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 */
141 int len; /* used area of tmp */
142 int size; /* size of tmp */
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 case AUDIT_SIGNAL_INFO:
326 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
330 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
333 default: /* bad msg */
340 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
344 struct audit_status *status_get, status_set;
346 struct audit_buffer *ab;
347 u16 msg_type = nlh->nlmsg_type;
348 uid_t loginuid; /* loginuid of sender */
349 struct audit_sig_info sig_data;
351 err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
355 pid = NETLINK_CREDS(skb)->pid;
356 uid = NETLINK_CREDS(skb)->uid;
357 loginuid = NETLINK_CB(skb).loginuid;
358 seq = nlh->nlmsg_seq;
359 data = NLMSG_DATA(nlh);
363 status_set.enabled = audit_enabled;
364 status_set.failure = audit_failure;
365 status_set.pid = audit_pid;
366 status_set.rate_limit = audit_rate_limit;
367 status_set.backlog_limit = audit_backlog_limit;
368 status_set.lost = atomic_read(&audit_lost);
369 status_set.backlog = atomic_read(&audit_backlog);
370 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
371 &status_set, sizeof(status_set));
374 if (nlh->nlmsg_len < sizeof(struct audit_status))
376 status_get = (struct audit_status *)data;
377 if (status_get->mask & AUDIT_STATUS_ENABLED) {
378 err = audit_set_enabled(status_get->enabled, loginuid);
379 if (err < 0) return err;
381 if (status_get->mask & AUDIT_STATUS_FAILURE) {
382 err = audit_set_failure(status_get->failure, loginuid);
383 if (err < 0) return err;
385 if (status_get->mask & AUDIT_STATUS_PID) {
387 audit_pid = status_get->pid;
388 audit_log(NULL, "audit_pid=%d old=%d by auid %u",
389 audit_pid, old, loginuid);
391 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
392 audit_set_rate_limit(status_get->rate_limit, loginuid);
393 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
394 audit_set_backlog_limit(status_get->backlog_limit,
398 ab = audit_log_start(NULL);
400 break; /* audit_panic has been called */
402 "user pid=%d uid=%d length=%d loginuid=%u"
406 - ((char *)data - (char *)nlh)),
407 loginuid, (char *)data);
408 ab->type = AUDIT_USER;
414 if (nlh->nlmsg_len < sizeof(struct audit_rule))
418 #ifdef CONFIG_AUDITSYSCALL
419 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
420 uid, seq, data, loginuid);
425 case AUDIT_SIGNAL_INFO:
426 sig_data.uid = audit_sig_uid;
427 sig_data.pid = audit_sig_pid;
428 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
429 0, 0, &sig_data, sizeof(sig_data));
436 return err < 0 ? err : 0;
439 /* Get message from skb (based on rtnetlink_rcv_skb). Each message is
440 * processed by audit_receive_msg. Malformed skbs with wrong length are
441 * discarded silently. */
442 static void audit_receive_skb(struct sk_buff *skb)
445 struct nlmsghdr *nlh;
448 while (skb->len >= NLMSG_SPACE(0)) {
449 nlh = (struct nlmsghdr *)skb->data;
450 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
452 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
455 if ((err = audit_receive_msg(skb, nlh))) {
456 netlink_ack(skb, nlh, err);
457 } else if (nlh->nlmsg_flags & NLM_F_ACK)
458 netlink_ack(skb, nlh, 0);
463 /* Receive messages from netlink socket. */
464 static void audit_receive(struct sock *sk, int length)
469 down(&audit_netlink_sem);
471 for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
472 skb = skb_dequeue(&sk->sk_receive_queue);
473 audit_receive_skb(skb);
476 up(&audit_netlink_sem);
479 /* Move data from tmp buffer into an skb. This is an extra copy, and
480 * that is unfortunate. However, the copy will only occur when a record
481 * is being written to user space, which is already a high-overhead
482 * operation. (Elimination of the copy is possible, for example, by
483 * writing directly into a pre-allocated skb, at the cost of wasting
485 static void audit_log_move(struct audit_buffer *ab)
488 struct nlmsghdr *nlh;
490 int len = NLMSG_SPACE(0) + ab->len + 1;
492 /* possible resubmission */
496 skb = alloc_skb(len, GFP_ATOMIC);
498 /* Lose information in ab->tmp */
499 audit_log_lost("out of memory in audit_log_move");
503 nlh = (struct nlmsghdr *)skb_put(skb, NLMSG_SPACE(0));
504 nlh->nlmsg_type = ab->type;
505 nlh->nlmsg_len = ab->len;
506 nlh->nlmsg_flags = 0;
507 nlh->nlmsg_pid = ab->pid;
509 start = skb_put(skb, ab->len);
510 memcpy(start, ab->tmp, ab->len);
513 /* Iterate over the skbuff in the audit_buffer, sending their contents
515 static inline int audit_log_drain(struct audit_buffer *ab)
517 struct sk_buff *skb = ab->skb;
523 skb_get(skb); /* because netlink_* frees */
524 retval = netlink_unicast(audit_sock, skb, audit_pid,
527 if (retval == -EAGAIN &&
528 (atomic_read(&audit_backlog)) < audit_backlog_limit) {
529 audit_log_end_irq(ab);
533 if (retval == -ECONNREFUSED) {
535 "audit: *NO* daemon at audit_pid=%d\n",
539 audit_log_lost("netlink socket too busy");
541 if (!audit_pid) { /* No daemon */
542 int offset = NLMSG_SPACE(0);
543 int len = skb->len - offset;
544 skb->data[offset + len] = '\0';
545 printk(KERN_ERR "%s\n", skb->data + offset);
552 /* Initialize audit support at boot time. */
553 static int __init audit_init(void)
555 printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
556 audit_default ? "enabled" : "disabled");
557 audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
559 audit_panic("cannot initialize netlink socket");
561 audit_initialized = 1;
562 audit_enabled = audit_default;
563 audit_log(NULL, "initialized");
568 /* Without CONFIG_NET, we have no skbuffs. For now, print what we have
570 static void audit_log_move(struct audit_buffer *ab)
572 printk(KERN_ERR "%*.*s\n", ab->len, ab->len, ab->tmp);
576 static inline int audit_log_drain(struct audit_buffer *ab)
581 /* Initialize audit support at boot time. */
582 int __init audit_init(void)
584 printk(KERN_INFO "audit: initializing WITHOUT netlink support\n");
588 audit_initialized = 1;
589 audit_enabled = audit_default;
590 audit_log(NULL, "initialized");
595 __initcall(audit_init);
597 /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */
598 static int __init audit_enable(char *str)
600 audit_default = !!simple_strtol(str, NULL, 0);
601 printk(KERN_INFO "audit: %s%s\n",
602 audit_default ? "enabled" : "disabled",
603 audit_initialized ? "" : " (after initialization)");
604 if (audit_initialized)
605 audit_enabled = audit_default;
609 __setup("audit=", audit_enable);
611 static void audit_buffer_free(struct audit_buffer *ab)
619 atomic_dec(&audit_backlog);
620 spin_lock_irqsave(&audit_freelist_lock, flags);
621 if (++audit_freelist_count > AUDIT_MAXFREE)
624 list_add(&ab->list, &audit_freelist);
625 spin_unlock_irqrestore(&audit_freelist_lock, flags);
628 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
632 struct audit_buffer *ab = NULL;
634 spin_lock_irqsave(&audit_freelist_lock, flags);
635 if (!list_empty(&audit_freelist)) {
636 ab = list_entry(audit_freelist.next,
637 struct audit_buffer, list);
639 --audit_freelist_count;
641 spin_unlock_irqrestore(&audit_freelist_lock, flags);
644 ab = kmalloc(sizeof(*ab), GFP_ATOMIC);
648 atomic_inc(&audit_backlog);
650 ab->tmp = kmalloc(AUDIT_BUFSIZ, GFP_ATOMIC);
657 ab->size = AUDIT_BUFSIZ;
658 ab->type = AUDIT_KERNEL;
662 audit_buffer_free(ab);
666 /* Obtain an audit buffer. This routine does locking to obtain the
667 * audit buffer, but then no locking is required for calls to
668 * audit_log_*format. If the tsk is a task that is currently in a
669 * syscall, then the syscall is marked as auditable and an audit record
670 * will be written at syscall exit. If there is no associated task, tsk
672 struct audit_buffer *audit_log_start(struct audit_context *ctx)
674 struct audit_buffer *ab = NULL;
678 if (!audit_initialized)
681 if (audit_backlog_limit
682 && atomic_read(&audit_backlog) > audit_backlog_limit) {
683 if (audit_rate_check())
685 "audit: audit_backlog=%d > "
686 "audit_backlog_limit=%d\n",
687 atomic_read(&audit_backlog),
688 audit_backlog_limit);
689 audit_log_lost("backlog limit exceeded");
693 ab = audit_buffer_alloc(ctx, GFP_ATOMIC);
695 audit_log_lost("out of memory in audit_log_start");
699 #ifdef CONFIG_AUDITSYSCALL
701 audit_get_stamp(ab->ctx, &t, &serial);
708 audit_log_format(ab, "audit(%lu.%03lu:%u): ",
709 t.tv_sec, t.tv_nsec/1000000, serial);
714 * audit_expand - expand tmp buffer in the audit buffer
717 * Returns 0 (no space) on failed expansion, or available space if
720 static inline int audit_expand(struct audit_buffer *ab)
723 int len = ab->size + AUDIT_BUFSIZ;
725 tmp = kmalloc(len, GFP_ATOMIC);
728 memcpy(tmp, ab->tmp, ab->len);
732 return ab->size - ab->len;
735 /* Format an audit message into the audit buffer. If there isn't enough
736 * room in the audit buffer, more room will be allocated and vsnprint
737 * will be called a second time. Currently, we assume that a printk
738 * can't format message larger than 1024 bytes, so we don't either. */
739 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
747 avail = ab->size - ab->len;
749 avail = audit_expand(ab);
753 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
755 /* The printk buffer is 1024 bytes long, so if we get
756 * here and AUDIT_BUFSIZ is at least 1024, then we can
757 * log everything that printk could have logged. */
758 avail = audit_expand(ab);
761 len = vsnprintf(ab->tmp + ab->len, avail, fmt, args);
763 ab->len += (len < avail) ? len : avail;
768 /* Format a message into the audit buffer. All the work is done in
769 * audit_log_vformat. */
770 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
777 audit_log_vformat(ab, fmt, args);
781 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len)
785 for (i=0; i<len; i++)
786 audit_log_format(ab, "%02x", buf[i]);
789 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
791 const unsigned char *p = string;
794 if (*p == '"' || *p == ' ' || *p < 0x20 || *p > 0x7f) {
795 audit_log_hex(ab, string, strlen(string));
800 audit_log_format(ab, "\"%s\"", string);
804 /* This is a helper-function to print the d_path without using a static
805 * buffer or allocating another buffer in addition to the one in
807 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
808 struct dentry *dentry, struct vfsmount *vfsmnt)
814 audit_log_format(ab, " %s", prefix);
816 avail = ab->size - ab->len;
817 p = d_path(dentry, vfsmnt, ab->tmp + ab->len, avail);
819 /* FIXME: can we save some information here? */
820 audit_log_format(ab, "<toolong>");
822 /* path isn't at start of buffer */
823 len = (ab->tmp + ab->size - 1) - p;
824 memmove(ab->tmp + ab->len, p, len);
829 /* Remove queued messages from the audit_txlist and send them to userspace. */
830 static void audit_tasklet_handler(unsigned long arg)
833 struct audit_buffer *ab;
836 spin_lock_irqsave(&audit_txlist_lock, flags);
837 list_splice_init(&audit_txlist, &list);
838 spin_unlock_irqrestore(&audit_txlist_lock, flags);
840 while (!list_empty(&list)) {
841 ab = list_entry(list.next, struct audit_buffer, list);
843 audit_log_end_fast(ab);
847 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
849 /* The netlink_* functions cannot be called inside an irq context, so
850 * the audit buffer is places on a queue and a tasklet is scheduled to
851 * remove them from the queue outside the irq context. May be called in
853 static void audit_log_end_irq(struct audit_buffer *ab)
859 spin_lock_irqsave(&audit_txlist_lock, flags);
860 list_add_tail(&ab->list, &audit_txlist);
861 spin_unlock_irqrestore(&audit_txlist_lock, flags);
863 tasklet_schedule(&audit_tasklet);
866 /* Send the message in the audit buffer directly to user space. May not
867 * be called in an irq context. */
868 static void audit_log_end_fast(struct audit_buffer *ab)
873 if (!audit_rate_check()) {
874 audit_log_lost("rate limit exceeded");
877 if (audit_log_drain(ab))
880 audit_buffer_free(ab);
883 /* Send or queue the message in the audit buffer, depending on the
884 * current context. (A convenience function that may be called in any
886 void audit_log_end(struct audit_buffer *ab)
889 audit_log_end_irq(ab);
891 audit_log_end_fast(ab);
894 /* Log an audit record. This is a convenience function that calls
895 * audit_log_start, audit_log_vformat, and audit_log_end. It may be
896 * called in any context. */
897 void audit_log(struct audit_context *ctx, const char *fmt, ...)
899 struct audit_buffer *ab;
902 ab = audit_log_start(ctx);
905 audit_log_vformat(ab, fmt, args);