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
gnutls_anti_replay_init(gnutls_anti_replay_t * anti_replay)53 gnutls_anti_replay_init(gnutls_anti_replay_t *anti_replay)
54 {
55 *anti_replay = gnutls_calloc(1, sizeof(struct gnutls_anti_replay_st));
56 if (!*anti_replay)
57 return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);
58
59 (*anti_replay)->window = DEFAULT_WINDOW_MS;
60
61 gnutls_gettime(&(*anti_replay)->start_time);
62
63 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
gnutls_anti_replay_set_window(gnutls_anti_replay_t anti_replay,unsigned int window)83 gnutls_anti_replay_set_window(gnutls_anti_replay_t anti_replay,
84 unsigned int window)
85 {
86 anti_replay->window = window;
87 }
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
gnutls_anti_replay_deinit(gnutls_anti_replay_t anti_replay)99 gnutls_anti_replay_deinit(gnutls_anti_replay_t anti_replay)
100 {
101 gnutls_free(anti_replay);
102 }
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
gnutls_anti_replay_enable(gnutls_session_t session,gnutls_anti_replay_t anti_replay)114 gnutls_anti_replay_enable(gnutls_session_t session,
115 gnutls_anti_replay_t anti_replay)
116 {
117 if (unlikely(session->security_parameters.entity != GNUTLS_SERVER)) {
118 gnutls_assert();
119 return;
120 }
121
122 session->internals.anti_replay = anti_replay;
123 }
124
125 int
_gnutls_anti_replay_check(gnutls_anti_replay_t anti_replay,uint32_t client_ticket_age,struct timespec * ticket_creation_time,gnutls_datum_t * id)126 _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 struct timespec now;
132 time_t window;
133 uint32_t server_ticket_age, diff;
134 gnutls_datum_t key = { NULL, 0 };
135 gnutls_datum_t entry = { NULL, 0 };
136 unsigned char key_buffer[MAX_HASH_SIZE + 12];
137 unsigned char entry_buffer[12]; /* magic + timestamp + expire_time */
138 unsigned char *p;
139 int ret;
140
141 if (unlikely(id->size > MAX_HASH_SIZE))
142 return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);
143
144 gnutls_gettime(&now);
145 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 if (unlikely(server_ticket_age < client_ticket_age))
151 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 if (_gnutls_timespec_cmp(ticket_creation_time,
157 &anti_replay->start_time) < 0) {
158 _gnutls_handshake_log("anti_replay: ticket is created before recording has started\n");
159 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 diff = timespec_sub_ms(&now, &anti_replay->start_time);
166 if (diff > anti_replay->window)
167 gnutls_gettime(&anti_replay->start_time);
168
169 /* If expected_arrival_time is out of window, reject early
170 * data.
171 */
172 if (server_ticket_age - client_ticket_age > anti_replay->window) {
173 _gnutls_handshake_log("anti_replay: server ticket age: %u, client ticket age: %u\n",
174 server_ticket_age,
175 client_ticket_age);
176 return gnutls_assert_val(GNUTLS_E_EARLY_DATA_REJECTED);
177 }
178
179 /* Check if the ClientHello is stored in the database.
180 */
181 if (!anti_replay->db_add_func)
182 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 p = key_buffer;
190 _gnutls_write_uint32((uint64_t) anti_replay->start_time.tv_sec >> 32, p);
191 p += 4;
192 _gnutls_write_uint32(anti_replay->start_time.tv_sec & 0xFFFFFFFF, p);
193 p += 4;
194 _gnutls_write_uint32(anti_replay->start_time.tv_nsec, p);
195 p += 4;
196 memcpy(p, id->data, id->size);
197 p += id->size;
198 key.data = key_buffer;
199 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 p = entry_buffer;
206 _gnutls_write_uint32(PACKED_SESSION_MAGIC, p);
207 p += 4;
208 _gnutls_write_uint32(now.tv_sec, p);
209 p += 4;
210 window = anti_replay->window / 1000;
211 _gnutls_write_uint32(window, p);
212 p += 4;
213 entry.data = entry_buffer;
214 entry.size = p - entry_buffer;
215
216 ret = anti_replay->db_add_func(anti_replay->db_ptr,
217 (uint64_t)now.tv_sec+(uint64_t)window, &key, &entry);
218 if (ret < 0) {
219 _gnutls_handshake_log("anti_replay: duplicate ClientHello found\n");
220 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 **/
gnutls_anti_replay_set_ptr(gnutls_anti_replay_t anti_replay,void * ptr)234 void gnutls_anti_replay_set_ptr(gnutls_anti_replay_t anti_replay, void *ptr)
235 {
236 anti_replay->db_ptr = ptr;
237 }
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
gnutls_anti_replay_set_add_function(gnutls_anti_replay_t anti_replay,gnutls_db_add_func add_func)262 gnutls_anti_replay_set_add_function(gnutls_anti_replay_t anti_replay,
263 gnutls_db_add_func add_func)
264 {
265 anti_replay->db_add_func = add_func;
266 }
267