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 /* Records can be lost in several ways:
83 0) [suppressed in audit_alloc]
84 1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
85 2) out of memory in audit_log_move [alloc_skb]
86 3) suppressed due to audit_rate_limit
87 4) suppressed due to audit_backlog_limit
89 static atomic_t audit_lost = ATOMIC_INIT(0);
91 /* The netlink socket. */
92 static struct sock *audit_sock;
94 /* There are two lists of audit buffers. The txlist contains audit
95 * buffers that cannot be sent immediately to the netlink device because
96 * we are in an irq context (these are sent later in a tasklet).
98 * The second list is a list of pre-allocated audit buffers (if more
99 * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
100 * being placed on the freelist). */
101 static DEFINE_SPINLOCK(audit_txlist_lock);
102 static DEFINE_SPINLOCK(audit_freelist_lock);
103 static int audit_freelist_count = 0;
104 static LIST_HEAD(audit_txlist);
105 static LIST_HEAD(audit_freelist);
107 /* There are three lists of rules -- one to search at task creation
108 * time, one to search at syscall entry time, and another to search at
109 * syscall exit time. */
110 static LIST_HEAD(audit_tsklist);
111 static LIST_HEAD(audit_entlist);
112 static LIST_HEAD(audit_extlist);
114 /* The netlink socket is only to be read by 1 CPU, which lets us assume
115 * that list additions and deletions never happen simultaneiously in
117 static DECLARE_MUTEX(audit_netlink_sem);
119 /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
120 * audit records. Since printk uses a 1024 byte buffer, this buffer
121 * should be at least that large. */
122 #define AUDIT_BUFSIZ 1024
124 /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
125 * audit_freelist. Doing so eliminates many kmalloc/kfree calls. */
126 #define AUDIT_MAXFREE (2*NR_CPUS)
128 /* The audit_buffer is used when formatting an audit record. The caller
129 * locks briefly to get the record off the freelist or to allocate the
130 * buffer, and locks briefly to send the buffer to the netlink layer or
131 * to place it on a transmit queue. Multiple audit_buffers can be in
132 * use simultaneously. */
133 struct audit_buffer {
134 struct list_head list;
135 struct sk_buff_head sklist; /* formatted skbs ready to send */
136 struct audit_context *ctx; /* NULL or associated context */
137 int len; /* used area of tmp */
138 char tmp[AUDIT_BUFSIZ];
140 /* Pointer to header and contents */
141 struct nlmsghdr *nlh;
145 int count; /* Times requeued */
148 void audit_set_type(struct audit_buffer *ab, int type)
154 struct list_head list;
155 struct audit_rule rule;
158 static void audit_log_end_irq(struct audit_buffer *ab);
159 static void audit_log_end_fast(struct audit_buffer *ab);
161 static void audit_panic(const char *message)
163 switch (audit_failure)
165 case AUDIT_FAIL_SILENT:
167 case AUDIT_FAIL_PRINTK:
168 printk(KERN_ERR "audit: %s\n", message);
170 case AUDIT_FAIL_PANIC:
171 panic("audit: %s\n", message);
176 static inline int audit_rate_check(void)
178 static unsigned long last_check = 0;
179 static int messages = 0;
180 static DEFINE_SPINLOCK(lock);
183 unsigned long elapsed;
186 if (!audit_rate_limit) return 1;
188 spin_lock_irqsave(&lock, flags);
189 if (++messages < audit_rate_limit) {
193 elapsed = now - last_check;
200 spin_unlock_irqrestore(&lock, flags);
205 /* Emit at least 1 message per second, even if audit_rate_check is
207 void audit_log_lost(const char *message)
209 static unsigned long last_msg = 0;
210 static DEFINE_SPINLOCK(lock);
215 atomic_inc(&audit_lost);
217 print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
220 spin_lock_irqsave(&lock, flags);
222 if (now - last_msg > HZ) {
226 spin_unlock_irqrestore(&lock, flags);
231 "audit: audit_lost=%d audit_backlog=%d"
232 " audit_rate_limit=%d audit_backlog_limit=%d\n",
233 atomic_read(&audit_lost),
234 atomic_read(&audit_backlog),
236 audit_backlog_limit);
237 audit_panic(message);
242 static int audit_set_rate_limit(int limit, uid_t loginuid)
244 int old = audit_rate_limit;
245 audit_rate_limit = limit;
246 audit_log(NULL, "audit_rate_limit=%d old=%d by auid %u",
247 audit_rate_limit, old, loginuid);
251 static int audit_set_backlog_limit(int limit, uid_t loginuid)
253 int old = audit_backlog_limit;
254 audit_backlog_limit = limit;
255 audit_log(NULL, "audit_backlog_limit=%d old=%d by auid %u",
256 audit_backlog_limit, old, loginuid);
260 static int audit_set_enabled(int state, uid_t loginuid)
262 int old = audit_enabled;
263 if (state != 0 && state != 1)
265 audit_enabled = state;
266 audit_log(NULL, "audit_enabled=%d old=%d by auid %u",
267 audit_enabled, old, loginuid);
271 static int audit_set_failure(int state, uid_t loginuid)
273 int old = audit_failure;
274 if (state != AUDIT_FAIL_SILENT
275 && state != AUDIT_FAIL_PRINTK
276 && state != AUDIT_FAIL_PANIC)
278 audit_failure = state;
279 audit_log(NULL, "audit_failure=%d old=%d by auid %u",
280 audit_failure, old, loginuid);
285 void audit_send_reply(int pid, int seq, int type, int done, int multi,
286 void *payload, int size)
289 struct nlmsghdr *nlh;
290 int len = NLMSG_SPACE(size);
292 int flags = multi ? NLM_F_MULTI : 0;
293 int t = done ? NLMSG_DONE : type;
295 skb = alloc_skb(len, GFP_KERNEL);
299 nlh = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
300 nlh->nlmsg_flags = flags;
301 data = NLMSG_DATA(nlh);
302 memcpy(data, payload, size);
303 netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
306 nlmsg_failure: /* Used by NLMSG_PUT */
312 * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
315 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
325 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
329 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
332 default: /* bad msg */
339 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
343 struct audit_status *status_get, status_set;
345 struct audit_buffer *ab;
346 u16 msg_type = nlh->nlmsg_type;
347 uid_t loginuid; /* loginuid of sender */
349 err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
353 pid = NETLINK_CREDS(skb)->pid;
354 uid = NETLINK_CREDS(skb)->uid;
355 loginuid = NETLINK_CB(skb).loginuid;
356 seq = nlh->nlmsg_seq;
357 data = NLMSG_DATA(nlh);
361 status_set.enabled = audit_enabled;
362 status_set.failure = audit_failure;
363 status_set.pid = audit_pid;
364 status_set.rate_limit = audit_rate_limit;
365 status_set.backlog_limit = audit_backlog_limit;
366 status_set.lost = atomic_read(&audit_lost);
367 status_set.backlog = atomic_read(&audit_backlog);
368 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
369 &status_set, sizeof(status_set));
372 if (nlh->nlmsg_len < sizeof(struct audit_status))
374 status_get = (struct audit_status *)data;
375 if (status_get->mask & AUDIT_STATUS_ENABLED) {
376 err = audit_set_enabled(status_get->enabled, loginuid);
377 if (err < 0) return err;
379 if (status_get->mask & AUDIT_STATUS_FAILURE) {
380 err = audit_set_failure(status_get->failure, loginuid);
381 if (err < 0) return err;
383 if (status_get->mask & AUDIT_STATUS_PID) {
385 audit_pid = status_get->pid;
386 audit_log(NULL, "audit_pid=%d old=%d by auid %u",
387 audit_pid, old, loginuid);
389 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
390 audit_set_rate_limit(status_get->rate_limit, loginuid);
391 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
392 audit_set_backlog_limit(status_get->backlog_limit,
396 ab = audit_log_start(NULL);
398 break; /* audit_panic has been called */
400 "user pid=%d uid=%d length=%d loginuid=%u"
404 - ((char *)data - (char *)nlh)),
405 loginuid, (char *)data);
406 ab->type = AUDIT_USER;
412 if (nlh->nlmsg_len < sizeof(struct audit_rule))
416 #ifdef CONFIG_AUDITSYSCALL
417 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
418 uid, seq, data, loginuid);
428 return err < 0 ? err : 0;
431 /* Get message from skb (based on rtnetlink_rcv_skb). Each message is
432 * processed by audit_receive_msg. Malformed skbs with wrong length are
433 * discarded silently. */
434 static int audit_receive_skb(struct sk_buff *skb)
437 struct nlmsghdr *nlh;
440 while (skb->len >= NLMSG_SPACE(0)) {
441 nlh = (struct nlmsghdr *)skb->data;
442 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
444 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
447 if ((err = audit_receive_msg(skb, nlh))) {
448 netlink_ack(skb, nlh, err);
449 } else if (nlh->nlmsg_flags & NLM_F_ACK)
450 netlink_ack(skb, nlh, 0);
456 /* Receive messages from netlink socket. */
457 static void audit_receive(struct sock *sk, int length)
461 if (down_trylock(&audit_netlink_sem))
464 /* FIXME: this must not cause starvation */
465 while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
466 if (audit_receive_skb(skb) && skb->len)
467 skb_queue_head(&sk->sk_receive_queue, skb);
471 up(&audit_netlink_sem);
474 /* Move data from tmp buffer into an skb. This is an extra copy, and
475 * that is unfortunate. However, the copy will only occur when a record
476 * is being written to user space, which is already a high-overhead
477 * operation. (Elimination of the copy is possible, for example, by
478 * writing directly into a pre-allocated skb, at the cost of wasting
480 static void audit_log_move(struct audit_buffer *ab)
484 int extra = ab->nlh ? 0 : NLMSG_SPACE(0);
486 /* possible resubmission */
490 skb = skb_peek(&ab->sklist);
491 if (!skb || skb_tailroom(skb) <= ab->len + extra) {
492 skb = alloc_skb(2 * ab->len + extra, GFP_ATOMIC);
494 ab->len = 0; /* Lose information in ab->tmp */
495 audit_log_lost("out of memory in audit_log_move");
498 __skb_queue_tail(&ab->sklist, skb);
500 ab->nlh = (struct nlmsghdr *)skb_put(skb,
503 start = skb_put(skb, ab->len);
504 memcpy(start, ab->tmp, ab->len);
508 /* Iterate over the skbuff in the audit_buffer, sending their contents
510 static inline int audit_log_drain(struct audit_buffer *ab)
514 while ((skb = skb_dequeue(&ab->sklist))) {
519 ab->nlh->nlmsg_len = ab->total;
520 ab->nlh->nlmsg_type = ab->type;
521 ab->nlh->nlmsg_flags = 0;
522 ab->nlh->nlmsg_seq = 0;
523 ab->nlh->nlmsg_pid = ab->pid;
525 skb_get(skb); /* because netlink_* frees */
526 retval = netlink_unicast(audit_sock, skb, audit_pid,
529 if (retval == -EAGAIN && ab->count < 5) {
531 skb_queue_tail(&ab->sklist, skb);
532 audit_log_end_irq(ab);
536 if (retval == -ECONNREFUSED) {
538 "audit: *NO* daemon at audit_pid=%d\n",
542 audit_log_lost("netlink socket too busy");
544 if (!audit_pid) { /* No daemon */
545 int offset = ab->nlh ? NLMSG_SPACE(0) : 0;
546 int len = skb->len - offset;
547 skb->data[offset + len] = '\0';
548 printk(KERN_ERR "%s\n", skb->data + offset);
556 /* Initialize audit support at boot time. */
557 static int __init audit_init(void)
559 printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
560 audit_default ? "enabled" : "disabled");
561 audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
563 audit_panic("cannot initialize netlink socket");
565 audit_initialized = 1;
566 audit_enabled = audit_default;
567 audit_log(NULL, "initialized");
572 /* Without CONFIG_NET, we have no skbuffs. For now, print what we have
574 static void audit_log_move(struct audit_buffer *ab)
576 printk(KERN_ERR "%*.*s\n", ab->len, ab->len, ab->tmp);
580 static inline int audit_log_drain(struct audit_buffer *ab)
585 /* Initialize audit support at boot time. */
586 int __init audit_init(void)
588 printk(KERN_INFO "audit: initializing WITHOUT netlink support\n");
592 audit_initialized = 1;
593 audit_enabled = audit_default;
594 audit_log(NULL, "initialized");
599 __initcall(audit_init);
601 /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */
602 static int __init audit_enable(char *str)
604 audit_default = !!simple_strtol(str, NULL, 0);
605 printk(KERN_INFO "audit: %s%s\n",
606 audit_default ? "enabled" : "disabled",
607 audit_initialized ? "" : " (after initialization)");
608 if (audit_initialized)
609 audit_enabled = audit_default;
613 __setup("audit=", audit_enable);
616 /* Obtain an audit buffer. This routine does locking to obtain the
617 * audit buffer, but then no locking is required for calls to
618 * audit_log_*format. If the tsk is a task that is currently in a
619 * syscall, then the syscall is marked as auditable and an audit record
620 * will be written at syscall exit. If there is no associated task, tsk
622 struct audit_buffer *audit_log_start(struct audit_context *ctx)
624 struct audit_buffer *ab = NULL;
629 if (!audit_initialized)
632 if (audit_backlog_limit
633 && atomic_read(&audit_backlog) > audit_backlog_limit) {
634 if (audit_rate_check())
636 "audit: audit_backlog=%d > "
637 "audit_backlog_limit=%d\n",
638 atomic_read(&audit_backlog),
639 audit_backlog_limit);
640 audit_log_lost("backlog limit exceeded");
644 spin_lock_irqsave(&audit_freelist_lock, flags);
645 if (!list_empty(&audit_freelist)) {
646 ab = list_entry(audit_freelist.next,
647 struct audit_buffer, list);
649 --audit_freelist_count;
651 spin_unlock_irqrestore(&audit_freelist_lock, flags);
654 ab = kmalloc(sizeof(*ab), GFP_ATOMIC);
656 audit_log_lost("out of memory in audit_log_start");
660 atomic_inc(&audit_backlog);
661 skb_queue_head_init(&ab->sklist);
667 ab->type = AUDIT_KERNEL;
671 #ifdef CONFIG_AUDITSYSCALL
673 audit_get_stamp(ab->ctx, &t, &serial);
680 audit_log_format(ab, "audit(%lu.%03lu:%u): ",
681 t.tv_sec, t.tv_nsec/1000000, serial);
686 /* Format an audit message into the audit buffer. If there isn't enough
687 * room in the audit buffer, more room will be allocated and vsnprint
688 * will be called a second time. Currently, we assume that a printk
689 * can't format message larger than 1024 bytes, so we don't either. */
690 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
698 avail = sizeof(ab->tmp) - ab->len;
701 avail = sizeof(ab->tmp) - ab->len;
703 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
705 /* The printk buffer is 1024 bytes long, so if we get
706 * here and AUDIT_BUFSIZ is at least 1024, then we can
707 * log everything that printk could have logged. */
709 avail = sizeof(ab->tmp) - ab->len;
710 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
712 ab->len += (len < avail) ? len : avail;
713 ab->total += (len < avail) ? len : avail;
716 /* Format a message into the audit buffer. All the work is done in
717 * audit_log_vformat. */
718 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
725 audit_log_vformat(ab, fmt, args);
729 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len)
733 for (i=0; i<len; i++)
734 audit_log_format(ab, "%02x", buf[i]);
737 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
739 const unsigned char *p = string;
742 if (*p == '"' || *p == ' ' || *p < 0x20 || *p > 0x7f) {
743 audit_log_hex(ab, string, strlen(string));
748 audit_log_format(ab, "\"%s\"", string);
752 /* This is a helper-function to print the d_path without using a static
753 * buffer or allocating another buffer in addition to the one in
755 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
756 struct dentry *dentry, struct vfsmount *vfsmnt)
761 if (prefix) audit_log_format(ab, " %s", prefix);
765 avail = sizeof(ab->tmp) - ab->len;
766 p = d_path(dentry, vfsmnt, ab->tmp + ab->len, avail);
768 /* FIXME: can we save some information here? */
769 audit_log_format(ab, "<toolong>");
771 /* path isn't at start of buffer */
772 len = (ab->tmp + sizeof(ab->tmp) - 1) - p;
773 memmove(ab->tmp + ab->len, p, len);
779 /* Remove queued messages from the audit_txlist and send them to userspace. */
780 static void audit_tasklet_handler(unsigned long arg)
783 struct audit_buffer *ab;
786 spin_lock_irqsave(&audit_txlist_lock, flags);
787 list_splice_init(&audit_txlist, &list);
788 spin_unlock_irqrestore(&audit_txlist_lock, flags);
790 while (!list_empty(&list)) {
791 ab = list_entry(list.next, struct audit_buffer, list);
793 audit_log_end_fast(ab);
797 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
799 /* The netlink_* functions cannot be called inside an irq context, so
800 * the audit buffer is places on a queue and a tasklet is scheduled to
801 * remove them from the queue outside the irq context. May be called in
803 static void audit_log_end_irq(struct audit_buffer *ab)
809 spin_lock_irqsave(&audit_txlist_lock, flags);
810 list_add_tail(&ab->list, &audit_txlist);
811 spin_unlock_irqrestore(&audit_txlist_lock, flags);
813 tasklet_schedule(&audit_tasklet);
816 /* Send the message in the audit buffer directly to user space. May not
817 * be called in an irq context. */
818 static void audit_log_end_fast(struct audit_buffer *ab)
825 if (!audit_rate_check()) {
826 audit_log_lost("rate limit exceeded");
829 if (audit_log_drain(ab))
833 atomic_dec(&audit_backlog);
834 spin_lock_irqsave(&audit_freelist_lock, flags);
835 if (++audit_freelist_count > AUDIT_MAXFREE)
838 list_add(&ab->list, &audit_freelist);
839 spin_unlock_irqrestore(&audit_freelist_lock, flags);
842 /* Send or queue the message in the audit buffer, depending on the
843 * current context. (A convenience function that may be called in any
845 void audit_log_end(struct audit_buffer *ab)
848 audit_log_end_irq(ab);
850 audit_log_end_fast(ab);
853 /* Log an audit record. This is a convenience function that calls
854 * audit_log_start, audit_log_vformat, and audit_log_end. It may be
855 * called in any context. */
856 void audit_log(struct audit_context *ctx, const char *fmt, ...)
858 struct audit_buffer *ab;
861 ab = audit_log_start(ctx);
864 audit_log_vformat(ab, fmt, args);