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
29 #include <sys/param.h>
30 #include <sys/conf.h>
31 #include <sys/kernel.h>
32 #include <sys/lock.h>
33 #include <sys/malloc.h>
34 #include <sys/mutex.h>
35 #include <sys/poll.h>
36 #include <sys/proc.h>
37 #include <sys/queue.h>
38 #include <sys/selinfo.h>
39 #include <sys/systm.h>
40 #include <sys/uio.h>
41
42 #include <security/audit/audit.h>
43 #include <security/audit/audit_private.h>
44
45 /*
46 * Structures and operations to support the basic character special device
47 * used to communicate with userland. /dev/audit reliably delivers one-byte
48 * messages to a listening application (or discards them if there is no
49 * listening application).
50 */
51 struct trigger_info {
52 unsigned int trigger;
53 STAILQ_ENTRY(trigger_info) list;
54 };
55
56 static MALLOC_DEFINE(M_AUDITTRIGGER, "audit_trigger", "Audit trigger events");
57 static struct cdev *audit_dev;
58 static int audit_isopen = 0;
59 static STAILQ_HEAD(, trigger_info) trigger_list;
60 static struct mtx audit_trigger_mtx;
61 static struct selinfo audit_trigger_rsel;
62
63 static int
audit_open(struct cdev * dev,int oflags,int devtype,struct thread * td)64 audit_open(struct cdev *dev, int oflags, int devtype, struct thread *td)
65 {
66 int error;
67
68 /* Only one process may open the device at a time. */
69 mtx_lock(&audit_trigger_mtx);
70 if (!audit_isopen) {
71 error = 0;
72 audit_isopen = 1;
73 } else
74 error = EBUSY;
75 mtx_unlock(&audit_trigger_mtx);
76
77 return (error);
78 }
79
80 static int
audit_close(struct cdev * dev,int fflag,int devtype,struct thread * td)81 audit_close(struct cdev *dev, int fflag, int devtype, struct thread *td)
82 {
83 struct trigger_info *ti;
84
85 /* Flush the queue of pending trigger events. */
86 mtx_lock(&audit_trigger_mtx);
87 audit_isopen = 0;
88 while (!STAILQ_EMPTY(&trigger_list)) {
89 ti = STAILQ_FIRST(&trigger_list);
90 STAILQ_REMOVE_HEAD(&trigger_list, list);
91 free(ti, M_AUDITTRIGGER);
92 }
93 mtx_unlock(&audit_trigger_mtx);
94
95 return (0);
96 }
97
98 static int
audit_read(struct cdev * dev,struct uio * uio,int ioflag)99 audit_read(struct cdev *dev, struct uio *uio, int ioflag)
100 {
101 int error = 0;
102 struct trigger_info *ti = NULL;
103
104 mtx_lock(&audit_trigger_mtx);
105 while (STAILQ_EMPTY(&trigger_list)) {
106 error = msleep(&trigger_list, &audit_trigger_mtx,
107 PSOCK | PCATCH, "auditd", 0);
108 if (error)
109 break;
110 }
111 if (!error) {
112 ti = STAILQ_FIRST(&trigger_list);
113 STAILQ_REMOVE_HEAD(&trigger_list, list);
114 }
115 mtx_unlock(&audit_trigger_mtx);
116 if (!error) {
117 error = uiomove(&ti->trigger, sizeof(ti->trigger), uio);
118 free(ti, M_AUDITTRIGGER);
119 }
120 return (error);
121 }
122
123 static int
audit_write(struct cdev * dev,struct uio * uio,int ioflag)124 audit_write(struct cdev *dev, struct uio *uio, int ioflag)
125 {
126
127 /* Communication is kernel->userspace only. */
128 return (EOPNOTSUPP);
129 }
130
131 static int
audit_poll(struct cdev * dev,int events,struct thread * td)132 audit_poll(struct cdev *dev, int events, struct thread *td)
133 {
134 int revents = 0;
135
136 if (events & (POLLIN | POLLRDNORM)) {
137 mtx_lock(&audit_trigger_mtx);
138 if (!STAILQ_EMPTY(&trigger_list))
139 revents = events & (POLLIN | POLLRDNORM);
140 else
141 selrecord(td, &audit_trigger_rsel);
142 mtx_unlock(&audit_trigger_mtx);
143 }
144 return (revents);
145 }
146
147 int
audit_send_trigger(unsigned int trigger)148 audit_send_trigger(unsigned int trigger)
149 {
150 struct trigger_info *ti;
151
152 ti = malloc(sizeof *ti, M_AUDITTRIGGER, M_WAITOK);
153 mtx_lock(&audit_trigger_mtx);
154 if (!audit_isopen) {
155 /* If nobody's listening, we ain't talking. */
156 mtx_unlock(&audit_trigger_mtx);
157 free(ti, M_AUDITTRIGGER);
158 return (ENODEV);
159 }
160 ti->trigger = trigger;
161 STAILQ_INSERT_TAIL(&trigger_list, ti, list);
162 selwakeup(&audit_trigger_rsel);
163 wakeup(&trigger_list);
164 mtx_unlock(&audit_trigger_mtx);
165 return (0);
166 }
167
168 static struct cdevsw audit_cdevsw = {
169 .d_version = D_VERSION,
170 .d_open = audit_open,
171 .d_close = audit_close,
172 .d_read = audit_read,
173 .d_write = audit_write,
174 .d_poll = audit_poll,
175 .d_name = "audit"
176 };
177
178 void
audit_trigger_init(void)179 audit_trigger_init(void)
180 {
181
182 STAILQ_INIT(&trigger_list);
183 mtx_init(&audit_trigger_mtx, "audit_trigger_mtx", NULL, MTX_DEF);
184 }
185
186 static void
audit_trigger_cdev_init(void * unused)187 audit_trigger_cdev_init(void *unused)
188 {
189
190 /* Create the special device file. */
191 audit_dev = make_dev(&audit_cdevsw, 0, UID_ROOT, GID_KMEM, 0600,
192 AUDITDEV_FILENAME);
193 }
194
195 SYSINIT(audit_trigger_cdev_init, SI_SUB_DRIVERS, SI_ORDER_MIDDLE,
196 audit_trigger_cdev_init, NULL);
197