[PATCH ghak25 v2 0/9] Address NETFILTER_CFG issues

From: Richard Guy Briggs
Date: Mon Jan 06 2020 - 13:55:30 EST

There were questions about the presence and cause of unsolicited syscall events
in the logs containing NETFILTER_CFG records and sometimes unaccompanied

During testing at least the following list of events trigger NETFILTER_CFG
records and the syscalls related (There may be more events that will trigger
this message type.):
init_module, finit_module: modprobe
setsockopt: iptables-restore, ip6tables-restore, ebtables-restore
unshare: (h?)ostnamed
clone: libvirtd

The syscall events unsolicited by any audit rule were found to be caused by a
missing !audit_dummy_context() check before creating a NETFILTER_CFG
record and issuing the record immediately rather than saving the
information to create the record at syscall exit.
Check !audit_dummy_context() before creating the NETFILTER_CFG record.

The vast majority of unaccompanied records are caused by the fedora default
rule: "-a never,task" and the occasional early startup one is I believe caused
by the iptables filter table module hard linked into the kernel rather than a
loadable module. The !audit_dummy_context() check above should avoid them.

A couple of other factors should help eliminate unaccompanied records
which include commit cb74ed278f80 ("audit: always enable syscall
auditing when supported and audit is enabled") which makes sure that
when audit is enabled, so automatically is syscall auditing, and ghak66
which addressed initializing audit before PID 1.

Ebtables module initialization to register tables doesn't generate records
because it was never hooked in to audit. Recommend adding audit hooks to log

Table unregistration was never logged, which is now covered.

Seemingly duplicate records are not actually exact duplicates that are caused
by netfilter table initialization in different network namespaces from the same
syscall. Recommend adding the network namespace ID (proc inode and dev)
to the record to make this obvious (address later with ghak79 after nsid

See: https://github.com/linux-audit/audit-kernel/issues/25
See: https://github.com/linux-audit/audit-kernel/issues/35
See: https://github.com/linux-audit/audit-kernel/issues/43
See: https://github.com/linux-audit/audit-kernel/issues/44

- Rebase (audit/next 5.5-rc1) to get audit_context access and ebt_register_table ret code
- Split x_tables and ebtables updates
- Check audit_dummy_context
- Store struct audit_nfcfg params in audit_context, abstract to audit_nf_cfg() call
- Restore back to "table, family, entries" from "family, table, entries"
- Log unregistration of tables
- Add "op=" at the end of the AUDIT_NETFILTER_CFG record
- Defer nsid patch (ghak79) to once nsid patchset upstreamed (ghak32)
- Add ghak refs

Richard Guy Briggs (9):
netfilter: normalize x_table function declarations
netfilter: normalize ebtables function declarations
netfilter: normalize ebtables function declarations II
audit: record nfcfg params
netfilter: x_tables audit only on syscall rule
netfilter: ebtables audit only on syscall rule
netfilter: ebtables audit table registration
netfilter: add audit operation field
netfilter: audit table unregister actions

include/linux/audit.h | 11 ++++
kernel/auditsc.c | 18 +++++
net/bridge/netfilter/ebtables.c | 142 ++++++++++++++++++++--------------------
net/netfilter/x_tables.c | 56 +++++++---------
4 files changed, 124 insertions(+), 103 deletions(-)