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<?php
require_once('library/asn1.php');
function salmon_key($pubkey) {
$lines = explode("\n",$pubkey);
unset($lines[0]);
unset($lines[count($lines)]);
$x = base64_decode(implode('',$lines));
$r = ASN_BASE::parseASNString($x);
$m = $r[0]->asnData[1]->asnData[0]->asnData[0]->asnData;
$e = $r[0]->asnData[1]->asnData[0]->asnData[1]->asnData;
return 'RSA' . '.' . $m . '.' . $e ;
}
function base64url_encode($s) {
return strtr(base64_encode($s),'+/','-_');
}
function base64url_decode($s) {
return base64_decode(strtr($s,'-_','+/'));
}
function get_salmon_key($uri,$keyhash) {
$ret = array();
$debugging = get_config('system','debugging');
if($debugging)
file_put_contents('salmon.out', "\n" . 'Fetch key' . "\n", FILE_APPEND);
$arr = lrdd($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]);
}
}
if($debugging)
file_put_contents('salmon.out', "\n" . 'Key located: ' . print_r($ret,true) . "\n", FILE_APPEND);
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,$contact,$slap) {
// does contact have a salmon endpoint?
if(! strlen($contact['notify']))
return;
// add all namespaces to item
$namespaces = <<< EOT
<entry xmlns="http://www.w3.org/2005/Atom"
xmlns:thr="http://purl.org/syndication/thread/1.0"
xmlns:at="http://purl.org/atompub/tombstones/1.0"
xmlns:media="http://purl.org/syndication/atommedia"
xmlns:dfrn="http://purl.org/macgirvin/dfrn/1.0"
xmlns:as="http://activitystrea.ms/spec/1.0/"
xmlns:georss="http://www.georss.org/georss"
xmlns:poco="http://portablecontacts.net/spec/1.0" >
EOT;
$slap = str_replace('<entry>',$namespaces,$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'])));
// Setup RSA stuff to PKCS#1 sign the data
set_include_path(get_include_path() . PATH_SEPARATOR . 'phpsec');
require_once('phpsec/Crypt/RSA.php');
$rsa = new CRYPT_RSA();
$rsa->signatureMode = CRYPT_RSA_SIGNATURE_PKCS1;
$rsa->setHash('sha256');
$rsa->loadKey($owner['sprvkey']);
// precomputed base64url encoding of data_type, encoding, algorithm concatenated with periods
$precomputed = '.YXBwbGljYXRpb24vYXRvbSt4bWw=.YmFzZTY0dXJs.UlNBLVNIQTI1Ng==';
$signature = base64url_encode($rsa->sign($data . $precomputed));
$signature2 = base64url_encode($rsa->sign($data));
$salmon_tpl = load_view_file('view/magicsig.tpl');
$salmon = replace_macros($salmon_tpl,array(
'$data' => $data,
'$encoding' => $encoding,
'$algorithm' => $algorithm,
'$keyhash' => $keyhash,
'$signature' => $signature
));
// slap them
post_url($contact['notify'],$salmon, array(
'Content-type: application/magic-envelope+xml',
'Content-length: ' . strlen($salmon)
));
$a = get_app();
$return_code = trim($a->get_curl_code());
// check for success, e.g. 2xx
if(substr($return_code,0,1) !== '2') {
// 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' => $signature2
));
// slap them
post_url($contact['notify'],$salmon, array(
'Content-type: application/magic-envelope+xml',
'Content-length: ' . strlen($salmon)
));
$return_code = trim($a->get_curl_code());
}
return;
}
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