1/*
2 * TLS server tickets callbacks implementation
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20#include "common.h"
21
22#if defined(MBEDTLS_SSL_TICKET_C)
23
24#include "mbedtls/platform.h"
25
26#include "mbedtls/ssl_internal.h"
27#include "mbedtls/ssl_ticket.h"
28#include "mbedtls/error.h"
29#include "mbedtls/platform_util.h"
30
31#include <string.h>
32
33/*
34 * Initialize context
35 */
36void mbedtls_ssl_ticket_init(mbedtls_ssl_ticket_context *ctx)
37{
38 memset(ctx, 0, sizeof(mbedtls_ssl_ticket_context));
39
40#if defined(MBEDTLS_THREADING_C)
41 mbedtls_mutex_init(&ctx->mutex);
42#endif
43}
44
45#define MAX_KEY_BYTES 32 /* 256 bits */
46
47#define TICKET_KEY_NAME_BYTES 4
48#define TICKET_IV_BYTES 12
49#define TICKET_CRYPT_LEN_BYTES 2
50#define TICKET_AUTH_TAG_BYTES 16
51
52#define TICKET_MIN_LEN (TICKET_KEY_NAME_BYTES + \
53 TICKET_IV_BYTES + \
54 TICKET_CRYPT_LEN_BYTES + \
55 TICKET_AUTH_TAG_BYTES)
56#define TICKET_ADD_DATA_LEN (TICKET_KEY_NAME_BYTES + \
57 TICKET_IV_BYTES + \
58 TICKET_CRYPT_LEN_BYTES)
59
60/*
61 * Generate/update a key
62 */
63MBEDTLS_CHECK_RETURN_CRITICAL
64static int ssl_ticket_gen_key(mbedtls_ssl_ticket_context *ctx,
65 unsigned char index)
66{
67 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
68 unsigned char buf[MAX_KEY_BYTES];
69 mbedtls_ssl_ticket_key *key = ctx->keys + index;
70
71#if defined(MBEDTLS_HAVE_TIME)
72 key->generation_time = (uint32_t) mbedtls_time(NULL);
73#endif
74
75 if ((ret = ctx->f_rng(ctx->p_rng, key->name, sizeof(key->name))) != 0) {
76 return ret;
77 }
78
79 if ((ret = ctx->f_rng(ctx->p_rng, buf, sizeof(buf))) != 0) {
80 return ret;
81 }
82
83 /* With GCM and CCM, same context can encrypt & decrypt */
84 ret = mbedtls_cipher_setkey(&key->ctx, buf,
85 mbedtls_cipher_get_key_bitlen(&key->ctx),
86 MBEDTLS_ENCRYPT);
87
88 mbedtls_platform_zeroize(buf, sizeof(buf));
89
90 return ret;
91}
92
93/*
94 * Rotate/generate keys if necessary
95 */
96MBEDTLS_CHECK_RETURN_CRITICAL
97static int ssl_ticket_update_keys(mbedtls_ssl_ticket_context *ctx)
98{
99#if !defined(MBEDTLS_HAVE_TIME)
100 ((void) ctx);
101#else
102 if (ctx->ticket_lifetime != 0) {
103 uint32_t current_time = (uint32_t) mbedtls_time(NULL);
104 uint32_t key_time = ctx->keys[ctx->active].generation_time;
105
106 if (current_time >= key_time &&
107 current_time - key_time < ctx->ticket_lifetime) {
108 return 0;
109 }
110
111 ctx->active = 1 - ctx->active;
112
113 return ssl_ticket_gen_key(ctx, ctx->active);
114 } else
115#endif /* MBEDTLS_HAVE_TIME */
116 return 0;
117}
118
119/*
120 * Setup context for actual use
121 */
122int mbedtls_ssl_ticket_setup(mbedtls_ssl_ticket_context *ctx,
123 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
124 mbedtls_cipher_type_t cipher,
125 uint32_t lifetime)
126{
127 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
128 const mbedtls_cipher_info_t *cipher_info;
129
130 ctx->f_rng = f_rng;
131 ctx->p_rng = p_rng;
132
133 ctx->ticket_lifetime = lifetime;
134
135 cipher_info = mbedtls_cipher_info_from_type(cipher);
136 if (cipher_info == NULL) {
137 return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
138 }
139
140 if (cipher_info->mode != MBEDTLS_MODE_GCM &&
141 cipher_info->mode != MBEDTLS_MODE_CCM) {
142 return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
143 }
144
145 if (cipher_info->key_bitlen > 8 * MAX_KEY_BYTES) {
146 return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
147 }
148
149 int do_mbedtls_cipher_setup = 1;
150#if defined(MBEDTLS_USE_PSA_CRYPTO)
151 ret = mbedtls_cipher_setup_psa(&ctx->keys[0].ctx,
152 cipher_info, TICKET_AUTH_TAG_BYTES);
153
154 switch (ret) {
155 case 0:
156 do_mbedtls_cipher_setup = 0;
157 break;
158 case MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE:
159 /* We don't yet expect to support all ciphers through PSA,
160 * so allow fallback to ordinary mbedtls_cipher_setup(). */
161 do_mbedtls_cipher_setup = 1;
162 break;
163 default:
164 return ret;
165 }
166#endif /* MBEDTLS_USE_PSA_CRYPTO */
167 if (do_mbedtls_cipher_setup) {
168 if ((ret = mbedtls_cipher_setup(&ctx->keys[0].ctx, cipher_info))
169 != 0) {
170 return ret;
171 }
172 }
173
174 do_mbedtls_cipher_setup = 1;
175#if defined(MBEDTLS_USE_PSA_CRYPTO)
176 do_mbedtls_cipher_setup = 0;
177
178 ret = mbedtls_cipher_setup_psa(&ctx->keys[1].ctx,
179 cipher_info, TICKET_AUTH_TAG_BYTES);
180 if (ret != 0 && ret != MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE) {
181 return ret;
182 }
183 if (ret == MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE) {
184 do_mbedtls_cipher_setup = 1;
185 }
186#endif /* MBEDTLS_USE_PSA_CRYPTO */
187 if (do_mbedtls_cipher_setup) {
188 if ((ret = mbedtls_cipher_setup(&ctx->keys[1].ctx, cipher_info))
189 != 0) {
190 return ret;
191 }
192 }
193
194 if ((ret = ssl_ticket_gen_key(ctx, 0)) != 0 ||
195 (ret = ssl_ticket_gen_key(ctx, 1)) != 0) {
196 return ret;
197 }
198
199 return 0;
200}
201
202/*
203 * Create session ticket, with the following structure:
204 *
205 * struct {
206 * opaque key_name[4];
207 * opaque iv[12];
208 * opaque encrypted_state<0..2^16-1>;
209 * opaque tag[16];
210 * } ticket;
211 *
212 * The key_name, iv, and length of encrypted_state are the additional
213 * authenticated data.
214 */
215
216int mbedtls_ssl_ticket_write(void *p_ticket,
217 const mbedtls_ssl_session *session,
218 unsigned char *start,
219 const unsigned char *end,
220 size_t *tlen,
221 uint32_t *ticket_lifetime)
222{
223 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
224 mbedtls_ssl_ticket_context *ctx = p_ticket;
225 mbedtls_ssl_ticket_key *key;
226 unsigned char *key_name = start;
227 unsigned char *iv = start + TICKET_KEY_NAME_BYTES;
228 unsigned char *state_len_bytes = iv + TICKET_IV_BYTES;
229 unsigned char *state = state_len_bytes + TICKET_CRYPT_LEN_BYTES;
230 size_t clear_len, ciph_len;
231
232 *tlen = 0;
233
234 if (ctx == NULL || ctx->f_rng == NULL) {
235 return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
236 }
237
238 /* We need at least 4 bytes for key_name, 12 for IV, 2 for len 16 for tag,
239 * in addition to session itself, that will be checked when writing it. */
240 MBEDTLS_SSL_CHK_BUF_PTR(start, end, TICKET_MIN_LEN);
241
242#if defined(MBEDTLS_THREADING_C)
243 if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
244 return ret;
245 }
246#endif
247
248 if ((ret = ssl_ticket_update_keys(ctx)) != 0) {
249 goto cleanup;
250 }
251
252 key = &ctx->keys[ctx->active];
253
254 *ticket_lifetime = ctx->ticket_lifetime;
255
256 memcpy(key_name, key->name, TICKET_KEY_NAME_BYTES);
257
258 if ((ret = ctx->f_rng(ctx->p_rng, iv, TICKET_IV_BYTES)) != 0) {
259 goto cleanup;
260 }
261
262 /* Dump session state */
263 if ((ret = mbedtls_ssl_session_save(session,
264 state, end - state,
265 &clear_len)) != 0 ||
266 (unsigned long) clear_len > 65535) {
267 goto cleanup;
268 }
269 MBEDTLS_PUT_UINT16_BE(clear_len, state_len_bytes, 0);
270
271 /* Encrypt and authenticate */
272 if ((ret = mbedtls_cipher_auth_encrypt_ext(&key->ctx,
273 iv, TICKET_IV_BYTES,
274 /* Additional data: key name, IV and length */
275 key_name, TICKET_ADD_DATA_LEN,
276 state, clear_len,
277 state, end - state, &ciph_len,
278 TICKET_AUTH_TAG_BYTES)) != 0) {
279 goto cleanup;
280 }
281 if (ciph_len != clear_len + TICKET_AUTH_TAG_BYTES) {
282 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
283 goto cleanup;
284 }
285
286 *tlen = TICKET_MIN_LEN + ciph_len - TICKET_AUTH_TAG_BYTES;
287
288cleanup:
289#if defined(MBEDTLS_THREADING_C)
290 if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
291 return MBEDTLS_ERR_THREADING_MUTEX_ERROR;
292 }
293#endif
294
295 return ret;
296}
297
298/*
299 * Select key based on name
300 */
301static mbedtls_ssl_ticket_key *ssl_ticket_select_key(
302 mbedtls_ssl_ticket_context *ctx,
303 const unsigned char name[4])
304{
305 unsigned char i;
306
307 for (i = 0; i < sizeof(ctx->keys) / sizeof(*ctx->keys); i++) {
308 if (memcmp(name, ctx->keys[i].name, 4) == 0) {
309 return &ctx->keys[i];
310 }
311 }
312
313 return NULL;
314}
315
316/*
317 * Load session ticket (see mbedtls_ssl_ticket_write for structure)
318 */
319int mbedtls_ssl_ticket_parse(void *p_ticket,
320 mbedtls_ssl_session *session,
321 unsigned char *buf,
322 size_t len)
323{
324 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
325 mbedtls_ssl_ticket_context *ctx = p_ticket;
326 mbedtls_ssl_ticket_key *key;
327 unsigned char *key_name = buf;
328 unsigned char *iv = buf + TICKET_KEY_NAME_BYTES;
329 unsigned char *enc_len_p = iv + TICKET_IV_BYTES;
330 unsigned char *ticket = enc_len_p + TICKET_CRYPT_LEN_BYTES;
331 size_t enc_len, clear_len;
332
333 if (ctx == NULL || ctx->f_rng == NULL) {
334 return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
335 }
336
337 if (len < TICKET_MIN_LEN) {
338 return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
339 }
340
341#if defined(MBEDTLS_THREADING_C)
342 if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) {
343 return ret;
344 }
345#endif
346
347 if ((ret = ssl_ticket_update_keys(ctx)) != 0) {
348 goto cleanup;
349 }
350
351 enc_len = (enc_len_p[0] << 8) | enc_len_p[1];
352
353 if (len != TICKET_MIN_LEN + enc_len) {
354 ret = MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
355 goto cleanup;
356 }
357
358 /* Select key */
359 if ((key = ssl_ticket_select_key(ctx, key_name)) == NULL) {
360 /* We can't know for sure but this is a likely option unless we're
361 * under attack - this is only informative anyway */
362 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
363 goto cleanup;
364 }
365
366 /* Decrypt and authenticate */
367 if ((ret = mbedtls_cipher_auth_decrypt_ext(&key->ctx,
368 iv, TICKET_IV_BYTES,
369 /* Additional data: key name, IV and length */
370 key_name, TICKET_ADD_DATA_LEN,
371 ticket, enc_len + TICKET_AUTH_TAG_BYTES,
372 ticket, enc_len, &clear_len,
373 TICKET_AUTH_TAG_BYTES)) != 0) {
374 if (ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED) {
375 ret = MBEDTLS_ERR_SSL_INVALID_MAC;
376 }
377
378 goto cleanup;
379 }
380 if (clear_len != enc_len) {
381 ret = MBEDTLS_ERR_SSL_INTERNAL_ERROR;
382 goto cleanup;
383 }
384
385 /* Actually load session */
386 if ((ret = mbedtls_ssl_session_load(session, ticket, clear_len)) != 0) {
387 goto cleanup;
388 }
389
390#if defined(MBEDTLS_HAVE_TIME)
391 {
392 /* Check for expiration */
393 mbedtls_time_t current_time = mbedtls_time(NULL);
394
395 if (current_time < session->start ||
396 (uint32_t) (current_time - session->start) > ctx->ticket_lifetime) {
397 ret = MBEDTLS_ERR_SSL_SESSION_TICKET_EXPIRED;
398 goto cleanup;
399 }
400 }
401#endif
402
403cleanup:
404#if defined(MBEDTLS_THREADING_C)
405 if (mbedtls_mutex_unlock(&ctx->mutex) != 0) {
406 return MBEDTLS_ERR_THREADING_MUTEX_ERROR;
407 }
408#endif
409
410 return ret;
411}
412
413/*
414 * Free context
415 */
416void mbedtls_ssl_ticket_free(mbedtls_ssl_ticket_context *ctx)
417{
418 mbedtls_cipher_free(&ctx->keys[0].ctx);
419 mbedtls_cipher_free(&ctx->keys[1].ctx);
420
421#if defined(MBEDTLS_THREADING_C)
422 mbedtls_mutex_free(&ctx->mutex);
423#endif
424
425 mbedtls_platform_zeroize(ctx, sizeof(mbedtls_ssl_ticket_context));
426}
427
428#endif /* MBEDTLS_SSL_TICKET_C */
429