provide support for json-ld signatures (https://w3c-dvcg.github.io/ld-signatures/)

Zotlabs/Lib/LDSignatures.php

@@ -0,0 +1,81 @@
+<?php
+
+namespace Zotlabs\Lib;
+
+require_once('library/jsonld/jsonld.php');
+
+class LDSignatures {
+
+
+	static function verify($data,$pubkey) {
+
+		$ohash = self::hash(self::signable_options($data['signature']));
+		$dhash = self::hash(self::signable_data($data['signature']));
+
+		return rsa_verify($ohash . $dhash,base64_decode($data['signature']['signatureValue']), $pubkey);
+	}
+
+
+
+	static function sign($data,$channel) {
+		$options = [
+			'type' => 'RsaSignature2017',
+			'creator' => z_root() . '/channel/' . $channel['channel_address'] . '/public_key_pem',
+			'created' => datetime_convert('UTC','UTC', 'now', 'Y-m-d\Th:i:s\Z')
+		];
+
+		$ohash = self::hash(self::signable_options($options));
+		$dhash = self::hash(self::signable_data($data));
+		$options['signatureValue'] = base64_encode(rsa_sign($ohash . $dhash,$channel['channel_prvkey']));
+
+		$signed = array_merge([
+			'@context' => [ 'https://www.w3.org/ns/activitystreams', 'https://w3id.org/security/v1' ],
+			],$options);
+
+		return $signed;
+	}
+
+
+	static function signable_data($data) {
+
+		$newdata = [];
+		if($data) {
+			foreach($data as $k => $v) {
+				if(! in_array($k,[ 'signature' ])) {
+					$newopts[$k] = $v;
+				}
+			}
+		}
+		return json_encode($newdata,JSON_UNESCAPED_SLASHES);
+	}
+
+
+	static function signable_options($options) {
+
+		$newopts = [ '@context' => 'https://w3id.org/identity/v1' ];
+		if($options) {
+			foreach($options as $k => $v) {
+				if(! in_array($k,[ 'type','id','signatureValue' ])) {
+					$newopts[$k] = $v;
+				}
+			}
+		}
+		return json_encode($newopts,JSON_UNESCAPED_SLASHES);
+	}
+
+	static function hash($obj) {
+		return hash('sha256',self::normalise($obj));
+	}
+
+	static function normalise($data) {
+		if(is_string($data)) {
+			$data = json_decode($data);
+		}
+
+		if(! is_object($data))
+			return '';
+
+		return jsonld_normalize($data,[ 'algorithm' => 'URDNA2015', 'format' => 'application/nquads' ]);
+	}
+
+}