Re: [PATCH ghak28 V7] audit: log audit netlink multicast bind and unbind events

From: Richard Guy Briggs
Date: Fri Apr 17 2020 - 17:34:41 EST

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On 2020-04-17 17:18, Paul Moore wrote:
> On Tue, Mar 17, 2020 at 12:04 PM Richard Guy Briggs <rgb@xxxxxxxxxx> 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=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=PROCTITLE msg=audit(2020-03-17 11:35:31.474:344) : proctitle=/usr/bin/perl -w amcast_joinpart/test
> > type=SYSCALL msg=audit(2020-03-17 11:35:31.474:344) : arch=x86_64 syscall=setsockopt success=yes exit=0 a0=0x7 a1=SOL_NETLINK a2=0x2 a3=0x7ffee21ca5f0 items=0 ppid=686 pid=689 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(2020-03-17 11:35:31.474:344) : pid=689 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
> >
> > 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
>
> This patch looks fine to me, but this line is curious ... I'm assuming
> this is just a stray/cut-n-paste-error from the last time you updated
> the commit description? If so, just let me know and I can drop it
> while merging, otherwise there is something odd going on ....

That last line is the result of close() from an earlier version of the
testsuite, rather than setsockopt(..., NETLINK_DROP_MEMBERSHIP, ...).

This is why we need the subject attributes, as noted in the first note
above the changelog below.

> > 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@xxxxxxxxxx>
> >
> > ---
> > Note: subj attrs included due to missing syscall record for disconnect on close
> > Note: tried refactor of subj attrs, but this is yet another new order.
> >
> > Changelog:
> > v7:
> > - rename audit_log_multicast_bind to audit_log_multicast
> >
> > v6:
> > - rebased on 5.6-rc1 audit/next and audit log BPF
> > - updated patch description sample records
> >
> > v5:
> > - rebased on 5.5-rc1 audit/next
> > - group bind/unbind ops
> > - add audit context
> > - justify message number skip
> > - check audit_enabled
> > - change field name from nlnk-grp to nl-mcgrp
> > - fix whitespace issues
> >
> > v4:
> > - 2017-10-13 sgrubb
> > - squash to 1 patch
> > - rebase on KERN_MODULE event
> > - open code subj attrs
> >
> > v3:
> > - 2016-11-30 sgrubb
> > - rebase on REPLACE event
> > - minimize audit_log_format calls
> > - rename audit_log_bind to audit_log_multicast_bind
> >
> > v2:
> > - 2015-07-23 sgrubb
> > - spin off audit_log_task_simple in seperate patch
> >
> > v1:
> > - 2014-10-07 rgb
> > ---
> > 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 b96331e1976d..612bd818f6d7 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(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,
> > };
> > --
> > 1.8.3.1
> >
>
>
> --
> paul moore
> www.paul-moore.com
>
>
> --
> Linux-audit mailing list
> Linux-audit@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/linux-audit

- 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

Next message: Martin K. Petersen: "Re: [PATCH] scsi: mvsas: make mvst_host_attrs static"
Previous message: Florian Westphal: "Re: WARNING in nf_nat_unregister_fn"
In reply to: Paul Moore: "Re: [PATCH ghak28 V7] audit: log audit netlink multicast bind and unbind events"
Next in thread: Paul Moore: "Re: [PATCH ghak28 V7] audit: log audit netlink multicast bind and unbind events"
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