309 lines
11 KiB
PHP
309 lines
11 KiB
PHP
<?php
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/**
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* StatusNet - the distributed open-source microblogging tool
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* Copyright (C) 2010, StatusNet, Inc.
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*
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* A sample module to show best practices for StatusNet plugins
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*
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* PHP version 5
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* @package StatusNet
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* @author James Walker <james@status.net>
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* @copyright 2010 StatusNet, Inc.
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* @license http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
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* @link http://status.net/
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*/
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class MagicEnvelope
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{
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const ENCODING = 'base64url';
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const NS = 'http://salmon-protocol.org/ns/magic-env';
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/**
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* Get the Salmon keypair from a URI, uses XRD Discovery etc.
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*
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* @return Magicsig with loaded keypair
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*/
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public function getKeyPair($signer_uri)
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{
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$disco = new Discovery();
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// Throws exception on lookup problems
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$xrd = $disco->lookup($signer_uri);
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$link = $xrd->get(Magicsig::PUBLICKEYREL);
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if (is_null($link)) {
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// TRANS: Exception.
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throw new Exception(_m('Unable to locate signer public key.'));
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}
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// We have a public key element, let's hope it has proper key data.
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$keypair = false;
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$parts = explode(',', $link->href);
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if (count($parts) == 2) {
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$keypair = $parts[1];
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} else {
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// Backwards compatibility check for separator bug in 0.9.0
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$parts = explode(';', $link->href);
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if (count($parts) == 2) {
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$keypair = $parts[1];
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}
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}
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if ($keypair === false) {
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// For debugging clarity. Keypair did not pass count()-check above.
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// TRANS: Exception when public key was not properly formatted.
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throw new Exception(_m('Incorrectly formatted public key element.'));
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}
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$magicsig = Magicsig::fromString($keypair);
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if (!$magicsig instanceof Magicsig) {
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common_debug('Salmon error: unable to parse keypair: '.var_export($keypair,true));
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// TRANS: Exception when public key was properly formatted but not parsable.
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throw new ServerException(_m('Retrieved Salmon keypair could not be parsed.'));
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}
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return $magicsig;
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}
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/**
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* The current MagicEnvelope spec as used in StatusNet 0.9.7 and later
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* includes both the original data and some signing metadata fields as
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* the input plaintext for the signature hash.
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*
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* @param array $env
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* @return string
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*/
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public function signingText($env) {
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return implode('.', array($env['data'], // this field is pre-base64'd
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Magicsig::base64_url_encode($env['data_type']),
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Magicsig::base64_url_encode($env['encoding']),
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Magicsig::base64_url_encode($env['alg'])));
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}
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/**
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*
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* @param <type> $text
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* @param <type> $mimetype
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* @param <type> $keypair
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* @return array: associative array of envelope properties
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* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
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*/
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public function signMessage($text, $mimetype, $keypair)
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{
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$signature_alg = Magicsig::fromString($keypair);
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$armored_text = Magicsig::base64_url_encode($text);
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$env = array(
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'data' => $armored_text,
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'encoding' => MagicEnvelope::ENCODING,
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'data_type' => $mimetype,
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'sig' => '',
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'alg' => $signature_alg->getName()
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);
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$env['sig'] = $signature_alg->sign($this->signingText($env));
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return $env;
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}
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/**
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* Create an <me:env> XML representation of the envelope.
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*
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* @param array $env associative array with envelope data
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* @return string representation of XML document
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* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
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*/
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public function toXML($env) {
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$xs = new XMLStringer();
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$xs->startXML();
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$xs->elementStart('me:env', array('xmlns:me' => MagicEnvelope::NS));
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$xs->element('me:data', array('type' => $env['data_type']), $env['data']);
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$xs->element('me:encoding', null, $env['encoding']);
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$xs->element('me:alg', null, $env['alg']);
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$xs->element('me:sig', null, $env['sig']);
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$xs->elementEnd('me:env');
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$string = $xs->getString();
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common_debug($string);
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return $string;
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}
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/**
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* Extract the contained XML payload, and insert a copy of the envelope
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* signature data as an <me:provenance> section.
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*
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* @param array $env associative array with envelope data
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* @return string representation of modified XML document
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*
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* @fixme in case of XML parsing errors, this will spew to the error log or output
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* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
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*/
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public function unfold($env)
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{
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$dom = new DOMDocument();
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$dom->loadXML(Magicsig::base64_url_decode($env['data']));
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if ($dom->documentElement->tagName != 'entry') {
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return false;
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}
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$prov = $dom->createElementNS(MagicEnvelope::NS, 'me:provenance');
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$prov->setAttribute('xmlns:me', MagicEnvelope::NS);
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$data = $dom->createElementNS(MagicEnvelope::NS, 'me:data', $env['data']);
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$data->setAttribute('type', $env['data_type']);
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$prov->appendChild($data);
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$enc = $dom->createElementNS(MagicEnvelope::NS, 'me:encoding', $env['encoding']);
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$prov->appendChild($enc);
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$alg = $dom->createElementNS(MagicEnvelope::NS, 'me:alg', $env['alg']);
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$prov->appendChild($alg);
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$sig = $dom->createElementNS(MagicEnvelope::NS, 'me:sig', $env['sig']);
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$prov->appendChild($sig);
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$dom->documentElement->appendChild($prov);
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return $dom->saveXML();
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}
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/**
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* Find the author URI referenced in the given Atom entry.
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*
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* @param string $text string containing Atom entry XML
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* @return mixed URI string or false if XML parsing fails, or null if no author URI can be found
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*
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* @fixme XML parsing failures will spew to error logs/output
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*/
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public function getAuthorUri($text) {
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$doc = new DOMDocument();
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if (!$doc->loadXML($text)) {
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return FALSE;
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}
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if ($doc->documentElement->tagName == 'entry') {
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$authors = $doc->documentElement->getElementsByTagName('author');
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foreach ($authors as $author) {
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$uris = $author->getElementsByTagName('uri');
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foreach ($uris as $uri) {
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return $uri->nodeValue;
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}
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}
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}
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}
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/**
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* Attempt to verify cryptographic signing for parsed envelope data.
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* Requires network access to retrieve public key referenced by the envelope signer.
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*
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* Details of failure conditions are dumped to output log and not exposed to caller.
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*
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* @param array $env array representation of magic envelope data, as returned from MagicEnvelope::parse()
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* @return boolean
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*
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* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
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*/
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public function verify($env)
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{
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if ($env['alg'] != 'RSA-SHA256') {
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common_log(LOG_DEBUG, "Salmon error: bad algorithm");
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return false;
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}
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if ($env['encoding'] != MagicEnvelope::ENCODING) {
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common_log(LOG_DEBUG, "Salmon error: bad encoding");
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return false;
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}
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$text = Magicsig::base64_url_decode($env['data']);
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$signer_uri = $this->getAuthorUri($text);
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try {
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$magicsig = $this->getKeyPair($signer_uri);
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} catch (Exception $e) {
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common_log(LOG_DEBUG, "Salmon error: ".$e->getMessage());
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return false;
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}
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return $magicsig->verify($this->signingText($env), $env['sig']);
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}
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/**
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* Extract envelope data from an XML document containing an <me:env> or <me:provenance> element.
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*
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* @param string XML source
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* @return mixed associative array of envelope data, or false on unrecognized input
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*
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* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
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* @fixme will spew errors to logs or output in case of XML parse errors
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* @fixme may give fatal errors if some elements are missing or invalid XML
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* @fixme calling DOMDocument::loadXML statically triggers warnings in strict mode
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*/
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public function parse($text)
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{
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$dom = DOMDocument::loadXML($text);
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return $this->fromDom($dom);
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}
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/**
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* Extract envelope data from an XML document containing an <me:env> or <me:provenance> element.
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*
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* @param DOMDocument $dom
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* @return mixed associative array of envelope data, or false on unrecognized input
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*
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* @fixme it might be easier to work with storing envelope data these in the object instead of passing arrays around
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* @fixme may give fatal errors if some elements are missing
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*/
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public function fromDom($dom)
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{
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$env_element = $dom->getElementsByTagNameNS(MagicEnvelope::NS, 'env')->item(0);
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if (!$env_element) {
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$env_element = $dom->getElementsByTagNameNS(MagicEnvelope::NS, 'provenance')->item(0);
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}
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if (!$env_element) {
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return false;
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}
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$data_element = $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'data')->item(0);
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$sig_element = $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'sig')->item(0);
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return array(
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'data' => preg_replace('/\s/', '', $data_element->nodeValue),
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'data_type' => $data_element->getAttribute('type'),
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'encoding' => $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'encoding')->item(0)->nodeValue,
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'alg' => $env_element->getElementsByTagNameNS(MagicEnvelope::NS, 'alg')->item(0)->nodeValue,
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'sig' => preg_replace('/\s/', '', $sig_element->nodeValue),
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);
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}
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}
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/**
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* Variant of MagicEnvelope using the earlier signature form listed in the MagicEnvelope
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* spec in early 2010; this was used in StatusNet up through 0.9.6, so for backwards compatiblity
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* we still need to accept and sometimes send this format.
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*/
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class MagicEnvelopeCompat extends MagicEnvelope {
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/**
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* StatusNet through 0.9.6 used an earlier version of the MagicEnvelope spec
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* which used only the input data, without the additional fields, as the plaintext
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* for signing.
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*
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* @param array $env
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* @return string
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*/
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public function signingText($env) {
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return $env['data'];
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}
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}
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