Re: Encryption Pager
Re: Encryption Pager
- Subject: Re: Encryption Pager
- From: Terry Lambert <email@hidden>
- Date: Wed, 27 Aug 2008 17:43:35 -0700
On Aug 27, 2008, at 5:49 AM, Nicolas CORMIER wrote:
Hi folks,
I would like to know if it is possible to create an external pager.
My main goal is to decrypt encrypted pages when they are accessed at
run-time.
I found some interesting articles like "extending the Mach external
pager interface to accommodate user-level page replacement policies".
But I actually don't know how to exploit them.
We already have an internal pager that does this; that's how
"encrypted swap" works.
The traditional UNIX way to deal with this inside a process address
space is to fix up the SIGSEGV/SIGBUS signals by providing handlers,
and then fixing up the faults when the signal handler fires.
An alternative method which will work on Mac OS X because of the way
signals are implemented would be to obtain the task exception port for
the task, and fix up the exception when it is raised before it becomes
a signal. You will also need the task port, so that you other process
can fix up the address space contents in the target task.
Finally, as shipped, the Leopard code still has most of the Mach
external pager support intact (not ripped out). If you really want to
do this, you should look at the CMU or OSF documentation on how to
write external pagers.
-- Terry
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