/* audit.c -- Auditing support

   * Gateway between the kernel (e.g., selinux) and the user-space audit daemon.
   * System-call specific features have moved to auditsc.c
   *
   * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
   * All Rights Reserved.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   *
   * Written by Rickard E. (Rik) Faith <faith@redhat.com>
   *
   * Goals: 1) Integrate fully with SELinux.
   *	  2) Minimal run-time overhead:
   *	     a) Minimal when syscall auditing is disabled (audit_enable=0).
   *	     b) Small when syscall auditing is enabled and no audit record
   *		is generated (defer as much work as possible to record
   *		generation time):
   *		i) context is allocated,
   *		ii) names from getname are stored without a copy, and
   *		iii) inode information stored from path_lookup.
   *	  3) Ability to disable syscall auditing at boot time (audit=0).
   *	  4) Usable by other parts of the kernel (if audit_log* is called,
   *	     then a syscall record will be generated automatically for the
   *	     current syscall).
   *	  5) Netlink interface to user-space.
   *	  6) Support low-overhead kernel-based filtering to minimize the
   *	     information that must be passed to user-space.
   *

   * Example user-space utilities: http://people.redhat.com/sgrubb/audit/

   */
  
  #include <linux/init.h>

  #include <asm/types.h>

  #include <asm/atomic.h>

  #include <linux/mm.h>
  #include <linux/module.h>

  #include <linux/err.h>
  #include <linux/kthread.h>

  
  #include <linux/audit.h>
  
  #include <net/sock.h>

  #include <net/netlink.h>

  #include <linux/skbuff.h>
  #include <linux/netlink.h>

  #include <linux/selinux.h>

  #include <linux/inotify.h>

  #include <linux/freezer.h>

  
  #include "audit.h"

  
  /* No auditing will take place until audit_initialized != 0.
   * (Initialization happens after skb_init is called.) */
  static int	audit_initialized;
  
  /* No syscall auditing will take place unless audit_enabled != 0. */
  int		audit_enabled;
  
  /* Default state when kernel boots without any parameters. */
  static int	audit_default;
  
  /* If auditing cannot proceed, audit_failure selects what happens. */
  static int	audit_failure = AUDIT_FAIL_PRINTK;
  
  /* If audit records are to be written to the netlink socket, audit_pid
   * contains the (non-zero) pid. */

  int		audit_pid;

  /* If audit_rate_limit is non-zero, limit the rate of sending audit records

   * to that number per second.  This prevents DoS attacks, but results in
   * audit records being dropped. */
  static int	audit_rate_limit;
  
  /* Number of outstanding audit_buffers allowed. */
  static int	audit_backlog_limit = 64;

  static int	audit_backlog_wait_time = 60 * HZ;
  static int	audit_backlog_wait_overflow = 0;

  /* The identity of the user shutting down the audit system. */
  uid_t		audit_sig_uid = -1;
  pid_t		audit_sig_pid = -1;

  u32		audit_sig_sid = 0;

  /* Records can be lost in several ways:
     0) [suppressed in audit_alloc]
     1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
     2) out of memory in audit_log_move [alloc_skb]
     3) suppressed due to audit_rate_limit
     4) suppressed due to audit_backlog_limit
  */
  static atomic_t    audit_lost = ATOMIC_INIT(0);
  
  /* The netlink socket. */
  static struct sock *audit_sock;

  /* Inotify handle. */
  struct inotify_handle *audit_ih;
  
  /* Hash for inode-based rules */
  struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS];

  /* The audit_freelist is a list of pre-allocated audit buffers (if more

   * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
   * being placed on the freelist). */

  static DEFINE_SPINLOCK(audit_freelist_lock);

  static int	   audit_freelist_count;

  static LIST_HEAD(audit_freelist);

  static struct sk_buff_head audit_skb_queue;
  static struct task_struct *kauditd_task;
  static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);

  static DECLARE_WAIT_QUEUE_HEAD(audit_backlog_wait);

  /* Serialize requests from userspace. */
  static DEFINE_MUTEX(audit_cmd_mutex);

  
  /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
   * audit records.  Since printk uses a 1024 byte buffer, this buffer
   * should be at least that large. */
  #define AUDIT_BUFSIZ 1024
  
  /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
   * audit_freelist.  Doing so eliminates many kmalloc/kfree calls. */
  #define AUDIT_MAXFREE  (2*NR_CPUS)
  
  /* The audit_buffer is used when formatting an audit record.  The caller
   * locks briefly to get the record off the freelist or to allocate the
   * buffer, and locks briefly to send the buffer to the netlink layer or
   * to place it on a transmit queue.  Multiple audit_buffers can be in
   * use simultaneously. */
  struct audit_buffer {
  	struct list_head     list;

  	struct sk_buff       *skb;	/* formatted skb ready to send */

  	struct audit_context *ctx;	/* NULL or associated context */

  	gfp_t		     gfp_mask;

  };

  static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
  {
  	struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
  	nlh->nlmsg_pid = pid;
  }

  void audit_panic(const char *message)

  {
  	switch (audit_failure)
  	{
  	case AUDIT_FAIL_SILENT:
  		break;
  	case AUDIT_FAIL_PRINTK:
  		printk(KERN_ERR "audit: %s
  ", message);
  		break;
  	case AUDIT_FAIL_PANIC:
  		panic("audit: %s
  ", message);
  		break;
  	}
  }
  
  static inline int audit_rate_check(void)
  {
  	static unsigned long	last_check = 0;
  	static int		messages   = 0;
  	static DEFINE_SPINLOCK(lock);
  	unsigned long		flags;
  	unsigned long		now;
  	unsigned long		elapsed;
  	int			retval	   = 0;
  
  	if (!audit_rate_limit) return 1;
  
  	spin_lock_irqsave(&lock, flags);
  	if (++messages < audit_rate_limit) {
  		retval = 1;
  	} else {
  		now     = jiffies;
  		elapsed = now - last_check;
  		if (elapsed > HZ) {
  			last_check = now;
  			messages   = 0;
  			retval     = 1;
  		}
  	}
  	spin_unlock_irqrestore(&lock, flags);
  
  	return retval;
  }

  /**
   * audit_log_lost - conditionally log lost audit message event
   * @message: the message stating reason for lost audit message
   *
   * Emit at least 1 message per second, even if audit_rate_check is
   * throttling.
   * Always increment the lost messages counter.
  */

  void audit_log_lost(const char *message)
  {
  	static unsigned long	last_msg = 0;
  	static DEFINE_SPINLOCK(lock);
  	unsigned long		flags;
  	unsigned long		now;
  	int			print;
  
  	atomic_inc(&audit_lost);
  
  	print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
  
  	if (!print) {
  		spin_lock_irqsave(&lock, flags);
  		now = jiffies;
  		if (now - last_msg > HZ) {
  			print = 1;
  			last_msg = now;
  		}
  		spin_unlock_irqrestore(&lock, flags);
  	}
  
  	if (print) {
  		printk(KERN_WARNING

  		       "audit: audit_lost=%d audit_rate_limit=%d audit_backlog_limit=%d
  ",

  		       atomic_read(&audit_lost),

  		       audit_rate_limit,
  		       audit_backlog_limit);
  		audit_panic(message);
  	}

  }

  static int audit_set_rate_limit(int limit, uid_t loginuid, u32 sid)

  {

  	int old	= audit_rate_limit;
  
  	if (sid) {
  		char *ctx = NULL;
  		u32 len;
  		int rc;

  		if ((rc = selinux_sid_to_string(sid, &ctx, &len)))

  			return rc;
  		else
  			audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
  				"audit_rate_limit=%d old=%d by auid=%u subj=%s",
  				limit, old, loginuid, ctx);
  		kfree(ctx);
  	} else
  		audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,

  			"audit_rate_limit=%d old=%d by auid=%u",

  			limit, old, loginuid);
  	audit_rate_limit = limit;

  	return 0;

  }

  static int audit_set_backlog_limit(int limit, uid_t loginuid, u32 sid)

  {

  	int old	= audit_backlog_limit;
  
  	if (sid) {
  		char *ctx = NULL;
  		u32 len;
  		int rc;

  		if ((rc = selinux_sid_to_string(sid, &ctx, &len)))

  			return rc;
  		else
  			audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
  			    "audit_backlog_limit=%d old=%d by auid=%u subj=%s",
  				limit, old, loginuid, ctx);
  		kfree(ctx);
  	} else
  		audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,

  			"audit_backlog_limit=%d old=%d by auid=%u",

  			limit, old, loginuid);
  	audit_backlog_limit = limit;

  	return 0;

  }

  static int audit_set_enabled(int state, uid_t loginuid, u32 sid)

  {

  	int old = audit_enabled;

  	if (state != 0 && state != 1)
  		return -EINVAL;

  
  	if (sid) {
  		char *ctx = NULL;
  		u32 len;
  		int rc;

  		if ((rc = selinux_sid_to_string(sid, &ctx, &len)))

  			return rc;
  		else
  			audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
  				"audit_enabled=%d old=%d by auid=%u subj=%s",
  				state, old, loginuid, ctx);
  		kfree(ctx);
  	} else
  		audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,

  			"audit_enabled=%d old=%d by auid=%u",

  			state, old, loginuid);
  	audit_enabled = state;

  	return 0;

  }

  static int audit_set_failure(int state, uid_t loginuid, u32 sid)

  {

  	int old = audit_failure;

  	if (state != AUDIT_FAIL_SILENT
  	    && state != AUDIT_FAIL_PRINTK
  	    && state != AUDIT_FAIL_PANIC)
  		return -EINVAL;

  
  	if (sid) {
  		char *ctx = NULL;
  		u32 len;
  		int rc;

  		if ((rc = selinux_sid_to_string(sid, &ctx, &len)))

  			return rc;
  		else
  			audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
  				"audit_failure=%d old=%d by auid=%u subj=%s",
  				state, old, loginuid, ctx);
  		kfree(ctx);
  	} else
  		audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,

  			"audit_failure=%d old=%d by auid=%u",

  			state, old, loginuid);
  	audit_failure = state;

  	return 0;

  }

  static int kauditd_thread(void *dummy)

  {
  	struct sk_buff *skb;

  	while (!kthread_should_stop()) {

  		skb = skb_dequeue(&audit_skb_queue);

  		wake_up(&audit_backlog_wait);

  		if (skb) {
  			if (audit_pid) {
  				int err = netlink_unicast(audit_sock, skb, audit_pid, 0);
  				if (err < 0) {
  					BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */
  					printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d
  ", audit_pid);
  					audit_pid = 0;
  				}
  			} else {

  				printk(KERN_NOTICE "%s
  ", skb->data + NLMSG_SPACE(0));

  				kfree_skb(skb);
  			}
  		} else {
  			DECLARE_WAITQUEUE(wait, current);
  			set_current_state(TASK_INTERRUPTIBLE);
  			add_wait_queue(&kauditd_wait, &wait);

  			if (!skb_queue_len(&audit_skb_queue)) {
  				try_to_freeze();

  				schedule();

  			}

  
  			__set_current_state(TASK_RUNNING);
  			remove_wait_queue(&kauditd_wait, &wait);
  		}
  	}

  	return 0;

  }

  int audit_send_list(void *_dest)
  {
  	struct audit_netlink_list *dest = _dest;
  	int pid = dest->pid;
  	struct sk_buff *skb;
  
  	/* wait for parent to finish and send an ACK */

  	mutex_lock(&audit_cmd_mutex);
  	mutex_unlock(&audit_cmd_mutex);

  
  	while ((skb = __skb_dequeue(&dest->q)) != NULL)
  		netlink_unicast(audit_sock, skb, pid, 0);
  
  	kfree(dest);
  
  	return 0;
  }
  
  struct sk_buff *audit_make_reply(int pid, int seq, int type, int done,
  				 int multi, void *payload, int size)
  {
  	struct sk_buff	*skb;
  	struct nlmsghdr	*nlh;
  	int		len = NLMSG_SPACE(size);
  	void		*data;
  	int		flags = multi ? NLM_F_MULTI : 0;
  	int		t     = done  ? NLMSG_DONE  : type;
  
  	skb = alloc_skb(len, GFP_KERNEL);
  	if (!skb)
  		return NULL;
  
  	nlh		 = NLMSG_PUT(skb, pid, seq, t, size);
  	nlh->nlmsg_flags = flags;
  	data		 = NLMSG_DATA(nlh);
  	memcpy(data, payload, size);
  	return skb;
  
  nlmsg_failure:			/* Used by NLMSG_PUT */
  	if (skb)
  		kfree_skb(skb);
  	return NULL;
  }

  /**
   * audit_send_reply - send an audit reply message via netlink
   * @pid: process id to send reply to
   * @seq: sequence number
   * @type: audit message type
   * @done: done (last) flag
   * @multi: multi-part message flag
   * @payload: payload data
   * @size: payload size
   *
   * Allocates an skb, builds the netlink message, and sends it to the pid.
   * No failure notifications.
   */

  void audit_send_reply(int pid, int seq, int type, int done, int multi,
  		      void *payload, int size)
  {
  	struct sk_buff	*skb;

  	skb = audit_make_reply(pid, seq, type, done, multi, payload, size);

  	if (!skb)

  		return;

  	/* Ignore failure. It'll only happen if the sender goes away,
  	   because our timeout is set to infinite. */
  	netlink_unicast(audit_sock, skb, pid, 0);

  	return;

  }
  
  /*
   * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
   * control messages.
   */

  static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type)

  {
  	int err = 0;
  
  	switch (msg_type) {
  	case AUDIT_GET:
  	case AUDIT_LIST:

  	case AUDIT_LIST_RULES:

  	case AUDIT_SET:
  	case AUDIT_ADD:

  	case AUDIT_ADD_RULE:

  	case AUDIT_DEL:

  	case AUDIT_DEL_RULE:

  	case AUDIT_SIGNAL_INFO:

  		if (security_netlink_recv(skb, CAP_AUDIT_CONTROL))

  			err = -EPERM;
  		break;

  	case AUDIT_USER:

  	case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:

  	case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:

  		if (security_netlink_recv(skb, CAP_AUDIT_WRITE))

  			err = -EPERM;
  		break;
  	default:  /* bad msg */
  		err = -EINVAL;
  	}
  
  	return err;
  }
  
  static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
  {

  	u32			uid, pid, seq, sid;

  	void			*data;
  	struct audit_status	*status_get, status_set;
  	int			err;

  	struct audit_buffer	*ab;

  	u16			msg_type = nlh->nlmsg_type;

  	uid_t			loginuid; /* loginuid of sender */

  	struct audit_sig_info   *sig_data;
  	char			*ctx;
  	u32			len;

  	err = audit_netlink_ok(skb, msg_type);

  	if (err)
  		return err;

  	/* As soon as there's any sign of userspace auditd,
  	 * start kauditd to talk to it */

  	if (!kauditd_task)
  		kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
  	if (IS_ERR(kauditd_task)) {
  		err = PTR_ERR(kauditd_task);
  		kauditd_task = NULL;
  		return err;
  	}

  	pid  = NETLINK_CREDS(skb)->pid;
  	uid  = NETLINK_CREDS(skb)->uid;

  	loginuid = NETLINK_CB(skb).loginuid;

  	sid  = NETLINK_CB(skb).sid;

  	seq  = nlh->nlmsg_seq;
  	data = NLMSG_DATA(nlh);
  
  	switch (msg_type) {
  	case AUDIT_GET:
  		status_set.enabled	 = audit_enabled;
  		status_set.failure	 = audit_failure;
  		status_set.pid		 = audit_pid;
  		status_set.rate_limit	 = audit_rate_limit;
  		status_set.backlog_limit = audit_backlog_limit;
  		status_set.lost		 = atomic_read(&audit_lost);

  		status_set.backlog	 = skb_queue_len(&audit_skb_queue);

  		audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
  				 &status_set, sizeof(status_set));
  		break;
  	case AUDIT_SET:
  		if (nlh->nlmsg_len < sizeof(struct audit_status))
  			return -EINVAL;
  		status_get   = (struct audit_status *)data;
  		if (status_get->mask & AUDIT_STATUS_ENABLED) {

  			err = audit_set_enabled(status_get->enabled,
  							loginuid, sid);

  			if (err < 0) return err;
  		}
  		if (status_get->mask & AUDIT_STATUS_FAILURE) {

  			err = audit_set_failure(status_get->failure,
  							 loginuid, sid);

  			if (err < 0) return err;
  		}
  		if (status_get->mask & AUDIT_STATUS_PID) {
  			int old   = audit_pid;

  			if (sid) {

  				if ((err = selinux_sid_to_string(

  						sid, &ctx, &len)))

  					return err;

  				else
  					audit_log(NULL, GFP_KERNEL,
  						AUDIT_CONFIG_CHANGE,
  						"audit_pid=%d old=%d by auid=%u subj=%s",
  						status_get->pid, old,
  						loginuid, ctx);
  				kfree(ctx);
  			} else
  				audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
  					"audit_pid=%d old=%d by auid=%u",
  					  status_get->pid, old, loginuid);

  			audit_pid = status_get->pid;

  		}
  		if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)

  			err = audit_set_rate_limit(status_get->rate_limit,

  							 loginuid, sid);

  		if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)

  			err = audit_set_backlog_limit(status_get->backlog_limit,

  							loginuid, sid);

  		break;

  	case AUDIT_USER:

  	case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:

  	case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:

  		if (!audit_enabled && msg_type != AUDIT_USER_AVC)
  			return 0;

  		err = audit_filter_user(&NETLINK_CB(skb), msg_type);

  		if (err == 1) {
  			err = 0;

  			ab = audit_log_start(NULL, GFP_KERNEL, msg_type);

  			if (ab) {
  				audit_log_format(ab,

  						 "user pid=%d uid=%u auid=%u",
  						 pid, uid, loginuid);
  				if (sid) {

  					if (selinux_sid_to_string(

  							sid, &ctx, &len)) {
  						audit_log_format(ab, 

  							" ssid=%u", sid);

  						/* Maybe call audit_panic? */
  					} else
  						audit_log_format(ab, 
  							" subj=%s", ctx);
  					kfree(ctx);
  				}
  				audit_log_format(ab, " msg='%.1024s'",
  					 (char *)data);

  				audit_set_pid(ab, pid);
  				audit_log_end(ab);
  			}

  		}

  		break;
  	case AUDIT_ADD:
  	case AUDIT_DEL:

  		if (nlmsg_len(nlh) < sizeof(struct audit_rule))

  			return -EINVAL;
  		/* fallthrough */
  	case AUDIT_LIST:

  		err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,

  					   uid, seq, data, nlmsg_len(nlh),

  					   loginuid, sid);

  		break;
  	case AUDIT_ADD_RULE:
  	case AUDIT_DEL_RULE:
  		if (nlmsg_len(nlh) < sizeof(struct audit_rule_data))
  			return -EINVAL;
  		/* fallthrough */
  	case AUDIT_LIST_RULES:
  		err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
  					   uid, seq, data, nlmsg_len(nlh),

  					   loginuid, sid);

  		break;

  	case AUDIT_SIGNAL_INFO:

  		err = selinux_sid_to_string(audit_sig_sid, &ctx, &len);

  		if (err)
  			return err;
  		sig_data = kmalloc(sizeof(*sig_data) + len, GFP_KERNEL);
  		if (!sig_data) {
  			kfree(ctx);
  			return -ENOMEM;
  		}
  		sig_data->uid = audit_sig_uid;
  		sig_data->pid = audit_sig_pid;
  		memcpy(sig_data->ctx, ctx, len);
  		kfree(ctx);

  		audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO, 

  				0, 0, sig_data, sizeof(*sig_data) + len);
  		kfree(sig_data);

  		break;

  	default:
  		err = -EINVAL;
  		break;
  	}
  
  	return err < 0 ? err : 0;
  }

  /*
   * Get message from skb (based on rtnetlink_rcv_skb).  Each message is

   * processed by audit_receive_msg.  Malformed skbs with wrong length are

   * discarded silently.
   */

  static void audit_receive_skb(struct sk_buff *skb)

  {
  	int		err;
  	struct nlmsghdr	*nlh;
  	u32		rlen;
  
  	while (skb->len >= NLMSG_SPACE(0)) {
  		nlh = (struct nlmsghdr *)skb->data;
  		if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)

  			return;

  		rlen = NLMSG_ALIGN(nlh->nlmsg_len);
  		if (rlen > skb->len)
  			rlen = skb->len;
  		if ((err = audit_receive_msg(skb, nlh))) {
  			netlink_ack(skb, nlh, err);
  		} else if (nlh->nlmsg_flags & NLM_F_ACK)
  			netlink_ack(skb, nlh, 0);
  		skb_pull(skb, rlen);
  	}

  }
  
  /* Receive messages from netlink socket. */
  static void audit_receive(struct sock *sk, int length)
  {
  	struct sk_buff  *skb;

  	unsigned int qlen;

  	mutex_lock(&audit_cmd_mutex);

  	for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
  		skb = skb_dequeue(&sk->sk_receive_queue);
  		audit_receive_skb(skb);
  		kfree_skb(skb);

  	}

  	mutex_unlock(&audit_cmd_mutex);

  }

  #ifdef CONFIG_AUDITSYSCALL
  static const struct inotify_operations audit_inotify_ops = {
  	.handle_event	= audit_handle_ievent,
  	.destroy_watch	= audit_free_parent,
  };
  #endif

  
  /* Initialize audit support at boot time. */
  static int __init audit_init(void)
  {

  	int i;

  	printk(KERN_INFO "audit: initializing netlink socket (%s)
  ",
  	       audit_default ? "enabled" : "disabled");

  	audit_sock = netlink_kernel_create(NETLINK_AUDIT, 0, audit_receive,

  					   THIS_MODULE);

  	if (!audit_sock)
  		audit_panic("cannot initialize netlink socket");

  	else
  		audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;

  	skb_queue_head_init(&audit_skb_queue);

  	audit_initialized = 1;
  	audit_enabled = audit_default;

  
  	/* Register the callback with selinux.  This callback will be invoked
  	 * when a new policy is loaded. */
  	selinux_audit_set_callback(&selinux_audit_rule_update);

  	audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL, "initialized");

  
  #ifdef CONFIG_AUDITSYSCALL
  	audit_ih = inotify_init(&audit_inotify_ops);
  	if (IS_ERR(audit_ih))
  		audit_panic("cannot initialize inotify handle");

  #endif

  
  	for (i = 0; i < AUDIT_INODE_BUCKETS; i++)
  		INIT_LIST_HEAD(&audit_inode_hash[i]);

  	return 0;
  }

  __initcall(audit_init);
  
  /* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
  static int __init audit_enable(char *str)
  {
  	audit_default = !!simple_strtol(str, NULL, 0);
  	printk(KERN_INFO "audit: %s%s
  ",
  	       audit_default ? "enabled" : "disabled",
  	       audit_initialized ? "" : " (after initialization)");
  	if (audit_initialized)
  		audit_enabled = audit_default;

  	return 1;

  }
  
  __setup("audit=", audit_enable);

  static void audit_buffer_free(struct audit_buffer *ab)
  {
  	unsigned long flags;

  	if (!ab)
  		return;

  	if (ab->skb)
  		kfree_skb(ab->skb);

  	spin_lock_irqsave(&audit_freelist_lock, flags);

  	if (audit_freelist_count > AUDIT_MAXFREE)

  		kfree(ab);

  	else {
  		audit_freelist_count++;

  		list_add(&ab->list, &audit_freelist);

  	}

  	spin_unlock_irqrestore(&audit_freelist_lock, flags);
  }

  static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,

  						gfp_t gfp_mask, int type)

  {
  	unsigned long flags;
  	struct audit_buffer *ab = NULL;

  	struct nlmsghdr *nlh;

  
  	spin_lock_irqsave(&audit_freelist_lock, flags);
  	if (!list_empty(&audit_freelist)) {
  		ab = list_entry(audit_freelist.next,
  				struct audit_buffer, list);
  		list_del(&ab->list);
  		--audit_freelist_count;
  	}
  	spin_unlock_irqrestore(&audit_freelist_lock, flags);
  
  	if (!ab) {

  		ab = kmalloc(sizeof(*ab), gfp_mask);

  		if (!ab)

  			goto err;

  	}

  	ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);

  	if (!ab->skb)

  		goto err;

  	ab->ctx = ctx;

  	ab->gfp_mask = gfp_mask;

  	nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
  	nlh->nlmsg_type = type;
  	nlh->nlmsg_flags = 0;
  	nlh->nlmsg_pid = 0;
  	nlh->nlmsg_seq = 0;

  	return ab;

  err:
  	audit_buffer_free(ab);
  	return NULL;

  }

  /**
   * audit_serial - compute a serial number for the audit record
   *
   * Compute a serial number for the audit record.  Audit records are

   * written to user-space as soon as they are generated, so a complete
   * audit record may be written in several pieces.  The timestamp of the
   * record and this serial number are used by the user-space tools to
   * determine which pieces belong to the same audit record.  The
   * (timestamp,serial) tuple is unique for each syscall and is live from
   * syscall entry to syscall exit.
   *

   * NOTE: Another possibility is to store the formatted records off the
   * audit context (for those records that have a context), and emit them
   * all at syscall exit.  However, this could delay the reporting of
   * significant errors until syscall exit (or never, if the system

   * halts).
   */

  unsigned int audit_serial(void)
  {

  	static DEFINE_SPINLOCK(serial_lock);

  	static unsigned int serial = 0;
  
  	unsigned long flags;
  	unsigned int ret;

  	spin_lock_irqsave(&serial_lock, flags);

  	do {

  		ret = ++serial;
  	} while (unlikely(!ret));

  	spin_unlock_irqrestore(&serial_lock, flags);

  	return ret;

  }
  
  static inline void audit_get_stamp(struct audit_context *ctx, 
  				   struct timespec *t, unsigned int *serial)
  {
  	if (ctx)
  		auditsc_get_stamp(ctx, t, serial);
  	else {
  		*t = CURRENT_TIME;
  		*serial = audit_serial();
  	}
  }

  /* Obtain an audit buffer.  This routine does locking to obtain the
   * audit buffer, but then no locking is required for calls to
   * audit_log_*format.  If the tsk is a task that is currently in a
   * syscall, then the syscall is marked as auditable and an audit record
   * will be written at syscall exit.  If there is no associated task, tsk
   * should be NULL. */

  /**
   * audit_log_start - obtain an audit buffer
   * @ctx: audit_context (may be NULL)
   * @gfp_mask: type of allocation
   * @type: audit message type
   *
   * Returns audit_buffer pointer on success or NULL on error.
   *
   * Obtain an audit buffer.  This routine does locking to obtain the
   * audit buffer, but then no locking is required for calls to
   * audit_log_*format.  If the task (ctx) is a task that is currently in a
   * syscall, then the syscall is marked as auditable and an audit record
   * will be written at syscall exit.  If there is no associated task, then
   * task context (ctx) should be NULL.
   */

  struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,

  				     int type)

  {
  	struct audit_buffer	*ab	= NULL;

  	struct timespec		t;

  	unsigned int		serial;

  	int reserve;

  	unsigned long timeout_start = jiffies;

  
  	if (!audit_initialized)
  		return NULL;

  	if (unlikely(audit_filter_type(type)))
  		return NULL;

  	if (gfp_mask & __GFP_WAIT)
  		reserve = 0;
  	else
  		reserve = 5; /* Allow atomic callers to go up to five 
  				entries over the normal backlog limit */
  
  	while (audit_backlog_limit
  	       && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {

  		if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time
  		    && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {

  			/* Wait for auditd to drain the queue a little */
  			DECLARE_WAITQUEUE(wait, current);
  			set_current_state(TASK_INTERRUPTIBLE);
  			add_wait_queue(&audit_backlog_wait, &wait);
  
  			if (audit_backlog_limit &&
  			    skb_queue_len(&audit_skb_queue) > audit_backlog_limit)

  				schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);

  
  			__set_current_state(TASK_RUNNING);
  			remove_wait_queue(&audit_backlog_wait, &wait);

  			continue;

  		}

  		if (audit_rate_check())
  			printk(KERN_WARNING
  			       "audit: audit_backlog=%d > "
  			       "audit_backlog_limit=%d
  ",
  			       skb_queue_len(&audit_skb_queue),
  			       audit_backlog_limit);
  		audit_log_lost("backlog limit exceeded");

  		audit_backlog_wait_time = audit_backlog_wait_overflow;
  		wake_up(&audit_backlog_wait);

  		return NULL;
  	}

  	ab = audit_buffer_alloc(ctx, gfp_mask, type);

  	if (!ab) {
  		audit_log_lost("out of memory in audit_log_start");
  		return NULL;
  	}

  	audit_get_stamp(ab->ctx, &t, &serial);

  	audit_log_format(ab, "audit(%lu.%03lu:%u): ",
  			 t.tv_sec, t.tv_nsec/1000000, serial);
  	return ab;
  }

  /**

   * audit_expand - expand skb in the audit buffer

   * @ab: audit_buffer

   * @extra: space to add at tail of the skb

   *
   * Returns 0 (no space) on failed expansion, or available space if
   * successful.
   */

  static inline int audit_expand(struct audit_buffer *ab, int extra)

  {

  	struct sk_buff *skb = ab->skb;

  	int ret = pskb_expand_head(skb, skb_headroom(skb), extra,

  				   ab->gfp_mask);

  	if (ret < 0) {
  		audit_log_lost("out of memory in audit_expand");

  		return 0;

  	}
  	return skb_tailroom(skb);

  }

  /*
   * Format an audit message into the audit buffer.  If there isn't enough

   * room in the audit buffer, more room will be allocated and vsnprint
   * will be called a second time.  Currently, we assume that a printk

   * can't format message larger than 1024 bytes, so we don't either.
   */

  static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
  			      va_list args)
  {
  	int len, avail;

  	struct sk_buff *skb;

  	va_list args2;

  
  	if (!ab)
  		return;

  	BUG_ON(!ab->skb);
  	skb = ab->skb;
  	avail = skb_tailroom(skb);
  	if (avail == 0) {

  		avail = audit_expand(ab, AUDIT_BUFSIZ);

  		if (!avail)
  			goto out;

  	}

  	va_copy(args2, args);

  	len = vsnprintf(skb->tail, avail, fmt, args);

  	if (len >= avail) {
  		/* The printk buffer is 1024 bytes long, so if we get
  		 * here and AUDIT_BUFSIZ is at least 1024, then we can
  		 * log everything that printk could have logged. */

  		avail = audit_expand(ab,
  			max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail));

  		if (!avail)
  			goto out;

  		len = vsnprintf(skb->tail, avail, fmt, args2);

  	}

  	if (len > 0)
  		skb_put(skb, len);

  out:
  	return;

  }

  /**
   * audit_log_format - format a message into the audit buffer.
   * @ab: audit_buffer
   * @fmt: format string
   * @...: optional parameters matching @fmt string
   *
   * All the work is done in audit_log_vformat.
   */

  void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
  {
  	va_list args;
  
  	if (!ab)
  		return;
  	va_start(args, fmt);
  	audit_log_vformat(ab, fmt, args);
  	va_end(args);
  }

  /**
   * audit_log_hex - convert a buffer to hex and append it to the audit skb
   * @ab: the audit_buffer
   * @buf: buffer to convert to hex
   * @len: length of @buf to be converted
   *
   * No return value; failure to expand is silently ignored.
   *
   * This function will take the passed buf and convert it into a string of
   * ascii hex digits. The new string is placed onto the skb.
   */
  void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf,

  		size_t len)

  {

  	int i, avail, new_len;
  	unsigned char *ptr;
  	struct sk_buff *skb;
  	static const unsigned char *hex = "0123456789ABCDEF";

  	if (!ab)
  		return;

  	BUG_ON(!ab->skb);
  	skb = ab->skb;
  	avail = skb_tailroom(skb);
  	new_len = len<<1;
  	if (new_len >= avail) {
  		/* Round the buffer request up to the next multiple */
  		new_len = AUDIT_BUFSIZ*(((new_len-avail)/AUDIT_BUFSIZ) + 1);
  		avail = audit_expand(ab, new_len);
  		if (!avail)
  			return;
  	}

  	ptr = skb->tail;
  	for (i=0; i<len; i++) {
  		*ptr++ = hex[(buf[i] & 0xF0)>>4]; /* Upper nibble */
  		*ptr++ = hex[buf[i] & 0x0F];	  /* Lower nibble */
  	}
  	*ptr = 0;
  	skb_put(skb, len << 1); /* new string is twice the old string */

  }

  /*
   * Format a string of no more than slen characters into the audit buffer,
   * enclosed in quote marks.
   */
  static void audit_log_n_string(struct audit_buffer *ab, size_t slen,
  			       const char *string)
  {
  	int avail, new_len;
  	unsigned char *ptr;
  	struct sk_buff *skb;

  	if (!ab)
  		return;

  	BUG_ON(!ab->skb);
  	skb = ab->skb;
  	avail = skb_tailroom(skb);
  	new_len = slen + 3;	/* enclosing quotes + null terminator */
  	if (new_len > avail) {
  		avail = audit_expand(ab, new_len);
  		if (!avail)
  			return;
  	}
  	ptr = skb->tail;
  	*ptr++ = '"';
  	memcpy(ptr, string, slen);
  	ptr += slen;
  	*ptr++ = '"';
  	*ptr = 0;
  	skb_put(skb, slen + 2);	/* don't include null terminator */
  }

  /**

   * audit_log_n_unstrustedstring - log a string that may contain random characters

   * @ab: audit_buffer

   * @len: lenth of string (not including trailing null)

   * @string: string to be logged
   *
   * This code will escape a string that is passed to it if the string
   * contains a control character, unprintable character, double quote mark,

   * or a space. Unescaped strings will start and end with a double quote mark.

   * Strings that are escaped are printed in hex (2 digits per char).

   *
   * The caller specifies the number of characters in the string to log, which may
   * or may not be the entire string.

   */

  const char *audit_log_n_untrustedstring(struct audit_buffer *ab, size_t len,
  					const char *string)

  {

  	const unsigned char *p = string;

  
  	while (*p) {

  		if (*p == '"' || *p < 0x21 || *p > 0x7f) {

  			audit_log_hex(ab, string, len);
  			return string + len + 1;

  		}
  		p++;
  	}

  	audit_log_n_string(ab, len, string);

  	return p + 1;

  }

  /**
   * audit_log_unstrustedstring - log a string that may contain random characters
   * @ab: audit_buffer
   * @string: string to be logged
   *
   * Same as audit_log_n_unstrustedstring(), except that strlen is used to
   * determine string length.
   */
  const char *audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
  {
  	return audit_log_n_untrustedstring(ab, strlen(string), string);
  }

  /* This is a helper-function to print the escaped d_path */

  void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
  		      struct dentry *dentry, struct vfsmount *vfsmnt)
  {

  	char *p, *path;

  	if (prefix)
  		audit_log_format(ab, " %s", prefix);

  	/* We will allow 11 spaces for ' (deleted)' to be appended */

  	path = kmalloc(PATH_MAX+11, ab->gfp_mask);

  	if (!path) {
  		audit_log_format(ab, "<no memory>");
  		return;

  	}

  	p = d_path(dentry, vfsmnt, path, PATH_MAX+11);
  	if (IS_ERR(p)) { /* Should never happen since we send PATH_MAX */
  		/* FIXME: can we save some information here? */
  		audit_log_format(ab, "<too long>");
  	} else 
  		audit_log_untrustedstring(ab, p);
  	kfree(path);

  }

  /**
   * audit_log_end - end one audit record
   * @ab: the audit_buffer
   *
   * The netlink_* functions cannot be called inside an irq context, so
   * the audit buffer is placed on a queue and a tasklet is scheduled to

   * remove them from the queue outside the irq context.  May be called in

   * any context.
   */

  void audit_log_end(struct audit_buffer *ab)

  {

  	if (!ab)
  		return;
  	if (!audit_rate_check()) {
  		audit_log_lost("rate limit exceeded");
  	} else {

  		if (audit_pid) {
  			struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
  			nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0);
  			skb_queue_tail(&audit_skb_queue, ab->skb);
  			ab->skb = NULL;
  			wake_up_interruptible(&kauditd_wait);
  		} else {

  			printk(KERN_NOTICE "%s
  ", ab->skb->data + NLMSG_SPACE(0));

  		}

  	}

  	audit_buffer_free(ab);

  }

  /**
   * audit_log - Log an audit record
   * @ctx: audit context
   * @gfp_mask: type of allocation
   * @type: audit message type
   * @fmt: format string to use
   * @...: variable parameters matching the format string
   *
   * This is a convenience function that calls audit_log_start,
   * audit_log_vformat, and audit_log_end.  It may be called
   * in any context.
   */

  void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type, 

  	       const char *fmt, ...)

  {
  	struct audit_buffer *ab;
  	va_list args;

  	ab = audit_log_start(ctx, gfp_mask, type);

  	if (ab) {
  		va_start(args, fmt);
  		audit_log_vformat(ab, fmt, args);
  		va_end(args);
  		audit_log_end(ab);
  	}
  }

  
  EXPORT_SYMBOL(audit_log_start);
  EXPORT_SYMBOL(audit_log_end);
  EXPORT_SYMBOL(audit_log_format);
  EXPORT_SYMBOL(audit_log);