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
 115         spin_lock_irq(&current->sighand->siglock);
 116         buf = current->signal->tty_audit_buf;
 117         current->signal->tty_audit_buf = NULL;
 118         spin_unlock_irq(&current->sighand->siglock);
 119         if (!buf)
 120                 return;
 121
 122         mutex_lock(&buf->mutex);
 123         tty_audit_buf_push(buf);
 124         mutex_unlock(&buf->mutex);
 125
 126         tty_audit_buf_put(buf);
 127 }
 128
 129 /**
 130  *      tty_audit_fork  -       Copy TTY audit state for a new task
 131  *
 132  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 133  */
 134 void tty_audit_fork(struct signal_struct *sig)
 135 {
 136         spin_lock_irq(&current->sighand->siglock);
 137         sig->audit_tty = current->signal->audit_tty;
 138         spin_unlock_irq(&current->sighand->siglock);
 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
 149         spin_lock_irq(&current->sighand->siglock);
 150         should_audit = current->signal->audit_tty;
 151         buf = current->signal->tty_audit_buf;
 152         if (buf)
 153                 atomic_inc(&buf->count);
 154         spin_unlock_irq(&current->sighand->siglock);
 155
 156         major = tty->driver->major;
 157         minor = tty->driver->minor_start + tty->index;
 158         if (buf) {
 159                 mutex_lock(&buf->mutex);
 160                 if (buf->major == major && buf->minor == minor)
 161                         tty_audit_buf_push(buf);
 162                 mutex_unlock(&buf->mutex);
 163                 tty_audit_buf_put(buf);
 164         }
 165
 166         if (should_audit && audit_enabled) {
 167                 kuid_t auid;
 168                 unsigned int sessionid;
 169
 170                 auid = audit_get_loginuid(current);
 171                 sessionid = audit_get_sessionid(current);
 172                 tty_audit_log("ioctl=TIOCSTI", major, minor, &ch, 1);
 173         }
 174 }
 175
 176 /**
 177  * tty_audit_push_current -     Flush current's pending audit data
 178  *
 179  * Try to lock sighand and get a reference to the tty audit buffer if available.
 180  * Flush the buffer or return an appropriate error code.
 181  */
 182 int tty_audit_push_current(void)
 183 {
 184         struct tty_audit_buf *buf = ERR_PTR(-EPERM);
 185         struct task_struct *tsk = current;
 186         unsigned long flags;
 187
 188         if (!lock_task_sighand(tsk, &flags))
 189                 return -ESRCH;
 190
 191         if (tsk->signal->audit_tty) {
 192                 buf = tsk->signal->tty_audit_buf;
 193                 if (buf)
 194                         atomic_inc(&buf->count);
 195         }
 196         unlock_task_sighand(tsk, &flags);
 197
 198         /*
 199          * Return 0 when signal->audit_tty set
 200          * but tsk->signal->tty_audit_buf == NULL.
 201          */
 202         if (!buf || IS_ERR(buf))
 203                 return PTR_ERR(buf);
 204
 205         mutex_lock(&buf->mutex);
 206         tty_audit_buf_push(buf);
 207         mutex_unlock(&buf->mutex);
 208
 209         tty_audit_buf_put(buf);
 210         return 0;
 211 }
 212
 213 /**
 214  *      tty_audit_buf_get       -       Get an audit buffer.
 215  *
 216  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 217  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 218  *      reference to the buffer.
 219  */
 220 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty,
 221                 unsigned icanon)
 222 {
 223         struct tty_audit_buf *buf, *buf2;
 224
 225         buf = NULL;
 226         buf2 = NULL;
 227         spin_lock_irq(&current->sighand->siglock);
 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_irq(&current->sighand->siglock);
 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_irq(&current->sighand->siglock);
 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_irq(&current->sighand->siglock);
 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
 274         if (unlikely(size == 0))
 275                 return;
 276
 277         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 278             && tty->driver->subtype == PTY_TYPE_MASTER)
 279                 return;
 280
 281         buf = tty_audit_buf_get(tty, icanon);
 282         if (!buf)
 283                 return;
 284
 285         mutex_lock(&buf->mutex);
 286         major = tty->driver->major;
 287         minor = tty->driver->minor_start + tty->index;
 288         if (buf->major != major || buf->minor != minor
 289             || buf->icanon != icanon) {
 290                 tty_audit_buf_push(buf);
 291                 buf->major = major;
 292                 buf->minor = minor;
 293                 buf->icanon = icanon;
 294         }
 295         do {
 296                 size_t run;
 297
 298                 run = N_TTY_BUF_SIZE - buf->valid;
 299                 if (run > size)
 300                         run = size;
 301                 memcpy(buf->data + buf->valid, data, run);
 302                 buf->valid += run;
 303                 data += run;
 304                 size -= run;
 305                 if (buf->valid == N_TTY_BUF_SIZE)
 306                         tty_audit_buf_push(buf);
 307         } while (size != 0);
 308         mutex_unlock(&buf->mutex);
 309         tty_audit_buf_put(buf);
 310 }
 311
 312 /**
 313  *      tty_audit_push  -       Push buffered data out
 314  *
 315  *      Make sure no audit data is pending for @tty on the current process.
 316  */
 317 void tty_audit_push(struct tty_struct *tty)
 318 {
 319         struct tty_audit_buf *buf;
 320
 321         spin_lock_irq(&current->sighand->siglock);
 322         if (likely(!current->signal->audit_tty)) {
 323                 spin_unlock_irq(&current->sighand->siglock);
 324                 return;
 325         }
 326         buf = current->signal->tty_audit_buf;
 327         if (buf)
 328                 atomic_inc(&buf->count);
 329         spin_unlock_irq(&current->sighand->siglock);
 330
 331         if (buf) {
 332                 int major, minor;
 333
 334                 major = tty->driver->major;
 335                 minor = tty->driver->minor_start + tty->index;
 336                 mutex_lock(&buf->mutex);
 337                 if (buf->major == major && buf->minor == minor)
 338                         tty_audit_buf_push(buf);
 339                 mutex_unlock(&buf->mutex);
 340                 tty_audit_buf_put(buf);
 341         }
 342 }