id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	launchpad_bug
956	embed security metadata in parent directory	zooko		"#954 (revoke write authority), #955 (use client-side storage to defend against rollback attack) and not-yet-ticketed ""LAFS 301 Moved Permanently"" all involve a small fixed amount of metadata.

A ""highest known version number"" for a mutable file or directory, which according to #955 could be stored in a client to prevent that client from perceiving a rollback could ''also'' be stored in a parent directory which links to that mutable file or directory, thus preventing someone who accesses the file through that parent directory from seeing a rollback to a version earlier than the most recent known version when that child link was last updated.

A LAFS 301 Moved Permanently marker has to be stored in the shares with the file content itself, but it could ''also'' be copied into a parent directory that linked to that file, thus optimizing out a round trip to the old location and also preventing a rollback attack from undoing the Moved Permanently (from the perspective of someone accessing the file through that parent directory).

Likewise, a write-authority-revocation marker, a.k.a. a ""petrification marker"" has to live in the shares next to the file contents itself, but it could ''also'' be copied into a directory which links to that file, preventing rollback attack from unpetrifying the file (from the perspective of someone accessing the file through that parent directory)."	enhancement	new	major		code-dirnodes	1.6.0		mutable newcaps newurls metadata forward-compatibility rollback revocation