Logo Search packages:      
Sourcecode: linux version File versions  Download package

audit.c

/* 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 2003-2007 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 <linux/tty.h>

#include "audit.h"

/* No auditing will take place until audit_initialized != 0.
 * (Initialization happens after skb_init is called.) */
static int  audit_initialized;

/* 0 - no auditing
 * 1 - auditing enabled
 * 2 - auditing enabled and configuration is locked/unchangeable. */
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 = nlmsg_hdr(ab->skb);
      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\n", message);
            break;
      case AUDIT_FAIL_PANIC:
            panic("audit: %s\n", 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\n",
                   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 res, rc = 0, old = audit_rate_limit;

      /* check if we are locked */
      if (audit_enabled == 2)
            res = 0;
      else
            res = 1;

      if (sid) {
            char *ctx = NULL;
            u32 len;
            if ((rc = selinux_sid_to_string(sid, &ctx, &len)) == 0) {
                  audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
                        "audit_rate_limit=%d old=%d by auid=%u"
                        " subj=%s res=%d",
                        limit, old, loginuid, ctx, res);
                  kfree(ctx);
            } else
                  res = 0; /* Something weird, deny request */
      }
      audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
            "audit_rate_limit=%d old=%d by auid=%u res=%d",
            limit, old, loginuid, res);

      /* If we are allowed, make the change */
      if (res == 1)
            audit_rate_limit = limit;
      /* Not allowed, update reason */
      else if (rc == 0)
            rc = -EPERM;
      return rc;
}

static int audit_set_backlog_limit(int limit, uid_t loginuid, u32 sid)
{
      int res, rc = 0, old = audit_backlog_limit;

      /* check if we are locked */
      if (audit_enabled == 2)
            res = 0;
      else
            res = 1;

      if (sid) {
            char *ctx = NULL;
            u32 len;
            if ((rc = selinux_sid_to_string(sid, &ctx, &len)) == 0) {
                  audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
                        "audit_backlog_limit=%d old=%d by auid=%u"
                        " subj=%s res=%d",
                        limit, old, loginuid, ctx, res);
                  kfree(ctx);
            } else
                  res = 0; /* Something weird, deny request */
      }
      audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
            "audit_backlog_limit=%d old=%d by auid=%u res=%d",
            limit, old, loginuid, res);

      /* If we are allowed, make the change */
      if (res == 1)
            audit_backlog_limit = limit;
      /* Not allowed, update reason */
      else if (rc == 0)
            rc = -EPERM;
      return rc;
}

static int audit_set_enabled(int state, uid_t loginuid, u32 sid)
{
      int res, rc = 0, old = audit_enabled;

      if (state < 0 || state > 2)
            return -EINVAL;

      /* check if we are locked */
      if (audit_enabled == 2)
            res = 0;
      else
            res = 1;

      if (sid) {
            char *ctx = NULL;
            u32 len;
            if ((rc = selinux_sid_to_string(sid, &ctx, &len)) == 0) {
                  audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
                        "audit_enabled=%d old=%d by auid=%u"
                        " subj=%s res=%d",
                        state, old, loginuid, ctx, res);
                  kfree(ctx);
            } else
                  res = 0; /* Something weird, deny request */
      }
      audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
            "audit_enabled=%d old=%d by auid=%u res=%d",
            state, old, loginuid, res);

      /* If we are allowed, make the change */
      if (res == 1)
            audit_enabled = state;
      /* Not allowed, update reason */
      else if (rc == 0)
            rc = -EPERM;
      return rc;
}

static int audit_set_failure(int state, uid_t loginuid, u32 sid)
{
      int res, rc = 0, old = audit_failure;

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

      /* check if we are locked */
      if (audit_enabled == 2)
            res = 0;
      else
            res = 1;

      if (sid) {
            char *ctx = NULL;
            u32 len;
            if ((rc = selinux_sid_to_string(sid, &ctx, &len)) == 0) {
                  audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
                        "audit_failure=%d old=%d by auid=%u"
                        " subj=%s res=%d",
                        state, old, loginuid, ctx, res);
                  kfree(ctx);
            } else
                  res = 0; /* Something weird, deny request */
      }
      audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
            "audit_failure=%d old=%d by auid=%u res=%d",
            state, old, loginuid, res);

      /* If we are allowed, make the change */
      if (res == 1)
            audit_failure = state;
      /* Not allowed, update reason */
      else if (rc == 0)
            rc = -EPERM;
      return rc;
}

static int kauditd_thread(void *dummy)
{
      struct sk_buff *skb;

      set_freezable();
      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\n", audit_pid);
                              audit_pid = 0;
                        }
                  } else {
                        printk(KERN_NOTICE "%s\n", 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;
}

static int audit_prepare_user_tty(pid_t pid, uid_t loginuid)
{
      struct task_struct *tsk;
      int err;

      read_lock(&tasklist_lock);
      tsk = find_task_by_pid(pid);
      err = -ESRCH;
      if (!tsk)
            goto out;
      err = 0;

      spin_lock_irq(&tsk->sighand->siglock);
      if (!tsk->signal->audit_tty)
            err = -EPERM;
      spin_unlock_irq(&tsk->sighand->siglock);
      if (err)
            goto out;

      tty_audit_push_task(tsk, loginuid);
out:
      read_unlock(&tasklist_lock);
      return err;
}

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;
}

#ifdef CONFIG_AUDIT_TREE
static int prune_tree_thread(void *unused)
{
      mutex_lock(&audit_cmd_mutex);
      audit_prune_trees();
      mutex_unlock(&audit_cmd_mutex);
      return 0;
}

void audit_schedule_prune(void)
{
      kthread_run(prune_tree_thread, NULL, "audit_prune_tree");
}
#endif

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:
      case AUDIT_TTY_GET:
      case AUDIT_TTY_SET:
      case AUDIT_TRIM:
      case AUDIT_MAKE_EQUIV:
            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;
                  if (msg_type == AUDIT_USER_TTY) {
                        err = audit_prepare_user_tty(pid, loginuid);
                        if (err)
                              break;
                  }
                  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);
                        }
                        if (msg_type != AUDIT_USER_TTY)
                              audit_log_format(ab, " msg='%.1024s'",
                                           (char *)data);
                        else {
                              int size;

                              audit_log_format(ab, " msg=");
                              size = nlmsg_len(nlh);
                              audit_log_n_untrustedstring(ab, size,
                                                    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;
            if (audit_enabled == 2) {
                  ab = audit_log_start(NULL, GFP_KERNEL,
                              AUDIT_CONFIG_CHANGE);
                  if (ab) {
                        audit_log_format(ab,
                                     "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, " audit_enabled=%d res=0",
                              audit_enabled);
                        audit_log_end(ab);
                  }
                  return -EPERM;
            }
            /* 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;
            if (audit_enabled == 2) {
                  ab = audit_log_start(NULL, GFP_KERNEL,
                              AUDIT_CONFIG_CHANGE);
                  if (ab) {
                        audit_log_format(ab,
                                     "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, " audit_enabled=%d res=0",
                              audit_enabled);
                        audit_log_end(ab);
                  }
                  return -EPERM;
            }
            /* 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_TRIM:
            audit_trim_trees();
            ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
            if (!ab)
                  break;
            audit_log_format(ab, "auid=%u", loginuid);
            if (sid) {
                  u32 len;
                  ctx = NULL;
                  if (selinux_sid_to_string(sid, &ctx, &len))
                        audit_log_format(ab, " ssid=%u", sid);
                  else
                        audit_log_format(ab, " subj=%s", ctx);
                  kfree(ctx);
            }
            audit_log_format(ab, " op=trim res=1");
            audit_log_end(ab);
            break;
      case AUDIT_MAKE_EQUIV: {
            void *bufp = data;
            u32 sizes[2];
            size_t len = nlmsg_len(nlh);
            char *old, *new;

            err = -EINVAL;
            if (len < 2 * sizeof(u32))
                  break;
            memcpy(sizes, bufp, 2 * sizeof(u32));
            bufp += 2 * sizeof(u32);
            len -= 2 * sizeof(u32);
            old = audit_unpack_string(&bufp, &len, sizes[0]);
            if (IS_ERR(old)) {
                  err = PTR_ERR(old);
                  break;
            }
            new = audit_unpack_string(&bufp, &len, sizes[1]);
            if (IS_ERR(new)) {
                  err = PTR_ERR(new);
                  kfree(old);
                  break;
            }
            /* OK, here comes... */
            err = audit_tag_tree(old, new);

            ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE);
            if (!ab) {
                  kfree(old);
                  kfree(new);
                  break;
            }
            audit_log_format(ab, "auid=%u", loginuid);
            if (sid) {
                  u32 len;
                  ctx = NULL;
                  if (selinux_sid_to_string(sid, &ctx, &len))
                        audit_log_format(ab, " ssid=%u", sid);
                  else
                        audit_log_format(ab, " subj=%s", ctx);
                  kfree(ctx);
            }
            audit_log_format(ab, " op=make_equiv old=");
            audit_log_untrustedstring(ab, old);
            audit_log_format(ab, " new=");
            audit_log_untrustedstring(ab, new);
            audit_log_format(ab, " res=%d", !err);
            audit_log_end(ab);
            kfree(old);
            kfree(new);
            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;
      case AUDIT_TTY_GET: {
            struct audit_tty_status s;
            struct task_struct *tsk;

            read_lock(&tasklist_lock);
            tsk = find_task_by_pid(pid);
            if (!tsk)
                  err = -ESRCH;
            else {
                  spin_lock_irq(&tsk->sighand->siglock);
                  s.enabled = tsk->signal->audit_tty != 0;
                  spin_unlock_irq(&tsk->sighand->siglock);
            }
            read_unlock(&tasklist_lock);
            audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_TTY_GET, 0, 0,
                         &s, sizeof(s));
            break;
      }
      case AUDIT_TTY_SET: {
            struct audit_tty_status *s;
            struct task_struct *tsk;

            if (nlh->nlmsg_len < sizeof(struct audit_tty_status))
                  return -EINVAL;
            s = data;
            if (s->enabled != 0 && s->enabled != 1)
                  return -EINVAL;
            read_lock(&tasklist_lock);
            tsk = find_task_by_pid(pid);
            if (!tsk)
                  err = -ESRCH;
            else {
                  spin_lock_irq(&tsk->sighand->siglock);
                  tsk->signal->audit_tty = s->enabled != 0;
                  spin_unlock_irq(&tsk->sighand->siglock);
            }
            read_unlock(&tasklist_lock);
            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 = nlmsg_hdr(skb);
            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 sk_buff  *skb)
{
      mutex_lock(&audit_cmd_mutex);
      audit_receive_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)\n",
             audit_default ? "enabled" : "disabled");
      audit_sock = netlink_kernel_create(&init_net, NETLINK_AUDIT, 0,
                                 audit_receive, NULL, 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\n",
             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\n",
                         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_pointer(skb), 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_pointer(skb), 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_pointer(skb);
      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_pointer(skb);
      *ptr++ = '"';
      memcpy(ptr, string, slen);
      ptr += slen;
      *ptr++ = '"';
      *ptr = 0;
      skb_put(skb, slen + 2); /* don't include null terminator */
}

/**
 * audit_log_n_untrustedstring - 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;

      for (p = string; p < (const unsigned char *)string + len && *p; p++) {
            if (*p == '"' || *p < 0x21 || *p > 0x7f) {
                  audit_log_hex(ab, string, len);
                  return string + len + 1;
            }
      }
      audit_log_n_string(ab, len, string);
      return p + 1;
}

/**
 * audit_log_untrustedstring - log a string that may contain random characters
 * @ab: audit_buffer
 * @string: string to be logged
 *
 * Same as audit_log_n_untrustedstring(), 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 = nlmsg_hdr(ab->skb);
                  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\n", 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);

Generated by  Doxygen 1.6.0   Back to index