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 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-Sock... 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(a)redhat.com&gt; --- 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