From 8abac5e5c7128748f8bc8cc8c52ebf37874023c4 Mon Sep 17 00:00:00 2001
From: Mike Macgirvin <mike@macgirvin.com>
Date: Mon, 4 Oct 2010 05:13:10 -0700
Subject: some tools we'll require going forward

---
 library/oauth.php | 728 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 728 insertions(+)
 create mode 100644 library/oauth.php

(limited to 'library/oauth.php')

diff --git a/library/oauth.php b/library/oauth.php
new file mode 100644
index 000000000..caf1a0839
--- /dev/null
+++ b/library/oauth.php
@@ -0,0 +1,728 @@
+<?php
+
+//ini_set('display_errors', 1);
+//error_reporting(E_ALL | E_STRICT);
+
+// Regex to filter out the client identifier
+// (described in Section 2 of IETF draft)
+// IETF draft does not prescribe a format for these, however
+// I've arbitrarily chosen alphanumeric strings with hyphens and underscores, 3-12 characters long
+// Feel free to change.
+define("REGEX_CLIENT_ID", "/^[a-z0-9-_]{3,12}$/i");
+
+// Used to define the name of the OAuth access token parameter (POST/GET/etc.)
+// IETF Draft sections 5.2 and 5.3 specify that it should be called "oauth_token"
+// but other implementations use things like "access_token"
+// I won't be heartbroken if you change it, but it might be better to adhere to the spec
+define("OAUTH_TOKEN_PARAM_NAME", "oauth_token");
+
+// Client types (for client authorization)
+//define("WEB_SERVER_CLIENT_TYPE", "web_server");
+//define("USER_AGENT_CLIENT_TYPE", "user_agent");
+//define("REGEX_CLIENT_TYPE", "/^(web_server|user_agent)$/");
+define("ACCESS_TOKEN_AUTH_RESPONSE_TYPE", "token");
+define("AUTH_CODE_AUTH_RESPONSE_TYPE", "code");
+define("CODE_AND_TOKEN_AUTH_RESPONSE_TYPE", "code-and-token");
+define("REGEX_AUTH_RESPONSE_TYPE", "/^(token|code|code-and-token)$/");
+
+// Grant Types (for token obtaining)
+define("AUTH_CODE_GRANT_TYPE", "authorization-code");
+define("USER_CREDENTIALS_GRANT_TYPE", "basic-credentials");
+define("ASSERTION_GRANT_TYPE", "assertion");
+define("REFRESH_TOKEN_GRANT_TYPE", "refresh-token");
+define("NONE_GRANT_TYPE", "none");
+define("REGEX_TOKEN_GRANT_TYPE", "/^(authorization-code|basic-credentials|assertion|refresh-token|none)$/");
+
+/* Error handling constants */
+
+// HTTP status codes
+define("ERROR_NOT_FOUND", "404 Not Found");
+define("ERROR_BAD_REQUEST", "400 Bad Request");
+
+// TODO: Extend for i18n
+
+// "Official" OAuth 2.0 errors
+define("ERROR_REDIRECT_URI_MISMATCH", "redirect-uri-mismatch");
+define("ERROR_INVALID_CLIENT_CREDENTIALS", "invalid-client-credentials");
+define("ERROR_UNAUTHORIZED_CLIENT", "unauthorized-client");
+define("ERROR_USER_DENIED", "access-denied");
+define("ERROR_INVALID_REQUEST", "invalid-request");
+define("ERROR_INVALID_CLIENT_ID", "invalid-client-id");
+define("ERROR_UNSUPPORTED_RESPONSE_TYPE", "unsupported-response-type");
+define("ERROR_INVALID_SCOPE", "invalid-scope");
+define("ERROR_INVALID_GRANT", "invalid-grant");
+
+// Protected resource errors
+define("ERROR_INVALID_TOKEN", "invalid-token");
+define("ERROR_EXPIRED_TOKEN", "expired-token");
+define("ERROR_INSUFFICIENT_SCOPE", "insufficient-scope");
+
+// Messages
+define("ERROR_INVALID_RESPONSE_TYPE", "Invalid response type.");
+
+// Errors that we made up
+
+// Error for trying to use a grant type that we haven't implemented
+define("ERROR_UNSUPPORTED_GRANT_TYPE", "unsupported-grant-type");
+
+abstract class OAuth2 {
+
+    /* Subclasses must implement the following functions */
+
+    // Make sure that the client id is valid
+    // If a secret is required, check that they've given the right one
+    // Must return false if the client credentials are invalid
+    abstract protected function auth_client_credentials($client_id, $client_secret = null);
+
+    // OAuth says we should store request URIs for each registered client
+    // Implement this function to grab the stored URI for a given client id
+    // Must return false if the given client does not exist or is invalid
+    abstract protected function get_redirect_uri($client_id);
+
+    // We need to store and retrieve access token data as we create and verify tokens
+    // Implement these functions to do just that
+
+    // Look up the supplied token id from storage, and return an array like:
+    //
+    //  array(
+    //      "client_id" => <stored client id>,
+    //      "expires" => <stored expiration timestamp>,
+    //      "scope" => <stored scope (may be null)
+    //  )
+    //
+    //  Return null if the supplied token is invalid
+    //
+    abstract protected function get_access_token($token_id);
+
+    // Store the supplied values
+    abstract protected function store_access_token($token_id, $client_id, $expires, $scope = null);
+
+    /*
+     *
+     * Stuff that should get overridden by subclasses
+     *
+     * I don't want to make these abstract, because then subclasses would have
+     * to implement all of them, which is too much work.
+     *
+     * So they're just stubs.  Override the ones you need.
+     *
+     */
+
+    // You should override this function with something,
+    // or else your OAuth provider won't support any grant types!
+    protected function get_supported_grant_types() {
+        // If you support all grant types, then you'd do:
+        // return array(
+        //             AUTH_CODE_GRANT_TYPE,
+        //             USER_CREDENTIALS_GRANT_TYPE,
+        //             ASSERTION_GRANT_TYPE,
+        //             REFRESH_TOKEN_GRANT_TYPE,
+        //             NONE_GRANT_TYPE
+        //     );
+
+        return array();
+    }
+
+    // You should override this function with your supported response types
+    protected function get_supported_auth_response_types() {
+        return array(
+            AUTH_CODE_AUTH_RESPONSE_TYPE,
+            ACCESS_TOKEN_AUTH_RESPONSE_TYPE,
+            CODE_AND_TOKEN_AUTH_RESPONSE_TYPE
+        );
+    }
+
+    // If you want to support scope use, then have this function return a list
+    // of all acceptable scopes (used to throw the invalid-scope error)
+    protected function get_supported_scopes() {
+        //  Example:
+        //  return array("my-friends", "photos", "whatever-else");
+        return array();
+    }
+
+    // If you want to restrict clients to certain authorization response types,
+    // override this function
+    // Given a client identifier and auth type, return true or false
+    // (auth type would be one of the values contained in REGEX_AUTH_RESPONSE_TYPE)
+    protected function authorize_client_response_type($client_id, $response_type) {
+        return true;
+    }
+
+    // If you want to restrict clients to certain grant types, override this function
+    // Given a client identifier and grant type, return true or false
+    protected function authorize_client($client_id, $grant_type) {
+        return true;
+    }
+
+    /* Functions that help grant access tokens for various grant types */
+
+    // Fetch authorization code data (probably the most common grant type)
+    // IETF Draft 4.1.1: http://tools.ietf.org/html/draft-ietf-oauth-v2-08#section-4.1.1
+    // Required for AUTH_CODE_GRANT_TYPE
+    protected function get_stored_auth_code($code) {
+        // Retrieve the stored data for the given authorization code
+        // Should return:
+        //
+        // array (
+        //  "client_id" => <stored client id>,
+        //  "redirect_uri" => <stored redirect URI>,
+        //  "expires" => <stored code expiration time>,
+        //  "scope" => <stored scope values (space-separated string), or can be omitted if scope is unused>
+        // )
+        //
+        // Return null if the code is invalid.
+
+        return null;
+    }
+
+    // Take the provided authorization code values and store them somewhere (db, etc.)
+    // Required for AUTH_CODE_GRANT_TYPE
+    protected function store_auth_code($code, $client_id, $redirect_uri, $expires, $scope) {
+        // This function should be the storage counterpart to get_stored_auth_code
+
+        // If storage fails for some reason, we're not currently checking
+        // for any sort of success/failure, so you should bail out of the
+        // script and provide a descriptive fail message
+    }
+
+    // Grant access tokens for basic user credentials
+    // IETF Draft 4.1.2: http://tools.ietf.org/html/draft-ietf-oauth-v2-08#section-4.1.2
+    // Required for USER_CREDENTIALS_GRANT_TYPE
+    protected function check_user_credentials($client_id, $username, $password) {
+        // Check the supplied username and password for validity
+        // You can also use the $client_id param to do any checks required
+        // based on a client, if you need that
+        // If the username and password are invalid, return false
+
+        // If the username and password are valid, and you want to verify the scope of
+        // a user's access, return an array with the scope values, like so:
+        //
+        // array (
+        //  "scope" => <stored scope values (space-separated string)>
+        // )
+        //
+        // We'll check the scope you provide against the requested scope before
+        // providing an access token.
+        //
+        // Otherwise, just return true.
+
+        return false;
+    }
+
+    // Grant access tokens for assertions
+    // IETF Draft 4.1.3: http://tools.ietf.org/html/draft-ietf-oauth-v2-08#section-4.1.3
+    // Required for ASSERTION_GRANT_TYPE
+    protected function check_assertion($client_id, $assertion_type, $assertion) {
+        // Check the supplied assertion for validity
+        // You can also use the $client_id param to do any checks required
+        // based on a client, if you need that
+        // If the assertion is invalid, return false
+
+        // If the assertion is valid, and you want to verify the scope of
+        // an access request, return an array with the scope values, like so:
+        //
+        // array (
+        //  "scope" => <stored scope values (space-separated string)>
+        // )
+        //
+        // We'll check the scope you provide against the requested scope before
+        // providing an access token.
+        //
+        // Otherwise, just return true.
+
+        return false;
+    }
+
+    // Grant refresh access tokens
+    // IETF Draft 4.1.4: http://tools.ietf.org/html/draft-ietf-oauth-v2-08#section-4.1.4
+    // Required for REFRESH_TOKEN_GRANT_TYPE
+    protected function get_refresh_token($refresh_token) {
+        // Retrieve the stored data for the given refresh token
+        // Should return:
+        //
+        // array (
+        //  "client_id" => <stored client id>,
+        //  "expires" => <refresh token expiration time>,
+        //  "scope" => <stored scope values (space-separated string), or can be omitted if scope is unused>
+        // )
+        //
+        // Return null if the token id is invalid.
+
+        return null;
+    }
+
+    // Store refresh access tokens
+    // Required for REFRESH_TOKEN_GRANT_TYPE
+    protected function store_refresh_token($token, $client_id, $expires, $scope = null) {
+        // If storage fails for some reason, we're not currently checking
+        // for any sort of success/failure, so you should bail out of the
+        // script and provide a descriptive fail message
+
+        return;
+    }
+
+    // Grant access tokens for the "none" grant type
+    // Not really described in the IETF Draft, so I just left a method stub...do whatever you want!
+    // Required for NONE_GRANT_TYPE
+    protected function check_none_access($client_id) {
+        return false;
+    }
+
+    protected function get_default_authentication_realm() {
+        // Change this to whatever authentication realm you want to send in a WWW-Authenticate header
+        return "Service";
+    }
+
+    /* End stuff that should get overridden */
+
+    private $access_token_lifetime = 3600;
+    private $auth_code_lifetime = 30;
+    private $refresh_token_lifetime = 1209600; // Two weeks
+
+    public function __construct($access_token_lifetime = 3600, $auth_code_lifetime = 30, $refresh_token_lifetime = 1209600) {
+        $this->access_token_lifetime = $access_token_lifetime;
+        $this->auth_code_lifetime = $auth_code_lifetime;
+        $this->refresh_token_lifetime = $refresh_token_lifetime;
+    }
+
+    /* Resource protecting (Section 5) */
+
+    // Check that a valid access token has been provided
+    //
+    // The scope parameter defines any required scope that the token must have
+    // If a scope param is provided and the token does not have the required scope,
+    // we bounce the request
+    //
+    // Some implementations may choose to return a subset of the protected resource
+    // (i.e. "public" data) if the user has not provided an access token
+    // or if the access token is invalid or expired
+    //
+    // The IETF spec says that we should send a 401 Unauthorized header and bail immediately
+    // so that's what the defaults are set to
+    //
+    // Here's what each parameter does:
+    // $scope = A space-separated string of required scope(s), if you want to check for scope
+    // $exit_not_present = If true and no access token is provided, send a 401 header and exit, otherwise return false
+    // $exit_invalid = If true and the implementation of get_access_token returns null, exit, otherwise return false
+    // $exit_expired = If true and the access token has expired, exit, otherwise return false
+    // $exit_scope = If true the access token does not have the required scope(s), exit, otherwise return false
+    // $realm = If you want to specify a particular realm for the WWW-Authenticate header, supply it here
+    public function verify_access_token($scope = null, $exit_not_present = true, $exit_invalid = true, $exit_expired = true, $exit_scope = true, $realm = null) {
+        $token_param = $this->get_access_token_param();
+        if ($token_param === false) // Access token was not provided
+            return $exit_not_present ? $this->send_401_unauthorized($realm, $scope) : false;
+
+        // Get the stored token data (from the implementing subclass)
+        $token = $this->get_access_token($token_param);
+        if ($token === null)
+            return $exit_invalid ? $this->send_401_unauthorized($realm, $scope, ERROR_INVALID_TOKEN) : false;
+
+        // Check token expiration (I'm leaving this check separated, later we'll fill in better error messages)
+        if (isset($token["expires"]) && time() > $token["expires"])
+            return $exit_expired ? $this->send_401_unauthorized($realm, $scope, ERROR_EXPIRED_TOKEN) : false;
+
+        // Check scope, if provided
+        // If token doesn't have a scope, it's null/empty, or it's insufficient, then throw an error
+        if ($scope &&
+                (!isset($token["scope"]) || !$token["scope"] || !$this->check_scope($scope, $token["scope"])))
+            return $exit_scope ? $this->send_401_unauthorized($realm, $scope, ERROR_INSUFFICIENT_SCOPE) : false;
+
+        return true;
+    }
+
+
+    // Returns true if everything in required scope is contained in available scope
+    // False if something in required scope is not in available scope
+    private function check_scope($required_scope, $available_scope) {
+        // The required scope should match or be a subset of the available scope
+        if (!is_array($required_scope))
+            $required_scope = explode(" ", $required_scope);
+
+        if (!is_array($available_scope))
+            $available_scope = explode(" ", $available_scope);
+
+        return (count(array_diff($required_scope, $available_scope)) == 0);
+    }
+
+    // Send a 401 unauthorized header with the given realm
+    // and an error, if provided
+    private function send_401_unauthorized($realm, $scope, $error = null) {
+        $realm = $realm === null ? $this->get_default_authentication_realm() : $realm;
+
+        $auth_header = "WWW-Authenticate: Token realm='".$realm."'";
+
+        if ($scope)
+            $auth_header .= ", scope='".$scope."'";
+
+        if ($error !== null)
+            $auth_header .= ", error='".$error."'";
+
+        header("HTTP/1.1 401 Unauthorized");
+        header($auth_header);
+
+        exit;
+    }
+
+    // Pulls the access token out of the HTTP request
+    // Either from the Authorization header or GET/POST/etc.
+    // Returns false if no token is present
+    // TODO: Support POST or DELETE
+    private function get_access_token_param() {
+        $auth_header = $this->get_authorization_header();
+
+        if ($auth_header !== false) {
+            // Make sure only the auth header is set
+            if (isset($_GET[OAUTH_TOKEN_PARAM_NAME]) || isset($_POST[OAUTH_TOKEN_PARAM_NAME]))
+                $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+            $auth_header = trim($auth_header);
+
+            // Make sure it's Token authorization
+            if (strcmp(substr($auth_header, 0, 6),"Token ") !== 0)
+                $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+            // Parse the rest of the header
+            if (preg_match('/\s*token\s*="(.+)"/', substr($auth_header, 6), $matches) == 0 || count($matches) < 2)
+                $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+            return $matches[1];
+        }
+
+        if (isset($_GET[OAUTH_TOKEN_PARAM_NAME]))  {
+            if (isset($_POST[OAUTH_TOKEN_PARAM_NAME])) // Both GET and POST are not allowed
+                $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+            return $_GET[OAUTH_TOKEN_PARAM_NAME];
+        }
+
+        if (isset($_POST[OAUTH_TOKEN_PARAM_NAME]))
+            return $_POST[OAUTH_TOKEN_PARAM_NAME];
+
+        return false;
+    }
+
+    /* Access token granting (Section 4) */
+
+    // Grant or deny a requested access token
+    // This would be called from the "/token" endpoint as defined in the spec
+    // Obviously, you can call your endpoint whatever you want
+    public function grant_access_token() {
+        $filters = array(
+            "grant_type" => array("filter" => FILTER_VALIDATE_REGEXP, "options" => array("regexp" => REGEX_TOKEN_GRANT_TYPE), "flags" => FILTER_REQUIRE_SCALAR),
+            "scope" => array("flags" => FILTER_REQUIRE_SCALAR),
+            "code" => array("flags" => FILTER_REQUIRE_SCALAR),
+            "redirect_uri" => array("filter" => FILTER_VALIDATE_URL, "flags" => array(FILTER_FLAG_SCHEME_REQUIRED, FILTER_REQUIRE_SCALAR)),
+            "username" => array("flags" => FILTER_REQUIRE_SCALAR),
+            "password" => array("flags" => FILTER_REQUIRE_SCALAR),
+            "assertion_type" => array("flags" => FILTER_REQUIRE_SCALAR),
+            "assertion" => array("flags" => FILTER_REQUIRE_SCALAR),
+            "refresh_token" => array("flags" => FILTER_REQUIRE_SCALAR),
+        );
+
+        $input = filter_input_array(INPUT_POST, $filters);
+
+        // Grant Type must be specified.
+        if (!$input["grant_type"])
+            $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+        // Make sure we've implemented the requested grant type
+        if (!in_array($input["grant_type"], $this->get_supported_grant_types()))
+            $this->error(ERROR_BAD_REQUEST, ERROR_UNSUPPORTED_GRANT_TYPE);
+
+        // Authorize the client
+        $client = $this->get_client_credentials();
+
+        if ($this->auth_client_credentials($client[0], $client[1]) === false)
+            $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_CLIENT_CREDENTIALS);
+
+        if (!$this->authorize_client($client[0], $input["grant_type"]))
+            $this->error(ERROR_BAD_REQUEST, ERROR_UNAUTHORIZED_CLIENT);
+
+        // Do the granting
+        switch ($input["grant_type"]) {
+            case AUTH_CODE_GRANT_TYPE:
+                if (!$input["code"] || !$input["redirect_uri"])
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+                $stored = $this->get_stored_auth_code($input["code"]);
+
+                if ($stored === null || $input["redirect_uri"] != $stored["redirect_uri"] || $client[0] != $stored["client_id"])
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_GRANT);
+
+                if ($stored["expires"] > time())
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_GRANT);
+
+                break;
+            case USER_CREDENTIALS_GRANT_TYPE:
+                if (!$input["username"] || !$input["password"])
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+                $stored = $this->check_user_credentials($client[0], $input["username"], $input["password"]);
+
+                if ($stored === false)
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_GRANT);
+
+                break;
+            case ASSERTION_GRANT_TYPE:
+                if (!$input["assertion_type"] || !$input["assertion"])
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+                $stored = $this->check_assertion($client[0], $input["assertion_type"], $input["assertion"]);
+
+                if ($stored === false)
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_GRANT);
+
+                break;
+            case REFRESH_TOKEN_GRANT_TYPE:
+                if (!$input["refresh_token"])
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+                $stored = $this->get_refresh_token($input["refresh_token"]);
+
+                if ($stored === null || $client[0] != $stored["client_id"])
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_GRANT);
+
+                if ($stored["expires"] > time())
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_GRANT);
+
+                break;
+            case NONE_GRANT_TYPE:
+                $stored = $this->check_none_access($client[0]);
+
+                if ($stored === false)
+                    $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+        }
+
+        // Check scope, if provided
+        if ($input["scope"] && (!is_array($stored) || !isset($stored["scope"]) || !$this->check_scope($input["scope"], $stored["scope"])))
+            $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_SCOPE);
+
+        if (!$input["scope"])
+            $input["scope"] = null;
+
+        $token = $this->create_access_token($client[0], $input["scope"]);
+
+        $this->send_json_headers();
+        echo json_encode($token);
+    }
+
+    // Internal function used to get the client credentials from HTTP basic auth or POST data
+    // See http://tools.ietf.org/html/draft-ietf-oauth-v2-08#section-2
+    private function get_client_credentials() {
+        if (isset($_SERVER["PHP_AUTH_USER"]) && $_POST && isset($_POST["client_id"]))
+            $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_CLIENT_CREDENTIALS);
+
+        // Try basic auth
+        if (isset($_SERVER["PHP_AUTH_USER"]))
+            return array($_SERVER["PHP_AUTH_USER"], $_SERVER["PHP_AUTH_PW"]);
+
+        // Try POST
+        if ($_POST && isset($_POST["client_id"])) {
+            if (isset($_POST["client_secret"]))
+                return array($_POST["client_id"], $_POST["client_secret"]);
+
+            return array($_POST["client_id"], NULL);
+        }
+
+        // No credentials were specified
+        $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_CLIENT_CREDENTIALS);
+    }
+
+    /* End-user/client Authorization (Section 3 of IETF Draft) */
+
+    // Pull the authorization request data out of the HTTP request
+    // and return it so the authorization server can prompt the user
+    // for approval
+    public function get_authorize_params() {
+        $filters = array(
+            "client_id" => array("filter" => FILTER_VALIDATE_REGEXP, "options" => array("regexp" => REGEX_CLIENT_ID), "flags" => FILTER_REQUIRE_SCALAR),
+            "response_type" => array("filter" => FILTER_VALIDATE_REGEXP, "options" => array("regexp" => REGEX_AUTH_RESPONSE_TYPE), "flags" => FILTER_REQUIRE_SCALAR),
+            "redirect_uri" => array("filter" => FILTER_VALIDATE_URL, "flags" => array(FILTER_FLAG_SCHEME_REQUIRED, FILTER_REQUIRE_SCALAR)),
+            "state" => array("flags" => FILTER_REQUIRE_SCALAR),
+            "scope" => array("flags" => FILTER_REQUIRE_SCALAR),
+        );
+
+        $input = filter_input_array(INPUT_GET, $filters);
+
+        // Make sure a valid client id was supplied
+        if (!$input["client_id"]) {
+            if ($input["redirect_uri"])
+                $this->callback_error($input["redirect_uri"], ERROR_INVALID_CLIENT_ID, $input["state"]);
+
+            $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_CLIENT_ID); // We don't have a good URI to use
+        }
+
+        // redirect_uri is not required if already established via other channels
+        // check an existing redirect URI against the one supplied
+        $redirect_uri = $this->get_redirect_uri($input["client_id"]);
+
+        // At least one of: existing redirect URI or input redirect URI must be specified
+        if (!$redirect_uri && !$input["redirect_uri"])
+            $this->error(ERROR_BAD_REQUEST, ERROR_INVALID_REQUEST);
+
+        // get_redirect_uri should return false if the given client ID is invalid
+        // this probably saves us from making a separate db call, and simplifies the method set
+        if ($redirect_uri === false)
+            $this->callback_error($input["redirect_uri"], ERROR_INVALID_CLIENT_ID, $input["state"]);
+
+        // If there's an existing uri and one from input, verify that they match
+        if ($redirect_uri && $input["redirect_uri"]) {
+            // Ensure that the input uri starts with the stored uri
+            if (strcasecmp(substr($input["redirect_uri"], 0, strlen($redirect_uri)),$redirect_uri) !== 0)
+                $this->callback_error($input["redirect_uri"], ERROR_REDIRECT_URI_MISMATCH, $input["state"]);
+        } elseif ($redirect_uri) { // They did not provide a uri from input, so use the stored one
+            $input["redirect_uri"] = $redirect_uri;
+        }
+
+        // type and client_id are required
+        if (!$input["response_type"])
+            $this->callback_error($input["redirect_uri"], ERROR_INVALID_REQUEST, $input["state"], ERROR_INVALID_RESPONSE_TYPE);
+
+        // Check requested auth response type against the list of supported types
+        if (array_search($input["response_type"], $this->get_supported_auth_response_types()) === false)
+            $this->callback_error($input["redirect_uri"], ERROR_UNSUPPORTED_RESPONSE_TYPE, $input["state"]);
+
+        // Validate that the requested scope is supported
+        if ($input["scope"] && !$this->check_scope($input["scope"], $this->get_supported_scopes()))
+            $this->callback_error($input["redirect_uri"], ERROR_INVALID_SCOPE, $input["state"]);
+
+        return $input;
+    }
+
+    // After the user has approved or denied the access request
+    // the authorization server should call this function to redirect
+    // the user appropriately
+
+    // The params all come from the results of get_authorize_params
+    // except for $is_authorized -- this is true or false depending on whether
+    // the user authorized the access
+    public function finish_client_authorization($is_authorized, $type, $client_id, $redirect_uri, $state, $scope = null) {
+        if ($state !== null)
+            $result["query"]["state"] = $state;
+
+        if ($is_authorized === false) {
+            $result["query"]["error"] = ERROR_USER_DENIED;
+        } else {
+            if ($type == AUTH_CODE_AUTH_RESPONSE_TYPE || $type == CODE_AND_TOKEN_AUTH_RESPONSE_TYPE)
+                $result["query"]["code"] = $this->create_auth_code($client_id, $redirect_uri, $scope);
+
+            if ($type == ACCESS_TOKEN_AUTH_RESPONSE_TYPE || $type == CODE_AND_TOKEN_AUTH_RESPONSE_TYPE)
+                $result["fragment"] = $this->create_access_token($client_id, $scope);
+        }
+
+        $this->do_redirect_uri_callback($redirect_uri, $result);
+    }
+
+    /* Other/utility functions */
+
+    private function do_redirect_uri_callback($redirect_uri, $result) {
+        header("HTTP/1.1 302 Found");
+        header("Location: " . $this->build_uri($redirect_uri, $result));
+        exit;
+    }
+
+    private function build_uri($uri, $data) {
+        $parse_url = parse_url($uri);
+
+        // Add our data to the parsed uri
+        foreach ($data as $k => $v) {
+            if (isset($parse_url[$k]))
+                $parse_url[$k] .= "&" . http_build_query($v);
+            else
+                $parse_url[$k] = http_build_query($v);
+        }
+
+        // Put humpty dumpty back together
+        return
+             ((isset($parse_url["scheme"])) ? $parse_url["scheme"] . "://" : "")
+            .((isset($parse_url["user"])) ? $parse_url["user"] . ((isset($parse_url["pass"])) ? ":" . $parse_url["pass"] : "") ."@" : "")
+            .((isset($parse_url["host"])) ? $parse_url["host"] : "")
+            .((isset($parse_url["port"])) ? ":" . $parse_url["port"] : "")
+            .((isset($parse_url["path"])) ? $parse_url["path"] : "")
+            .((isset($parse_url["query"])) ? "?" . $parse_url["query"] : "")
+            .((isset($parse_url["fragment"])) ? "#" . $parse_url["fragment"] : "");
+    }
+
+    // This belongs in a separate factory, but to keep it simple, I'm just keeping it here.
+    private function create_access_token($client_id, $scope) {
+        $token = array(
+            "access_token" => $this->gen_access_token(),
+            "expires_in" => $this->access_token_lifetime,
+            "scope" => $scope
+        );
+
+        $this->store_access_token($token["access_token"], $client_id, time() + $this->access_token_lifetime, $scope);
+
+        // Issue a refresh token also, if we support them
+        if (in_array(REFRESH_TOKEN_GRANT_TYPE, $this->get_supported_grant_types())) {
+            $token["refresh_token"] = $this->gen_access_token();
+            $this->store_refresh_token($token["refresh_token"], $client_id, time() + $this->refresh_token_lifetime, $scope);
+        }
+
+        return $token;
+    }
+
+    private function create_auth_code($client_id, $redirect_uri, $scope) {
+        $code = $this->gen_auth_code();
+        $this->store_auth_code($code, $client_id, $redirect_uri, time() + $this->auth_code_lifetime, $scope);
+        return $code;
+    }
+
+    // Implementing classes may want to override these two functions
+    // to implement other access token or auth code generation schemes
+    private function gen_access_token() {
+        return base64_encode(pack('N6', mt_rand(), mt_rand(), mt_rand(), mt_rand(), mt_rand(), mt_rand()));
+    }
+
+    private function gen_auth_code() {
+        return base64_encode(pack('N6', mt_rand(), mt_rand(), mt_rand(), mt_rand(), mt_rand(), mt_rand()));
+    }
+
+    // Implementing classes may need to override this function for use on non-Apache web servers
+    // Just pull out the Authorization HTTP header and return it
+    // Return false if the Authorization header does not exist
+    private function get_authorization_header() {
+        if (array_key_exists("HTTP_AUTHORIZATION", $_SERVER))
+            return $_SERVER["HTTP_AUTHORIZATION"];
+
+        if (function_exists("apache_request_headers")) {
+            $headers = apache_request_headers();
+
+            if (array_key_exists("Authorization", $headers))
+                return $headers["Authorization"];
+        }
+
+        return false;
+    }
+
+    private function send_json_headers() {
+        header("Content-Type: application/json");
+        header("Cache-Control: no-store");
+    }
+
+    public function error($code, $message = null) {
+        header("HTTP/1.1 " . $code);
+
+        if ($message) {
+            $this->send_json_headers();
+            echo json_encode(array("error" => $message));
+        }
+
+        exit;
+    }
+
+    public function callback_error($redirect_uri, $error, $state, $message = null, $error_uri = null) {
+        $result["query"]["error"] = $error;
+
+        if ($state)
+            $result["query"]["state"] = $state;
+
+        if ($message)
+            $result["query"]["error_description"] = $message;
+
+        if ($error_uri)
+            $result["query"]["error_uri"] = $error_uri;
+
+        $this->do_redirect_uri_callback($redirect_uri, $result);
+    }
+}
\ No newline at end of file
-- 
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