Merge pull request #444 from nextcloud/backport/433/alpha1alpha1

[alpha1] create object even if it can't be signed

5 files changed, 128 insertions, 4 deletions

diff --git a/context/w3id.org.identity.v1.json b/context/w3id.org.identity.v1.json
new file mode 100644
index 00000000..fcb38e57
--- /dev/null
+++ b/context/w3id.org.identity.v1.json
@@ -0,0 +1 @@
+{"contextUrl":null,"document":"{\n  \"@context\": {\n    \"id\": \"@id\",\n    \"type\": \"@type\",\n\n    \"cred\": \"https:\/\/w3id.org\/credentials#\",\n    \"dc\": \"http:\/\/purl.org\/dc\/terms\/\",\n    \"identity\": \"https:\/\/w3id.org\/identity#\",\n    \"perm\": \"https:\/\/w3id.org\/permissions#\",\n    \"ps\": \"https:\/\/w3id.org\/payswarm#\",\n    \"rdf\": \"http:\/\/www.w3.org\/1999\/02\/22-rdf-syntax-ns#\",\n    \"rdfs\": \"http:\/\/www.w3.org\/2000\/01\/rdf-schema#\",\n    \"sec\": \"https:\/\/w3id.org\/security#\",\n    \"schema\": \"http:\/\/schema.org\/\",\n    \"xsd\": \"http:\/\/www.w3.org\/2001\/XMLSchema#\",\n\n    \"Group\": \"https:\/\/www.w3.org\/ns\/activitystreams#Group\",\n\n    \"claim\": {\"@id\": \"cred:claim\", \"@type\": \"@id\"},\n    \"credential\": {\"@id\": \"cred:credential\", \"@type\": \"@id\"},\n    \"issued\": {\"@id\": \"cred:issued\", \"@type\": \"xsd:dateTime\"},\n    \"issuer\": {\"@id\": \"cred:issuer\", \"@type\": \"@id\"},\n    \"recipient\": {\"@id\": \"cred:recipient\", \"@type\": \"@id\"},\n    \"Credential\": \"cred:Credential\",\n    \"CryptographicKeyCredential\": \"cred:CryptographicKeyCredential\",\n\n    \"about\": {\"@id\": \"schema:about\", \"@type\": \"@id\"},\n    \"address\": {\"@id\": \"schema:address\", \"@type\": \"@id\"},\n    \"addressCountry\": \"schema:addressCountry\",\n    \"addressLocality\": \"schema:addressLocality\",\n    \"addressRegion\": \"schema:addressRegion\",\n    \"comment\": \"rdfs:comment\",\n    \"created\": {\"@id\": \"dc:created\", \"@type\": \"xsd:dateTime\"},\n    \"creator\": {\"@id\": \"dc:creator\", \"@type\": \"@id\"},\n    \"description\": \"schema:description\",\n    \"email\": \"schema:email\",\n    \"familyName\": \"schema:familyName\",\n    \"givenName\": \"schema:givenName\",\n    \"image\": {\"@id\": \"schema:image\", \"@type\": \"@id\"},\n    \"label\": \"rdfs:label\",\n    \"name\": \"schema:name\",\n    \"postalCode\": \"schema:postalCode\",\n    \"streetAddress\": \"schema:streetAddress\",\n    \"title\": \"dc:title\",\n    \"url\": {\"@id\": \"schema:url\", \"@type\": \"@id\"},\n    \"Person\": \"schema:Person\",\n    \"PostalAddress\": \"schema:PostalAddress\",\n    \"Organization\": \"schema:Organization\",\n\n    \"identityService\": {\"@id\": \"identity:identityService\", \"@type\": \"@id\"},\n    \"idp\": {\"@id\": \"identity:idp\", \"@type\": \"@id\"},\n    \"Identity\": \"identity:Identity\",\n\n    \"paymentProcessor\": \"ps:processor\",\n    \"preferences\": {\"@id\": \"ps:preferences\", \"@type\": \"@vocab\"},\n\n    \"cipherAlgorithm\": \"sec:cipherAlgorithm\",\n    \"cipherData\": \"sec:cipherData\",\n    \"cipherKey\": \"sec:cipherKey\",\n    \"digestAlgorithm\": \"sec:digestAlgorithm\",\n    \"digestValue\": \"sec:digestValue\",\n    \"domain\": \"sec:domain\",\n    \"expires\": {\"@id\": \"sec:expiration\", \"@type\": \"xsd:dateTime\"},\n    \"initializationVector\": \"sec:initializationVector\",\n    \"member\": {\"@id\": \"schema:member\", \"@type\": \"@id\"},\n    \"memberOf\": {\"@id\": \"schema:memberOf\", \"@type\": \"@id\"},\n    \"nonce\": \"sec:nonce\",\n    \"normalizationAlgorithm\": \"sec:normalizationAlgorithm\",\n    \"owner\": {\"@id\": \"sec:owner\", \"@type\": \"@id\"},\n    \"password\": \"sec:password\",\n    \"privateKey\": {\"@id\": \"sec:privateKey\", \"@type\": \"@id\"},\n    \"privateKeyPem\": \"sec:privateKeyPem\",\n    \"publicKey\": {\"@id\": \"sec:publicKey\", \"@type\": \"@id\"},\n    \"publicKeyPem\": \"sec:publicKeyPem\",\n    \"publicKeyService\": {\"@id\": \"sec:publicKeyService\", \"@type\": \"@id\"},\n    \"revoked\": {\"@id\": \"sec:revoked\", \"@type\": \"xsd:dateTime\"},\n    \"signature\": \"sec:signature\",\n    \"signatureAlgorithm\": \"sec:signatureAlgorithm\",\n    \"signatureValue\": \"sec:signatureValue\",\n    \"CryptographicKey\": \"sec:Key\",\n    \"EncryptedMessage\": \"sec:EncryptedMessage\",\n    \"GraphSignature2012\": \"sec:GraphSignature2012\",\n    \"LinkedDataSignature2015\": \"sec:LinkedDataSignature2015\",\n\n    \"accessControl\": {\"@id\": \"perm:accessControl\", \"@type\": \"@id\"},\n    \"writePermission\": {\"@id\": \"perm:writePermission\", \"@type\": \"@id\"}\n  }\n}\n","documentUrl":"https:\/\/web-payments.org\/contexts\/identity-v1.jsonld"}
\ No newline at end of file
diff --git a/context/w3id.org.security.v1.json b/context/w3id.org.security.v1.json
new file mode 100644
index 00000000..e3a0825b
--- /dev/null
+++ b/context/w3id.org.security.v1.json
@@ -0,0 +1 @@
+{"contextUrl":null,"document":"{\n  \"@context\": {\n    \"id\": \"@id\",\n    \"type\": \"@type\",\n\n    \"dc\": \"http:\/\/purl.org\/dc\/terms\/\",\n    \"sec\": \"https:\/\/w3id.org\/security#\",\n    \"xsd\": \"http:\/\/www.w3.org\/2001\/XMLSchema#\",\n\n    \"EcdsaKoblitzSignature2016\": \"sec:EcdsaKoblitzSignature2016\",\n    \"Ed25519Signature2018\": \"sec:Ed25519Signature2018\",\n    \"EncryptedMessage\": \"sec:EncryptedMessage\",\n    \"GraphSignature2012\": \"sec:GraphSignature2012\",\n    \"LinkedDataSignature2015\": \"sec:LinkedDataSignature2015\",\n    \"LinkedDataSignature2016\": \"sec:LinkedDataSignature2016\",\n    \"CryptographicKey\": \"sec:Key\",\n\n    \"authenticationTag\": \"sec:authenticationTag\",\n    \"canonicalizationAlgorithm\": \"sec:canonicalizationAlgorithm\",\n    \"cipherAlgorithm\": \"sec:cipherAlgorithm\",\n    \"cipherData\": \"sec:cipherData\",\n    \"cipherKey\": \"sec:cipherKey\",\n    \"created\": {\"@id\": \"dc:created\", \"@type\": \"xsd:dateTime\"},\n    \"creator\": {\"@id\": \"dc:creator\", \"@type\": \"@id\"},\n    \"digestAlgorithm\": \"sec:digestAlgorithm\",\n    \"digestValue\": \"sec:digestValue\",\n    \"domain\": \"sec:domain\",\n    \"encryptionKey\": \"sec:encryptionKey\",\n    \"expiration\": {\"@id\": \"sec:expiration\", \"@type\": \"xsd:dateTime\"},\n    \"expires\": {\"@id\": \"sec:expiration\", \"@type\": \"xsd:dateTime\"},\n    \"initializationVector\": \"sec:initializationVector\",\n    \"iterationCount\": \"sec:iterationCount\",\n    \"nonce\": \"sec:nonce\",\n    \"normalizationAlgorithm\": \"sec:normalizationAlgorithm\",\n    \"owner\": {\"@id\": \"sec:owner\", \"@type\": \"@id\"},\n    \"password\": \"sec:password\",\n    \"privateKey\": {\"@id\": \"sec:privateKey\", \"@type\": \"@id\"},\n    \"privateKeyPem\": \"sec:privateKeyPem\",\n    \"publicKey\": {\"@id\": \"sec:publicKey\", \"@type\": \"@id\"},\n    \"publicKeyBase58\": \"sec:publicKeyBase58\",\n    \"publicKeyPem\": \"sec:publicKeyPem\",\n    \"publicKeyWif\": \"sec:publicKeyWif\",\n    \"publicKeyService\": {\"@id\": \"sec:publicKeyService\", \"@type\": \"@id\"},\n    \"revoked\": {\"@id\": \"sec:revoked\", \"@type\": \"xsd:dateTime\"},\n    \"salt\": \"sec:salt\",\n    \"signature\": \"sec:signature\",\n    \"signatureAlgorithm\": \"sec:signingAlgorithm\",\n    \"signatureValue\": \"sec:signatureValue\"\n  }\n}\n","documentUrl":"https:\/\/web-payments.org\/contexts\/security-v1.jsonld"}
\ No newline at end of file
diff --git a/context/www.w3.org.ns.activitystreams.json b/context/www.w3.org.ns.activitystreams.json
new file mode 100644
index 00000000..659708ff
--- /dev/null
+++ b/context/www.w3.org.ns.activitystreams.json
@@ -0,0 +1 @@
+{"contextUrl":null,"document":"{\n  \"@context\": {\n    \"@vocab\": \"_:\",\n    \"xsd\": \"http:\/\/www.w3.org\/2001\/XMLSchema#\",\n    \"as\": \"https:\/\/www.w3.org\/ns\/activitystreams#\",\n    \"ldp\": \"http:\/\/www.w3.org\/ns\/ldp#\",\n    \"id\": \"@id\",\n    \"type\": \"@type\",\n    \"Accept\": \"as:Accept\",\n    \"Activity\": \"as:Activity\",\n    \"IntransitiveActivity\": \"as:IntransitiveActivity\",\n    \"Add\": \"as:Add\",\n    \"Announce\": \"as:Announce\",\n    \"Application\": \"as:Application\",\n    \"Arrive\": \"as:Arrive\",\n    \"Article\": \"as:Article\",\n    \"Audio\": \"as:Audio\",\n    \"Block\": \"as:Block\",\n    \"Collection\": \"as:Collection\",\n    \"CollectionPage\": \"as:CollectionPage\",\n    \"Relationship\": \"as:Relationship\",\n    \"Create\": \"as:Create\",\n    \"Delete\": \"as:Delete\",\n    \"Dislike\": \"as:Dislike\",\n    \"Document\": \"as:Document\",\n    \"Event\": \"as:Event\",\n    \"Follow\": \"as:Follow\",\n    \"Flag\": \"as:Flag\",\n    \"Group\": \"as:Group\",\n    \"Ignore\": \"as:Ignore\",\n    \"Image\": \"as:Image\",\n    \"Invite\": \"as:Invite\",\n    \"Join\": \"as:Join\",\n    \"Leave\": \"as:Leave\",\n    \"Like\": \"as:Like\",\n    \"Link\": \"as:Link\",\n    \"Mention\": \"as:Mention\",\n    \"Note\": \"as:Note\",\n    \"Object\": \"as:Object\",\n    \"Offer\": \"as:Offer\",\n    \"OrderedCollection\": \"as:OrderedCollection\",\n    \"OrderedCollectionPage\": \"as:OrderedCollectionPage\",\n    \"Organization\": \"as:Organization\",\n    \"Page\": \"as:Page\",\n    \"Person\": \"as:Person\",\n    \"Place\": \"as:Place\",\n    \"Profile\": \"as:Profile\",\n    \"Question\": \"as:Question\",\n    \"Reject\": \"as:Reject\",\n    \"Remove\": \"as:Remove\",\n    \"Service\": \"as:Service\",\n    \"TentativeAccept\": \"as:TentativeAccept\",\n    \"TentativeReject\": \"as:TentativeReject\",\n    \"Tombstone\": \"as:Tombstone\",\n    \"Undo\": \"as:Undo\",\n    \"Update\": \"as:Update\",\n    \"Video\": \"as:Video\",\n    \"View\": \"as:View\",\n    \"Listen\": \"as:Listen\",\n    \"Read\": \"as:Read\",\n    \"Move\": \"as:Move\",\n    \"Travel\": \"as:Travel\",\n    \"IsFollowing\": \"as:IsFollowing\",\n    \"IsFollowedBy\": \"as:IsFollowedBy\",\n    \"IsContact\": \"as:IsContact\",\n    \"IsMember\": \"as:IsMember\",\n    \"subject\": {\n      \"@id\": \"as:subject\",\n      \"@type\": \"@id\"\n    },\n    \"relationship\": {\n      \"@id\": \"as:relationship\",\n      \"@type\": \"@id\"\n    },\n    \"actor\": {\n      \"@id\": \"as:actor\",\n      \"@type\": \"@id\"\n    },\n    \"attributedTo\": {\n      \"@id\": \"as:attributedTo\",\n      \"@type\": \"@id\"\n    },\n    \"attachment\": {\n      \"@id\": \"as:attachment\",\n      \"@type\": \"@id\"\n    },\n    \"bcc\": {\n      \"@id\": \"as:bcc\",\n      \"@type\": \"@id\"\n    },\n    \"bto\": {\n      \"@id\": \"as:bto\",\n      \"@type\": \"@id\"\n    },\n    \"cc\": {\n      \"@id\": \"as:cc\",\n      \"@type\": \"@id\"\n    },\n    \"context\": {\n      \"@id\": \"as:context\",\n      \"@type\": \"@id\"\n    },\n    \"current\": {\n      \"@id\": \"as:current\",\n      \"@type\": \"@id\"\n    },\n    \"first\": {\n      \"@id\": \"as:first\",\n      \"@type\": \"@id\"\n    },\n    \"generator\": {\n      \"@id\": \"as:generator\",\n      \"@type\": \"@id\"\n    },\n    \"icon\": {\n      \"@id\": \"as:icon\",\n      \"@type\": \"@id\"\n    },\n    \"image\": {\n      \"@id\": \"as:image\",\n      \"@type\": \"@id\"\n    },\n    \"inReplyTo\": {\n      \"@id\": \"as:inReplyTo\",\n      \"@type\": \"@id\"\n    },\n    \"items\": {\n      \"@id\": \"as:items\",\n      \"@type\": \"@id\"\n    },\n    \"instrument\": {\n      \"@id\": \"as:instrument\",\n      \"@type\": \"@id\"\n    },\n    \"orderedItems\": {\n      \"@id\": \"as:items\",\n      \"@type\": \"@id\",\n      \"@container\": \"@list\"\n    },\n    \"last\": {\n      \"@id\": \"as:last\",\n      \"@type\": \"@id\"\n    },\n    \"location\": {\n      \"@id\": \"as:location\",\n      \"@type\": \"@id\"\n    },\n    \"next\": {\n      \"@id\": \"as:next\",\n      \"@type\": \"@id\"\n    },\n    \"object\": {\n      \"@id\": \"as:object\",\n      \"@type\": \"@id\"\n    },\n    \"oneOf\": {\n      \"@id\": \"as:oneOf\",\n      \"@type\": \"@id\"\n    },\n    \"anyOf\": {\n      \"@id\": \"as:anyOf\",\n      \"@type\": \"@id\"\n    },\n    \"closed\": {\n      \"@id\": \"as:closed\",\n      \"@type\": \"xsd:dateTime\"\n    },\n    \"origin\": {\n      \"@id\": \"as:origin\",\n      \"@type\": \"@id\"\n    },\n    \"accuracy\": {\n      \"@id\": \"as:accuracy\",\n      \"@type\": \"xsd:float\"\n    },\n    \"prev\": {\n      \"@id\": \"as:prev\",\n      \"@type\": \"@id\"\n    },\n    \"preview\": {\n      \"@id\": \"as:preview\",\n      \"@type\": \"@id\"\n    },\n    \"replies\": {\n      \"@id\": \"as:replies\",\n      \"@type\": \"@id\"\n    },\n    \"result\": {\n      \"@id\": \"as:result\",\n      \"@type\": \"@id\"\n    },\n    \"audience\": {\n      \"@id\": \"as:audience\",\n      \"@type\": \"@id\"\n    },\n    \"partOf\": {\n      \"@id\": \"as:partOf\",\n      \"@type\": \"@id\"\n    },\n    \"tag\": {\n      \"@id\": \"as:tag\",\n      \"@type\": \"@id\"\n    },\n    \"target\": {\n      \"@id\": \"as:target\",\n      \"@type\": \"@id\"\n    },\n    \"to\": {\n      \"@id\": \"as:to\",\n      \"@type\": \"@id\"\n    },\n    \"url\": {\n      \"@id\": \"as:url\",\n      \"@type\": \"@id\"\n    },\n    \"altitude\": {\n      \"@id\": \"as:altitude\",\n      \"@type\": \"xsd:float\"\n    },\n    \"content\": \"as:content\",\n    \"contentMap\": {\n      \"@id\": \"as:content\",\n      \"@container\": \"@language\"\n    },\n    \"name\": \"as:name\",\n    \"nameMap\": {\n      \"@id\": \"as:name\",\n      \"@container\": \"@language\"\n    },\n    \"duration\": {\n      \"@id\": \"as:duration\",\n      \"@type\": \"xsd:duration\"\n    },\n    \"endTime\": {\n      \"@id\": \"as:endTime\",\n      \"@type\": \"xsd:dateTime\"\n    },\n    \"height\": {\n      \"@id\": \"as:height\",\n      \"@type\": \"xsd:nonNegativeInteger\"\n    },\n    \"href\": {\n      \"@id\": \"as:href\",\n      \"@type\": \"@id\"\n    },\n    \"hreflang\": \"as:hreflang\",\n    \"latitude\": {\n      \"@id\": \"as:latitude\",\n      \"@type\": \"xsd:float\"\n    },\n    \"longitude\": {\n      \"@id\": \"as:longitude\",\n      \"@type\": \"xsd:float\"\n    },\n    \"mediaType\": \"as:mediaType\",\n    \"published\": {\n      \"@id\": \"as:published\",\n      \"@type\": \"xsd:dateTime\"\n    },\n    \"radius\": {\n      \"@id\": \"as:radius\",\n      \"@type\": \"xsd:float\"\n    },\n    \"rel\": \"as:rel\",\n    \"startIndex\": {\n      \"@id\": \"as:startIndex\",\n      \"@type\": \"xsd:nonNegativeInteger\"\n    },\n    \"startTime\": {\n      \"@id\": \"as:startTime\",\n      \"@type\": \"xsd:dateTime\"\n    },\n    \"summary\": \"as:summary\",\n    \"summaryMap\": {\n      \"@id\": \"as:summary\",\n      \"@container\": \"@language\"\n    },\n    \"totalItems\": {\n      \"@id\": \"as:totalItems\",\n      \"@type\": \"xsd:nonNegativeInteger\"\n    },\n    \"units\": \"as:units\",\n    \"updated\": {\n      \"@id\": \"as:updated\",\n      \"@type\": \"xsd:dateTime\"\n    },\n    \"width\": {\n      \"@id\": \"as:width\",\n      \"@type\": \"xsd:nonNegativeInteger\"\n    },\n    \"describes\": {\n      \"@id\": \"as:describes\",\n      \"@type\": \"@id\"\n    },\n    \"formerType\": {\n      \"@id\": \"as:formerType\",\n      \"@type\": \"@id\"\n    },\n    \"deleted\": {\n      \"@id\": \"as:deleted\",\n      \"@type\": \"xsd:dateTime\"\n    },\n    \"inbox\": {\n      \"@id\": \"ldp:inbox\",\n      \"@type\": \"@id\"\n    },\n    \"outbox\": {\n      \"@id\": \"as:outbox\",\n      \"@type\": \"@id\"\n    },\n    \"following\": {\n      \"@id\": \"as:following\",\n      \"@type\": \"@id\"\n    },\n    \"followers\": {\n      \"@id\": \"as:followers\",\n      \"@type\": \"@id\"\n    },\n    \"streams\": {\n      \"@id\": \"as:streams\",\n      \"@type\": \"@id\"\n    },\n    \"preferredUsername\": \"as:preferredUsername\",\n    \"endpoints\": {\n      \"@id\": \"as:endpoints\",\n      \"@type\": \"@id\"\n    },\n    \"uploadMedia\": {\n      \"@id\": \"as:uploadMedia\",\n      \"@type\": \"@id\"\n    },\n    \"proxyUrl\": {\n      \"@id\": \"as:proxyUrl\",\n      \"@type\": \"@id\"\n    },\n    \"liked\": {\n      \"@id\": \"as:liked\",\n      \"@type\": \"@id\"\n    },\n    \"oauthAuthorizationEndpoint\": {\n      \"@id\": \"as:oauthAuthorizationEndpoint\",\n      \"@type\": \"@id\"\n    },\n    \"oauthTokenEndpoint\": {\n      \"@id\": \"as:oauthTokenEndpoint\",\n      \"@type\": \"@id\"\n    },\n    \"provideClientKey\": {\n      \"@id\": \"as:provideClientKey\",\n      \"@type\": \"@id\"\n    },\n    \"signClientKey\": {\n      \"@id\": \"as:signClientKey\",\n      \"@type\": \"@id\"\n    },\n    \"sharedInbox\": {\n      \"@id\": \"as:sharedInbox\",\n      \"@type\": \"@id\"\n    },\n    \"Public\": {\n      \"@id\": \"as:Public\",\n      \"@type\": \"@id\"\n    },\n    \"source\": \"as:source\",\n    \"likes\": {\n      \"@id\": \"as:likes\",\n      \"@type\": \"@id\"\n    },\n    \"shares\": {\n      \"@id\": \"as:shares\",\n      \"@type\": \"@id\"\n    }\n  }\n}\n","documentUrl":"https:\/\/www.w3.org\/ns\/activitystreams"}
\ No newline at end of file
diff --git a/lib/Model/LinkedDataSignature.php b/lib/Model/LinkedDataSignature.php
index abf4406d..03009815 100644
--- a/lib/Model/LinkedDataSignature.php
+++ b/lib/Model/LinkedDataSignature.php
@@ -32,9 +32,12 @@ namespace OCA\Social\Model;
 
 
 use daita\MySmallPhpTools\Traits\TArrayTools;
+use JsonLdException;
 use JsonSerializable;
 use OCA\Social\Exceptions\LinkedDataSignatureMissingException;
 use OCA\Social\Model\ActivityPub\ACore;
+use OCA\Social\Service\SignatureService;
+use stdClass;
 
 
 /**
@@ -78,6 +81,7 @@ class LinkedDataSignature implements JsonSerializable {
 	public function __construct() {
 	}
 
+
 	/**
 	 * @return string
 	 */
@@ -96,6 +100,7 @@ class LinkedDataSignature implements JsonSerializable {
 		return $this;
 	}
 
+
 	/**
 	 * @return string
 	 */
@@ -305,8 +310,9 @@ class LinkedDataSignature implements JsonSerializable {
 		$res = jsonld_normalize(
 			$object,
 			[
-				'algorithm' => 'URDNA2015',
-				'format'    => 'application/nquads'
+				'algorithm'      => 'URDNA2015',
+				'format'         => 'application/nquads',
+				'documentLoader' => [SignatureService::class, 'documentLoader']
 			]
 		);
 
diff --git a/lib/Service/SignatureService.php b/lib/Service/SignatureService.php
index 45da8ad4..fff546f6 100644
--- a/lib/Service/SignatureService.php
+++ b/lib/Service/SignatureService.php
@@ -35,10 +35,13 @@ use daita\MySmallPhpTools\Model\Request;
 use daita\MySmallPhpTools\Traits\TArrayTools;
 use DateTime;
 use Exception;
+use JsonLdException;
+use OCA\Social\AppInfo\Application;
 use OCA\Social\Db\ActorsRequest;
 use OCA\Social\Exceptions\ActorDoesNotExistException;
 use OCA\Social\Exceptions\InvalidOriginException;
 use OCA\Social\Exceptions\InvalidResourceException;
+use OCA\Social\Exceptions\ItemUnknownException;
 use OCA\Social\Exceptions\LinkedDataSignatureMissingException;
 use OCA\Social\Exceptions\RedundancyLimitException;
 use OCA\Social\Exceptions\RequestContentException;
@@ -48,12 +51,16 @@ use OCA\Social\Exceptions\RequestServerException;
 use OCA\Social\Exceptions\SignatureException;
 use OCA\Social\Exceptions\SignatureIsGoneException;
 use OCA\Social\Exceptions\SocialAppConfigException;
-use OCA\Social\Exceptions\ItemUnknownException;
 use OCA\Social\Model\ActivityPub\ACore;
 use OCA\Social\Model\ActivityPub\Actor\Person;
 use OCA\Social\Model\LinkedDataSignature;
 use OCA\Social\Model\RequestQueue;
+use OCP\Files\NotFoundException;
+use OCP\Files\NotPermittedException;
+use OCP\Files\SimpleFS\ISimpleFile;
+use OCP\Files\SimpleFS\ISimpleFolder;
 use OCP\IRequest;
+use stdClass;
 
 class SignatureService {
 
@@ -256,7 +263,7 @@ class SignatureService {
 		try {
 			$signature->sign();
 			$object->setSignature($signature);
-		} catch (LinkedDataSignatureMissingException $e) {
+		} catch (Exception $e) {
 		}
 	}
 
@@ -412,5 +419,113 @@ class SignatureService {
 		}
 	}
 
+
+	/**
+	 * @param string $url
+	 *
+	 * @return stdClass
+	 * @throws NotPermittedException
+	 * @throws JsonLdException
+	 */
+	public static function documentLoader($url): stdClass {
+		$recursion = 0;
+		$x = debug_backtrace();
+		if ($x) {
+			foreach ($x as $n) {
+				if ($n['function'] === __FUNCTION__) {
+					$recursion++;
+				}
+			}
+		}
+
+		if ($recursion > 5) {
+			exit();
+		}
+
+		$folder = self::getContextCacheFolder();
+		$filename = parse_url($url, PHP_URL_HOST) . parse_url($url, PHP_URL_PATH);
+		$filename = str_replace('/', '.', $filename) . '.json';
+
+		try {
+			$cache = $folder->getFile($filename);
+			self::updateContextCacheDocument($cache, $url);
+
+			$data = json_decode($cache->getContent());
+		} catch (NotFoundException $e) {
+			$data = self::generateContextCacheDocument($folder, $filename, $url);
+		}
+
+		return $data;
+	}
+
+
+	/**
+	 * @return ISimpleFolder
+	 * @throws NotPermittedException
+	 */
+	private static function getContextCacheFolder(): ISimpleFolder {
+		$path = 'context';
+
+		$appData = \OC::$server->getAppDataDir(Application::APP_NAME);
+		try {
+			$folder = $appData->getFolder($path);
+		} catch (NotFoundException $e) {
+			$folder = $appData->newFolder($path);
+		}
+
+		return $folder;
+	}
+
+
+	/**
+	 * @param ISimpleFolder $folder
+	 * @param string $filename
+	 *
+	 * @param string $url
+	 *
+	 * @return stdClass
+	 * @throws JsonLdException
+	 * @throws NotPermittedException
+	 */
+	private static function generateContextCacheDocument(
+		ISimpleFolder $folder, string $filename, string $url
+	): stdClass {
+
+		try {
+			$data = jsonld_default_document_loader($url);
+			$content = json_encode($data);
+		} catch (JsonLdException $e) {
+			$context = file_get_contents(__DIR__ . '/../../context/' . $filename);
+			if (is_bool($context)) {
+				throw $e;
+			}
+
+			$content = $context;
+			$data = json_decode($context);
+		}
+
+		$cache = $folder->newFile($filename);
+		$cache->putContent($content);
+
+		return $data;
+	}
+
+
+	/**
+	 * @param ISimpleFile $cache
+	 * @param string $url
+	 *
+	 * @throws NotPermittedException
+	 */
+	private static function updateContextCacheDocument(ISimpleFile $cache, string $url) {
+		if ($cache->getMTime() < (time() - 98765)) {
+			try {
+				$data = jsonld_default_document_loader($url);
+				$cache->putContent(json_encode($data));
+			} catch (JsonLdException $e) {
+			}
+		}
+	}
+
 }