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 
33 static dbus_bool_t
do_check_nonce(int fd,const DBusString * nonce,DBusError * error)34 do_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  */
100 dbus_bool_t
_dbus_read_nonce(const DBusString * fname,DBusString * nonce,DBusError * error)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 
133 int
_dbus_accept_with_noncefile(int listen_fd,const DBusNonceFile * noncefile)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 
157 static dbus_bool_t
generate_and_write_nonce(const DBusString * filename,DBusError * error)158 generate_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  */
194 dbus_bool_t
_dbus_send_nonce(int fd,const DBusString * noncefile,DBusError * error)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 
237 static dbus_bool_t
do_noncefile_create(DBusNonceFile * noncefile,DBusError * error,dbus_bool_t use_subdir)238 do_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  */
331 dbus_bool_t
_dbus_noncefile_create(DBusNonceFile * noncefile,DBusError * error)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  */
345 dbus_bool_t
_dbus_noncefile_delete(DBusNonceFile * noncefile,DBusError * error)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  */
366 dbus_bool_t
_dbus_noncefile_create(DBusNonceFile * noncefile,DBusError * error)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  */
380 dbus_bool_t
_dbus_noncefile_delete(DBusNonceFile * noncefile,DBusError * error)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  */
400 const DBusString*
_dbus_noncefile_get_path(const DBusNonceFile * noncefile)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  */
417 dbus_bool_t
_dbus_noncefile_check_nonce(int fd,const DBusNonceFile * noncefile,DBusError * error)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