Re: [PATCH ghak28 V6] audit: log audit netlink multicast bind and unbind events
From: Richard Guy Briggs
Date: Tue Feb 18 2020 - 16:12:36 EST
On 2020-02-18 15:51, Richard Guy Briggs wrote:
> 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(2020-02-18 15:26:50.775:10) : proctitle=/init
> type=SYSCALL msg=audit(2020-02-18 15:26:50.775:10) : arch=x86_64 syscall=bind success=yes exit=0 a0=0x19 a1=0x55645c369b70 a2=0xc a3=0x7fff9fedec24 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(2020-02-18 15:26:50.775:10) : 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 the events from the test suite:
>
> type=PROCTITLE msg=audit(2020-02-18 15:28:01.594:307) : proctitle=/usr/bin/perl -w amcast_joinpart/test
> type=SOCKADDR msg=audit(2020-02-18 15:28:01.594:307) : saddr={ saddr_fam=netlink nlnk-fam=16 nlnk-pid=0 }
> type=SYSCALL msg=audit(2020-02-18 15:28:01.594:307) : arch=x86_64 syscall=bind success=yes exit=0 a0=0x7 a1=0x558ebc428be0 a2=0xc a3=0x0 items=0 ppid=642 pid=645 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(2020-02-18 15:28:01.594:307) : pid=645 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(2020-01-17 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-Socket-Join-Part
> https://github.com/rgbriggs/audit-testsuite/compare/ghak28-mcast-part-join
>
> Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
This was slightly premature. I had intended to send the ghak120 (norule
missing accompanying) patch first to start a discussion. The results
above are depending on that patch.
> ---
> 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 a534d71e689a..9b6a973f4cc3 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -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 */
> 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
>
- RGB
--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635