Re: [PATCH ghak28 V4] audit: log audit netlink multicast bind and unbind events

On Wednesday, January 22, 2020 5:40:10 PM EST Paul Moore wrote: > On Fri, Jan 17, 2020 at 3:21 PM Richard Guy Briggs <rgb(a)redhat.com&gt; 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=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-So > > cket-Join-Part > > https://github.com/rgbriggs/audit-testsuite/compare/ghak28-mcast-part-> > join> > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > > > --- > > 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)); > > Don't we already get all of that information as part of the syscall record? We don't want or need a syscall record. It doesn't add anything to the necessary information. Also, when we have syscall records, people expect that they obey the syscall auditing. Especially wrt "never" audit rules.

> > + audit_put_tty(tty); > > + audit_log_task_context(ab); /* subj= */ > > Also part of the syscall record. > > > + audit_log_format(ab, " comm="); > > + audit_log_untrustedstring(ab, get_task_comm(comm, current)); > > Again. > > > + audit_log_d_path_exe(ab, current->mm); /* exe= */ > > Again. > > > + audit_log_format(ab, " nl-mcgrp=%d op=%s res=%d", group, op, > > !err); > This part is new ;) > > > + audit_log_end(ab); > > +} > > I'm pretty sure these are the same arguments I made when Steve posted > a prior version of this patch. No. You didn't mind it then. What you objected to was that I wrote a helper function that could be used by future audit events to start a format standardization process.

The event looks good to me. Ack for the format being acceptable to existing tools. -Steve