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(void)
  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 = 0;
  38         buf->minor = 0;
  39         buf->icanon = 0;
  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, int major, int minor,
  63                           unsigned char *data, size_t size)
  64 {
  65         struct audit_buffer *ab;
  66         struct task_struct *tsk = current;
  67         pid_t pid = task_pid_nr(tsk);
  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         unsigned int 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, 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         buf = current->signal->tty_audit_buf;
 116         current->signal->tty_audit_buf = NULL;
 117         if (!buf)
 118                 return;
 119
 120         mutex_lock(&buf->mutex);
 121         tty_audit_buf_push(buf);
 122         mutex_unlock(&buf->mutex);
 123
 124         tty_audit_buf_put(buf);
 125 }
 126
 127 /**
 128  *      tty_audit_fork  -       Copy TTY audit state for a new task
 129  *
 130  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 131  */
 132 void tty_audit_fork(struct signal_struct *sig)
 133 {
 134         sig->audit_tty = current->signal->audit_tty;
 135         sig->audit_tty_log_passwd = current->signal->audit_tty_log_passwd;
 136 }
 137
 138 /**
 139  *      tty_audit_tiocsti       -       Log TIOCSTI
 140  */
 141 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 142 {
 143         struct tty_audit_buf *buf;
 144         int major, minor, should_audit;
 145         unsigned long flags;
 146
 147         spin_lock_irqsave(&current->sighand->siglock, flags);
 148         should_audit = current->signal->audit_tty;
 149         buf = current->signal->tty_audit_buf;
 150         if (buf)
 151                 atomic_inc(&buf->count);
 152         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 153
 154         major = tty->driver->major;
 155         minor = tty->driver->minor_start + tty->index;
 156         if (buf) {
 157                 mutex_lock(&buf->mutex);
 158                 if (buf->major == major && buf->minor == minor)
 159                         tty_audit_buf_push(buf);
 160                 mutex_unlock(&buf->mutex);
 161                 tty_audit_buf_put(buf);
 162         }
 163
 164         if (should_audit && audit_enabled) {
 165                 kuid_t auid;
 166                 unsigned int sessionid;
 167
 168                 auid = audit_get_loginuid(current);
 169                 sessionid = audit_get_sessionid(current);
 170                 tty_audit_log("ioctl=TIOCSTI", major, minor, &ch, 1);
 171         }
 172 }
 173
 174 /**
 175  * tty_audit_push_current -     Flush current's pending audit data
 176  *
 177  * Try to lock sighand and get a reference to the tty audit buffer if available.
 178  * Flush the buffer or return an appropriate error code.
 179  */
 180 int tty_audit_push_current(void)
 181 {
 182         struct tty_audit_buf *buf = ERR_PTR(-EPERM);
 183         struct task_struct *tsk = current;
 184         unsigned long flags;
 185
 186         if (!lock_task_sighand(tsk, &flags))
 187                 return -ESRCH;
 188
 189         if (tsk->signal->audit_tty) {
 190                 buf = tsk->signal->tty_audit_buf;
 191                 if (buf)
 192                         atomic_inc(&buf->count);
 193         }
 194         unlock_task_sighand(tsk, &flags);
 195
 196         /*
 197          * Return 0 when signal->audit_tty set
 198          * but tsk->signal->tty_audit_buf == NULL.
 199          */
 200         if (!buf || IS_ERR(buf))
 201                 return PTR_ERR(buf);
 202
 203         mutex_lock(&buf->mutex);
 204         tty_audit_buf_push(buf);
 205         mutex_unlock(&buf->mutex);
 206
 207         tty_audit_buf_put(buf);
 208         return 0;
 209 }
 210
 211 /**
 212  *      tty_audit_buf_get       -       Get an audit buffer.
 213  *
 214  *      Get an audit buffer, allocate it if necessary.  Return %NULL
 215  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 216  *      reference to the buffer.
 217  */
 218 static struct tty_audit_buf *tty_audit_buf_get(void)
 219 {
 220         struct tty_audit_buf *buf, *buf2;
 221         unsigned long flags;
 222
 223         buf = NULL;
 224         buf2 = NULL;
 225         spin_lock_irqsave(&current->sighand->siglock, flags);
 226         if (likely(!current->signal->audit_tty))
 227                 goto out;
 228         buf = current->signal->tty_audit_buf;
 229         if (buf) {
 230                 atomic_inc(&buf->count);
 231                 goto out;
 232         }
 233         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 234
 235         buf2 = tty_audit_buf_alloc();
 236         if (buf2 == NULL) {
 237                 audit_log_lost("out of memory in TTY auditing");
 238                 return NULL;
 239         }
 240
 241         spin_lock_irqsave(&current->sighand->siglock, flags);
 242         if (!current->signal->audit_tty)
 243                 goto out;
 244         buf = current->signal->tty_audit_buf;
 245         if (!buf) {
 246                 current->signal->tty_audit_buf = buf2;
 247                 buf = buf2;
 248                 buf2 = NULL;
 249         }
 250         atomic_inc(&buf->count);
 251         /* Fall through */
 252  out:
 253         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 254         if (buf2)
 255                 tty_audit_buf_free(buf2);
 256         return buf;
 257 }
 258
 259 /**
 260  *      tty_audit_add_data      -       Add data for TTY auditing.
 261  *
 262  *      Audit @data of @size from @tty, if necessary.
 263  */
 264 void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
 265 {
 266         struct tty_audit_buf *buf;
 267         int major, minor;
 268         int audit_log_tty_passwd;
 269         unsigned long flags;
 270         unsigned int icanon = !!L_ICANON(tty);
 271
 272         if (unlikely(size == 0))
 273                 return;
 274
 275         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 276             && tty->driver->subtype == PTY_TYPE_MASTER)
 277                 return;
 278
 279         spin_lock_irqsave(&current->sighand->siglock, flags);
 280         audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
 281         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 282         if (!audit_log_tty_passwd && icanon && !L_ECHO(tty))
 283                 return;
 284
 285         buf = tty_audit_buf_get();
 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 != icanon) {
 294                 tty_audit_buf_push(buf);
 295                 buf->major = major;
 296                 buf->minor = minor;
 297                 buf->icanon = 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(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         unsigned long flags;
 325
 326         spin_lock_irqsave(&current->sighand->siglock, flags);
 327         if (likely(!current->signal->audit_tty)) {
 328                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
 329                 return;
 330         }
 331         buf = current->signal->tty_audit_buf;
 332         if (buf)
 333                 atomic_inc(&buf->count);
 334         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 335
 336         if (buf) {
 337                 int major, minor;
 338
 339                 major = tty->driver->major;
 340                 minor = tty->driver->minor_start + tty->index;
 341                 mutex_lock(&buf->mutex);
 342                 if (buf->major == major && buf->minor == minor)
 343                         tty_audit_buf_push(buf);
 344                 mutex_unlock(&buf->mutex);
 345                 tty_audit_buf_put(buf);
 346         }
 347 }