audit_trigger.c revision 176686 
1/*-
2 * Copyright (c) 2005 Wayne J. Salamon
3 * All rights reserved.
4 *
5 * This software was developed by Wayne Salamon for the TrustedBSD Project.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 * $FreeBSD: head/sys/security/audit/audit_trigger.c 176686 2008-03-01 11:04:04Z rwatson $
29 */
30
31#include <sys/param.h>
32#include <sys/conf.h>
33#include <sys/kernel.h>
34#include <sys/malloc.h>
35#include <sys/proc.h>
36#include <sys/queue.h>
37#include <sys/systm.h>
38#include <sys/uio.h>
39
40#include <security/audit/audit.h>
41#include <security/audit/audit_private.h>
42
43/*
44 * Structures and operations to support the basic character special device
45 * used to communicate with userland.  /dev/audit reliably delivers one-byte
46 * messages to a listening application (or discards them if there is no
47 * listening application).
48 *
49 * Currently, select/poll are not supported on the trigger device.
50 */
51struct trigger_info {
52	unsigned int			trigger;
53	TAILQ_ENTRY(trigger_info)	list;
54};
55
56static MALLOC_DEFINE(M_AUDITTRIGGER, "audit_trigger", "Audit trigger events");
57static struct cdev *audit_dev;
58static int audit_isopen = 0;
59static TAILQ_HEAD(, trigger_info) trigger_list;
60static struct mtx audit_trigger_mtx;
61
62static int
63audit_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
64{
65	int error;
66
67	/* Only one process may open the device at a time. */
68	mtx_lock(&audit_trigger_mtx);
69	if (!audit_isopen) {
70		error = 0;
71		audit_isopen = 1;
72	} else
73		error = EBUSY;
74	mtx_unlock(&audit_trigger_mtx);
75
76	return (error);
77}
78
79static int
80audit_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
81{
82	struct trigger_info *ti;
83
84	/* Flush the queue of pending trigger events. */
85	mtx_lock(&audit_trigger_mtx);
86	audit_isopen = 0;
87	while (!TAILQ_EMPTY(&trigger_list)) {
88		ti = TAILQ_FIRST(&trigger_list);
89		TAILQ_REMOVE(&trigger_list, ti, list);
90		free(ti, M_AUDITTRIGGER);
91	}
92	mtx_unlock(&audit_trigger_mtx);
93
94	return (0);
95}
96
97static int
98audit_read(struct cdev *dev, struct uio *uio, int ioflag)
99{
100	int error = 0;
101	struct trigger_info *ti = NULL;
102
103	mtx_lock(&audit_trigger_mtx);
104	while (TAILQ_EMPTY(&trigger_list)) {
105		error = msleep(&trigger_list, &audit_trigger_mtx,
106		    PSOCK | PCATCH, "auditd", 0);
107		if (error)
108			break;
109	}
110	if (!error) {
111		ti = TAILQ_FIRST(&trigger_list);
112		TAILQ_REMOVE(&trigger_list, ti, list);
113	}
114	mtx_unlock(&audit_trigger_mtx);
115	if (!error) {
116		error = uiomove(ti, sizeof *ti, uio);
117		free(ti, M_AUDITTRIGGER);
118	}
119	return (error);
120}
121
122static int
123audit_write(struct cdev *dev, struct uio *uio, int ioflag)
124{
125
126	/* Communication is kernel->userspace only. */
127	return (EOPNOTSUPP);
128}
129
130int
131audit_send_trigger(unsigned int trigger)
132{
133	struct trigger_info *ti;
134
135	ti = malloc(sizeof *ti, M_AUDITTRIGGER, M_WAITOK);
136	mtx_lock(&audit_trigger_mtx);
137	if (!audit_isopen) {
138		/* If nobody's listening, we ain't talking. */
139		mtx_unlock(&audit_trigger_mtx);
140		free(ti, M_AUDITTRIGGER);
141		return (ENODEV);
142	}
143	ti->trigger = trigger;
144	TAILQ_INSERT_TAIL(&trigger_list, ti, list);
145	wakeup(&trigger_list);
146	mtx_unlock(&audit_trigger_mtx);
147	return (0);
148}
149
150static struct cdevsw audit_cdevsw = {
151	.d_version =	D_VERSION,
152	.d_open = 	audit_open,
153	.d_close = 	audit_close,
154	.d_read = 	audit_read,
155	.d_write = 	audit_write,
156	.d_name = 	"audit"
157};
158
159void
160audit_trigger_init(void)
161{
162
163	TAILQ_INIT(&trigger_list);
164	mtx_init(&audit_trigger_mtx, "audit_trigger_mtx", NULL, MTX_DEF);
165}
166
167static void
168audit_trigger_cdev_init(void *unused)
169{
170
171	/* Create the special device file. */
172	audit_dev = make_dev(&audit_cdevsw, 0, UID_ROOT, GID_KMEM, 0600,
173	    AUDITDEV_FILENAME);
174}
175
176SYSINIT(audit_trigger_cdev_init, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,
177    audit_trigger_cdev_init, NULL);
178