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

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&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));

+ 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); +}