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