/*
* Copyright (C) 2009-2012 Free Software Foundation, Inc.
* Copyright (C) 2013 Nikos Mavrogiannopoulos
*
* Authors: Jonathan Bastien-Filiatrault
* Nikos Mavrogiannopoulos
*
* This file is part of GNUTLS.
*
* The GNUTLS library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library 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 program. If not, see <https://www.gnu.org/licenses/>
*
*/
/* Functions that relate to DTLS retransmission and reassembly.
*/
#include "gnutls_int.h"
#include "errors.h"
#include "debug.h"
#include "dtls.h"
#include "record.h"
#include <mbuffers.h>
#include <buffers.h>
#include <constate.h>
#include <state.h>
#include <gnutls/dtls.h>
#include <algorithms.h>
void _dtls_async_timer_delete(gnutls_session_t session)
{
if (session->internals.dtls.async_term != 0) {
_gnutls_dtls_log
("DTLS[%p]: Deinitializing previous handshake state.\n",
session);
session->internals.dtls.async_term = 0; /* turn off "timer" */
_dtls_reset_hsk_state(session);
_gnutls_handshake_io_buffer_clear(session);
_gnutls_epoch_gc(session);
}
}
/* This function fragments and transmits a previously buffered
* outgoing message. It accepts mtu_data which is a buffer to
* be reused (should be set to NULL initially).
*/
static inline int
transmit_message(gnutls_session_t session,
mbuffer_st * bufel, uint8_t ** buf)
{
uint8_t *data, *mtu_data;
int ret = 0;
unsigned int offset, frag_len, data_size;
unsigned int mtu =
gnutls_dtls_get_data_mtu(session);
if (session->security_parameters.max_record_send_size < mtu)
mtu = session->security_parameters.max_record_send_size;
mtu -= DTLS_HANDSHAKE_HEADER_SIZE;
if (bufel->type == GNUTLS_CHANGE_CIPHER_SPEC) {
_gnutls_dtls_log
("DTLS[%p]: Sending Packet[%u] fragment %s(%d), mtu %u\n",
session, bufel->handshake_sequence,
_gnutls_handshake2str(bufel->htype), bufel->htype, mtu);
return _gnutls_send_int(session, bufel->type, -1,
bufel->epoch,
_mbuffer_get_uhead_ptr(bufel),
_mbuffer_get_uhead_size(bufel), 0);
}
if (*buf == NULL)
*buf = gnutls_malloc(mtu + DTLS_HANDSHAKE_HEADER_SIZE);
if (*buf == NULL)
return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);
mtu_data = *buf;
data = _mbuffer_get_udata_ptr(bufel);
data_size = _mbuffer_get_udata_size(bufel);
/* Write fixed headers
*/
/* Handshake type */
mtu_data[0] = (uint8_t) bufel->htype;
/* Total length */
_gnutls_write_uint24(data_size, &mtu_data[1]);
/* Handshake sequence */
_gnutls_write_uint16(bufel->handshake_sequence, &mtu_data[4]);
/* Chop up and send handshake message into mtu-size pieces. */
for (offset = 0; offset <= data_size; offset += mtu) {
/* Calculate fragment length */
if (offset + mtu > data_size)
frag_len = data_size - offset;
else
frag_len = mtu;
/* we normally allow fragments of zero length, to allow
* the packets which have zero size. On the others don't
* send such fragments */
if (frag_len == 0 && data_size > 0) {
ret = 0;
break;
}
/* Fragment offset */
_gnutls_write_uint24(offset, &mtu_data[6]);
/* Fragment length */
_gnutls_write_uint24(frag_len, &mtu_data[9]);
memcpy(&mtu_data[DTLS_HANDSHAKE_HEADER_SIZE],
data + offset, frag_len);
_gnutls_dtls_log
("DTLS[%p]: Sending Packet[%u] fragment %s(%d) with "
"length: %u, offset: %u, fragment length: %u, mtu: %u\n",
session, bufel->handshake_sequence,
_gnutls_handshake2str(bufel->htype), bufel->htype,
data_size, offset, frag_len, mtu);
ret = _gnutls_send_int(session, bufel->type, bufel->htype,
bufel->epoch, mtu_data,
DTLS_HANDSHAKE_HEADER_SIZE +
frag_len, 0);
if (ret < 0) {
gnutls_assert();
break;
}
}
return ret;
}
static int drop_usage_count(gnutls_session_t session,
mbuffer_head_st * const send_buffer)
{
int ret;
mbuffer_st *cur;
for (cur = send_buffer->head; cur != NULL; cur = cur->next) {
ret = _gnutls_epoch_refcount_dec(session, cur->epoch);
if (ret < 0)
return gnutls_assert_val(ret);
}
return 0;
}
/* Checks whether the received packet contains a handshake
* packet with sequence higher that the previously received.
* It must be called only when an actual packet has been
* received.
*
* Returns: 0 if expected, negative value otherwise.
*/
static int is_next_hpacket_expected(gnutls_session_t session)
{
int ret;
/* htype is arbitrary */
ret =
_gnutls_recv_in_buffers(session, GNUTLS_HANDSHAKE,
GNUTLS_HANDSHAKE_FINISHED, 0);
if (ret < 0)
return gnutls_assert_val(ret);
ret = _gnutls_parse_record_buffered_msgs(session);
if (ret < 0)
return gnutls_assert_val(ret);
if (session->internals.handshake_recv_buffer_size > 0)
return 0;
else
return
gnutls_assert_val
(GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET);
}
void _dtls_reset_hsk_state(gnutls_session_t session)
{
session->internals.dtls.flight_init = 0;
drop_usage_count(session,
&session->internals.handshake_send_buffer);
_mbuffer_head_clear(&session->internals.handshake_send_buffer);
}
#define UPDATE_TIMER { \
session->internals.dtls.actual_retrans_timeout_ms *= 2; \
session->internals.dtls.actual_retrans_timeout_ms %= MAX_DTLS_TIMEOUT; \
}
#define RESET_TIMER \
session->internals.dtls.actual_retrans_timeout_ms = session->internals.dtls.retrans_timeout_ms
#define TIMER_WINDOW session->internals.dtls.actual_retrans_timeout_ms
/* This function transmits the flight that has been previously
* buffered.
*
* This function is called from the handshake layer and calls the
* record layer.
*/
int _dtls_transmit(gnutls_session_t session)
{
int ret;
uint8_t *buf = NULL;
unsigned int timeout;
/* PREPARING -> SENDING state transition */
mbuffer_head_st *const send_buffer =
&session->internals.handshake_send_buffer;
mbuffer_st *cur;
gnutls_handshake_description_t last_type = 0;
unsigned int diff;
struct timespec now;
gnutls_gettime(&now);
/* If we have already sent a flight and we are operating in a
* non blocking way, check if it is time to retransmit or just
* return.
*/
if (session->internals.dtls.flight_init != 0
&& (session->internals.flags & GNUTLS_NONBLOCK)) {
/* just in case previous run was interrupted */
ret = _gnutls_io_write_flush(session);
if (ret < 0) {
gnutls_assert();
goto cleanup;
}
if (session->internals.dtls.last_flight == 0
|| !_dtls_is_async(session)) {
/* check for ACK */
ret = _gnutls_io_check_recv(session, 0);
if (ret == GNUTLS_E_TIMEDOUT) {
/* if no retransmission is required yet just return
*/
if (timespec_sub_ms
(&now,
&session->internals.dtls.
last_retransmit) < TIMER_WINDOW) {
gnutls_assert();
goto nb_timeout;
}
} else { /* received something */
if (ret == 0) {
ret =
is_next_hpacket_expected
(session);
if (ret == GNUTLS_E_AGAIN
|| ret == GNUTLS_E_INTERRUPTED)
goto nb_timeout;
if (ret < 0
&& ret !=
GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET)
{
gnutls_assert();
goto cleanup;
}
if (ret == 0)
goto end_flight;
/* if ret == GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET retransmit */
} else
goto nb_timeout;
}
}
}
do {
timeout = TIMER_WINDOW;
diff =
timespec_sub_ms(&now,
&session->internals.handshake_start_time);
if (diff >= session->internals.handshake_timeout_ms) {
_gnutls_dtls_log("Session timeout: %u ms\n", diff);
ret = gnutls_assert_val(GNUTLS_E_TIMEDOUT);
goto end_flight;
}
diff =
timespec_sub_ms(&now,
&session->internals.dtls.
last_retransmit);
if (session->internals.dtls.flight_init == 0
|| diff >= TIMER_WINDOW) {
_gnutls_dtls_log
("DTLS[%p]: %sStart of flight transmission.\n",
session,
(session->internals.dtls.flight_init ==
0) ? "" : "re-");
for (cur = send_buffer->head; cur != NULL;
cur = cur->next) {
ret = transmit_message(session, cur, &buf);
if (ret < 0) {
gnutls_assert();
goto end_flight;
}
last_type = cur->htype;
}
gnutls_gettime(&session->internals.dtls.last_retransmit);
if (session->internals.dtls.flight_init == 0) {
session->internals.dtls.flight_init = 1;
RESET_TIMER;
timeout = TIMER_WINDOW;
if (last_type == GNUTLS_HANDSHAKE_FINISHED) {
/* On the last flight we cannot ensure retransmission
* from here. _dtls_wait_and_retransmit() is being called
* by handshake.
*/
session->internals.dtls.
last_flight = 1;
} else
session->internals.dtls.
last_flight = 0;
} else {
UPDATE_TIMER;
}
}
ret = _gnutls_io_write_flush(session);
if (ret < 0) {
ret = gnutls_assert_val(ret);
goto cleanup;
}
/* last message in handshake -> no ack */
if (session->internals.dtls.last_flight != 0) {
/* we don't wait here. We just return 0 and
* if a retransmission occurs because peer didn't receive it
* we rely on the record or handshake
* layer calling this function again.
*/
ret = 0;
goto cleanup;
} else { /* all other messages -> implicit ack (receive of next flight) */
if (!(session->internals.flags & GNUTLS_NONBLOCK))
ret =
_gnutls_io_check_recv(session,
timeout);
else {
ret = _gnutls_io_check_recv(session, 0);
if (ret == GNUTLS_E_TIMEDOUT) {
goto nb_timeout;
}
}
if (ret == 0) {
ret = is_next_hpacket_expected(session);
if (ret == GNUTLS_E_AGAIN
|| ret == GNUTLS_E_INTERRUPTED)
goto nb_timeout;
if (ret ==
GNUTLS_E_UNEXPECTED_HANDSHAKE_PACKET) {
ret = GNUTLS_E_TIMEDOUT;
goto keep_up;
}
if (ret < 0) {
gnutls_assert();
goto cleanup;
}
goto end_flight;
}
}
keep_up:
gnutls_gettime(&now);
} while (ret == GNUTLS_E_TIMEDOUT);
if (ret < 0) {
ret = gnutls_assert_val(ret);
goto end_flight;
}
ret = 0;
end_flight:
_gnutls_dtls_log("DTLS[%p]: End of flight transmission.\n",
session);
_dtls_reset_hsk_state(session);
cleanup:
if (buf != NULL)
gnutls_free(buf);
/* SENDING -> WAITING state transition */
return ret;
nb_timeout:
if (buf != NULL)
gnutls_free(buf);
RETURN_DTLS_EAGAIN_OR_TIMEOUT(session, ret);
}
/* Waits for the last flight or retransmits
* the previous on timeout. Returns 0 on success.
*/
int _dtls_wait_and_retransmit(gnutls_session_t session)
{
int ret;
if (!(session->internals.flags & GNUTLS_NONBLOCK))
ret = _gnutls_io_check_recv(session, TIMER_WINDOW);
else
ret = _gnutls_io_check_recv(session, 0);
if (ret == GNUTLS_E_TIMEDOUT) {
ret = _dtls_retransmit(session);
if (ret == 0) {
RETURN_DTLS_EAGAIN_OR_TIMEOUT(session, 0);
} else
return gnutls_assert_val(ret);
}
RESET_TIMER;
return 0;
}
/**
* gnutls_dtls_set_timeouts:
* @session: is a #gnutls_session_t type.
* @retrans_timeout: The time at which a retransmission will occur in milliseconds
* @total_timeout: The time at which the connection will be aborted, in milliseconds.
*
* This function will set the timeouts required for the DTLS handshake
* protocol. The retransmission timeout is the time after which a
* message from the peer is not received, the previous messages will
* be retransmitted. The total timeout is the time after which the
* handshake will be aborted with %GNUTLS_E_TIMEDOUT.
*
* The DTLS protocol recommends the values of 1 sec and 60 seconds
* respectively, and these are the default values.
*
* To disable retransmissions set a @retrans_timeout larger than the @total_timeout.
*
* Since: 3.0
**/
void gnutls_dtls_set_timeouts(gnutls_session_t session,
unsigned int retrans_timeout,
unsigned int total_timeout)
{
if (total_timeout == GNUTLS_INDEFINITE_TIMEOUT)
session->internals.handshake_timeout_ms = 0;
else
session->internals.handshake_timeout_ms = total_timeout;
session->internals.dtls.retrans_timeout_ms = retrans_timeout;
}
/**
* gnutls_dtls_set_mtu:
* @session: is a #gnutls_session_t type.
* @mtu: The maximum transfer unit of the transport
*
* This function will set the maximum transfer unit of the transport
* that DTLS packets are sent over. Note that this should exclude
* the IP (or IPv6) and UDP headers. So for DTLS over IPv6 on an
* Ethernet device with MTU 1500, the DTLS MTU set with this function
* would be 1500 - 40 (IPV6 header) - 8 (UDP header) = 1452.
*
* Since: 3.0
**/
void gnutls_dtls_set_mtu(gnutls_session_t session, unsigned int mtu)
{
session->internals.dtls.mtu = MIN(mtu, DEFAULT_MAX_RECORD_SIZE);
}
/* when max is non-zero this function will return the maximum
* overhead that this ciphersuite may introduce, e.g., the maximum
* amount of padding required */
unsigned _gnutls_record_overhead(const version_entry_st *ver,
const cipher_entry_st *cipher,
const mac_entry_st *mac,
unsigned max)
{
int total = 0;
int ret;
int hash_len = 0;
if (unlikely(cipher == NULL))
return 0;
/* 1 octet content type in the unencrypted content */
if (ver->tls13_sem)
total++;
if (mac->id == GNUTLS_MAC_AEAD) {
if (!ver->tls13_sem)
total += _gnutls_cipher_get_explicit_iv_size(cipher);
total += _gnutls_cipher_get_tag_size(cipher);
} else {
/* STREAM + BLOCK have a MAC appended */
ret = _gnutls_mac_get_algo_len(mac);
if (unlikely(ret < 0))
return 0;
hash_len = ret;
total += hash_len;
}
/* Block ciphers have padding + IV */
if (_gnutls_cipher_type(cipher) == CIPHER_BLOCK) {
int exp_iv;
exp_iv = _gnutls_cipher_get_explicit_iv_size(cipher);
if (max)
total += 2*exp_iv; /* block == iv size */
else
total += exp_iv + 1;
}
return total;
}
/**
* gnutls_est_record_overhead_size:
* @version: is a #gnutls_protocol_t value
* @cipher: is a #gnutls_cipher_algorithm_t value
* @mac: is a #gnutls_mac_algorithm_t value
* @comp: is a #gnutls_compression_method_t value (ignored)
* @flags: must be zero
*
* This function will return the set size in bytes of the overhead
* due to TLS (or DTLS) per record.
*
* Note that this function may provide inacurate values when TLS
* extensions that modify the record format are negotiated. In these
* cases a more accurate value can be obtained using gnutls_record_overhead_size()
* after a completed handshake.
*
* Since: 3.2.2
**/
size_t gnutls_est_record_overhead_size(gnutls_protocol_t version,
gnutls_cipher_algorithm_t cipher,
gnutls_mac_algorithm_t mac,
gnutls_compression_method_t comp,
unsigned int flags)
{
const cipher_entry_st *c;
const mac_entry_st *m;
const version_entry_st *v;
size_t total = 0;
c = cipher_to_entry(cipher);
if (c == NULL)
return 0;
m = mac_to_entry(mac);
if (m == NULL)
return 0;
v = version_to_entry(version);
if (v == NULL)
return 0;
if (v->transport == GNUTLS_STREAM)
total = TLS_RECORD_HEADER_SIZE;
else
total = DTLS_RECORD_HEADER_SIZE;
total += _gnutls_record_overhead(v, c, m, 1);
return total;
}
/* returns overhead imposed by the record layer (encryption/compression)
* etc. It does not include the record layer headers, since the caller
* needs to cope with rounding to multiples of blocksize, and the header
* is outside that.
*
* blocksize: will contain the block size when padding may be required or 1
*
* It may return a negative error code on error.
*/
static int record_overhead_rt(gnutls_session_t session)
{
record_parameters_st *params;
int ret;
if (session->internals.initial_negotiation_completed == 0)
return GNUTLS_E_INVALID_REQUEST;
ret = _gnutls_epoch_get(session, EPOCH_WRITE_CURRENT, ¶ms);
if (ret < 0)
return gnutls_assert_val(ret);
return _gnutls_record_overhead(get_version(session), params->cipher, params->mac, 1);
}
/**
* gnutls_record_overhead_size:
* @session: is #gnutls_session_t
*
* This function will return the size in bytes of the overhead
* due to TLS (or DTLS) per record. On certain occasions
* (e.g., CBC ciphers) the returned value is the maximum
* possible overhead.
*
* Since: 3.2.2
**/
size_t gnutls_record_overhead_size(gnutls_session_t session)
{
const version_entry_st *v = get_version(session);
int ret;
size_t total;
if (v->transport == GNUTLS_STREAM)
total = TLS_RECORD_HEADER_SIZE;
else
total = DTLS_RECORD_HEADER_SIZE;
ret = record_overhead_rt(session);
if (ret >= 0)
total += ret;
return total;
}
/**
* gnutls_dtls_get_data_mtu:
* @session: is a #gnutls_session_t type.
*
* This function will return the actual maximum transfer unit for
* application data. I.e. DTLS headers are subtracted from the
* actual MTU which is set using gnutls_dtls_set_mtu().
*
* Returns: the maximum allowed transfer unit.
*
* Since: 3.0
**/
unsigned int gnutls_dtls_get_data_mtu(gnutls_session_t session)
{
int mtu = session->internals.dtls.mtu;
record_parameters_st *params;
int ret, k, hash_size, block;
mtu -= RECORD_HEADER_SIZE(session);
if (session->internals.initial_negotiation_completed == 0)
return mtu;
ret = _gnutls_epoch_get(session, EPOCH_WRITE_CURRENT, ¶ms);
if (ret < 0)
return mtu;
if (params->cipher->type == CIPHER_AEAD || params->cipher->type == CIPHER_STREAM)
return mtu-_gnutls_record_overhead(get_version(session), params->cipher, params->mac, 0);
/* CIPHER_BLOCK: in CBC ciphers guess the data MTU as it depends on residues
*/
hash_size = _gnutls_mac_get_algo_len(params->mac);
block = _gnutls_cipher_get_explicit_iv_size(params->cipher);
assert(_gnutls_cipher_get_block_size(params->cipher) == block);
if (params->etm) {
/* the maximum data mtu satisfies:
* data mtu (mod block) = block-1
* or data mtu = (k+1)*(block) - 1
*
* and data mtu + block + hash size + 1 = link_mtu
* (k+2) * (block) + hash size = link_mtu
*
* We try to find k, and thus data mtu
*/
k = ((mtu-hash_size)/block) - 2;
return (k+1)*block - 1;
} else {
/* the maximum data mtu satisfies:
* data mtu + hash size (mod block) = block-1
* or data mtu = (k+1)*(block) - hash size - 1
*
* and data mtu + block + hash size + 1 = link_mtu
* (k+2) * (block) = link_mtu
*
* We try to find k, and thus data mtu
*/
k = ((mtu)/block) - 2;
return (k+1)*block - hash_size - 1;
}
}
/**
* gnutls_dtls_set_data_mtu:
* @session: is a #gnutls_session_t type.
* @mtu: The maximum unencrypted transfer unit of the session
*
* This function will set the maximum size of the *unencrypted* records
* which will be sent over a DTLS session. It is equivalent to calculating
* the DTLS packet overhead with the current encryption parameters, and
* calling gnutls_dtls_set_mtu() with that value. In particular, this means
* that you may need to call this function again after any negotiation or
* renegotiation, in order to ensure that the MTU is still sufficient to
* account for the new protocol overhead.
*
* In most cases you only need to call gnutls_dtls_set_mtu() with
* the maximum MTU of your transport layer.
*
* Returns: %GNUTLS_E_SUCCESS (0) on success, or a negative error code.
*
* Since: 3.1
**/
int gnutls_dtls_set_data_mtu(gnutls_session_t session, unsigned int mtu)
{
int overhead;
overhead = record_overhead_rt(session);
/* You can't call this until the session is actually running */
if (overhead < 0)
return GNUTLS_E_INVALID_SESSION;
/* Add the overhead inside the encrypted part */
mtu += overhead;
/* Add the *unencrypted header size */
mtu += RECORD_HEADER_SIZE(session);
gnutls_dtls_set_mtu(session, mtu);
return GNUTLS_E_SUCCESS;
}
/**
* gnutls_dtls_get_mtu:
* @session: is a #gnutls_session_t type.
*
* This function will return the MTU size as set with
* gnutls_dtls_set_mtu(). This is not the actual MTU
* of data you can transmit. Use gnutls_dtls_get_data_mtu()
* for that reason.
*
* Returns: the set maximum transfer unit.
*
* Since: 3.0
**/
unsigned int gnutls_dtls_get_mtu(gnutls_session_t session)
{
return session->internals.dtls.mtu;
}
/**
* gnutls_dtls_get_timeout:
* @session: is a #gnutls_session_t type.
*
* This function will return the milliseconds remaining
* for a retransmission of the previously sent handshake
* message. This function is useful when DTLS is used in
* non-blocking mode, to estimate when to call gnutls_handshake()
* if no packets have been received.
*
* Returns: the remaining time in milliseconds.
*
* Since: 3.0
**/
unsigned int gnutls_dtls_get_timeout(gnutls_session_t session)
{
struct timespec now;
unsigned int diff;
gnutls_gettime(&now);
diff =
timespec_sub_ms(&now,
&session->internals.dtls.last_retransmit);
if (diff >= TIMER_WINDOW)
return 0;
else
return TIMER_WINDOW - diff;
}
#define COOKIE_SIZE 16
#define COOKIE_MAC_SIZE 16
/* MAC
* 16 bytes
*
* total 19 bytes
*/
#define C_HASH GNUTLS_MAC_SHA1
#define C_HASH_SIZE 20
/**
* gnutls_dtls_cookie_send:
* @key: is a random key to be used at cookie generation
* @client_data: contains data identifying the client (i.e. address)
* @client_data_size: The size of client's data
* @prestate: The previous cookie returned by gnutls_dtls_cookie_verify()
* @ptr: A transport pointer to be used by @push_func
* @push_func: A function that will be used to reply
*
* This function can be used to prevent denial of service
* attacks to a DTLS server by requiring the client to
* reply using a cookie sent by this function. That way
* it can be ensured that a client we allocated resources
* for (i.e. #gnutls_session_t) is the one that the
* original incoming packet was originated from.
*
* This function must be called at the first incoming packet,
* prior to allocating any resources and must be succeeded
* by gnutls_dtls_cookie_verify().
*
* Returns: the number of bytes sent, or a negative error code.
*
* Since: 3.0
**/
int gnutls_dtls_cookie_send(gnutls_datum_t * key, void *client_data,
size_t client_data_size,
gnutls_dtls_prestate_st * prestate,
gnutls_transport_ptr_t ptr,
gnutls_push_func push_func)
{
uint8_t hvr[20 + DTLS_HANDSHAKE_HEADER_SIZE + COOKIE_SIZE];
int hvr_size = 0, ret;
uint8_t digest[C_HASH_SIZE];
if (key == NULL || key->data == NULL || key->size == 0)
return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
/* send
* struct {
* ContentType type - 1 byte GNUTLS_HANDSHAKE;
* ProtocolVersion version; - 2 bytes (254,255)
* uint16 epoch; - 2 bytes (0, 0)
* uint48 sequence_number; - 4 bytes (0,0,0,0)
* uint16 length; - 2 bytes (COOKIE_SIZE+1+2)+DTLS_HANDSHAKE_HEADER_SIZE
* uint8_t fragment[DTLSPlaintext.length];
* } DTLSPlaintext;
*
*
* struct {
* HandshakeType msg_type; 1 byte - GNUTLS_HANDSHAKE_HELLO_VERIFY_REQUEST
* uint24 length; - COOKIE_SIZE+3
* uint16 message_seq; - 2 bytes (0,0)
* uint24 fragment_offset; - 3 bytes (0,0,0)
* uint24 fragment_length; - same as length
* }
*
* struct {
* ProtocolVersion server_version;
* uint8_t cookie<0..32>;
* } HelloVerifyRequest;
*/
hvr[hvr_size++] = GNUTLS_HANDSHAKE;
/* version */
hvr[hvr_size++] = 254;
hvr[hvr_size++] = 255;
/* epoch + seq */
memset(&hvr[hvr_size], 0, 8);
hvr_size += 7;
hvr[hvr_size++] = prestate->record_seq;
/* length */
_gnutls_write_uint16(DTLS_HANDSHAKE_HEADER_SIZE + COOKIE_SIZE + 3,
&hvr[hvr_size]);
hvr_size += 2;
/* now handshake headers */
hvr[hvr_size++] = GNUTLS_HANDSHAKE_HELLO_VERIFY_REQUEST;
_gnutls_write_uint24(COOKIE_SIZE + 3, &hvr[hvr_size]);
hvr_size += 3;
/* handshake seq */
hvr[hvr_size++] = 0;
hvr[hvr_size++] = prestate->hsk_write_seq;
_gnutls_write_uint24(0, &hvr[hvr_size]);
hvr_size += 3;
_gnutls_write_uint24(COOKIE_SIZE + 3, &hvr[hvr_size]);
hvr_size += 3;
/* version */
hvr[hvr_size++] = 254;
hvr[hvr_size++] = 255;
hvr[hvr_size++] = COOKIE_SIZE;
ret =
_gnutls_mac_fast(C_HASH, key->data, key->size, client_data,
client_data_size, digest);
if (ret < 0)
return gnutls_assert_val(ret);
memcpy(&hvr[hvr_size], digest, COOKIE_MAC_SIZE);
hvr_size += COOKIE_MAC_SIZE;
ret = push_func(ptr, hvr, hvr_size);
if (ret < 0)
ret = GNUTLS_E_PUSH_ERROR;
return ret;
}
/**
* gnutls_dtls_cookie_verify:
* @key: is a random key to be used at cookie generation
* @client_data: contains data identifying the client (i.e. address)
* @client_data_size: The size of client's data
* @_msg: An incoming message that initiates a connection.
* @msg_size: The size of the message.
* @prestate: The cookie of this client.
*
* This function will verify the received message for
* a valid cookie. If a valid cookie is returned then
* it should be associated with the session using
* gnutls_dtls_prestate_set();
*
* This function must be called after gnutls_dtls_cookie_send().
*
* Returns: %GNUTLS_E_SUCCESS (0) on success, or a negative error code.
*
* Since: 3.0
**/
int gnutls_dtls_cookie_verify(gnutls_datum_t * key,
void *client_data, size_t client_data_size,
void *_msg, size_t msg_size,
gnutls_dtls_prestate_st * prestate)
{
gnutls_datum_t cookie;
int ret;
unsigned int pos, sid_size;
uint8_t *msg = _msg;
uint8_t digest[C_HASH_SIZE];
if (key == NULL || key->data == NULL || key->size == 0)
return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);
/* format:
* version - 2 bytes
* random - 32 bytes
* session_id - 1 byte length + content
* cookie - 1 byte length + content
*/
pos = 34 + DTLS_RECORD_HEADER_SIZE + DTLS_HANDSHAKE_HEADER_SIZE;
if (msg_size < pos + 1)
return
gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
sid_size = msg[pos++];
if (sid_size > 32 || msg_size < pos + sid_size + 1)
return
gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
pos += sid_size;
cookie.size = msg[pos++];
if (msg_size < pos + cookie.size + 1)
return
gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);
cookie.data = &msg[pos];
if (cookie.size != COOKIE_SIZE) {
if (cookie.size > 0)
_gnutls_audit_log(NULL,
"Received cookie with illegal size %d. Expected %d\n",
(int) cookie.size, COOKIE_SIZE);
return gnutls_assert_val(GNUTLS_E_BAD_COOKIE);
}
ret =
_gnutls_mac_fast(C_HASH, key->data, key->size, client_data,
client_data_size, digest);
if (ret < 0)
return gnutls_assert_val(ret);
if (memcmp(digest, cookie.data, COOKIE_MAC_SIZE) != 0)
return gnutls_assert_val(GNUTLS_E_BAD_COOKIE);
prestate->record_seq = msg[10]; /* client's record seq */
prestate->hsk_read_seq = msg[DTLS_RECORD_HEADER_SIZE + 5]; /* client's hsk seq */
prestate->hsk_write_seq = 0; /* we always send zero for this msg */
return 0;
}
/**
* gnutls_dtls_prestate_set:
* @session: a new session
* @prestate: contains the client's prestate
*
* This function will associate the prestate acquired by
* the cookie authentication with the client, with the newly
* established session.
*
* This functions must be called after a successful gnutls_dtls_cookie_verify()
* and should be succeeded by the actual DTLS handshake using gnutls_handshake().
*
* Since: 3.0
**/
void gnutls_dtls_prestate_set(gnutls_session_t session,
gnutls_dtls_prestate_st * prestate)
{
record_parameters_st *params;
int ret;
if (prestate == NULL)
return;
/* we do not care about read_params, since we accept anything
* the peer sends.
*/
ret = _gnutls_epoch_get(session, EPOCH_WRITE_CURRENT, ¶ms);
if (ret < 0)
return;
params->write.sequence_number = prestate->record_seq;
session->internals.dtls.hsk_read_seq = prestate->hsk_read_seq;
session->internals.dtls.hsk_write_seq =
prestate->hsk_write_seq + 1;
}
/**
* gnutls_record_get_discarded:
* @session: is a #gnutls_session_t type.
*
* Returns the number of discarded packets in a
* DTLS connection.
*
* Returns: The number of discarded packets.
*
* Since: 3.0
**/
unsigned int gnutls_record_get_discarded(gnutls_session_t session)
{
return session->internals.dtls.packets_dropped;
}