about summary refs log tree commit diff
path: root/login/utmp_file.c
blob: 1366f38d75ddb33d7f592f0e9bb0597b3506c670 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
/* Copyright (C) 1996, 1997 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>
   and Paul Janzen <pcj@primenet.com>, 1996.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <utmp.h>
#include <sys/file.h>
#include <sys/stat.h>

#include "utmp-private.h"

#ifndef _LIBC
#define _(msg) (msg)
#define __set_errno(val) errno = (val)
#endif


/* Descriptor for the file and position.  */
static int file_fd = INT_MIN;
static off_t file_offset;

static struct utmp last_entry;


/* Functions defined here.  */
static int setutent_file (int reset);
static int getutent_r_file (struct utmp *buffer, struct utmp **result);
static int getutid_r_file (const struct utmp *key, struct utmp *buffer,
			   struct utmp **result);
static int getutline_r_file (const struct utmp *key, struct utmp *buffer,
			     struct utmp **result);
static struct utmp *pututline_file (const struct utmp *data);
static void endutent_file (void);
static int updwtmp_file (const char *file, const struct utmp *utmp);

/* Jump table for file functions.  */
struct utfuncs __libc_utmp_file_functions =
{
  setutent_file,
  getutent_r_file,
  getutid_r_file,
  getutline_r_file,
  pututline_file,
  endutent_file,
  updwtmp_file
};


static int
setutent_file (int reset)
{
  if (file_fd == INT_MIN)
    {
      file_fd = open (__libc_utmp_file_name, O_RDWR);
      if (file_fd == -1)
	{
	  /* Hhm, read-write access did not work.  Try read-only.  */
	  file_fd = open (__libc_utmp_file_name, O_RDONLY);
	  if (file_fd == -1)
	    {
	      perror (_("while opening UTMP file"));
	      return 0;
	    }
	}
      file_offset = 0;

#if _HAVE_UT_TYPE - 0
      /* Make sure the entry won't match.  */
      last_entry.ut_type = -1;
#endif
    }
  else if (reset)
    {
      lseek (file_fd, 0, SEEK_SET);

      /* Remember we are at beginning of file.  */
      file_offset = 0;

#if _HAVE_UT_TYPE - 0
      /* Make sure the entry won't match.  */
      last_entry.ut_type = -1;
#endif
    }

  return 1;
}


static void
endutent_file (void)
{
  if (file_fd >= 0)
    close (file_fd);

  file_fd = INT_MIN;
}


static int
getutent_r_file (struct utmp *buffer, struct utmp **result)
{
  int nbytes;
  struct flock fl;			/* Information struct for locking.  */

  /* Open utmp file if not already done.  */
  if (file_fd == INT_MIN)
    setutent_file (1);

  if (file_fd == -1 || file_offset == -1l)
    {
      /* Not available.  */
      *result = NULL;
      return -1;
    }

  /* XXX The following is not perfect.  Instead of locking the file itself
     Marek Michalkiewicz <marekm@i17linuxb.ists.pwr.wroc.pl> suggests to
     use an extra locking file.  */

  /* Try to get the lock.  */
  memset (&fl, '\0', sizeof (struct flock));
  fl.l_type = F_WRLCK;
  fl.l_whence = SEEK_SET;
  fcntl (file_fd, F_SETLKW, &fl);

  /* Read the next entry.  */
  nbytes = read (file_fd, &last_entry, sizeof (struct utmp));

  /* And unlock the file.  */
  fl.l_type = F_UNLCK;
  fcntl (file_fd, F_SETLKW, &fl);

  if (nbytes != sizeof (struct utmp))
    {
      file_offset = -1l;
      *result = NULL;
      return -1;
    }

  /* Update position pointer.  */
  file_offset += sizeof (struct utmp);

  memcpy (buffer, &last_entry, sizeof (struct utmp));
  *result = buffer;

  return 0;
}


/* For implementing this function we don't use the getutent_r function
   because we can avoid the reposition on every new entry this way.  */
static int
getutline_r_file (const struct utmp *line, struct utmp *buffer,
		  struct utmp **result)
{
  if (file_fd < 0 || file_offset == -1l)
    {
      *result = NULL;
      return -1;
    }

  while (1)
    {
      /* Read the next entry.  */
      if (read (file_fd, &last_entry, sizeof (struct utmp))
	  != sizeof (struct utmp))
	{
	  __set_errno (ESRCH);
	  file_offset = -1l;
	  *result = NULL;
	  return -1;
	}
      file_offset += sizeof (struct utmp);

      /* Stop if we found a user or login entry.  */
      if (
#if _HAVE_UT_TYPE - 0
	  (last_entry.ut_type == USER_PROCESS
	   || last_entry.ut_type == LOGIN_PROCESS)
	  &&
#endif
	  !strncmp (line->ut_line, last_entry.ut_line, sizeof line->ut_line))
	break;
    }

  memcpy (buffer, &last_entry, sizeof (struct utmp));
  *result = buffer;

  return 0;
}


static int
proc_utmp_eq (const struct utmp *entry, const struct utmp *match)
{
  return
    (
#if _HAVE_UT_TYPE - 0
     (entry->ut_type == INIT_PROCESS
      || entry->ut_type == LOGIN_PROCESS
      || entry->ut_type == USER_PROCESS
      || entry->ut_type == DEAD_PROCESS)
     &&
     (match->ut_type == INIT_PROCESS
      || match->ut_type == LOGIN_PROCESS
      || match->ut_type == USER_PROCESS
      || match->ut_type == DEAD_PROCESS)
     &&
#endif
#if _HAVE_UT_ID - 0
     strncmp (entry->ut_id, match->ut_id, sizeof match->ut_id) == 0
#else
     strncmp (entry->ut_line, match->ut_line, sizeof match->ut_line) == 0
#endif
     );
}

static int
internal_getut_r (const struct utmp *id, struct utmp *buffer)
{
#if _HAVE_UT_TYPE - 0
  if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME
      || id->ut_type == OLD_TIME || id->ut_type == NEW_TIME)
    {
      /* Search for next entry with type RUN_LVL, BOOT_TIME,
	 OLD_TIME, or NEW_TIME.  */

      while (1)
	{
	  /* Read the next entry.  */
	  if (read (file_fd, buffer, sizeof (struct utmp))
	      != sizeof (struct utmp))
	    {
	      __set_errno (ESRCH);
	      file_offset = -1l;
	      return -1;
	    }
	  file_offset += sizeof (struct utmp);

	  if (id->ut_type == buffer->ut_type)
	    break;
	}
    }
  else
#endif /* _HAVE_UT_TYPE */
    {
      /* Search for the next entry with the specified ID and with type
	 INIT_PROCESS, LOGIN_PROCESS, USER_PROCESS, or DEAD_PROCESS.  */

      while (1)
	{
	  /* Read the next entry.  */
	  if (read (file_fd, buffer, sizeof (struct utmp))
	      != sizeof (struct utmp))
	    {
	      __set_errno (ESRCH);
	      file_offset = -1l;
	      return -1;
	    }
	  file_offset += sizeof (struct utmp);

	  if (proc_utmp_eq (buffer, id))
	    break;
	}
    }

  return 0;
}


/* For implementing this function we don't use the getutent_r function
   because we can avoid the reposition on every new entry this way.  */
static int
getutid_r_file (const struct utmp *id, struct utmp *buffer,
		struct utmp **result)
{
  if (file_fd < 0 || file_offset == -1l)
    {
      *result = NULL;
      return -1;
    }

  if (internal_getut_r (id, &last_entry) < 0)
    {
      *result = NULL;
      return -1;
    }

  memcpy (buffer, &last_entry, sizeof (struct utmp));
  *result = buffer;

  return 0;
}


static struct utmp *
pututline_file (const struct utmp *data)
{
  struct flock fl;			/* Information struct for locking.  */
  struct utmp buffer;
  struct utmp *pbuf;
  int found;

  if (file_fd < 0)
    /* Something went wrong.  */
    return NULL;

  if (file_fd == INT_MIN)
    /* The file is closed.  Open it again.  */
    setutent_file (0);

  /* Find the correct place to insert the data.  */
  if (file_offset > 0
      && (
#if _HAVE_UT_TYPE - 0
	  (last_entry.ut_type == data->ut_type
	   && (last_entry.ut_type == RUN_LVL
	       || last_entry.ut_type == BOOT_TIME
	       || last_entry.ut_type == OLD_TIME
	       || last_entry.ut_type == NEW_TIME))
	  ||
#endif
	  proc_utmp_eq (&last_entry, data)))
    found = 1;
  else
    found = internal_getut_r (data, &buffer);

  /* Try to lock the file.  */
  memset (&fl, '\0', sizeof (struct flock));
  fl.l_type = F_WRLCK;
  fl.l_whence = SEEK_SET;
  fcntl (file_fd, F_SETLKW, &fl);

  if (found < 0)
    {
      /* We append the next entry.  */
      file_offset = lseek (file_fd, 0, SEEK_END);
      if (file_offset % sizeof (struct utmp) != 0)
	{
	  file_offset -= file_offset % sizeof (struct utmp);
	  ftruncate (file_fd, file_offset);

	  if (lseek (file_fd, 0, SEEK_END) < 0)
	    {
	      pbuf = NULL;
	      goto unlock_return;
	    }
	}
    }
  else
    {
      /* We replace the just read entry.  */
      file_offset -= sizeof (struct utmp);
      lseek (file_fd, file_offset, SEEK_SET);
    }

  /* Write the new data.  */
  if (write (file_fd, data, sizeof (struct utmp)) != sizeof (struct utmp)
      /* If we appended a new record this is only partially written.
	 Remove it.  */
      && found < 0)
    {
      (void) ftruncate (file_fd, file_offset);
      pbuf = NULL;
    }
  else
    {
      file_offset += sizeof (struct utmp);
      pbuf = (struct utmp *) data;
    }

 unlock_return:
   /* And unlock the file.  */
  fl.l_type = F_UNLCK;
  fcntl (file_fd, F_SETLKW, &fl);

  return pbuf;
}


static int
updwtmp_file (const char *file, const struct utmp *utmp)
{
  int result = -1;
  struct stat st;
  ssize_t nbytes;
  int fd;
  
  /* Open WTMP file.  */
  fd = __open (file, O_WRONLY | O_APPEND);
  if (fd < 0)
    return -1;

  /* Try to lock the file.  */
  if (__flock (fd, LOCK_EX | LOCK_NB) < 0 && errno != ENOSYS)
    {
      /* Oh, oh.  The file is already locked.  Wait a bit and try again.  */
      sleep (1);

      /*  This time we ignore the error.  */
      __flock (fd, LOCK_EX | LOCK_NB);
    }

  /* Remember original size of log file.  */
  if (__fstat (fd, &st) < 0)
    goto fail;

  /* Write the entry.  If we can't write all the bytes, reset the file
     size back to the original size.  That way, no partial entries
     will remain.  */
  nbytes = __write (fd, utmp, sizeof (struct utmp));
  if (nbytes != sizeof (struct utmp))
    {
      ftruncate (fd, st.st_size);
      goto fail;
    }

  result = 0;
  
fail:
  /* And unlock the file.  */
  __flock (fd, LOCK_UN);

  /* Close WTMP file.  */
  __close (fd);

  return result;
}