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<?php
namespace IMSGlobal\LTI\OAuth;
/**
* Class to represent an %OAuth Server
*
* @copyright Andy Smith
* @version 2008-08-04
* @license https://opensource.org/licenses/MIT The MIT License
*/
class OAuthServer {
protected $timestamp_threshold = 300; // in seconds, five minutes
protected $version = '1.0'; // hi blaine
protected $signature_methods = array();
protected $data_store;
function __construct($data_store) {
$this->data_store = $data_store;
}
public function add_signature_method($signature_method) {
$this->signature_methods[$signature_method->get_name()] = $signature_method;
}
// high level functions
/**
* process a request_token request
* returns the request token on success
*/
public function fetch_request_token(&$request) {
$this->get_version($request);
$consumer = $this->get_consumer($request);
// no token required for the initial token request
$token = NULL;
$this->check_signature($request, $consumer, $token);
// Rev A change
$callback = $request->get_parameter('oauth_callback');
$new_token = $this->data_store->new_request_token($consumer, $callback);
return $new_token;
}
/**
* process an access_token request
* returns the access token on success
*/
public function fetch_access_token(&$request) {
$this->get_version($request);
$consumer = $this->get_consumer($request);
// requires authorized request token
$token = $this->get_token($request, $consumer, "request");
$this->check_signature($request, $consumer, $token);
// Rev A change
$verifier = $request->get_parameter('oauth_verifier');
$new_token = $this->data_store->new_access_token($token, $consumer, $verifier);
return $new_token;
}
/**
* verify an api call, checks all the parameters
*/
public function verify_request(&$request) {
$this->get_version($request);
$consumer = $this->get_consumer($request);
$token = $this->get_token($request, $consumer, "access");
$this->check_signature($request, $consumer, $token);
return array($consumer, $token);
}
// Internals from here
/**
* version 1
*/
private function get_version(&$request) {
$version = $request->get_parameter("oauth_version");
if (!$version) {
// Service Providers MUST assume the protocol version to be 1.0 if this parameter is not present.
// Chapter 7.0 ("Accessing Protected Ressources")
$version = '1.0';
}
if ($version !== $this->version) {
throw new OAuthException("OAuth version '$version' not supported");
}
return $version;
}
/**
* figure out the signature with some defaults
*/
private function get_signature_method($request) {
$signature_method = $request instanceof OAuthRequest
? $request->get_parameter('oauth_signature_method') : NULL;
if (!$signature_method) {
// According to chapter 7 ("Accessing Protected Ressources") the signature-method
// parameter is required, and we can't just fallback to PLAINTEXT
throw new OAuthException('No signature method parameter. This parameter is required');
}
if (!in_array($signature_method,
array_keys($this->signature_methods))) {
throw new OAuthException(
"Signature method '$signature_method' not supported " .
'try one of the following: ' .
implode(', ', array_keys($this->signature_methods))
);
}
return $this->signature_methods[$signature_method];
}
/**
* try to find the consumer for the provided request's consumer key
*/
private function get_consumer($request) {
$consumer_key = $request instanceof OAuthRequest
? $request->get_parameter('oauth_consumer_key') : NULL;
if (!$consumer_key) {
throw new OAuthException('Invalid consumer key');
}
$consumer = $this->data_store->lookup_consumer($consumer_key);
if (!$consumer) {
throw new OAuthException('Invalid consumer');
}
return $consumer;
}
/**
* try to find the token for the provided request's token key
*/
private function get_token($request, $consumer, $token_type="access") {
$token_field = $request instanceof OAuthRequest
? $request->get_parameter('oauth_token') : NULL;
$token = $this->data_store->lookup_token($consumer, $token_type, $token_field);
if (!$token) {
throw new OAuthException("Invalid $token_type token: $token_field");
}
return $token;
}
/**
* all-in-one function to check the signature on a request
* should guess the signature method appropriately
*/
private function check_signature($request, $consumer, $token) {
// this should probably be in a different method
$timestamp = $request instanceof OAuthRequest
? $request->get_parameter('oauth_timestamp')
: NULL;
$nonce = $request instanceof OAuthRequest
? $request->get_parameter('oauth_nonce')
: NULL;
$this->check_timestamp($timestamp);
$this->check_nonce($consumer, $token, $nonce, $timestamp);
$signature_method = $this->get_signature_method($request);
$signature = $request->get_parameter('oauth_signature');
$valid_sig = $signature_method->check_signature($request, $consumer, $token, $signature);
if (!$valid_sig) {
throw new OAuthException('Invalid signature');
}
}
/**
* check that the timestamp is new enough
*/
private function check_timestamp($timestamp) {
if(!$timestamp)
throw new OAuthException('Missing timestamp parameter. The parameter is required');
// verify that timestamp is recentish
$now = time();
if (abs($now - $timestamp) > $this->timestamp_threshold) {
throw new OAuthException("Expired timestamp, yours $timestamp, ours $now");
}
}
/**
* check that the nonce is not repeated
*/
private function check_nonce($consumer, $token, $nonce, $timestamp) {
if(!$nonce)
throw new OAuthException('Missing nonce parameter. The parameter is required');
// verify that the nonce is uniqueish
$found = $this->data_store->lookup_nonce($consumer, $token, $nonce, $timestamp);
if ($found) {
throw new OAuthException("Nonce already used: $nonce");
}
}
}