/*

* OpenConnect (SSL + DTLS) VPN client

*

* Copyright © 2008-2010 Intel Corporation.

*

* Author: David Woodhouse <dwmw2@infradead.org>

*

* This program is free software; you can redistribute it and/or

* modify it under the terms of the GNU Lesser General Public License

* version 2.1, as published by the Free Software Foundation.

*

* This program is distributed in the hope that it will be useful, but

* WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

* Lesser General Public License for more details.

*

* You should have received a copy of the GNU Lesser General Public

* License along with this library; if not, write to:

*

* Free Software Foundation, Inc.

* 51 Franklin Street, Fifth Floor,

* Boston, MA 02110-1301 USA

*/

#include <errno.h>

#include <sys/types.h>

#include <sys/socket.h>

#include <netdb.h>

#include <unistd.h>

#include <netinet/in.h>

#include <openssl/err.h>

#include <openssl/ssl.h>

#include <fcntl.h>

#include <string.h>

#include "openconnect-internal.h"

#ifdef HAVE_DTLS1_STOP_TIMER

/* OpenSSL doesn't deliberately export this, but we need it to

workaround a DTLS bug in versions < 1.0.0e */

extern void dtls1_stop_timer (SSL *);

#endif

static unsigned char nybble(unsigned char n)

{

if (n >= '0' && n <= '9') return n - '0';

else if (n >= 'A' && n <= 'F') return n - ('A' - 10);

else if (n >= 'a' && n <= 'f') return n - ('a' - 10);

return 0;

}

unsigned char unhex(const char *data)

{

return (nybble(data[0]) << 4) | nybble(data[1]);

}

#ifdef SSL_OP_CISCO_ANYCONNECT

#if 0

/*

* Useful for catching test cases, where we want everything to be

* reproducible. *NEVER* do this in the wild.

*/

time_t time(time_t *t)

{

time_t x = 0x3ab2d948;

if (t) *t = x;

return x;

}

int RAND_pseudo_bytes(char *buf, int len)

{

memset(buf, 0x5a, len);

printf("FAKE PSEUDO RANDOM!\n");

return 1;

}

int RAND_bytes(char *buf, int len)

{

static int foo = 0x5b;

printf("FAKE RANDOM!\n");

memset(buf, foo, len);

return 1;

}

#endif

/*

* The master-secret is generated randomly by the client. The server

* responds with a DTLS Session-ID. These, done over the HTTPS

* connection, are enough to 'resume' a DTLS session, bypassing all

* the normal setup of a normal DTLS connection.

*

* Cisco use a version of the protocol which predates RFC4347, but

* isn't quite the same as the pre-RFC version of the protocol which

* was in OpenSSL 0.9.8e -- it includes backports of some later

* OpenSSL patches.

*

* The openssl/ directory of this source tree should contain both a

* small patch against OpenSSL 0.9.8e to make it support Cisco's

* snapshot of the protocol, and a larger patch against newer OpenSSL

* which gives us an option to use the old protocol again.

*

* Cisco's server also seems to respond to the official version of the

* protocol, with a change in the ChangeCipherSpec packet which implies

* that it does know the difference and isn't just repeating the version

* number seen in the ClientHello. But although I can make the handshake

* complete by hacking tls1_mac() to use the _old_ protocol version

* number when calculating the MAC, the server still seems to be ignoring

* my subsequent data packets. So we use the old protocol, which is what

* their clients use anyway.

*/

int connect_dtls_socket(struct openconnect_info *vpninfo)

{

STACK_OF(SSL_CIPHER) *ciphers;

method_const SSL_METHOD *dtls_method;

SSL_CIPHER *dtls_cipher;

SSL *dtls_ssl;

BIO *dtls_bio;

int dtls_fd;

if (!vpninfo->dtls_addr) {

vpn_progress(vpninfo, PRG_ERR, _("No DTLS address\n"));

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

if (!vpninfo->dtls_cipher) {

/* We probably didn't offer it any ciphers it liked */

vpn_progress(vpninfo, PRG_ERR, _("Server offered no DTLS cipher option\n"));

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

if (vpninfo->proxy) {

/* XXX: Theoretically, SOCKS5 proxies can do UDP too */

vpn_progress(vpninfo, PRG_ERR, _("No DTLS when connected via proxy\n"));

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

dtls_fd = socket(vpninfo->peer_addr->sa_family, SOCK_DGRAM, IPPROTO_UDP);

if (dtls_fd < 0) {

perror(_("Open UDP socket for DTLS:"));

return -EINVAL;

}

if (connect(dtls_fd, vpninfo->dtls_addr, vpninfo->peer_addrlen)) {

perror(_("UDP (DTLS) connect:\n"));

close(dtls_fd);

return -EINVAL;

}

fcntl(dtls_fd, F_SETFD, FD_CLOEXEC);

if (!vpninfo->dtls_ctx) {

dtls_method = DTLSv1_client_method();

vpninfo->dtls_ctx = SSL_CTX_new(dtls_method);

if (!vpninfo->dtls_ctx) {

vpn_progress(vpninfo, PRG_ERR,

_("Initialise DTLSv1 CTX failed\n"));

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

/* If we don't readahead, then we do short reads and throw

away the tail of data packets. */

SSL_CTX_set_read_ahead(vpninfo->dtls_ctx, 1);

if (!SSL_CTX_set_cipher_list(vpninfo->dtls_ctx, vpninfo->dtls_cipher)) {

vpn_progress(vpninfo, PRG_ERR,

_("Set DTLS cipher list failed\n"));

SSL_CTX_free(vpninfo->dtls_ctx);

vpninfo->dtls_ctx = NULL;

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

}

if (!vpninfo->dtls_session) {

/* We're going to "resume" a session which never existed. Fake it... */

vpninfo->dtls_session = SSL_SESSION_new();

if (!vpninfo->dtls_session) {

vpn_progress(vpninfo, PRG_ERR,

_("Initialise DTLSv1 session failed\n"));

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

vpninfo->dtls_session->ssl_version = 0x0100; /* DTLS1_BAD_VER */

}

/* Do this every time; it may have changed due to a rekey */

vpninfo->dtls_session->master_key_length = sizeof(vpninfo->dtls_secret);

memcpy(vpninfo->dtls_session->master_key, vpninfo->dtls_secret,

sizeof(vpninfo->dtls_secret));

vpninfo->dtls_session->session_id_length = sizeof(vpninfo->dtls_session_id);

memcpy(vpninfo->dtls_session->session_id, vpninfo->dtls_session_id,

sizeof(vpninfo->dtls_session_id));

dtls_ssl = SSL_new(vpninfo->dtls_ctx);

SSL_set_connect_state(dtls_ssl);

ciphers = SSL_get_ciphers(dtls_ssl);

if (sk_SSL_CIPHER_num(ciphers) != 1) {

vpn_progress(vpninfo, PRG_ERR, _("Not precisely one DTLS cipher\n"));

SSL_CTX_free(vpninfo->dtls_ctx);

SSL_free(dtls_ssl);

SSL_SESSION_free(vpninfo->dtls_session);

vpninfo->dtls_ctx = NULL;

vpninfo->dtls_session = NULL;

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

dtls_cipher = sk_SSL_CIPHER_value(ciphers, 0);

/* Set the appropriate cipher on our session to be resumed */

vpninfo->dtls_session->cipher = dtls_cipher;

vpninfo->dtls_session->cipher_id = dtls_cipher->id;

/* Add the generated session to the SSL */

if (!SSL_set_session(dtls_ssl, vpninfo->dtls_session)) {

vpn_progress(vpninfo, PRG_ERR,

_("SSL_set_session() failed with old protocol version 0x%x\n"

"Are you using a version of OpenSSL older than 0.9.8m?\n"

"See http://rt.openssl.org/Ticket/Display.html?id=1751\n"

"Use the --no-dtls command line option to avoid this message\n"),

vpninfo->dtls_session->ssl_version);

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

/* Go Go Go! */

dtls_bio = BIO_new_socket(dtls_fd, BIO_NOCLOSE);

SSL_set_bio(dtls_ssl, dtls_bio, dtls_bio);

SSL_set_options(dtls_ssl, SSL_OP_CISCO_ANYCONNECT);

/* Set non-blocking */

BIO_set_nbio(SSL_get_rbio(dtls_ssl), 1);

BIO_set_nbio(SSL_get_wbio(dtls_ssl), 1);

fcntl(dtls_fd, F_SETFL, fcntl(dtls_fd, F_GETFL) | O_NONBLOCK);

vpninfo->new_dtls_fd = dtls_fd;

vpninfo->new_dtls_ssl = dtls_ssl;

if (vpninfo->select_nfds <= dtls_fd)

vpninfo->select_nfds = dtls_fd + 1;

FD_SET(dtls_fd, &vpninfo->select_rfds);

FD_SET(dtls_fd, &vpninfo->select_efds);

time(&vpninfo->new_dtls_started);

return dtls_try_handshake(vpninfo);

}

int dtls_try_handshake(struct openconnect_info *vpninfo)

{

int ret = SSL_do_handshake(vpninfo->new_dtls_ssl);

if (ret == 1) {

vpn_progress(vpninfo, PRG_INFO, _("Established DTLS connection\n"));

if (vpninfo->dtls_ssl) {

/* We are replacing an old connection */

SSL_free(vpninfo->dtls_ssl);

close(vpninfo->dtls_fd);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);

}

vpninfo->dtls_ssl = vpninfo->new_dtls_ssl;

vpninfo->dtls_fd = vpninfo->new_dtls_fd;

vpninfo->new_dtls_ssl = NULL;

vpninfo->new_dtls_fd = -1;

vpninfo->dtls_times.last_rx = vpninfo->dtls_times.last_tx = time(NULL);

/* From about 8.4.1(11) onwards, the ASA seems to get

very unhappy if we resend ChangeCipherSpec messages

after the initial setup. This was "fixed" in OpenSSL

1.0.0e for RT#2505, but it's not clear if that was

the right fix. What happens if the original packet

*does* get lost? Surely we *wanted* the retransmits,

because without them the server will never be able

to decrypt anything we send?

Oh well, our retransmitted packets upset the server

because we don't get the Cisco-compatibility right

(this is one of the areas in which Cisco's DTLS differs

from the RFC4347 spec), and DPD should help us notice

if *nothing* is getting through. */

#if OPENSSL_VERSION_NUMBER >= 0x1000005fL

/* OpenSSL 1.0.0e or above doesn't resend anyway; do nothing.

However, if we were *built* against 1.0.0e or newer, but at

runtime we find that we are being run against an older

version, warn about it. */

if (SSLeay() < 0x1000005fL) {

vpn_progress(vpninfo, PRG_ERR,

_("Your OpenSSL is older than the one you built against, so DTLS may fail!"));

}

#elif defined (HAVE_DTLS1_STOP_TIMER)

dtls1_stop_timer(vpninfo->dtls_ssl);

#else

/* Debian restricts visibility of dtls1_stop_timer()

so do it manually. Thankfully this *should* work,

from 0.9.8m to 1.0.0d inclusive, and we don't have

to worry about future changes because we don't do

this for 1.0.0e and above anyway */

memset (&(vpninfo->dtls_ssl->d1->next_timeout), 0,

sizeof((vpninfo->dtls_ssl->d1->next_timeout)));

vpninfo->dtls_ssl->d1->timeout_duration = 1;

BIO_ctrl(SSL_get_rbio(vpninfo->dtls_ssl),

BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT, 0,

&(vpninfo->dtls_ssl->d1->next_timeout));

#endif

return 0;

}

ret = SSL_get_error(vpninfo->new_dtls_ssl, ret);

if (ret == SSL_ERROR_WANT_WRITE || ret == SSL_ERROR_WANT_READ) {

if (time(NULL) < vpninfo->new_dtls_started + 5)

return 0;

vpn_progress(vpninfo, PRG_TRACE, _("DTLS handshake timed out\n"));

}

vpn_progress(vpninfo, PRG_ERR, _("DTLS handshake failed: %d\n"), ret);

report_ssl_errors(vpninfo);

/* Kill the new (failed) connection... */

SSL_free(vpninfo->new_dtls_ssl);

FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_rfds);

FD_CLR(vpninfo->new_dtls_fd, &vpninfo->select_efds);

close(vpninfo->new_dtls_fd);

vpninfo->new_dtls_ssl = NULL;

vpninfo->new_dtls_fd = -1;

/* ... and kill the old one too. The only time there'll be a valid

existing session is when it was a rekey, and in that case it's

time for the old one to die. */

if (vpninfo->dtls_ssl) {

SSL_free(vpninfo->dtls_ssl);

close(vpninfo->dtls_fd);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);

vpninfo->dtls_ssl = NULL;

vpninfo->dtls_fd = -1;

}

time(&vpninfo->new_dtls_started);

return -EINVAL;

}

static int dtls_restart(struct openconnect_info *vpninfo)

{

if (vpninfo->dtls_ssl) {

SSL_free(vpninfo->dtls_ssl);

close(vpninfo->dtls_fd);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_rfds);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_wfds);

FD_CLR(vpninfo->dtls_fd, &vpninfo->select_efds);

vpninfo->dtls_ssl = NULL;

vpninfo->dtls_fd = -1;

}

return connect_dtls_socket(vpninfo);

}

int setup_dtls(struct openconnect_info *vpninfo)

{

struct vpn_option *dtls_opt = vpninfo->dtls_options;

int dtls_port = 0;

while (dtls_opt) {

vpn_progress(vpninfo, PRG_TRACE,

_("DTLS option %s : %s\n"),

dtls_opt->option, dtls_opt->value);

if (!strcmp(dtls_opt->option + 7, "Port")) {

dtls_port = atol(dtls_opt->value);

} else if (!strcmp(dtls_opt->option + 7, "Keepalive")) {

vpninfo->dtls_times.keepalive = atol(dtls_opt->value);

} else if (!strcmp(dtls_opt->option + 7, "DPD")) {

int j = atol(dtls_opt->value);

if (j && (!vpninfo->dtls_times.dpd || j < vpninfo->dtls_times.dpd))

vpninfo->dtls_times.dpd = j;

} else if (!strcmp(dtls_opt->option + 7, "Rekey-Time")) {

vpninfo->dtls_times.rekey = atol(dtls_opt->value);

} else if (!strcmp(dtls_opt->option + 7, "CipherSuite")) {

vpninfo->dtls_cipher = strdup(dtls_opt->value);

}

dtls_opt = dtls_opt->next;

}

if (!dtls_port) {

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

vpninfo->dtls_addr = malloc(vpninfo->peer_addrlen);

if (!vpninfo->dtls_addr) {

vpninfo->dtls_attempt_period = 0;

return -ENOMEM;

}

memcpy(vpninfo->dtls_addr, vpninfo->peer_addr, vpninfo->peer_addrlen);

if (vpninfo->peer_addr->sa_family == AF_INET) {

struct sockaddr_in *sin = (void *)vpninfo->dtls_addr;

sin->sin_port = htons(dtls_port);

} else if (vpninfo->peer_addr->sa_family == AF_INET6) {

struct sockaddr_in6 *sin = (void *)vpninfo->dtls_addr;

sin->sin6_port = htons(dtls_port);

} else {

vpn_progress(vpninfo, PRG_ERR,

_("Unknown protocol family %d. Cannot do DTLS\n"),

vpninfo->peer_addr->sa_family);

vpninfo->dtls_attempt_period = 0;

return -EINVAL;

}

if (connect_dtls_socket(vpninfo))

return -EINVAL;

vpn_progress(vpninfo, PRG_TRACE,

_("DTLS connected. DPD %d, Keepalive %d\n"),

vpninfo->dtls_times.dpd, vpninfo->dtls_times.keepalive);

return 0;

}

static struct pkt *dtls_pkt;

int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)

{

int work_done = 0;

char magic_pkt;

while (1) {

int len = vpninfo->mtu;

unsigned char *buf;

if (!dtls_pkt) {

dtls_pkt = malloc(sizeof(struct pkt) + len);

if (!dtls_pkt) {

vpn_progress(vpninfo, PRG_ERR, "Allocation failed\n");

break;

}

}

buf = dtls_pkt->data - 1;

len = SSL_read(vpninfo->dtls_ssl, buf, len + 1);

if (len <= 0)

break;

vpn_progress(vpninfo, PRG_TRACE,

_("Received DTLS packet 0x%02x of %d bytes\n"),

buf[0], len);

vpninfo->dtls_times.last_rx = time(NULL);

switch(buf[0]) {

case AC_PKT_DATA:

queue_new_packet(&vpninfo->incoming_queue, buf+1, len-1);

work_done = 1;

break;

case AC_PKT_DPD_OUT:

vpn_progress(vpninfo, PRG_TRACE, _("Got DTLS DPD request\n"));

/* FIXME: What if the packet doesn't get through? */

magic_pkt = AC_PKT_DPD_RESP;

if (SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1) != 1)

vpn_progress(vpninfo, PRG_ERR,

_("Failed to send DPD response. Expect disconnect\n"));

continue;

case AC_PKT_DPD_RESP:

vpn_progress(vpninfo, PRG_TRACE, _("Got DTLS DPD response\n"));

break;

case AC_PKT_KEEPALIVE:

vpn_progress(vpninfo, PRG_TRACE, _("Got DTLS Keepalive\n"));

break;

default:

vpn_progress(vpninfo, PRG_ERR,

_("Unknown DTLS packet type %02x, len %d\n"),

buf[0], len);

if (1) {

/* Some versions of OpenSSL have bugs with receiving out-of-order

* packets. Not only do they wrongly decide to drop packets if

* two packets get swapped in transit, but they also _fail_ to

* drop the packet in non-blocking mode; instead they return

* the appropriate length of garbage. So don't abort... for now. */

break;

} else {

vpninfo->quit_reason = "Unknown packet received";

return 1;

}

}

}

switch (keepalive_action(&vpninfo->dtls_times, timeout)) {

case KA_REKEY:

vpn_progress(vpninfo, PRG_INFO, _("DTLS rekey due\n"));

/* There ought to be a method of rekeying DTLS without tearing down

the CSTP session and restarting, but we don't (yet) know it */

if (cstp_reconnect(vpninfo)) {

vpn_progress(vpninfo, PRG_ERR, _("Reconnect failed\n"));

vpninfo->quit_reason = "CSTP reconnect failed";

return 1;

}

if (dtls_restart(vpninfo)) {

vpn_progress(vpninfo, PRG_ERR, _("DTLS rekey failed\n"));

return 1;

}

work_done = 1;

break;

case KA_DPD_DEAD:

vpn_progress(vpninfo, PRG_ERR, _("DTLS Dead Peer Detection detected dead peer!\n"));

/* Fall back to SSL, and start a new DTLS connection */

dtls_restart(vpninfo);

return 1;

case KA_DPD:

vpn_progress(vpninfo, PRG_TRACE, _("Send DTLS DPD\n"));

magic_pkt = AC_PKT_DPD_OUT;

SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);

/* last_dpd will just have been set */

vpninfo->dtls_times.last_tx = vpninfo->dtls_times.last_dpd;

work_done = 1;

break;

case KA_KEEPALIVE:

/* No need to send an explicit keepalive

if we have real data to send */

if (vpninfo->outgoing_queue)

break;

vpn_progress(vpninfo, PRG_TRACE, _("Send DTLS Keepalive\n"));

magic_pkt = AC_PKT_KEEPALIVE;

SSL_write(vpninfo->dtls_ssl, &magic_pkt, 1);

time(&vpninfo->dtls_times.last_tx);

work_done = 1;

break;

case KA_NONE:

;

}

/* Service outgoing packet queue */

while (vpninfo->outgoing_queue) {

struct pkt *this = vpninfo->outgoing_queue;

int ret;

vpninfo->outgoing_queue = this->next;

vpninfo->outgoing_qlen--;

/* One byte of header */

this->hdr[7] = AC_PKT_DATA;

ret = SSL_write(vpninfo->dtls_ssl, &this->hdr[7], this->len + 1);

if (ret <= 0) {

ret = SSL_get_error(vpninfo->dtls_ssl, ret);

/* If it's a real error, kill the DTLS connection and

requeue the packet to be sent over SSL */

if (ret != SSL_ERROR_WANT_READ && ret != SSL_ERROR_WANT_WRITE) {

vpn_progress(vpninfo, PRG_ERR,

_("DTLS got write error %d. Falling back to SSL\n"),

ret);

report_ssl_errors(vpninfo);

dtls_restart(vpninfo);

vpninfo->outgoing_queue = this;

vpninfo->outgoing_qlen++;

}

return 1;

}

time(&vpninfo->dtls_times.last_tx);

vpn_progress(vpninfo, PRG_TRACE,

_("Sent DTLS packet of %d bytes; SSL_write() returned %d\n"),

this->len, ret);

free(this);

}

return work_done;

}

#else /* No DTLS support in OpenSSL */

#warning Your version of OpenSSL does not seem to support Cisco DTLS compatibility

int setup_dtls(struct openconnect_info *vpninfo)

{

vpn_progress(vpninfo, PRG_ERR,

_("Built against OpenSSL with no Cisco DTLS support\n"));

return -EINVAL;

}

#endif