Outgoing posts are now signed

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));
+	}
+}