Connecting to Trello

Trello uses token-based authentication to grant third-party applications access to their API. When a user has granted an application access to their data, the application is given a token that can be used to make requests to Trello's API.

The Trello API can be accessed either via Trello's own Authorization Route, or via OAuth.

Trello Authorization Route

At the moment of registration, Trello assigns an API key and Token to the account.

To activate access via Authorization Route:

1. Set AuthScheme to Token.
2. Retrieve the account's API key:
   • Log into Trello
   • Visit https://trello.com/app-key.
3. Adjust this url: https://trello.com/1/authorize?expiration=never&name=MyPersonalToken&scope=read,write,account&response_type=token&key={Key} changing key to the API key you just obtained.
4. Visit the url.
5. To change the token's expiration time, modify the expiration= field. Legal values are 1hour, 1day, 30days, and never.
6. To authorize the application to use your account, click Allow. Trello redirects you to a page with your token.
7. Set the following connection properties:
   • APIKey = the key found at https://trello.com/app-key.
   • Token = the token you just obtained.

After you have secured both the API key and the Token, you are ready to make requests to the Trello API.

OAuth

Similar to using Authorization, OAuth creates an Application Id and Secret when you create your account. To authenticate via OAuth, from the Web, a Desktop, or a Headless Server, you must set AuthScheme to OAuth, and you must create a custom OAuth application, as described in Creating a Custom OAuth Application.

The following subsections describe how to authenticate to Trello from three common authentication flows:

• Desktop: a connection to a server on the user's local machine, frequently used for testing and prototyping.
• Web: access to data via a shared website.
• Headless Server: a dedicated computer that provides services to other computers and their users, which is configured to operate without a monitor and keyboard.

For information about how to create a custom OAuth application, see Creating a Custom OAuth Application.

For a complete list of connection string properties available in Trello, see Connection.

Desktop Applications

To authenticate with the credentials for a custom OAuth application, you must get and refresh the OAuth access token. After you do that, you are ready to connect.

Get and refresh the OAuth access token:

• InitiateOAuth = GETANDREFRESH. Used to automatically get and refresh the OAuthAccessToken.
• OAuthClientId = the client Id assigned when you registered your application.
• OAuthClientSecret = the client secret that was assigned when you registered your application.
• CallbackURL = the redirect URI that was defined when you registered your application.

When you connect, the adapter opens Trello's OAuth endpoint in your default browser. Log in and grant permissions to the application.

After you grant permissions to the application, the adapter then completes the OAuth process:

1. The adapter obtains an access token from Trello and uses it to request data.
2. The OAuth values are saved in the path specified in OAuthSettingsLocation. These values persist across connections.

When the access token expires, the adapter refreshes it automatically.

Web Applications

Authenticating via the Web requires you to create and register a custom OAuth application with Trello, as described in Creating a Custom OAuth Application. You can then use the adapter to get and manage the OAuth token values.

This section describes how to get the OAuth access token, and how to have the driver refresh the OAuth access token automatically.

Get the OAuth access token:

1. Set the following connection properties to obtain the OAuthAccessToken:
   • OAuthClientId = the client Id in your application settings.
   • OAuthClientSecret = the client secret in your application settings.

2. Call stored procedures to complete the OAuth exchange:
   • Call the GetOAuthAuthorizationURL stored procedure. Set the AuthMode input to WEB and the CallbackURL to the Redirect URI you specified in your application settings. The stored procedure returns the URL to the OAuth endpoint.
   • Navigate to the URL that the stored procedure returned in Step 1. Log in and authorize the web application. You are redirected back to the callback URL.
   • Call the GetOAuthAccessToken stored procedure. Set the AuthMode input to WEB. Set the Verifier input to the code parameter in the query string of the redirect URI.

After you obtain the access and refresh tokens, you can connect to data and refresh the OAuth access token automatically.

Automatic refresh of the OAuth access token:

To have the adapter automatically refresh the OAuth access token, do the following:

1. Before connecting to data for the first time, set the following connection parameters:
   • InitiateOAuth = REFRESH.
   • OAuthClientId = the client Id in your application settings.
   • OAuthClientSecret = the client secret in your application settings.
   • OAuthAccessToken = the access token returned by GetOAuthAccessToken.
   • OAuthSettingsLocation = the path where you want the adapter to save the OAuth values, which persist across connections.
2. On subsequent data connections, set the following:
   • InitiateOAuth
   • OAuthSettingsLocation

Headless Machines

If you need to log in to a resource that resides on a headless machine, you must authenticate on another device that has an internet browser. You can do this in either of the following ways:

• Option 1: Obtain the OAuthVerifier value.
• Option 2: Install the adapter on a machine with an internet browser and transfer the OAuth authentication values after you authenticate through the usual browser-based flow.

After you execute either Option 1 or Option 2, configure the driver to automatically refresh the access token on the headless machine.

Option 1: Obtaining and Exchanging a Verifier Code

To obtain a verifier code, you must authenticate at the OAuth authorization URL. Do the following:

1. Authenticate from the machine with an internet browser, and obtain the OAuthVerifier connection property.

   Set the following properties:

   • InitiateOAuth = OFF.
   • OAuthClientId = the client Id assigned when you registered your application.
   • OAuthClientSecret = the client secret assigned when you registered your application.

2. Call the GetOAuthAuthorizationURL stored procedure. The stored procedure returns the CallbackURL established when the custom OAuth application was registered. (See Creating a Custom OAuth Application.)

   Copy this URL and paste it into a new browser tab.

3. Log in and grant permissions to the adapter. The OAuth application redirects you the redirect URI, with a parameter called code appended. Note the value of this parameter; you will need it later, to configure the OAuthVerifier connection property.

4. Exchange the OAuth verifier code for OAuth refresh and access tokens. On the headless machine, set the following connection properties to obtain the OAuth authentication values:

   • InitiateOAuth = REFRESH.
   • OAuthVerifier = the noted verifier code (the value of the code parameter in the redirect URI).
   • OAuthSettingsLocation = persist the encrypted OAuth authentication values to the specified file.
   • OAuthClientId = the client Id in your custom OAuth application settings.
   • OAuthClientSecret = the client secret in the custom OAuth application settings.

5. Test the connection to generate the OAuth settings file.

6. After you re-set the following properties, you are ready to connect:

   • InitiateOAuth = REFRESH.
   • OAuthSettingsLocation = the file containing the encrypted OAuth authentication values. To enable the automatic refreshing of the access token, be sure that this file gives read and write permissions to the adapter.
   • OAuthClientId = the client Id assigned when you registered your application.
   • OAuthClientSecret = the client secret assigned when you registered your application.

Option 2: Transferring OAuth Settings

Prior to connecting on a headless machine, you must install and create a connection with the driver on a device that supports an internet browser. Set the connection properties as described above in "Desktop Applications".

After completing the instructions in "Desktop Applications", the resulting authentication values are encrypted and written to the path specified by OAuthSettingsLocation. The default filename is OAuthSettings.txt.

Test the connection to generate the OAuth settings file, then copy the OAuth settings file to your headless machine.

To connect to data via the headless machine, set the following connection properties:

• InitiateOAuth = REFRESH
• OAuthSettingsLocation = the path to the OAuth settings file you copied from the machine with the browser. To enable automatic refreshing of the access token, ensure that this file gives read and write permissions to the adapter.
• OAuthClientId = the client Id assigned when you registered your custom OAuth application.
• OAuthClientSecret = the client secret assigned when you registered your custom OAuth application.