gnu-social/plugins/ActivityPub/lib/httpsignature.php

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<?php
/**
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* @category Network
* @package Nautilus
* @author Aaron Parecki <aaron@parecki.com>
* @license http://www.apache.org/licenses/LICENSE-2.0 Apache License 2.0
* @link https://github.com/aaronpk/Nautilus/blob/master/app/ActivityPub/HTTPSignature.php
*/
class HttpSignature
{
/**
* Sign a message with an Actor
*
* @param Profile $user Actor signing
* @param string $url Inbox url
* @param string|bool $body Data to sign (optional)
* @param array $addlHeaders Additional headers (optional)
* @return array Headers to be used in curl
* @throws Exception Attempted to sign something that belongs to an Actor we don't own
*/
public static function sign(Profile $user, string $url, $body = false, array $addlHeaders = []): array
{
$digest = false;
if ($body) {
$digest = self::_digest($body);
}
$headers = self::_headersToSign($url, $digest);
$headers = array_merge($headers, $addlHeaders);
$stringToSign = self::_headersToSigningString($headers);
$signedHeaders = implode(' ', array_map('strtolower', array_keys($headers)));
$actor_private_key = new Activitypub_rsa();
// Intentionally unhandled exception, we want this to explode if that happens as it would be a bug
$actor_private_key = $actor_private_key->get_private_key($user);
$key = openssl_pkey_get_private($actor_private_key);
openssl_sign($stringToSign, $signature, $key, OPENSSL_ALGO_SHA256);
$signature = base64_encode($signature);
$signatureHeader = 'keyId="' . $user->getUri() . '#public-key' . '",headers="' . $signedHeaders . '",algorithm="rsa-sha256",signature="' . $signature . '"';
unset($headers['(request-target)']);
$headers['Signature'] = $signatureHeader;
return self::_headersToCurlArray($headers);
}
/**
* @param mixed $body
* @return string
*/
private static function _digest($body): string
{
if (is_array($body)) {
$body = json_encode($body);
}
return base64_encode(hash('sha256', $body, true));
}
/**
* @param string $url
* @param mixed $digest
* @return array
* @throws Exception
*/
protected static function _headersToSign(string $url, $digest = false): array
{
$date = new DateTime('UTC');
$headers = [
'(request-target)' => 'post ' . parse_url($url, PHP_URL_PATH),
'Date' => $date->format('D, d M Y H:i:s \G\M\T'),
'Host' => parse_url($url, PHP_URL_HOST),
'Accept' => 'application/ld+json; profile="https://www.w3.org/ns/activitystreams", application/activity+json, application/json',
'User-Agent' => 'GNU social ActivityPub Plugin - '.GNUSOCIAL_ENGINE_URL,
'Content-Type' => 'application/activity+json'
];
if ($digest) {
$headers['Digest'] = 'SHA-256=' . $digest;
}
return $headers;
}
/**
* @param array $headers
* @return string
*/
private static function _headersToSigningString(array $headers): string
{
return implode("\n", array_map(function ($k, $v) {
return strtolower($k) . ': ' . $v;
}, array_keys($headers), $headers));
}
/**
* @param array $headers
* @return array
*/
private static function _headersToCurlArray(array $headers): array
{
return array_map(function ($k, $v) {
return "$k: $v";
}, array_keys($headers), $headers);
}
/**
* @param string $signature
* @return array
*/
public static function parseSignatureHeader(string $signature): array
{
$parts = explode(',', $signature);
$signatureData = [];
foreach ($parts as $part) {
if (preg_match('/(.+)="(.+)"/', $part, $match)) {
$signatureData[$match[1]] = $match[2];
}
}
if (!isset($signatureData['keyId'])) {
return [
'error' => 'No keyId was found in the signature header. Found: ' . implode(', ', array_keys($signatureData))
];
}
if (!filter_var($signatureData['keyId'], FILTER_VALIDATE_URL)) {
return [
'error' => 'keyId is not a URL: ' . $signatureData['keyId']
];
}
if (!isset($signatureData['headers']) || !isset($signatureData['signature'])) {
return [
'error' => 'Signature is missing headers or signature parts'
];
}
return $signatureData;
}
/**
* @param $publicKey
* @param $signatureData
* @param $inputHeaders
* @param $path
* @param $body
* @return array
*/
public static function verify($publicKey, $signatureData, $inputHeaders, $path, $body): array
{
$digest = 'SHA-256=' . base64_encode(hash('sha256', $body, true));
$headersToSign = [];
foreach (explode(' ', $signatureData['headers']) as $h) {
if ($h == '(request-target)') {
$headersToSign[$h] = 'post ' . $path;
} elseif ($h == 'digest') {
$headersToSign[$h] = $digest;
} elseif (isset($inputHeaders[$h][0])) {
$headersToSign[$h] = $inputHeaders[$h];
}
}
$signingString = self::_headersToSigningString($headersToSign);
$verified = openssl_verify($signingString, base64_decode($signatureData['signature']), $publicKey, OPENSSL_ALGO_SHA256);
return [$verified, $signingString];
}
}