Pileus Git - ~andy/linux/blob - 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, int major, int minor,
  64                           unsigned char *data, size_t size)
  65 {
  66         struct audit_buffer *ab;
  67         struct task_struct *tsk = current;
  68         uid_t uid = from_kuid(&init_user_ns, task_uid(tsk));
  69         uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(tsk));
  70         u32 sessionid = audit_get_sessionid(tsk);
  71
  72         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  73         if (ab) {
  74                 char name[sizeof(tsk->comm)];
  75
  76                 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
  77                                  " minor=%d comm=", description, tsk->pid, uid,
  78                                  loginuid, sessionid, major, minor);
  79                 get_task_comm(name, tsk);
  80                 audit_log_untrustedstring(ab, name);
  81                 audit_log_format(ab, " data=");
  82                 audit_log_n_hex(ab, data, size);
  83                 audit_log_end(ab);
  84         }
  85 }
  86
  87 /**
  88  *      tty_audit_buf_push      -       Push buffered data out
  89  *
  90  *      Generate an audit message from the contents of @buf, which is owned by
  91  *      the current task.  @buf->mutex must be locked.
  92  */
  93 static void tty_audit_buf_push(struct tty_audit_buf *buf)
  94 {
  95         if (buf->valid == 0)
  96                 return;
  97         if (audit_enabled == 0) {
  98                 buf->valid = 0;
  99                 return;
 100         }
 101         tty_audit_log("tty", buf->major, buf->minor, buf->data, buf->valid);
 102         buf->valid = 0;
 103 }
 104
 105 /**
 106  *      tty_audit_exit  -       Handle a task exit
 107  *
 108  *      Make sure all buffered data is written out and deallocate the buffer.
 109  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 110  */
 111 void tty_audit_exit(void)
 112 {
 113         struct tty_audit_buf *buf;
 114         unsigned long flags;
 115
 116         spin_lock_irqsave(&current->sighand->siglock, flags);
 117         buf = current->signal->tty_audit_buf;
 118         current->signal->tty_audit_buf = NULL;
 119         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 120         if (!buf)
 121                 return;
 122
 123         mutex_lock(&buf->mutex);
 124         tty_audit_buf_push(buf);
 125         mutex_unlock(&buf->mutex);
 126
 127         tty_audit_buf_put(buf);
 128 }
 129
 130 /**
 131  *      tty_audit_fork  -       Copy TTY audit state for a new task
 132  *
 133  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 134  */
 135 void tty_audit_fork(struct signal_struct *sig)
 136 {
 137         sig->audit_tty = current->signal->audit_tty;
 138         sig->audit_tty_log_passwd = current->signal->audit_tty_log_passwd;
 139 }
 140
 141 /**
 142  *      tty_audit_tiocsti       -       Log TIOCSTI
 143  */
 144 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 145 {
 146         struct tty_audit_buf *buf;
 147         int major, minor, should_audit;
 148         unsigned long flags;
 149
 150         spin_lock_irqsave(&current->sighand->siglock, flags);
 151         should_audit = current->signal->audit_tty;
 152         buf = current->signal->tty_audit_buf;
 153         if (buf)
 154                 atomic_inc(&buf->count);
 155         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 156
 157         major = tty->driver->major;
 158         minor = tty->driver->minor_start + tty->index;
 159         if (buf) {
 160                 mutex_lock(&buf->mutex);
 161                 if (buf->major == major && buf->minor == minor)
 162                         tty_audit_buf_push(buf);
 163                 mutex_unlock(&buf->mutex);
 164                 tty_audit_buf_put(buf);
 165         }
 166
 167         if (should_audit && audit_enabled) {
 168                 kuid_t auid;
 169                 unsigned int sessionid;
 170
 171                 auid = audit_get_loginuid(current);
 172                 sessionid = audit_get_sessionid(current);
 173                 tty_audit_log("ioctl=TIOCSTI", major, minor, &ch, 1);
 174         }
 175 }
 176
 177 /**
 178  * tty_audit_push_current -     Flush current's pending audit data
 179  *
 180  * Try to lock sighand and get a reference to the tty audit buffer if available.
 181  * Flush the buffer or return an appropriate error code.
 182  */
 183 int tty_audit_push_current(void)
 184 {
 185         struct tty_audit_buf *buf = ERR_PTR(-EPERM);
 186         struct task_struct *tsk = current;
 187         unsigned long flags;
 188
 189         if (!lock_task_sighand(tsk, &flags))
 190                 return -ESRCH;
 191
 192         if (tsk->signal->audit_tty) {
 193                 buf = tsk->signal->tty_audit_buf;
 194                 if (buf)
 195                         atomic_inc(&buf->count);
 196         }
 197         unlock_task_sighand(tsk, &flags);
 198
 199         /*
 200          * Return 0 when signal->audit_tty set
 201          * but tsk->signal->tty_audit_buf == NULL.
 202          */
 203         if (!buf || IS_ERR(buf))
 204                 return PTR_ERR(buf);
 205
 206         mutex_lock(&buf->mutex);
 207         tty_audit_buf_push(buf);
 208         mutex_unlock(&buf->mutex);
 209
 210         tty_audit_buf_put(buf);
 211         return 0;
 212 }
 213
 214 /**
 215  *      tty_audit_buf_get       -       Get an audit buffer.
 216  *
 217  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 218  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 219  *      reference to the buffer.
 220  */
 221 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty,
 222                 unsigned icanon)
 223 {
 224         struct tty_audit_buf *buf, *buf2;
 225         unsigned long flags;
 226
 227         buf = NULL;
 228         buf2 = NULL;
 229         spin_lock_irqsave(&current->sighand->siglock, flags);
 230         if (likely(!current->signal->audit_tty))
 231                 goto out;
 232         buf = current->signal->tty_audit_buf;
 233         if (buf) {
 234                 atomic_inc(&buf->count);
 235                 goto out;
 236         }
 237         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 238
 239         buf2 = tty_audit_buf_alloc(tty->driver->major,
 240                                    tty->driver->minor_start + tty->index,
 241                                    icanon);
 242         if (buf2 == NULL) {
 243                 audit_log_lost("out of memory in TTY auditing");
 244                 return NULL;
 245         }
 246
 247         spin_lock_irqsave(&current->sighand->siglock, flags);
 248         if (!current->signal->audit_tty)
 249                 goto out;
 250         buf = current->signal->tty_audit_buf;
 251         if (!buf) {
 252                 current->signal->tty_audit_buf = buf2;
 253                 buf = buf2;
 254                 buf2 = NULL;
 255         }
 256         atomic_inc(&buf->count);
 257         /* Fall through */
 258  out:
 259         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 260         if (buf2)
 261                 tty_audit_buf_free(buf2);
 262         return buf;
 263 }
 264
 265 /**
 266  *      tty_audit_add_data      -       Add data for TTY auditing.
 267  *
 268  *      Audit @data of @size from @tty, if necessary.
 269  */
 270 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 271                         size_t size, unsigned icanon)
 272 {
 273         struct tty_audit_buf *buf;
 274         int major, minor;
 275         int audit_log_tty_passwd;
 276         unsigned long flags;
 277
 278         if (unlikely(size == 0))
 279                 return;
 280
 281         spin_lock_irqsave(&current->sighand->siglock, flags);
 282         audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
 283         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 284         if (!audit_log_tty_passwd && icanon && !L_ECHO(tty))
 285                 return;
 286
 287         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 288             && tty->driver->subtype == PTY_TYPE_MASTER)
 289                 return;
 290
 291         buf = tty_audit_buf_get(tty, icanon);
 292         if (!buf)
 293                 return;
 294
 295         mutex_lock(&buf->mutex);
 296         major = tty->driver->major;
 297         minor = tty->driver->minor_start + tty->index;
 298         if (buf->major != major || buf->minor != minor
 299             || buf->icanon != icanon) {
 300                 tty_audit_buf_push(buf);
 301                 buf->major = major;
 302                 buf->minor = minor;
 303                 buf->icanon = icanon;
 304         }
 305         do {
 306                 size_t run;
 307
 308                 run = N_TTY_BUF_SIZE - buf->valid;
 309                 if (run > size)
 310                         run = size;
 311                 memcpy(buf->data + buf->valid, data, run);
 312                 buf->valid += run;
 313                 data += run;
 314                 size -= run;
 315                 if (buf->valid == N_TTY_BUF_SIZE)
 316                         tty_audit_buf_push(buf);
 317         } while (size != 0);
 318         mutex_unlock(&buf->mutex);
 319         tty_audit_buf_put(buf);
 320 }
 321
 322 /**
 323  *      tty_audit_push  -       Push buffered data out
 324  *
 325  *      Make sure no audit data is pending for @tty on the current process.
 326  */
 327 void tty_audit_push(struct tty_struct *tty)
 328 {
 329         struct tty_audit_buf *buf;
 330         unsigned long flags;
 331
 332         spin_lock_irqsave(&current->sighand->siglock, flags);
 333         if (likely(!current->signal->audit_tty)) {
 334                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
 335                 return;
 336         }
 337         buf = current->signal->tty_audit_buf;
 338         if (buf)
 339                 atomic_inc(&buf->count);
 340         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 341
 342         if (buf) {
 343                 int major, minor;
 344
 345                 major = tty->driver->major;
 346                 minor = tty->driver->minor_start + tty->index;
 347                 mutex_lock(&buf->mutex);
 348                 if (buf->major == major && buf->minor == minor)
 349                         tty_audit_buf_push(buf);
 350                 mutex_unlock(&buf->mutex);
 351                 tty_audit_buf_put(buf);
 352         }
 353 }