Oauth2 авторизация

<?php
 
class Oauth2
{
    private $data = false;
    private $tracing = '';
 
    # https://hueniverse.com/oauth-2-0-and-the-road-to-hell-8eec45921529
    # https://habr.com/post/150756/
    static function run($via) {
        global $sky;
 
        $me = new Oauth2($via);
        if (is_object($me->data))
            $sky->log('oauth', print_r($me->data, 1));
        return $me->data;
    }
 
    function __construct($via) {
        global $sky, $user;
        method_exists($this, $provider = "cfg_$via") && !$user->auth or die;
 
        $this->$provider(); # set configuration
        $redirect_uri = urlencode("http://coresky.net/auth?via=$via");
        # step 0
        if (!isset($_GET['code'])) {
            $tpl = 'client_id=%s&redirect_uri=%s&state=%s&scope=%s';
            $dialog = $this->p0 . sprintf($tpl, $this->app_id, $redirect_uri, $user->v_oauth2 = strand(), $this->scope);
            $sky->log('oauth', "\nDIALOG: $dialog\n");
            jump($dialog);
        }
        if (!$user->v_oauth2 || $_GET['state'] != $user->v_oauth2)
            return $this->error("$via: CSRF protection |$_GET[state]|, vid=$user->vid", true); # fatal
        $user->v_oauth2 = null; # erase, do not required anymore
        # step 1
        $tpl = 'client_id=%s&redirect_uri=%s&client_secret=%s&code=%s';
        $auth = unjson($this->cep($this->p1, sprintf($tpl, $this->app_id, $redirect_uri, $this->secret, $_GET['code'] . $this->fields)));
        if (!isset($auth->access_token))
            return $this->error("$via: no token");
        # step 2
        $obj = unjson($this->cep($this->p2 . $auth->access_token)); # GET only
        if (!isset($obj->email) || $this->verify && @!$obj->{$this->verify})
            return $this->error("$via: email error");
        $obj->avatar = $this->$provider($obj);
        $this->data = $obj;
    }
 
    private function error($desc, $is_fatal = false) {
        global $sky;
 
        trace($err = "Oauth2 $desc", true);
        $sky->log('oauth', "\n$err\n$this->tracing\n");
        if ($is_fatal) # auto-ban may used
            throw new Error($err);
    }
 
    # call the end point
    private function cep($url, $qs = '') {
        if ($post = $this->is_post && $qs) {
            $this->tracing .= "\nURL: $url\nPOSTFIELDS:$qs";
        } else { # get
            $this->tracing .= "\nURL: " . ($url .= $qs); # just append QS
        }
        $curl = curl_init($url);
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);
        curl_setopt($curl, CURLOPT_SSL_VERIFYHOST, false);
        if ($post) {
            curl_setopt($curl, CURLOPT_POST, true);
            curl_setopt($curl, CURLOPT_POSTFIELDS, $qs);
        }
        $out = curl_exec($curl);
        if (curl_errno($curl))
            trace(curl_error($curl), true);
        curl_close($curl);
        $this->tracing .= "\nRESULT: $out";
        return $out;
    }
 
    # see https://developers.facebook.com/tools/debug/accesstoken
    # https://developers.facebook.com/docs/facebook-login/manually-build-a-login-flow
    function cfg_facebook($obj = false) {
        if ($obj) # set avatar, no ssl !
            return "http://graph.facebook.com/$obj->id/picture";
        $this->app_id = '{APP_ID}';
        $this->secret = '{APP_SECRET}';
        $this->scope = 'email,user_location,user_link,user_hometown,user_gender,user_birthday,user_age_range';
        $this->p0 = 'https://www.facebook.com/v3.1/dialog/oauth?';
        if (isset($_GET['force']))
            $this->p0 .= 'auth_type=rerequest&';
        $graph = 'https://graph.facebook.com';
        $this->p1 = "$graph/v3.1/oauth/access_token?";
        $this->is_post = false;
        $this->fields = '';
        $this->p2 = "$graph/me?fields=email,name,verified&access_token=";
        $this->verify = '';
    }
 
    # see https://developers.google.com/accounts/docs/OAuth2WebServer?hl=ru
    # register app here: https://code.google.com/apis/console#access
    function cfg_google($obj = false) {
        if ($obj) # set avatar
            return isset($obj->picture) ? $obj->picture : false;
        $this->app_id = '{APP_ID}';
        $this->secret = '{APP_SECRET}';
        $this->scope = 'email%20profile&response_type=code';
        $this->p0 = ($google = 'https://accounts.google.com/o/oauth2') . '/auth?';
        if (isset($_GET['force']))
            $this->p0 .= 'approval_prompt=force&';
        $this->p1 = "$google/token";
        $this->is_post = true;
        $this->fields = "&grant_type=authorization_code";
        $this->p2 = 'https://www.googleapis.com/oauth2/v1/userinfo?access_token=';
        $this->verify = 'verified_email';
    }
}