2 * OpenConnect (SSL + DTLS) VPN client
4 * Copyright © 2008-2010 Intel Corporation.
6 * Author: David Woodhouse <dwmw2@infradead.org>
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public License
10 * version 2.1, as published by the Free Software Foundation.
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this library; if not, write to:
20 * Free Software Foundation, Inc.
21 * 51 Franklin Street, Fifth Floor,
22 * Boston, MA 02110-1301 USA
26 #include <sys/types.h>
27 #include <sys/socket.h>
30 #include <netinet/in.h>
31 #include <openssl/err.h>
32 #include <openssl/ssl.h>
36 #include "openconnect.h"
38 #ifdef SSL_F_DTLS1_CONNECT
41 * Useful for catching test cases, where we want everything to be
42 * reproducible. *NEVER* do this in the wild.
44 time_t time(time_t *t)
46 time_t x = 0x3ab2d948;
51 int RAND_pseudo_bytes(char *buf, int len)
53 memset(buf, 0x5a, len);
54 printf("FAKE PSEUDO RANDOM!\n");
58 int RAND_bytes(char *buf, int len)
60 static int foo = 0x5b;
61 printf("FAKE RANDOM!\n");
62 memset(buf, foo, len);
68 * The master-secret is generated randomly by the client. The server
69 * responds with a DTLS Session-ID. These, done over the HTTPS
70 * connection, are enough to 'resume' a DTLS session, bypassing all
71 * the normal setup of a normal DTLS connection.
73 * Cisco use a version of the protocol which predates RFC4347, but
74 * isn't quite the same as the pre-RFC version of the protocol which
75 * was in OpenSSL 0.9.8e -- it includes backports of some later
78 * The openssl/ directory of this source tree should contain both a
79 * small patch against OpenSSL 0.9.8e to make it support Cisco's
80 * snapshot of the protocol, and a larger patch against newer OpenSSL
81 * which gives us an option to use the old protocol again.
83 * Cisco's server also seems to respond to the official version of the
84 * protocol, with a change in the ChangeCipherSpec packet which implies
85 * that it does know the difference and isn't just repeating the version
86 * number seen in the ClientHello. But although I can make the handshake
87 * complete by hacking tls1_mac() to use the _old_ protocol version
88 * number when calculating the MAC, the server still seems to be ignoring
89 * my subsequent data packets. So we use the old protocol, which is what
90 * their clients use anyway.
93 static unsigned char nybble(unsigned char n)
95 if (n >= '0' && n <= '9') return n - '0';
96 else if (n >= 'A' && n <= 'F') return n - ('A' - 10);
97 else if (n >= 'a' && n <= 'f') return n - ('a' - 10);
101 static unsigned char hex(const char *data)
103 return (nybble(data[0]) << 4) | nybble(data[1]);
106 int connect_dtls_socket(struct openconnect_info *vpninfo)
108 STACK_OF(SSL_CIPHER) *ciphers;
109 method_const SSL_METHOD *dtls_method;
110 SSL_CIPHER *dtls_cipher;
115 if (!vpninfo->dtls_cipher) {
116 /* We probably didn't offer it any ciphers it liked */
117 vpninfo->progress(vpninfo, PRG_ERR, "Server offered no DTLS cipher option\n");
118 vpninfo->dtls_attempt_period = 0;
122 if (vpninfo->proxy) {
123 vpninfo->progress(vpninfo, PRG_ERR, "No DTLS when connected via HTTP proxy\n");
124 vpninfo->dtls_attempt_period = 0;
128 dtls_fd = socket(vpninfo->peer_addr->sa_family, SOCK_DGRAM, IPPROTO_UDP);
130 perror("Open UDP socket for DTLS:");
134 if (connect(dtls_fd, vpninfo->peer_addr, vpninfo->peer_addrlen)) {
135 perror("UDP (DTLS) connect:\n");
140 fcntl(dtls_fd, F_SETFD, FD_CLOEXEC);
142 if (!vpninfo->dtls_ctx) {
143 dtls_method = DTLSv1_client_method();
144 vpninfo->dtls_ctx = SSL_CTX_new(dtls_method);
145 if (!vpninfo->dtls_ctx) {
146 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 CTX failed\n");
147 vpninfo->dtls_attempt_period = 0;
151 /* If we don't readahead, then we do short reads and throw
152 away the tail of data packets. */
153 SSL_CTX_set_read_ahead(vpninfo->dtls_ctx, 1);
155 if (!SSL_CTX_set_cipher_list(vpninfo->dtls_ctx, vpninfo->dtls_cipher)) {
156 vpninfo->progress(vpninfo, PRG_ERR, "Set DTLS cipher list failed\n");
157 SSL_CTX_free(vpninfo->dtls_ctx);
158 vpninfo->dtls_ctx = NULL;
159 vpninfo->dtls_attempt_period = 0;
164 if (!vpninfo->dtls_session) {
165 /* We're going to "resume" a session which never existed. Fake it... */
166 vpninfo->dtls_session = SSL_SESSION_new();
167 if (!vpninfo->dtls_session) {
168 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 session failed\n");
169 vpninfo->dtls_attempt_period = 0;
172 vpninfo->dtls_session->ssl_version = 0x0100; // DTLS1_BAD_VER
174 vpninfo->dtls_session->master_key_length = sizeof(vpninfo->dtls_secret);
175 memcpy(vpninfo->dtls_session->master_key, vpninfo->dtls_secret,
176 sizeof(vpninfo->dtls_secret));
178 vpninfo->dtls_session->session_id_length = sizeof(vpninfo->dtls_session_id);
179 memcpy(vpninfo->dtls_session->session_id, vpninfo->dtls_session_id,
180 sizeof(vpninfo->dtls_session_id));
183 dtls_ssl = SSL_new(vpninfo->dtls_ctx);
184 SSL_set_connect_state(dtls_ssl);
186 ciphers = SSL_get_ciphers(dtls_ssl);
187 if (sk_SSL_CIPHER_num(ciphers) != 1) {
188 vpninfo->progress(vpninfo, PRG_ERR, "Not precisely one DTLS cipher\n");
189 SSL_CTX_free(vpninfo->dtls_ctx);
191 SSL_SESSION_free(vpninfo->dtls_session);
192 vpninfo->dtls_ctx = NULL;
193 vpninfo->dtls_session = NULL;
194 vpninfo->dtls_attempt_period = 0;
197 dtls_cipher = sk_SSL_CIPHER_value(ciphers, 0);
199 /* Set the appropriate cipher on our session to be resumed */
200 vpninfo->dtls_session->cipher = dtls_cipher;
201 vpninfo->dtls_session->cipher_id = dtls_cipher->id;
203 /* Add the generated session to the SSL */
204 if (!SSL_set_session(dtls_ssl, vpninfo->dtls_session)) {
205 vpninfo->progress(vpninfo, PRG_ERR,
206 "SSL_set_session() failed with old protocol version 0x%x\n"
207 "Your OpenSSL may lack Cisco compatibility support\n"
208 "See http://rt.openssl.org/Ticket/Display.html?id=1751\n"
209 "Use the --no-dtls command line option to avoid this message\n",
210 vpninfo->dtls_session->ssl_version);
211 vpninfo->dtls_attempt_period = 0;
216 dtls_bio = BIO_new_socket(dtls_fd, BIO_NOCLOSE);
217 SSL_set_bio(dtls_ssl, dtls_bio, dtls_bio);
219 #ifndef SSL_OP_CISCO_ANYCONNECT
220 #warning Your version of OpenSSL does not seem to support Cisco DTLS compatibility
221 #define SSL_OP_CISCO_ANYCONNECT 0x8000
223 SSL_set_options(dtls_ssl, SSL_OP_CISCO_ANYCONNECT);
225 /* Set non-blocking */
226 BIO_set_nbio(SSL_get_rbio(dtls_ssl), 1);
227 BIO_set_nbio(SSL_get_wbio(dtls_ssl), 1);
229 fcntl(dtls_fd, F_SETFL, fcntl(dtls_fd, F_GETFL) | O_NONBLOCK);
231 vpninfo->new_dtls_fd = dtls_fd;
232 vpninfo->new_dtls_ssl = dtls_ssl;
234 if (vpninfo->select_nfds <= dtls_fd)
235 vpninfo->select_nfds = dtls_fd + 1;
237 FD_SET(dtls_fd, &vpninfo->select_rfds);
238 FD_SET(dtls_fd, &vpninfo->select_efds);
240 time(&vpninfo->new_dtls_started);
241 return dtls_try_handshake(vpninfo);
244 int dtls_try_handshake(struct openconnect_info *vpninfo)
246 int ret = SSL_do_handshake(vpninfo->new_dtls_ssl);
249 vpninfo->progress(vpninfo, PRG_INFO, "Established DTLS connection\n");
251 if (vpninfo->dtls_ssl) {
252 /* We are replacing an old connection */
253 SSL_free(vpninfo->dtls_ssl);
254 close(vpninfo->dtls_fd);
255 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
256 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
257 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
259 vpninfo->dtls_ssl = vpninfo->new_dtls_ssl;
260 vpninfo->dtls_fd = vpninfo->new_dtls_fd;
262 vpninfo->new_dtls_ssl = NULL;
263 vpninfo->new_dtls_fd = -1;
265 vpninfo->dtls_times.last_rekey = vpninfo->dtls_times.last_rx =
266 vpninfo->dtls_times.last_tx = time(NULL);
271 ret = SSL_get_error(vpninfo->new_dtls_ssl, ret);
272 if (ret == SSL_ERROR_WANT_WRITE || ret == SSL_ERROR_WANT_READ) {
273 if (time(NULL) < vpninfo->new_dtls_started + 5)
275 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS handshake timed out\n");
278 vpninfo->progress(vpninfo, PRG_ERR, "DTLS handshake failed: %d\n", ret);
279 report_ssl_errors(vpninfo);
281 /* Kill the new (failed) connection... */
282 SSL_free(vpninfo->new_dtls_ssl);
283 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_rfds);
284 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_efds);
285 close(vpninfo->new_dtls_fd);
286 vpninfo->new_dtls_ssl = NULL;
287 vpninfo->new_dtls_fd = -1;
289 /* ... and kill the old one too. The only time there'll be a valid
290 existing session is when it was a rekey, and in that case it's
291 time for the old one to die. */
292 if (vpninfo->dtls_ssl) {
293 SSL_free(vpninfo->dtls_ssl);
294 close(vpninfo->dtls_fd);
295 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
296 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
297 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
298 vpninfo->dtls_ssl = NULL;
299 vpninfo->dtls_fd = -1;
302 time(&vpninfo->new_dtls_started);
306 static int dtls_restart(struct openconnect_info *vpninfo)
308 if (vpninfo->dtls_ssl) {
309 SSL_free(vpninfo->dtls_ssl);
310 close(vpninfo->dtls_fd);
311 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
312 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
313 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
314 vpninfo->dtls_ssl = NULL;
315 vpninfo->dtls_fd = -1;
318 return connect_dtls_socket(vpninfo);
322 int setup_dtls(struct openconnect_info *vpninfo)
324 struct vpn_option *dtls_opt = vpninfo->dtls_options;
325 int sessid_found = 0;
330 vpninfo->progress(vpninfo, PRG_TRACE,
331 "DTLS option %s : %s\n",
332 dtls_opt->option, dtls_opt->value);
334 if (!strcmp(dtls_opt->option, "X-DTLS-Session-ID")) {
335 if (strlen(dtls_opt->value) != 64) {
336 vpninfo->progress(vpninfo, PRG_ERR, "X-DTLS-Session-ID not 64 characters\n");
337 vpninfo->progress(vpninfo, PRG_ERR, "Is: %s\n", dtls_opt->value);
340 for (i = 0; i < 64; i += 2)
341 vpninfo->dtls_session_id[i/2] = hex(dtls_opt->value + i);
343 } else if (!strcmp(dtls_opt->option + 7, "Port")) {
344 dtls_port = atol(dtls_opt->value);
345 } else if (!strcmp(dtls_opt->option + 7, "Keepalive")) {
346 vpninfo->dtls_times.keepalive = atol(dtls_opt->value);
347 } else if (!strcmp(dtls_opt->option + 7, "DPD")) {
348 vpninfo->dtls_times.dpd = atol(dtls_opt->value);
349 } else if (!strcmp(dtls_opt->option + 7, "Rekey-Time")) {
350 vpninfo->dtls_times.rekey = atol(dtls_opt->value);
351 } else if (!strcmp(dtls_opt->option + 7, "CipherSuite")) {
352 vpninfo->dtls_cipher = strdup(dtls_opt->value);
355 dtls_opt = dtls_opt->next;
357 if (!sessid_found || !dtls_port)
360 if (vpninfo->peer_addr->sa_family == AF_INET) {
361 struct sockaddr_in *sin = (void *)vpninfo->peer_addr;
362 sin->sin_port = htons(dtls_port);
363 } else if (vpninfo->peer_addr->sa_family == AF_INET6) {
364 struct sockaddr_in6 *sin = (void *)vpninfo->peer_addr;
365 sin->sin6_port = htons(dtls_port);
367 vpninfo->progress(vpninfo, PRG_ERR, "Unknown protocol family %d. Cannot do DTLS\n",
368 vpninfo->peer_addr->sa_family);
373 if (connect_dtls_socket(vpninfo))
376 vpninfo->progress(vpninfo, PRG_TRACE,
377 "DTLS connected. DPD %d, Keepalive %d\n",
378 vpninfo->dtls_times.dpd, vpninfo->dtls_times.keepalive);
383 int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)
385 unsigned char buf[2000];
390 while ( (len = SSL_read(vpninfo->dtls_ssl, buf, sizeof(buf))) > 0 ) {
392 vpninfo->progress(vpninfo, PRG_TRACE,
393 "Received DTLS packet 0x%02x of %d bytes\n",
396 vpninfo->dtls_times.last_rx = time(NULL);
400 queue_new_packet(&vpninfo->incoming_queue, buf+1, len-1);
405 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD request\n");
407 /* FIXME: What if the packet doesn't get through? */
408 magic_pkt = AC_PKT_DPD_RESP;
409 if (SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1) != 1)
410 vpninfo->progress(vpninfo, PRG_ERR, "Failed to send DPD response. Expect disconnect\n");
413 case AC_PKT_DPD_RESP:
414 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD response\n");
417 case AC_PKT_KEEPALIVE:
418 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS Keepalive\n");
422 vpninfo->progress(vpninfo, PRG_ERR,
423 "Unknown DTLS packet type %02x, len %d\n", buf[0], len);
425 /* Some versions of OpenSSL have bugs with receiving out-of-order
426 * packets. Not only do they wrongly decide to drop packets if
427 * two packets get swapped in transit, but they also _fail_ to
428 * drop the packet in non-blocking mode; instead they return
429 * the appropriate length of garbage. So don't abort... for now. */
432 vpninfo->quit_reason = "Unknown packet received";
439 switch (keepalive_action(&vpninfo->dtls_times, timeout)) {
441 time(&vpninfo->dtls_times.last_rekey);
442 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS rekey due\n");
443 if (connect_dtls_socket(vpninfo)) {
444 vpninfo->progress(vpninfo, PRG_ERR, "DTLS rekey failed\n");
452 vpninfo->progress(vpninfo, PRG_ERR, "DTLS Dead Peer Detection detected dead peer!\n");
453 /* Fall back to SSL, and start a new DTLS connection */
454 dtls_restart(vpninfo);
458 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS DPD\n");
460 magic_pkt = AC_PKT_DPD_OUT;
461 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
462 /* last_dpd will just have been set */
463 vpninfo->dtls_times.last_tx = vpninfo->dtls_times.last_dpd;
468 /* No need to send an explicit keepalive
469 if we have real data to send */
470 if (vpninfo->outgoing_queue)
473 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS Keepalive\n");
475 magic_pkt = AC_PKT_KEEPALIVE;
476 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
477 time(&vpninfo->dtls_times.last_tx);
485 /* Service outgoing packet queue */
486 while (vpninfo->outgoing_queue) {
487 struct pkt *this = vpninfo->outgoing_queue;
490 vpninfo->outgoing_queue = this->next;
491 vpninfo->outgoing_qlen--;
493 /* One byte of header */
494 this->hdr[7] = AC_PKT_DATA;
496 ret = SSL_write(vpninfo->dtls_ssl, &this->hdr[7], this->len + 1);
498 ret = SSL_get_error(vpninfo->dtls_ssl, ret);
500 /* If it's a real error, kill the DTLS connection and
501 requeue the packet to be sent over SSL */
502 if (ret != SSL_ERROR_WANT_READ && ret != SSL_ERROR_WANT_WRITE) {
503 vpninfo->progress(vpninfo, PRG_ERR,
504 "DTLS got write error %d. Falling back to SSL\n", ret);
505 report_ssl_errors(vpninfo);
506 dtls_restart(vpninfo);
507 vpninfo->outgoing_queue = this;
508 vpninfo->outgoing_qlen++;
512 time(&vpninfo->dtls_times.last_tx);
513 vpninfo->progress(vpninfo, PRG_TRACE,
514 "Sent DTLS packet of %d bytes; SSL_write() returned %d\n",
521 #else /* No DTLS support in OpenSSL */
522 int setup_dtls(struct openconnect_info *vpninfo)
524 vpninfo->progress(vpninfo, PRG_ERR, "Built against OpenSSL with no DTLS support\n");