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         buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
  33         if (!buf->data)
  34                 goto err_buf;
  35         atomic_set(&buf->count, 1);
  36         mutex_init(&buf->mutex);
  37         buf->major = major;
  38         buf->minor = minor;
  39         buf->icanon = icanon;
  40         buf->valid = 0;
  41         return buf;
  42
  43 err_buf:
  44         kfree(buf);
  45 err:
  46         return NULL;
  47 }
  48
  49 static void tty_audit_buf_free(struct tty_audit_buf *buf)
  50 {
  51         WARN_ON(buf->valid != 0);
  52         kfree(buf->data);
  53         kfree(buf);
  54 }
  55
  56 static void tty_audit_buf_put(struct tty_audit_buf *buf)
  57 {
  58         if (atomic_dec_and_test(&buf->count))
  59                 tty_audit_buf_free(buf);
  60 }
  61
  62 static void tty_audit_log(const char *description, struct task_struct *tsk,
  63                           uid_t loginuid, unsigned sessionid, int major,
  64                           int minor, unsigned char *data, size_t size)
  65 {
  66         struct audit_buffer *ab;
  67
  68         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  69         if (ab) {
  70                 char name[sizeof(tsk->comm)];
  71                 uid_t uid = task_uid(tsk);
  72
  73                 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
  74                                  "major=%d minor=%d comm=", description,
  75                                  tsk->pid, uid, loginuid, sessionid,
  76                                  major, minor);
  77                 get_task_comm(name, tsk);
  78                 audit_log_untrustedstring(ab, name);
  79                 audit_log_format(ab, " data=");
  80                 audit_log_n_hex(ab, data, size);
  81                 audit_log_end(ab);
  82         }
  83 }
  84
  85 /**
  86  *      tty_audit_buf_push      -       Push buffered data out
  87  *
  88  *      Generate an audit message from the contents of @buf, which is owned by
  89  *      @tsk with @loginuid.  @buf->mutex must be locked.
  90  */
  91 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
  92                                unsigned int sessionid,
  93                                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", tsk, loginuid, sessionid, buf->major, buf->minor,
 102                       buf->data, buf->valid);
 103         buf->valid = 0;
 104 }
 105
 106 /**
 107  *      tty_audit_buf_push_current      -       Push buffered data out
 108  *
 109  *      Generate an audit message from the contents of @buf, which is owned by
 110  *      the current task.  @buf->mutex must be locked.
 111  */
 112 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
 113 {
 114         uid_t auid = audit_get_loginuid(current);
 115         unsigned int sessionid = audit_get_sessionid(current);
 116         tty_audit_buf_push(current, auid, sessionid, buf);
 117 }
 118
 119 /**
 120  *      tty_audit_exit  -       Handle a task exit
 121  *
 122  *      Make sure all buffered data is written out and deallocate the buffer.
 123  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 124  */
 125 void tty_audit_exit(void)
 126 {
 127         struct tty_audit_buf *buf;
 128
 129         spin_lock_irq(&current->sighand->siglock);
 130         buf = current->signal->tty_audit_buf;
 131         current->signal->tty_audit_buf = NULL;
 132         spin_unlock_irq(&current->sighand->siglock);
 133         if (!buf)
 134                 return;
 135
 136         mutex_lock(&buf->mutex);
 137         tty_audit_buf_push_current(buf);
 138         mutex_unlock(&buf->mutex);
 139
 140         tty_audit_buf_put(buf);
 141 }
 142
 143 /**
 144  *      tty_audit_fork  -       Copy TTY audit state for a new task
 145  *
 146  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 147  */
 148 void tty_audit_fork(struct signal_struct *sig)
 149 {
 150         spin_lock_irq(&current->sighand->siglock);
 151         sig->audit_tty = current->signal->audit_tty;
 152         spin_unlock_irq(&current->sighand->siglock);
 153         sig->tty_audit_buf = NULL;
 154 }
 155
 156 /**
 157  *      tty_audit_tiocsti       -       Log TIOCSTI
 158  */
 159 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 160 {
 161         struct tty_audit_buf *buf;
 162         int major, minor, should_audit;
 163
 164         spin_lock_irq(&current->sighand->siglock);
 165         should_audit = current->signal->audit_tty;
 166         buf = current->signal->tty_audit_buf;
 167         if (buf)
 168                 atomic_inc(&buf->count);
 169         spin_unlock_irq(&current->sighand->siglock);
 170
 171         major = tty->driver->major;
 172         minor = tty->driver->minor_start + tty->index;
 173         if (buf) {
 174                 mutex_lock(&buf->mutex);
 175                 if (buf->major == major && buf->minor == minor)
 176                         tty_audit_buf_push_current(buf);
 177                 mutex_unlock(&buf->mutex);
 178                 tty_audit_buf_put(buf);
 179         }
 180
 181         if (should_audit && audit_enabled) {
 182                 uid_t auid;
 183                 unsigned int sessionid;
 184
 185                 auid = audit_get_loginuid(current);
 186                 sessionid = audit_get_sessionid(current);
 187                 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
 188                               minor, &ch, 1);
 189         }
 190 }
 191
 192 /**
 193  *      tty_audit_push_task     -       Flush task's pending audit data
 194  */
 195 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
 196 {
 197         struct tty_audit_buf *buf;
 198
 199         spin_lock_irq(&tsk->sighand->siglock);
 200         buf = tsk->signal->tty_audit_buf;
 201         if (buf)
 202                 atomic_inc(&buf->count);
 203         spin_unlock_irq(&tsk->sighand->siglock);
 204         if (!buf)
 205                 return;
 206
 207         mutex_lock(&buf->mutex);
 208         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 209         mutex_unlock(&buf->mutex);
 210
 211         tty_audit_buf_put(buf);
 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 {
 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                                    tty->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)
 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);
 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 != tty->icanon) {
 290                 tty_audit_buf_push_current(buf);
 291                 buf->major = major;
 292                 buf->minor = minor;
 293                 buf->icanon = tty->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_current(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_current(buf);
 339                 mutex_unlock(&buf->mutex);
 340                 tty_audit_buf_put(buf);
 341         }
 342 }