From 752b5fe28464c7f1dec79132b6ef74ae71420d8b Mon Sep 17 00:00:00 2001
From: Michael <heluecht@pirati.ca>
Date: Thu, 20 Sep 2018 21:45:23 +0000
Subject: [PATCH] Outgoing posts are now signed

---
 src/Protocol/ActivityPub.php | 22 +++++++--
 src/Util/LDSignature.php     | 92 ++++++++++++++++++++++++++++++++++++
 2 files changed, 109 insertions(+), 5 deletions(-)
 create mode 100644 src/Util/LDSignature.php

diff --git a/src/Protocol/ActivityPub.php b/src/Protocol/ActivityPub.php
index d952f4de8f..6f5fdedc95 100644
--- a/src/Protocol/ActivityPub.php
+++ b/src/Protocol/ActivityPub.php
@@ -20,6 +20,7 @@ use Friendica\Util\Crypto;
 use Friendica\Content\Text\BBCode;
 use Friendica\Content\Text\HTML;
 use Friendica\Util\JsonLD;
+use Friendica\Util\LDSignature;
 
 /**
  * @brief ActivityPub Protocol class
@@ -273,7 +274,10 @@ class ActivityPub
 		$data = array_merge($data, ActivityPub::createPermissionBlockForItem($item));
 
 		$data['object'] = self::createNote($item);
-		return $data;
+
+		$owner = User::getOwnerDataById($item['uid']);
+
+		return LDSignature::sign($data, $owner);
 	}
 
 	public static function createObjectFromItemID($item_id)
@@ -369,7 +373,9 @@ class ActivityPub
 			'to' => $profile['url']];
 
 		logger('Sending activity ' . $activity . ' to ' . $target . ' for user ' . $uid, LOGGER_DEBUG);
-		return HTTPSignature::transmit($data,  $profile['inbox'], $uid);
+
+		$signed = LDSignature::sign($data, $owner);
+		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
 	}
 
 	public static function transmitContactAccept($target, $id, $uid)
@@ -387,7 +393,9 @@ class ActivityPub
 			'to' => $profile['url']];
 
 		logger('Sending accept to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-		return HTTPSignature::transmit($data,  $profile['inbox'], $uid);
+
+		$signed = LDSignature::sign($data, $owner);
+		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
 	}
 
 	public static function transmitContactReject($target, $id, $uid)
@@ -405,7 +413,9 @@ class ActivityPub
 			'to' => $profile['url']];
 
 		logger('Sending reject to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-		return HTTPSignature::transmit($data,  $profile['inbox'], $uid);
+
+		$signed = LDSignature::sign($data, $owner);
+		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
 	}
 
 	public static function transmitContactUndo($target, $uid)
@@ -425,7 +435,9 @@ class ActivityPub
 			'to' => $profile['url']];
 
 		logger('Sending undo to ' . $target . ' for user ' . $uid . ' with id ' . $id, LOGGER_DEBUG);
-		return HTTPSignature::transmit($data,  $profile['inbox'], $uid);
+
+		$signed = LDSignature::sign($data, $owner);
+		return HTTPSignature::transmit($signed, $profile['inbox'], $uid);
 	}
 
 	/**
diff --git a/src/Util/LDSignature.php b/src/Util/LDSignature.php
new file mode 100644
index 0000000000..7288b584c7
--- /dev/null
+++ b/src/Util/LDSignature.php
@@ -0,0 +1,92 @@
+<?php
+
+namespace Friendica\Util;
+
+use Friendica\Util\JsonLD;
+use Friendica\Util\DateTimeFormat;
+use Friendica\Protocol\ActivityPub;
+
+class LDSignature
+{
+	public static function isSigned($data)
+	{
+		return !empty($data['signature']);
+	}
+
+	public static function isVerified($data, $pubkey = null)
+	{
+		if (!self::isSigned($data)) {
+			return false;
+		}
+
+		if (empty($pubkey)) {
+			$actor = JsonLD::fetchElement($data, 'actor', 'id');
+			if (empty($actor)) {
+				return false;
+			}
+
+			$profile = ActivityPub::fetchprofile($actor);
+			if (empty($profile['pubkey'])) {
+				return false;
+			}
+			$pubkey = $profile['pubkey'];
+		}
+
+		$ohash = self::hash(self::signable_options($data['signature']));
+		$dhash = self::hash(self::signable_data($data));
+
+		$x = Crypto::rsaVerify($ohash . $dhash, base64_decode($data['signature']['signatureValue']), $pubkey);
+		logger('LD-verify: ' . intval($x));
+
+		return $x;
+	}
+
+	public static function sign($data, $owner)
+	{
+		$options = [
+			'type' => 'RsaSignature2017',
+			'nonce' => random_string(64),
+			'creator' => $owner['url'] . '#main-key',
+			'created' => DateTimeFormat::utcNow()
+		];
+
+		$ohash = self::hash(self::signable_options($options));
+		$dhash = self::hash(self::signable_data($data));
+		$options['signatureValue'] = base64_encode(Crypto::rsaSign($ohash . $dhash, $owner['uprvkey']));
+
+		return array_merge($data, ['signature' => $options]);
+	}
+
+
+	private static function signable_data($data)
+	{
+		$newdata = [];
+		if (!empty($data)) {
+			foreach ($data as $k => $v) {
+				if (!in_array($k, ['signature'])) {
+					$newdata[$k] = $v;
+				}
+			}
+		}
+		return $newdata;
+	}
+
+
+	private static function signable_options($options)
+	{
+		$newopts = ['@context' => 'https://w3id.org/identity/v1'];
+		if (!empty($options)) {
+			foreach ($options as $k => $v) {
+				if (!in_array($k, ['type','id','signatureValue'])) {
+					$newopts[$k] = $v;
+				}
+			}
+		}
+		return $newopts;
+	}
+
+	private static function hash($obj)
+	{
+		return hash('sha256', JsonLD::normalize($obj));
+	}
+}