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 */
143 void audit_set_type(struct audit_buffer *ab, int type)
145 struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
146 nlh->nlmsg_type = type;
149 static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
151 struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
152 nlh->nlmsg_pid = pid;
156 struct list_head list;
157 struct audit_rule rule;
160 static void audit_log_end_irq(struct audit_buffer *ab);
161 static void audit_log_end_fast(struct audit_buffer *ab);
163 static void audit_panic(const char *message)
165 switch (audit_failure)
167 case AUDIT_FAIL_SILENT:
169 case AUDIT_FAIL_PRINTK:
170 printk(KERN_ERR "audit: %s\n", message);
172 case AUDIT_FAIL_PANIC:
173 panic("audit: %s\n", message);
178 static inline int audit_rate_check(void)
180 static unsigned long last_check = 0;
181 static int messages = 0;
182 static DEFINE_SPINLOCK(lock);
185 unsigned long elapsed;
188 if (!audit_rate_limit) return 1;
190 spin_lock_irqsave(&lock, flags);
191 if (++messages < audit_rate_limit) {
195 elapsed = now - last_check;
202 spin_unlock_irqrestore(&lock, flags);
207 /* Emit at least 1 message per second, even if audit_rate_check is
209 void audit_log_lost(const char *message)
211 static unsigned long last_msg = 0;
212 static DEFINE_SPINLOCK(lock);
217 atomic_inc(&audit_lost);
219 print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
222 spin_lock_irqsave(&lock, flags);
224 if (now - last_msg > HZ) {
228 spin_unlock_irqrestore(&lock, flags);
233 "audit: audit_lost=%d audit_backlog=%d"
234 " audit_rate_limit=%d audit_backlog_limit=%d\n",
235 atomic_read(&audit_lost),
236 atomic_read(&audit_backlog),
238 audit_backlog_limit);
239 audit_panic(message);
244 static int audit_set_rate_limit(int limit, uid_t loginuid)
246 int old = audit_rate_limit;
247 audit_rate_limit = limit;
248 audit_log(NULL, "audit_rate_limit=%d old=%d by auid %u",
249 audit_rate_limit, old, loginuid);
253 static int audit_set_backlog_limit(int limit, uid_t loginuid)
255 int old = audit_backlog_limit;
256 audit_backlog_limit = limit;
257 audit_log(NULL, "audit_backlog_limit=%d old=%d by auid %u",
258 audit_backlog_limit, old, loginuid);
262 static int audit_set_enabled(int state, uid_t loginuid)
264 int old = audit_enabled;
265 if (state != 0 && state != 1)
267 audit_enabled = state;
268 audit_log(NULL, "audit_enabled=%d old=%d by auid %u",
269 audit_enabled, old, loginuid);
273 static int audit_set_failure(int state, uid_t loginuid)
275 int old = audit_failure;
276 if (state != AUDIT_FAIL_SILENT
277 && state != AUDIT_FAIL_PRINTK
278 && state != AUDIT_FAIL_PANIC)
280 audit_failure = state;
281 audit_log(NULL, "audit_failure=%d old=%d by auid %u",
282 audit_failure, old, loginuid);
287 void audit_send_reply(int pid, int seq, int type, int done, int multi,
288 void *payload, int size)
291 struct nlmsghdr *nlh;
292 int len = NLMSG_SPACE(size);
294 int flags = multi ? NLM_F_MULTI : 0;
295 int t = done ? NLMSG_DONE : type;
297 skb = alloc_skb(len, GFP_KERNEL);
301 nlh = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
302 nlh->nlmsg_flags = flags;
303 data = NLMSG_DATA(nlh);
304 memcpy(data, payload, size);
305 netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
308 nlmsg_failure: /* Used by NLMSG_PUT */
314 * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
317 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
327 case AUDIT_SIGNAL_INFO:
328 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
332 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
335 default: /* bad msg */
342 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
346 struct audit_status *status_get, status_set;
348 struct audit_buffer *ab;
349 u16 msg_type = nlh->nlmsg_type;
350 uid_t loginuid; /* loginuid of sender */
351 struct audit_sig_info sig_data;
353 err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
357 pid = NETLINK_CREDS(skb)->pid;
358 uid = NETLINK_CREDS(skb)->uid;
359 loginuid = NETLINK_CB(skb).loginuid;
360 seq = nlh->nlmsg_seq;
361 data = NLMSG_DATA(nlh);
365 status_set.enabled = audit_enabled;
366 status_set.failure = audit_failure;
367 status_set.pid = audit_pid;
368 status_set.rate_limit = audit_rate_limit;
369 status_set.backlog_limit = audit_backlog_limit;
370 status_set.lost = atomic_read(&audit_lost);
371 status_set.backlog = atomic_read(&audit_backlog);
372 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
373 &status_set, sizeof(status_set));
376 if (nlh->nlmsg_len < sizeof(struct audit_status))
378 status_get = (struct audit_status *)data;
379 if (status_get->mask & AUDIT_STATUS_ENABLED) {
380 err = audit_set_enabled(status_get->enabled, loginuid);
381 if (err < 0) return err;
383 if (status_get->mask & AUDIT_STATUS_FAILURE) {
384 err = audit_set_failure(status_get->failure, loginuid);
385 if (err < 0) return err;
387 if (status_get->mask & AUDIT_STATUS_PID) {
389 audit_pid = status_get->pid;
390 audit_log(NULL, "audit_pid=%d old=%d by auid %u",
391 audit_pid, old, loginuid);
393 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
394 audit_set_rate_limit(status_get->rate_limit, loginuid);
395 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
396 audit_set_backlog_limit(status_get->backlog_limit,
400 ab = audit_log_start(NULL);
402 break; /* audit_panic has been called */
404 "user pid=%d uid=%d length=%d loginuid=%u"
408 - ((char *)data - (char *)nlh)),
409 loginuid, (char *)data);
410 audit_set_type(ab, AUDIT_USER);
411 audit_set_pid(ab, pid);
416 if (nlh->nlmsg_len < sizeof(struct audit_rule))
420 #ifdef CONFIG_AUDITSYSCALL
421 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
422 uid, seq, data, loginuid);
427 case AUDIT_SIGNAL_INFO:
428 sig_data.uid = audit_sig_uid;
429 sig_data.pid = audit_sig_pid;
430 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
431 0, 0, &sig_data, sizeof(sig_data));
438 return err < 0 ? err : 0;
441 /* Get message from skb (based on rtnetlink_rcv_skb). Each message is
442 * processed by audit_receive_msg. Malformed skbs with wrong length are
443 * discarded silently. */
444 static void audit_receive_skb(struct sk_buff *skb)
447 struct nlmsghdr *nlh;
450 while (skb->len >= NLMSG_SPACE(0)) {
451 nlh = (struct nlmsghdr *)skb->data;
452 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
454 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
457 if ((err = audit_receive_msg(skb, nlh))) {
458 netlink_ack(skb, nlh, err);
459 } else if (nlh->nlmsg_flags & NLM_F_ACK)
460 netlink_ack(skb, nlh, 0);
465 /* Receive messages from netlink socket. */
466 static void audit_receive(struct sock *sk, int length)
471 down(&audit_netlink_sem);
473 for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
474 skb = skb_dequeue(&sk->sk_receive_queue);
475 audit_receive_skb(skb);
478 up(&audit_netlink_sem);
481 /* Grab skbuff from the audit_buffer and send to user space. */
482 static inline int audit_log_drain(struct audit_buffer *ab)
484 struct sk_buff *skb = ab->skb;
490 struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
491 nlh->nlmsg_len = skb->len - sizeof(*nlh);
492 skb_get(skb); /* because netlink_* frees */
493 retval = netlink_unicast(audit_sock, skb, audit_pid,
496 if (retval == -EAGAIN &&
497 (atomic_read(&audit_backlog)) < audit_backlog_limit) {
498 audit_log_end_irq(ab);
502 if (retval == -ECONNREFUSED) {
504 "audit: *NO* daemon at audit_pid=%d\n",
508 audit_log_lost("netlink socket too busy");
510 if (!audit_pid) { /* No daemon */
511 int offset = NLMSG_SPACE(0);
512 int len = skb->len - offset;
513 skb->data[offset + len] = '\0';
514 printk(KERN_ERR "%s\n", skb->data + offset);
520 /* Initialize audit support at boot time. */
521 static int __init audit_init(void)
523 printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
524 audit_default ? "enabled" : "disabled");
525 audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
527 audit_panic("cannot initialize netlink socket");
529 audit_initialized = 1;
530 audit_enabled = audit_default;
531 audit_log(NULL, "initialized");
536 /* Without CONFIG_NET, we have no skbuffs. For now, print what we have
538 static void audit_log_move(struct audit_buffer *ab)
540 printk(KERN_ERR "%*.*s\n", ab->len, ab->len, ab->tmp);
544 static inline int audit_log_drain(struct audit_buffer *ab)
549 /* Initialize audit support at boot time. */
550 int __init audit_init(void)
552 printk(KERN_INFO "audit: initializing WITHOUT netlink support\n");
556 audit_initialized = 1;
557 audit_enabled = audit_default;
558 audit_log(NULL, "initialized");
563 __initcall(audit_init);
565 /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */
566 static int __init audit_enable(char *str)
568 audit_default = !!simple_strtol(str, NULL, 0);
569 printk(KERN_INFO "audit: %s%s\n",
570 audit_default ? "enabled" : "disabled",
571 audit_initialized ? "" : " (after initialization)");
572 if (audit_initialized)
573 audit_enabled = audit_default;
577 __setup("audit=", audit_enable);
579 static void audit_buffer_free(struct audit_buffer *ab)
588 atomic_dec(&audit_backlog);
589 spin_lock_irqsave(&audit_freelist_lock, flags);
590 if (++audit_freelist_count > AUDIT_MAXFREE)
593 list_add(&ab->list, &audit_freelist);
594 spin_unlock_irqrestore(&audit_freelist_lock, flags);
597 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
601 struct audit_buffer *ab = NULL;
602 struct nlmsghdr *nlh;
604 spin_lock_irqsave(&audit_freelist_lock, flags);
605 if (!list_empty(&audit_freelist)) {
606 ab = list_entry(audit_freelist.next,
607 struct audit_buffer, list);
609 --audit_freelist_count;
611 spin_unlock_irqrestore(&audit_freelist_lock, flags);
614 ab = kmalloc(sizeof(*ab), gfp_mask);
618 atomic_inc(&audit_backlog);
620 ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
625 nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
626 nlh->nlmsg_type = AUDIT_KERNEL;
627 nlh->nlmsg_flags = 0;
632 audit_buffer_free(ab);
636 /* Obtain an audit buffer. This routine does locking to obtain the
637 * audit buffer, but then no locking is required for calls to
638 * audit_log_*format. If the tsk is a task that is currently in a
639 * syscall, then the syscall is marked as auditable and an audit record
640 * will be written at syscall exit. If there is no associated task, tsk
642 struct audit_buffer *audit_log_start(struct audit_context *ctx)
644 struct audit_buffer *ab = NULL;
648 if (!audit_initialized)
651 if (audit_backlog_limit
652 && atomic_read(&audit_backlog) > audit_backlog_limit) {
653 if (audit_rate_check())
655 "audit: audit_backlog=%d > "
656 "audit_backlog_limit=%d\n",
657 atomic_read(&audit_backlog),
658 audit_backlog_limit);
659 audit_log_lost("backlog limit exceeded");
663 ab = audit_buffer_alloc(ctx, GFP_ATOMIC);
665 audit_log_lost("out of memory in audit_log_start");
669 #ifdef CONFIG_AUDITSYSCALL
671 audit_get_stamp(ab->ctx, &t, &serial);
678 audit_log_format(ab, "audit(%lu.%03lu:%u): ",
679 t.tv_sec, t.tv_nsec/1000000, serial);
684 * audit_expand - expand skb in the audit buffer
687 * Returns 0 (no space) on failed expansion, or available space if
690 static inline int audit_expand(struct audit_buffer *ab, int extra)
692 struct sk_buff *skb = ab->skb;
693 int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
696 audit_log_lost("out of memory in audit_expand");
699 return skb_tailroom(skb);
702 /* Format an audit message into the audit buffer. If there isn't enough
703 * room in the audit buffer, more room will be allocated and vsnprint
704 * will be called a second time. Currently, we assume that a printk
705 * can't format message larger than 1024 bytes, so we don't either. */
706 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
717 avail = skb_tailroom(skb);
719 avail = audit_expand(ab, AUDIT_BUFSIZ);
723 len = vsnprintf(skb->tail, avail, fmt, args);
725 /* The printk buffer is 1024 bytes long, so if we get
726 * here and AUDIT_BUFSIZ is at least 1024, then we can
727 * log everything that printk could have logged. */
728 avail = audit_expand(ab, 1+len-avail);
731 len = vsnprintf(skb->tail, avail, fmt, args);
733 skb_put(skb, (len < avail) ? len : avail);
738 /* Format a message into the audit buffer. All the work is done in
739 * audit_log_vformat. */
740 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
747 audit_log_vformat(ab, fmt, args);
751 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len)
755 for (i=0; i<len; i++)
756 audit_log_format(ab, "%02x", buf[i]);
759 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
761 const unsigned char *p = string;
764 if (*p == '"' || *p == ' ' || *p < 0x20 || *p > 0x7f) {
765 audit_log_hex(ab, string, strlen(string));
770 audit_log_format(ab, "\"%s\"", string);
774 /* This is a helper-function to print the d_path without using a static
775 * buffer or allocating another buffer in addition to the one in
777 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
778 struct dentry *dentry, struct vfsmount *vfsmnt)
781 struct sk_buff *skb = ab->skb;
785 audit_log_format(ab, " %s", prefix);
787 avail = skb_tailroom(skb);
788 p = d_path(dentry, vfsmnt, skb->tail, avail);
790 /* FIXME: can we save some information here? */
791 audit_log_format(ab, "<toolong>");
793 /* path isn't at start of buffer */
794 len = ((char *)skb->tail + avail - 1) - p;
795 memmove(skb->tail, p, len);
800 /* Remove queued messages from the audit_txlist and send them to userspace. */
801 static void audit_tasklet_handler(unsigned long arg)
804 struct audit_buffer *ab;
807 spin_lock_irqsave(&audit_txlist_lock, flags);
808 list_splice_init(&audit_txlist, &list);
809 spin_unlock_irqrestore(&audit_txlist_lock, flags);
811 while (!list_empty(&list)) {
812 ab = list_entry(list.next, struct audit_buffer, list);
814 audit_log_end_fast(ab);
818 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
820 /* The netlink_* functions cannot be called inside an irq context, so
821 * the audit buffer is places on a queue and a tasklet is scheduled to
822 * remove them from the queue outside the irq context. May be called in
824 static void audit_log_end_irq(struct audit_buffer *ab)
830 spin_lock_irqsave(&audit_txlist_lock, flags);
831 list_add_tail(&ab->list, &audit_txlist);
832 spin_unlock_irqrestore(&audit_txlist_lock, flags);
834 tasklet_schedule(&audit_tasklet);
837 /* Send the message in the audit buffer directly to user space. May not
838 * be called in an irq context. */
839 static void audit_log_end_fast(struct audit_buffer *ab)
844 if (!audit_rate_check()) {
845 audit_log_lost("rate limit exceeded");
847 if (audit_log_drain(ab))
850 audit_buffer_free(ab);
853 /* Send or queue the message in the audit buffer, depending on the
854 * current context. (A convenience function that may be called in any
856 void audit_log_end(struct audit_buffer *ab)
859 audit_log_end_irq(ab);
861 audit_log_end_fast(ab);
864 /* Log an audit record. This is a convenience function that calls
865 * audit_log_start, audit_log_vformat, and audit_log_end. It may be
866 * called in any context. */
867 void audit_log(struct audit_context *ctx, const char *fmt, ...)
869 struct audit_buffer *ab;
872 ab = audit_log_start(ctx);
875 audit_log_vformat(ab, fmt, args);