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                 buf->valid = 0;
 100                 return;
 101         }
 102         tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
 103                       buf->data, buf->valid);
 104         buf->valid = 0;
 105 }
 106
 107 /**
 108  *      tty_audit_buf_push_current      -       Push buffered data out
 109  *
 110  *      Generate an audit message from the contents of @buf, which is owned by
 111  *      the current task.  @buf->mutex must be locked.
 112  */
 113 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
 114 {
 115         uid_t auid = audit_get_loginuid(current);
 116         unsigned int sessionid = audit_get_sessionid(current);
 117         tty_audit_buf_push(current, auid, sessionid, buf);
 118 }
 119
 120 /**
 121  *      tty_audit_exit  -       Handle a task exit
 122  *
 123  *      Make sure all buffered data is written out and deallocate the buffer.
 124  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 125  */
 126 void tty_audit_exit(void)
 127 {
 128         struct tty_audit_buf *buf;
 129
 130         spin_lock_irq(&current->sighand->siglock);
 131         buf = current->signal->tty_audit_buf;
 132         current->signal->tty_audit_buf = NULL;
 133         spin_unlock_irq(&current->sighand->siglock);
 134         if (!buf)
 135                 return;
 136
 137         mutex_lock(&buf->mutex);
 138         tty_audit_buf_push_current(buf);
 139         mutex_unlock(&buf->mutex);
 140
 141         tty_audit_buf_put(buf);
 142 }
 143
 144 /**
 145  *      tty_audit_fork  -       Copy TTY audit state for a new task
 146  *
 147  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 148  */
 149 void tty_audit_fork(struct signal_struct *sig)
 150 {
 151         spin_lock_irq(&current->sighand->siglock);
 152         sig->audit_tty = current->signal->audit_tty;
 153         spin_unlock_irq(&current->sighand->siglock);
 154 }
 155
 156 /**
 157  *      tty_audit_tiocsti       -       Log TIOCSTI
 158  */
 159 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 160 {
 161         struct tty_audit_buf *buf;
 162         int major, minor, should_audit;
 163
 164         spin_lock_irq(&current->sighand->siglock);
 165         should_audit = current->signal->audit_tty;
 166         buf = current->signal->tty_audit_buf;
 167         if (buf)
 168                 atomic_inc(&buf->count);
 169         spin_unlock_irq(&current->sighand->siglock);
 170
 171         major = tty->driver->major;
 172         minor = tty->driver->minor_start + tty->index;
 173         if (buf) {
 174                 mutex_lock(&buf->mutex);
 175                 if (buf->major == major && buf->minor == minor)
 176                         tty_audit_buf_push_current(buf);
 177                 mutex_unlock(&buf->mutex);
 178                 tty_audit_buf_put(buf);
 179         }
 180
 181         if (should_audit && audit_enabled) {
 182                 uid_t auid;
 183                 unsigned int sessionid;
 184
 185                 auid = audit_get_loginuid(current);
 186                 sessionid = audit_get_sessionid(current);
 187                 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
 188                               minor, &ch, 1);
 189         }
 190 }
 191
 192 /**
 193  * tty_audit_push_task  -       Flush task's pending audit data
 194  * @tsk:                task pointer
 195  * @loginuid:           sender login uid
 196  * @sessionid:          sender session id
 197  *
 198  * Called with a ref on @tsk held. Try to lock sighand and get a
 199  * reference to the tty audit buffer if available.
 200  * Flush the buffer or return an appropriate error code.
 201  */
 202 int tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
 203 {
 204         struct tty_audit_buf *buf = ERR_PTR(-EPERM);
 205         unsigned long flags;
 206
 207         if (!lock_task_sighand(tsk, &flags))
 208                 return -ESRCH;
 209
 210         if (tsk->signal->audit_tty) {
 211                 buf = tsk->signal->tty_audit_buf;
 212                 if (buf)
 213                         atomic_inc(&buf->count);
 214         }
 215         unlock_task_sighand(tsk, &flags);
 216
 217         /*
 218          * Return 0 when signal->audit_tty set
 219          * but tsk->signal->tty_audit_buf == NULL.
 220          */
 221         if (!buf || IS_ERR(buf))
 222                 return PTR_ERR(buf);
 223
 224         mutex_lock(&buf->mutex);
 225         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 226         mutex_unlock(&buf->mutex);
 227
 228         tty_audit_buf_put(buf);
 229         return 0;
 230 }
 231
 232 /**
 233  *      tty_audit_buf_get       -       Get an audit buffer.
 234  *
 235  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 236  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 237  *      reference to the buffer.
 238  */
 239 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
 240 {
 241         struct tty_audit_buf *buf, *buf2;
 242
 243         buf = NULL;
 244         buf2 = NULL;
 245         spin_lock_irq(&current->sighand->siglock);
 246         if (likely(!current->signal->audit_tty))
 247                 goto out;
 248         buf = current->signal->tty_audit_buf;
 249         if (buf) {
 250                 atomic_inc(&buf->count);
 251                 goto out;
 252         }
 253         spin_unlock_irq(&current->sighand->siglock);
 254
 255         buf2 = tty_audit_buf_alloc(tty->driver->major,
 256                                    tty->driver->minor_start + tty->index,
 257                                    tty->icanon);
 258         if (buf2 == NULL) {
 259                 audit_log_lost("out of memory in TTY auditing");
 260                 return NULL;
 261         }
 262
 263         spin_lock_irq(&current->sighand->siglock);
 264         if (!current->signal->audit_tty)
 265                 goto out;
 266         buf = current->signal->tty_audit_buf;
 267         if (!buf) {
 268                 current->signal->tty_audit_buf = buf2;
 269                 buf = buf2;
 270                 buf2 = NULL;
 271         }
 272         atomic_inc(&buf->count);
 273         /* Fall through */
 274  out:
 275         spin_unlock_irq(&current->sighand->siglock);
 276         if (buf2)
 277                 tty_audit_buf_free(buf2);
 278         return buf;
 279 }
 280
 281 /**
 282  *      tty_audit_add_data      -       Add data for TTY auditing.
 283  *
 284  *      Audit @data of @size from @tty, if necessary.
 285  */
 286 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 287                         size_t size)
 288 {
 289         struct tty_audit_buf *buf;
 290         int major, minor;
 291
 292         if (unlikely(size == 0))
 293                 return;
 294
 295         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 296             && tty->driver->subtype == PTY_TYPE_MASTER)
 297                 return;
 298
 299         buf = tty_audit_buf_get(tty);
 300         if (!buf)
 301                 return;
 302
 303         mutex_lock(&buf->mutex);
 304         major = tty->driver->major;
 305         minor = tty->driver->minor_start + tty->index;
 306         if (buf->major != major || buf->minor != minor
 307             || buf->icanon != tty->icanon) {
 308                 tty_audit_buf_push_current(buf);
 309                 buf->major = major;
 310                 buf->minor = minor;
 311                 buf->icanon = tty->icanon;
 312         }
 313         do {
 314                 size_t run;
 315
 316                 run = N_TTY_BUF_SIZE - buf->valid;
 317                 if (run > size)
 318                         run = size;
 319                 memcpy(buf->data + buf->valid, data, run);
 320                 buf->valid += run;
 321                 data += run;
 322                 size -= run;
 323                 if (buf->valid == N_TTY_BUF_SIZE)
 324                         tty_audit_buf_push_current(buf);
 325         } while (size != 0);
 326         mutex_unlock(&buf->mutex);
 327         tty_audit_buf_put(buf);
 328 }
 329
 330 /**
 331  *      tty_audit_push  -       Push buffered data out
 332  *
 333  *      Make sure no audit data is pending for @tty on the current process.
 334  */
 335 void tty_audit_push(struct tty_struct *tty)
 336 {
 337         struct tty_audit_buf *buf;
 338
 339         spin_lock_irq(&current->sighand->siglock);
 340         if (likely(!current->signal->audit_tty)) {
 341                 spin_unlock_irq(&current->sighand->siglock);
 342                 return;
 343         }
 344         buf = current->signal->tty_audit_buf;
 345         if (buf)
 346                 atomic_inc(&buf->count);
 347         spin_unlock_irq(&current->sighand->siglock);
 348
 349         if (buf) {
 350                 int major, minor;
 351
 352                 major = tty->driver->major;
 353                 minor = tty->driver->minor_start + tty->index;
 354                 mutex_lock(&buf->mutex);
 355                 if (buf->major == major && buf->minor == minor)
 356                         tty_audit_buf_push_current(buf);
 357                 mutex_unlock(&buf->mutex);
 358                 tty_audit_buf_put(buf);
 359         }
 360 }