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openssl/ssl/d1_lib.c
Matt Caswell e3d0dae7cf DTLSv1_listen rewrite 
The existing implementation of DTLSv1_listen() is fundamentally flawed. This
function is used in DTLS solutions to listen for new incoming connections
from DTLS clients. A client will send an initial ClientHello. The server
will respond with a HelloVerifyRequest containing a unique cookie. The
client the responds with a second ClientHello - which this time contains the
cookie.

Once the cookie has been verified then DTLSv1_listen() returns to user code,
which is typically expected to continue the handshake with a call to (for
example) SSL_accept().

Whilst listening for incoming ClientHellos, the underlying BIO is usually in
an unconnected state. Therefore ClientHellos can come in from *any* peer.
The arrival of the first ClientHello without the cookie, and the second one
with it, could be interspersed with other intervening messages from
different clients.

The whole purpose of this mechanism is as a defence against DoS attacks. The
idea is to avoid allocating state on the server until the client has
verified that it is capable of receiving messages at the address it claims
to come from. However the existing DTLSv1_listen() implementation completely
fails to do this. It attempts to super-impose itself on the standard state
machine and reuses all of this code. However the standard state machine
expects to operate in a stateful manner with a single client, and this can
cause various problems.

A second more minor issue is that the return codes from this function are
quite confused, with no distinction made between fatal and non-fatal errors.
Most user code treats all errors as non-fatal, and simply retries the call
to DTLSv1_listen().

This commit completely rewrites the implementation of DTLSv1_listen() and
provides a stand alone implementation that does not rely on the existing
state machine. It also provides more consistent return codes.

Reviewed-by: Andy Polyakov <appro@openssl.org>
2015-09-23 13:53:26 +01:00

909 lines
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/* ssl/d1_lib.c */
/*
* DTLS implementation written by Nagendra Modadugu
* (nagendra@cs.stanford.edu) for the OpenSSL project 2005.
*/
/* ====================================================================
* Copyright (c) 1999-2005 The OpenSSL Project. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. All advertising materials mentioning features or use of this
* software must display the following acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
*
* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
* endorse or promote products derived from this software without
* prior written permission. For written permission, please contact
* openssl-core@OpenSSL.org.
*
* 5. Products derived from this software may not be called "OpenSSL"
* nor may "OpenSSL" appear in their names without prior written
* permission of the OpenSSL Project.
*
* 6. Redistributions of any form whatsoever must retain the following
* acknowledgment:
* "This product includes software developed by the OpenSSL Project
* for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
*
* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* This product includes cryptographic software written by Eric Young
* (eay@cryptsoft.com). This product includes software written by Tim
* Hudson (tjh@cryptsoft.com).
*
*/
#include <stdio.h>
#define USE_SOCKETS
#include <openssl/objects.h>
#include "ssl_locl.h"
#if defined(OPENSSL_SYS_VMS)
# include <sys/timeb.h>
#elif defined(OPENSSL_SYS_NETWARE) && !defined(_WINSOCK2API_)
# include <sys/timeval.h>
#elif defined(OPENSSL_SYS_VXWORKS)
# include <sys/times.h>
#elif !defined(OPENSSL_SYS_WIN32)
# include <sys/time.h>
#endif
static void get_current_time(struct timeval *t);
static int dtls1_set_handshake_header(SSL *s, int type, unsigned long len);
static int dtls1_handshake_write(SSL *s);
int dtls1_listen(SSL *s, struct sockaddr *client);
const SSL3_ENC_METHOD DTLSv1_enc_data = {
tls1_enc,
tls1_mac,
tls1_setup_key_block,
tls1_generate_master_secret,
tls1_change_cipher_state,
tls1_final_finish_mac,
TLS1_FINISH_MAC_LENGTH,
tls1_cert_verify_mac,
TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
tls1_alert_code,
tls1_export_keying_material,
SSL_ENC_FLAG_DTLS | SSL_ENC_FLAG_EXPLICIT_IV,
DTLS1_HM_HEADER_LENGTH,
dtls1_set_handshake_header,
dtls1_handshake_write
};
const SSL3_ENC_METHOD DTLSv1_2_enc_data = {
tls1_enc,
tls1_mac,
tls1_setup_key_block,
tls1_generate_master_secret,
tls1_change_cipher_state,
tls1_final_finish_mac,
TLS1_FINISH_MAC_LENGTH,
tls1_cert_verify_mac,
TLS_MD_CLIENT_FINISH_CONST, TLS_MD_CLIENT_FINISH_CONST_SIZE,
TLS_MD_SERVER_FINISH_CONST, TLS_MD_SERVER_FINISH_CONST_SIZE,
tls1_alert_code,
tls1_export_keying_material,
SSL_ENC_FLAG_DTLS | SSL_ENC_FLAG_EXPLICIT_IV | SSL_ENC_FLAG_SIGALGS
| SSL_ENC_FLAG_SHA256_PRF | SSL_ENC_FLAG_TLS1_2_CIPHERS,
DTLS1_HM_HEADER_LENGTH,
dtls1_set_handshake_header,
dtls1_handshake_write
};
long dtls1_default_timeout(void)
{
/*
* 2 hours, the 24 hours mentioned in the DTLSv1 spec is way too long for
* http, the cache would over fill
*/
return (60 * 60 * 2);
}
int dtls1_new(SSL *s)
{
DTLS1_STATE *d1;
if (!DTLS_RECORD_LAYER_new(&s->rlayer)) {
return 0;
}
if (!ssl3_new(s))
return (0);
if ((d1 = OPENSSL_zalloc(sizeof(*d1))) == NULL) {
ssl3_free(s);
return (0);
}
d1->buffered_messages = pqueue_new();
d1->sent_messages = pqueue_new();
if (s->server) {
d1->cookie_len = sizeof(s->d1->cookie);
}
d1->link_mtu = 0;
d1->mtu = 0;
if (!d1->buffered_messages || !d1->sent_messages) {
pqueue_free(d1->buffered_messages);
pqueue_free(d1->sent_messages);
OPENSSL_free(d1);
ssl3_free(s);
return (0);
}
s->d1 = d1;
s->method->ssl_clear(s);
return (1);
}
static void dtls1_clear_queues(SSL *s)
{
pitem *item = NULL;
hm_fragment *frag = NULL;
while ((item = pqueue_pop(s->d1->buffered_messages)) != NULL) {
frag = (hm_fragment *)item->data;
dtls1_hm_fragment_free(frag);
pitem_free(item);
}
while ((item = pqueue_pop(s->d1->sent_messages)) != NULL) {
frag = (hm_fragment *)item->data;
dtls1_hm_fragment_free(frag);
pitem_free(item);
}
}
void dtls1_free(SSL *s)
{
DTLS_RECORD_LAYER_free(&s->rlayer);
ssl3_free(s);
dtls1_clear_queues(s);
pqueue_free(s->d1->buffered_messages);
pqueue_free(s->d1->sent_messages);
OPENSSL_free(s->d1);
s->d1 = NULL;
}
void dtls1_clear(SSL *s)
{
pqueue buffered_messages;
pqueue sent_messages;
unsigned int mtu;
unsigned int link_mtu;
DTLS_RECORD_LAYER_clear(&s->rlayer);
if (s->d1) {
buffered_messages = s->d1->buffered_messages;
sent_messages = s->d1->sent_messages;
mtu = s->d1->mtu;
link_mtu = s->d1->link_mtu;
dtls1_clear_queues(s);
memset(s->d1, 0, sizeof(*s->d1));
if (s->server) {
s->d1->cookie_len = sizeof(s->d1->cookie);
}
if (SSL_get_options(s) & SSL_OP_NO_QUERY_MTU) {
s->d1->mtu = mtu;
s->d1->link_mtu = link_mtu;
}
s->d1->buffered_messages = buffered_messages;
s->d1->sent_messages = sent_messages;
}
ssl3_clear(s);
if (s->options & SSL_OP_CISCO_ANYCONNECT)
s->client_version = s->version = DTLS1_BAD_VER;
else if (s->method->version == DTLS_ANY_VERSION)
s->version = DTLS1_2_VERSION;
else
s->version = s->method->version;
}
long dtls1_ctrl(SSL *s, int cmd, long larg, void *parg)
{
int ret = 0;
switch (cmd) {
case DTLS_CTRL_GET_TIMEOUT:
if (dtls1_get_timeout(s, (struct timeval *)parg) != NULL) {
ret = 1;
}
break;
case DTLS_CTRL_HANDLE_TIMEOUT:
ret = dtls1_handle_timeout(s);
break;
case DTLS_CTRL_LISTEN:
ret = dtls1_listen(s, parg);
break;
case SSL_CTRL_CHECK_PROTO_VERSION:
/*
* For library-internal use; checks that the current protocol is the
* highest enabled version (according to s->ctx->method, as version
* negotiation may have changed s->method).
*/
if (s->version == s->ctx->method->version)
return 1;
/*
* Apparently we're using a version-flexible SSL_METHOD (not at its
* highest protocol version).
*/
if (s->ctx->method->version == DTLS_method()->version) {
#if DTLS_MAX_VERSION != DTLS1_2_VERSION
# error Code needs update for DTLS_method() support beyond DTLS1_2_VERSION.
#endif
if (!(s->options & SSL_OP_NO_DTLSv1_2))
return s->version == DTLS1_2_VERSION;
if (!(s->options & SSL_OP_NO_DTLSv1))
return s->version == DTLS1_VERSION;
}
return 0; /* Unexpected state; fail closed. */
case DTLS_CTRL_SET_LINK_MTU:
if (larg < (long)dtls1_link_min_mtu())
return 0;
s->d1->link_mtu = larg;
return 1;
case DTLS_CTRL_GET_LINK_MIN_MTU:
return (long)dtls1_link_min_mtu();
case SSL_CTRL_SET_MTU:
/*
* We may not have a BIO set yet so can't call dtls1_min_mtu()
* We'll have to make do with dtls1_link_min_mtu() and max overhead
*/
if (larg < (long)dtls1_link_min_mtu() - DTLS1_MAX_MTU_OVERHEAD)
return 0;
s->d1->mtu = larg;
return larg;
default:
ret = ssl3_ctrl(s, cmd, larg, parg);
break;
}
return (ret);
}
/*
* As it's impossible to use stream ciphers in "datagram" mode, this
* simple filter is designed to disengage them in DTLS. Unfortunately
* there is no universal way to identify stream SSL_CIPHER, so we have
* to explicitly list their SSL_* codes. Currently RC4 is the only one
* available, but if new ones emerge, they will have to be added...
*/
const SSL_CIPHER *dtls1_get_cipher(unsigned int u)
{
const SSL_CIPHER *ciph = ssl3_get_cipher(u);
if (ciph != NULL) {
if (ciph->algorithm_enc == SSL_RC4)
return NULL;
}
return ciph;
}
void dtls1_start_timer(SSL *s)
{
#ifndef OPENSSL_NO_SCTP
/* Disable timer for SCTP */
if (BIO_dgram_is_sctp(SSL_get_wbio(s))) {
memset(&s->d1->next_timeout, 0, sizeof(s->d1->next_timeout));
return;
}
#endif
/* If timer is not set, initialize duration with 1 second */
if (s->d1->next_timeout.tv_sec == 0 && s->d1->next_timeout.tv_usec == 0) {
s->d1->timeout_duration = 1;
}
/* Set timeout to current time */
get_current_time(&(s->d1->next_timeout));
/* Add duration to current time */
s->d1->next_timeout.tv_sec += s->d1->timeout_duration;
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT, 0,
&(s->d1->next_timeout));
}
struct timeval *dtls1_get_timeout(SSL *s, struct timeval *timeleft)
{
struct timeval timenow;
/* If no timeout is set, just return NULL */
if (s->d1->next_timeout.tv_sec == 0 && s->d1->next_timeout.tv_usec == 0) {
return NULL;
}
/* Get current time */
get_current_time(&timenow);
/* If timer already expired, set remaining time to 0 */
if (s->d1->next_timeout.tv_sec < timenow.tv_sec ||
(s->d1->next_timeout.tv_sec == timenow.tv_sec &&
s->d1->next_timeout.tv_usec <= timenow.tv_usec)) {
memset(timeleft, 0, sizeof(*timeleft));
return timeleft;
}
/* Calculate time left until timer expires */
memcpy(timeleft, &(s->d1->next_timeout), sizeof(struct timeval));
timeleft->tv_sec -= timenow.tv_sec;
timeleft->tv_usec -= timenow.tv_usec;
if (timeleft->tv_usec < 0) {
timeleft->tv_sec--;
timeleft->tv_usec += 1000000;
}
/*
* If remaining time is less than 15 ms, set it to 0 to prevent issues
* because of small devergences with socket timeouts.
*/
if (timeleft->tv_sec == 0 && timeleft->tv_usec < 15000) {
memset(timeleft, 0, sizeof(*timeleft));
}
return timeleft;
}
int dtls1_is_timer_expired(SSL *s)
{
struct timeval timeleft;
/* Get time left until timeout, return false if no timer running */
if (dtls1_get_timeout(s, &timeleft) == NULL) {
return 0;
}
/* Return false if timer is not expired yet */
if (timeleft.tv_sec > 0 || timeleft.tv_usec > 0) {
return 0;
}
/* Timer expired, so return true */
return 1;
}
void dtls1_double_timeout(SSL *s)
{
s->d1->timeout_duration *= 2;
if (s->d1->timeout_duration > 60)
s->d1->timeout_duration = 60;
dtls1_start_timer(s);
}
void dtls1_stop_timer(SSL *s)
{
/* Reset everything */
memset(&s->d1->timeout, 0, sizeof(s->d1->timeout));
memset(&s->d1->next_timeout, 0, sizeof(s->d1->next_timeout));
s->d1->timeout_duration = 1;
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT, 0,
&(s->d1->next_timeout));
/* Clear retransmission buffer */
dtls1_clear_record_buffer(s);
}
int dtls1_check_timeout_num(SSL *s)
{
unsigned int mtu;
s->d1->timeout.num_alerts++;
/* Reduce MTU after 2 unsuccessful retransmissions */
if (s->d1->timeout.num_alerts > 2
&& !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
mtu =
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_GET_FALLBACK_MTU, 0,
NULL);
if (mtu < s->d1->mtu)
s->d1->mtu = mtu;
}
if (s->d1->timeout.num_alerts > DTLS1_TMO_ALERT_COUNT) {
/* fail the connection, enough alerts have been sent */
SSLerr(SSL_F_DTLS1_CHECK_TIMEOUT_NUM, SSL_R_READ_TIMEOUT_EXPIRED);
return -1;
}
return 0;
}
int dtls1_handle_timeout(SSL *s)
{
/* if no timer is expired, don't do anything */
if (!dtls1_is_timer_expired(s)) {
return 0;
}
dtls1_double_timeout(s);
if (dtls1_check_timeout_num(s) < 0)
return -1;
s->d1->timeout.read_timeouts++;
if (s->d1->timeout.read_timeouts > DTLS1_TMO_READ_COUNT) {
s->d1->timeout.read_timeouts = 1;
}
#ifndef OPENSSL_NO_HEARTBEATS
if (s->tlsext_hb_pending) {
s->tlsext_hb_pending = 0;
return dtls1_heartbeat(s);
}
#endif
dtls1_start_timer(s);
return dtls1_retransmit_buffered_messages(s);
}
static void get_current_time(struct timeval *t)
{
#if defined(_WIN32)
SYSTEMTIME st;
union {
unsigned __int64 ul;
FILETIME ft;
} now;
GetSystemTime(&st);
SystemTimeToFileTime(&st, &now.ft);
# ifdef __MINGW32__
now.ul -= 116444736000000000ULL;
# else
now.ul -= 116444736000000000UI64; /* re-bias to 1/1/1970 */
# endif
t->tv_sec = (long)(now.ul / 10000000);
t->tv_usec = ((int)(now.ul % 10000000)) / 10;
#elif defined(OPENSSL_SYS_VMS)
struct timeb tb;
ftime(&tb);
t->tv_sec = (long)tb.time;
t->tv_usec = (long)tb.millitm * 1000;
#else
gettimeofday(t, NULL);
#endif
}
#define LISTEN_SUCCESS 2
#define LISTEN_SEND_VERIFY_REQUEST 1
int dtls1_listen(SSL *s, struct sockaddr *client)
{
int next, n, ret = 0, clearpkt = 0;
unsigned char cookie[DTLS1_COOKIE_LENGTH];
unsigned char seq[SEQ_NUM_SIZE];
unsigned char *data, *p, *buf;
unsigned long reclen, fragoff, fraglen, msglen;
unsigned int rectype, versmajor, msgseq, msgtype, clientvers, cookielen;
BIO *rbio, *wbio;
BUF_MEM *bufm;
struct sockaddr_storage tmpclient;
PACKET pkt, msgpkt, msgpayload, session, cookiepkt;
/* Ensure there is no state left over from a previous invocation */
if (!SSL_clear(s))
return -1;
ERR_clear_error();
rbio = SSL_get_rbio(s);
wbio = SSL_get_wbio(s);
if(!rbio || !wbio) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_BIO_NOT_SET);
return -1;
}
/*
* We only peek at incoming ClientHello's until we're sure we are going to
* to respond with a HelloVerifyRequest. If its a ClientHello with a valid
* cookie then we leave it in the BIO for dtls1_accept to handle.
*/
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
/*
* Note: This check deliberately excludes DTLS1_BAD_VER because that version
* requires the MAC to be calculated *including* the first ClientHello
* (without the cookie). Since DTLSv1_listen is stateless that cannot be
* supported. DTLS1_BAD_VER must use cookies in a stateful manner (e.g. via
* SSL_accept)
*/
if ((s->version & 0xff00) != (DTLS1_VERSION & 0xff00)) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNSUPPORTED_SSL_VERSION);
return -1;
}
if (s->init_buf == NULL) {
if ((bufm = BUF_MEM_new()) == NULL) {
SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_MALLOC_FAILURE);
return -1;
}
if (!BUF_MEM_grow(bufm, SSL3_RT_MAX_PLAIN_LENGTH)) {
BUF_MEM_free(bufm);
SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_MALLOC_FAILURE);
return -1;
}
s->init_buf = bufm;
}
buf = (unsigned char *)s->init_buf->data;
do {
/* Get a packet */
clear_sys_error();
/*
* Technically a ClientHello could be SSL3_RT_MAX_PLAIN_LENGTH
* + DTLS1_RT_HEADER_LENGTH bytes long. Normally init_buf does not store
* the record header as well, but we do here. We've set up init_buf to
* be the standard size for simplicity. In practice we shouldn't ever
* receive a ClientHello as long as this. If we do it will get dropped
* in the record length check below.
*/
n = BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
if (n <= 0) {
if(BIO_should_retry(rbio)) {
/* Non-blocking IO */
goto end;
}
return -1;
}
/* If we hit any problems we need to clear this packet from the BIO */
clearpkt = 1;
if (!PACKET_buf_init(&pkt, buf, n)) {
SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_INTERNAL_ERROR);
return -1;
}
/*
* Parse the received record. If there are any problems with it we just
* dump it - with no alert. RFC6347 says this "Unlike TLS, DTLS is
* resilient in the face of invalid records (e.g., invalid formatting,
* length, MAC, etc.). In general, invalid records SHOULD be silently
* discarded, thus preserving the association; however, an error MAY be
* logged for diagnostic purposes."
*/
/* this packet contained a partial record, dump it */
if (n < DTLS1_RT_HEADER_LENGTH) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_RECORD_TOO_SMALL);
goto end;
}
if (s->msg_callback)
s->msg_callback(0, 0, SSL3_RT_HEADER, buf,
DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
/* Get the record header */
if (!PACKET_get_1(&pkt, &rectype)
|| !PACKET_get_1(&pkt, &versmajor)) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
if (rectype != SSL3_RT_HANDSHAKE) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
goto end;
}
/*
* Check record version number. We only check that the major version is
* the same.
*/
if (versmajor != DTLS1_VERSION_MAJOR) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_BAD_PROTOCOL_VERSION_NUMBER);
goto end;
}
if (!PACKET_forward(&pkt, 1)
/* Save the sequence number: 64 bits, with top 2 bytes = epoch */
|| !PACKET_copy_bytes(&pkt, seq, SEQ_NUM_SIZE)
|| !PACKET_get_length_prefixed_2(&pkt, &msgpkt)
|| PACKET_remaining(&pkt) != 0) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
/* This is an initial ClientHello so the epoch has to be 0 */
if (seq[0] != 0 || seq[1] != 0) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
goto end;
}
/* Get a pointer to the raw message for the later callback */
data = PACKET_data(&msgpkt);
/* Finished processing the record header, now process the message */
if (!PACKET_get_1(&msgpkt, &msgtype)
|| !PACKET_get_net_3(&msgpkt, &msglen)
|| !PACKET_get_net_2(&msgpkt, &msgseq)
|| !PACKET_get_net_3(&msgpkt, &fragoff)
|| !PACKET_get_net_3(&msgpkt, &fraglen)
|| !PACKET_get_sub_packet(&msgpkt, &msgpayload, msglen)
|| PACKET_remaining(&msgpkt) != 0) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
if (msgtype != SSL3_MT_CLIENT_HELLO) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
goto end;
}
/* Message sequence number can only be 0 or 1 */
if(msgseq > 2) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_INVALID_SEQUENCE_NUMBER);
goto end;
}
/* We don't support a fragmented ClientHello whilst listening */
if (fragoff != 0 || fraglen != msglen) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_FRAGMENTED_CLIENT_HELLO);
goto end;
}
if (s->msg_callback)
s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, data,
msglen + DTLS1_HM_HEADER_LENGTH, s,
s->msg_callback_arg);
if (!PACKET_get_net_2(&msgpayload, &clientvers)) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
/*
* Verify client version is supported
*/
if ((clientvers > (unsigned int)s->method->version &&
s->method->version != DTLS_ANY_VERSION)) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_WRONG_VERSION_NUMBER);
goto end;
}
if (!PACKET_forward(&msgpayload, SSL3_RANDOM_SIZE)
|| !PACKET_get_length_prefixed_1(&msgpayload, &session)
|| !PACKET_get_length_prefixed_1(&msgpayload, &cookiepkt)) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
/*
* Check if we have a cookie or not. If not we need to send a
* HelloVerifyRequest.
*/
if (PACKET_remaining(&cookiepkt) == 0) {
next = LISTEN_SEND_VERIFY_REQUEST;
} else {
/*
* We have a cookie, so lets check it.
*/
if (s->ctx->app_verify_cookie_cb == NULL) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_NO_VERIFY_COOKIE_CALLBACK);
/* This is fatal */
return -1;
}
if (PACKET_remaining(&cookiepkt) > sizeof(s->d1->rcvd_cookie)
|| s->ctx->app_verify_cookie_cb(s, PACKET_data(&cookiepkt),
PACKET_remaining(&cookiepkt)) == 0) {
/*
* We treat invalid cookies in the same was as no cookie as
* per RFC6347
*/
next = LISTEN_SEND_VERIFY_REQUEST;
} else {
/* Cookie verification succeeded */
next = LISTEN_SUCCESS;
}
}
if (next == LISTEN_SEND_VERIFY_REQUEST) {
/*
* There was no cookie in the ClientHello so we need to send a
* HelloVerifyRequest. If this fails we do not worry about trying
* to resend, we just drop it.
*/
/*
* Dump the read packet, we don't need it any more. Ignore return
* value
*/
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 1, NULL);
/* Generate the cookie */
if (s->ctx->app_gen_cookie_cb == NULL ||
s->ctx->app_gen_cookie_cb(s, cookie, &cookielen) == 0) {
SSLerr(SSL_F_DTLS1_LISTEN, SSL_R_COOKIE_GEN_CALLBACK_FAILURE);
/* This is fatal */
return -1;
}
p = &buf[DTLS1_RT_HEADER_LENGTH];
msglen = dtls1_raw_hello_verify_request(p + DTLS1_HM_HEADER_LENGTH,
cookie, cookielen);
*p++ = DTLS1_MT_HELLO_VERIFY_REQUEST;
/* Message length */
l2n3(msglen, p);
/* Message sequence number is always 0 for a HelloVerifyRequest */
s2n(0, p);
/*
* We never fragment a HelloVerifyRequest, so fragment offset is 0
* and fragment length is message length
*/
l2n3(0, p);
l2n3(msglen, p);
/* Set reclen equal to length of whole handshake message */
reclen = msglen + DTLS1_HM_HEADER_LENGTH;
/* Add the record header */
p = buf;
*(p++) = SSL3_RT_HANDSHAKE;
/*
* Special case: for hello verify request, client version 1.0 and we
* haven't decided which version to use yet send back using version
* 1.0 header: otherwise some clients will ignore it.
*/
if (s->method->version == DTLS_ANY_VERSION) {
*(p++) = DTLS1_VERSION >> 8;
*(p++) = DTLS1_VERSION & 0xff;
} else {
*(p++) = s->version >> 8;
*(p++) = s->version & 0xff;
}
/*
* Record sequence number is always the same as in the received
* ClientHello
*/
memcpy(p, seq, SEQ_NUM_SIZE);
p += SEQ_NUM_SIZE;
/* Length */
s2n(reclen, p);
/*
* Set reclen equal to length of whole record including record
* header
*/
reclen += DTLS1_RT_HEADER_LENGTH;
if (s->msg_callback)
s->msg_callback(1, 0, SSL3_RT_HEADER, buf,
DTLS1_RT_HEADER_LENGTH, s, s->msg_callback_arg);
/*
* This is unneccessary if rbio and wbio are one and the same - but
* maybe they're not.
*/
if(BIO_dgram_get_peer(rbio, &tmpclient) <= 0
|| BIO_dgram_set_peer(wbio, &tmpclient) <= 0) {
SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_INTERNAL_ERROR);
goto end;
}
if (BIO_write(wbio, buf, reclen) < (int)reclen) {
if(BIO_should_retry(wbio)) {
/*
* Non-blocking IO...but we're stateless, so we're just
* going to drop this packet.
*/
goto end;
}
return -1;
}
if (BIO_flush(wbio) <= 0) {
if(BIO_should_retry(wbio)) {
/*
* Non-blocking IO...but we're stateless, so we're just
* going to drop this packet.
*/
goto end;
}
return -1;
}
}
} while (next != LISTEN_SUCCESS);
/*
* Set expected sequence numbers to continue the handshake.
*/
s->d1->handshake_read_seq = 1;
s->d1->handshake_write_seq = 1;
s->d1->next_handshake_write_seq = 1;
DTLS_RECORD_LAYER_set_write_sequence(&s->rlayer, seq);
/*
* We are doing cookie exchange, so make sure we set that option in the
* SSL object
*/
SSL_set_options(s, SSL_OP_COOKIE_EXCHANGE);
/*
* Put us into the "init" state so that dtls1_accept doesn't clear our
* state
*/
s->state = SSL_ST_ACCEPT;
if(BIO_dgram_get_peer(rbio, client) <= 0) {
SSLerr(SSL_F_DTLS1_LISTEN, ERR_R_INTERNAL_ERROR);
return -1;
}
ret = 1;
clearpkt = 0;
end:
BIO_ctrl(SSL_get_rbio(s), BIO_CTRL_DGRAM_SET_PEEK_MODE, 0, NULL);
if (clearpkt) {
/* Dump this packet. Ignore return value */
BIO_read(rbio, buf, SSL3_RT_MAX_PLAIN_LENGTH);
}
return ret;
}
static int dtls1_set_handshake_header(SSL *s, int htype, unsigned long len)
{
unsigned char *p = (unsigned char *)s->init_buf->data;
dtls1_set_message_header(s, p, htype, len, 0, len);
s->init_num = (int)len + DTLS1_HM_HEADER_LENGTH;
s->init_off = 0;
/* Buffer the message to handle re-xmits */
if (!dtls1_buffer_message(s, 0))
return 0;
return 1;
}
static int dtls1_handshake_write(SSL *s)
{
return dtls1_do_write(s, SSL3_RT_HANDSHAKE);
}
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