1/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
2/* dbus-nonce.c  Nonce handling functions used by nonce-tcp (internal to D-Bus implementation)
3 *
4 * Copyright (C) 2009 Klaralvdalens Datakonsult AB, a KDAB Group company, info@kdab.net
5 *
6 * Licensed under the Academic Free License version 2.1
7 *
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License as published by
10 * the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
21 *
22 */
23
24#include <config.h>
25// major sections of this file are modified code from libassuan, (C) FSF
26#include "dbus-nonce.h"
27#include "dbus-internals.h"
28#include "dbus-protocol.h"
29#include "dbus-sysdeps.h"
30
31#include <stdio.h>
32
33static dbus_bool_t
34do_check_nonce (int fd, const DBusString *nonce, DBusError *error)
35{
36  DBusString buffer;
37  DBusString p;
38  size_t nleft;
39  dbus_bool_t result;
40  int n;
41
42  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
43
44  nleft = 16;
45
46  if (   !_dbus_string_init (&buffer)
47      || !_dbus_string_init (&p) ) {
48        dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
49        _dbus_string_free (&p);
50        _dbus_string_free (&buffer);
51        return FALSE;
52      }
53
54  while (nleft)
55    {
56      n = _dbus_read_socket (fd, &p, nleft);
57      if (n == -1 && _dbus_get_is_errno_eintr())
58        ;
59      else if (n == -1 && _dbus_get_is_errno_eagain_or_ewouldblock())
60        _dbus_sleep_milliseconds (100);
61      else if (n==-1)
62        {
63          dbus_set_error (error, DBUS_ERROR_IO_ERROR, "Could not read nonce from socket (fd=%d)", fd );
64          _dbus_string_free (&p);
65          _dbus_string_free (&buffer);
66          return FALSE;
67        }
68      else if (!n)
69        {
70          _dbus_string_free (&p);
71          _dbus_string_free (&buffer);
72          dbus_set_error (error, DBUS_ERROR_IO_ERROR, "Could not read nonce from socket (fd=%d)", fd );
73          return FALSE;
74        }
75      else
76        {
77          _dbus_string_append_len(&buffer, _dbus_string_get_const_data (&p), n);
78          nleft -= n;
79        }
80    }
81
82  result =  _dbus_string_equal_len (&buffer, nonce, 16);
83  if (!result)
84    dbus_set_error (error, DBUS_ERROR_ACCESS_DENIED, "Nonces do not match, access denied (fd=%d)", fd );
85
86  _dbus_string_free (&p);
87  _dbus_string_free (&buffer);
88
89  return result;
90}
91
92/**
93 * reads the nonce from the nonce file and stores it in a string
94 *
95 * @param fname the file to read the nonce from
96 * @param nonce returns the nonce. Must be an initialized string, the nonce will be appended.
97 * @param error error object to report possible errors
98 * @return FALSE iff reading the nonce fails (error is set then)
99 */
100dbus_bool_t
101_dbus_read_nonce (const DBusString *fname, DBusString *nonce, DBusError* error)
102{
103  FILE *fp;
104  char buffer[17];
105  size_t nread;
106
107  buffer[sizeof buffer - 1] = '\0';
108
109  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
110
111  _dbus_verbose ("reading nonce from file: %s\n", _dbus_string_get_const_data (fname));
112
113
114  fp = fopen (_dbus_string_get_const_data (fname), "rb");
115  if (!fp)
116    return FALSE;
117  nread = fread (buffer, 1, sizeof buffer - 1, fp);
118  fclose (fp);
119  if (!nread)
120    {
121      dbus_set_error (error, DBUS_ERROR_FILE_NOT_FOUND, "Could not read nonce from file %s", _dbus_string_get_const_data (fname));
122      return FALSE;
123    }
124
125  if (!_dbus_string_append_len (nonce, buffer, sizeof buffer - 1 ))
126    {
127      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
128      return FALSE;
129    }
130  return TRUE;
131}
132
133int
134_dbus_accept_with_noncefile (int listen_fd, const DBusNonceFile *noncefile)
135{
136  int fd;
137  DBusString nonce;
138
139  _dbus_assert (noncefile != NULL);
140  if (!_dbus_string_init (&nonce))
141    return -1;
142  //PENDING(kdab): set better errors
143  if (_dbus_read_nonce (_dbus_noncefile_get_path(noncefile), &nonce, NULL) != TRUE)
144    return -1;
145  fd = _dbus_accept (listen_fd);
146  if (_dbus_socket_is_invalid (fd))
147    return fd;
148  if (do_check_nonce(fd, &nonce, NULL) != TRUE) {
149    _dbus_verbose ("nonce check failed. Closing socket.\n");
150    _dbus_close_socket(fd, NULL);
151    return -1;
152  }
153
154  return fd;
155}
156
157static dbus_bool_t
158generate_and_write_nonce (const DBusString *filename, DBusError *error)
159{
160  DBusString nonce;
161  dbus_bool_t ret;
162
163  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
164
165  if (!_dbus_string_init (&nonce))
166    {
167      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
168      return FALSE;
169    }
170
171  if (!_dbus_generate_random_bytes (&nonce, 16))
172    {
173      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
174      _dbus_string_free (&nonce);
175      return FALSE;
176    }
177
178  ret = _dbus_string_save_to_file (&nonce, filename, FALSE, error);
179
180  _dbus_string_free (&nonce);
181
182  return ret;
183}
184
185/**
186 * sends the nonce over a given socket. Blocks while doing so.
187 *
188 * @param fd the file descriptor to write the nonce data to (usually a socket)
189 * @param noncefile the noncefile location to read the nonce from
190 * @param error contains error details if FALSE is returned
191 * @return TRUE iff the nonce was successfully sent. Note that this does not
192 * indicate whether the server accepted the nonce.
193 */
194dbus_bool_t
195_dbus_send_nonce (int fd, const DBusString *noncefile, DBusError *error)
196{
197  dbus_bool_t read_result;
198  int send_result;
199  DBusString nonce;
200
201  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
202
203  if (_dbus_string_get_length (noncefile) == 0)
204    return FALSE;
205
206  if (!_dbus_string_init (&nonce))
207    {
208      dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
209      return FALSE;
210    }
211
212  read_result = _dbus_read_nonce (noncefile, &nonce, error);
213  if (!read_result)
214    {
215      _DBUS_ASSERT_ERROR_IS_SET (error);
216      _dbus_string_free (&nonce);
217      return FALSE;
218    }
219  _DBUS_ASSERT_ERROR_IS_CLEAR (error);
220
221  send_result = _dbus_write_socket (fd, &nonce, 0, _dbus_string_get_length (&nonce));
222
223  _dbus_string_free (&nonce);
224
225  if (send_result == -1)
226    {
227      dbus_set_error (error,
228                      _dbus_error_from_system_errno (),
229                      "Failed to send nonce (fd=%d): %s",
230                      fd, _dbus_strerror_from_errno ());
231      return FALSE;
232    }
233
234  return TRUE;
235}
236
237static dbus_bool_t
238do_noncefile_create (DBusNonceFile *noncefile,
239                     DBusError *error,
240                     dbus_bool_t use_subdir)
241{
242    DBusString randomStr;
243
244    _DBUS_ASSERT_ERROR_IS_CLEAR (error);
245
246    _dbus_assert (noncefile);
247
248    if (!_dbus_string_init (&randomStr))
249      {
250        dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
251        goto on_error;
252      }
253
254    if (!_dbus_generate_random_ascii (&randomStr, 8))
255      {
256        dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
257        goto on_error;
258      }
259
260    if (!_dbus_string_init (&noncefile->dir)
261        || !_dbus_string_append (&noncefile->dir, _dbus_get_tmpdir()))
262      {
263        dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
264        goto on_error;
265      }
266    if (use_subdir)
267      {
268        if (!_dbus_string_append (&noncefile->dir, "/dbus_nonce-")
269            || !_dbus_string_append (&noncefile->dir, _dbus_string_get_const_data (&randomStr)) )
270          {
271            dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
272            goto on_error;
273          }
274        if (!_dbus_string_init (&noncefile->path)
275            || !_dbus_string_copy (&noncefile->dir, 0, &noncefile->path, 0)
276            || !_dbus_string_append (&noncefile->path, "/nonce"))
277          {
278            dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
279            goto on_error;
280          }
281        if (!_dbus_create_directory (&noncefile->dir, error))
282          {
283            _DBUS_ASSERT_ERROR_IS_SET (error);
284            goto on_error;
285          }
286        _DBUS_ASSERT_ERROR_IS_CLEAR (error);
287
288      }
289    else
290      {
291        if (!_dbus_string_init (&noncefile->path)
292            || !_dbus_string_copy (&noncefile->dir, 0, &noncefile->path, 0)
293            || !_dbus_string_append (&noncefile->path, "/dbus_nonce-")
294            || !_dbus_string_append (&noncefile->path, _dbus_string_get_const_data (&randomStr)))
295          {
296            dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
297            goto on_error;
298          }
299
300      }
301
302    if (!generate_and_write_nonce (&noncefile->path, error))
303      {
304        _DBUS_ASSERT_ERROR_IS_SET (error);
305        if (use_subdir)
306          _dbus_delete_directory (&noncefile->dir, NULL); //we ignore possible errors deleting the dir and return the write error instead
307        goto on_error;
308      }
309    _DBUS_ASSERT_ERROR_IS_CLEAR (error);
310
311    _dbus_string_free (&randomStr);
312
313    return TRUE;
314  on_error:
315    if (use_subdir)
316      _dbus_delete_directory (&noncefile->dir, NULL);
317    _dbus_string_free (&noncefile->dir);
318    _dbus_string_free (&noncefile->path);
319    _dbus_string_free (&randomStr);
320    return FALSE;
321}
322
323#ifdef DBUS_WIN
324/**
325 * creates a nonce file in a user-readable location and writes a generated nonce to it
326 *
327 * @param noncefile returns the nonce file location
328 * @param error error details if creating the nonce file fails
329 * @return TRUE iff the nonce file was successfully created
330 */
331dbus_bool_t
332_dbus_noncefile_create (DBusNonceFile *noncefile,
333                        DBusError *error)
334{
335    return do_noncefile_create (noncefile, error, /*use_subdir=*/FALSE);
336}
337
338/**
339 * deletes the noncefile and frees the DBusNonceFile object.
340 *
341 * @param noncefile the nonce file to delete. Contents will be freed.
342 * @param error error details if the nonce file could not be deleted
343 * @return TRUE
344 */
345dbus_bool_t
346_dbus_noncefile_delete (DBusNonceFile *noncefile,
347                        DBusError *error)
348{
349    _DBUS_ASSERT_ERROR_IS_CLEAR (error);
350
351    _dbus_delete_file (&noncefile->path, error);
352    _dbus_string_free (&noncefile->dir);
353    _dbus_string_free (&noncefile->path);
354    return TRUE;
355}
356
357#else
358/**
359 * creates a nonce file in a user-readable location and writes a generated nonce to it.
360 * Initializes the noncefile object.
361 *
362 * @param noncefile returns the nonce file location
363 * @param error error details if creating the nonce file fails
364 * @return TRUE iff the nonce file was successfully created
365 */
366dbus_bool_t
367_dbus_noncefile_create (DBusNonceFile *noncefile,
368                        DBusError *error)
369{
370    return do_noncefile_create (noncefile, error, /*use_subdir=*/TRUE);
371}
372
373/**
374 * deletes the noncefile and frees the DBusNonceFile object.
375 *
376 * @param noncefile the nonce file to delete. Contents will be freed.
377 * @param error error details if the nonce file could not be deleted
378 * @return TRUE
379 */
380dbus_bool_t
381_dbus_noncefile_delete (DBusNonceFile *noncefile,
382                        DBusError *error)
383{
384    _DBUS_ASSERT_ERROR_IS_CLEAR (error);
385
386    _dbus_delete_directory (&noncefile->dir, error);
387    _dbus_string_free (&noncefile->dir);
388    _dbus_string_free (&noncefile->path);
389    return TRUE;
390}
391#endif
392
393
394/**
395 * returns the absolute file path of the nonce file
396 *
397 * @param noncefile an initialized noncefile object
398 * @return the absolute path of the nonce file
399 */
400const DBusString*
401_dbus_noncefile_get_path (const DBusNonceFile *noncefile)
402{
403    _dbus_assert (noncefile);
404    return &noncefile->path;
405}
406
407/**
408 * reads data from a file descriptor and checks if the received data matches
409 * the data in the given noncefile.
410 *
411 * @param fd the file descriptor to read the nonce from
412 * @param noncefile the nonce file to check the received data against
413 * @param error error details on fail
414 * @return TRUE iff a nonce could be successfully read from the file descriptor
415 * and matches the nonce from the given nonce file
416 */
417dbus_bool_t
418_dbus_noncefile_check_nonce (int fd,
419                             const DBusNonceFile *noncefile,
420                             DBusError* error)
421{
422    return do_check_nonce (fd, _dbus_noncefile_get_path (noncefile), error);
423}
424
425
426/** @} end of nonce */
427