OAuth2 authentication

OAuth2 is a protocol that enables us to get access to private details of user's account without getting its password.

Before using the OAuth2 you should create an application in user's account. Each application getting unique App ID and App Secret parameters. You should not share them.

This functianolity is based on doorkeeper gem

Web Application Flow

This flow is using for authentication from third-party web sites and probably is most used. It basically consists of an exchange of an authorization token for an access token. For more detailed info, check out the RFC spec here

This flow consists from 3 steps.

1. Registering the client

Creat an application in user's account profile.

2. Requesting authorization

To request the authorization token, you should visit the /oauth/authorize endpoint. You can do that by visiting manually the URL:

http://localhost:3000/oauth/authorize?client_id=APP_ID&redirect_uri=REDIRECT_URI&response_type=code

Where REDIRECT_URI is the URL in your app where users will be sent after authorization.

3. Requesting the access token

To request the access token, you should use the returned code and exchange it for an access token. To do that you can use any HTTP client. In this case, I used rest-client:

parameters = 'client_id=APP_ID&client_secret=APP_SECRET&code=RETURNED_CODE&grant_type=AUTHORIZATION_CODE&redirect_uri=REDIRECT_URI'
RestClient.post 'http://localhost:3000/oauth/token', parameters

# The response will be
{
 "access_token": "de6780bc506a0446309bd9362820ba8aed28aa506c71eedbe1c5c4f9dd350e54",
 "token_type": "bearer", 
 "expires_in": 7200,
 "refresh_token": "8257e65c97202ed1726cf9571600918f3bffb2544b26e00a61df9897668c33a1"
}

You can now make requests to the API with the access token returned.

Use the access token to access the API

The access token allows you to make requests to the API on a behalf of a user.

GET https://localhost:3000/api/v3/user?access_token=OAUTH-TOKEN

Or you can put the token to the Authorization header:

curl -H "Authorization: Bearer OAUTH-TOKEN" https://localhost:3000/api/v3/user

Resource Owner Password Credentials

In this flow, a token is requested in exchange for the resource owner credentials (username and password). The credentials should only be used when there is a high degree of trust between the resource owner and the client (e.g. the client is part of the device operating system or a highly privileged application), and when other authorization grant types are not available (such as an authorization code).

Even though this grant type requires direct client access to the resource owner credentials, the resource owner credentials are used for a single request and are exchanged for an access token. This grant type can eliminate the need for the client to store the resource owner credentials for future use, by exchanging the credentials with a long-lived access token or refresh token. You can do POST request to /oauth/token with parameters:

{
  "grant_type"    : "password",
  "username"      : "user@example.com",
  "password"      : "sekret"
}

Then, you'll receive the access token back in the response:

{
  "access_token": "1f0af717251950dbd4d73154fdf0a474a5c5119adad999683f5b450c460726aa",
  "token_type": "bearer",
  "expires_in": 7200
}

For testing you can use the oauth2 ruby gem:

client = OAuth2::Client.new('the_client_id', 'the_client_secret', :site => "http://example.com")
access_token = client.password.get_token('user@example.com', 'sekret')
puts access_token.token

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