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openssl/ssl/d1_lib.c
Matt Caswell f5c7f5dfba Fix DTLS buffered message DoS attack 
DTLS can handle out of order record delivery. Additionally since
handshake messages can be bigger than will fit into a single packet, the
messages can be fragmented across multiple records (as with normal TLS).
That means that the messages can arrive mixed up, and we have to
reassemble them. We keep a queue of buffered messages that are "from the
future", i.e. messages we're not ready to deal with yet but have arrived
early. The messages held there may not be full yet - they could be one
or more fragments that are still in the process of being reassembled.

The code assumes that we will eventually complete the reassembly and
when that occurs the complete message is removed from the queue at the
point that we need to use it.

However, DTLS is also tolerant of packet loss. To get around that DTLS
messages can be retransmitted. If we receive a full (non-fragmented)
message from the peer after previously having received a fragment of
that message, then we ignore the message in the queue and just use the
non-fragmented version. At that point the queued message will never get
removed.

Additionally the peer could send "future" messages that we never get to
in order to complete the handshake. Each message has a sequence number
(starting from 0). We will accept a message fragment for the current
message sequence number, or for any sequence up to 10 into the future.
However if the Finished message has a sequence number of 2, anything
greater than that in the queue is just left there.

So, in those two ways we can end up with "orphaned" data in the queue
that will never get removed - except when the connection is closed. At
that point all the queues are flushed.

An attacker could seek to exploit this by filling up the queues with
lots of large messages that are never going to be used in order to
attempt a DoS by memory exhaustion.

I will assume that we are only concerned with servers here. It does not
seem reasonable to be concerned about a memory exhaustion attack on a
client. They are unlikely to process enough connections for this to be
an issue.

A "long" handshake with many messages might be 5 messages long (in the
incoming direction), e.g. ClientHello, Certificate, ClientKeyExchange,
CertificateVerify, Finished. So this would be message sequence numbers 0
to 4. Additionally we can buffer up to 10 messages in the future.
Therefore the maximum number of messages that an attacker could send
that could get orphaned would typically be 15.

The maximum size that a DTLS message is allowed to be is defined by
max_cert_list, which by default is 100k. Therefore the maximum amount of
"orphaned" memory per connection is 1500k.

Message sequence numbers get reset after the Finished message, so
renegotiation will not extend the maximum number of messages that can be
orphaned per connection.

As noted above, the queues do get cleared when the connection is closed.
Therefore in order to mount an effective attack, an attacker would have
to open many simultaneous connections.

Issue reported by Quan Luo.

CVE-2016-2179

Reviewed-by: Richard Levitte <levitte@openssl.org>
2016-08-22 10:53:55 +01:00

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/*
* Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include <stdio.h>
#define USE_SOCKETS
#include <openssl/objects.h>
#include <openssl/rand.h>
#include "ssl_locl.h"
#if defined(OPENSSL_SYS_VMS)
# include <sys/timeb.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);
static unsigned int dtls1_link_min_mtu(void);
/* XDTLS: figure out the right values */
static const unsigned int g_probable_mtu[] = { 1500, 512, 256 };
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,
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,
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 == NULL || d1->sent_messages == NULL) {
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)
{
dtls1_clear_received_buffer(s);
dtls1_clear_sent_buffer(s);
}
void dtls1_clear_received_buffer(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);
}
}
void dtls1_clear_sent_buffer(SSL *s)
{
pitem *item = NULL;
hm_fragment *frag = NULL;
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->method->version == DTLS_ANY_VERSION)
s->version = DTLS_MAX_VERSION;
#ifndef OPENSSL_NO_DTLS1_METHOD
else if (s->options & SSL_OP_CISCO_ANYCONNECT)
s->client_version = s->version = DTLS1_BAD_VER;
#endif
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_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);
}
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 divergences 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_sent_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);
/* re-bias to 1/1/1970 */
# ifdef __MINGW32__
now.ul -= 116444736000000000ULL;
# else
/* *INDENT-OFF* */
now.ul -= 116444736000000000UI64;
/* *INDENT-ON* */
# 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
#ifndef OPENSSL_NO_SOCK
int DTLSv1_listen(SSL *s, BIO_ADDR *client)
{
int next, n, ret = 0, clearpkt = 0;
unsigned char cookie[DTLS1_COOKIE_LENGTH];
unsigned char seq[SEQ_NUM_SIZE];
const unsigned char *data;
unsigned char *p, *buf;
unsigned long reclen, fragoff, fraglen, msglen;
unsigned int rectype, versmajor, msgseq, msgtype, clientvers, cookielen;
BIO *rbio, *wbio;
BUF_MEM *bufm;
BIO_ADDR *tmpclient = NULL;
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_DTLSV1_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 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_DTLSV1_LISTEN, SSL_R_UNSUPPORTED_SSL_VERSION);
return -1;
}
if (s->init_buf == NULL) {
if ((bufm = BUF_MEM_new()) == NULL) {
SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
return -1;
}
if (!BUF_MEM_grow(bufm, SSL3_RT_MAX_PLAIN_LENGTH)) {
BUF_MEM_free(bufm);
SSLerr(SSL_F_DTLSV1_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_DTLSV1_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_DTLSV1_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_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
if (rectype != SSL3_RT_HANDSHAKE) {
SSLerr(SSL_F_DTLSV1_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_DTLSV1_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)) {
SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
/*
* We allow data remaining at the end of the packet because there could
* be a second record (but we ignore it)
*/
/* This is an initial ClientHello so the epoch has to be 0 */
if (seq[0] != 0 || seq[1] != 0) {
SSLerr(SSL_F_DTLSV1_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, fraglen)
|| PACKET_remaining(&msgpkt) != 0) {
SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
if (msgtype != SSL3_MT_CLIENT_HELLO) {
SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_UNEXPECTED_MESSAGE);
goto end;
}
/* Message sequence number can only be 0 or 1 */
if (msgseq > 2) {
SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_INVALID_SEQUENCE_NUMBER);
goto end;
}
/*
* We don't support fragment reassembly for ClientHellos whilst
* listening because that would require server side state (which is
* against the whole point of the ClientHello/HelloVerifyRequest
* mechanism). Instead we only look at the first ClientHello fragment
* and require that the cookie must be contained within it.
*/
if (fragoff != 0 || fraglen > msglen) {
/* Non initial ClientHello fragment (or bad fragment) */
SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_FRAGMENTED_CLIENT_HELLO);
goto end;
}
if (s->msg_callback)
s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, data,
fraglen + DTLS1_HM_HEADER_LENGTH, s,
s->msg_callback_arg);
if (!PACKET_get_net_2(&msgpayload, &clientvers)) {
SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_LENGTH_MISMATCH);
goto end;
}
/*
* Verify client version is supported
*/
if (DTLS_VERSION_LT(clientvers, (unsigned int)s->method->version) &&
s->method->version != DTLS_ANY_VERSION) {
SSLerr(SSL_F_DTLSV1_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)) {
/*
* Could be malformed or the cookie does not fit within the initial
* ClientHello fragment. Either way we can't handle it.
*/
SSLerr(SSL_F_DTLSV1_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_DTLSV1_LISTEN, SSL_R_NO_VERIFY_COOKIE_CALLBACK);
/* This is fatal */
return -1;
}
if (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 ||
cookielen > 255) {
SSLerr(SSL_F_DTLSV1_LISTEN, SSL_R_COOKIE_GEN_CALLBACK_FAILURE);
/* This is fatal */
return -1;
}
p = &buf[DTLS1_RT_HEADER_LENGTH];
msglen = dtls_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);
if ((tmpclient = BIO_ADDR_new()) == NULL) {
SSLerr(SSL_F_DTLSV1_LISTEN, ERR_R_MALLOC_FAILURE);
goto end;
}
/*
* This is unnecessary if rbio and wbio are one and the same - but
* maybe they're not. We ignore errors here - some BIOs do not
* support this.
*/
if (BIO_dgram_get_peer(rbio, tmpclient) > 0) {
(void)BIO_dgram_set_peer(wbio, tmpclient);
}
BIO_ADDR_free(tmpclient);
tmpclient = NULL;
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);
/*
* Tell the state machine that we've done the initial hello verify
* exchange
*/
ossl_statem_set_hello_verify_done(s);
/*
* Some BIOs may not support this. If we fail we clear the client address
*/
if (BIO_dgram_get_peer(rbio, client) <= 0)
BIO_ADDR_clear(client);
ret = 1;
clearpkt = 0;
end:
BIO_ADDR_free(tmpclient);
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;
}
#endif
static int dtls1_set_handshake_header(SSL *s, int htype, unsigned long len)
{
dtls1_set_message_header(s, 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);
}
#ifndef OPENSSL_NO_HEARTBEATS
# define HEARTBEAT_SIZE(payload, padding) ( \
1 /* heartbeat type */ + \
2 /* heartbeat length */ + \
(payload) + (padding))
# define HEARTBEAT_SIZE_STD(payload) HEARTBEAT_SIZE(payload, 16)
int dtls1_process_heartbeat(SSL *s, unsigned char *p, unsigned int length)
{
unsigned char *pl;
unsigned short hbtype;
unsigned int payload;
unsigned int padding = 16; /* Use minimum padding */
if (s->msg_callback)
s->msg_callback(0, s->version, DTLS1_RT_HEARTBEAT,
p, length, s, s->msg_callback_arg);
/* Read type and payload length */
if (HEARTBEAT_SIZE_STD(0) > length)
return 0; /* silently discard */
if (length > SSL3_RT_MAX_PLAIN_LENGTH)
return 0; /* silently discard per RFC 6520 sec. 4 */
hbtype = *p++;
n2s(p, payload);
if (HEARTBEAT_SIZE_STD(payload) > length)
return 0; /* silently discard per RFC 6520 sec. 4 */
pl = p;
if (hbtype == TLS1_HB_REQUEST) {
unsigned char *buffer, *bp;
unsigned int write_length = HEARTBEAT_SIZE(payload, padding);
int r;
if (write_length > SSL3_RT_MAX_PLAIN_LENGTH)
return 0;
/* Allocate memory for the response. */
buffer = OPENSSL_malloc(write_length);
if (buffer == NULL)
return -1;
bp = buffer;
/* Enter response type, length and copy payload */
*bp++ = TLS1_HB_RESPONSE;
s2n(payload, bp);
memcpy(bp, pl, payload);
bp += payload;
/* Random padding */
if (RAND_bytes(bp, padding) <= 0) {
OPENSSL_free(buffer);
return -1;
}
r = dtls1_write_bytes(s, DTLS1_RT_HEARTBEAT, buffer, write_length);
if (r >= 0 && s->msg_callback)
s->msg_callback(1, s->version, DTLS1_RT_HEARTBEAT,
buffer, write_length, s, s->msg_callback_arg);
OPENSSL_free(buffer);
if (r < 0)
return r;
} else if (hbtype == TLS1_HB_RESPONSE) {
unsigned int seq;
/*
* We only send sequence numbers (2 bytes unsigned int), and 16
* random bytes, so we just try to read the sequence number
*/
n2s(pl, seq);
if (payload == 18 && seq == s->tlsext_hb_seq) {
dtls1_stop_timer(s);
s->tlsext_hb_seq++;
s->tlsext_hb_pending = 0;
}
}
return 0;
}
int dtls1_heartbeat(SSL *s)
{
unsigned char *buf, *p;
int ret = -1;
unsigned int payload = 18; /* Sequence number + random bytes */
unsigned int padding = 16; /* Use minimum padding */
unsigned int size;
/* Only send if peer supports and accepts HB requests... */
if (!(s->tlsext_heartbeat & SSL_DTLSEXT_HB_ENABLED) ||
s->tlsext_heartbeat & SSL_DTLSEXT_HB_DONT_SEND_REQUESTS) {
SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_TLS_HEARTBEAT_PEER_DOESNT_ACCEPT);
return -1;
}
/* ...and there is none in flight yet... */
if (s->tlsext_hb_pending) {
SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_TLS_HEARTBEAT_PENDING);
return -1;
}
/* ...and no handshake in progress. */
if (SSL_in_init(s) || ossl_statem_get_in_handshake(s)) {
SSLerr(SSL_F_DTLS1_HEARTBEAT, SSL_R_UNEXPECTED_MESSAGE);
return -1;
}
/*-
* Create HeartBeat message, we just use a sequence number
* as payload to distinguish different messages and add
* some random stuff.
*/
size = HEARTBEAT_SIZE(payload, padding);
buf = OPENSSL_malloc(size);
if (buf == NULL) {
SSLerr(SSL_F_DTLS1_HEARTBEAT, ERR_R_MALLOC_FAILURE);
return -1;
}
p = buf;
/* Message Type */
*p++ = TLS1_HB_REQUEST;
/* Payload length (18 bytes here) */
s2n(payload, p);
/* Sequence number */
s2n(s->tlsext_hb_seq, p);
/* 16 random bytes */
if (RAND_bytes(p, 16) <= 0) {
SSLerr(SSL_F_DTLS1_HEARTBEAT, ERR_R_INTERNAL_ERROR);
goto err;
}
p += 16;
/* Random padding */
if (RAND_bytes(p, padding) <= 0) {
SSLerr(SSL_F_DTLS1_HEARTBEAT, ERR_R_INTERNAL_ERROR);
goto err;
}
ret = dtls1_write_bytes(s, DTLS1_RT_HEARTBEAT, buf, size);
if (ret >= 0) {
if (s->msg_callback)
s->msg_callback(1, s->version, DTLS1_RT_HEARTBEAT,
buf, size, s, s->msg_callback_arg);
dtls1_start_timer(s);
s->tlsext_hb_pending = 1;
}
err:
OPENSSL_free(buf);
return ret;
}
#endif
int dtls1_shutdown(SSL *s)
{
int ret;
#ifndef OPENSSL_NO_SCTP
BIO *wbio;
wbio = SSL_get_wbio(s);
if (wbio != NULL && BIO_dgram_is_sctp(wbio) &&
!(s->shutdown & SSL_SENT_SHUTDOWN)) {
ret = BIO_dgram_sctp_wait_for_dry(wbio);
if (ret < 0)
return -1;
if (ret == 0)
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 1,
NULL);
}
#endif
ret = ssl3_shutdown(s);
#ifndef OPENSSL_NO_SCTP
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SCTP_SAVE_SHUTDOWN, 0, NULL);
#endif
return ret;
}
int dtls1_query_mtu(SSL *s)
{
if (s->d1->link_mtu) {
s->d1->mtu =
s->d1->link_mtu - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
s->d1->link_mtu = 0;
}
/* AHA! Figure out the MTU, and stick to the right size */
if (s->d1->mtu < dtls1_min_mtu(s)) {
if (!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) {
s->d1->mtu =
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
/*
* I've seen the kernel return bogus numbers when it doesn't know
* (initial write), so just make sure we have a reasonable number
*/
if (s->d1->mtu < dtls1_min_mtu(s)) {
/* Set to min mtu */
s->d1->mtu = dtls1_min_mtu(s);
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
s->d1->mtu, NULL);
}
} else
return 0;
}
return 1;
}
static unsigned int dtls1_link_min_mtu(void)
{
return (g_probable_mtu[(sizeof(g_probable_mtu) /
sizeof(g_probable_mtu[0])) - 1]);
}
unsigned int dtls1_min_mtu(SSL *s)
{
return dtls1_link_min_mtu() - BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
}
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