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<?php
namespace IMSGlobal\LTI\OAuth;
/**
* Class to represent an %OAuth Signature Method
*
* @copyright Andy Smith
* @version 2008-08-04
* @license https://opensource.org/licenses/MIT The MIT License
*/
/**
* A class for implementing a Signature Method
* See section 9 ("Signing Requests") in the spec
*/
abstract class OAuthSignatureMethod {
/**
* Needs to return the name of the Signature Method (ie HMAC-SHA1)
* @return string
*/
abstract public function get_name();
/**
* Build up the signature
* NOTE: The output of this function MUST NOT be urlencoded.
* the encoding is handled in OAuthRequest when the final
* request is serialized
* @param OAuthRequest $request
* @param OAuthConsumer $consumer
* @param OAuthToken $token
* @return string
*/
abstract public function build_signature($request, $consumer, $token);
/**
* Verifies that a given signature is correct
* @param OAuthRequest $request
* @param OAuthConsumer $consumer
* @param OAuthToken $token
* @param string $signature
* @return bool
*/
public function check_signature($request, $consumer, $token, $signature) {
$built = $this->build_signature($request, $consumer, $token);
// Check for zero length, although unlikely here
if (strlen($built) == 0 || strlen($signature) == 0) {
return false;
}
if (strlen($built) != strlen($signature)) {
return false;
}
// Avoid a timing leak with a (hopefully) time insensitive compare
$result = 0;
for ($i = 0; $i < strlen($signature); $i++) {
$result |= ord($built[$i]) ^ ord($signature[$i]);
}
return $result == 0;
}
}