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 static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
145 struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
146 nlh->nlmsg_pid = pid;
150 struct list_head list;
151 struct audit_rule rule;
154 static void audit_log_end_irq(struct audit_buffer *ab);
155 static void audit_log_end_fast(struct audit_buffer *ab);
157 static void audit_panic(const char *message)
159 switch (audit_failure)
161 case AUDIT_FAIL_SILENT:
163 case AUDIT_FAIL_PRINTK:
164 printk(KERN_ERR "audit: %s\n", message);
166 case AUDIT_FAIL_PANIC:
167 panic("audit: %s\n", message);
172 static inline int audit_rate_check(void)
174 static unsigned long last_check = 0;
175 static int messages = 0;
176 static DEFINE_SPINLOCK(lock);
179 unsigned long elapsed;
182 if (!audit_rate_limit) return 1;
184 spin_lock_irqsave(&lock, flags);
185 if (++messages < audit_rate_limit) {
189 elapsed = now - last_check;
196 spin_unlock_irqrestore(&lock, flags);
201 /* Emit at least 1 message per second, even if audit_rate_check is
203 void audit_log_lost(const char *message)
205 static unsigned long last_msg = 0;
206 static DEFINE_SPINLOCK(lock);
211 atomic_inc(&audit_lost);
213 print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
216 spin_lock_irqsave(&lock, flags);
218 if (now - last_msg > HZ) {
222 spin_unlock_irqrestore(&lock, flags);
227 "audit: audit_lost=%d audit_backlog=%d"
228 " audit_rate_limit=%d audit_backlog_limit=%d\n",
229 atomic_read(&audit_lost),
230 atomic_read(&audit_backlog),
232 audit_backlog_limit);
233 audit_panic(message);
238 static int audit_set_rate_limit(int limit, uid_t loginuid)
240 int old = audit_rate_limit;
241 audit_rate_limit = limit;
242 audit_log(NULL, AUDIT_CONFIG_CHANGE,
243 "audit_rate_limit=%d old=%d by auid %u",
244 audit_rate_limit, old, loginuid);
248 static int audit_set_backlog_limit(int limit, uid_t loginuid)
250 int old = audit_backlog_limit;
251 audit_backlog_limit = limit;
252 audit_log(NULL, AUDIT_CONFIG_CHANGE,
253 "audit_backlog_limit=%d old=%d by auid %u",
254 audit_backlog_limit, old, loginuid);
258 static int audit_set_enabled(int state, uid_t loginuid)
260 int old = audit_enabled;
261 if (state != 0 && state != 1)
263 audit_enabled = state;
264 audit_log(NULL, AUDIT_CONFIG_CHANGE,
265 "audit_enabled=%d old=%d by auid %u",
266 audit_enabled, old, loginuid);
270 static int audit_set_failure(int state, uid_t loginuid)
272 int old = audit_failure;
273 if (state != AUDIT_FAIL_SILENT
274 && state != AUDIT_FAIL_PRINTK
275 && state != AUDIT_FAIL_PANIC)
277 audit_failure = state;
278 audit_log(NULL, AUDIT_CONFIG_CHANGE,
279 "audit_failure=%d old=%d by auid %u",
280 audit_failure, old, loginuid);
284 void audit_send_reply(int pid, int seq, int type, int done, int multi,
285 void *payload, int size)
288 struct nlmsghdr *nlh;
289 int len = NLMSG_SPACE(size);
291 int flags = multi ? NLM_F_MULTI : 0;
292 int t = done ? NLMSG_DONE : type;
294 skb = alloc_skb(len, GFP_KERNEL);
298 nlh = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
299 nlh->nlmsg_flags = flags;
300 data = NLMSG_DATA(nlh);
301 memcpy(data, payload, size);
302 netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
305 nlmsg_failure: /* Used by NLMSG_PUT */
311 * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
314 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
324 case AUDIT_SIGNAL_INFO:
325 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
329 case AUDIT_USER_AUTH:
330 case AUDIT_USER_ACCT:
331 case AUDIT_USER_MGMT:
333 case AUDIT_CRED_DISP:
334 case AUDIT_USER_START:
337 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
340 default: /* bad msg */
347 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
351 struct audit_status *status_get, status_set;
353 struct audit_buffer *ab;
354 u16 msg_type = nlh->nlmsg_type;
355 uid_t loginuid; /* loginuid of sender */
356 struct audit_sig_info sig_data;
358 err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
362 pid = NETLINK_CREDS(skb)->pid;
363 uid = NETLINK_CREDS(skb)->uid;
364 loginuid = NETLINK_CB(skb).loginuid;
365 seq = nlh->nlmsg_seq;
366 data = NLMSG_DATA(nlh);
370 status_set.enabled = audit_enabled;
371 status_set.failure = audit_failure;
372 status_set.pid = audit_pid;
373 status_set.rate_limit = audit_rate_limit;
374 status_set.backlog_limit = audit_backlog_limit;
375 status_set.lost = atomic_read(&audit_lost);
376 status_set.backlog = atomic_read(&audit_backlog);
377 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
378 &status_set, sizeof(status_set));
381 if (nlh->nlmsg_len < sizeof(struct audit_status))
383 status_get = (struct audit_status *)data;
384 if (status_get->mask & AUDIT_STATUS_ENABLED) {
385 err = audit_set_enabled(status_get->enabled, loginuid);
386 if (err < 0) return err;
388 if (status_get->mask & AUDIT_STATUS_FAILURE) {
389 err = audit_set_failure(status_get->failure, loginuid);
390 if (err < 0) return err;
392 if (status_get->mask & AUDIT_STATUS_PID) {
394 audit_pid = status_get->pid;
395 audit_log(NULL, AUDIT_CONFIG_CHANGE,
396 "audit_pid=%d old=%d by auid %u",
397 audit_pid, old, loginuid);
399 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
400 audit_set_rate_limit(status_get->rate_limit, loginuid);
401 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
402 audit_set_backlog_limit(status_get->backlog_limit,
406 case AUDIT_USER_AUTH:
407 case AUDIT_USER_ACCT:
408 case AUDIT_USER_MGMT:
410 case AUDIT_CRED_DISP:
411 case AUDIT_USER_START:
414 ab = audit_log_start(NULL, msg_type);
416 break; /* audit_panic has been called */
418 "user pid=%d uid=%d length=%d loginuid=%u"
422 - ((char *)data - (char *)nlh)),
423 loginuid, (char *)data);
424 audit_set_pid(ab, pid);
429 if (nlh->nlmsg_len < sizeof(struct audit_rule))
433 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
434 uid, seq, data, loginuid);
436 case AUDIT_SIGNAL_INFO:
437 sig_data.uid = audit_sig_uid;
438 sig_data.pid = audit_sig_pid;
439 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
440 0, 0, &sig_data, sizeof(sig_data));
447 return err < 0 ? err : 0;
450 /* Get message from skb (based on rtnetlink_rcv_skb). Each message is
451 * processed by audit_receive_msg. Malformed skbs with wrong length are
452 * discarded silently. */
453 static void audit_receive_skb(struct sk_buff *skb)
456 struct nlmsghdr *nlh;
459 while (skb->len >= NLMSG_SPACE(0)) {
460 nlh = (struct nlmsghdr *)skb->data;
461 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
463 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
466 if ((err = audit_receive_msg(skb, nlh))) {
467 netlink_ack(skb, nlh, err);
468 } else if (nlh->nlmsg_flags & NLM_F_ACK)
469 netlink_ack(skb, nlh, 0);
474 /* Receive messages from netlink socket. */
475 static void audit_receive(struct sock *sk, int length)
480 down(&audit_netlink_sem);
482 for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
483 skb = skb_dequeue(&sk->sk_receive_queue);
484 audit_receive_skb(skb);
487 up(&audit_netlink_sem);
490 /* Grab skbuff from the audit_buffer and send to user space. */
491 static inline int audit_log_drain(struct audit_buffer *ab)
493 struct sk_buff *skb = ab->skb;
499 struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
500 nlh->nlmsg_len = skb->len - NLMSG_SPACE(0);
501 skb_get(skb); /* because netlink_* frees */
502 retval = netlink_unicast(audit_sock, skb, audit_pid,
505 if (retval == -EAGAIN &&
506 (atomic_read(&audit_backlog)) < audit_backlog_limit) {
507 audit_log_end_irq(ab);
511 if (retval == -ECONNREFUSED) {
513 "audit: *NO* daemon at audit_pid=%d\n",
517 audit_log_lost("netlink socket too busy");
519 if (!audit_pid) { /* No daemon */
520 int offset = NLMSG_SPACE(0);
521 int len = skb->len - offset;
522 skb->data[offset + len] = '\0';
523 printk(KERN_ERR "%s\n", skb->data + offset);
529 /* Initialize audit support at boot time. */
530 static int __init audit_init(void)
532 printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
533 audit_default ? "enabled" : "disabled");
534 audit_sock = netlink_kernel_create(NETLINK_AUDIT, audit_receive);
536 audit_panic("cannot initialize netlink socket");
538 audit_initialized = 1;
539 audit_enabled = audit_default;
540 audit_log(NULL, AUDIT_KERNEL, "initialized");
543 __initcall(audit_init);
545 /* Process kernel command-line parameter at boot time. audit=0 or audit=1. */
546 static int __init audit_enable(char *str)
548 audit_default = !!simple_strtol(str, NULL, 0);
549 printk(KERN_INFO "audit: %s%s\n",
550 audit_default ? "enabled" : "disabled",
551 audit_initialized ? "" : " (after initialization)");
552 if (audit_initialized)
553 audit_enabled = audit_default;
557 __setup("audit=", audit_enable);
559 static void audit_buffer_free(struct audit_buffer *ab)
568 atomic_dec(&audit_backlog);
569 spin_lock_irqsave(&audit_freelist_lock, flags);
570 if (++audit_freelist_count > AUDIT_MAXFREE)
573 list_add(&ab->list, &audit_freelist);
574 spin_unlock_irqrestore(&audit_freelist_lock, flags);
577 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
578 int gfp_mask, int type)
581 struct audit_buffer *ab = NULL;
582 struct nlmsghdr *nlh;
584 spin_lock_irqsave(&audit_freelist_lock, flags);
585 if (!list_empty(&audit_freelist)) {
586 ab = list_entry(audit_freelist.next,
587 struct audit_buffer, list);
589 --audit_freelist_count;
591 spin_unlock_irqrestore(&audit_freelist_lock, flags);
594 ab = kmalloc(sizeof(*ab), gfp_mask);
598 atomic_inc(&audit_backlog);
600 ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
605 nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
606 nlh->nlmsg_type = type;
607 nlh->nlmsg_flags = 0;
612 audit_buffer_free(ab);
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, int type)
624 struct audit_buffer *ab = NULL;
628 if (!audit_initialized)
631 if (audit_backlog_limit
632 && atomic_read(&audit_backlog) > audit_backlog_limit) {
633 if (audit_rate_check())
635 "audit: audit_backlog=%d > "
636 "audit_backlog_limit=%d\n",
637 atomic_read(&audit_backlog),
638 audit_backlog_limit);
639 audit_log_lost("backlog limit exceeded");
643 ab = audit_buffer_alloc(ctx, GFP_ATOMIC, type);
645 audit_log_lost("out of memory in audit_log_start");
649 if (!audit_get_stamp(ab->ctx, &t, &serial)) {
654 audit_log_format(ab, "audit(%lu.%03lu:%u): ",
655 t.tv_sec, t.tv_nsec/1000000, serial);
660 * audit_expand - expand skb in the audit buffer
663 * Returns 0 (no space) on failed expansion, or available space if
666 static inline int audit_expand(struct audit_buffer *ab, int extra)
668 struct sk_buff *skb = ab->skb;
669 int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
672 audit_log_lost("out of memory in audit_expand");
675 return skb_tailroom(skb);
678 /* Format an audit message into the audit buffer. If there isn't enough
679 * room in the audit buffer, more room will be allocated and vsnprint
680 * will be called a second time. Currently, we assume that a printk
681 * can't format message larger than 1024 bytes, so we don't either. */
682 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
694 avail = skb_tailroom(skb);
696 avail = audit_expand(ab, AUDIT_BUFSIZ);
700 va_copy(args2, args);
701 len = vsnprintf(skb->tail, avail, fmt, args);
703 /* The printk buffer is 1024 bytes long, so if we get
704 * here and AUDIT_BUFSIZ is at least 1024, then we can
705 * log everything that printk could have logged. */
706 avail = audit_expand(ab, max_t(AUDIT_BUFSIZ, 1+len-avail));
709 len = vsnprintf(skb->tail, avail, fmt, args2);
711 skb_put(skb, (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)
759 struct sk_buff *skb = ab->skb;
763 audit_log_format(ab, " %s", prefix);
765 avail = skb_tailroom(skb);
766 p = d_path(dentry, vfsmnt, skb->tail, 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 = ((char *)skb->tail + avail - 1) - p;
773 memmove(skb->tail, p, len);
778 /* Remove queued messages from the audit_txlist and send them to userspace. */
779 static void audit_tasklet_handler(unsigned long arg)
782 struct audit_buffer *ab;
785 spin_lock_irqsave(&audit_txlist_lock, flags);
786 list_splice_init(&audit_txlist, &list);
787 spin_unlock_irqrestore(&audit_txlist_lock, flags);
789 while (!list_empty(&list)) {
790 ab = list_entry(list.next, struct audit_buffer, list);
792 audit_log_end_fast(ab);
796 static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
798 /* The netlink_* functions cannot be called inside an irq context, so
799 * the audit buffer is places on a queue and a tasklet is scheduled to
800 * remove them from the queue outside the irq context. May be called in
802 static void audit_log_end_irq(struct audit_buffer *ab)
808 spin_lock_irqsave(&audit_txlist_lock, flags);
809 list_add_tail(&ab->list, &audit_txlist);
810 spin_unlock_irqrestore(&audit_txlist_lock, flags);
812 tasklet_schedule(&audit_tasklet);
815 /* Send the message in the audit buffer directly to user space. May not
816 * be called in an irq context. */
817 static void audit_log_end_fast(struct audit_buffer *ab)
822 if (!audit_rate_check()) {
823 audit_log_lost("rate limit exceeded");
825 if (audit_log_drain(ab))
828 audit_buffer_free(ab);
831 /* Send or queue the message in the audit buffer, depending on the
832 * current context. (A convenience function that may be called in any
834 void audit_log_end(struct audit_buffer *ab)
837 audit_log_end_irq(ab);
839 audit_log_end_fast(ab);
842 /* Log an audit record. This is a convenience function that calls
843 * audit_log_start, audit_log_vformat, and audit_log_end. It may be
844 * called in any context. */
845 void audit_log(struct audit_context *ctx, int type, const char *fmt, ...)
847 struct audit_buffer *ab;
850 ab = audit_log_start(ctx, type);
853 audit_log_vformat(ab, fmt, args);