2 * OpenConnect (SSL + DTLS) VPN client
4 * Copyright © 2008 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>
35 #include "openconnect.h"
39 * Useful for catching test cases, where we want everything to be
40 * reproducible. *NEVER* do this in the wild.
42 time_t time(time_t *t)
44 time_t x = 0x3ab2d948;
49 int RAND_pseudo_bytes(char *buf, int len)
51 memset(buf, 0x5a, len);
52 printf("FAKE PSEUDO RANDOM!\n");
56 int RAND_bytes(char *buf, int len)
58 static int foo = 0x5b;
59 printf("FAKE RANDOM!\n");
60 memset(buf, foo, len);
66 * The master-secret is generated randomly by the client. The server
67 * responds with a DTLS Session-ID. These, done over the HTTPS
68 * connection, are enough to 'resume' a DTLS session, bypassing all
69 * the normal setup of a normal DTLS connection.
71 * Cisco use a version of the protocol which predates RFC4347, but
72 * isn't quite the same as the pre-RFC version of the protocol which
73 * was in OpenSSL 0.9.8e -- it includes backports of some later
76 * The openssl/ directory of this source tree should contain both a
77 * small patch against OpenSSL 0.9.8e to make it support Cisco's
78 * snapshot of the protocol, and a larger patch against newer OpenSSL
79 * which gives us an option to use the old protocol again.
81 * Cisco's server also seems to respond to the official version of the
82 * protocol, with a change in the ChangeCipherSpec packet which implies
83 * that it does know the difference and isn't just repeating the version
84 * number seen in the ClientHello. But although I can make the handshake
85 * complete by hacking tls1_mac() to use the _old_ protocol version
86 * number when calculating the MAC, the server still seems to be ignoring
87 * my subsequent data packets. So we use the old protocol, which is what
88 * their clients use anyway.
91 static unsigned char nybble(unsigned char n)
93 if (n >= '0' && n <= '9') return n - '0';
94 else if (n >= 'A' && n <= 'F') return n - ('A' - 10);
95 else if (n >= 'a' && n <= 'f') return n - ('a' - 10);
99 static unsigned char hex(const char *data)
101 return (nybble(data[0]) << 4) | nybble(data[1]);
104 int connect_dtls_socket(struct openconnect_info *vpninfo)
106 SSL_METHOD *dtls_method;
107 SSL_CIPHER *https_cipher;
112 dtls_fd = socket(vpninfo->peer_addr->sa_family, SOCK_DGRAM, IPPROTO_UDP);
114 perror("Open UDP socket for DTLS:");
118 if (connect(dtls_fd, vpninfo->peer_addr, vpninfo->peer_addrlen)) {
119 perror("UDP (DTLS) connect:\n");
124 fcntl(dtls_fd, F_SETFD, FD_CLOEXEC);
126 https_cipher = SSL_get_current_cipher(vpninfo->https_ssl);
128 if (!vpninfo->dtls_ctx) {
129 dtls_method = DTLSv1_client_method();
130 vpninfo->dtls_ctx = SSL_CTX_new(dtls_method);
131 if (!vpninfo->dtls_ctx) {
132 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 CTX failed\n");
136 /* If we don't readahead, then we do short reads and throw
137 away the tail of data packets. */
138 SSL_CTX_set_read_ahead(vpninfo->dtls_ctx, 1);
141 if (!vpninfo->dtls_session) {
142 /* We're going to "resume" a session which never existed. Fake it... */
143 vpninfo->dtls_session = SSL_SESSION_new();
144 if (!vpninfo->dtls_session) {
145 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 session failed\n");
148 vpninfo->dtls_session->ssl_version = 0x0100; // DTLS1_BAD_VER
150 vpninfo->dtls_session->master_key_length = sizeof(vpninfo->dtls_secret);
151 memcpy(vpninfo->dtls_session->master_key, vpninfo->dtls_secret,
152 sizeof(vpninfo->dtls_secret));
154 vpninfo->dtls_session->session_id_length = sizeof(vpninfo->dtls_session_id);
155 memcpy(vpninfo->dtls_session->session_id, vpninfo->dtls_session_id,
156 sizeof(vpninfo->dtls_session_id));
158 vpninfo->dtls_session->cipher = https_cipher;
159 vpninfo->dtls_session->cipher_id = https_cipher->id;
162 dtls_ssl = SSL_new(vpninfo->dtls_ctx);
163 SSL_set_connect_state(dtls_ssl);
164 SSL_set_cipher_list(dtls_ssl, SSL_CIPHER_get_name(https_cipher));
166 /* Add the generated session to the SSL */
167 if (!SSL_set_session(dtls_ssl, vpninfo->dtls_session)) {
168 vpninfo->progress(vpninfo, PRG_ERR,
169 "SSL_set_session() failed with old protocol version 0x%x\n"
170 "Your OpenSSL may lack Cisco compatibility support\n"
171 "See http://rt.openssl.org/Ticket/Display.html?id=1751\n"
172 "Use the --no-dtls command line option to avoid this message\n",
173 vpninfo->dtls_session->ssl_version);
174 vpninfo->dtls_attempt_period = 0;
179 dtls_bio = BIO_new_socket(dtls_fd, BIO_NOCLOSE);
180 SSL_set_bio(dtls_ssl, dtls_bio, dtls_bio);
182 #ifndef SSL_OP_CISCO_ANYCONNECT
183 #define SSL_OP_CISCO_ANYCONNECT 0x8000
185 SSL_set_options(dtls_ssl, SSL_OP_CISCO_ANYCONNECT);
187 /* Set non-blocking */
188 BIO_set_nbio(SSL_get_rbio(dtls_ssl),1);
189 BIO_set_nbio(SSL_get_wbio(dtls_ssl),1);
191 fcntl(dtls_fd, F_SETFL, fcntl(dtls_fd, F_GETFL) | O_NONBLOCK);
193 vpninfo->new_dtls_fd = dtls_fd;
194 vpninfo->new_dtls_ssl = dtls_ssl;
196 if (vpninfo->select_nfds <= dtls_fd)
197 vpninfo->select_nfds = dtls_fd + 1;
199 FD_SET(dtls_fd, &vpninfo->select_rfds);
200 FD_SET(dtls_fd, &vpninfo->select_efds);
202 time(&vpninfo->new_dtls_started);
203 return dtls_try_handshake(vpninfo);
206 int dtls_try_handshake(struct openconnect_info *vpninfo)
208 int ret = SSL_do_handshake(vpninfo->new_dtls_ssl);
211 vpninfo->progress(vpninfo, PRG_INFO, "Established DTLS connection\n");
213 if (vpninfo->dtls_ssl) {
214 /* We are replacing an old connection */
215 SSL_free(vpninfo->dtls_ssl);
216 close(vpninfo->dtls_fd);
217 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
218 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
219 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
221 vpninfo->dtls_ssl = vpninfo->new_dtls_ssl;
222 vpninfo->dtls_fd = vpninfo->new_dtls_fd;
224 vpninfo->new_dtls_ssl = NULL;
225 vpninfo->new_dtls_fd = -1;
227 vpninfo->dtls_times.last_rekey = vpninfo->dtls_times.last_rx =
228 vpninfo->dtls_times.last_tx = time(NULL);
233 ret = SSL_get_error(vpninfo->new_dtls_ssl, ret);
234 if (ret == SSL_ERROR_WANT_WRITE || ret == SSL_ERROR_WANT_READ) {
235 if (time(NULL) < vpninfo->new_dtls_started + 5)
237 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS handshake timed out\n");
240 vpninfo->progress(vpninfo, PRG_ERR, "DTLS handshake failed: %d\n", ret);
241 ERR_print_errors_fp(stderr);
243 /* Kill the new (failed) connection... */
244 SSL_free(vpninfo->new_dtls_ssl);
245 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_rfds);
246 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_efds);
247 close(vpninfo->new_dtls_fd);
248 vpninfo->new_dtls_ssl = NULL;
249 vpninfo->new_dtls_fd = -1;
251 /* ... and kill the old one too. The only time there'll be a valid
252 existing session is when it was a rekey, and in that case it's
253 time for the old one to die. */
254 if (vpninfo->dtls_ssl) {
255 SSL_free(vpninfo->dtls_ssl);
256 close(vpninfo->dtls_fd);
257 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
258 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
259 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
260 vpninfo->dtls_ssl = NULL;
261 vpninfo->dtls_fd = -1;
264 time(&vpninfo->new_dtls_started);
268 static int dtls_restart(struct openconnect_info *vpninfo)
270 if (vpninfo->dtls_ssl) {
271 SSL_free(vpninfo->dtls_ssl);
272 close(vpninfo->dtls_fd);
273 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
274 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
275 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
276 vpninfo->dtls_ssl = NULL;
277 vpninfo->dtls_fd = -1;
280 return connect_dtls_socket(vpninfo);
284 int setup_dtls(struct openconnect_info *vpninfo)
286 struct vpn_option *dtls_opt = vpninfo->dtls_options;
287 int sessid_found = 0;
292 vpninfo->progress(vpninfo, PRG_TRACE,
293 "DTLS option %s : %s\n",
294 dtls_opt->option, dtls_opt->value);
296 if (!strcmp(dtls_opt->option, "X-DTLS-Session-ID")) {
297 if (strlen(dtls_opt->value) != 64) {
298 vpninfo->progress(vpninfo, PRG_ERR, "X-DTLS-Session-ID not 64 characters\n");
299 vpninfo->progress(vpninfo, PRG_ERR, "Is: %s\n", dtls_opt->value);
302 for (i = 0; i < 64; i += 2)
303 vpninfo->dtls_session_id[i/2] = hex(dtls_opt->value + i);
305 } else if (!strcmp(dtls_opt->option + 7, "Port")) {
306 dtls_port = atol(dtls_opt->value);
307 } else if (!strcmp(dtls_opt->option + 7, "Keepalive")) {
308 vpninfo->dtls_times.keepalive = atol(dtls_opt->value);
309 } else if (!strcmp(dtls_opt->option + 7, "DPD")) {
310 vpninfo->dtls_times.dpd = atol(dtls_opt->value);
311 } else if (!strcmp(dtls_opt->option + 7, "Rekey-Time")) {
312 vpninfo->dtls_times.rekey = atol(dtls_opt->value);
315 dtls_opt = dtls_opt->next;
317 if (!sessid_found || !dtls_port)
320 if (vpninfo->peer_addr->sa_family == AF_INET) {
321 struct sockaddr_in *sin = (void *)vpninfo->peer_addr;
322 sin->sin_port = htons(dtls_port);
323 } else if (vpninfo->peer_addr->sa_family == AF_INET6) {
324 struct sockaddr_in6 *sin = (void *)vpninfo->peer_addr;
325 sin->sin6_port = htons(dtls_port);
327 vpninfo->progress(vpninfo, PRG_ERR, "Unknown protocol family %d. Cannot do DTLS\n",
328 vpninfo->peer_addr->sa_family);
333 if (connect_dtls_socket(vpninfo))
336 vpninfo->progress(vpninfo, PRG_TRACE,
337 "DTLS connected. DPD %d, Keepalive %d\n",
338 vpninfo->dtls_times.dpd, vpninfo->dtls_times.keepalive);
343 int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)
345 unsigned char buf[2000];
350 while ( (len = SSL_read(vpninfo->dtls_ssl, buf, sizeof(buf))) > 0 ) {
352 vpninfo->progress(vpninfo, PRG_TRACE,
353 "Received DTLS packet 0x%02x of %d bytes\n",
356 vpninfo->dtls_times.last_rx = time(NULL);
360 queue_new_packet(&vpninfo->incoming_queue, AF_INET, buf+1, len-1);
365 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD request\n");
367 /* FIXME: What if the packet doesn't get through? */
368 magic_pkt = AC_PKT_DPD_RESP;
369 if (SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1) != 1)
370 vpninfo->progress(vpninfo, PRG_ERR, "Failed to send DPD response. Expect disconnect\n");
373 case AC_PKT_DPD_RESP:
374 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD response\n");
377 case AC_PKT_KEEPALIVE:
378 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS Keepalive\n");
382 vpninfo->progress(vpninfo, PRG_ERR,
383 "Unknown DTLS packet type %02x, len %d\n", buf[0], len);
385 /* Some versions of OpenSSL have bugs with receiving out-of-order
386 * packets. Not only do they wrongly decide to drop packets if
387 * two packets get swapped in transit, but they also _fail_ to
388 * drop the packet in non-blocking mode; instead they return
389 * the appropriate length of garbage. So don't abort... for now. */
392 vpninfo->quit_reason = "Unknown packet received";
399 switch (keepalive_action(&vpninfo->dtls_times, timeout)) {
401 time(&vpninfo->dtls_times.last_rekey);
402 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS rekey due\n");
403 if (connect_dtls_socket(vpninfo)) {
404 vpninfo->progress(vpninfo, PRG_ERR, "DTLS rekey failed\n");
412 vpninfo->progress(vpninfo, PRG_ERR, "DTLS Dead Peer Detection detected dead peer!\n");
413 /* Fall back to SSL, and start a new DTLS connection */
414 dtls_restart(vpninfo);
418 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS DPD\n");
420 magic_pkt = AC_PKT_DPD_OUT;
421 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
422 /* last_dpd will just have been set */
423 vpninfo->dtls_times.last_tx = vpninfo->dtls_times.last_dpd;
428 /* No need to send an explicit keepalive
429 if we have real data to send */
430 if (vpninfo->outgoing_queue)
433 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS Keepalive\n");
435 magic_pkt = AC_PKT_KEEPALIVE;
436 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
437 time(&vpninfo->dtls_times.last_tx);
445 /* Service outgoing packet queue */
446 while (vpninfo->outgoing_queue) {
447 struct pkt *this = vpninfo->outgoing_queue;
450 vpninfo->outgoing_queue = this->next;
451 vpninfo->outgoing_qlen--;
453 /* One byte of header */
454 this->hdr[7] = AC_PKT_DATA;
456 ret = SSL_write(vpninfo->dtls_ssl, &this->hdr[7], this->len + 1);
458 ret = SSL_get_error(vpninfo->dtls_ssl, ret);
460 /* If it's a real error, kill the DTLS connection and
461 requeue the packet to be sent over SSL */
462 if (ret != SSL_ERROR_WANT_READ && ret != SSL_ERROR_WANT_WRITE) {
463 vpninfo->progress(vpninfo, PRG_ERR,
464 "DTLS got write error %d. Falling back to SSL\n", ret);
465 ERR_print_errors_fp(stderr);
466 dtls_restart(vpninfo);
467 vpninfo->outgoing_queue = this;
468 vpninfo->outgoing_qlen++;
472 time(&vpninfo->dtls_times.last_tx);
473 vpninfo->progress(vpninfo, PRG_TRACE,
474 "Sent DTLS packet of %d bytes; SSL_write() returned %d\n",