Commit 9d2161be authored Apr 22, 2020 by Richard Guy Briggs Committed by Paul Moore Apr 27, 2020

audit: log audit netlink multicast bind and unbind

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=PROCTITLE msg=audit(2020-04-22 10:10:21.787:10) : proctitle=/init
type=SYSCALL msg=audit(2020-04-22 10:10:21.787:10) : arch=x86_64 syscall=bind success=yes exit=0 a0=0x19 a1=0x555f4aac7e90 a2=0xc a3=0x7ffcb792ff44 items=0 ppid=0 pid=1 auid=unset uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=(none) ses=unset comm=systemd exe=/usr/lib/systemd/systemd subj=kernel key=(null)
type=UNKNOWN[1335] msg=audit(2020-04-22 10:10:21.787:10) : 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 events from the test suite that just uses close():
type=PROCTITLE msg=audit(2020-04-22 11:47:08.501:442) : proctitle=/usr/bin/perl -w amcast_joinpart/test
type=SYSCALL msg=audit(2020-04-22 11:47:08.501:442) : arch=x86_64 syscall=bind success=yes exit=0 a0=0x7 a1=0x563004378760 a2=0xc a3=0x0 items=0 ppid=815 pid=818 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=1 comm=perl exe=/usr/bin/perl subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
type=UNKNOWN[1335] msg=audit(2020-04-22 11:47:08.501:442) : pid=818 uid=root auid=root tty=ttyS0 ses=1 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(2020-04-22 11:47:08.501:443) : pid=818 uid=root auid=root tty=ttyS0 ses=1 subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 comm=perl exe=/usr/bin/perl nl-mcgrp=1 op=disconnect res=yes

And the events from the test suite using setsockopt with NETLINK_DROP_MEMBERSHIP:
type=PROCTITLE msg=audit(2020-04-22 11:39:53.291:439) : proctitle=/usr/bin/perl -w amcast_joinpart/test
type=SYSCALL msg=audit(2020-04-22 11:39:53.291:439) : arch=x86_64 syscall=bind success=yes exit=0 a0=0x7 a1=0x5560877c2d20 a2=0xc a3=0x0 items=0 ppid=772 pid=775 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=1 comm=perl exe=/usr/bin/perl subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
type=UNKNOWN[1335] msg=audit(2020-04-22 11:39:53.291:439) : pid=775 uid=root auid=root tty=ttyS0 ses=1 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=PROCTITLE msg=audit(2020-04-22 11:39:53.292:440) : proctitle=/usr/bin/perl -w amcast_joinpart/test
type=SYSCALL msg=audit(2020-04-22 11:39:53.292:440) : arch=x86_64 syscall=setsockopt success=yes exit=0 a0=0x7 a1=SOL_NETLINK a2=0x2 a3=0x7ffc8366f000 items=0 ppid=772 pid=775 auid=root uid=root gid=root euid=root suid=root fsuid=root egid=root sgid=root fsgid=root tty=ttyS0 ses=1 comm=perl exe=/usr/bin/perl subj=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 key=(null)
type=UNKNOWN[1335] msg=audit(2020-04-22 11:39:53.292:440) : pid=775 uid=root auid=root tty=ttyS0 ses=1 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 at
https://github.com/linux-audit/audit-kernel/issues/28
With the feature description at
https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Multicast-Socket-Join-Part
The testsuite support is at
https://github.com/rgbriggs/audit-testsuite/compare/ghak28-mcast-part-join
https://github.com/linux-audit/audit-testsuite/pull/93
And the userspace support patch is at
https://github.com/linux-audit/audit-userspace/pull/114

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

parent 3054d067

include/uapi/linux/audit.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -117,6 +117,7 @@
		#define AUDIT_TIME_INJOFFSET 1332 /* Timekeeping offset injected */
		#define AUDIT_TIME_ADJNTPVAL 1333 /* NTP value adjustment */
		#define AUDIT_BPF 1334 /* BPF subsystem */
		#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 */

kernel/audit.c

+44 −4

Original line number	Diff line number	Diff line
		@@ -1530,20 +1530,60 @@ 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(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(group, "connect", err);
		return err;
		}

		return 0;
		static void audit_multicast_unbind(struct net *net, int group)
		{
		audit_log_multicast(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,
		};

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