From 100f102396beed2a218ca2f8ffaef392e94f4acc Mon Sep 17 00:00:00 2001
From: Daniel Supernault <danielsupernault@gmail.com>
Date: Sun, 16 Dec 2018 22:44:01 -0700
Subject: [PATCH] Add HttpSignature handlers

---
 app/Util/ActivityPub/HttpSignature.php | 121 +++++++++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 app/Util/ActivityPub/HttpSignature.php

diff --git a/app/Util/ActivityPub/HttpSignature.php b/app/Util/ActivityPub/HttpSignature.php
new file mode 100644
index 000000000..d4e4cbecd
--- /dev/null
+++ b/app/Util/ActivityPub/HttpSignature.php
@@ -0,0 +1,121 @@
+<?php
+
+namespace App\Util\ActivityPub;
+
+use Log;
+use App\Profile;
+use DateTime;
+
+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);
+  }
+
+  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', $body, true));
+  }
+
+  protected static function _headersToSign($url, $digest = false) {
+    $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),
+      'Content-Type' => 'application/activity+json',
+    ];
+
+    if($digest) {
+      $headers['Digest'] = 'SHA-256='.$digest;
+    }
+
+    return $headers;
+  }
+
+}