memory: new getFilesOwner method:

this method is used by `getFiles` and `setFile` and fill `owner` when it's missing to
avoid getting accidentally files from other users.

`owner` is not filled in some case (no client, `file_id` or `parent` specified) and an
exception is raised if a component has neither `owner` nor `peer_jid` specified.

sat/memory/memory.py

@@ -1451,6 +1451,37 @@ class Memory(object):
             ),
         )
 
+    def getFilesOwner(
+            self,
+            client,
+            owner: Optional[jid.JID],
+            peer_jid: Optional[jid.JID],
+            file_id: Optional[str],
+            parent: Optional[str]
+    ) -> jid.JID:
+        """Get owner to use for a file operation
+
+        if owner is not explicitely set, a suitable one will be used (client.jid for
+        clients, peer_jid for components).
+        @raise exception.InternalError: we are one a component, and neither owner nor
+            peer_jid are set
+        """
+        if owner is not None:
+            return owner.userhostJID()
+        if client is None:
+            # client may be None when looking for file with public_id
+            return None
+        if file_id or parent:
+            # owner has already been filtered on parent file
+            return None
+        if not client.is_component:
+            return client.jid.userhostJID()
+        if peer_jid is None:
+            raise exceptions.InternalError(
+                "Owner must be set for component if peer_jid is None"
+            )
+        return peer_jid.userhostJID()
+
     @defer.inlineCallbacks
     def getFiles(
         self, client, peer_jid, file_id=None, version=None, parent=None, path=None,
@@ -1485,7 +1516,8 @@ class Memory(object):
         @param unique(bool): if True will remove duplicates
         @param perms_to_check(tuple[unicode],None): permission to check
             must be a tuple of C.ACCESS_PERM_* or None
-            if None, permission will no be checked (peer_jid must be None too in this case)
+            if None, permission will no be checked (peer_jid must be None too in this
+            case)
         other params are the same as for [setFile]
         @return (list[dict]): files corresponding to filters
         @raise exceptions.NotFound: parent directory not found (when path is specified)
@@ -1498,8 +1530,7 @@ class Memory(object):
                 "if you want to disable permission check, both peer_jid and "
                 "perms_to_check must be None"
             )
-        if owner is not None:
-            owner = owner.userhostJID()
+        owner = self.getFilesOwner(client, owner, peer_jid, file_id, parent)
         if path is not None:
             path = str(path)
             # permission are checked by _getParentDir
@@ -1600,7 +1631,7 @@ class Memory(object):
             will be encoded to json in database
         @param perms_to_check(tuple[unicode],None): permission to check
             must be a tuple of C.ACCESS_PERM_* or None
-            if None, permission will no be checked (peer_jid must be None too in this
+            if None, permission will not be checked (peer_jid must be None too in this
             case)
         @param profile(unicode): profile owning the file
         """
@@ -1630,8 +1661,7 @@ class Memory(object):
                 raise ValueError(
                     "version, file_hash, size and mime_type can't be set for a directory"
                 )
-        if owner is not None:
-            owner = owner.userhostJID()
+        owner = self.getFilesOwner(client, owner, peer_jid, file_id, parent)
 
         if path is not None:
             path = str(path)