Accessing the LogicMonitor REST API with Postman and LMv1 API Token Authentication

[Kurt Huffman 0]

Introduction

Postman is widely used for interacting with various REST APIs such as LogicMonitor's. However, there is no out-of-the-box support for the LMv1 authentication method which we recommend as a best practice. This document describes how to configure Postman to use LMv1 authentication when interacting with our REST API.

Overview

Postman's pre-request script functionality provides the ability to generate the necessary Authorization header for LMv1 authentication. As the name suggests, the pre-request script runs immediately before the request is made to the API endpoint. We set the pre-request script at the collection level in Postman so that it will run automatically for every request that is part of the collection.

The script requires three input parameters: a LogicMonitor API token (or ID), its associated key, and the full request URL. These parameters are made available to the script by creating a Postman environment and setting the values as environment variables. If you need to access multiple LogicMonitor accounts (portals), create a separate environment for each to store the applicable API and URL information. Since all API requests to a given account use the same base URL (https://<account>.logicmonitor.com/santaba/rest) it is convenient to store this as an environment variable.

The output of the script is the value of the Authorization header. The script writes the header value to an environment variable which is then inserted as the Authorization header value in the request.

Instructions

1. 1. Download and install Postman.
    
2. 2. Launch Postman and create a new collection that will be used for all LogicMonitor API requests.
    
3. 3. In the create collection dialog, select the "Pre-request Scripts" section and paste in the following code.

// Get API credentials from environment variables
var api_id = pm.environment.get('api_id');
var api_key = pm.environment.get('api_key');
  
 // Get the HTTP method from the request
var http_verb = request.method;
// Extract the resource path from the request URL
var resource_path = request.url.replace(/(^{{url}})([^\?]+)(\?.*)?/, '$2');
// Get the current time in epoch format
var epoch = (new Date()).getTime();

// If the request includes a payload, included it in the request variables
var request_vars = (http_verb == 'GET'||http_verb == 'DELETE') ?
http_verb + epoch + resource_path : http_verb + epoch + request.data + resource_path;
  
 // Generate the signature and build the Auth header
var signature = btoa(CryptoJS.HmacSHA256(request_vars,api_key).toString());
var auth = "LMv1 " + api_id + ":" + signature + ":" + epoch;

// Write the Auth header to the environment variable
pm.environment.set('auth', auth);

 

4. Create a new environment. Create the environment variables shown below. You do not need to provide a value for the "auth" variable since this will be set by the pre-request script. Be sure to use the api_id, api_key, and url values appropriate for your LogicMonitor account.

5. Create a request and add it to the collection with the pre-request script. A sample request is shown below with the necessary parameters configured.

1. 1. 1.      1. Set the environment for the request,
      2.      2. Set the HTTP method for the request.
      3.      3. Use {{url}} to pull the base URL from the environment variable. Add the resource path and any request parameters your API request may require.
      4.      4. Add the Authorization header and set the value to {{auth}} to pull the the value from the environment variable.
      5.      5. POST, PUT, and PATCH requests only: if your request includes JSON data, be sure to select the Body tab and add it.

 

6. Press Send to send the request. The response will appear below the request in Postman.

 

Troubleshooting

You receive the response "HTTP Status 401 - Unauthorized"

Confirm the following:

     • The proper environment has been specified for the request.
     • The necessary environment variables have been set and their values are correct. Note that the script relies on the specific variable names used in this document: "api_id", "api_key", "url", and "auth".
     • The request is a member of the collection configured with the pre-request script.

Postman reports "Could not get any response" or "There was an error in evaluating the Pre-request Script:  TypeError: Cannot read property 'sigBytes' of undefined"

Make sure you have set the proper environment for the request and all necessary environment variables and values are present.

 

 

 

Edited May 25, 2018 by Kurt Huffman
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[Mosh 114]

Very useful, thanks!

[Nicklas Karlsson 1]

Is it possible to use other rest api motors like Restlet client (add in to chrome) and perform a clean request. in Postman You have a pre-request script in your environment for every request. WHy I'm wondering is that I want to Use Power BI to collect data from LM toll gather information from different system to show an central space for all systems we have.

[Kurt Huffman 0]

LMv1 (token-based) authentication relies on a dynamically generated signature in the Authorization header. Current time is one of the inputs for generating the signature which is why the pre-request script must be run for each request.

While we recommend using LMv1 authentication due to its greater security, basic authentication (user-password) is supported for v1 of our API and is easily implemented when dynamic generation of the Authorization header is not possible. You can find more information about authenticating with our API here: Using LogicMonitor's REST API

[Jason Miller 0]

I got this to work with a GET however I get an authorization failed when doing a post, the api user I am using is a full admin

[Kurt Huffman 0]

If GET works but POST does not, there may be something wrong with the request variables in the script. Make sure the code in your script generating the request variables (request_vars) matches the code in the example.

You can add a line to the relevant section of the script to inspect the request variables in the Postman console:

// If the request includes a payload, included it in the request variables
var request_vars = (http_verb == 'GET'||http_verb == 'DELETE') ? 
http_verb + epoch + resource_path : http_verb + epoch + request.data + resource_path;
console.log(request_vars)

After saving the change to the pre-request script, open the Postman console then send the request.

request_vars for a GET request is just GET+timestamp+resource_path like this:

GET1553268441890/device/groups

request_vars for a POST request must include the body data between the timestamp and the resource path and so should look like this:

POST1553267947762{"name":"Postman"}/device/groups

I hope this helps. If not, feel free to share your POST request and I'll be happy to take a look.

[Jason Miller 0]

Ok I am getting "POST1553787894612[object Object]/sdt/sdts"

Here is my script:

// Get API credentials from environment variables
var api_id = pm.environment.get('api_id');
var api_key = pm.environment.get('api_key');
  
 // Get the HTTP method from the request
var http_verb = request.method;
// Extract the resource path from the request URL
var resource_path = request.url.replace(/(^{{url}})([^\?]+)(\?.*)?/, '$2');
// Get the current time in epoch format
var epoch = (new Date()).getTime();

// If the request includes a payload, included it in the request variables
var request_vars = (http_verb == 'GET'||http_verb == 'DELETE') ?
http_verb + epoch + resource_path : http_verb + epoch + request.data + resource_path;
console.log(request_vars)
  
 // Generate the signature and build the Auth header
var signature = btoa(CryptoJS.HmacSHA256(request_vars,api_key).toString());
var auth = "LMv1 " + api_id + ":" + signature + ":" + epoch;

// Write the Auth header to the environment variable
pm.environment.set('auth', auth);

 

Here is the post: {{url}}/sdt/sdts?type=DeviceGroupSDT&deviceGroupFullPath=Test&sdtType=1&startDateTime=1553400000000&endDateTime=1553425200000&dataSourceName=Ping

Edited March 28 by Jason Miller
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[Kurt Huffman 0]

Thanks for sharing. Your pre-request script looks good. But "[object Object]" in the request variables suggests that there is no data in the body of your request. POST requests require some body data, most often in JSON format.

Here is example data for a POST to /sdt/sdts taken from https://www.logicmonitor.com/support/rest-api-developers-guide/v1/sdts/add-sdts/:

{"sdtType":1,"type":"ServiceSDT","serviceId":47,"startDateTime":1469134752000,"endDateTime":1469144995000}

In Postman, it would look like this:

Confirm that your request contains properly formatted JSON data in the body. If it does, and you're still getting this error, I'll be happy to take a closer look.

[Jason Miller 0]

Got it, thanks a bunch