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