This article provides information regarding integration with OAuth v1 applications.
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Starting the OAuth Flow

The GET /oauth1 endpoint performs the initial setup for OAuth version 1 accounts. Included with the request is a single query argument, callback_uri, which is the redirect URL that the user should be expected to be redirected to upon successful authentication with the third-party service. Return body should at least include a redirect_uri that the user should be forwarded to in order to complete setup. Replies are then POST’ed to this endpoint (see below).

// GET /oauth1
{
    "redirect_uri": "https://trello.com/1/OAuthAuthorizeToken?oauth_token=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx&name=TrelloIntegration"
}

Note: The OAuth implementation requires the account identifier to be oauth for OAuth version 1.

Finalizing accounts after user authorization

The POST /oauth1 endpoint performs the final setup and validation of OAuth version 1 accounts. Information as received from the third party upon redirection to the previously posted callback_uri are sent to this endpoint, with other applicable account information, for final setup. The account is then validated and, if successful, the account is returned; if there is an error, it is to be raised appropriately.

Tags: api_spec oauth