friendica/include/salmon.php

<?php

require_once('include/crypto.php');



function get_salmon_key($uri,$keyhash) {
	$ret = array();

	logger('Fetching salmon key for '.$uri);

	$arr = lrdd($uri);

	if(is_array($arr)) {
		foreach($arr as $a) {
			if($a['@attributes']['rel'] === 'magic-public-key') {
				$ret[] = $a['@attributes']['href'];
			}
		}
	}
	else {
		return '';
	}

	// We have found at least one key URL
	// If it's inline, parse it - otherwise get the key

	if(count($ret)) {
		for($x = 0; $x < count($ret); $x ++) {
			if(substr($ret[$x],0,5) === 'data:') {
				if(strstr($ret[$x],','))
					$ret[$x] = substr($ret[$x],strpos($ret[$x],',')+1);
				else
					$ret[$x] = substr($ret[$x],5);
			}
			else
				$ret[$x] = fetch_url($ret[$x]);
		}
	}


	logger('Key located: ' . print_r($ret,true));

	if(count($ret) == 1) {

		// We only found one one key so we don't care if the hash matches.
		// If it's the wrong key we'll find out soon enough because
		// message verification will fail. This also covers some older
		// software which don't supply a keyhash. As long as they only
		// have one key we'll be right.

		return $ret[0];
	}
	else {
		foreach($ret as $a) {
			$hash = base64url_encode(hash('sha256',$a));
			if($hash == $keyhash)
				return $a;
		}
	}

	return '';
}



function slapper($owner,$url,$slap) {

	// does contact have a salmon endpoint?

	if(! strlen($url))
		return;


	if(! $owner['sprvkey']) {
		logger(sprintf("user '%s' (%d) does not have a salmon private key. Send failed.",
		$owner['username'],$owner['uid']));
		return;
	}

	logger('slapper called for '.$url.'. Data: ' . $slap);

	// create a magic envelope

	$data      = base64url_encode($slap);
	$data_type = 'application/atom+xml';
	$encoding  = 'base64url';
	$algorithm = 'RSA-SHA256';
	$keyhash   = base64url_encode(hash('sha256',salmon_key($owner['spubkey'])),true);

	// precomputed base64url encoding of data_type, encoding, algorithm concatenated with periods

	$precomputed = '.YXBwbGljYXRpb24vYXRvbSt4bWw=.YmFzZTY0dXJs.UlNBLVNIQTI1Ng==';

	$signature   = base64url_encode(rsa_sign(str_replace('=','',$data . $precomputed),$owner['sprvkey']));

	$signature2  = base64url_encode(rsa_sign($data . $precomputed,$owner['sprvkey']));

	$signature3  = base64url_encode(rsa_sign($data,$owner['sprvkey']));

	$salmon_tpl = get_markup_template('magicsig.tpl');

	$salmon = replace_macros($salmon_tpl,array(
		'$data'      => $data,
		'$encoding'  => $encoding,
		'$algorithm' => $algorithm,
		'$keyhash'   => $keyhash,
		'$signature' => $signature
	));

	// slap them
	post_url($url,$salmon, array(
		'Content-type: application/magic-envelope+xml',
		'Content-length: ' . strlen($salmon)
	));

	$a = get_app();
	$return_code = $a->get_curl_code();

	// check for success, e.g. 2xx

	if($return_code > 299) {

		logger('compliant salmon failed. Falling back to status.net hack2');

		// Entirely likely that their salmon implementation is
		// non-compliant. Let's try once more, this time only signing
		// the data, without stripping '=' chars

		$salmon = replace_macros($salmon_tpl,array(
			'$data'      => $data,
			'$encoding'  => $encoding,
			'$algorithm' => $algorithm,
			'$keyhash'   => $keyhash,
			'$signature' => $signature2
		));

		// slap them
		post_url($url,$salmon, array(
			'Content-type: application/magic-envelope+xml',
			'Content-length: ' . strlen($salmon)
		));
		$return_code = $a->get_curl_code();


		if($return_code > 299) {

			logger('compliant salmon failed. Falling back to status.net hack3');

			// Entirely likely that their salmon implementation is
			// non-compliant. Let's try once more, this time only signing
			// the data, without the precomputed blob

			$salmon = replace_macros($salmon_tpl,array(
				'$data'      => $data,
				'$encoding'  => $encoding,
				'$algorithm' => $algorithm,
				'$keyhash'   => $keyhash,
				'$signature' => $signature3
			));

			// slap them
			post_url($url,$salmon, array(
				'Content-type: application/magic-envelope+xml',
				'Content-length: ' . strlen($salmon)
			));
			$return_code = $a->get_curl_code();
		}
	}
	logger('slapper for '.$url.' returned ' . $return_code);
	if(! $return_code)
		return(-1);
	if(($return_code == 503) && (stristr($a->get_curl_headers(),'retry-after')))
		return(-1);

	return ((($return_code >= 200) && ($return_code < 300)) ? 0 : 1);
}