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/file.h>
  14 #include <linux/fdtable.h>
  15 #include <linux/tty.h>
  16
  17 struct tty_audit_buf {
  18         atomic_t count;
  19         struct mutex mutex;     /* Protects all data below */
  20         int major, minor;       /* The TTY which the data is from */
  21         unsigned icanon:1;
  22         size_t valid;
  23         unsigned char *data;    /* Allocated size N_TTY_BUF_SIZE */
  24 };
  25
  26 static struct tty_audit_buf *tty_audit_buf_alloc(int major, int minor,
  27                                                  int icanon)
  28 {
  29         struct tty_audit_buf *buf;
  30
  31         buf = kmalloc(sizeof(*buf), GFP_KERNEL);
  32         if (!buf)
  33                 goto err;
  34         if (PAGE_SIZE != N_TTY_BUF_SIZE)
  35                 buf->data = kmalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
  36         else
  37                 buf->data = (unsigned char *)__get_free_page(GFP_KERNEL);
  38         if (!buf->data)
  39                 goto err_buf;
  40         atomic_set(&buf->count, 1);
  41         mutex_init(&buf->mutex);
  42         buf->major = major;
  43         buf->minor = minor;
  44         buf->icanon = icanon;
  45         buf->valid = 0;
  46         return buf;
  47
  48 err_buf:
  49         kfree(buf);
  50 err:
  51         return NULL;
  52 }
  53
  54 static void tty_audit_buf_free(struct tty_audit_buf *buf)
  55 {
  56         WARN_ON(buf->valid != 0);
  57         if (PAGE_SIZE != N_TTY_BUF_SIZE)
  58                 kfree(buf->data);
  59         else
  60                 free_page((unsigned long)buf->data);
  61         kfree(buf);
  62 }
  63
  64 static void tty_audit_buf_put(struct tty_audit_buf *buf)
  65 {
  66         if (atomic_dec_and_test(&buf->count))
  67                 tty_audit_buf_free(buf);
  68 }
  69
  70 static void tty_audit_log(const char *description, struct task_struct *tsk,
  71                           uid_t loginuid, unsigned sessionid, int major,
  72                           int minor, unsigned char *data, size_t size)
  73 {
  74         struct audit_buffer *ab;
  75
  76         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  77         if (ab) {
  78                 char name[sizeof(tsk->comm)];
  79                 uid_t uid = task_uid(tsk);
  80
  81                 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u "
  82                                  "major=%d minor=%d comm=", description,
  83                                  tsk->pid, uid, loginuid, sessionid,
  84                                  major, minor);
  85                 get_task_comm(name, tsk);
  86                 audit_log_untrustedstring(ab, name);
  87                 audit_log_format(ab, " data=");
  88                 audit_log_n_hex(ab, data, size);
  89                 audit_log_end(ab);
  90         }
  91 }
  92
  93 /**
  94  *      tty_audit_buf_push      -       Push buffered data out
  95  *
  96  *      Generate an audit message from the contents of @buf, which is owned by
  97  *      @tsk with @loginuid.  @buf->mutex must be locked.
  98  */
  99 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
 100                                unsigned int sessionid,
 101                                struct tty_audit_buf *buf)
 102 {
 103         if (buf->valid == 0)
 104                 return;
 105         if (audit_enabled == 0)
 106                 return;
 107         tty_audit_log("tty", tsk, loginuid, sessionid, buf->major, buf->minor,
 108                       buf->data, buf->valid);
 109         buf->valid = 0;
 110 }
 111
 112 /**
 113  *      tty_audit_buf_push_current      -       Push buffered data out
 114  *
 115  *      Generate an audit message from the contents of @buf, which is owned by
 116  *      the current task.  @buf->mutex must be locked.
 117  */
 118 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
 119 {
 120         uid_t auid = audit_get_loginuid(current);
 121         unsigned int sessionid = audit_get_sessionid(current);
 122         tty_audit_buf_push(current, auid, sessionid, buf);
 123 }
 124
 125 /**
 126  *      tty_audit_exit  -       Handle a task exit
 127  *
 128  *      Make sure all buffered data is written out and deallocate the buffer.
 129  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 130  */
 131 void tty_audit_exit(void)
 132 {
 133         struct tty_audit_buf *buf;
 134
 135         spin_lock_irq(&current->sighand->siglock);
 136         buf = current->signal->tty_audit_buf;
 137         current->signal->tty_audit_buf = NULL;
 138         spin_unlock_irq(&current->sighand->siglock);
 139         if (!buf)
 140                 return;
 141
 142         mutex_lock(&buf->mutex);
 143         tty_audit_buf_push_current(buf);
 144         mutex_unlock(&buf->mutex);
 145
 146         tty_audit_buf_put(buf);
 147 }
 148
 149 /**
 150  *      tty_audit_fork  -       Copy TTY audit state for a new task
 151  *
 152  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 153  */
 154 void tty_audit_fork(struct signal_struct *sig)
 155 {
 156         spin_lock_irq(&current->sighand->siglock);
 157         sig->audit_tty = current->signal->audit_tty;
 158         spin_unlock_irq(&current->sighand->siglock);
 159         sig->tty_audit_buf = NULL;
 160 }
 161
 162 /**
 163  *      tty_audit_tiocsti       -       Log TIOCSTI
 164  */
 165 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 166 {
 167         struct tty_audit_buf *buf;
 168         int major, minor, should_audit;
 169
 170         spin_lock_irq(&current->sighand->siglock);
 171         should_audit = current->signal->audit_tty;
 172         buf = current->signal->tty_audit_buf;
 173         if (buf)
 174                 atomic_inc(&buf->count);
 175         spin_unlock_irq(&current->sighand->siglock);
 176
 177         major = tty->driver->major;
 178         minor = tty->driver->minor_start + tty->index;
 179         if (buf) {
 180                 mutex_lock(&buf->mutex);
 181                 if (buf->major == major && buf->minor == minor)
 182                         tty_audit_buf_push_current(buf);
 183                 mutex_unlock(&buf->mutex);
 184                 tty_audit_buf_put(buf);
 185         }
 186
 187         if (should_audit && audit_enabled) {
 188                 uid_t auid;
 189                 unsigned int sessionid;
 190
 191                 auid = audit_get_loginuid(current);
 192                 sessionid = audit_get_sessionid(current);
 193                 tty_audit_log("ioctl=TIOCSTI", current, auid, sessionid, major,
 194                               minor, &ch, 1);
 195         }
 196 }
 197
 198 /**
 199  *      tty_audit_push_task     -       Flush task's pending audit data
 200  */
 201 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
 202 {
 203         struct tty_audit_buf *buf;
 204
 205         spin_lock_irq(&tsk->sighand->siglock);
 206         buf = tsk->signal->tty_audit_buf;
 207         if (buf)
 208                 atomic_inc(&buf->count);
 209         spin_unlock_irq(&tsk->sighand->siglock);
 210         if (!buf)
 211                 return;
 212
 213         mutex_lock(&buf->mutex);
 214         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 215         mutex_unlock(&buf->mutex);
 216
 217         tty_audit_buf_put(buf);
 218 }
 219
 220 /**
 221  *      tty_audit_buf_get       -       Get an audit buffer.
 222  *
 223  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 224  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 225  *      reference to the buffer.
 226  */
 227 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
 228 {
 229         struct tty_audit_buf *buf, *buf2;
 230
 231         buf = NULL;
 232         buf2 = NULL;
 233         spin_lock_irq(&current->sighand->siglock);
 234         if (likely(!current->signal->audit_tty))
 235                 goto out;
 236         buf = current->signal->tty_audit_buf;
 237         if (buf) {
 238                 atomic_inc(&buf->count);
 239                 goto out;
 240         }
 241         spin_unlock_irq(&current->sighand->siglock);
 242
 243         buf2 = tty_audit_buf_alloc(tty->driver->major,
 244                                    tty->driver->minor_start + tty->index,
 245                                    tty->icanon);
 246         if (buf2 == NULL) {
 247                 audit_log_lost("out of memory in TTY auditing");
 248                 return NULL;
 249         }
 250
 251         spin_lock_irq(&current->sighand->siglock);
 252         if (!current->signal->audit_tty)
 253                 goto out;
 254         buf = current->signal->tty_audit_buf;
 255         if (!buf) {
 256                 current->signal->tty_audit_buf = buf2;
 257                 buf = buf2;
 258                 buf2 = NULL;
 259         }
 260         atomic_inc(&buf->count);
 261         /* Fall through */
 262  out:
 263         spin_unlock_irq(&current->sighand->siglock);
 264         if (buf2)
 265                 tty_audit_buf_free(buf2);
 266         return buf;
 267 }
 268
 269 /**
 270  *      tty_audit_add_data      -       Add data for TTY auditing.
 271  *
 272  *      Audit @data of @size from @tty, if necessary.
 273  */
 274 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 275                         size_t size)
 276 {
 277         struct tty_audit_buf *buf;
 278         int major, minor;
 279
 280         if (unlikely(size == 0))
 281                 return;
 282
 283         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 284             && tty->driver->subtype == PTY_TYPE_MASTER)
 285                 return;
 286
 287         buf = tty_audit_buf_get(tty);
 288         if (!buf)
 289                 return;
 290
 291         mutex_lock(&buf->mutex);
 292         major = tty->driver->major;
 293         minor = tty->driver->minor_start + tty->index;
 294         if (buf->major != major || buf->minor != minor
 295             || buf->icanon != tty->icanon) {
 296                 tty_audit_buf_push_current(buf);
 297                 buf->major = major;
 298                 buf->minor = minor;
 299                 buf->icanon = tty->icanon;
 300         }
 301         do {
 302                 size_t run;
 303
 304                 run = N_TTY_BUF_SIZE - buf->valid;
 305                 if (run > size)
 306                         run = size;
 307                 memcpy(buf->data + buf->valid, data, run);
 308                 buf->valid += run;
 309                 data += run;
 310                 size -= run;
 311                 if (buf->valid == N_TTY_BUF_SIZE)
 312                         tty_audit_buf_push_current(buf);
 313         } while (size != 0);
 314         mutex_unlock(&buf->mutex);
 315         tty_audit_buf_put(buf);
 316 }
 317
 318 /**
 319  *      tty_audit_push  -       Push buffered data out
 320  *
 321  *      Make sure no audit data is pending for @tty on the current process.
 322  */
 323 void tty_audit_push(struct tty_struct *tty)
 324 {
 325         struct tty_audit_buf *buf;
 326
 327         spin_lock_irq(&current->sighand->siglock);
 328         if (likely(!current->signal->audit_tty)) {
 329                 spin_unlock_irq(&current->sighand->siglock);
 330                 return;
 331         }
 332         buf = current->signal->tty_audit_buf;
 333         if (buf)
 334                 atomic_inc(&buf->count);
 335         spin_unlock_irq(&current->sighand->siglock);
 336
 337         if (buf) {
 338                 int major, minor;
 339
 340                 major = tty->driver->major;
 341                 minor = tty->driver->minor_start + tty->index;
 342                 mutex_lock(&buf->mutex);
 343                 if (buf->major == major && buf->minor == minor)
 344                         tty_audit_buf_push_current(buf);
 345                 mutex_unlock(&buf->mutex);
 346                 tty_audit_buf_put(buf);
 347         }
 348 }