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                                                  int 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                           uid_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                 uid_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, uid, loginuid, sessionid,
  77                                  major, minor);
  78                 get_task_comm(name, tsk);
  79                 audit_log_untrustedstring(ab, name);
  80                 audit_log_format(ab, " data=");
  81                 audit_log_n_hex(ab, data, size);
  82                 audit_log_end(ab);
  83         }
  84 }
  85
  86 /**
  87  *      tty_audit_buf_push      -       Push buffered data out
  88  *
  89  *      Generate an audit message from the contents of @buf, which is owned by
  90  *      @tsk with @loginuid.  @buf->mutex must be locked.
  91  */
  92 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
  93                                unsigned int sessionid,
  94                                struct tty_audit_buf *buf)
  95 {
  96         if (buf->valid == 0)
  97                 return;
  98         if (audit_enabled == 0)
  99                 return;
 100         tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
 101                       buf->data, buf->valid);
 102         buf->valid = 0;
 103 }
 104
 105 /**
 106  *      tty_audit_buf_push_current      -       Push buffered data out
 107  *
 108  *      Generate an audit message from the contents of @buf, which is owned by
 109  *      the current task.  @buf->mutex must be locked.
 110  */
 111 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
 112 {
 113         uid_t auid = audit_get_loginuid(current);
 114         unsigned int sessionid = audit_get_sessionid(current);
 115         tty_audit_buf_push(current, auid, sessionid, buf);
 116 }
 117
 118 /**
 119  *      tty_audit_exit  -       Handle a task exit
 120  *
 121  *      Make sure all buffered data is written out and deallocate the buffer.
 122  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 123  */
 124 void tty_audit_exit(void)
 125 {
 126         struct tty_audit_buf *buf;
 127
 128         spin_lock_irq(&current->sighand->siglock);
 129         buf = current->signal->tty_audit_buf;
 130         current->signal->tty_audit_buf = NULL;
 131         spin_unlock_irq(&current->sighand->siglock);
 132         if (!buf)
 133                 return;
 134
 135         mutex_lock(&buf->mutex);
 136         tty_audit_buf_push_current(buf);
 137         mutex_unlock(&buf->mutex);
 138
 139         tty_audit_buf_put(buf);
 140 }
 141
 142 /**
 143  *      tty_audit_fork  -       Copy TTY audit state for a new task
 144  *
 145  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 146  */
 147 void tty_audit_fork(struct signal_struct *sig)
 148 {
 149         spin_lock_irq(&current->sighand->siglock);
 150         sig->audit_tty = current->signal->audit_tty;
 151         spin_unlock_irq(&current->sighand->siglock);
 152 }
 153
 154 /**
 155  *      tty_audit_tiocsti       -       Log TIOCSTI
 156  */
 157 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 158 {
 159         struct tty_audit_buf *buf;
 160         int major, minor, should_audit;
 161
 162         spin_lock_irq(&current->sighand->siglock);
 163         should_audit = current->signal->audit_tty;
 164         buf = current->signal->tty_audit_buf;
 165         if (buf)
 166                 atomic_inc(&buf->count);
 167         spin_unlock_irq(&current->sighand->siglock);
 168
 169         major = tty->driver->major;
 170         minor = tty->driver->minor_start + tty->index;
 171         if (buf) {
 172                 mutex_lock(&buf->mutex);
 173                 if (buf->major == major && buf->minor == minor)
 174                         tty_audit_buf_push_current(buf);
 175                 mutex_unlock(&buf->mutex);
 176                 tty_audit_buf_put(buf);
 177         }
 178
 179         if (should_audit && audit_enabled) {
 180                 uid_t auid;
 181                 unsigned int sessionid;
 182
 183                 auid = audit_get_loginuid(current);
 184                 sessionid = audit_get_sessionid(current);
 185                 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
 186                               minor, &ch, 1);
 187         }
 188 }
 189
 190 /**
 191  * tty_audit_push_task  -       Flush task's pending audit data
 192  * @tsk:                task pointer
 193  * @loginuid:           sender login uid
 194  * @sessionid:          sender session id
 195  *
 196  * Called with a ref on @tsk held. Try to lock sighand and get a
 197  * reference to the tty audit buffer if available.
 198  * Flush the buffer or return an appropriate error code.
 199  */
 200 int tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
 201 {
 202         struct tty_audit_buf *buf = ERR_PTR(-EPERM);
 203         unsigned long flags;
 204
 205         if (!lock_task_sighand(tsk, &flags))
 206                 return -ESRCH;
 207
 208         if (tsk->signal->audit_tty) {
 209                 buf = tsk->signal->tty_audit_buf;
 210                 if (buf)
 211                         atomic_inc(&buf->count);
 212         }
 213         unlock_task_sighand(tsk, &flags);
 214
 215         /*
 216          * Return 0 when signal->audit_tty set
 217          * but tsk->signal->tty_audit_buf == NULL.
 218          */
 219         if (!buf || IS_ERR(buf))
 220                 return PTR_ERR(buf);
 221
 222         mutex_lock(&buf->mutex);
 223         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 224         mutex_unlock(&buf->mutex);
 225
 226         tty_audit_buf_put(buf);
 227         return 0;
 228 }
 229
 230 /**
 231  *      tty_audit_buf_get       -       Get an audit buffer.
 232  *
 233  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 234  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 235  *      reference to the buffer.
 236  */
 237 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
 238 {
 239         struct tty_audit_buf *buf, *buf2;
 240
 241         buf = NULL;
 242         buf2 = NULL;
 243         spin_lock_irq(&current->sighand->siglock);
 244         if (likely(!current->signal->audit_tty))
 245                 goto out;
 246         buf = current->signal->tty_audit_buf;
 247         if (buf) {
 248                 atomic_inc(&buf->count);
 249                 goto out;
 250         }
 251         spin_unlock_irq(&current->sighand->siglock);
 252
 253         buf2 = tty_audit_buf_alloc(tty->driver->major,
 254                                    tty->driver->minor_start + tty->index,
 255                                    tty->icanon);
 256         if (buf2 == NULL) {
 257                 audit_log_lost("out of memory in TTY auditing");
 258                 return NULL;
 259         }
 260
 261         spin_lock_irq(&current->sighand->siglock);
 262         if (!current->signal->audit_tty)
 263                 goto out;
 264         buf = current->signal->tty_audit_buf;
 265         if (!buf) {
 266                 current->signal->tty_audit_buf = buf2;
 267                 buf = buf2;
 268                 buf2 = NULL;
 269         }
 270         atomic_inc(&buf->count);
 271         /* Fall through */
 272  out:
 273         spin_unlock_irq(&current->sighand->siglock);
 274         if (buf2)
 275                 tty_audit_buf_free(buf2);
 276         return buf;
 277 }
 278
 279 /**
 280  *      tty_audit_add_data      -       Add data for TTY auditing.
 281  *
 282  *      Audit @data of @size from @tty, if necessary.
 283  */
 284 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 285                         size_t size)
 286 {
 287         struct tty_audit_buf *buf;
 288         int major, minor;
 289
 290         if (unlikely(size == 0))
 291                 return;
 292
 293         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 294             && tty->driver->subtype == PTY_TYPE_MASTER)
 295                 return;
 296
 297         buf = tty_audit_buf_get(tty);
 298         if (!buf)
 299                 return;
 300
 301         mutex_lock(&buf->mutex);
 302         major = tty->driver->major;
 303         minor = tty->driver->minor_start + tty->index;
 304         if (buf->major != major || buf->minor != minor
 305             || buf->icanon != tty->icanon) {
 306                 tty_audit_buf_push_current(buf);
 307                 buf->major = major;
 308                 buf->minor = minor;
 309                 buf->icanon = tty->icanon;
 310         }
 311         do {
 312                 size_t run;
 313
 314                 run = N_TTY_BUF_SIZE - buf->valid;
 315                 if (run > size)
 316                         run = size;
 317                 memcpy(buf->data + buf->valid, data, run);
 318                 buf->valid += run;
 319                 data += run;
 320                 size -= run;
 321                 if (buf->valid == N_TTY_BUF_SIZE)
 322                         tty_audit_buf_push_current(buf);
 323         } while (size != 0);
 324         mutex_unlock(&buf->mutex);
 325         tty_audit_buf_put(buf);
 326 }
 327
 328 /**
 329  *      tty_audit_push  -       Push buffered data out
 330  *
 331  *      Make sure no audit data is pending for @tty on the current process.
 332  */
 333 void tty_audit_push(struct tty_struct *tty)
 334 {
 335         struct tty_audit_buf *buf;
 336
 337         spin_lock_irq(&current->sighand->siglock);
 338         if (likely(!current->signal->audit_tty)) {
 339                 spin_unlock_irq(&current->sighand->siglock);
 340                 return;
 341         }
 342         buf = current->signal->tty_audit_buf;
 343         if (buf)
 344                 atomic_inc(&buf->count);
 345         spin_unlock_irq(&current->sighand->siglock);
 346
 347         if (buf) {
 348                 int major, minor;
 349
 350                 major = tty->driver->major;
 351                 minor = tty->driver->minor_start + tty->index;
 352                 mutex_lock(&buf->mutex);
 353                 if (buf->major == major && buf->minor == minor)
 354                         tty_audit_buf_push_current(buf);
 355                 mutex_unlock(&buf->mutex);
 356                 tty_audit_buf_put(buf);
 357         }
 358 }