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pixelfed/app/Util/ActivityPub/HttpSignature.php

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<?php
namespace App\Util\ActivityPub;
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use Cache, Log;
use App\Models\InstanceActor;
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use App\Profile;
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use \DateTime;
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class HttpSignature {
/*
* source: https://github.com/aaronpk/Nautilus/blob/master/app/ActivityPub/HTTPSignature.php
* thanks aaronpk!
*/
public static function sign(Profile $profile, $url, $body = false, $addlHeaders = []) {
if($body) {
$digest = self::_digest($body);
}
$user = $profile;
$headers = self::_headersToSign($url, $body ? $digest : false);
$headers = array_merge($headers, $addlHeaders);
$stringToSign = self::_headersToSigningString($headers);
$signedHeaders = implode(' ', array_map('strtolower', array_keys($headers)));
$key = openssl_pkey_get_private($user->private_key);
openssl_sign($stringToSign, $signature, $key, OPENSSL_ALGO_SHA256);
$signature = base64_encode($signature);
$signatureHeader = 'keyId="'.$user->keyId().'",headers="'.$signedHeaders.'",algorithm="rsa-sha256",signature="'.$signature.'"';
unset($headers['(request-target)']);
$headers['Signature'] = $signatureHeader;
return self::_headersToCurlArray($headers);
}
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public static function instanceActorSign($url, $body = false, $addlHeaders = [], $method = 'post')
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{
$keyId = config('app.url') . '/i/actor#main-key';
$privateKey = Cache::rememberForever(InstanceActor::PKI_PRIVATE, function() {
return InstanceActor::first()->private_key;
});
if($body) {
$digest = self::_digest($body);
}
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$headers = self::_headersToSign($url, $body ? $digest : false, $method);
$headers = array_merge($headers, $addlHeaders);
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$stringToSign = self::_headersToSigningString($headers);
$signedHeaders = implode(' ', array_map('strtolower', array_keys($headers)));
$key = openssl_pkey_get_private($privateKey);
openssl_sign($stringToSign, $signature, $key, OPENSSL_ALGO_SHA256);
$signature = base64_encode($signature);
$signatureHeader = 'keyId="'.$keyId.'",headers="'.$signedHeaders.'",algorithm="rsa-sha256",signature="'.$signature.'"';
unset($headers['(request-target)']);
$headers['Signature'] = $signatureHeader;
return $headers;
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}
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public static function parseSignatureHeader($signature) {
$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 $signatureData;
}
public static function verify($publicKey, $signatureData, $inputHeaders, $path, $body) {
$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][0];
}
}
$signingString = self::_headersToSigningString($headersToSign);
$verified = openssl_verify($signingString, base64_decode($signatureData['signature']), $publicKey, OPENSSL_ALGO_SHA256);
return [$verified, $signingString];
}
private static function _headersToSigningString($headers) {
return implode("\n", array_map(function($k, $v){
return strtolower($k).': '.$v;
}, array_keys($headers), $headers));
}
private static function _headersToCurlArray($headers) {
return array_map(function($k, $v){
return "$k: $v";
}, array_keys($headers), $headers);
}
private static function _digest($body) {
if(is_array($body)) {
$body = json_encode($body);
}
return base64_encode(hash('sha256', $body, true));
}
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protected static function _headersToSign($url, $digest = false, $method = 'post') {
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$date = new DateTime('UTC');
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if(!in_array($method, ['post', 'get'])) {
throw new \Exception('Invalid method used to sign headers in HttpSignature');
}
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$headers = [
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'(request-target)' => $method . ' '.parse_url($url, PHP_URL_PATH),
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'Host' => parse_url($url, PHP_URL_HOST),
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'Date' => $date->format('D, d M Y H:i:s \G\M\T'),
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];
if($digest) {
$headers['Digest'] = 'SHA-256='.$digest;
}
return $headers;
}
}