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_addr) {
116 vpninfo->progress(vpninfo, PRG_ERR, "No DTLS address\n");
117 vpninfo->dtls_attempt_period = 0;
121 if (!vpninfo->dtls_cipher) {
122 /* We probably didn't offer it any ciphers it liked */
123 vpninfo->progress(vpninfo, PRG_ERR, "Server offered no DTLS cipher option\n");
124 vpninfo->dtls_attempt_period = 0;
128 if (vpninfo->proxy) {
129 /* XXX: Theoretically, SOCKS5 proxies can do UDP too */
130 vpninfo->progress(vpninfo, PRG_ERR, "No DTLS when connected via proxy\n");
131 vpninfo->dtls_attempt_period = 0;
135 dtls_fd = socket(vpninfo->peer_addr->sa_family, SOCK_DGRAM, IPPROTO_UDP);
137 perror("Open UDP socket for DTLS:");
141 if (connect(dtls_fd, vpninfo->dtls_addr, vpninfo->peer_addrlen)) {
142 perror("UDP (DTLS) connect:\n");
147 fcntl(dtls_fd, F_SETFD, FD_CLOEXEC);
149 if (!vpninfo->dtls_ctx) {
150 dtls_method = DTLSv1_client_method();
151 vpninfo->dtls_ctx = SSL_CTX_new(dtls_method);
152 if (!vpninfo->dtls_ctx) {
153 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 CTX failed\n");
154 vpninfo->dtls_attempt_period = 0;
158 /* If we don't readahead, then we do short reads and throw
159 away the tail of data packets. */
160 SSL_CTX_set_read_ahead(vpninfo->dtls_ctx, 1);
162 if (!SSL_CTX_set_cipher_list(vpninfo->dtls_ctx, vpninfo->dtls_cipher)) {
163 vpninfo->progress(vpninfo, PRG_ERR, "Set DTLS cipher list failed\n");
164 SSL_CTX_free(vpninfo->dtls_ctx);
165 vpninfo->dtls_ctx = NULL;
166 vpninfo->dtls_attempt_period = 0;
171 if (!vpninfo->dtls_session) {
172 /* We're going to "resume" a session which never existed. Fake it... */
173 vpninfo->dtls_session = SSL_SESSION_new();
174 if (!vpninfo->dtls_session) {
175 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 session failed\n");
176 vpninfo->dtls_attempt_period = 0;
179 vpninfo->dtls_session->ssl_version = 0x0100; // DTLS1_BAD_VER
181 vpninfo->dtls_session->master_key_length = sizeof(vpninfo->dtls_secret);
182 memcpy(vpninfo->dtls_session->master_key, vpninfo->dtls_secret,
183 sizeof(vpninfo->dtls_secret));
185 vpninfo->dtls_session->session_id_length = sizeof(vpninfo->dtls_session_id);
186 memcpy(vpninfo->dtls_session->session_id, vpninfo->dtls_session_id,
187 sizeof(vpninfo->dtls_session_id));
190 dtls_ssl = SSL_new(vpninfo->dtls_ctx);
191 SSL_set_connect_state(dtls_ssl);
193 ciphers = SSL_get_ciphers(dtls_ssl);
194 if (sk_SSL_CIPHER_num(ciphers) != 1) {
195 vpninfo->progress(vpninfo, PRG_ERR, "Not precisely one DTLS cipher\n");
196 SSL_CTX_free(vpninfo->dtls_ctx);
198 SSL_SESSION_free(vpninfo->dtls_session);
199 vpninfo->dtls_ctx = NULL;
200 vpninfo->dtls_session = NULL;
201 vpninfo->dtls_attempt_period = 0;
204 dtls_cipher = sk_SSL_CIPHER_value(ciphers, 0);
206 /* Set the appropriate cipher on our session to be resumed */
207 vpninfo->dtls_session->cipher = dtls_cipher;
208 vpninfo->dtls_session->cipher_id = dtls_cipher->id;
210 /* Add the generated session to the SSL */
211 if (!SSL_set_session(dtls_ssl, vpninfo->dtls_session)) {
212 vpninfo->progress(vpninfo, PRG_ERR,
213 "SSL_set_session() failed with old protocol version 0x%x\n"
214 "Are you using a version of OpenSSL older than 0.9.8m?\n"
215 "See http://rt.openssl.org/Ticket/Display.html?id=1751\n"
216 "Use the --no-dtls command line option to avoid this message\n",
217 vpninfo->dtls_session->ssl_version);
218 vpninfo->dtls_attempt_period = 0;
223 dtls_bio = BIO_new_socket(dtls_fd, BIO_NOCLOSE);
224 SSL_set_bio(dtls_ssl, dtls_bio, dtls_bio);
226 #ifndef SSL_OP_CISCO_ANYCONNECT
227 #warning Your version of OpenSSL does not seem to support Cisco DTLS compatibility
228 #define SSL_OP_CISCO_ANYCONNECT 0x8000
230 SSL_set_options(dtls_ssl, SSL_OP_CISCO_ANYCONNECT);
232 /* Set non-blocking */
233 BIO_set_nbio(SSL_get_rbio(dtls_ssl), 1);
234 BIO_set_nbio(SSL_get_wbio(dtls_ssl), 1);
236 fcntl(dtls_fd, F_SETFL, fcntl(dtls_fd, F_GETFL) | O_NONBLOCK);
238 vpninfo->new_dtls_fd = dtls_fd;
239 vpninfo->new_dtls_ssl = dtls_ssl;
241 if (vpninfo->select_nfds <= dtls_fd)
242 vpninfo->select_nfds = dtls_fd + 1;
244 FD_SET(dtls_fd, &vpninfo->select_rfds);
245 FD_SET(dtls_fd, &vpninfo->select_efds);
247 time(&vpninfo->new_dtls_started);
248 return dtls_try_handshake(vpninfo);
251 int dtls_try_handshake(struct openconnect_info *vpninfo)
253 int ret = SSL_do_handshake(vpninfo->new_dtls_ssl);
256 vpninfo->progress(vpninfo, PRG_INFO, "Established DTLS connection\n");
258 if (vpninfo->dtls_ssl) {
259 /* We are replacing an old connection */
260 SSL_free(vpninfo->dtls_ssl);
261 close(vpninfo->dtls_fd);
262 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
263 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
264 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
266 vpninfo->dtls_ssl = vpninfo->new_dtls_ssl;
267 vpninfo->dtls_fd = vpninfo->new_dtls_fd;
269 vpninfo->new_dtls_ssl = NULL;
270 vpninfo->new_dtls_fd = -1;
272 vpninfo->dtls_times.last_rekey = vpninfo->dtls_times.last_rx =
273 vpninfo->dtls_times.last_tx = time(NULL);
278 ret = SSL_get_error(vpninfo->new_dtls_ssl, ret);
279 if (ret == SSL_ERROR_WANT_WRITE || ret == SSL_ERROR_WANT_READ) {
280 if (time(NULL) < vpninfo->new_dtls_started + 5)
282 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS handshake timed out\n");
285 vpninfo->progress(vpninfo, PRG_ERR, "DTLS handshake failed: %d\n", ret);
286 report_ssl_errors(vpninfo);
288 /* Kill the new (failed) connection... */
289 SSL_free(vpninfo->new_dtls_ssl);
290 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_rfds);
291 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_efds);
292 close(vpninfo->new_dtls_fd);
293 vpninfo->new_dtls_ssl = NULL;
294 vpninfo->new_dtls_fd = -1;
296 /* ... and kill the old one too. The only time there'll be a valid
297 existing session is when it was a rekey, and in that case it's
298 time for the old one to die. */
299 if (vpninfo->dtls_ssl) {
300 SSL_free(vpninfo->dtls_ssl);
301 close(vpninfo->dtls_fd);
302 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
303 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
304 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
305 vpninfo->dtls_ssl = NULL;
306 vpninfo->dtls_fd = -1;
309 time(&vpninfo->new_dtls_started);
313 static int dtls_restart(struct openconnect_info *vpninfo)
315 if (vpninfo->dtls_ssl) {
316 SSL_free(vpninfo->dtls_ssl);
317 close(vpninfo->dtls_fd);
318 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
319 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
320 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
321 vpninfo->dtls_ssl = NULL;
322 vpninfo->dtls_fd = -1;
325 return connect_dtls_socket(vpninfo);
329 int setup_dtls(struct openconnect_info *vpninfo)
331 struct vpn_option *dtls_opt = vpninfo->dtls_options;
332 int sessid_found = 0;
337 vpninfo->progress(vpninfo, PRG_TRACE,
338 "DTLS option %s : %s\n",
339 dtls_opt->option, dtls_opt->value);
341 if (!strcmp(dtls_opt->option, "X-DTLS-Session-ID")) {
342 if (strlen(dtls_opt->value) != 64) {
343 vpninfo->progress(vpninfo, PRG_ERR, "X-DTLS-Session-ID not 64 characters\n");
344 vpninfo->progress(vpninfo, PRG_ERR, "Is: %s\n", dtls_opt->value);
345 vpninfo->dtls_attempt_period = 0;
348 for (i = 0; i < 64; i += 2)
349 vpninfo->dtls_session_id[i/2] = hex(dtls_opt->value + i);
351 } else if (!strcmp(dtls_opt->option + 7, "Port")) {
352 dtls_port = atol(dtls_opt->value);
353 } else if (!strcmp(dtls_opt->option + 7, "Keepalive")) {
354 vpninfo->dtls_times.keepalive = atol(dtls_opt->value);
355 } else if (!strcmp(dtls_opt->option + 7, "DPD")) {
356 vpninfo->dtls_times.dpd = atol(dtls_opt->value);
357 } else if (!strcmp(dtls_opt->option + 7, "Rekey-Time")) {
358 vpninfo->dtls_times.rekey = atol(dtls_opt->value);
359 } else if (!strcmp(dtls_opt->option + 7, "CipherSuite")) {
360 vpninfo->dtls_cipher = strdup(dtls_opt->value);
363 dtls_opt = dtls_opt->next;
365 if (!sessid_found || !dtls_port) {
366 vpninfo->dtls_attempt_period = 0;
370 vpninfo->dtls_addr = malloc(vpninfo->peer_addrlen);
371 if (!vpninfo->dtls_addr) {
372 vpninfo->dtls_attempt_period = 0;
375 memcpy(vpninfo->dtls_addr, vpninfo->peer_addr, vpninfo->peer_addrlen);
377 if (vpninfo->peer_addr->sa_family == AF_INET) {
378 struct sockaddr_in *sin = (void *)vpninfo->dtls_addr;
379 sin->sin_port = htons(dtls_port);
380 } else if (vpninfo->peer_addr->sa_family == AF_INET6) {
381 struct sockaddr_in6 *sin = (void *)vpninfo->dtls_addr;
382 sin->sin6_port = htons(dtls_port);
384 vpninfo->progress(vpninfo, PRG_ERR, "Unknown protocol family %d. Cannot do DTLS\n",
385 vpninfo->peer_addr->sa_family);
386 vpninfo->dtls_attempt_period = 0;
390 if (connect_dtls_socket(vpninfo))
393 vpninfo->progress(vpninfo, PRG_TRACE,
394 "DTLS connected. DPD %d, Keepalive %d\n",
395 vpninfo->dtls_times.dpd, vpninfo->dtls_times.keepalive);
400 int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)
402 unsigned char buf[2000];
407 while ( (len = SSL_read(vpninfo->dtls_ssl, buf, sizeof(buf))) > 0 ) {
409 vpninfo->progress(vpninfo, PRG_TRACE,
410 "Received DTLS packet 0x%02x of %d bytes\n",
413 vpninfo->dtls_times.last_rx = time(NULL);
417 queue_new_packet(&vpninfo->incoming_queue, buf+1, len-1);
422 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD request\n");
424 /* FIXME: What if the packet doesn't get through? */
425 magic_pkt = AC_PKT_DPD_RESP;
426 if (SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1) != 1)
427 vpninfo->progress(vpninfo, PRG_ERR, "Failed to send DPD response. Expect disconnect\n");
430 case AC_PKT_DPD_RESP:
431 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD response\n");
434 case AC_PKT_KEEPALIVE:
435 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS Keepalive\n");
439 vpninfo->progress(vpninfo, PRG_ERR,
440 "Unknown DTLS packet type %02x, len %d\n", buf[0], len);
442 /* Some versions of OpenSSL have bugs with receiving out-of-order
443 * packets. Not only do they wrongly decide to drop packets if
444 * two packets get swapped in transit, but they also _fail_ to
445 * drop the packet in non-blocking mode; instead they return
446 * the appropriate length of garbage. So don't abort... for now. */
449 vpninfo->quit_reason = "Unknown packet received";
456 switch (keepalive_action(&vpninfo->dtls_times, timeout)) {
458 time(&vpninfo->dtls_times.last_rekey);
459 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS rekey due\n");
460 if (connect_dtls_socket(vpninfo)) {
461 vpninfo->progress(vpninfo, PRG_ERR, "DTLS rekey failed\n");
469 vpninfo->progress(vpninfo, PRG_ERR, "DTLS Dead Peer Detection detected dead peer!\n");
470 /* Fall back to SSL, and start a new DTLS connection */
471 dtls_restart(vpninfo);
475 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS DPD\n");
477 magic_pkt = AC_PKT_DPD_OUT;
478 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
479 /* last_dpd will just have been set */
480 vpninfo->dtls_times.last_tx = vpninfo->dtls_times.last_dpd;
485 /* No need to send an explicit keepalive
486 if we have real data to send */
487 if (vpninfo->outgoing_queue)
490 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS Keepalive\n");
492 magic_pkt = AC_PKT_KEEPALIVE;
493 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
494 time(&vpninfo->dtls_times.last_tx);
502 /* Service outgoing packet queue */
503 while (vpninfo->outgoing_queue) {
504 struct pkt *this = vpninfo->outgoing_queue;
507 vpninfo->outgoing_queue = this->next;
508 vpninfo->outgoing_qlen--;
510 /* One byte of header */
511 this->hdr[7] = AC_PKT_DATA;
513 ret = SSL_write(vpninfo->dtls_ssl, &this->hdr[7], this->len + 1);
515 ret = SSL_get_error(vpninfo->dtls_ssl, ret);
517 /* If it's a real error, kill the DTLS connection and
518 requeue the packet to be sent over SSL */
519 if (ret != SSL_ERROR_WANT_READ && ret != SSL_ERROR_WANT_WRITE) {
520 vpninfo->progress(vpninfo, PRG_ERR,
521 "DTLS got write error %d. Falling back to SSL\n", ret);
522 report_ssl_errors(vpninfo);
523 dtls_restart(vpninfo);
524 vpninfo->outgoing_queue = this;
525 vpninfo->outgoing_qlen++;
529 time(&vpninfo->dtls_times.last_tx);
530 vpninfo->progress(vpninfo, PRG_TRACE,
531 "Sent DTLS packet of %d bytes; SSL_write() returned %d\n",
538 #else /* No DTLS support in OpenSSL */
539 int setup_dtls(struct openconnect_info *vpninfo)
541 vpninfo->progress(vpninfo, PRG_ERR, "Built against OpenSSL with no DTLS support\n");