drivers/tty/tty_audit.c

   1 /*
   2  * Creating audit events from TTY input.
   3  *
   4  * Copyright (C) 2007 Red Hat, Inc.  All rights reserved.  This copyrighted
   5  * material is made available to anyone wishing to use, modify, copy, or
   6  * redistribute it subject to the terms and conditions of the GNU General
   7  * Public License v.2.
   8  *
   9  * Authors: Miloslav Trmac <mitr@redhat.com>
  10  */
  11
  12 #include <linux/audit.h>
  13 #include <linux/slab.h>
  14 #include <linux/tty.h>
  15
  16 struct tty_audit_buf {
  17         atomic_t count;
  18         struct mutex mutex;     /* Protects all data below */
  19         int major, minor;       /* The TTY which the data is from */
  20         unsigned icanon:1;
  21         size_t valid;
  22         unsigned char *data;    /* Allocated size N_TTY_BUF_SIZE */
  23 };
  24
  25 static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
  26                                                  unsigned icanon)
  27 {
  28         struct tty_audit_buf *buf;
  29
  30         buf = kmalloc(sizeof(*buf), GFP_KERNEL);
  31         if (!buf)
  32                 goto err;
  33         buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
  34         if (!buf->data)
  35                 goto err_buf;
  36         atomic_set(&buf->count, 1);
  37         mutex_init(&buf->mutex);
  38         buf->major = major;
  39         buf->minor = minor;
  40         buf->icanon = icanon;
  41         buf->valid = 0;
  42         return buf;
  43
  44 err_buf:
  45         kfree(buf);
  46 err:
  47         return NULL;
  48 }
  49
  50 static void tty_audit_buf_free(struct tty_audit_buf *buf)
  51 {
  52         WARN_ON(buf->valid != 0);
  53         kfree(buf->data);
  54         kfree(buf);
  55 }
  56
  57 static void tty_audit_buf_put(struct tty_audit_buf *buf)
  58 {
  59         if (atomic_dec_and_test(&buf->count))
  60                 tty_audit_buf_free(buf);
  61 }
  62
  63 static void tty_audit_log(const char *description, struct task_struct *tsk,
  64                           kuid_t loginuid, unsigned sessionid, int major,
  65                           int minor, unsigned char *data, size_t size)
  66 {
  67         struct audit_buffer *ab;
  68
  69         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  70         if (ab) {
  71                 char name[sizeof(tsk->comm)];
  72                 kuid_t uid = task_uid(tsk);
  73
  74                 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
  75                                  "major=%d minor=%d comm=", description,
  76                                  tsk->pid,
  77                                  from_kuid(&init_user_ns, uid),
  78                                  from_kuid(&init_user_ns, loginuid),
  79                                  sessionid,
  80                                  major, minor);
  81                 get_task_comm(name, tsk);
  82                 audit_log_untrustedstring(ab, name);
  83                 audit_log_format(ab, " data=");
  84                 audit_log_n_hex(ab, data, size);
  85                 audit_log_end(ab);
  86         }
  87 }
  88
  89 /**
  90  *      tty_audit_buf_push      -       Push buffered data out
  91  *
  92  *      Generate an audit message from the contents of @buf, which is owned by
  93  *      @tsk with @loginuid.  @buf->mutex must be locked.
  94  */
  95 static void tty_audit_buf_push(struct task_struct *tsk, kuid_t loginuid,
  96                                unsigned int sessionid,
  97                                struct tty_audit_buf *buf)
  98 {
  99         if (buf->valid == 0)
 100                 return;
 101         if (audit_enabled == 0) {
 102                 buf->valid = 0;
 103                 return;
 104         }
 105         tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
 106                       buf->data, buf->valid);
 107         buf->valid = 0;
 108 }
 109
 110 /**
 111  *      tty_audit_buf_push_current      -       Push buffered data out
 112  *
 113  *      Generate an audit message from the contents of @buf, which is owned by
 114  *      the current task.  @buf->mutex must be locked.
 115  */
 116 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
 117 {
 118         kuid_t auid = audit_get_loginuid(current);
 119         unsigned int sessionid = audit_get_sessionid(current);
 120         tty_audit_buf_push(current, auid, sessionid, buf);
 121 }
 122
 123 /**
 124  *      tty_audit_exit  -       Handle a task exit
 125  *
 126  *      Make sure all buffered data is written out and deallocate the buffer.
 127  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 128  */
 129 void tty_audit_exit(void)
 130 {
 131         struct tty_audit_buf *buf;
 132
 133         spin_lock_irq(&current->sighand->siglock);
 134         buf = current->signal->tty_audit_buf;
 135         current->signal->tty_audit_buf = NULL;
 136         spin_unlock_irq(&current->sighand->siglock);
 137         if (!buf)
 138                 return;
 139
 140         mutex_lock(&buf->mutex);
 141         tty_audit_buf_push_current(buf);
 142         mutex_unlock(&buf->mutex);
 143
 144         tty_audit_buf_put(buf);
 145 }
 146
 147 /**
 148  *      tty_audit_fork  -       Copy TTY audit state for a new task
 149  *
 150  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 151  */
 152 void tty_audit_fork(struct signal_struct *sig)
 153 {
 154         spin_lock_irq(&current->sighand->siglock);
 155         sig->audit_tty = current->signal->audit_tty;
 156         spin_unlock_irq(&current->sighand->siglock);
 157 }
 158
 159 /**
 160  *      tty_audit_tiocsti       -       Log TIOCSTI
 161  */
 162 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 163 {
 164         struct tty_audit_buf *buf;
 165         int major, minor, should_audit;
 166
 167         spin_lock_irq(&current->sighand->siglock);
 168         should_audit = current->signal->audit_tty;
 169         buf = current->signal->tty_audit_buf;
 170         if (buf)
 171                 atomic_inc(&buf->count);
 172         spin_unlock_irq(&current->sighand->siglock);
 173
 174         major = tty->driver->major;
 175         minor = tty->driver->minor_start + tty->index;
 176         if (buf) {
 177                 mutex_lock(&buf->mutex);
 178                 if (buf->major == major && buf->minor == minor)
 179                         tty_audit_buf_push_current(buf);
 180                 mutex_unlock(&buf->mutex);
 181                 tty_audit_buf_put(buf);
 182         }
 183
 184         if (should_audit && audit_enabled) {
 185                 kuid_t auid;
 186                 unsigned int sessionid;
 187
 188                 auid = audit_get_loginuid(current);
 189                 sessionid = audit_get_sessionid(current);
 190                 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
 191                               minor, &ch, 1);
 192         }
 193 }
 194
 195 /**
 196  * tty_audit_push_task  -       Flush task's pending audit data
 197  * @tsk:                task pointer
 198  * @loginuid:           sender login uid
 199  * @sessionid:          sender session id
 200  *
 201  * Called with a ref on @tsk held. Try to lock sighand and get a
 202  * reference to the tty audit buffer if available.
 203  * Flush the buffer or return an appropriate error code.
 204  */
 205 int tty_audit_push_task(struct task_struct *tsk, kuid_t loginuid, u32 sessionid)
 206 {
 207         struct tty_audit_buf *buf = ERR_PTR(-EPERM);
 208         unsigned long flags;
 209
 210         if (!lock_task_sighand(tsk, &flags))
 211                 return -ESRCH;
 212
 213         if (tsk->signal->audit_tty) {
 214                 buf = tsk->signal->tty_audit_buf;
 215                 if (buf)
 216                         atomic_inc(&buf->count);
 217         }
 218         unlock_task_sighand(tsk, &flags);
 219
 220         /*
 221          * Return 0 when signal->audit_tty set
 222          * but tsk->signal->tty_audit_buf == NULL.
 223          */
 224         if (!buf || IS_ERR(buf))
 225                 return PTR_ERR(buf);
 226
 227         mutex_lock(&buf->mutex);
 228         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 229         mutex_unlock(&buf->mutex);
 230
 231         tty_audit_buf_put(buf);
 232         return 0;
 233 }
 234
 235 /**
 236  *      tty_audit_buf_get       -       Get an audit buffer.
 237  *
 238  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 239  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 240  *      reference to the buffer.
 241  */
 242 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty,
 243                 unsigned icanon)
 244 {
 245         struct tty_audit_buf *buf, *buf2;
 246
 247         buf = NULL;
 248         buf2 = NULL;
 249         spin_lock_irq(&current->sighand->siglock);
 250         if (likely(!current->signal->audit_tty))
 251                 goto out;
 252         buf = current->signal->tty_audit_buf;
 253         if (buf) {
 254                 atomic_inc(&buf->count);
 255                 goto out;
 256         }
 257         spin_unlock_irq(&current->sighand->siglock);
 258
 259         buf2 = tty_audit_buf_alloc(tty->driver->major,
 260                                    tty->driver->minor_start + tty->index,
 261                                    icanon);
 262         if (buf2 == NULL) {
 263                 audit_log_lost("out of memory in TTY auditing");
 264                 return NULL;
 265         }
 266
 267         spin_lock_irq(&current->sighand->siglock);
 268         if (!current->signal->audit_tty)
 269                 goto out;
 270         buf = current->signal->tty_audit_buf;
 271         if (!buf) {
 272                 current->signal->tty_audit_buf = buf2;
 273                 buf = buf2;
 274                 buf2 = NULL;
 275         }
 276         atomic_inc(&buf->count);
 277         /* Fall through */
 278  out:
 279         spin_unlock_irq(&current->sighand->siglock);
 280         if (buf2)
 281                 tty_audit_buf_free(buf2);
 282         return buf;
 283 }
 284
 285 /**
 286  *      tty_audit_add_data      -       Add data for TTY auditing.
 287  *
 288  *      Audit @data of @size from @tty, if necessary.
 289  */
 290 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 291                         size_t size, unsigned icanon)
 292 {
 293         struct tty_audit_buf *buf;
 294         int major, minor;
 295
 296         if (unlikely(size == 0))
 297                 return;
 298
 299         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 300             && tty->driver->subtype == PTY_TYPE_MASTER)
 301                 return;
 302
 303         buf = tty_audit_buf_get(tty, icanon);
 304         if (!buf)
 305                 return;
 306
 307         mutex_lock(&buf->mutex);
 308         major = tty->driver->major;
 309         minor = tty->driver->minor_start + tty->index;
 310         if (buf->major != major || buf->minor != minor
 311             || buf->icanon != icanon) {
 312                 tty_audit_buf_push_current(buf);
 313                 buf->major = major;
 314                 buf->minor = minor;
 315                 buf->icanon = icanon;
 316         }
 317         do {
 318                 size_t run;
 319
 320                 run = N_TTY_BUF_SIZE - buf->valid;
 321                 if (run > size)
 322                         run = size;
 323                 memcpy(buf->data + buf->valid, data, run);
 324                 buf->valid += run;
 325                 data += run;
 326                 size -= run;
 327                 if (buf->valid == N_TTY_BUF_SIZE)
 328                         tty_audit_buf_push_current(buf);
 329         } while (size != 0);
 330         mutex_unlock(&buf->mutex);
 331         tty_audit_buf_put(buf);
 332 }
 333
 334 /**
 335  *      tty_audit_push  -       Push buffered data out
 336  *
 337  *      Make sure no audit data is pending for @tty on the current process.
 338  */
 339 void tty_audit_push(struct tty_struct *tty)
 340 {
 341         struct tty_audit_buf *buf;
 342
 343         spin_lock_irq(&current->sighand->siglock);
 344         if (likely(!current->signal->audit_tty)) {
 345                 spin_unlock_irq(&current->sighand->siglock);
 346                 return;
 347         }
 348         buf = current->signal->tty_audit_buf;
 349         if (buf)
 350                 atomic_inc(&buf->count);
 351         spin_unlock_irq(&current->sighand->siglock);
 352
 353         if (buf) {
 354                 int major, minor;
 355
 356                 major = tty->driver->major;
 357                 minor = tty->driver->minor_start + tty->index;
 358                 mutex_lock(&buf->mutex);
 359                 if (buf->major == major && buf->minor == minor)
 360                         tty_audit_buf_push_current(buf);
 361                 mutex_unlock(&buf->mutex);
 362                 tty_audit_buf_put(buf);
 363         }
 364 }