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 <openssl/err.h>
34 #include "openconnect.h"
38 * Useful for catching test cases, where we want everything to be
39 * reproducible. *NEVER* do this in the wild.
41 time_t time(time_t *t)
43 time_t x = 0x3ab2d948;
48 int RAND_pseudo_bytes(char *buf, int len)
50 memset(buf, 0x5a, len);
51 printf("FAKE PSEUDO RANDOM!\n");
55 int RAND_bytes(char *buf, int len)
57 static int foo = 0x5b;
58 printf("FAKE RANDOM!\n");
59 memset(buf, foo, len);
65 * The master-secret is generated randomly by the client. The server
66 * responds with a DTLS Session-ID. These, done over the HTTPS
67 * connection, are enough to 'resume' a DTLS session, bypassing all
68 * the normal setup of a normal DTLS connection.
70 * Cisco use a version of the protocol which predates RFC4347, but
71 * isn't quite the same as the pre-RFC version of the protocol which
72 * was in OpenSSL 0.9.8e -- it includes backports of some later
75 * The openssl/ directory of this source tree should contain both a
76 * small patch against OpenSSL 0.9.8e to make it support Cisco's
77 * snapshot of the protocol, and a larger patch against newer OpenSSL
78 * which gives us an option to use the old protocol again.
80 * Cisco's server also seems to respond to the official version of the
81 * protocol, with a change in the ChangeCipherSpec packet which implies
82 * that it does know the difference and isn't just repeating the version
83 * number seen in the ClientHello. But although I can make the handshake
84 * complete by hacking tls1_mac() to use the _old_ protocol version
85 * number when calculating the MAC, the server still seems to be ignoring
86 * my subsequent data packets. So we use the old protocol, which is what
87 * their clients use anyway.
90 static unsigned char nybble(unsigned char n)
92 if (n >= '0' && n <= '9') return n - '0';
93 else if (n >= 'A' && n <= 'F') return n - ('A' - 10);
94 else if (n >= 'a' && n <= 'f') return n - ('a' - 10);
98 static unsigned char hex(const char *data)
100 return (nybble(data[0]) << 4) | nybble(data[1]);
103 int connect_dtls_socket(struct openconnect_info *vpninfo)
105 SSL_METHOD *dtls_method;
106 SSL_CIPHER *https_cipher;
111 dtls_fd = socket(vpninfo->peer_addr->sa_family, SOCK_DGRAM, IPPROTO_UDP);
113 perror("Open UDP socket for DTLS:");
117 if (connect(dtls_fd, vpninfo->peer_addr, vpninfo->peer_addrlen)) {
118 perror("UDP (DTLS) connect:\n");
123 fcntl(dtls_fd, F_SETFD, FD_CLOEXEC);
125 https_cipher = SSL_get_current_cipher(vpninfo->https_ssl);
127 if (!vpninfo->dtls_ctx) {
128 dtls_method = DTLSv1_client_method();
129 vpninfo->dtls_ctx = SSL_CTX_new(dtls_method);
130 if (!vpninfo->dtls_ctx) {
131 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 CTX failed\n");
135 /* If we don't readahead, then we do short reads and throw
136 away the tail of data packets. */
137 SSL_CTX_set_read_ahead(vpninfo->dtls_ctx, 1);
140 if (!vpninfo->dtls_session) {
141 /* We're going to "resume" a session which never existed. Fake it... */
142 vpninfo->dtls_session = SSL_SESSION_new();
143 if (!vpninfo->dtls_session) {
144 vpninfo->progress(vpninfo, PRG_ERR, "Initialise DTLSv1 session failed\n");
147 vpninfo->dtls_session->ssl_version = 0x0100; // DTLS1_BAD_VER
149 vpninfo->dtls_session->master_key_length = sizeof(vpninfo->dtls_secret);
150 memcpy(vpninfo->dtls_session->master_key, vpninfo->dtls_secret,
151 sizeof(vpninfo->dtls_secret));
153 vpninfo->dtls_session->session_id_length = sizeof(vpninfo->dtls_session_id);
154 memcpy(vpninfo->dtls_session->session_id, vpninfo->dtls_session_id,
155 sizeof(vpninfo->dtls_session_id));
157 vpninfo->dtls_session->cipher = https_cipher;
158 vpninfo->dtls_session->cipher_id = https_cipher->id;
161 dtls_ssl = SSL_new(vpninfo->dtls_ctx);
162 SSL_set_connect_state(dtls_ssl);
163 SSL_set_cipher_list(dtls_ssl, SSL_CIPHER_get_name(https_cipher));
165 /* Add the generated session to the SSL */
166 if (!SSL_set_session(dtls_ssl, vpninfo->dtls_session)) {
167 vpninfo->progress(vpninfo, PRG_ERR,
168 "SSL_set_session() failed with old protocol version 0x%x\n"
169 "Your OpenSSL may lack Cisco compatibility support\n"
170 "See http://rt.openssl.org/Ticket/Display.html?id=1751\n"
171 "Use the --no-dtls command line option to avoid this message\n",
172 vpninfo->dtls_session->ssl_version);
177 dtls_bio = BIO_new_socket(dtls_fd, BIO_NOCLOSE);
178 SSL_set_bio(dtls_ssl, dtls_bio, dtls_bio);
180 #ifndef SSL_OP_CISCO_ANYCONNECT
181 #define SSL_OP_CISCO_ANYCONNECT 0x8000
183 SSL_set_options(dtls_ssl, SSL_OP_CISCO_ANYCONNECT);
185 /* Set non-blocking */
186 BIO_set_nbio(SSL_get_rbio(dtls_ssl),1);
187 BIO_set_nbio(SSL_get_wbio(dtls_ssl),1);
189 fcntl(dtls_fd, F_SETFL, fcntl(dtls_fd, F_GETFL) | O_NONBLOCK);
191 vpninfo->new_dtls_fd = dtls_fd;
192 vpninfo->new_dtls_ssl = dtls_ssl;
194 if (vpninfo->select_nfds <= dtls_fd)
195 vpninfo->select_nfds = dtls_fd + 1;
197 FD_SET(dtls_fd, &vpninfo->select_rfds);
198 FD_SET(dtls_fd, &vpninfo->select_efds);
200 time(&vpninfo->new_dtls_started);
201 return dtls_try_handshake(vpninfo);
204 int dtls_try_handshake(struct openconnect_info *vpninfo)
206 int ret = SSL_do_handshake(vpninfo->new_dtls_ssl);
209 vpninfo->progress(vpninfo, PRG_INFO, "Established DTLS connection\n");
211 if (vpninfo->dtls_ssl) {
212 /* We are replacing an old connection */
213 SSL_free(vpninfo->dtls_ssl);
214 close(vpninfo->dtls_fd);
215 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
216 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
217 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
219 vpninfo->dtls_ssl = vpninfo->new_dtls_ssl;
220 vpninfo->dtls_fd = vpninfo->new_dtls_fd;
222 vpninfo->new_dtls_ssl = NULL;
223 vpninfo->new_dtls_fd = -1;
225 vpninfo->dtls_times.last_rekey = vpninfo->dtls_times.last_rx =
226 vpninfo->dtls_times.last_tx = time(NULL);
231 ret = SSL_get_error(vpninfo->new_dtls_ssl, ret);
232 if (ret == SSL_ERROR_WANT_WRITE || ret == SSL_ERROR_WANT_READ) {
233 if (time(NULL) < vpninfo->new_dtls_started + 5)
235 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS handshake timed out\n");
238 vpninfo->progress(vpninfo, PRG_ERR, "DTLS handshake failed: %d\n", ret);
239 ERR_print_errors_fp(stderr);
241 /* Kill the new (failed) connection... */
242 SSL_free(vpninfo->new_dtls_ssl);
243 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_rfds);
244 FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_efds);
245 close(vpninfo->new_dtls_fd);
246 vpninfo->new_dtls_ssl = NULL;
247 vpninfo->new_dtls_fd = -1;
249 /* ... and kill the old one too. The only time there'll be a valid
250 existing session is when it was a rekey, and in that case it's
251 time for the old one to die. */
252 if (vpninfo->dtls_ssl) {
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);
258 vpninfo->dtls_ssl = NULL;
259 vpninfo->dtls_fd = -1;
262 time(&vpninfo->new_dtls_started);
266 static int dtls_restart(struct openconnect_info *vpninfo)
268 if (vpninfo->dtls_ssl) {
269 SSL_free(vpninfo->dtls_ssl);
270 close(vpninfo->dtls_fd);
271 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);
272 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);
273 FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);
274 vpninfo->dtls_ssl = NULL;
275 vpninfo->dtls_fd = -1;
278 return connect_dtls_socket(vpninfo);
282 int setup_dtls(struct openconnect_info *vpninfo)
284 struct vpn_option *dtls_opt = vpninfo->dtls_options;
285 int sessid_found = 0;
290 vpninfo->progress(vpninfo, PRG_TRACE,
291 "DTLS option %s : %s\n",
292 dtls_opt->option, dtls_opt->value);
294 if (!strcmp(dtls_opt->option, "X-DTLS-Session-ID")) {
295 if (strlen(dtls_opt->value) != 64) {
296 vpninfo->progress(vpninfo, PRG_ERR, "X-DTLS-Session-ID not 64 characters\n");
297 vpninfo->progress(vpninfo, PRG_ERR, "Is: %s\n", dtls_opt->value);
300 for (i = 0; i < 64; i += 2)
301 vpninfo->dtls_session_id[i/2] = hex(dtls_opt->value + i);
303 } else if (!strcmp(dtls_opt->option + 7, "Port")) {
304 dtls_port = atol(dtls_opt->value);
305 } else if (!strcmp(dtls_opt->option + 7, "Keepalive")) {
306 vpninfo->dtls_times.keepalive = atol(dtls_opt->value);
307 } else if (!strcmp(dtls_opt->option + 7, "DPD")) {
308 vpninfo->dtls_times.dpd = atol(dtls_opt->value);
309 } else if (!strcmp(dtls_opt->option + 7, "Rekey-Time")) {
310 vpninfo->dtls_times.rekey = atol(dtls_opt->value);
313 dtls_opt = dtls_opt->next;
315 if (!sessid_found || !dtls_port)
318 if (vpninfo->peer_addr->sa_family == AF_INET) {
319 struct sockaddr_in *sin = (void *)vpninfo->peer_addr;
320 sin->sin_port = htons(dtls_port);
321 } else if (vpninfo->peer_addr->sa_family == AF_INET6) {
322 struct sockaddr_in6 *sin = (void *)vpninfo->peer_addr;
323 sin->sin6_port = htons(dtls_port);
325 vpninfo->progress(vpninfo, PRG_ERR, "Unknown protocol family %d. Cannot do DTLS\n",
326 vpninfo->peer_addr->sa_family);
331 if (connect_dtls_socket(vpninfo))
334 vpninfo->progress(vpninfo, PRG_TRACE,
335 "DTLS connected. DPD %d, Keepalive %d\n",
336 vpninfo->dtls_times.dpd, vpninfo->dtls_times.keepalive);
341 int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)
343 unsigned char buf[2000];
348 while ( (len = SSL_read(vpninfo->dtls_ssl, buf, sizeof(buf))) > 0 ) {
350 vpninfo->progress(vpninfo, PRG_TRACE,
351 "Received DTLS packet 0x%02x of %d bytes\n",
354 vpninfo->dtls_times.last_rx = time(NULL);
358 queue_new_packet(&vpninfo->incoming_queue, AF_INET, buf+1, len-1);
363 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD request\n");
365 /* FIXME: What if the packet doesn't get through? */
366 magic_pkt = AC_PKT_DPD_RESP;
367 if (SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1) != 1)
368 vpninfo->progress(vpninfo, PRG_ERR, "Failed to send DPD response. Expect disconnect\n");
371 case AC_PKT_DPD_RESP:
372 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS DPD response\n");
375 case AC_PKT_KEEPALIVE:
376 vpninfo->progress(vpninfo, PRG_TRACE, "Got DTLS Keepalive\n");
380 vpninfo->progress(vpninfo, PRG_ERR,
381 "Unknown DTLS packet type %02x, len %d\n", buf[0], len);
383 /* Some versions of OpenSSL have bugs with receiving out-of-order
384 * packets. Not only do they wrongly decide to drop packets if
385 * two packets get swapped in transit, but they also _fail_ to
386 * drop the packet in non-blocking mode; instead they return
387 * the appropriate length of garbage. So don't abort... for now. */
390 vpninfo->quit_reason = "Unknown packet received";
397 switch (keepalive_action(&vpninfo->dtls_times, timeout)) {
399 time(&vpninfo->dtls_times.last_rekey);
400 vpninfo->progress(vpninfo, PRG_TRACE, "DTLS rekey due\n");
401 if (connect_dtls_socket(vpninfo)) {
402 vpninfo->progress(vpninfo, PRG_ERR, "DTLS rekey failed\n");
410 vpninfo->progress(vpninfo, PRG_ERR, "DTLS Dead Peer Detection detected dead peer!\n");
411 /* Fall back to SSL, and start a new DTLS connection */
412 dtls_restart(vpninfo);
416 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS DPD\n");
418 magic_pkt = AC_PKT_DPD_OUT;
419 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
420 /* last_dpd will just have been set */
421 vpninfo->dtls_times.last_tx = vpninfo->dtls_times.last_dpd;
426 /* No need to send an explicit keepalive
427 if we have real data to send */
428 if (vpninfo->outgoing_queue)
431 vpninfo->progress(vpninfo, PRG_TRACE, "Send DTLS Keepalive\n");
433 magic_pkt = AC_PKT_KEEPALIVE;
434 SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);
435 time(&vpninfo->dtls_times.last_tx);
443 /* Service outgoing packet queue */
444 while (vpninfo->outgoing_queue) {
445 struct pkt *this = vpninfo->outgoing_queue;
448 vpninfo->outgoing_queue = this->next;
449 vpninfo->outgoing_qlen--;
451 /* One byte of header */
452 this->hdr[7] = AC_PKT_DATA;
454 ret = SSL_write(vpninfo->dtls_ssl, &this->hdr[7], this->len + 1);
456 ret = SSL_get_error(vpninfo->dtls_ssl, ret);
458 /* If it's a real error, kill the DTLS connection and
459 requeue the packet to be sent over SSL */
460 if (ret != SSL_ERROR_WANT_READ && ret != SSL_ERROR_WANT_WRITE) {
461 vpninfo->progress(vpninfo, PRG_ERR,
462 "DTLS got write error %d. Falling back to SSL\n", ret);
463 ERR_print_errors_fp(stderr);
464 dtls_restart(vpninfo);
465 vpninfo->outgoing_queue = this;
466 vpninfo->outgoing_qlen++;
470 time(&vpninfo->dtls_times.last_tx);
471 vpninfo->progress(vpninfo, PRG_TRACE,
472 "Sent DTLS packet of %d bytes; SSL_write() returned %d\n",