kernel/audit.c

   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
   4  *
   5  * Copyright 2003-2004 Red Hat Inc., Durham, North Carolina.
   6  * All Rights Reserved.
   7  *
   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.
  12  *
  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.
  17  *
  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
  21  *
  22  * Written by Rickard E. (Rik) Faith <faith@redhat.com>
  23  *
  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
  29  *              generation time):
  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
  36  *           current syscall).
  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.
  40  *
  41  * Example user-space utilities: http://people.redhat.com/sgrubb/audit/
  42  */
  43
  44 #include <linux/init.h>
  45 #include <asm/types.h>
  46 #include <asm/atomic.h>
  47 #include <linux/mm.h>
  48 #include <linux/module.h>
  49 #include <linux/err.h>
  50 #include <linux/kthread.h>
  51
  52 #include <linux/audit.h>
  53
  54 #include <net/sock.h>
  55 #include <net/netlink.h>
  56 #include <linux/skbuff.h>
  57 #include <linux/netlink.h>
  58 #include <linux/selinux.h>
  59
  60 #include "audit.h"
  61
  62 /* No auditing will take place until audit_initialized != 0.
  63  * (Initialization happens after skb_init is called.) */
  64 static int      audit_initialized;
  65
  66 /* No syscall auditing will take place unless audit_enabled != 0. */
  67 int             audit_enabled;
  68
  69 /* Default state when kernel boots without any parameters. */
  70 static int      audit_default;
  71
  72 /* If auditing cannot proceed, audit_failure selects what happens. */
  73 static int      audit_failure = AUDIT_FAIL_PRINTK;
  74
  75 /* If audit records are to be written to the netlink socket, audit_pid
  76  * contains the (non-zero) pid. */
  77 int             audit_pid;
  78
  79 /* If audit_rate_limit is non-zero, limit the rate of sending audit records
  80  * to that number per second.  This prevents DoS attacks, but results in
  81  * audit records being dropped. */
  82 static int      audit_rate_limit;
  83
  84 /* Number of outstanding audit_buffers allowed. */
  85 static int      audit_backlog_limit = 64;
  86 static int      audit_backlog_wait_time = 60 * HZ;
  87 static int      audit_backlog_wait_overflow = 0;
  88
  89 /* The identity of the user shutting down the audit system. */
  90 uid_t           audit_sig_uid = -1;
  91 pid_t           audit_sig_pid = -1;
  92
  93 /* Records can be lost in several ways:
  94    0) [suppressed in audit_alloc]
  95    1) out of memory in audit_log_start [kmalloc of struct audit_buffer]
  96    2) out of memory in audit_log_move [alloc_skb]
  97    3) suppressed due to audit_rate_limit
  98    4) suppressed due to audit_backlog_limit
  99 */
 100 static atomic_t    audit_lost = ATOMIC_INIT(0);
 101
 102 /* The netlink socket. */
 103 static struct sock *audit_sock;
 104
 105 /* The audit_freelist is a list of pre-allocated audit buffers (if more
 106  * than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
 107  * being placed on the freelist). */
 108 static DEFINE_SPINLOCK(audit_freelist_lock);
 109 static int         audit_freelist_count;
 110 static LIST_HEAD(audit_freelist);
 111
 112 static struct sk_buff_head audit_skb_queue;
 113 static struct task_struct *kauditd_task;
 114 static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);
 115 static DECLARE_WAIT_QUEUE_HEAD(audit_backlog_wait);
 116
 117 /* The netlink socket is only to be read by 1 CPU, which lets us assume
 118  * that list additions and deletions never happen simultaneously in
 119  * auditsc.c */
 120 DEFINE_MUTEX(audit_netlink_mutex);
 121
 122 /* AUDIT_BUFSIZ is the size of the temporary buffer used for formatting
 123  * audit records.  Since printk uses a 1024 byte buffer, this buffer
 124  * should be at least that large. */
 125 #define AUDIT_BUFSIZ 1024
 126
 127 /* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the
 128  * audit_freelist.  Doing so eliminates many kmalloc/kfree calls. */
 129 #define AUDIT_MAXFREE  (2*NR_CPUS)
 130
 131 /* The audit_buffer is used when formatting an audit record.  The caller
 132  * locks briefly to get the record off the freelist or to allocate the
 133  * buffer, and locks briefly to send the buffer to the netlink layer or
 134  * to place it on a transmit queue.  Multiple audit_buffers can be in
 135  * use simultaneously. */
 136 struct audit_buffer {
 137         struct list_head     list;
 138         struct sk_buff       *skb;      /* formatted skb ready to send */
 139         struct audit_context *ctx;      /* NULL or associated context */
 140         gfp_t                gfp_mask;
 141 };
 142
 143 static void audit_set_pid(struct audit_buffer *ab, pid_t pid)
 144 {
 145         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
 146         nlh->nlmsg_pid = pid;
 147 }
 148
 149 void audit_panic(const char *message)
 150 {
 151         switch (audit_failure)
 152         {
 153         case AUDIT_FAIL_SILENT:
 154                 break;
 155         case AUDIT_FAIL_PRINTK:
 156                 printk(KERN_ERR "audit: %s\n", message);
 157                 break;
 158         case AUDIT_FAIL_PANIC:
 159                 panic("audit: %s\n", message);
 160                 break;
 161         }
 162 }
 163
 164 static inline int audit_rate_check(void)
 165 {
 166         static unsigned long    last_check = 0;
 167         static int              messages   = 0;
 168         static DEFINE_SPINLOCK(lock);
 169         unsigned long           flags;
 170         unsigned long           now;
 171         unsigned long           elapsed;
 172         int                     retval     = 0;
 173
 174         if (!audit_rate_limit) return 1;
 175
 176         spin_lock_irqsave(&lock, flags);
 177         if (++messages < audit_rate_limit) {
 178                 retval = 1;
 179         } else {
 180                 now     = jiffies;
 181                 elapsed = now - last_check;
 182                 if (elapsed > HZ) {
 183                         last_check = now;
 184                         messages   = 0;
 185                         retval     = 1;
 186                 }
 187         }
 188         spin_unlock_irqrestore(&lock, flags);
 189
 190         return retval;
 191 }
 192
 193 /**
 194  * audit_log_lost - conditionally log lost audit message event
 195  * @message: the message stating reason for lost audit message
 196  *
 197  * Emit at least 1 message per second, even if audit_rate_check is
 198  * throttling.
 199  * Always increment the lost messages counter.
 200 */
 201 void audit_log_lost(const char *message)
 202 {
 203         static unsigned long    last_msg = 0;
 204         static DEFINE_SPINLOCK(lock);
 205         unsigned long           flags;
 206         unsigned long           now;
 207         int                     print;
 208
 209         atomic_inc(&audit_lost);
 210
 211         print = (audit_failure == AUDIT_FAIL_PANIC || !audit_rate_limit);
 212
 213         if (!print) {
 214                 spin_lock_irqsave(&lock, flags);
 215                 now = jiffies;
 216                 if (now - last_msg > HZ) {
 217                         print = 1;
 218                         last_msg = now;
 219                 }
 220                 spin_unlock_irqrestore(&lock, flags);
 221         }
 222
 223         if (print) {
 224                 printk(KERN_WARNING
 225                        "audit: audit_lost=%d audit_rate_limit=%d audit_backlog_limit=%d\n",
 226                        atomic_read(&audit_lost),
 227                        audit_rate_limit,
 228                        audit_backlog_limit);
 229                 audit_panic(message);
 230         }
 231 }
 232
 233 static int audit_set_rate_limit(int limit, uid_t loginuid, u32 sid)
 234 {
 235         int old = audit_rate_limit;
 236
 237         if (sid) {
 238                 char *ctx = NULL;
 239                 u32 len;
 240                 int rc;
 241                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 242                         return rc;
 243                 else
 244                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 245                                 "audit_rate_limit=%d old=%d by auid=%u subj=%s",
 246                                 limit, old, loginuid, ctx);
 247                 kfree(ctx);
 248         } else
 249                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 250                         "audit_rate_limit=%d old=%d by auid=%u",
 251                         limit, old, loginuid);
 252         audit_rate_limit = limit;
 253         return old;
 254 }
 255
 256 static int audit_set_backlog_limit(int limit, uid_t loginuid, u32 sid)
 257 {
 258         int old = audit_backlog_limit;
 259
 260         if (sid) {
 261                 char *ctx = NULL;
 262                 u32 len;
 263                 int rc;
 264                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 265                         return rc;
 266                 else
 267                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 268                             "audit_backlog_limit=%d old=%d by auid=%u subj=%s",
 269                                 limit, old, loginuid, ctx);
 270                 kfree(ctx);
 271         } else
 272                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 273                         "audit_backlog_limit=%d old=%d by auid=%u",
 274                         limit, old, loginuid);
 275         audit_backlog_limit = limit;
 276         return old;
 277 }
 278
 279 static int audit_set_enabled(int state, uid_t loginuid, u32 sid)
 280 {
 281         int old = audit_enabled;
 282
 283         if (state != 0 && state != 1)
 284                 return -EINVAL;
 285
 286         if (sid) {
 287                 char *ctx = NULL;
 288                 u32 len;
 289                 int rc;
 290                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 291                         return rc;
 292                 else
 293                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 294                                 "audit_enabled=%d old=%d by auid=%u subj=%s",
 295                                 state, old, loginuid, ctx);
 296                 kfree(ctx);
 297         } else
 298                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 299                         "audit_enabled=%d old=%d by auid=%u",
 300                         state, old, loginuid);
 301         audit_enabled = state;
 302         return old;
 303 }
 304
 305 static int audit_set_failure(int state, uid_t loginuid, u32 sid)
 306 {
 307         int old = audit_failure;
 308
 309         if (state != AUDIT_FAIL_SILENT
 310             && state != AUDIT_FAIL_PRINTK
 311             && state != AUDIT_FAIL_PANIC)
 312                 return -EINVAL;
 313
 314         if (sid) {
 315                 char *ctx = NULL;
 316                 u32 len;
 317                 int rc;
 318                 if ((rc = selinux_ctxid_to_string(sid, &ctx, &len)))
 319                         return rc;
 320                 else
 321                         audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 322                                 "audit_failure=%d old=%d by auid=%u subj=%s",
 323                                 state, old, loginuid, ctx);
 324                 kfree(ctx);
 325         } else
 326                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 327                         "audit_failure=%d old=%d by auid=%u",
 328                         state, old, loginuid);
 329         audit_failure = state;
 330         return old;
 331 }
 332
 333 static int kauditd_thread(void *dummy)
 334 {
 335         struct sk_buff *skb;
 336
 337         while (1) {
 338                 skb = skb_dequeue(&audit_skb_queue);
 339                 wake_up(&audit_backlog_wait);
 340                 if (skb) {
 341                         if (audit_pid) {
 342                                 int err = netlink_unicast(audit_sock, skb, audit_pid, 0);
 343                                 if (err < 0) {
 344                                         BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */
 345                                         printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
 346                                         audit_pid = 0;
 347                                 }
 348                         } else {
 349                                 printk(KERN_NOTICE "%s\n", skb->data + NLMSG_SPACE(0));
 350                                 kfree_skb(skb);
 351                         }
 352                 } else {
 353                         DECLARE_WAITQUEUE(wait, current);
 354                         set_current_state(TASK_INTERRUPTIBLE);
 355                         add_wait_queue(&kauditd_wait, &wait);
 356
 357                         if (!skb_queue_len(&audit_skb_queue)) {
 358                                 try_to_freeze();
 359                                 schedule();
 360                         }
 361
 362                         __set_current_state(TASK_RUNNING);
 363                         remove_wait_queue(&kauditd_wait, &wait);
 364                 }
 365         }
 366         return 0;
 367 }
 368
 369 /**
 370  * audit_send_reply - send an audit reply message via netlink
 371  * @pid: process id to send reply to
 372  * @seq: sequence number
 373  * @type: audit message type
 374  * @done: done (last) flag
 375  * @multi: multi-part message flag
 376  * @payload: payload data
 377  * @size: payload size
 378  *
 379  * Allocates an skb, builds the netlink message, and sends it to the pid.
 380  * No failure notifications.
 381  */
 382 void audit_send_reply(int pid, int seq, int type, int done, int multi,
 383                       void *payload, int size)
 384 {
 385         struct sk_buff  *skb;
 386         struct nlmsghdr *nlh;
 387         int             len = NLMSG_SPACE(size);
 388         void            *data;
 389         int             flags = multi ? NLM_F_MULTI : 0;
 390         int             t     = done  ? NLMSG_DONE  : type;
 391
 392         skb = alloc_skb(len, GFP_KERNEL);
 393         if (!skb)
 394                 return;
 395
 396         nlh              = NLMSG_PUT(skb, pid, seq, t, size);
 397         nlh->nlmsg_flags = flags;
 398         data             = NLMSG_DATA(nlh);
 399         memcpy(data, payload, size);
 400
 401         /* Ignore failure. It'll only happen if the sender goes away,
 402            because our timeout is set to infinite. */
 403         netlink_unicast(audit_sock, skb, pid, 0);
 404         return;
 405
 406 nlmsg_failure:                  /* Used by NLMSG_PUT */
 407         if (skb)
 408                 kfree_skb(skb);
 409 }
 410
 411 /*
 412  * Check for appropriate CAP_AUDIT_ capabilities on incoming audit
 413  * control messages.
 414  */
 415 static int audit_netlink_ok(kernel_cap_t eff_cap, u16 msg_type)
 416 {
 417         int err = 0;
 418
 419         switch (msg_type) {
 420         case AUDIT_GET:
 421         case AUDIT_LIST:
 422         case AUDIT_LIST_RULES:
 423         case AUDIT_SET:
 424         case AUDIT_ADD:
 425         case AUDIT_ADD_RULE:
 426         case AUDIT_DEL:
 427         case AUDIT_DEL_RULE:
 428         case AUDIT_SIGNAL_INFO:
 429                 if (!cap_raised(eff_cap, CAP_AUDIT_CONTROL))
 430                         err = -EPERM;
 431                 break;
 432         case AUDIT_USER:
 433         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 434         case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:
 435                 if (!cap_raised(eff_cap, CAP_AUDIT_WRITE))
 436                         err = -EPERM;
 437                 break;
 438         default:  /* bad msg */
 439                 err = -EINVAL;
 440         }
 441
 442         return err;
 443 }
 444
 445 static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 446 {
 447         u32                     uid, pid, seq, sid;
 448         void                    *data;
 449         struct audit_status     *status_get, status_set;
 450         int                     err;
 451         struct audit_buffer     *ab;
 452         u16                     msg_type = nlh->nlmsg_type;
 453         uid_t                   loginuid; /* loginuid of sender */
 454         struct audit_sig_info   sig_data;
 455
 456         err = audit_netlink_ok(NETLINK_CB(skb).eff_cap, msg_type);
 457         if (err)
 458                 return err;
 459
 460         /* As soon as there's any sign of userspace auditd,
 461          * start kauditd to talk to it */
 462         if (!kauditd_task)
 463                 kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
 464         if (IS_ERR(kauditd_task)) {
 465                 err = PTR_ERR(kauditd_task);
 466                 kauditd_task = NULL;
 467                 return err;
 468         }
 469
 470         pid  = NETLINK_CREDS(skb)->pid;
 471         uid  = NETLINK_CREDS(skb)->uid;
 472         loginuid = NETLINK_CB(skb).loginuid;
 473         sid  = NETLINK_CB(skb).sid;
 474         seq  = nlh->nlmsg_seq;
 475         data = NLMSG_DATA(nlh);
 476
 477         switch (msg_type) {
 478         case AUDIT_GET:
 479                 status_set.enabled       = audit_enabled;
 480                 status_set.failure       = audit_failure;
 481                 status_set.pid           = audit_pid;
 482                 status_set.rate_limit    = audit_rate_limit;
 483                 status_set.backlog_limit = audit_backlog_limit;
 484                 status_set.lost          = atomic_read(&audit_lost);
 485                 status_set.backlog       = skb_queue_len(&audit_skb_queue);
 486                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
 487                                  &status_set, sizeof(status_set));
 488                 break;
 489         case AUDIT_SET:
 490                 if (nlh->nlmsg_len < sizeof(struct audit_status))
 491                         return -EINVAL;
 492                 status_get   = (struct audit_status *)data;
 493                 if (status_get->mask & AUDIT_STATUS_ENABLED) {
 494                         err = audit_set_enabled(status_get->enabled,
 495                                                         loginuid, sid);
 496                         if (err < 0) return err;
 497                 }
 498                 if (status_get->mask & AUDIT_STATUS_FAILURE) {
 499                         err = audit_set_failure(status_get->failure,
 500                                                          loginuid, sid);
 501                         if (err < 0) return err;
 502                 }
 503                 if (status_get->mask & AUDIT_STATUS_PID) {
 504                         int old   = audit_pid;
 505                         if (sid) {
 506                                 char *ctx = NULL;
 507                                 u32 len;
 508                                 int rc;
 509                                 if ((rc = selinux_ctxid_to_string(
 510                                                 sid, &ctx, &len)))
 511                                         return rc;
 512                                 else
 513                                         audit_log(NULL, GFP_KERNEL,
 514                                                 AUDIT_CONFIG_CHANGE,
 515                                                 "audit_pid=%d old=%d by auid=%u subj=%s",
 516                                                 status_get->pid, old,
 517                                                 loginuid, ctx);
 518                                 kfree(ctx);
 519                         } else
 520                                 audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE,
 521                                         "audit_pid=%d old=%d by auid=%u",
 522                                           status_get->pid, old, loginuid);
 523                         audit_pid = status_get->pid;
 524                 }
 525                 if (status_get->mask & AUDIT_STATUS_RATE_LIMIT)
 526                         audit_set_rate_limit(status_get->rate_limit,
 527                                                          loginuid, sid);
 528                 if (status_get->mask & AUDIT_STATUS_BACKLOG_LIMIT)
 529                         audit_set_backlog_limit(status_get->backlog_limit,
 530                                                         loginuid, sid);
 531                 break;
 532         case AUDIT_USER:
 533         case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG:
 534         case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2:
 535                 if (!audit_enabled && msg_type != AUDIT_USER_AVC)
 536                         return 0;
 537
 538                 err = audit_filter_user(&NETLINK_CB(skb), msg_type);
 539                 if (err == 1) {
 540                         err = 0;
 541                         ab = audit_log_start(NULL, GFP_KERNEL, msg_type);
 542                         if (ab) {
 543                                 audit_log_format(ab,
 544                                                  "user pid=%d uid=%u auid=%u",
 545                                                  pid, uid, loginuid);
 546                                 if (sid) {
 547                                         char *ctx = NULL;
 548                                         u32 len;
 549                                         if (selinux_ctxid_to_string(
 550                                                         sid, &ctx, &len)) {
 551                                                 audit_log_format(ab,
 552                                                         " ssid=%u", sid);
 553                                                 /* Maybe call audit_panic? */
 554                                         } else
 555                                                 audit_log_format(ab,
 556                                                         " subj=%s", ctx);
 557                                         kfree(ctx);
 558                                 }
 559                                 audit_log_format(ab, " msg='%.1024s'",
 560                                          (char *)data);
 561                                 audit_set_pid(ab, pid);
 562                                 audit_log_end(ab);
 563                         }
 564                 }
 565                 break;
 566         case AUDIT_ADD:
 567         case AUDIT_DEL:
 568                 if (nlmsg_len(nlh) < sizeof(struct audit_rule))
 569                         return -EINVAL;
 570                 /* fallthrough */
 571         case AUDIT_LIST:
 572                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 573                                            uid, seq, data, nlmsg_len(nlh),
 574                                            loginuid, sid);
 575                 break;
 576         case AUDIT_ADD_RULE:
 577         case AUDIT_DEL_RULE:
 578                 if (nlmsg_len(nlh) < sizeof(struct audit_rule_data))
 579                         return -EINVAL;
 580                 /* fallthrough */
 581         case AUDIT_LIST_RULES:
 582                 err = audit_receive_filter(nlh->nlmsg_type, NETLINK_CB(skb).pid,
 583                                            uid, seq, data, nlmsg_len(nlh),
 584                                            loginuid, sid);
 585                 break;
 586         case AUDIT_SIGNAL_INFO:
 587                 sig_data.uid = audit_sig_uid;
 588                 sig_data.pid = audit_sig_pid;
 589                 audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_SIGNAL_INFO,
 590                                 0, 0, &sig_data, sizeof(sig_data));
 591                 break;
 592         default:
 593                 err = -EINVAL;
 594                 break;
 595         }
 596
 597         return err < 0 ? err : 0;
 598 }
 599
 600 /*
 601  * Get message from skb (based on rtnetlink_rcv_skb).  Each message is
 602  * processed by audit_receive_msg.  Malformed skbs with wrong length are
 603  * discarded silently.
 604  */
 605 static void audit_receive_skb(struct sk_buff *skb)
 606 {
 607         int             err;
 608         struct nlmsghdr *nlh;
 609         u32             rlen;
 610
 611         while (skb->len >= NLMSG_SPACE(0)) {
 612                 nlh = (struct nlmsghdr *)skb->data;
 613                 if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
 614                         return;
 615                 rlen = NLMSG_ALIGN(nlh->nlmsg_len);
 616                 if (rlen > skb->len)
 617                         rlen = skb->len;
 618                 if ((err = audit_receive_msg(skb, nlh))) {
 619                         netlink_ack(skb, nlh, err);
 620                 } else if (nlh->nlmsg_flags & NLM_F_ACK)
 621                         netlink_ack(skb, nlh, 0);
 622                 skb_pull(skb, rlen);
 623         }
 624 }
 625
 626 /* Receive messages from netlink socket. */
 627 static void audit_receive(struct sock *sk, int length)
 628 {
 629         struct sk_buff  *skb;
 630         unsigned int qlen;
 631
 632         mutex_lock(&audit_netlink_mutex);
 633
 634         for (qlen = skb_queue_len(&sk->sk_receive_queue); qlen; qlen--) {
 635                 skb = skb_dequeue(&sk->sk_receive_queue);
 636                 audit_receive_skb(skb);
 637                 kfree_skb(skb);
 638         }
 639         mutex_unlock(&audit_netlink_mutex);
 640 }
 641
 642
 643 /* Initialize audit support at boot time. */
 644 static int __init audit_init(void)
 645 {
 646         printk(KERN_INFO "audit: initializing netlink socket (%s)\n",
 647                audit_default ? "enabled" : "disabled");
 648         audit_sock = netlink_kernel_create(NETLINK_AUDIT, 0, audit_receive,
 649                                            THIS_MODULE);
 650         if (!audit_sock)
 651                 audit_panic("cannot initialize netlink socket");
 652         else
 653                 audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
 654
 655         skb_queue_head_init(&audit_skb_queue);
 656         audit_initialized = 1;
 657         audit_enabled = audit_default;
 658
 659         /* Register the callback with selinux.  This callback will be invoked
 660          * when a new policy is loaded. */
 661         selinux_audit_set_callback(&selinux_audit_rule_update);
 662
 663         audit_log(NULL, GFP_KERNEL, AUDIT_KERNEL, "initialized");
 664         return 0;
 665 }
 666 __initcall(audit_init);
 667
 668 /* Process kernel command-line parameter at boot time.  audit=0 or audit=1. */
 669 static int __init audit_enable(char *str)
 670 {
 671         audit_default = !!simple_strtol(str, NULL, 0);
 672         printk(KERN_INFO "audit: %s%s\n",
 673                audit_default ? "enabled" : "disabled",
 674                audit_initialized ? "" : " (after initialization)");
 675         if (audit_initialized)
 676                 audit_enabled = audit_default;
 677         return 1;
 678 }
 679
 680 __setup("audit=", audit_enable);
 681
 682 static void audit_buffer_free(struct audit_buffer *ab)
 683 {
 684         unsigned long flags;
 685
 686         if (!ab)
 687                 return;
 688
 689         if (ab->skb)
 690                 kfree_skb(ab->skb);
 691
 692         spin_lock_irqsave(&audit_freelist_lock, flags);
 693         if (++audit_freelist_count > AUDIT_MAXFREE)
 694                 kfree(ab);
 695         else
 696                 list_add(&ab->list, &audit_freelist);
 697         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 698 }
 699
 700 static struct audit_buffer * audit_buffer_alloc(struct audit_context *ctx,
 701                                                 gfp_t gfp_mask, int type)
 702 {
 703         unsigned long flags;
 704         struct audit_buffer *ab = NULL;
 705         struct nlmsghdr *nlh;
 706
 707         spin_lock_irqsave(&audit_freelist_lock, flags);
 708         if (!list_empty(&audit_freelist)) {
 709                 ab = list_entry(audit_freelist.next,
 710                                 struct audit_buffer, list);
 711                 list_del(&ab->list);
 712                 --audit_freelist_count;
 713         }
 714         spin_unlock_irqrestore(&audit_freelist_lock, flags);
 715
 716         if (!ab) {
 717                 ab = kmalloc(sizeof(*ab), gfp_mask);
 718                 if (!ab)
 719                         goto err;
 720         }
 721
 722         ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
 723         if (!ab->skb)
 724                 goto err;
 725
 726         ab->ctx = ctx;
 727         ab->gfp_mask = gfp_mask;
 728         nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
 729         nlh->nlmsg_type = type;
 730         nlh->nlmsg_flags = 0;
 731         nlh->nlmsg_pid = 0;
 732         nlh->nlmsg_seq = 0;
 733         return ab;
 734 err:
 735         audit_buffer_free(ab);
 736         return NULL;
 737 }
 738
 739 /**
 740  * audit_serial - compute a serial number for the audit record
 741  *
 742  * Compute a serial number for the audit record.  Audit records are
 743  * written to user-space as soon as they are generated, so a complete
 744  * audit record may be written in several pieces.  The timestamp of the
 745  * record and this serial number are used by the user-space tools to
 746  * determine which pieces belong to the same audit record.  The
 747  * (timestamp,serial) tuple is unique for each syscall and is live from
 748  * syscall entry to syscall exit.
 749  *
 750  * NOTE: Another possibility is to store the formatted records off the
 751  * audit context (for those records that have a context), and emit them
 752  * all at syscall exit.  However, this could delay the reporting of
 753  * significant errors until syscall exit (or never, if the system
 754  * halts).
 755  */
 756 unsigned int audit_serial(void)
 757 {
 758         static spinlock_t serial_lock = SPIN_LOCK_UNLOCKED;
 759         static unsigned int serial = 0;
 760
 761         unsigned long flags;
 762         unsigned int ret;
 763
 764         spin_lock_irqsave(&serial_lock, flags);
 765         do {
 766                 ret = ++serial;
 767         } while (unlikely(!ret));
 768         spin_unlock_irqrestore(&serial_lock, flags);
 769
 770         return ret;
 771 }
 772
 773 static inline void audit_get_stamp(struct audit_context *ctx,
 774                                    struct timespec *t, unsigned int *serial)
 775 {
 776         if (ctx)
 777                 auditsc_get_stamp(ctx, t, serial);
 778         else {
 779                 *t = CURRENT_TIME;
 780                 *serial = audit_serial();
 781         }
 782 }
 783
 784 /* Obtain an audit buffer.  This routine does locking to obtain the
 785  * audit buffer, but then no locking is required for calls to
 786  * audit_log_*format.  If the tsk is a task that is currently in a
 787  * syscall, then the syscall is marked as auditable and an audit record
 788  * will be written at syscall exit.  If there is no associated task, tsk
 789  * should be NULL. */
 790
 791 /**
 792  * audit_log_start - obtain an audit buffer
 793  * @ctx: audit_context (may be NULL)
 794  * @gfp_mask: type of allocation
 795  * @type: audit message type
 796  *
 797  * Returns audit_buffer pointer on success or NULL on error.
 798  *
 799  * Obtain an audit buffer.  This routine does locking to obtain the
 800  * audit buffer, but then no locking is required for calls to
 801  * audit_log_*format.  If the task (ctx) is a task that is currently in a
 802  * syscall, then the syscall is marked as auditable and an audit record
 803  * will be written at syscall exit.  If there is no associated task, then
 804  * task context (ctx) should be NULL.
 805  */
 806 struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 807                                      int type)
 808 {
 809         struct audit_buffer     *ab     = NULL;
 810         struct timespec         t;
 811         unsigned int            serial;
 812         int reserve;
 813         unsigned long timeout_start = jiffies;
 814
 815         if (!audit_initialized)
 816                 return NULL;
 817
 818         if (unlikely(audit_filter_type(type)))
 819                 return NULL;
 820
 821         if (gfp_mask & __GFP_WAIT)
 822                 reserve = 0;
 823         else
 824                 reserve = 5; /* Allow atomic callers to go up to five
 825                                 entries over the normal backlog limit */
 826
 827         while (audit_backlog_limit
 828                && skb_queue_len(&audit_skb_queue) > audit_backlog_limit + reserve) {
 829                 if (gfp_mask & __GFP_WAIT && audit_backlog_wait_time
 830                     && time_before(jiffies, timeout_start + audit_backlog_wait_time)) {
 831
 832                         /* Wait for auditd to drain the queue a little */
 833                         DECLARE_WAITQUEUE(wait, current);
 834                         set_current_state(TASK_INTERRUPTIBLE);
 835                         add_wait_queue(&audit_backlog_wait, &wait);
 836
 837                         if (audit_backlog_limit &&
 838                             skb_queue_len(&audit_skb_queue) > audit_backlog_limit)
 839                                 schedule_timeout(timeout_start + audit_backlog_wait_time - jiffies);
 840
 841                         __set_current_state(TASK_RUNNING);
 842                         remove_wait_queue(&audit_backlog_wait, &wait);
 843                         continue;
 844                 }
 845                 if (audit_rate_check())
 846                         printk(KERN_WARNING
 847                                "audit: audit_backlog=%d > "
 848                                "audit_backlog_limit=%d\n",
 849                                skb_queue_len(&audit_skb_queue),
 850                                audit_backlog_limit);
 851                 audit_log_lost("backlog limit exceeded");
 852                 audit_backlog_wait_time = audit_backlog_wait_overflow;
 853                 wake_up(&audit_backlog_wait);
 854                 return NULL;
 855         }
 856
 857         ab = audit_buffer_alloc(ctx, gfp_mask, type);
 858         if (!ab) {
 859                 audit_log_lost("out of memory in audit_log_start");
 860                 return NULL;
 861         }
 862
 863         audit_get_stamp(ab->ctx, &t, &serial);
 864
 865         audit_log_format(ab, "audit(%lu.%03lu:%u): ",
 866                          t.tv_sec, t.tv_nsec/1000000, serial);
 867         return ab;
 868 }
 869
 870 /**
 871  * audit_expand - expand skb in the audit buffer
 872  * @ab: audit_buffer
 873  * @extra: space to add at tail of the skb
 874  *
 875  * Returns 0 (no space) on failed expansion, or available space if
 876  * successful.
 877  */
 878 static inline int audit_expand(struct audit_buffer *ab, int extra)
 879 {
 880         struct sk_buff *skb = ab->skb;
 881         int ret = pskb_expand_head(skb, skb_headroom(skb), extra,
 882                                    ab->gfp_mask);
 883         if (ret < 0) {
 884                 audit_log_lost("out of memory in audit_expand");
 885                 return 0;
 886         }
 887         return skb_tailroom(skb);
 888 }
 889
 890 /*
 891  * Format an audit message into the audit buffer.  If there isn't enough
 892  * room in the audit buffer, more room will be allocated and vsnprint
 893  * will be called a second time.  Currently, we assume that a printk
 894  * can't format message larger than 1024 bytes, so we don't either.
 895  */
 896 static void audit_log_vformat(struct audit_buffer *ab, const char *fmt,
 897                               va_list args)
 898 {
 899         int len, avail;
 900         struct sk_buff *skb;
 901         va_list args2;
 902
 903         if (!ab)
 904                 return;
 905
 906         BUG_ON(!ab->skb);
 907         skb = ab->skb;
 908         avail = skb_tailroom(skb);
 909         if (avail == 0) {
 910                 avail = audit_expand(ab, AUDIT_BUFSIZ);
 911                 if (!avail)
 912                         goto out;
 913         }
 914         va_copy(args2, args);
 915         len = vsnprintf(skb->tail, avail, fmt, args);
 916         if (len >= avail) {
 917                 /* The printk buffer is 1024 bytes long, so if we get
 918                  * here and AUDIT_BUFSIZ is at least 1024, then we can
 919                  * log everything that printk could have logged. */
 920                 avail = audit_expand(ab,
 921                         max_t(unsigned, AUDIT_BUFSIZ, 1+len-avail));
 922                 if (!avail)
 923                         goto out;
 924                 len = vsnprintf(skb->tail, avail, fmt, args2);
 925         }
 926         if (len > 0)
 927                 skb_put(skb, len);
 928 out:
 929         return;
 930 }
 931
 932 /**
 933  * audit_log_format - format a message into the audit buffer.
 934  * @ab: audit_buffer
 935  * @fmt: format string
 936  * @...: optional parameters matching @fmt string
 937  *
 938  * All the work is done in audit_log_vformat.
 939  */
 940 void audit_log_format(struct audit_buffer *ab, const char *fmt, ...)
 941 {
 942         va_list args;
 943
 944         if (!ab)
 945                 return;
 946         va_start(args, fmt);
 947         audit_log_vformat(ab, fmt, args);
 948         va_end(args);
 949 }
 950
 951 /**
 952  * audit_log_hex - convert a buffer to hex and append it to the audit skb
 953  * @ab: the audit_buffer
 954  * @buf: buffer to convert to hex
 955  * @len: length of @buf to be converted
 956  *
 957  * No return value; failure to expand is silently ignored.
 958  *
 959  * This function will take the passed buf and convert it into a string of
 960  * ascii hex digits. The new string is placed onto the skb.
 961  */
 962 void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf,
 963                 size_t len)
 964 {
 965         int i, avail, new_len;
 966         unsigned char *ptr;
 967         struct sk_buff *skb;
 968         static const unsigned char *hex = "0123456789ABCDEF";
 969
 970         BUG_ON(!ab->skb);
 971         skb = ab->skb;
 972         avail = skb_tailroom(skb);
 973         new_len = len<<1;
 974         if (new_len >= avail) {
 975                 /* Round the buffer request up to the next multiple */
 976                 new_len = AUDIT_BUFSIZ*(((new_len-avail)/AUDIT_BUFSIZ) + 1);
 977                 avail = audit_expand(ab, new_len);
 978                 if (!avail)
 979                         return;
 980         }
 981
 982         ptr = skb->tail;
 983         for (i=0; i<len; i++) {
 984                 *ptr++ = hex[(buf[i] & 0xF0)>>4]; /* Upper nibble */
 985                 *ptr++ = hex[buf[i] & 0x0F];      /* Lower nibble */
 986         }
 987         *ptr = 0;
 988         skb_put(skb, len << 1); /* new string is twice the old string */
 989 }
 990
 991 /**
 992  * audit_log_unstrustedstring - log a string that may contain random characters
 993  * @ab: audit_buffer
 994  * @string: string to be logged
 995  *
 996  * This code will escape a string that is passed to it if the string
 997  * contains a control character, unprintable character, double quote mark,
 998  * or a space. Unescaped strings will start and end with a double quote mark.
 999  * Strings that are escaped are printed in hex (2 digits per char).
1000  */
1001 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
1002 {
1003         const unsigned char *p = string;
1004
1005         while (*p) {
1006                 if (*p == '"' || *p < 0x21 || *p > 0x7f) {
1007                         audit_log_hex(ab, string, strlen(string));
1008                         return;
1009                 }
1010                 p++;
1011         }
1012         audit_log_format(ab, "\"%s\"", string);
1013 }
1014
1015 /* This is a helper-function to print the escaped d_path */
1016 void audit_log_d_path(struct audit_buffer *ab, const char *prefix,
1017                       struct dentry *dentry, struct vfsmount *vfsmnt)
1018 {
1019         char *p, *path;
1020
1021         if (prefix)
1022                 audit_log_format(ab, " %s", prefix);
1023
1024         /* We will allow 11 spaces for ' (deleted)' to be appended */
1025         path = kmalloc(PATH_MAX+11, ab->gfp_mask);
1026         if (!path) {
1027                 audit_log_format(ab, "<no memory>");
1028                 return;
1029         }
1030         p = d_path(dentry, vfsmnt, path, PATH_MAX+11);
1031         if (IS_ERR(p)) { /* Should never happen since we send PATH_MAX */
1032                 /* FIXME: can we save some information here? */
1033                 audit_log_format(ab, "<too long>");
1034         } else
1035                 audit_log_untrustedstring(ab, p);
1036         kfree(path);
1037 }
1038
1039 /**
1040  * audit_log_end - end one audit record
1041  * @ab: the audit_buffer
1042  *
1043  * The netlink_* functions cannot be called inside an irq context, so
1044  * the audit buffer is placed on a queue and a tasklet is scheduled to
1045  * remove them from the queue outside the irq context.  May be called in
1046  * any context.
1047  */
1048 void audit_log_end(struct audit_buffer *ab)
1049 {
1050         if (!ab)
1051                 return;
1052         if (!audit_rate_check()) {
1053                 audit_log_lost("rate limit exceeded");
1054         } else {
1055                 if (audit_pid) {
1056                         struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
1057                         nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0);
1058                         skb_queue_tail(&audit_skb_queue, ab->skb);
1059                         ab->skb = NULL;
1060                         wake_up_interruptible(&kauditd_wait);
1061                 } else {
1062                         printk(KERN_NOTICE "%s\n", ab->skb->data + NLMSG_SPACE(0));
1063                 }
1064         }
1065         audit_buffer_free(ab);
1066 }
1067
1068 /**
1069  * audit_log - Log an audit record
1070  * @ctx: audit context
1071  * @gfp_mask: type of allocation
1072  * @type: audit message type
1073  * @fmt: format string to use
1074  * @...: variable parameters matching the format string
1075  *
1076  * This is a convenience function that calls audit_log_start,
1077  * audit_log_vformat, and audit_log_end.  It may be called
1078  * in any context.
1079  */
1080 void audit_log(struct audit_context *ctx, gfp_t gfp_mask, int type,
1081                const char *fmt, ...)
1082 {
1083         struct audit_buffer *ab;
1084         va_list args;
1085
1086         ab = audit_log_start(ctx, gfp_mask, type);
1087         if (ab) {
1088                 va_start(args, fmt);
1089                 audit_log_vformat(ab, fmt, args);
1090                 va_end(args);
1091                 audit_log_end(ab);
1092         }
1093 }
1094
1095 EXPORT_SYMBOL(audit_log_start);
1096 EXPORT_SYMBOL(audit_log_end);
1097 EXPORT_SYMBOL(audit_log_format);
1098 EXPORT_SYMBOL(audit_log);