How to uniquely identify user logging in via oauth? - oauth

Question

I particular - I don't understand how to link user that authenticated using oauth to a particular account in my application?
So here's accounts in my applciation:
CREATE TABLE accounts (
id BIGINT NOT NULL AUTO_INCREMENT,
username VARCHAR(40),
email VARCHAR(256),
created DATETIME,
updated DATETIME,
PRIMARY KEY (id),
UNIQUE KEY (email),
UNIQUE KEY (username)
) ENGINE=InnoDB CHARACTER SET utf8 COLLATE utf8_general_ci;
With openid for example there is a unique user id (uri, xri) which uniquely identifies that user. So I can just link to my accounts like this:
CREATE TABLE openid_logins (
id BIGINT NOT NULL auto_increment,
fk_accounts_id BIGINT NOT NULL,
openid_identity TEXT NOT NULL, /*that's unique user id*/
openid_provider_url VARCHAR(255) NOT NULL, /*flickr, yahoo, live_journal*/
PRIMARY KEY (id),
INDEX (openid_identity),
FOREIGN KEY (fk_accounts_id) REFERENCES accounts(id) ON UPDATE CASCADE ON DELETE CASCADE
);
So Whenever user logs in via openid -> I can get his regular account referencing fk_accounts_id.
But when it comes to oauth - AFAIK there is no such things as oauth_identity_string... And since oauth tokens might change tokens by themselves cannot be used as a unique link to profile in my applicaiton..... So what should I do? How to uniquely identify a user logging in via oauth?

Answer 1

You can't get information about the user by the OAuth protocol itself, however, there is normally an endpoint, to which you can make a request, that provides user information. For example Google provides one: after you receive your token, you can make a request to:
GET https://www.googleapis.com/plus/v1/people/me?access_token={TOKEN}
This will return a JSON object containing information about the user, including an unique identifier.

Answer 2

Get the account_id using the apis and store it in the following format:
-- --------------------------------------------------------
--
-- Table structure for table oauth -- its like a username passwd thingy
--
CREATE TABLE IF NOT EXISTS oauth (
oauth_id bigint unsigned NOT NULL AUTO_INCREMENT UNIQUE,
service varchar(16) NOT NULL,
account_id varchar(256) NOT NULL,
token text NOT NULL,
token_secret text NOT NULL,
PRIMARY KEY (service, account_id)
) ENGINE=InnoDB DEFAULT CHARSET=ascii COLLATE=ascii_bin;
service can be a google, twitter, etc if you are using multiple oauth