REST API Authentication On Atlassian using Slack as OAuth Provider

Atlassian provides REST APIs to perform a number of operations such as Create Page, Delete Page, Add Comment, Create Space, etc. However, it supports only two authentication methods for REST APIs:
  1. Basic Authentication
  2. Using OAuth 1.0
The REST API Authentication plugin allows you to use any third party OAuth 2.0 provider/ OpenID connect to authenticate REST APIs. Here we will go through a guide to configure Slack as Provider.

Download And Installation

  • Log into your atlassian instance as admin.
  • Navigate to the settings menu and Click Manage Apps.
  • Click Find new apps or Find new add-ons from the left-hand side of the page.
  • Locate Api Token/OAuth Authentication app.
  • Click Try free to begin a new trial or Buy now to purchase a license.
  • Enter your information and click Generate license when redirected to MyAtlassian.
  • Click Apply license.

Step 1: Configure Slack server:

  • Login to Slack : Go to Slack API and login with your account.
  • Go to Channel Settings and click on Add an app option.
 
  • Create an app : Go to the Create App page.
  • Enter App name and Development Slack Workshop. App name can be anything and by default Slack Workshop is Group but you can sign in to another workspace.
  • Click On Create App.
  • Copy Client ID and Client Secret and keep it handy.
 
  • Add Redirect URL : Go to OAuth & Permissions, enter Callback URL(Application’s Base URL.) under Redirect URLs text field and after that click on Save URLs.
 

 

Step 2: Fetch Access token through POSTMAN

  • Open the Postman Application (Here is the link to download Postman Application).
  • Go to Authorization tab.
  • From the dropdown select type as OAuth 2.0 and  click on Get access token.
  • Add the following information from the table below.
  • Postman starts the authentication flow and prompts you to use the access token.
  • Select Send Client Credentials in Body.
Field Value
Grant type Authorization Code or Client Credentials
Callback URL Enter the application's base URL if you dont have a callback URL
Auth URL https://slack.com/oauth/authorize
Access token URL https://slack.com/api/oauth.access
Client ID Enter the Slack Client ID
Client secret Enter the Slack  Client secret
Scope identity.basic
Client Authentication Send Client Credentials in Body
  • Copy the Access Token or click on Use Token.
A sample access token from Slack Provider looks like this.
A834c0606ba71336423013699db8e971

Step 3: Fetch Username through Slack:

  • Choose the method type as "GET".
  • Enter the interoception Endpoint from the plugin to fetch the username in the Request URL. For Slack it is "https://slack.com/api/users.identity?token=".
  • Go to the Authorization tab select the Bearer Token and enter the access token here.
  • Add the header "content-type: application/json" and click on Send.
  Request:
     curl 
     -X GET 
     -H "Authorization: Bearer <Access Token>" 
     -H "Content-type: application/json" 
     https://slack.com/api/users.identity?token=
Copy the attribute value against the username, you will need to configure it in plugin. In this example, the value is "name".  

Configure the Rest API plugin:

Step 1: Enable Rest API Authentication:

  • After installing the app, navigate to the Global Settings tab.
  • Here you will have to Enable the Authentication through Enable REST API Authentication and click on Save.
  • Go to the OAuth/OIDC tab and in the dropdown provided select Slack as the OAuth provider.
  • Enter the attribute value against which we received the username in the Postman response.
  • Save the settings.

Step 2: Disable Basic Authentication:

  • Disabling this will restrict all the REST API call made using Basic Authentication.
 

Test REST API using access token:

  • Call any REST API. Include the access token in the Authorization header. Here’s an example of fetching content from Confluence.
  • Go to the Postman application select method type as GET and enter the Request URL. For eg. http://{Confluence_Base_URL}/confluence/rest/api/content/
  • In the Authorization tab select type as Bearer Token.
Confluence-Rest-API-Keycloak  
  • In the Header tab add the header “content-type: application/json and send the request.
Confluence-Rest-API-Keycloak Request:
     curl 
     -X GET  
     -H "Authorization: Bearer <Access Token>" 
     -H "Content-type: application/json" 
     http://{confluence_base_url}/confluence/rest/api/content/
  • This will show the content in Confluence and will return the status 200.
  • If the token is invalid or missing, the call will return a 401 Unauthorized response



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