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/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  */
 193 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
 194 {
 195         struct tty_audit_buf *buf;
 196
 197         spin_lock_irq(&tsk->sighand->siglock);
 198         buf = tsk->signal->tty_audit_buf;
 199         if (buf)
 200                 atomic_inc(&buf->count);
 201         spin_unlock_irq(&tsk->sighand->siglock);
 202         if (!buf)
 203                 return;
 204
 205         mutex_lock(&buf->mutex);
 206         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 207         mutex_unlock(&buf->mutex);
 208
 209         tty_audit_buf_put(buf);
 210 }
 211
 212 /**
 213  *      tty_audit_buf_get       -       Get an audit buffer.
 214  *
 215  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 216  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 217  *      reference to the buffer.
 218  */
 219 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
 220 {
 221         struct tty_audit_buf *buf, *buf2;
 222
 223         buf = NULL;
 224         buf2 = NULL;
 225         spin_lock_irq(&current->sighand->siglock);
 226         if (likely(!current->signal->audit_tty))
 227                 goto out;
 228         buf = current->signal->tty_audit_buf;
 229         if (buf) {
 230                 atomic_inc(&buf->count);
 231                 goto out;
 232         }
 233         spin_unlock_irq(&current->sighand->siglock);
 234
 235         buf2 = tty_audit_buf_alloc(tty->driver->major,
 236                                    tty->driver->minor_start + tty->index,
 237                                    tty->icanon);
 238         if (buf2 == NULL) {
 239                 audit_log_lost("out of memory in TTY auditing");
 240                 return NULL;
 241         }
 242
 243         spin_lock_irq(&current->sighand->siglock);
 244         if (!current->signal->audit_tty)
 245                 goto out;
 246         buf = current->signal->tty_audit_buf;
 247         if (!buf) {
 248                 current->signal->tty_audit_buf = buf2;
 249                 buf = buf2;
 250                 buf2 = NULL;
 251         }
 252         atomic_inc(&buf->count);
 253         /* Fall through */
 254  out:
 255         spin_unlock_irq(&current->sighand->siglock);
 256         if (buf2)
 257                 tty_audit_buf_free(buf2);
 258         return buf;
 259 }
 260
 261 /**
 262  *      tty_audit_add_data      -       Add data for TTY auditing.
 263  *
 264  *      Audit @data of @size from @tty, if necessary.
 265  */
 266 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 267                         size_t size)
 268 {
 269         struct tty_audit_buf *buf;
 270         int major, minor;
 271
 272         if (unlikely(size == 0))
 273                 return;
 274
 275         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 276             && tty->driver->subtype == PTY_TYPE_MASTER)
 277                 return;
 278
 279         buf = tty_audit_buf_get(tty);
 280         if (!buf)
 281                 return;
 282
 283         mutex_lock(&buf->mutex);
 284         major = tty->driver->major;
 285         minor = tty->driver->minor_start + tty->index;
 286         if (buf->major != major || buf->minor != minor
 287             || buf->icanon != tty->icanon) {
 288                 tty_audit_buf_push_current(buf);
 289                 buf->major = major;
 290                 buf->minor = minor;
 291                 buf->icanon = tty->icanon;
 292         }
 293         do {
 294                 size_t run;
 295
 296                 run = N_TTY_BUF_SIZE - buf->valid;
 297                 if (run > size)
 298                         run = size;
 299                 memcpy(buf->data + buf->valid, data, run);
 300                 buf->valid += run;
 301                 data += run;
 302                 size -= run;
 303                 if (buf->valid == N_TTY_BUF_SIZE)
 304                         tty_audit_buf_push_current(buf);
 305         } while (size != 0);
 306         mutex_unlock(&buf->mutex);
 307         tty_audit_buf_put(buf);
 308 }
 309
 310 /**
 311  *      tty_audit_push  -       Push buffered data out
 312  *
 313  *      Make sure no audit data is pending for @tty on the current process.
 314  */
 315 void tty_audit_push(struct tty_struct *tty)
 316 {
 317         struct tty_audit_buf *buf;
 318
 319         spin_lock_irq(&current->sighand->siglock);
 320         if (likely(!current->signal->audit_tty)) {
 321                 spin_unlock_irq(&current->sighand->siglock);
 322                 return;
 323         }
 324         buf = current->signal->tty_audit_buf;
 325         if (buf)
 326                 atomic_inc(&buf->count);
 327         spin_unlock_irq(&current->sighand->siglock);
 328
 329         if (buf) {
 330                 int major, minor;
 331
 332                 major = tty->driver->major;
 333                 minor = tty->driver->minor_start + tty->index;
 334                 mutex_lock(&buf->mutex);
 335                 if (buf->major == major && buf->minor == minor)
 336                         tty_audit_buf_push_current(buf);
 337                 mutex_unlock(&buf->mutex);
 338                 tty_audit_buf_put(buf);
 339         }
 340 }