Line data Source code
1 : /*
2 : * Copyright (C) 2018 Red Hat, Inc.
3 : *
4 : * Author: Daiki Ueno
5 : *
6 : * This file is part of GnuTLS.
7 : *
8 : * The GnuTLS is free software; you can redistribute it and/or
9 : * modify it under the terms of the GNU Lesser General Public License
10 : * as published by the Free Software Foundation; either version 2.1 of
11 : * the License, or (at your option) any later version.
12 : *
13 : * This library is distributed in the hope that it will be useful, but
14 : * WITHOUT ANY WARRANTY; without even the implied warranty of
15 : * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 : * Lesser General Public License for more details.
17 : *
18 : * You should have received a copy of the GNU Lesser General Public License
19 : * along with this program. If not, see <https://www.gnu.org/licenses/>
20 : *
21 : */
22 :
23 : #include "gnutls_int.h"
24 : #include "db.h"
25 : #include "system.h"
26 : #include "tls13/anti_replay.h"
27 :
28 : /* The default time window in milliseconds; RFC8446 suggests the order
29 : * of ten seconds is sufficient for the clients on the Internet. */
30 : #define DEFAULT_WINDOW_MS 10000
31 :
32 : struct gnutls_anti_replay_st {
33 : uint32_t window;
34 : struct timespec start_time;
35 : gnutls_db_add_func db_add_func;
36 : void *db_ptr;
37 : };
38 :
39 : /**
40 : * gnutls_anti_replay_init:
41 : * @anti_replay: is a pointer to #gnutls_anti_replay_t type
42 : *
43 : * This function will allocate and initialize the @anti_replay context
44 : * to be usable for detect replay attacks. The context can then be
45 : * attached to a @gnutls_session_t with
46 : * gnutls_anti_replay_enable().
47 : *
48 : * Returns: Zero or a negative error code on error.
49 : *
50 : * Since: 3.6.5
51 : **/
52 : int
53 9 : gnutls_anti_replay_init(gnutls_anti_replay_t *anti_replay)
54 : {
55 9 : *anti_replay = gnutls_calloc(1, sizeof(struct gnutls_anti_replay_st));
56 9 : if (!*anti_replay)
57 0 : return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);
58 :
59 9 : (*anti_replay)->window = DEFAULT_WINDOW_MS;
60 :
61 9 : gnutls_gettime(&(*anti_replay)->start_time);
62 :
63 9 : return 0;
64 : }
65 :
66 : /**
67 : * gnutls_anti_replay_set_window:
68 : * @anti_replay: is a #gnutls_anti_replay_t type.
69 : * @window: is the time window recording ClientHello, in milliseconds
70 : *
71 : * Sets the time window used for ClientHello recording. In order to
72 : * protect against replay attacks, the server records ClientHello
73 : * messages within this time period from the last update, and
74 : * considers it a replay when a ClientHello outside of the period; if
75 : * a ClientHello arrives within this period, the server checks the
76 : * database and detects duplicates.
77 : *
78 : * For the details of the algorithm, see RFC 8446, section 8.2.
79 : *
80 : * Since: 3.6.5
81 : */
82 : void
83 3 : gnutls_anti_replay_set_window(gnutls_anti_replay_t anti_replay,
84 : unsigned int window)
85 : {
86 3 : anti_replay->window = window;
87 3 : }
88 :
89 : /**
90 : * gnutls_anti_replay_deinit:
91 : * @anti_replay: is a #gnutls_anti_replay type
92 : *
93 : * This function will deinitialize all resources occupied by the given
94 : * anti-replay context.
95 : *
96 : * Since: 3.6.5
97 : **/
98 : void
99 7 : gnutls_anti_replay_deinit(gnutls_anti_replay_t anti_replay)
100 : {
101 7 : gnutls_free(anti_replay);
102 7 : }
103 :
104 : /**
105 : * gnutls_anti_replay_enable:
106 : * @session: is a #gnutls_session_t type.
107 : * @anti_replay: is a #gnutls_anti_replay_t type.
108 : *
109 : * Request that the server should use anti-replay mechanism.
110 : *
111 : * Since: 3.6.5
112 : **/
113 : void
114 16 : gnutls_anti_replay_enable(gnutls_session_t session,
115 : gnutls_anti_replay_t anti_replay)
116 : {
117 16 : if (unlikely(session->security_parameters.entity != GNUTLS_SERVER)) {
118 0 : gnutls_assert();
119 0 : return;
120 : }
121 :
122 16 : session->internals.anti_replay = anti_replay;
123 : }
124 :
125 : int
126 14 : _gnutls_anti_replay_check(gnutls_anti_replay_t anti_replay,
127 : uint32_t client_ticket_age,
128 : struct timespec *ticket_creation_time,
129 : gnutls_datum_t *id)
130 : {
131 14 : struct timespec now;
132 14 : time_t window;
133 14 : uint32_t server_ticket_age, diff;
134 14 : gnutls_datum_t key = { NULL, 0 };
135 14 : gnutls_datum_t entry = { NULL, 0 };
136 14 : unsigned char key_buffer[MAX_HASH_SIZE + 12];
137 14 : unsigned char entry_buffer[12]; /* magic + timestamp + expire_time */
138 14 : unsigned char *p;
139 14 : int ret;
140 :
141 14 : if (unlikely(id->size > MAX_HASH_SIZE))
142 0 : return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
143 :
144 14 : gnutls_gettime(&now);
145 14 : server_ticket_age = timespec_sub_ms(&now, ticket_creation_time);
146 :
147 : /* It shouldn't be possible that the server's view of ticket
148 : * age is smaller than the client's view.
149 : */
150 14 : if (unlikely(server_ticket_age < client_ticket_age))
151 1 : return gnutls_assert_val(GNUTLS_E_ILLEGAL_PARAMETER);
152 :
153 : /* If ticket is created before recording has started, discard
154 : * reject early data.
155 : */
156 13 : if (_gnutls_timespec_cmp(ticket_creation_time,
157 : &anti_replay->start_time) < 0) {
158 1 : _gnutls_handshake_log("anti_replay: ticket is created before recording has started\n");
159 1 : return gnutls_assert_val(GNUTLS_E_EARLY_DATA_REJECTED);
160 : }
161 :
162 : /* If certain amount of time (window) has elapsed, rollover
163 : * the recording.
164 : */
165 12 : diff = timespec_sub_ms(&now, &anti_replay->start_time);
166 12 : if (diff > anti_replay->window)
167 2 : gnutls_gettime(&anti_replay->start_time);
168 :
169 : /* If expected_arrival_time is out of window, reject early
170 : * data.
171 : */
172 12 : if (server_ticket_age - client_ticket_age > anti_replay->window) {
173 1 : _gnutls_handshake_log("anti_replay: server ticket age: %u, client ticket age: %u\n",
174 : server_ticket_age,
175 : client_ticket_age);
176 1 : return gnutls_assert_val(GNUTLS_E_EARLY_DATA_REJECTED);
177 : }
178 :
179 : /* Check if the ClientHello is stored in the database.
180 : */
181 11 : if (!anti_replay->db_add_func)
182 0 : return gnutls_assert_val(GNUTLS_E_EARLY_DATA_REJECTED);
183 :
184 : /* Create a key for database lookup, prefixing window start
185 : * time to ID. Note that this shouldn't clash with session ID
186 : * used in TLS 1.2, because such IDs are 32 octets, while here
187 : * the key becomes 44+ octets.
188 : */
189 11 : p = key_buffer;
190 11 : _gnutls_write_uint32((uint64_t) anti_replay->start_time.tv_sec >> 32, p);
191 11 : p += 4;
192 11 : _gnutls_write_uint32(anti_replay->start_time.tv_sec & 0xFFFFFFFF, p);
193 11 : p += 4;
194 11 : _gnutls_write_uint32(anti_replay->start_time.tv_nsec, p);
195 11 : p += 4;
196 11 : memcpy(p, id->data, id->size);
197 11 : p += id->size;
198 11 : key.data = key_buffer;
199 11 : key.size = p - key_buffer;
200 :
201 : /* Create an entry to be stored on database if the lookup
202 : * failed. This is formatted so that
203 : * gnutls_db_check_entry_expire_time() work.
204 : */
205 11 : p = entry_buffer;
206 11 : _gnutls_write_uint32(PACKED_SESSION_MAGIC, p);
207 11 : p += 4;
208 11 : _gnutls_write_uint32(now.tv_sec, p);
209 11 : p += 4;
210 11 : window = anti_replay->window / 1000;
211 11 : _gnutls_write_uint32(window, p);
212 11 : p += 4;
213 11 : entry.data = entry_buffer;
214 11 : entry.size = p - entry_buffer;
215 :
216 22 : ret = anti_replay->db_add_func(anti_replay->db_ptr,
217 11 : (uint64_t)now.tv_sec+(uint64_t)window, &key, &entry);
218 11 : if (ret < 0) {
219 4 : _gnutls_handshake_log("anti_replay: duplicate ClientHello found\n");
220 4 : return gnutls_assert_val(GNUTLS_E_EARLY_DATA_REJECTED);
221 : }
222 :
223 : return 0;
224 : }
225 :
226 : /**
227 : * gnutls_anti_replay_set_ptr:
228 : * @anti_replay: is a #gnutls_anti_replay_t type.
229 : * @ptr: is the pointer
230 : *
231 : * Sets the pointer that will be provided to db add function
232 : * as the first argument.
233 : **/
234 9 : void gnutls_anti_replay_set_ptr(gnutls_anti_replay_t anti_replay, void *ptr)
235 : {
236 9 : anti_replay->db_ptr = ptr;
237 9 : }
238 :
239 : /**
240 : * gnutls_anti_replay_set_add_function:
241 : * @anti_replay: is a #gnutls_anti_replay_t type.
242 : * @add_func: is the function.
243 : *
244 : * Sets the function that will be used to store an entry if it is not
245 : * already present in the resumed sessions database. This function returns 0
246 : * if the entry is successfully stored, and a negative error code
247 : * otherwise. In particular, if the entry is found in the database,
248 : * it returns %GNUTLS_E_DB_ENTRY_EXISTS.
249 : *
250 : * The arguments to the @add_func are:
251 : * - %ptr: the pointer set with gnutls_anti_replay_set_ptr()
252 : * - %exp_time: the expiration time of the entry
253 : * - %key: a pointer to the key
254 : * - %data: a pointer to data to store
255 : *
256 : * The data set by this function can be examined using
257 : * gnutls_db_check_entry_expire_time() and gnutls_db_check_entry_time().
258 : *
259 : * Since: 3.6.5
260 : **/
261 : void
262 9 : gnutls_anti_replay_set_add_function(gnutls_anti_replay_t anti_replay,
263 : gnutls_db_add_func add_func)
264 : {
265 9 : anti_replay->db_add_func = add_func;
266 9 : }
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