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         dev_t dev;              /* 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->dev = MKDEV(0, 0);
  38         buf->icanon = 0;
  39         buf->valid = 0;
  40         return buf;
  41
  42 err_buf:
  43         kfree(buf);
  44 err:
  45         return NULL;
  46 }
  47
  48 static void tty_audit_buf_free(struct tty_audit_buf *buf)
  49 {
  50         WARN_ON(buf->valid != 0);
  51         kfree(buf->data);
  52         kfree(buf);
  53 }
  54
  55 static void tty_audit_buf_put(struct tty_audit_buf *buf)
  56 {
  57         if (atomic_dec_and_test(&buf->count))
  58                 tty_audit_buf_free(buf);
  59 }
  60
  61 static void tty_audit_log(const char *description, dev_t dev,
  62                           unsigned char *data, size_t size)
  63 {
  64         struct audit_buffer *ab;
  65         struct task_struct *tsk = current;
  66         pid_t pid = task_pid_nr(tsk);
  67         uid_t uid = from_kuid(&init_user_ns, task_uid(tsk));
  68         uid_t loginuid = from_kuid(&init_user_ns, audit_get_loginuid(tsk));
  69         unsigned int sessionid = audit_get_sessionid(tsk);
  70
  71         ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_TTY);
  72         if (ab) {
  73                 char name[sizeof(tsk->comm)];
  74
  75                 audit_log_format(ab, "%s pid=%u uid=%u auid=%u ses=%u major=%d"
  76                                  " minor=%d comm=", description, pid, uid,
  77                                  loginuid, sessionid, MAJOR(dev), MINOR(dev));
  78                 get_task_comm(name, tsk);
  79                 audit_log_untrustedstring(ab, name);
  80                 audit_log_format(ab, " data=");
  81                 audit_log_n_hex(ab, data, size);
  82                 audit_log_end(ab);
  83         }
  84 }
  85
  86 /**
  87  *      tty_audit_buf_push      -       Push buffered data out
  88  *
  89  *      Generate an audit message from the contents of @buf, which is owned by
  90  *      the current task.  @buf->mutex must be locked.
  91  */
  92 static void tty_audit_buf_push(struct tty_audit_buf *buf)
  93 {
  94         if (buf->valid == 0)
  95                 return;
  96         if (audit_enabled == 0) {
  97                 buf->valid = 0;
  98                 return;
  99         }
 100         tty_audit_log("tty", buf->dev, buf->data, buf->valid);
 101         buf->valid = 0;
 102 }
 103
 104 /**
 105  *      tty_audit_exit  -       Handle a task exit
 106  *
 107  *      Make sure all buffered data is written out and deallocate the buffer.
 108  *      Only needs to be called if current->signal->tty_audit_buf != %NULL.
 109  */
 110 void tty_audit_exit(void)
 111 {
 112         struct tty_audit_buf *buf;
 113
 114         buf = current->signal->tty_audit_buf;
 115         current->signal->tty_audit_buf = NULL;
 116         if (!buf)
 117                 return;
 118
 119         mutex_lock(&buf->mutex);
 120         tty_audit_buf_push(buf);
 121         mutex_unlock(&buf->mutex);
 122
 123         tty_audit_buf_put(buf);
 124 }
 125
 126 /**
 127  *      tty_audit_fork  -       Copy TTY audit state for a new task
 128  *
 129  *      Set up TTY audit state in @sig from current.  @sig needs no locking.
 130  */
 131 void tty_audit_fork(struct signal_struct *sig)
 132 {
 133         sig->audit_tty = current->signal->audit_tty;
 134 }
 135
 136 /**
 137  *      tty_audit_tiocsti       -       Log TIOCSTI
 138  */
 139 void tty_audit_tiocsti(struct tty_struct *tty, char ch)
 140 {
 141         struct tty_audit_buf *buf;
 142         dev_t dev;
 143         unsigned long flags;
 144
 145         spin_lock_irqsave(&current->sighand->siglock, flags);
 146         buf = current->signal->tty_audit_buf;
 147         if (buf)
 148                 atomic_inc(&buf->count);
 149         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 150
 151         dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
 152         if (buf) {
 153                 mutex_lock(&buf->mutex);
 154                 if (buf->dev == dev)
 155                         tty_audit_buf_push(buf);
 156                 mutex_unlock(&buf->mutex);
 157                 tty_audit_buf_put(buf);
 158         }
 159
 160         if (audit_enabled && (current->signal->audit_tty & AUDIT_TTY_ENABLE)) {
 161                 kuid_t auid;
 162                 unsigned int sessionid;
 163
 164                 auid = audit_get_loginuid(current);
 165                 sessionid = audit_get_sessionid(current);
 166                 tty_audit_log("ioctl=TIOCSTI", dev, &ch, 1);
 167         }
 168 }
 169
 170 /**
 171  *      tty_audit_push  -       Flush current's pending audit data
 172  *
 173  *      Returns 0 if success, -EPERM if tty audit is disabled
 174  */
 175 int tty_audit_push(void)
 176 {
 177         struct tty_audit_buf *buf;
 178         unsigned long flags;
 179
 180         if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
 181                 return -EPERM;
 182
 183         spin_lock_irqsave(&current->sighand->siglock, flags);
 184         buf = current->signal->tty_audit_buf;
 185         if (buf)
 186                 atomic_inc(&buf->count);
 187         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 188
 189         if (buf) {
 190                 mutex_lock(&buf->mutex);
 191                 tty_audit_buf_push(buf);
 192                 mutex_unlock(&buf->mutex);
 193
 194                 tty_audit_buf_put(buf);
 195         }
 196         return 0;
 197 }
 198
 199 /**
 200  *      tty_audit_buf_get       -       Get an audit buffer.
 201  *
 202  *      Get an audit buffer, allocate it if necessary.  Return %NULL
 203  *      if TTY auditing is disabled or out of memory.  Otherwise, return a new
 204  *      reference to the buffer.
 205  */
 206 static struct tty_audit_buf *tty_audit_buf_get(void)
 207 {
 208         struct tty_audit_buf *buf, *buf2;
 209         unsigned long flags;
 210
 211         buf = NULL;
 212         buf2 = NULL;
 213         spin_lock_irqsave(&current->sighand->siglock, flags);
 214         buf = current->signal->tty_audit_buf;
 215         if (buf) {
 216                 atomic_inc(&buf->count);
 217                 goto out;
 218         }
 219         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 220
 221         buf2 = tty_audit_buf_alloc();
 222         if (buf2 == NULL) {
 223                 audit_log_lost("out of memory in TTY auditing");
 224                 return NULL;
 225         }
 226
 227         if (~current->signal->audit_tty & AUDIT_TTY_ENABLE)
 228                 goto out;
 229
 230         spin_lock_irqsave(&current->sighand->siglock, flags);
 231         buf = current->signal->tty_audit_buf;
 232         if (!buf) {
 233                 current->signal->tty_audit_buf = buf2;
 234                 buf = buf2;
 235                 buf2 = NULL;
 236         }
 237         atomic_inc(&buf->count);
 238         /* Fall through */
 239  out:
 240         spin_unlock_irqrestore(&current->sighand->siglock, flags);
 241         if (buf2)
 242                 tty_audit_buf_free(buf2);
 243         return buf;
 244 }
 245
 246 /**
 247  *      tty_audit_add_data      -       Add data for TTY auditing.
 248  *
 249  *      Audit @data of @size from @tty, if necessary.
 250  */
 251 void tty_audit_add_data(struct tty_struct *tty, const void *data, size_t size)
 252 {
 253         struct tty_audit_buf *buf;
 254         unsigned int icanon = !!L_ICANON(tty);
 255         unsigned int audit_tty;
 256         dev_t dev;
 257
 258         if (unlikely(size == 0))
 259                 return;
 260
 261         if (tty->driver->type == TTY_DRIVER_TYPE_PTY
 262             && tty->driver->subtype == PTY_TYPE_MASTER)
 263                 return;
 264
 265         audit_tty = READ_ONCE(current->signal->audit_tty);
 266         if (~audit_tty & AUDIT_TTY_ENABLE)
 267                 return;
 268         if ((~audit_tty & AUDIT_TTY_LOG_PASSWD) && icanon && !L_ECHO(tty))
 269                 return;
 270
 271         buf = tty_audit_buf_get();
 272         if (!buf)
 273                 return;
 274
 275         mutex_lock(&buf->mutex);
 276         dev = MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
 277         if (buf->dev != dev || buf->icanon != icanon) {
 278                 tty_audit_buf_push(buf);
 279                 buf->dev = dev;
 280                 buf->icanon = icanon;
 281         }
 282         do {
 283                 size_t run;
 284
 285                 run = N_TTY_BUF_SIZE - buf->valid;
 286                 if (run > size)
 287                         run = size;
 288                 memcpy(buf->data + buf->valid, data, run);
 289                 buf->valid += run;
 290                 data += run;
 291                 size -= run;
 292                 if (buf->valid == N_TTY_BUF_SIZE)
 293                         tty_audit_buf_push(buf);
 294         } while (size != 0);
 295         mutex_unlock(&buf->mutex);
 296         tty_audit_buf_put(buf);
 297 }