327 lines
12 KiB
PHP
327 lines
12 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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protected $data = null; // When stored here it is _always_ base64url encoded
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protected $data_type = null;
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protected $encoding = null;
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protected $alg = null;
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protected $sig = null;
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/**
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* Extract envelope data from an XML document containing an <me:env> or <me:provenance> element.
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*
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* @param string XML source
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* @return mixed associative array of envelope data, or false on unrecognized input
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*
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* @fixme will spew errors to logs or output in case of XML parse errors
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* @fixme may give fatal errors if some elements are missing or invalid XML
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* @fixme calling DOMDocument::loadXML statically triggers warnings in strict mode
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*/
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public function __construct($xml=null) {
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if (!empty($xml)) {
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$dom = DOMDocument::loadXML($xml);
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if (!$dom instanceof DOMDocument) {
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throw new ServerException('Tried to load malformed XML as DOM');
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} elseif (!$this->fromDom($dom)) {
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throw new ServerException('Could not load MagicEnvelope from DOM');
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}
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}
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}
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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 $magicsig;
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}
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/**
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* The current MagicEnvelope spec as used in StatusNet 0.9.7 and later
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* includes both the original data and some signing metadata fields as
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* the input plaintext for the signature hash.
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*
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* @return string
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*/
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public function signingText() {
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return implode('.', array($this->data, // this field is pre-base64'd
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Magicsig::base64_url_encode($this->data_type),
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Magicsig::base64_url_encode($this->encoding),
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Magicsig::base64_url_encode($this->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 Magicsig $magicsig Magicsig with private key available.
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* @return MagicEnvelope object with all properties set
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*/
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public static function signMessage($text, $mimetype, Magicsig $magicsig)
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{
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$magic_env = new MagicEnvelope();
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// Prepare text and metadata for signing
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$magic_env->data = Magicsig::base64_url_encode($text);
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$magic_env->data_type = $mimetype;
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$magic_env->encoding = self::ENCODING;
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$magic_env->alg = $magicsig->getName();
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// Get the actual signature
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$magic_env->sig = $magicsig->sign($magic_env->signingText());
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return $magic_env;
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}
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/**
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* Create an <me:env> XML representation of the envelope.
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*
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* @return string representation of XML document
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*/
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public function toXML() {
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$xs = new XMLStringer();
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$xs->startXML();
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$xs->elementStart('me:env', array('xmlns:me' => self::NS));
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$xs->element('me:data', array('type' => $this->data_type), $this->data);
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$xs->element('me:encoding', null, $this->encoding);
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$xs->element('me:alg', null, $this->alg);
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$xs->element('me:sig', null, $this->sig);
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$xs->elementEnd('me:env');
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$string = $xs->getString();
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common_debug('MagicEnvelope XML: ' . $string);
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return $string;
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}
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/**
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* Extract the contained XML payload, and insert a copy of the envelope
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* signature data as an <me:provenance> section.
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*
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* @return string representation of modified XML document
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*
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* @fixme in case of XML parsing errors, this will spew to the error log or output
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*/
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public function unfold()
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{
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$dom = new DOMDocument();
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$dom->loadXML(Magicsig::base64_url_decode($this->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 = $dom->createElementNS(self::NS, 'me:provenance');
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$prov->setAttribute('xmlns:me', self::NS);
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$data = $dom->createElementNS(self::NS, 'me:data', $this->data);
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$data->setAttribute('type', $this->data_type);
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$prov->appendChild($data);
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$enc = $dom->createElementNS(self::NS, 'me:encoding', $this->encoding);
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$prov->appendChild($enc);
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$alg = $dom->createElementNS(self::NS, 'me:alg', $this->alg);
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$prov->appendChild($alg);
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$sig = $dom->createElementNS(self::NS, 'me:sig', $this->sig);
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$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 $uri->nodeValue;
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}
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}
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}
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}
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/**
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* Attempt to verify cryptographic signing for parsed envelope data.
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* Requires network access to retrieve public key referenced by the envelope signer.
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*
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* Details of failure conditions are dumped to output log and not exposed to caller.
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*
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* @return boolean
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*/
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public function verify()
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{
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if ($this->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 ($this->encoding != self::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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// $this->data is base64_url_encoded and should contain XML which is passed to getAuthorUri
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$text = Magicsig::base64_url_decode($this->data);
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$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(), $this->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 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 may give fatal errors if some elements are missing
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*/
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protected function fromDom(DOMDocument $dom)
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{
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$env_element = $dom->getElementsByTagNameNS(self::NS, 'env')->item(0);
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if (!$env_element) {
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$env_element = $dom->getElementsByTagNameNS(self::NS, 'provenance')->item(0);
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}
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if (!$env_element) {
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return false;
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}
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$data_element = $env_element->getElementsByTagNameNS(self::NS, 'data')->item(0);
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$sig_element = $env_element->getElementsByTagNameNS(self::NS, 'sig')->item(0);
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$this->data = preg_replace('/\s/', '', $data_element->nodeValue);
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$this->data_type = $data_element->getAttribute('type');
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$this->encoding = $env_element->getElementsByTagNameNS(self::NS, 'encoding')->item(0)->nodeValue;
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$this->alg = $env_element->getElementsByTagNameNS(self::NS, 'alg')->item(0)->nodeValue;
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$this->sig = preg_replace('/\s/', '', $sig_element->nodeValue);
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return true;
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}
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/**
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* Encode the given string as a signed MagicEnvelope XML document,
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* using the keypair for the given local user profile. We can of
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* course not sign a remote profile's slap, since we don't have the
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* private key.
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*
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* Side effects: will create and store a keypair on-demand if one
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* hasn't already been generated for this user. This can be very slow
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* on some systems.
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*
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* @param string $text XML fragment to sign, assumed to be Atom
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* @param Profile $actor Profile of a local user to use as signer
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*
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* @return string XML string representation of magic envelope
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*
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* @throws Exception on bad profile input or key generation problems
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* @fixme if signing fails, this seems to return the original text without warning. Is there a reason for this?
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*/
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public static function signForProfile($text, Profile $actor)
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{
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// We only generate keys for our local users of course, so let
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// getUser throw an exception if the profile is not local.
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$user = $actor->getUser();
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// Find already stored key
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$magicsig = Magicsig::getKV('user_id', $user->id);
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if (!$magicsig instanceof Magicsig) {
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// No keypair yet, let's generate one.
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$magicsig = new Magicsig();
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$magicsig->generate($user->id);
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}
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$magic_env = self::signMessage($text, 'application/atom+xml', $magicsig);
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assert($magicenv instanceof MagicEnvelope);
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return $magic_env;
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}
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}
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