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dtls.c
1344 lines (1157 loc) · 38.5 KB
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dtls.c
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/*
* OpenConnect (SSL + DTLS) VPN client
*
* Copyright © 2008-2015 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.
*/
#include <config.h>
#include <errno.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include "openconnect-internal.h"
#ifdef HAVE_DTLS
#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.
*/
#if defined(DTLS_OPENSSL)
#define DTLS_SEND SSL_write
#define DTLS_RECV SSL_read
#define DTLS_FREE SSL_free
/* In the very early days there were cases where this wasn't found in
* the header files but it did still work somehow. I forget the details
* now but I was definitely avoiding using the macro. Let's just define
* it for ourselves instead.*/
#ifndef DTLS1_BAD_VER
#define DTLS1_BAD_VER 0x100
#endif
#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
#if OPENSSL_VERSION_NUMBER >= 0x10100000L
/* Since OpenSSL 1.1, the SSL_SESSION structure is opaque and we can't
* just fill it in directly. So we have to generate the OpenSSL ASN.1
* representation of the SSL_SESSION, and use d2i_SSL_SESSION() to
* create the SSL_SESSION from that. */
static void buf_append_INTEGER(struct oc_text_buf *buf, uint32_t datum)
{
int l;
/* We only handle positive integers up to INT_MAX */
if (datum < 0x80)
l = 1;
else if (datum < 0x8000)
l = 2;
else if (datum < 0x800000)
l = 3;
else
l = 4;
if (buf_ensure_space(buf, 2 + l))
return;
buf->data[buf->pos++] = 0x02;
buf->data[buf->pos++] = l;
while (l--)
buf->data[buf->pos++] = datum >> (l * 8);
}
static void buf_append_OCTET_STRING(struct oc_text_buf *buf, void *data, int len)
{
/* We only (need to) cope with length < 0x80 for now */
if (len >= 0x80) {
buf->error = -EINVAL;
return;
}
if (buf_ensure_space(buf, 2 + len))
return;
buf->data[buf->pos++] = 0x04;
buf->data[buf->pos++] = len;
memcpy(buf->data + buf->pos, data, len);
buf->pos += len;
}
static SSL_SESSION *generate_dtls_session(struct openconnect_info *vpninfo,
int dtlsver, SSL_CIPHER *cipher)
{
struct oc_text_buf *buf = buf_alloc();
SSL_SESSION *dtls_session;
const unsigned char *asn;
uint16_t cid;
buf_append_bytes(buf, "\x30\x80", 2); // SEQUENCE, indeterminate length
buf_append_INTEGER(buf, 1 /* SSL_SESSION_ASN1_VERSION */);
buf_append_INTEGER(buf, dtlsver);
store_be16(&cid, SSL_CIPHER_get_id(cipher) & 0xffff);
buf_append_OCTET_STRING(buf, &cid, 2);
buf_append_OCTET_STRING(buf, vpninfo->dtls_session_id,
sizeof(vpninfo->dtls_session_id));
buf_append_OCTET_STRING(buf, vpninfo->dtls_secret,
sizeof(vpninfo->dtls_secret));
/* If the length actually fits in one byte (which it should), do
* it that way. Else, leave it indeterminate and add two
* end-of-contents octets to mark the end of the SEQUENCE. */
if (!buf_error(buf) && buf->pos <= 0x80)
buf->data[1] = buf->pos - 2;
else
buf_append_bytes(buf, "\0\0", 2);
if (buf_error(buf)) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to create SSL_SESSION ASN.1 for OpenSSL: %s\n"),
strerror(buf_error(buf)));
buf_free(buf);
return NULL;
}
asn = (void *)buf->data;
dtls_session = d2i_SSL_SESSION(NULL, &asn, buf->pos);
buf_free(buf);
if (!dtls_session) {
vpn_progress(vpninfo, PRG_ERR,
_("OpenSSL failed to parse SSL_SESSION ASN.1\n"));
openconnect_report_ssl_errors(vpninfo);
return NULL;
}
return dtls_session;
}
#else /* OpenSSL before 1.1 */
static SSL_SESSION *generate_dtls_session(struct openconnect_info *vpninfo,
int dtlsver, SSL_CIPHER *cipher)
{
SSL_SESSION *dtls_session = SSL_SESSION_new();
if (!dtls_session) {
vpn_progress(vpninfo, PRG_ERR,
_("Initialise DTLSv1 session failed\n"));
return NULL;
}
dtls_session->ssl_version = dtlsver;
dtls_session->master_key_length = sizeof(vpninfo->dtls_secret);
memcpy(dtls_session->master_key, vpninfo->dtls_secret,
sizeof(vpninfo->dtls_secret));
dtls_session->session_id_length = sizeof(vpninfo->dtls_session_id);
memcpy(dtls_session->session_id, vpninfo->dtls_session_id,
sizeof(vpninfo->dtls_session_id));
dtls_session->cipher = cipher;
dtls_session->cipher_id = cipher->id;
return dtls_session;
}
#endif
static int start_dtls_handshake(struct openconnect_info *vpninfo, int dtls_fd)
{
STACK_OF(SSL_CIPHER) *ciphers;
method_const SSL_METHOD *dtls_method;
SSL_SESSION *dtls_session;
SSL *dtls_ssl;
BIO *dtls_bio;
int dtlsver = DTLS1_BAD_VER;
const char *cipher = vpninfo->dtls_cipher;
#ifdef HAVE_DTLS12
if (!strcmp(cipher, "OC-DTLS1_2-AES128-GCM")) {
dtlsver = DTLS1_2_VERSION;
cipher = "AES128-GCM-SHA256";
} else if (!strcmp(cipher, "OC-DTLS1_2-AES256-GCM")) {
dtlsver = DTLS1_2_VERSION;
cipher = "AES256-GCM-SHA384";
}
#endif
if (!vpninfo->dtls_ctx) {
#ifdef HAVE_DTLS12
if (dtlsver == DTLS1_2_VERSION)
dtls_method = DTLSv1_2_client_method();
else
#endif
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"));
openconnect_report_ssl_errors(vpninfo);
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, 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;
}
}
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);
vpninfo->dtls_ctx = NULL;
vpninfo->dtls_attempt_period = 0;
return -EINVAL;
}
/* We're going to "resume" a session which never existed. Fake it... */
dtls_session = generate_dtls_session(vpninfo, dtlsver,
sk_SSL_CIPHER_value(ciphers, 0));
if (!dtls_session) {
SSL_CTX_free(vpninfo->dtls_ctx);
SSL_free(dtls_ssl);
vpninfo->dtls_ctx = NULL;
vpninfo->dtls_attempt_period = 0;
return -EINVAL;
}
/* Add the generated session to the SSL */
if (!SSL_set_session(dtls_ssl, 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"),
DTLS1_BAD_VER);
SSL_CTX_free(vpninfo->dtls_ctx);
SSL_free(dtls_ssl);
vpninfo->dtls_ctx = NULL;
vpninfo->dtls_attempt_period = 0;
SSL_SESSION_free(dtls_session);
return -EINVAL;
}
/* We don't need our own refcount on it any more */
SSL_SESSION_free(dtls_session);
dtls_bio = BIO_new_socket(dtls_fd, BIO_NOCLOSE);
/* Set non-blocking */
BIO_set_nbio(dtls_bio, 1);
SSL_set_bio(dtls_ssl, dtls_bio, dtls_bio);
if (dtlsver == DTLS1_BAD_VER)
SSL_set_options(dtls_ssl, SSL_OP_CISCO_ANYCONNECT);
vpninfo->dtls_ssl = dtls_ssl;
return 0;
}
static int dtls_try_handshake(struct openconnect_info *vpninfo)
{
int ret = SSL_do_handshake(vpninfo->dtls_ssl);
if (ret == 1) {
const char *c;
vpninfo->dtls_state = DTLS_CONNECTED;
vpn_progress(vpninfo, PRG_INFO,
_("Established DTLS connection (using OpenSSL). Ciphersuite %s.\n"),
vpninfo->dtls_cipher);
c = openconnect_get_dtls_compression(vpninfo);
if (c) {
vpn_progress(vpninfo, PRG_INFO,
_("DTLS connection compression using %s.\n"), c);
}
vpninfo->dtls_times.last_rekey = 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 >= 0x10100000L
/* OpenSSL 1.1.0 or above. Do nothing. The SSLeay() function
got renamed, and it's a pointless check in this case
anyway because there's *no* chance that we linked against
1.1.0 and are running against something older than 1.0.0e. */
#elif 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)
/*
* This works for any normal OpenSSL that supports
* Cisco DTLS compatibility (0.9.8m to 1.0.0d inclusive,
* and even later versions although it isn't needed there.
*/
dtls1_stop_timer(vpninfo->dtls_ssl);
#elif defined(BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT)
/*
* Debian restricts visibility of dtls1_stop_timer()
* so do it manually. This version also works on all
* sane versions of OpenSSL:
*/
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));
#elif defined(BIO_CTRL_DGRAM_SET_TIMEOUT)
/*
* OK, here it gets more fun... this shoul handle the case
* of older OpenSSL which has the Cisco DTLS compatibility
* backported, but *not* the fix for RT#1922.
*/
BIO_ctrl(SSL_get_rbio(vpninfo->dtls_ssl),
BIO_CTRL_DGRAM_SET_TIMEOUT, 0, NULL);
#else
/*
* And if they don't have any of the above, they probably
* don't have RT#1829 fixed either, but that's OK because
* that's the "fix" that *introduces* the timeout we're
* trying to disable. So do nothing...
*/
#endif
return 0;
}
ret = SSL_get_error(vpninfo->dtls_ssl, ret);
if (ret == SSL_ERROR_WANT_WRITE || ret == SSL_ERROR_WANT_READ) {
static int badossl_bitched = 0;
if (time(NULL) < vpninfo->new_dtls_started + 12)
return 0;
if (((OPENSSL_VERSION_NUMBER >= 0x100000b0L && OPENSSL_VERSION_NUMBER <= 0x100000c0L) || \
(OPENSSL_VERSION_NUMBER >= 0x10001040L && OPENSSL_VERSION_NUMBER <= 0x10001060L) || \
OPENSSL_VERSION_NUMBER == 0x10002000L) && !badossl_bitched) {
badossl_bitched = 1;
vpn_progress(vpninfo, PRG_ERR, _("DTLS handshake timed out\n"));
vpn_progress(vpninfo, PRG_ERR, _("This is probably because your OpenSSL is broken\n"
"See http://rt.openssl.org/Ticket/Display.html?id=2984\n"));
} else {
vpn_progress(vpninfo, PRG_DEBUG, _("DTLS handshake timed out\n"));
}
}
vpn_progress(vpninfo, PRG_ERR, _("DTLS handshake failed: %d\n"), ret);
openconnect_report_ssl_errors(vpninfo);
dtls_close(vpninfo);
vpninfo->dtls_state = DTLS_SLEEPING;
time(&vpninfo->new_dtls_started);
return -EINVAL;
}
void dtls_shutdown(struct openconnect_info *vpninfo)
{
dtls_close(vpninfo);
SSL_CTX_free(vpninfo->dtls_ctx);
}
void append_dtls_ciphers(struct openconnect_info *vpninfo, struct oc_text_buf *buf)
{
#ifdef HAVE_DTLS12
buf_append(buf, "OC-DTLS1_2-AES256-GCM:OC-DTLS1_2-AES128-GCM:AES256-SHA:AES128-SHA:DES-CBC3-SHA:DES-CBC-SHA");
#else
buf_append(buf, "AES256-SHA:AES128-SHA:DES-CBC3-SHA:DES-CBC-SHA");
#endif
}
#elif defined(DTLS_GNUTLS)
#include <gnutls/dtls.h>
#include "gnutls.h"
#if GNUTLS_VERSION_NUMBER < 0x030200
# define GNUTLS_DTLS1_2 202
#endif
#if GNUTLS_VERSION_NUMBER < 0x030400
# define GNUTLS_CIPHER_CHACHA20_POLY1305 23
#endif
static void detect_mtu(struct openconnect_info *vpninfo);
struct {
const char *name;
gnutls_protocol_t version;
gnutls_cipher_algorithm_t cipher;
gnutls_kx_algorithm_t kx;
gnutls_mac_algorithm_t mac;
const char *prio;
const char *min_gnutls_version;
} gnutls_dtls_ciphers[] = {
{ "AES128-SHA", GNUTLS_DTLS0_9, GNUTLS_CIPHER_AES_128_CBC, GNUTLS_KX_RSA, GNUTLS_MAC_SHA1,
"NONE:+VERS-DTLS0.9:+COMP-NULL:+AES-128-CBC:+SHA1:+RSA:%COMPAT", "3.0.0" },
{ "AES256-SHA", GNUTLS_DTLS0_9, GNUTLS_CIPHER_AES_256_CBC, GNUTLS_KX_RSA, GNUTLS_MAC_SHA1,
"NONE:+VERS-DTLS0.9:+COMP-NULL:+AES-256-CBC:+SHA1:+RSA:%COMPAT", "3.0.0" },
{ "DES-CBC3-SHA", GNUTLS_DTLS0_9, GNUTLS_CIPHER_3DES_CBC, GNUTLS_KX_RSA, GNUTLS_MAC_SHA1,
"NONE:+VERS-DTLS0.9:+COMP-NULL:+3DES-CBC:+SHA1:+RSA:%COMPAT", "3.0.0" },
{ "OC-DTLS1_2-AES128-GCM", GNUTLS_DTLS1_2, GNUTLS_CIPHER_AES_128_GCM, GNUTLS_KX_RSA, GNUTLS_MAC_AEAD,
"NONE:+VERS-DTLS1.2:+COMP-NULL:+AES-128-GCM:+AEAD:+RSA:%COMPAT:+SIGN-ALL", "3.2.7" },
{ "OC-DTLS1_2-AES256-GCM", GNUTLS_DTLS1_2, GNUTLS_CIPHER_AES_256_GCM, GNUTLS_KX_RSA, GNUTLS_MAC_AEAD,
"NONE:+VERS-DTLS1.2:+COMP-NULL:+AES-256-GCM:+AEAD:+RSA:%COMPAT:+SIGN-ALL", "3.2.7" },
{ "OC2-DTLS1_2-CHACHA20-POLY1305", GNUTLS_DTLS1_2, GNUTLS_CIPHER_CHACHA20_POLY1305, GNUTLS_KX_PSK, GNUTLS_MAC_AEAD,
"NONE:+VERS-DTLS1.2:+COMP-NULL:+CHACHA20-POLY1305:+AEAD:+PSK:%COMPAT:+SIGN-ALL", "3.4.8" },
/* NB. We agreed that any new cipher suites probably shouldn't use
* Cisco's session resume hack (which ties us to a specific version
* of DTLS). Instead, we'll use GNUTLS_KX_PSK and let it negotiate
* the session properly. We might want to wait for
* draft-jay-tls-psk-identity-extension before we do that. */
};
#if GNUTLS_VERSION_NUMBER < 0x030009
void append_dtls_ciphers(struct openconnect_info *vpninfo, struct oc_text_buf *buf)
{
int i, first = 1;
for (i = 0; i < sizeof(gnutls_dtls_ciphers) / sizeof(gnutls_dtls_ciphers[0]); i++) {
if (gnutls_check_version(gnutls_dtls_ciphers[i].min_gnutls_version)) {
buf_append(buf, "%s%s", first ? "" : ":",
gnutls_dtls_ciphers[i].name);
first = 0;
}
}
#else
void append_dtls_ciphers(struct openconnect_info *vpninfo, struct oc_text_buf *buf)
{
/* only enable the ciphers that would have been negotiated in the TLS channel */
unsigned i, j, first = 1;
int ret;
unsigned idx;
gnutls_cipher_algorithm_t cipher;
gnutls_mac_algorithm_t mac;
gnutls_priority_t cache;
uint32_t used = 0;
ret = gnutls_priority_init(&cache, vpninfo->gnutls_prio, NULL);
if (ret < 0) {
buf->error = -EIO;
return;
}
for (j=0; ; j++) {
ret = gnutls_priority_get_cipher_suite_index(cache, j, &idx);
if (ret == GNUTLS_E_UNKNOWN_CIPHER_SUITE)
continue;
else if (ret < 0)
break;
if (gnutls_cipher_suite_info(idx, NULL, NULL, &cipher, &mac, NULL) != NULL) {
for (i = 0; i < sizeof(gnutls_dtls_ciphers)/sizeof(gnutls_dtls_ciphers[0]); i++) {
if (used & (1 << i))
continue;
if (gnutls_dtls_ciphers[i].mac == mac && gnutls_dtls_ciphers[i].cipher == cipher) {
buf_append(buf, "%s%s", first ? "" : ":",
gnutls_dtls_ciphers[i].name);
first = 0;
used |= (1 << i);
break;
}
}
}
}
gnutls_priority_deinit(cache);
}
#endif
#define DTLS_SEND gnutls_record_send
#define DTLS_RECV gnutls_record_recv
#define DTLS_FREE gnutls_deinit
static int start_dtls_handshake(struct openconnect_info *vpninfo, int dtls_fd)
{
gnutls_session_t dtls_ssl;
gnutls_datum_t master_secret, session_id;
int err;
int cipher;
for (cipher = 0; cipher < sizeof(gnutls_dtls_ciphers)/sizeof(gnutls_dtls_ciphers[0]); cipher++) {
if (gnutls_check_version(gnutls_dtls_ciphers[cipher].min_gnutls_version) == NULL)
continue;
if (!strcmp(vpninfo->dtls_cipher, gnutls_dtls_ciphers[cipher].name))
goto found_cipher;
}
vpn_progress(vpninfo, PRG_ERR, _("Unknown DTLS parameters for requested CipherSuite '%s'\n"),
vpninfo->dtls_cipher);
vpninfo->dtls_attempt_period = 0;
return -EINVAL;
found_cipher:
gnutls_init(&dtls_ssl, GNUTLS_CLIENT|GNUTLS_DATAGRAM|GNUTLS_NONBLOCK);
err = gnutls_priority_set_direct(dtls_ssl,
gnutls_dtls_ciphers[cipher].prio,
NULL);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to set DTLS priority: %s\n"),
gnutls_strerror(err));
gnutls_deinit(dtls_ssl);
vpninfo->dtls_attempt_period = 0;
return -EINVAL;
}
gnutls_transport_set_ptr(dtls_ssl,
(gnutls_transport_ptr_t)(intptr_t)dtls_fd);
gnutls_record_disable_padding(dtls_ssl);
master_secret.data = vpninfo->dtls_secret;
master_secret.size = sizeof(vpninfo->dtls_secret);
session_id.data = vpninfo->dtls_session_id;
session_id.size = sizeof(vpninfo->dtls_session_id);
err = gnutls_session_set_premaster(dtls_ssl, GNUTLS_CLIENT, gnutls_dtls_ciphers[cipher].version,
gnutls_dtls_ciphers[cipher].kx, gnutls_dtls_ciphers[cipher].cipher,
gnutls_dtls_ciphers[cipher].mac, GNUTLS_COMP_NULL,
&master_secret, &session_id);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to set DTLS session parameters: %s\n"),
gnutls_strerror(err));
gnutls_deinit(dtls_ssl);
vpninfo->dtls_attempt_period = 0;
return -EINVAL;
}
vpninfo->dtls_ssl = dtls_ssl;
return 0;
}
static int dtls_try_handshake(struct openconnect_info *vpninfo)
{
int err = gnutls_handshake(vpninfo->dtls_ssl);
char *str;
if (!err) {
#ifdef HAVE_GNUTLS_DTLS_SET_DATA_MTU
/* Make sure GnuTLS's idea of the MTU is sufficient to take
a full VPN MTU (with 1-byte header) in a data record. */
err = gnutls_dtls_set_data_mtu(vpninfo->dtls_ssl, vpninfo->ip_info.mtu + 1);
if (err) {
vpn_progress(vpninfo, PRG_ERR,
_("Failed to set DTLS MTU: %s\n"),
gnutls_strerror(err));
goto error;
}
#else
/* If we don't have gnutls_dtls_set_data_mtu() then make sure
we leave enough headroom by adding the worst-case overhead.
We only support AES128-CBC and DES-CBC3-SHA anyway, so
working out the worst case isn't hard. */
gnutls_dtls_set_mtu(vpninfo->dtls_ssl,
vpninfo->ip_info.mtu + 1 /* packet + header */
+ 13 /* DTLS header */
+ 20 /* biggest supported MAC (SHA1) */
+ 16 /* biggest supported IV (AES-128) */
+ 16 /* max padding */);
#endif
vpninfo->dtls_state = DTLS_CONNECTED;
str = get_gnutls_cipher(vpninfo->dtls_ssl);
if (str) {
const char *c;
vpn_progress(vpninfo, PRG_INFO,
_("Established DTLS connection (using GnuTLS). Ciphersuite %s.\n"),
str);
gnutls_free(str);
c = openconnect_get_dtls_compression(vpninfo);
if (c) {
vpn_progress(vpninfo, PRG_INFO,
_("DTLS connection compression using %s.\n"), c);
}
}
vpninfo->dtls_times.last_rekey = vpninfo->dtls_times.last_rx =
vpninfo->dtls_times.last_tx = time(NULL);
detect_mtu(vpninfo);
/* XXX: For OpenSSL we explicitly prevent retransmits here. */
return 0;
}
if (err == GNUTLS_E_AGAIN) {
if (time(NULL) < vpninfo->new_dtls_started + 12)
return 0;
vpn_progress(vpninfo, PRG_DEBUG, _("DTLS handshake timed out\n"));
}
vpn_progress(vpninfo, PRG_ERR, _("DTLS handshake failed: %s\n"),
gnutls_strerror(err));
if (err == GNUTLS_E_PUSH_ERROR)
vpn_progress(vpninfo, PRG_ERR,
_("(Is a firewall preventing you from sending UDP packets?)\n"));
error:
dtls_close(vpninfo);
vpninfo->dtls_state = DTLS_SLEEPING;
time(&vpninfo->new_dtls_started);
return -EINVAL;
}
void dtls_shutdown(struct openconnect_info *vpninfo)
{
dtls_close(vpninfo);
}
#endif
static int connect_dtls_socket(struct openconnect_info *vpninfo)
{
int dtls_fd, ret;
/* Sanity check for the removal of new_dtls_{fd,ssl} */
if (vpninfo->dtls_fd != -1) {
vpn_progress(vpninfo, PRG_ERR, _("DTLS connection attempted with an existing fd\n"));
vpninfo->dtls_attempt_period = 0;
return -EINVAL;
}
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 = udp_connect(vpninfo);
if (dtls_fd < 0)
return -EINVAL;
ret = start_dtls_handshake(vpninfo, dtls_fd);
if (ret) {
closesocket(dtls_fd);
return ret;
}
vpninfo->dtls_state = DTLS_CONNECTING;
vpninfo->dtls_fd = dtls_fd;
monitor_fd_new(vpninfo, dtls);
monitor_read_fd(vpninfo, dtls);
monitor_except_fd(vpninfo, dtls);
time(&vpninfo->new_dtls_started);
return dtls_try_handshake(vpninfo);
}
void dtls_close(struct openconnect_info *vpninfo)
{
if (vpninfo->dtls_ssl) {
DTLS_FREE(vpninfo->dtls_ssl);
closesocket(vpninfo->dtls_fd);
unmonitor_read_fd(vpninfo, dtls);
unmonitor_write_fd(vpninfo, dtls);
unmonitor_except_fd(vpninfo, dtls);
vpninfo->dtls_ssl = NULL;
vpninfo->dtls_fd = -1;
}
}
static int dtls_reconnect(struct openconnect_info *vpninfo)
{
dtls_close(vpninfo);
vpninfo->dtls_state = DTLS_SLEEPING;
return connect_dtls_socket(vpninfo);
}
int dtls_setup(struct openconnect_info *vpninfo, int dtls_attempt_period)
{
struct oc_vpn_option *dtls_opt = vpninfo->dtls_options;
int dtls_port = 0;
if (vpninfo->dtls_state == DTLS_DISABLED)
return -EINVAL;
vpninfo->dtls_attempt_period = dtls_attempt_period;
if (!dtls_attempt_period)
return 0;
#if defined(OPENCONNECT_GNUTLS) && defined(DTLS_OPENSSL)
/* If we're using GnuTLS for authentication but OpenSSL for DTLS,
we'll need to initialise OpenSSL now... */
SSL_library_init();
ERR_clear_error();
SSL_load_error_strings();
OpenSSL_add_all_algorithms();
#endif
while (dtls_opt) {
vpn_progress(vpninfo, PRG_DEBUG,
_("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-Method")) {
if (!strcmp(dtls_opt->value, "new-tunnel"))
vpninfo->dtls_times.rekey_method = REKEY_TUNNEL;
else if (!strcmp(dtls_opt->value, "ssl"))
vpninfo->dtls_times.rekey_method = REKEY_SSL;
else
vpninfo->dtls_times.rekey_method = REKEY_NONE;
} 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;
}
if (vpninfo->dtls_times.rekey <= 0)
vpninfo->dtls_times.rekey_method = REKEY_NONE;
if (udp_sockaddr(vpninfo, dtls_port)) {
vpninfo->dtls_attempt_period = 0;
return -EINVAL;
}
if (connect_dtls_socket(vpninfo))
return -EINVAL;
vpn_progress(vpninfo, PRG_DEBUG,
_("DTLS initialised. DPD %d, Keepalive %d\n"),
vpninfo->dtls_times.dpd, vpninfo->dtls_times.keepalive);
return 0;
}
int dtls_mainloop(struct openconnect_info *vpninfo, int *timeout)
{
int work_done = 0;
char magic_pkt;
if (vpninfo->dtls_need_reconnect) {
vpninfo->dtls_need_reconnect = 0;
dtls_reconnect(vpninfo);
return 1;
}
if (vpninfo->dtls_state == DTLS_CONNECTING) {
dtls_try_handshake(vpninfo);
return 0;
}
if (vpninfo->dtls_state == DTLS_SLEEPING) {
int when = vpninfo->new_dtls_started + vpninfo->dtls_attempt_period - time(NULL);
if (when <= 0) {
vpn_progress(vpninfo, PRG_DEBUG, _("Attempt new DTLS connection\n"));
connect_dtls_socket(vpninfo);
} else if ((when * 1000) < *timeout) {
*timeout = when * 1000;
}
return 0;
}
while (1) {
int len = vpninfo->ip_info.mtu;
unsigned char *buf;
if (!vpninfo->dtls_pkt) {
vpninfo->dtls_pkt = malloc(sizeof(struct pkt) + len);
if (!vpninfo->dtls_pkt) {
vpn_progress(vpninfo, PRG_ERR, _("Allocation failed\n"));
break;
}
}
buf = vpninfo->dtls_pkt->data - 1;
len = DTLS_RECV(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:
vpninfo->dtls_pkt->len = len - 1;
queue_packet(&vpninfo->incoming_queue, vpninfo->dtls_pkt);
vpninfo->dtls_pkt = NULL;
work_done = 1;
break;
case AC_PKT_DPD_OUT:
vpn_progress(vpninfo, PRG_DEBUG, _("Got DTLS DPD request\n"));
/* FIXME: What if the packet doesn't get through? */
magic_pkt = AC_PKT_DPD_RESP;
if (DTLS_SEND(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_DEBUG, _("Got DTLS DPD response\n"));
break;
case AC_PKT_KEEPALIVE:
vpn_progress(vpninfo, PRG_DEBUG, _("Got DTLS Keepalive\n"));
break;
case AC_PKT_COMPRESSED:
if (!vpninfo->dtls_compr) {
vpn_progress(vpninfo, PRG_ERR,
_("Compressed DTLS packet received when compression not enabled\n"));
goto unknown_pkt;
}
decompress_and_queue_packet(vpninfo, vpninfo->dtls_compr,
vpninfo->dtls_pkt->data, len - 1);
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 {
unknown_pkt:
vpninfo->quit_reason = "Unknown packet received";
return 1;
}
}
}
switch (keepalive_action(&vpninfo->dtls_times, timeout)) {
case KA_REKEY: {
int ret;
vpn_progress(vpninfo, PRG_INFO, _("DTLS rekey due\n"));
if (vpninfo->dtls_times.rekey_method == REKEY_SSL) {
time(&vpninfo->new_dtls_started);
vpninfo->dtls_state = DTLS_CONNECTING;
ret = dtls_try_handshake(vpninfo);
if (ret) {
vpn_progress(vpninfo, PRG_ERR, _("DTLS Rehandshake failed; reconnecting.\n"));
return connect_dtls_socket(vpninfo);
}
}
return 1;
}
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_reconnect(vpninfo);
return 1;
case KA_DPD:
vpn_progress(vpninfo, PRG_DEBUG, _("Send DTLS DPD\n"));
magic_pkt = AC_PKT_DPD_OUT;
if (DTLS_SEND(vpninfo->dtls_ssl, &magic_pkt, 1) != 1)
vpn_progress(vpninfo, PRG_ERR,
_("Failed to send DPD request. Expect disconnect\n"));
/* 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.head)
break;
vpn_progress(vpninfo, PRG_DEBUG, _("Send DTLS Keepalive\n"));
magic_pkt = AC_PKT_KEEPALIVE;
if (DTLS_SEND(vpninfo->dtls_ssl, &magic_pkt, 1) != 1)
vpn_progress(vpninfo, PRG_ERR,
_("Failed to send keepalive request. Expect disconnect\n"));
time(&vpninfo->dtls_times.last_tx);
work_done = 1;
break;
case KA_NONE:
;
}