gnu-social/plugins/OStatus/lib/magicenvelope.php

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<?php
/**
* StatusNet - the distributed open-source microblogging tool
* Copyright (C) 2010, StatusNet, Inc.
*
* A sample module to show best practices for StatusNet plugins
*
* PHP version 5
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @package StatusNet
* @author James Walker <james@status.net>
* @copyright 2010 StatusNet, Inc.
* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
* @link http://status.net/
*/
class MagicEnvelope
{
const ENCODING = 'base64url';
const NS = 'http://salmon-protocol.org/ns/magic-env';
/**
* Get the Salmon keypair from a URI, uses XRD Discovery etc.
*
* @return Magicsig with loaded keypair
*/
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public function getKeyPair($signer_uri)
{
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$disco = new Discovery();
// Throws exception on lookup problems
$xrd = $disco->lookup($signer_uri);
$link = $xrd->get(Magicsig::PUBLICKEYREL);
if (is_null($link)) {
// TRANS: Exception.
throw new Exception(_m('Unable to locate signer public key.'));
}
// We have a public key element, let's hope it has proper key data.
$keypair = false;
$parts = explode(',', $link->href);
if (count($parts) == 2) {
$keypair = $parts[1];
} else {
// Backwards compatibility check for separator bug in 0.9.0
$parts = explode(';', $link->href);
if (count($parts) == 2) {
$keypair = $parts[1];
}
}
if ($keypair === false) {
// For debugging clarity. Keypair did not pass count()-check above.
// TRANS: Exception when public key was not properly formatted.
throw new Exception(_m('Incorrectly formatted public key element.'));
}
$magicsig = Magicsig::fromString($keypair);
if (!$magicsig instanceof Magicsig) {
common_debug('Salmon error: unable to parse keypair: '.var_export($keypair,true));
// TRANS: Exception when public key was properly formatted but not parsable.
throw new ServerException(_m('Retrieved Salmon keypair could not be parsed.'));
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}
return $magicsig;
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}
/**
* The current MagicEnvelope spec as used in StatusNet 0.9.7 and later
* includes both the original data and some signing metadata fields as
* the input plaintext for the signature hash.
*
* @param array $env
* @return string
*/
public function signingText($env) {
return implode('.', array($env['data'], // this field is pre-base64'd
Magicsig::base64_url_encode($env['data_type']),
Magicsig::base64_url_encode($env['encoding']),
Magicsig::base64_url_encode($env['alg'])));
}
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/**
*
* @param <type> $text
* @param <type> $mimetype
* @param <type> $keypair
* @return array: associative array of envelope properties
* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
*/
public function signMessage($text, $mimetype, $keypair)
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{
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$signature_alg = Magicsig::fromString($keypair);
$armored_text = Magicsig::base64_url_encode($text);
$env = array(
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'data' => $armored_text,
'encoding' => MagicEnvelope::ENCODING,
'data_type' => $mimetype,
'sig' => '',
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'alg' => $signature_alg->getName()
);
$env['sig'] = $signature_alg->sign($this->signingText($env));
return $env;
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}
/**
* Create an <me:env> XML representation of the envelope.
*
* @param array $env associative array with envelope data
* @return string representation of XML document
* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
*/
public function toXML($env) {
$xs = new XMLStringer();
$xs->startXML();
$xs->elementStart('me:env', array('xmlns:me' => MagicEnvelope::NS));
$xs->element('me:data', array('type' => $env['data_type']), $env['data']);
$xs->element('me:encoding', null, $env['encoding']);
$xs->element('me:alg', null, $env['alg']);
$xs->element('me:sig', null, $env['sig']);
$xs->elementEnd('me:env');
$string = $xs->getString();
common_debug($string);
return $string;
}
/**
* Extract the contained XML payload, and insert a copy of the envelope
* signature data as an <me:provenance> section.
*
* @param array $env associative array with envelope data
* @return string representation of modified XML document
*
* @fixme in case of XML parsing errors, this will spew to the error log or output
* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
*/
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public function unfold($env)
{
$dom = new DOMDocument();
$dom->loadXML(Magicsig::base64_url_decode($env['data']));
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if ($dom->documentElement->tagName != 'entry') {
return false;
}
$prov = $dom->createElementNS(MagicEnvelope::NS, 'me:provenance');
$prov->setAttribute('xmlns:me', MagicEnvelope::NS);
$data = $dom->createElementNS(MagicEnvelope::NS, 'me:data', $env['data']);
$data->setAttribute('type', $env['data_type']);
$prov->appendChild($data);
$enc = $dom->createElementNS(MagicEnvelope::NS, 'me:encoding', $env['encoding']);
$prov->appendChild($enc);
$alg = $dom->createElementNS(MagicEnvelope::NS, 'me:alg', $env['alg']);
$prov->appendChild($alg);
$sig = $dom->createElementNS(MagicEnvelope::NS, 'me:sig', $env['sig']);
$prov->appendChild($sig);
$dom->documentElement->appendChild($prov);
return $dom->saveXML();
}
/**
* Find the author URI referenced in the given Atom entry.
*
* @param string $text string containing Atom entry XML
* @return mixed URI string or false if XML parsing fails, or null if no author URI can be found
*
* @fixme XML parsing failures will spew to error logs/output
*/
public function getAuthorUri($text) {
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$doc = new DOMDocument();
if (!$doc->loadXML($text)) {
return FALSE;
}
if ($doc->documentElement->tagName == 'entry') {
$authors = $doc->documentElement->getElementsByTagName('author');
foreach ($authors as $author) {
$uris = $author->getElementsByTagName('uri');
foreach ($uris as $uri) {
return $uri->nodeValue;
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}
}
}
}
/**
* Attempt to verify cryptographic signing for parsed envelope data.
* Requires network access to retrieve public key referenced by the envelope signer.
*
* Details of failure conditions are dumped to output log and not exposed to caller.
*
* @param array $env array representation of magic envelope data, as returned from MagicEnvelope::parse()
* @return boolean
*
* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
*/
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public function verify($env)
{
if ($env['alg'] != 'RSA-SHA256') {
common_log(LOG_DEBUG, "Salmon error: bad algorithm");
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return false;
}
if ($env['encoding'] != MagicEnvelope::ENCODING) {
common_log(LOG_DEBUG, "Salmon error: bad encoding");
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return false;
}
$text = Magicsig::base64_url_decode($env['data']);
$signer_uri = $this->getAuthorUri($text);
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try {
$magicsig = $this->getKeyPair($signer_uri);
} catch (Exception $e) {
common_log(LOG_DEBUG, "Salmon error: ".$e->getMessage());
return false;
}
return $magicsig->verify($this->signingText($env), $env['sig']);
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}
/**
* Extract envelope data from an XML document containing an <me:env> or <me:provenance> element.
*
* @param string XML source
* @return mixed associative array of envelope data, or false on unrecognized input
*
* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
* @fixme will spew errors to logs or output in case of XML parse errors
* @fixme may give fatal errors if some elements are missing or invalid XML
* @fixme calling DOMDocument::loadXML statically triggers warnings in strict mode
*/
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public function parse($text)
{
$dom = DOMDocument::loadXML($text);
return $this->fromDom($dom);
}
/**
* Extract envelope data from an XML document containing an <me:env> or <me:provenance> element.
*
* @param DOMDocument $dom
* @return mixed associative array of envelope data, or false on unrecognized input
*
* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
* @fixme may give fatal errors if some elements are missing
*/
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public function fromDom($dom)
{
$env_element = $dom->getElementsByTagNameNS(MagicEnvelope::NS, 'env')->item(0);
if (!$env_element) {
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$env_element = $dom->getElementsByTagNameNS(MagicEnvelope::NS, 'provenance')->item(0);
}
if (!$env_element) {
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return false;
}
$data_element = $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'data')->item(0);
$sig_element = $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'sig')->item(0);
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return array(
'data' => preg_replace('/\s/', '', $data_element->nodeValue),
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'data_type' => $data_element->getAttribute('type'),
'encoding' => $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'encoding')->item(0)->nodeValue,
'alg' => $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'alg')->item(0)->nodeValue,
'sig' => preg_replace('/\s/', '', $sig_element->nodeValue),
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);
}
}