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 /**
  71  *      tty_audit_buf_push      -       Push buffered data out
  72  *
  73  *      Generate an audit message from the contents of @buf, which is owned by
  74  *      @tsk with @loginuid.  @buf->mutex must be locked.
  75  */
  76 static void tty_audit_buf_push(struct task_struct *tsk, uid_t loginuid,
  77                                unsigned int sessionid,
  78                                struct tty_audit_buf *buf)
  79 {
  80         struct audit_buffer *ab;
  81
  82         if (buf->valid == 0)
  83                 return;
  84         if (audit_enabled == 0)
  85                 return;
  86         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  87         if (ab) {
  88                 char name[sizeof(tsk->comm)];
  89                 uid_t uid = task_uid(tsk);
  90
  91                 audit_log_format(ab, "tty pid=%u uid=%u auid=%u ses=%u "
  92                                  "major=%d minor=%d comm=",
  93                                  tsk->pid, uid, loginuid, sessionid,
  94                                  buf->major, buf->minor);
  95                 get_task_comm(name, tsk);
  96                 audit_log_untrustedstring(ab, name);
  97                 audit_log_format(ab, " data=");
  98                 audit_log_n_hex(ab, buf->data, buf->valid);
  99                 audit_log_end(ab);
 100         }
 101         buf->valid = 0;
 102 }
 103
 104 /**
 105  *      tty_audit_buf_push_current      -       Push buffered data out
 106  *
 107  *      Generate an audit message from the contents of @buf, which is owned by
 108  *      the current task.  @buf->mutex must be locked.
 109  */
 110 static void tty_audit_buf_push_current(struct tty_audit_buf *buf)
 111 {
 112         uid_t auid = audit_get_loginuid(current);
 113         unsigned int sessionid = audit_get_sessionid(current);
 114         tty_audit_buf_push(current, auid, sessionid, buf);
 115 }
 116
 117 /**
 118  *      tty_audit_exit  -       Handle a task exit
 119  *
 120  *      Make sure all buffered data is written out and deallocate the buffer.
 121  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 122  */
 123 void tty_audit_exit(void)
 124 {
 125         struct tty_audit_buf *buf;
 126
 127         spin_lock_irq(&current->sighand->siglock);
 128         buf = current->signal->tty_audit_buf;
 129         current->signal->tty_audit_buf = NULL;
 130         spin_unlock_irq(&current->sighand->siglock);
 131         if (!buf)
 132                 return;
 133
 134         mutex_lock(&buf->mutex);
 135         tty_audit_buf_push_current(buf);
 136         mutex_unlock(&buf->mutex);
 137
 138         tty_audit_buf_put(buf);
 139 }
 140
 141 /**
 142  *      tty_audit_fork  -       Copy TTY audit state for a new task
 143  *
 144  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 145  */
 146 void tty_audit_fork(struct signal_struct *sig)
 147 {
 148         spin_lock_irq(&current->sighand->siglock);
 149         sig->audit_tty = current->signal->audit_tty;
 150         spin_unlock_irq(&current->sighand->siglock);
 151         sig->tty_audit_buf = NULL;
 152 }
 153
 154 /**
 155  *      tty_audit_push_task     -       Flush task's pending audit data
 156  */
 157 void tty_audit_push_task(struct task_struct *tsk, uid_t loginuid, u32 sessionid)
 158 {
 159         struct tty_audit_buf *buf;
 160
 161         spin_lock_irq(&tsk->sighand->siglock);
 162         buf = tsk->signal->tty_audit_buf;
 163         if (buf)
 164                 atomic_inc(&buf->count);
 165         spin_unlock_irq(&tsk->sighand->siglock);
 166         if (!buf)
 167                 return;
 168
 169         mutex_lock(&buf->mutex);
 170         tty_audit_buf_push(tsk, loginuid, sessionid, buf);
 171         mutex_unlock(&buf->mutex);
 172
 173         tty_audit_buf_put(buf);
 174 }
 175
 176 /**
 177  *      tty_audit_buf_get       -       Get an audit buffer.
 178  *
 179  *      Get an audit buffer for @tty, allocate it if necessary.  Return %NULL
 180  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 181  *      reference to the buffer.
 182  */
 183 static struct tty_audit_buf *tty_audit_buf_get(struct tty_struct *tty)
 184 {
 185         struct tty_audit_buf *buf, *buf2;
 186
 187         buf = NULL;
 188         buf2 = NULL;
 189         spin_lock_irq(&current->sighand->siglock);
 190         if (likely(!current->signal->audit_tty))
 191                 goto out;
 192         buf = current->signal->tty_audit_buf;
 193         if (buf) {
 194                 atomic_inc(&buf->count);
 195                 goto out;
 196         }
 197         spin_unlock_irq(&current->sighand->siglock);
 198
 199         buf2 = tty_audit_buf_alloc(tty->driver->major,
 200                                    tty->driver->minor_start + tty->index,
 201                                    tty->icanon);
 202         if (buf2 == NULL) {
 203                 audit_log_lost("out of memory in TTY auditing");
 204                 return NULL;
 205         }
 206
 207         spin_lock_irq(&current->sighand->siglock);
 208         if (!current->signal->audit_tty)
 209                 goto out;
 210         buf = current->signal->tty_audit_buf;
 211         if (!buf) {
 212                 current->signal->tty_audit_buf = buf2;
 213                 buf = buf2;
 214                 buf2 = NULL;
 215         }
 216         atomic_inc(&buf->count);
 217         /* Fall through */
 218  out:
 219         spin_unlock_irq(&current->sighand->siglock);
 220         if (buf2)
 221                 tty_audit_buf_free(buf2);
 222         return buf;
 223 }
 224
 225 /**
 226  *      tty_audit_add_data      -       Add data for TTY auditing.
 227  *
 228  *      Audit @data of @size from @tty, if necessary.
 229  */
 230 void tty_audit_add_data(struct tty_struct *tty, unsigned char *data,
 231                         size_t size)
 232 {
 233         struct tty_audit_buf *buf;
 234         int major, minor;
 235
 236         if (unlikely(size == 0))
 237                 return;
 238
 239         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 240             && tty->driver->subtype == PTY_TYPE_MASTER)
 241                 return;
 242
 243         buf = tty_audit_buf_get(tty);
 244         if (!buf)
 245                 return;
 246
 247         mutex_lock(&buf->mutex);
 248         major = tty->driver->major;
 249         minor = tty->driver->minor_start + tty->index;
 250         if (buf->major != major || buf->minor != minor
 251             || buf->icanon != tty->icanon) {
 252                 tty_audit_buf_push_current(buf);
 253                 buf->major = major;
 254                 buf->minor = minor;
 255                 buf->icanon = tty->icanon;
 256         }
 257         do {
 258                 size_t run;
 259
 260                 run = N_TTY_BUF_SIZE - buf->valid;
 261                 if (run > size)
 262                         run = size;
 263                 memcpy(buf->data + buf->valid, data, run);
 264                 buf->valid += run;
 265                 data += run;
 266                 size -= run;
 267                 if (buf->valid == N_TTY_BUF_SIZE)
 268                         tty_audit_buf_push_current(buf);
 269         } while (size != 0);
 270         mutex_unlock(&buf->mutex);
 271         tty_audit_buf_put(buf);
 272 }
 273
 274 /**
 275  *      tty_audit_push  -       Push buffered data out
 276  *
 277  *      Make sure no audit data is pending for @tty on the current process.
 278  */
 279 void tty_audit_push(struct tty_struct *tty)
 280 {
 281         struct tty_audit_buf *buf;
 282
 283         spin_lock_irq(&current->sighand->siglock);
 284         if (likely(!current->signal->audit_tty)) {
 285                 spin_unlock_irq(&current->sighand->siglock);
 286                 return;
 287         }
 288         buf = current->signal->tty_audit_buf;
 289         if (buf)
 290                 atomic_inc(&buf->count);
 291         spin_unlock_irq(&current->sighand->siglock);
 292
 293         if (buf) {
 294                 int major, minor;
 295
 296                 major = tty->driver->major;
 297                 minor = tty->driver->minor_start + tty->index;
 298                 mutex_lock(&buf->mutex);
 299                 if (buf->major == major && buf->minor == minor)
 300                         tty_audit_buf_push_current(buf);
 301                 mutex_unlock(&buf->mutex);
 302                 tty_audit_buf_put(buf);
 303         }
 304 }