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         unsigned long flags;
 115
 116         spin_lock_irqsave(&current->sighand->siglock, flags);
 117         buf = current->signal->tty_audit_buf;
 118         current->signal->tty_audit_buf = NULL;
 119         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 120         if (!buf)
 121                 return;
 122
 123         mutex_lock(&buf->mutex);
 124         tty_audit_buf_push(buf);
 125         mutex_unlock(&buf->mutex);
 126
 127         tty_audit_buf_put(buf);
 128 }
 129
 130 /**
 131  *      tty_audit_fork  -       Copy TTY audit state for a new task
 132  *
 133  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 134  */
 135 void tty_audit_fork(struct signal_struct *sig)
 136 {
 137         unsigned long flags;
 138
 139         spin_lock_irqsave(&current->sighand->siglock, flags);
 140         sig->audit_tty = current->signal->audit_tty;
 141         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 142 }
 143
 144 /**
 145  *      tty_audit_tiocsti       -       Log TIOCSTI
 146  */
 147 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 148 {
 149         struct tty_audit_buf *buf;
 150         int major, minor, should_audit;
 151         unsigned long flags;
 152
 153         spin_lock_irqsave(&current->sighand->siglock, flags);
 154         should_audit = current->signal->audit_tty;
 155         buf = current->signal->tty_audit_buf;
 156         if (buf)
 157                 atomic_inc(&buf->count);
 158         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 159
 160         major = tty->driver->major;
 161         minor = tty->driver->minor_start + tty->index;
 162         if (buf) {
 163                 mutex_lock(&buf->mutex);
 164                 if (buf->major == major && buf->minor == minor)
 165                         tty_audit_buf_push(buf);
 166                 mutex_unlock(&buf->mutex);
 167                 tty_audit_buf_put(buf);
 168         }
 169
 170         if (should_audit && audit_enabled) {
 171                 kuid_t auid;
 172                 unsigned int sessionid;
 173
 174                 auid = audit_get_loginuid(current);
 175                 sessionid = audit_get_sessionid(current);
 176                 tty_audit_log("ioctl=TIOCSTI", major, minor, &ch, 1);
 177         }
 178 }
 179
 180 /**
 181  * tty_audit_push_current -     Flush current's pending audit data
 182  *
 183  * Try to lock sighand and get a reference to the tty audit buffer if available.
 184  * Flush the buffer or return an appropriate error code.
 185  */
 186 int tty_audit_push_current(void)
 187 {
 188         struct tty_audit_buf *buf = ERR_PTR(-EPERM);
 189         struct task_struct *tsk = current;
 190         unsigned long flags;
 191
 192         if (!lock_task_sighand(tsk, &flags))
 193                 return -ESRCH;
 194
 195         if (tsk->signal->audit_tty) {
 196                 buf = tsk->signal->tty_audit_buf;
 197                 if (buf)
 198                         atomic_inc(&buf->count);
 199         }
 200         unlock_task_sighand(tsk, &flags);
 201
 202         /*
 203          * Return 0 when signal->audit_tty set
 204          * but tsk->signal->tty_audit_buf == NULL.
 205          */
 206         if (!buf || IS_ERR(buf))
 207                 return PTR_ERR(buf);
 208
 209         mutex_lock(&buf->mutex);
 210         tty_audit_buf_push(buf);
 211         mutex_unlock(&buf->mutex);
 212
 213         tty_audit_buf_put(buf);
 214         return 0;
 215 }
 216
 217 /**
 218  *      tty_audit_buf_get       -       Get an audit buffer.
 219  *
 220  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 221  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 222  *      reference to the buffer.
 223  */
 224 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty,
 225                 unsigned icanon)
 226 {
 227         struct tty_audit_buf *buf, *buf2;
 228         unsigned long flags;
 229
 230         buf = NULL;
 231         buf2 = NULL;
 232         spin_lock_irqsave(&current->sighand->siglock, flags);
 233         if (likely(!current->signal->audit_tty))
 234                 goto out;
 235         buf = current->signal->tty_audit_buf;
 236         if (buf) {
 237                 atomic_inc(&buf->count);
 238                 goto out;
 239         }
 240         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 241
 242         buf2 = tty_audit_buf_alloc(tty->driver->major,
 243                                    tty->driver->minor_start + tty->index,
 244                                    icanon);
 245         if (buf2 == NULL) {
 246                 audit_log_lost("out of memory in TTY auditing");
 247                 return NULL;
 248         }
 249
 250         spin_lock_irqsave(&current->sighand->siglock, flags);
 251         if (!current->signal->audit_tty)
 252                 goto out;
 253         buf = current->signal->tty_audit_buf;
 254         if (!buf) {
 255                 current->signal->tty_audit_buf = buf2;
 256                 buf = buf2;
 257                 buf2 = NULL;
 258         }
 259         atomic_inc(&buf->count);
 260         /* Fall through */
 261  out:
 262         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 263         if (buf2)
 264                 tty_audit_buf_free(buf2);
 265         return buf;
 266 }
 267
 268 /**
 269  *      tty_audit_add_data      -       Add data for TTY auditing.
 270  *
 271  *      Audit @data of @size from @tty, if necessary.
 272  */
 273 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 274                         size_t size, unsigned icanon)
 275 {
 276         struct tty_audit_buf *buf;
 277         int major, minor;
 278
 279         if (unlikely(size == 0))
 280                 return;
 281
 282         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 283             && tty->driver->subtype == PTY_TYPE_MASTER)
 284                 return;
 285
 286         buf = tty_audit_buf_get(tty, icanon);
 287         if (!buf)
 288                 return;
 289
 290         mutex_lock(&buf->mutex);
 291         major = tty->driver->major;
 292         minor = tty->driver->minor_start + tty->index;
 293         if (buf->major != major || buf->minor != minor
 294             || buf->icanon != icanon) {
 295                 tty_audit_buf_push(buf);
 296                 buf->major = major;
 297                 buf->minor = minor;
 298                 buf->icanon = icanon;
 299         }
 300         do {
 301                 size_t run;
 302
 303                 run = N_TTY_BUF_SIZE - buf->valid;
 304                 if (run > size)
 305                         run = size;
 306                 memcpy(buf->data + buf->valid, data, run);
 307                 buf->valid += run;
 308                 data += run;
 309                 size -= run;
 310                 if (buf->valid == N_TTY_BUF_SIZE)
 311                         tty_audit_buf_push(buf);
 312         } while (size != 0);
 313         mutex_unlock(&buf->mutex);
 314         tty_audit_buf_put(buf);
 315 }
 316
 317 /**
 318  *      tty_audit_push  -       Push buffered data out
 319  *
 320  *      Make sure no audit data is pending for @tty on the current process.
 321  */
 322 void tty_audit_push(struct tty_struct *tty)
 323 {
 324         struct tty_audit_buf *buf;
 325         unsigned long flags;
 326
 327         spin_lock_irqsave(&current->sighand->siglock, flags);
 328         if (likely(!current->signal->audit_tty)) {
 329                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
 330                 return;
 331         }
 332         buf = current->signal->tty_audit_buf;
 333         if (buf)
 334                 atomic_inc(&buf->count);
 335         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 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(buf);
 345                 mutex_unlock(&buf->mutex);
 346                 tty_audit_buf_put(buf);
 347         }
 348 }