1 /* audit.c -- Auditing support
2 * Gateway between the kernel (e.g., selinux) and the user-space audit daemon.
3 * System-call specific features have moved to auditsc.c
5 * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 * Written by Rickard E. (Rik) Faith <faith@redhat.com>
24 * Goals: 1) Integrate fully with SELinux.
25 * 2) Minimal run-time overhead:
26 * a) Minimal when syscall auditing is disabled (audit_enable=0).
27 * b) Small when syscall auditing is enabled and no audit record
28 * is generated (defer as much work as possible to record
30 * i) context is allocated,
31 * ii) names from getname are stored without a copy, and
32 * iii) inode information stored from path_lookup.
33 * 3) Ability to disable syscall auditing at boot time (audit=0).
34 * 4) Usable by other parts of the kernel (if audit_log* is called,
35 * then a syscall record will be generated automatically for the
37 * 5) Netlink interface to user-space.
38 * 6) Support low-overhead kernel-based filtering to minimize the
39 * information that must be passed to user-space.
41 * Example user-space utilities: http://people.redhat.com/sgrubb/audit/
44 #include <linux/init.h>
45 #include <asm/atomic.h>
46 #include <asm/types.h>
48 #include <linux/module.h>
50 #include <linux/audit.h>
53 #include <linux/skbuff.h>
54 #include <linux/netlink.h>
56 /* No auditing will take place until audit_initialized != 0.
57 * (Initialization happens after skb_init is called.) */
58 static int audit_initialized;
60 /* No syscall auditing will take place unless audit_enabled != 0. */
63 /* Default state when kernel boots without any parameters. */
64 static int audit_default;
66 /* If auditing cannot proceed, audit_failure selects what happens. */
67 static int audit_failure = AUDIT_FAIL_PRINTK;
69 /* If audit records are to be written to the netlink socket, audit_pid
70 * contains the (non-zero) pid. */
73 /* If audit_limit is non-zero, limit the rate of sending audit records
74 * to that number per second. This prevents DoS attacks, but results in
75 * audit records being dropped. */
76 static int audit_rate_limit;
78 /* Number of outstanding audit_buffers allowed. */
79 static int audit_backlog_limit = 64;
80 static atomic_t audit_backlog = ATOMIC_INIT(0);
82 /* The identity of the user shutting down the audit system. */
83 uid_t audit_sig_uid = -1;
84 pid_t audit_sig_pid = -1;
86 /* Records can be lost in several ways:
87 0) [suppressed in audit_alloc]
88 1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
89 2) out of memory in audit_log_move [alloc_skb]
90 3) suppressed due to audit_rate_limit
91 4) suppressed due to audit_backlog_limit
93 static atomic_t audit_lost = ATOMIC_INIT(0);
95 /* The netlink socket. */
96 static struct sock *audit_sock;
98 /* There are two lists of audit buffers. The txlist contains audit
99 * buffers that cannot be sent immediately to the netlink device because
100 * we are in an irq context (these are sent later in a tasklet).
102 * The second list is a list of pre-allocated audit buffers (if more
103 * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
104 * being placed on the freelist). */
105 static DEFINE_SPINLOCK(audit_txlist_lock);
106 static DEFINE_SPINLOCK(audit_freelist_lock);
107 static int audit_freelist_count = 0;
108 static LIST_HEAD(audit_txlist);
109 static LIST_HEAD(audit_freelist);
111 /* There are three lists of rules -- one to search at task creation
112 * time, one to search at syscall entry time, and another to search at
113 * syscall exit time. */
114 static LIST_HEAD(audit_tsklist);
115 static LIST_HEAD(audit_entlist);
116 static LIST_HEAD(audit_extlist);
118 /* The netlink socket is only to be read by 1 CPU, which lets us assume
119 * that list additions and deletions never happen simultaneiously in
121 static DECLARE_MUTEX(audit_netlink_sem);
123 /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
124 * audit records. Since printk uses a 1024 byte buffer, this buffer
125 * should be at least that large. */
126 #define AUDIT_BUFSIZ 1024
128 /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
129 * audit_freelist. Doing so eliminates many kmalloc/kfree calls. */
130 #define AUDIT_MAXFREE (2*NR_CPUS)
132 /* The audit_buffer is used when formatting an audit record. The caller
133 * locks briefly to get the record off the freelist or to allocate the
134 * buffer, and locks briefly to send the buffer to the netlink layer or
135 * to place it on a transmit queue. Multiple audit_buffers can be in
136 * use simultaneously. */
137 struct audit_buffer {
138 struct list_head list;
139 struct sk_buff *skb; /* formatted skb ready to send */
140 struct audit_context *ctx; /* NULL or associated context */
144 struct list_head list;
145 struct audit_rule rule;
148 static void audit_log_end_irq(struct audit_buffer *ab);
149 static void audit_log_end_fast(struct audit_buffer *ab);
151 static void audit_panic(const char *message)
153 switch (audit_failure)
155 case AUDIT_FAIL_SILENT:
157 case AUDIT_FAIL_PRINTK:
158 printk(KERN_ERR "audit: %s\n", message);
160 case AUDIT_FAIL_PANIC:
161 panic("audit: %s\n", message);
166 static inline int audit_rate_check(void)
168 static unsigned long last_check = 0;
169 static int messages = 0;
170 static DEFINE_SPINLOCK(lock);
173 unsigned long elapsed;
176 if (!audit_rate_limit) return 1;
178 spin_lock_irqsave(&lock, flags);
179 if (++messages < audit_rate_limit) {
183 elapsed = now - last_check;
190 spin_unlock_irqrestore(&lock, flags);
195 /* Emit at least 1 message per second, even if audit_rate_check is
197 void audit_log_lost(const char *message)
199 static unsigned long last_msg = 0;
200 static DEFINE_SPINLOCK(lock);
205 atomic_inc(&audit_lost);
207 print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
210 spin_lock_irqsave(&lock, flags);
212 if (now - last_msg > HZ) {
216 spin_unlock_irqrestore(&lock, flags);
221 "audit: audit_lost=%d audit_backlog=%d"
222 " audit_rate_limit=%d audit_backlog_limit=%d\n",
223 atomic_read(&audit_lost),
224 atomic_read(&audit_backlog),
226 audit_backlog_limit);
227 audit_panic(message);
232 static int audit_set_rate_limit(int limit, uid_t loginuid)
234 int old = audit_rate_limit;
235 audit_rate_limit = limit;
236 audit_log(NULL, "audit_rate_limit=%d old=%d by auid %u",
237 audit_rate_limit, old, loginuid);
241 static int audit_set_backlog_limit(int limit, uid_t loginuid)
243 int old = audit_backlog_limit;
244 audit_backlog_limit = limit;
245 audit_log(NULL, "audit_backlog_limit=%d old=%d by auid %u",
246 audit_backlog_limit, old, loginuid);
250 static int audit_set_enabled(int state, uid_t loginuid)
252 int old = audit_enabled;
253 if (state != 0 && state != 1)
255 audit_enabled = state;
256 audit_log(NULL, "audit_enabled=%d old=%d by auid %u",
257 audit_enabled, old, loginuid);
261 static int audit_set_failure(int state, uid_t loginuid)
263 int old = audit_failure;
264 if (state != AUDIT_FAIL_SILENT
265 && state != AUDIT_FAIL_PRINTK
266 && state != AUDIT_FAIL_PANIC)
268 audit_failure = state;
269 audit_log(NULL, "audit_failure=%d old=%d by auid %u",
270 audit_failure, old, loginuid);
274 void audit_send_reply(int pid, int seq, int type, int done, int multi,
275 void *payload, int size)
278 struct nlmsghdr *nlh;
279 int len = NLMSG_SPACE(size);
281 int flags = multi ? NLM_F_MULTI : 0;
282 int t = done ? NLMSG_DONE : type;
284 skb = alloc_skb(len, GFP_KERNEL);
288 nlh = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
289 nlh->nlmsg_flags = flags;
290 data = NLMSG_DATA(nlh);
291 memcpy(data, payload, size);
292 netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
295 nlmsg_failure: /* Used by NLMSG_PUT */
301 * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
304 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
314 case AUDIT_SIGNAL_INFO:
315 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
319 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
322 default: /* bad msg */
329 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
333 struct audit_status *status_get, status_set;
335 u16 msg_type = nlh->nlmsg_type;
336 uid_t loginuid; /* loginuid of sender */
337 struct audit_sig_info sig_data;
339 err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
343 pid = NETLINK_CREDS(skb)->pid;
344 uid = NETLINK_CREDS(skb)->uid;
345 loginuid = NETLINK_CB(skb).loginuid;
346 seq = nlh->nlmsg_seq;
347 data = NLMSG_DATA(nlh);
351 status_set.enabled = audit_enabled;
352 status_set.failure = audit_failure;
353 status_set.pid = audit_pid;
354 status_set.rate_limit = audit_rate_limit;
355 status_set.backlog_limit = audit_backlog_limit;
356 status_set.lost = atomic_read(&audit_lost);
357 status_set.backlog = atomic_read(&audit_backlog);
358 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
359 &status_set, sizeof(status_set));
362 if (nlh->nlmsg_len < sizeof(struct audit_status))
364 status_get = (struct audit_status *)data;
365 if (status_get->mask & AUDIT_STATUS_ENABLED) {
366 err = audit_set_enabled(status_get->enabled, loginuid);
367 if (err < 0) return err;
369 if (status_get->mask & AUDIT_STATUS_FAILURE) {
370 err = audit_set_failure(status_get->failure, loginuid);
371 if (err < 0) return err;
373 if (status_get->mask & AUDIT_STATUS_PID) {
375 audit_pid = status_get->pid;
376 audit_log(NULL, "audit_pid=%d old=%d by auid %u",
377 audit_pid, old, loginuid);
379 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
380 audit_set_rate_limit(status_get->rate_limit, loginuid);
381 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
382 audit_set_backlog_limit(status_get->backlog_limit,
386 audit_log_type(NULL, AUDIT_USER, pid,
387 "user pid=%d uid=%d length=%d loginuid=%u"
391 - ((char *)data - (char *)nlh)),
392 loginuid, (char *)data);
396 if (nlh->nlmsg_len < sizeof(struct audit_rule))
400 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
401 uid, seq, data, loginuid);
403 case AUDIT_SIGNAL_INFO:
404 sig_data.uid = audit_sig_uid;
405 sig_data.pid = audit_sig_pid;
406 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
407 0, 0, &sig_data, sizeof(sig_data));
414 return err < 0 ? err : 0;
417 /* Get message from skb (based on rtnetlink_rcv_skb). Each message is
418 * processed by audit_receive_msg. Malformed skbs with wrong length are
419 * discarded silently. */
420 static void audit_receive_skb(struct sk_buff *skb)
423 struct nlmsghdr *nlh;
426 while (skb->len >= NLMSG_SPACE(0)) {
427 nlh = (struct nlmsghdr *)skb->data;
428 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
430 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
433 if ((err = audit_receive_msg(skb, nlh))) {
434 netlink_ack(skb, nlh, err);
435 } else if (nlh->nlmsg_flags & NLM_F_ACK)
436 netlink_ack(skb, nlh, 0);
441 /* Receive messages from netlink socket. */
442 static void audit_receive(struct sock *sk, int length)
447 down(&audit_netlink_sem);
449 for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
450 skb = skb_dequeue(&sk->sk_receive_queue);
451 audit_receive_skb(skb);
454 up(&audit_netlink_sem);
457 /* Grab skbuff from the audit_buffer and send to user space. */
458 static inline int audit_log_drain(struct audit_buffer *ab)
460 struct sk_buff *skb = ab->skb;
466 struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
467 nlh->nlmsg_len = skb->len - NLMSG_SPACE(0);
468 skb_get(skb); /* because netlink_* frees */
469 retval = netlink_unicast(audit_sock, skb, audit_pid,
472 if (retval == -EAGAIN &&
473 (atomic_read(&audit_backlog)) < audit_backlog_limit) {
474 audit_log_end_irq(ab);
478 if (retval == -ECONNREFUSED) {
480 "audit: *NO* daemon at audit_pid=%d\n",
484 audit_log_lost("netlink socket too busy");
486 if (!audit_pid) { /* No daemon */
487 int offset = NLMSG_SPACE(0);
488 int len = skb->len - offset;
489 skb->data[offset + len] = '\0';
490 printk(KERN_ERR "%s\n", skb->data + offset);
496 /* Initialize audit support at boot time. */
497 static int __init audit_init(void)
499 printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
500 audit_default ? "enabled" : "disabled");
501 audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
503 audit_panic("cannot initialize netlink socket");
505 audit_initialized = 1;
506 audit_enabled = audit_default;
507 audit_log(NULL, "initialized");
510 __initcall(audit_init);
512 /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */
513 static int __init audit_enable(char *str)
515 audit_default = !!simple_strtol(str, NULL, 0);
516 printk(KERN_INFO "audit: %s%s\n",
517 audit_default ? "enabled" : "disabled",
518 audit_initialized ? "" : " (after initialization)");
519 if (audit_initialized)
520 audit_enabled = audit_default;
524 __setup("audit=", audit_enable);
526 static void audit_buffer_free(struct audit_buffer *ab)
535 atomic_dec(&audit_backlog);
536 spin_lock_irqsave(&audit_freelist_lock, flags);
537 if (++audit_freelist_count > AUDIT_MAXFREE)
540 list_add(&ab->list, &audit_freelist);
541 spin_unlock_irqrestore(&audit_freelist_lock, flags);
544 static struct audit_buffer * audit_buffer_alloc(int gfp_mask)
547 struct audit_buffer *ab = NULL;
549 spin_lock_irqsave(&audit_freelist_lock, flags);
550 if (!list_empty(&audit_freelist)) {
551 ab = list_entry(audit_freelist.next,
552 struct audit_buffer, list);
554 --audit_freelist_count;
556 spin_unlock_irqrestore(&audit_freelist_lock, flags);
559 ab = kmalloc(sizeof(*ab), gfp_mask);
563 atomic_inc(&audit_backlog);
565 ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
571 audit_buffer_free(ab);
575 /* Obtain an audit buffer. This routine does locking to obtain the
576 * audit buffer, but then no locking is required for calls to
577 * audit_log_*format. If the tsk is a task that is currently in a
578 * syscall, then the syscall is marked as auditable and an audit record
579 * will be written at syscall exit. If there is no associated task, tsk
581 struct audit_buffer *audit_log_start(struct audit_context *ctx, int type, int pid)
583 struct audit_buffer *ab = NULL;
586 struct nlmsghdr *nlh;
588 if (!audit_initialized)
591 if (audit_backlog_limit
592 && atomic_read(&audit_backlog) > audit_backlog_limit) {
593 if (audit_rate_check())
595 "audit: audit_backlog=%d > "
596 "audit_backlog_limit=%d\n",
597 atomic_read(&audit_backlog),
598 audit_backlog_limit);
599 audit_log_lost("backlog limit exceeded");
603 ab = audit_buffer_alloc(GFP_ATOMIC);
605 audit_log_lost("out of memory in audit_log_start");
610 nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
611 nlh->nlmsg_type = type;
612 nlh->nlmsg_flags = 0;
613 nlh->nlmsg_pid = pid;
616 if (!audit_get_stamp(ab->ctx, &t, &serial)) {
621 audit_log_format(ab, "audit(%lu.%03lu:%u): ",
622 t.tv_sec, t.tv_nsec/1000000, serial);
627 * audit_expand - expand skb in the audit buffer
630 * Returns 0 (no space) on failed expansion, or available space if
633 static inline int audit_expand(struct audit_buffer *ab, int extra)
635 struct sk_buff *skb = ab->skb;
636 int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
639 audit_log_lost("out of memory in audit_expand");
642 return skb_tailroom(skb);
645 /* Format an audit message into the audit buffer. If there isn't enough
646 * room in the audit buffer, more room will be allocated and vsnprint
647 * will be called a second time. Currently, we assume that a printk
648 * can't format message larger than 1024 bytes, so we don't either. */
649 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
661 avail = skb_tailroom(skb);
663 avail = audit_expand(ab, AUDIT_BUFSIZ);
667 va_copy(args2, args);
668 len = vsnprintf(skb->tail, avail, fmt, args);
670 /* The printk buffer is 1024 bytes long, so if we get
671 * here and AUDIT_BUFSIZ is at least 1024, then we can
672 * log everything that printk could have logged. */
673 avail = audit_expand(ab, max_t(AUDIT_BUFSIZ, 1+len-avail));
676 len = vsnprintf(skb->tail, avail, fmt, args2);
678 skb_put(skb, (len < avail) ? len : avail);
683 /* Format a message into the audit buffer. All the work is done in
684 * audit_log_vformat. */
685 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
692 audit_log_vformat(ab, fmt, args);
696 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len)
700 for (i=0; i<len; i++)
701 audit_log_format(ab, "%02x", buf[i]);
704 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
706 const unsigned char *p = string;
709 if (*p == '"' || *p == ' ' || *p < 0x20 || *p > 0x7f) {
710 audit_log_hex(ab, string, strlen(string));
715 audit_log_format(ab, "\"%s\"", string);
719 /* This is a helper-function to print the d_path without using a static
720 * buffer or allocating another buffer in addition to the one in
722 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
723 struct dentry *dentry, struct vfsmount *vfsmnt)
726 struct sk_buff *skb = ab->skb;
730 audit_log_format(ab, " %s", prefix);
732 avail = skb_tailroom(skb);
733 p = d_path(dentry, vfsmnt, skb->tail, avail);
735 /* FIXME: can we save some information here? */
736 audit_log_format(ab, "<toolong>");
738 /* path isn't at start of buffer */
739 len = ((char *)skb->tail + avail - 1) - p;
740 memmove(skb->tail, p, len);
745 /* Remove queued messages from the audit_txlist and send them to userspace. */
746 static void audit_tasklet_handler(unsigned long arg)
749 struct audit_buffer *ab;
752 spin_lock_irqsave(&audit_txlist_lock, flags);
753 list_splice_init(&audit_txlist, &list);
754 spin_unlock_irqrestore(&audit_txlist_lock, flags);
756 while (!list_empty(&list)) {
757 ab = list_entry(list.next, struct audit_buffer, list);
759 audit_log_end_fast(ab);
763 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
765 /* The netlink_* functions cannot be called inside an irq context, so
766 * the audit buffer is places on a queue and a tasklet is scheduled to
767 * remove them from the queue outside the irq context. May be called in
769 static void audit_log_end_irq(struct audit_buffer *ab)
775 spin_lock_irqsave(&audit_txlist_lock, flags);
776 list_add_tail(&ab->list, &audit_txlist);
777 spin_unlock_irqrestore(&audit_txlist_lock, flags);
779 tasklet_schedule(&audit_tasklet);
782 /* Send the message in the audit buffer directly to user space. May not
783 * be called in an irq context. */
784 static void audit_log_end_fast(struct audit_buffer *ab)
789 if (!audit_rate_check()) {
790 audit_log_lost("rate limit exceeded");
792 if (audit_log_drain(ab))
795 audit_buffer_free(ab);
798 /* Send or queue the message in the audit buffer, depending on the
799 * current context. (A convenience function that may be called in any
801 void audit_log_end(struct audit_buffer *ab)
804 audit_log_end_irq(ab);
806 audit_log_end_fast(ab);
809 /* Log an audit record. This is a convenience function that calls
810 * audit_log_start, audit_log_vformat, and audit_log_end. It may be
811 * called in any context. */
812 void audit_log_type(struct audit_context *ctx, int type, int pid,
813 const char *fmt, ...)
815 struct audit_buffer *ab;
818 ab = audit_log_start(ctx, type, pid);
821 audit_log_vformat(ab, fmt, args);