[PATCH 0/6][v2] audit: implement multicast socket for journald

Richard Guy Briggs
2014-04-23T01:31:52Z

This is a patch set Eric Paris and I have been working on to add a restricted
capability read-only netlink multicast socket to kernel audit to enable
userspace clients such as systemd/journald to receive audit logs, in addition
to the bidirectional auditd userspace client.

Currently, auditd has the CAP_AUDIT_CONTROL and CAP_AUDIT_WRITE capabilities
(but uses CAP_NET_ADMIN). The CAP_AUDIT_READ capability will be added for use
by read-only AUDIT_NLGRP_READLOG multicast group clients to the kaudit
subsystem. This will remove the dependence on CAP_NET_ADMIN for the multicast
read-only socket.

Patches 1-3 provide a way for per-protocol bind functions to
signal an error and to be able to clean up after themselves.

The first netfilter cleanup patch has already been accepted by a netfilter
maintainer, though I don't see it upstream yet, so it is included for
completeness.

The second patch adds the per-protocol bind function return code to signal to
the netlink code that no further processing should be done and to undo the work
already done.
V1: This rev fixes a bug introduced by flattening the code in the last posting.
*V2: This rev moves the per-protocol bind call above the socket exposure call
and refactors out the unbind procedure.

The third provides a way per protocol to undo bind actions on DROP.

Patches 4-6 implement the audit multicast socket with capability checking.

The fourth patch adds the bind function capability check to multicast join
requests for audit.

The fifth patch adds the audit log read multicast group. An assumption has
been made that systemd/journald reside in the initial network namespace. This
could be changed to check the actual network namespace of systemd/journald
should this assumption no longer be true since audit now supports all network
namespaces. This version of the patch now directly sends the broadcast when
the packet is ready rather than waiting until it passes the queue.

The sixth checks if any clients actually exist before sending.

Since the net tree is busier than the audit tree, conflicts are more likely and
the audit patches depend on the net patches, it is proposed to have the net
tree carry this entire patchset for 3.16. Are the net maintainers ok with this?

https://bugzilla.redhat.com/show_bug.cgi?id=887992

First posted: https://www.redhat.com/archives/linux-audit/2013-January/msg00008.html
https://lkml.org/lkml/2013/1/27/279

Please find source for a test program at:
http://people.redhat.com/rbriggs/audit-multicast-listen/

Richard Guy Briggs (6):
netlink: simplify nfnetlink_bind
netlink: have netlink per-protocol bind function return an error
code.
netlink: implement unbind to netlink_setsockopt
NETLINK_DROP_MEMBERSHIP
audit: add netlink audit protocol bind to check capabilities on
multicast join
audit: add netlink multicast group for log read
audit: send multicast messages only if there are listeners

include/linux/netlink.h | 3 +-
include/uapi/linux/audit.h | 8 ++++
include/uapi/linux/capability.h | 7 +++-
kernel/audit.c | 64 ++++++++++++++++++++++++++++++--
net/netfilter/nfnetlink.c | 10 ++---
net/netlink/af_netlink.c | 70 +++++++++++++++++++++++++----------
net/netlink/af_netlink.h | 6 ++-
security/selinux/include/classmap.h | 2 +-
8 files changed, 135 insertions(+), 35 deletions(-)