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         unsigned long flags;
 184
 185         spin_lock_irqsave(&current->sighand->siglock, flags);
 186         if (current->signal->audit_tty) {
 187                 buf = current->signal->tty_audit_buf;
 188                 if (buf)
 189                         atomic_inc(&buf->count);
 190         }
 191         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 192
 193         /*
 194          * Return 0 when signal->audit_tty set
 195          * but current->signal->tty_audit_buf == NULL.
 196          */
 197         if (!buf || IS_ERR(buf))
 198                 return PTR_ERR(buf);
 199
 200         mutex_lock(&buf->mutex);
 201         tty_audit_buf_push(buf);
 202         mutex_unlock(&buf->mutex);
 203
 204         tty_audit_buf_put(buf);
 205         return 0;
 206 }
 207
 208 /**
 209  *      tty_audit_buf_get       -       Get an audit buffer.
 210  *
 211  *      Get an audit buffer, allocate it if necessary.  Return %NULL
 212  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 213  *      reference to the buffer.
 214  */
 215 static struct tty_audit_buf *tty_audit_buf_get(void)
 216 {
 217         struct tty_audit_buf *buf, *buf2;
 218         unsigned long flags;
 219
 220         buf = NULL;
 221         buf2 = NULL;
 222         spin_lock_irqsave(&current->sighand->siglock, flags);
 223         if (likely(!current->signal->audit_tty))
 224                 goto out;
 225         buf = current->signal->tty_audit_buf;
 226         if (buf) {
 227                 atomic_inc(&buf->count);
 228                 goto out;
 229         }
 230         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 231
 232         buf2 = tty_audit_buf_alloc();
 233         if (buf2 == NULL) {
 234                 audit_log_lost("out of memory in TTY auditing");
 235                 return NULL;
 236         }
 237
 238         spin_lock_irqsave(&current->sighand->siglock, flags);
 239         if (!current->signal->audit_tty)
 240                 goto out;
 241         buf = current->signal->tty_audit_buf;
 242         if (!buf) {
 243                 current->signal->tty_audit_buf = buf2;
 244                 buf = buf2;
 245                 buf2 = NULL;
 246         }
 247         atomic_inc(&buf->count);
 248         /* Fall through */
 249  out:
 250         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 251         if (buf2)
 252                 tty_audit_buf_free(buf2);
 253         return buf;
 254 }
 255
 256 /**
 257  *      tty_audit_add_data      -       Add data for TTY auditing.
 258  *
 259  *      Audit @data of @size from @tty, if necessary.
 260  */
 261 void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
 262 {
 263         struct tty_audit_buf *buf;
 264         int major, minor;
 265         int audit_log_tty_passwd;
 266         unsigned long flags;
 267         unsigned int icanon = !!L_ICANON(tty);
 268
 269         if (unlikely(size == 0))
 270                 return;
 271
 272         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 273             && tty->driver->subtype == PTY_TYPE_MASTER)
 274                 return;
 275
 276         spin_lock_irqsave(&current->sighand->siglock, flags);
 277         audit_log_tty_passwd = current->signal->audit_tty_log_passwd;
 278         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 279         if (!audit_log_tty_passwd && icanon && !L_ECHO(tty))
 280                 return;
 281
 282         buf = tty_audit_buf_get();
 283         if (!buf)
 284                 return;
 285
 286         mutex_lock(&buf->mutex);
 287         major = tty->driver->major;
 288         minor = tty->driver->minor_start + tty->index;
 289         if (buf->major != major || buf->minor != minor
 290             || buf->icanon != icanon) {
 291                 tty_audit_buf_push(buf);
 292                 buf->major = major;
 293                 buf->minor = minor;
 294                 buf->icanon = icanon;
 295         }
 296         do {
 297                 size_t run;
 298
 299                 run = N_TTY_BUF_SIZE - buf->valid;
 300                 if (run > size)
 301                         run = size;
 302                 memcpy(buf->data + buf->valid, data, run);
 303                 buf->valid += run;
 304                 data += run;
 305                 size -= run;
 306                 if (buf->valid == N_TTY_BUF_SIZE)
 307                         tty_audit_buf_push(buf);
 308         } while (size != 0);
 309         mutex_unlock(&buf->mutex);
 310         tty_audit_buf_put(buf);
 311 }
 312
 313 /**
 314  *      tty_audit_push  -       Push buffered data out
 315  *
 316  *      Make sure no audit data is pending on the current process.
 317  */
 318 void tty_audit_push(void)
 319 {
 320         struct tty_audit_buf *buf;
 321         unsigned long flags;
 322
 323         spin_lock_irqsave(&current->sighand->siglock, flags);
 324         if (likely(!current->signal->audit_tty)) {
 325                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
 326                 return;
 327         }
 328         buf = current->signal->tty_audit_buf;
 329         if (buf)
 330                 atomic_inc(&buf->count);
 331         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 332
 333         if (buf) {
 334                 mutex_lock(&buf->mutex);
 335                 tty_audit_buf_push(buf);
 336                 mutex_unlock(&buf->mutex);
 337                 tty_audit_buf_put(buf);
 338         }
 339 }