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>
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@ -117,6 +117,7 @@
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#define AUDIT_TIME_INJOFFSET 1332 /* Timekeeping offset injected */
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#define AUDIT_TIME_ADJNTPVAL 1333 /* NTP value adjustment */
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#define AUDIT_BPF 1334 /* BPF subsystem */
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#define AUDIT_EVENT_LISTENER 1335 /* Task joined multicast read socket */
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#define AUDIT_AVC 1400 /* SE Linux avc denial or grant */
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#define AUDIT_SELINUX_ERR 1401 /* Internal SE Linux Errors */
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@ -1530,20 +1530,60 @@ static void audit_receive(struct sk_buff *skb)
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audit_ctl_unlock();
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}
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/* Run custom bind function on netlink socket group connect or bind requests. */
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static int audit_bind(struct net *net, int group)
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/* Log information about who is connecting to the audit multicast socket */
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static void audit_log_multicast(int group, const char *op, int err)
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{
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if (!capable(CAP_AUDIT_READ))
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return -EPERM;
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const struct cred *cred;
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struct tty_struct *tty;
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char comm[sizeof(current->comm)];
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struct audit_buffer *ab;
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return 0;
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if (!audit_enabled)
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return;
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ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_EVENT_LISTENER);
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if (!ab)
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return;
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cred = current_cred();
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tty = audit_get_tty();
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audit_log_format(ab, "pid=%u uid=%u auid=%u tty=%s ses=%u",
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task_pid_nr(current),
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from_kuid(&init_user_ns, cred->uid),
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from_kuid(&init_user_ns, audit_get_loginuid(current)),
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tty ? tty_name(tty) : "(none)",
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audit_get_sessionid(current));
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audit_put_tty(tty);
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audit_log_task_context(ab); /* subj= */
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audit_log_format(ab, " comm=");
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audit_log_untrustedstring(ab, get_task_comm(comm, current));
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audit_log_d_path_exe(ab, current->mm); /* exe= */
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audit_log_format(ab, " nl-mcgrp=%d op=%s res=%d", group, op, !err);
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audit_log_end(ab);
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}
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/* Run custom bind function on netlink socket group connect or bind requests. */
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static int audit_multicast_bind(struct net *net, int group)
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{
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int err = 0;
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if (!capable(CAP_AUDIT_READ))
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err = -EPERM;
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audit_log_multicast(group, "connect", err);
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return err;
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}
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static void audit_multicast_unbind(struct net *net, int group)
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{
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audit_log_multicast(group, "disconnect", 0);
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}
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static int __net_init audit_net_init(struct net *net)
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{
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struct netlink_kernel_cfg cfg = {
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.input = audit_receive,
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.bind = audit_bind,
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.bind = audit_multicast_bind,
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.unbind = audit_multicast_unbind,
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.flags = NL_CFG_F_NONROOT_RECV,
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.groups = AUDIT_NLGRP_MAX,
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};
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