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         if (PAGE_SIZE != N_TTY_BUF_SIZE)
  33                 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
  34         else
  35                 buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
  36         if (!buf->data)
  37                 goto err_buf;
  38         atomic_set(&buf->count, 1);
  39         mutex_init(&buf->mutex);
  40         buf->major = major;
  41         buf->minor = minor;
  42         buf->icanon = icanon;
  43         buf->valid = 0;
  44         return buf;
  45
  46 err_buf:
  47         kfree(buf);
  48 err:
  49         return NULL;
  50 }
  51
  52 static void tty_audit_buf_free(struct tty_audit_buf *buf)
  53 {
  54         WARN_ON(buf->valid != 0);
  55         if (PAGE_SIZE != N_TTY_BUF_SIZE)
  56                 kfree(buf->data);
  57         else
  58                 free_page((unsigned long)buf->data);
  59         kfree(buf);
  60 }
  61
  62 static void tty_audit_buf_put(struct tty_audit_buf *buf)
  63 {
  64         if (atomic_dec_and_test(&buf->count))
  65                 tty_audit_buf_free(buf);
  66 }
  67
  68 static void tty_audit_log(const char *description, struct task_struct *tsk,
  69                           uid_t loginuid, unsigned sessionid, int major,
  70                           int minor, unsigned char *data, size_t size)
  71 {
  72         struct audit_buffer *ab;
  73
  74         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  75         if (ab) {
  76                 char name[sizeof(tsk->comm)];
  77                 uid_t uid = task_uid(tsk);
  78
  79                 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
  80                                  "major=%d minor=%d comm=", description,
  81                                  tsk->pid, uid, loginuid, sessionid,
  82                                  major, minor);
  83                 get_task_comm(name, tsk);
  84                 audit_log_untrustedstring(ab, name);
  85                 audit_log_format(ab, " data=");
  86                 audit_log_n_hex(ab, data, size);
  87                 audit_log_end(ab);
  88         }
  89 }
  90
  91 /**
  92  *      tty_audit_buf_push      -       Push buffered data out
  93  *
  94  *      Generate an audit message from the contents of @buf, which is owned by
  95  *      @tsk with @loginuid.  @buf->mutex must be locked.
  96  */
  97 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
  98                                unsigned int sessionid,
  99                                struct tty_audit_buf *buf)
 100 {
 101         if (buf->valid == 0)
 102                 return;
 103         if (audit_enabled == 0)
 104                 return;
 105         tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
 106                       buf->data, buf->valid);
 107         buf->valid = 0;
 108 }
 109
 110 /**
 111  *      tty_audit_buf_push_current      -       Push buffered data out
 112  *
 113  *      Generate an audit message from the contents of @buf, which is owned by
 114  *      the current task.  @buf->mutex must be locked.
 115  */
 116 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
 117 {
 118         uid_t auid = audit_get_loginuid(current);
 119         unsigned int sessionid = audit_get_sessionid(current);
 120         tty_audit_buf_push(current, auid, sessionid, buf);
 121 }
 122
 123 /**
 124  *      tty_audit_exit  -       Handle a task exit
 125  *
 126  *      Make sure all buffered data is written out and deallocate the buffer.
 127  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 128  */
 129 void tty_audit_exit(void)
 130 {
 131         struct tty_audit_buf *buf;
 132
 133         spin_lock_irq(&current->sighand->siglock);
 134         buf = current->signal->tty_audit_buf;
 135         current->signal->tty_audit_buf = NULL;
 136         spin_unlock_irq(&current->sighand->siglock);
 137         if (!buf)
 138                 return;
 139
 140         mutex_lock(&buf->mutex);
 141         tty_audit_buf_push_current(buf);
 142         mutex_unlock(&buf->mutex);
 143
 144         tty_audit_buf_put(buf);
 145 }
 146
 147 /**
 148  *      tty_audit_fork  -       Copy TTY audit state for a new task
 149  *
 150  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 151  */
 152 void tty_audit_fork(struct signal_struct *sig)
 153 {
 154         spin_lock_irq(&current->sighand->siglock);
 155         sig->audit_tty = current->signal->audit_tty;
 156         spin_unlock_irq(&current->sighand->siglock);
 157         sig->tty_audit_buf = NULL;
 158 }
 159
 160 /**
 161  *      tty_audit_tiocsti       -       Log TIOCSTI
 162  */
 163 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 164 {
 165         struct tty_audit_buf *buf;
 166         int major, minor, should_audit;
 167
 168         spin_lock_irq(&current->sighand->siglock);
 169         should_audit = current->signal->audit_tty;
 170         buf = current->signal->tty_audit_buf;
 171         if (buf)
 172                 atomic_inc(&buf->count);
 173         spin_unlock_irq(&current->sighand->siglock);
 174
 175         major = tty->driver->major;
 176         minor = tty->driver->minor_start + tty->index;
 177         if (buf) {
 178                 mutex_lock(&buf->mutex);
 179                 if (buf->major == major && buf->minor == minor)
 180                         tty_audit_buf_push_current(buf);
 181                 mutex_unlock(&buf->mutex);
 182                 tty_audit_buf_put(buf);
 183         }
 184
 185         if (should_audit && audit_enabled) {
 186                 uid_t auid;
 187                 unsigned int sessionid;
 188
 189                 auid = audit_get_loginuid(current);
 190                 sessionid = audit_get_sessionid(current);
 191                 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
 192                               minor, &ch, 1);
 193         }
 194 }
 195
 196 /**
 197  *      tty_audit_push_task     -       Flush task's pending audit data
 198  */
 199 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
 200 {
 201         struct tty_audit_buf *buf;
 202
 203         spin_lock_irq(&tsk->sighand->siglock);
 204         buf = tsk->signal->tty_audit_buf;
 205         if (buf)
 206                 atomic_inc(&buf->count);
 207         spin_unlock_irq(&tsk->sighand->siglock);
 208         if (!buf)
 209                 return;
 210
 211         mutex_lock(&buf->mutex);
 212         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 213         mutex_unlock(&buf->mutex);
 214
 215         tty_audit_buf_put(buf);
 216 }
 217
 218 /**
 219  *      tty_audit_buf_get       -       Get an audit buffer.
 220  *
 221  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 222  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 223  *      reference to the buffer.
 224  */
 225 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
 226 {
 227         struct tty_audit_buf *buf, *buf2;
 228
 229         buf = NULL;
 230         buf2 = NULL;
 231         spin_lock_irq(&current->sighand->siglock);
 232         if (likely(!current->signal->audit_tty))
 233                 goto out;
 234         buf = current->signal->tty_audit_buf;
 235         if (buf) {
 236                 atomic_inc(&buf->count);
 237                 goto out;
 238         }
 239         spin_unlock_irq(&current->sighand->siglock);
 240
 241         buf2 = tty_audit_buf_alloc(tty->driver->major,
 242                                    tty->driver->minor_start + tty->index,
 243                                    tty->icanon);
 244         if (buf2 == NULL) {
 245                 audit_log_lost("out of memory in TTY auditing");
 246                 return NULL;
 247         }
 248
 249         spin_lock_irq(&current->sighand->siglock);
 250         if (!current->signal->audit_tty)
 251                 goto out;
 252         buf = current->signal->tty_audit_buf;
 253         if (!buf) {
 254                 current->signal->tty_audit_buf = buf2;
 255                 buf = buf2;
 256                 buf2 = NULL;
 257         }
 258         atomic_inc(&buf->count);
 259         /* Fall through */
 260  out:
 261         spin_unlock_irq(&current->sighand->siglock);
 262         if (buf2)
 263                 tty_audit_buf_free(buf2);
 264         return buf;
 265 }
 266
 267 /**
 268  *      tty_audit_add_data      -       Add data for TTY auditing.
 269  *
 270  *      Audit @data of @size from @tty, if necessary.
 271  */
 272 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 273                         size_t size)
 274 {
 275         struct tty_audit_buf *buf;
 276         int major, minor;
 277
 278         if (unlikely(size == 0))
 279                 return;
 280
 281         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 282             && tty->driver->subtype == PTY_TYPE_MASTER)
 283                 return;
 284
 285         buf = tty_audit_buf_get(tty);
 286         if (!buf)
 287                 return;
 288
 289         mutex_lock(&buf->mutex);
 290         major = tty->driver->major;
 291         minor = tty->driver->minor_start + tty->index;
 292         if (buf->major != major || buf->minor != minor
 293             || buf->icanon != tty->icanon) {
 294                 tty_audit_buf_push_current(buf);
 295                 buf->major = major;
 296                 buf->minor = minor;
 297                 buf->icanon = tty->icanon;
 298         }
 299         do {
 300                 size_t run;
 301
 302                 run = N_TTY_BUF_SIZE - buf->valid;
 303                 if (run > size)
 304                         run = size;
 305                 memcpy(buf->data + buf->valid, data, run);
 306                 buf->valid += run;
 307                 data += run;
 308                 size -= run;
 309                 if (buf->valid == N_TTY_BUF_SIZE)
 310                         tty_audit_buf_push_current(buf);
 311         } while (size != 0);
 312         mutex_unlock(&buf->mutex);
 313         tty_audit_buf_put(buf);
 314 }
 315
 316 /**
 317  *      tty_audit_push  -       Push buffered data out
 318  *
 319  *      Make sure no audit data is pending for @tty on the current process.
 320  */
 321 void tty_audit_push(struct tty_struct *tty)
 322 {
 323         struct tty_audit_buf *buf;
 324
 325         spin_lock_irq(&current->sighand->siglock);
 326         if (likely(!current->signal->audit_tty)) {
 327                 spin_unlock_irq(&current->sighand->siglock);
 328                 return;
 329         }
 330         buf = current->signal->tty_audit_buf;
 331         if (buf)
 332                 atomic_inc(&buf->count);
 333         spin_unlock_irq(&current->sighand->siglock);
 334
 335         if (buf) {
 336                 int major, minor;
 337
 338                 major = tty->driver->major;
 339                 minor = tty->driver->minor_start + tty->index;
 340                 mutex_lock(&buf->mutex);
 341                 if (buf->major == major && buf->minor == minor)
 342                         tty_audit_buf_push_current(buf);
 343                 mutex_unlock(&buf->mutex);
 344                 tty_audit_buf_put(buf);
 345         }
 346 }