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