;
	var curr_time = Math.floor(new Date() / 1000);


    var post_data = JSON.stringify({
		"username": "Jamf Pro Server",
		"icon_emoji": ":balloon:",
		"channel": "#<yourslackchannelname>",
		"text": "Computer Enrolled",
        "attachments": [
	        {
            "color": "good",
            "fields": [
                {
                "title": "Computer: " + name,
				"value": "Serial number: " + sernum
					+ "\nUser name: " + user_name
					+ "\nBuilding: " + building,
                "short": false
                }
            ],
            "footer": "Jamf Webhook",
            "footer_icon": ":balloon:",
            "ts": curr_time
	        }
        ]
	});
  
    var post_options = {
      host: 'hooks.slack.com',
      port: '443',
      path: '/services/YOURWEBHOOK',
      method: 'POST',
      headers: {
          'Content-Type': 'application/json',
          'Content-Length': Buffer.byteLength(post_data)
      }
    };
    
	const req = https.request(post_options,
	  (res) => res.on("data", () => callback(null, "OK")))
	  req.on("error", (error) => callback(JSON.stringify(error)));
	  req.write(post_data);
	  req.end();
     
    var details = {
        "status": "OK"
    }
    
    var response = {
        'statusCode': 200,
        'headers': { 'Content-Type': 'application/json' },
        'body': JSON.stringify(details)
    }
    console.log("LOG:: " + JSON.stringify(response))
    
    callback(null, response);
};

 

 

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