2:21 p.m.
Log information about programs connecting to and disconnecting from the
audit netlink multicast socket. This is needed so that during
investigations a security officer can tell who or what had access to the
audit trail. This helps to meet the FAU_SAR.2 requirement for Common
Criteria. Here is the systemd startup event:
type=UNKNOWN[1335] msg=audit(2020-01-17 10:30:33.731:6) : pid=1 uid=root auid=unset
tty=(none) ses=unset subj=kernel comm=systemd exe=/usr/lib/systemd/systemd nl-mcgrp=1
op=connect res=yes
And the events from the test suite:
type=PROCTITLE msg=audit(2020-01-17 10:36:24.050:294) : proctitle=/usr/bin/perl -w
amcast_joinpart/test
type=SOCKADDR msg=audit(2020-01-17 10:36:24.050:294) : saddr={ saddr_fam=netlink
nlnk-fam=16 nlnk-pid=0 }
type=SYSCALL msg=audit(2020-01-17 10:36:24.050:294) : arch=x86_64 syscall=bind success=yes
exit=0 a0=0x7 a1=0x55d65cb79090 a2=0xc a3=0x0 items=0 ppid=671 pid=674 auid=root uid=root
gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=3
comm=perl exe=/usr/bin/perl subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
key=(null)
type=UNKNOWN[1335] msg=audit(2020-01-17 10:36:24.050:294) : pid=674 uid=root auid=root
tty=ttyS0 ses=3 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 comm=perl
exe=/usr/bin/perl nl-mcgrp=1 op=connect res=yes
type=UNKNOWN[1335] msg=audit(2020-01-17 10:36:24.051:295) : pid=674 uid=root auid=root
tty=ttyS0 ses=3 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 comm=perl
exe=/usr/bin/perl nl-mcgrp=1 op=disconnect res=yes
Please see the upstream issue tracker:
https://github.com/linux-audit/audit-kernel/issues/28
https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Multicast-Sock...
https://github.com/rgbriggs/audit-testsuite/compare/ghak28-mcast-part-join
Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com>
---
Note: msg type 1334 was skipped due to BPF accepted in another tree.
Note: v5 due to previous 2014-10-07, 2015-07-23, 2016-11-30, 2017-10-13
Note: subj attrs included due to missing syscall record for systemd (audit=1)
Note: tried refactor of subj attrs, but this is yet another new order.
---
include/uapi/linux/audit.h | 1 +
kernel/audit.c | 48 ++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 45 insertions(+), 4 deletions(-)
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 3ad935527177..67fb24472dc2 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -116,6 +116,7 @@
#define AUDIT_FANOTIFY 1331 /* Fanotify access decision */
#define AUDIT_TIME_INJOFFSET 1332 /* Timekeeping offset injected */
#define AUDIT_TIME_ADJNTPVAL 1333 /* NTP value adjustment */
+#define AUDIT_EVENT_LISTENER 1335 /* Task joined multicast read socket */
#define AUDIT_AVC 1400 /* SE Linux avc denial or grant */
#define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */
diff --git a/kernel/audit.c b/kernel/audit.c
index 17b0d523afb3..478259f3fa53 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1520,20 +1520,60 @@ static void audit_receive(struct sk_buff *skb)
audit_ctl_unlock();
}
+/* Log information about who is connecting to the audit multicast socket */
+static void audit_log_multicast_bind(int group, const char *op, int err)
+{
+ const struct cred *cred;
+ struct tty_struct *tty;
+ char comm[sizeof(current->comm)];
+ struct audit_buffer *ab;
+
+ if (!audit_enabled)
+ return;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_EVENT_LISTENER);
+ if (!ab)
+ return;
+
+ cred = current_cred();
+ tty = audit_get_tty();
+ audit_log_format(ab, "pid=%u uid=%u auid=%u tty=%s ses=%u",
+ task_pid_nr(current),
+ from_kuid(&init_user_ns, cred->uid),
+ from_kuid(&init_user_ns, audit_get_loginuid(current)),
+ tty ? tty_name(tty) : "(none)",
+ audit_get_sessionid(current));
+ audit_put_tty(tty);
+ audit_log_task_context(ab); /* subj= */
+ audit_log_format(ab, " comm=");
+ audit_log_untrustedstring(ab, get_task_comm(comm, current));
+ audit_log_d_path_exe(ab, current->mm); /* exe= */
+ audit_log_format(ab, " nl-mcgrp=%d op=%s res=%d", group, op, !err);
+ audit_log_end(ab);
+}
+
/* Run custom bind function on netlink socket group connect or bind requests. */
-static int audit_bind(struct net *net, int group)
+static int audit_multicast_bind(struct net *net, int group)
{
+ int err = 0;
+
if (!capable(CAP_AUDIT_READ))
- return -EPERM;
+ err = -EPERM;
+ audit_log_multicast_bind(group, "connect", err);
+ return err;
+}
- return 0;
+static void audit_multicast_unbind(struct net *net, int group)
+{
+ audit_log_multicast_bind(group, "disconnect", 0);
}
static int __net_init audit_net_init(struct net *net)
{
struct netlink_kernel_cfg cfg = {
.input = audit_receive,
- .bind = audit_bind,
+ .bind = audit_multicast_bind,
+ .unbind = audit_multicast_unbind,
.flags = NL_CFG_F_NONROOT_RECV,
.groups = AUDIT_NLGRP_MAX,
};
--
1.8.3.1