On 11/14/23 13:36, Sush Shringarputale wrote:
On 11/13/2023 10:59 AM, Stefan Berger wrote:
On 10/19/23 14:49, Tushar Sugandhi wrote:
=======================================================================
| Introduction |
=======================================================================
This document provides a detailed overview of the proposed Kernel
feature IMA log snapshotting. It describes the motivation behind the
proposal, the problem to be solved, a detailed solution design with
examples, and describes the changes to be made in the clients/services
which are part of remote-attestation system. This is the 2nd version
of the proposal. The first version is present here[1].
Table of Contents:
------------------
A. Motivation and Background
B. Goals and Non-Goals
B.1 Goals
B.2 Non-Goals
C. Proposed Solution
C.1 Solution Summary
C.2 High-level Work-flow
D. Detailed Design
D.1 Snapshot Aggregate Event
D.2 Snapshot Triggering Mechanism
D.3 Choosing A Persistent Storage Location For Snapshots
D.4 Remote-Attestation Client/Service-side Changes
D.4.a Client-side Changes
D.4.b Service-side Changes
E. Example Walk-through
F. Other Design Considerations
G. References
Userspace applications will have to know
a) where are the shard files?
We describe the file storage location choices in section D.3, but user
applications will have to query the well-known location described there.
b) how do I read the shard files while locking out the producer of the
shard files?
IMO, this will require a well known config file and a locking method
(flock) so that user space applications can work together in this new
environment. The lock could be defined in the config file or just be
the config file itself.
The flock is a good idea for co-ordination between UM clients. While
the Kernel cannot enforce any access in this way, any UM process that
is planning on triggering the snapshot mechanism should follow that
protocol. We will ensure we document that as the best-practices in
the patch series.
It's more than 'best practices'. You need a well-known config file with
well-known config options in it.
All clients that were previously just trying to read new bytes from the
IMA log cannot do this anymore in the presence of a log shard producer
but have to also learn that a new log shard has been produced so they
need to figure out the new position in the log where to read from. So
maybe a counter in a config file should indicate to the log readers that
a new log has been produced -- otherwise they would have to monitor all
the log shard files or the log shard file's size.
Iff the log-shard producer were configured to discard leading parts of
the log then that should also be noted in a config file so clients, that
need to see the beginning of the log, can refuse early on to work on a
machine that either is configured this way or where the discarding has
already happened.
Stefan
- Sush
