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dtls.c
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dtls.c
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/* dtls -- a very basic DTLS implementation
*
* Copyright (C) 2011--2012 Olaf Bergmann <[email protected]>
* Copyright (C) 2013 Hauke Mehrtens <[email protected]>
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy,
* modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#ifdef HAVE_ASSERT_H
#include <assert.h>
#endif
#ifdef HAVE_TIME_H
#include <time.h>
#define clock_time() (time(NULL))
#ifndef CLOCK_SECOND
# define CLOCK_SECOND 1024
#endif
#endif
#ifndef WITH_CONTIKI
#include <stdlib.h>
#include "uthash.h"
#else /* WITH_CONTIKI */
# ifndef NDEBUG
# define DEBUG DEBUG_PRINT
# include "net/uip-debug.h"
# endif /* NDEBUG */
#endif /* WITH_CONTIKI */
#include "debug.h"
#include "numeric.h"
#include "netq.h"
#include "dtls.h"
#ifdef WITH_SHA256
# include "sha2/sha2.h"
#endif
#define dtls_set_version(H,V) dtls_int_to_uint16(&(H)->version, (V))
#define dtls_set_content_type(H,V) ((H)->content_type = (V) & 0xff)
#define dtls_set_length(H,V) ((H)->length = (V))
#define dtls_get_content_type(H) ((H)->content_type & 0xff)
#define dtls_get_version(H) dtls_uint16_to_int(&(H)->version)
#define dtls_get_epoch(H) dtls_uint16_to_int(&(H)->epoch)
#define dtls_get_sequence_number(H) dtls_uint48_to_ulong(&(H)->sequence_number)
#define dtls_get_fragment_length(H) dtls_uint24_to_int(&(H)->fragment_length)
#ifndef WITH_CONTIKI
#define HASH_FIND_PEER(head,sess,out) \
HASH_FIND(hh,head,sess,sizeof(session_t),out)
#define HASH_ADD_PEER(head,sess,add) \
HASH_ADD(hh,head,sess,sizeof(session_t),add)
#define HASH_DEL_PEER(head,delptr) \
HASH_DELETE(hh,head,delptr)
#endif /* WITH_CONTIKI */
#define DTLS_RH_LENGTH sizeof(dtls_record_header_t)
#define DTLS_HS_LENGTH sizeof(dtls_handshake_header_t)
#define DTLS_CH_LENGTH sizeof(dtls_client_hello_t) /* no variable length fields! */
#define DTLS_COOKIE_LENGTH_MAX 32
#define DTLS_CH_LENGTH_MAX sizeof(dtls_client_hello_t) + DTLS_COOKIE_LENGTH_MAX + 12 + 20
#define DTLS_HV_LENGTH sizeof(dtls_hello_verify_t)
#define DTLS_SH_LENGTH (2 + DTLS_RANDOM_LENGTH + 1 + 2 + 1)
#define DTLS_CE_LENGTH (3 + 3 + 27 + DTLS_EC_KEY_SIZE + DTLS_EC_KEY_SIZE)
#define DTLS_SKEXEC_LENGTH (1 + 2 + 1 + 1 + DTLS_EC_KEY_SIZE + DTLS_EC_KEY_SIZE + 2 + 70)
#define DTLS_CKXPSK_LENGTH_MIN 2
#define DTLS_CKXEC_LENGTH (1 + 1 + DTLS_EC_KEY_SIZE + DTLS_EC_KEY_SIZE)
#define DTLS_CV_LENGTH (1 + 1 + 2 + 1 + 1 + 1 + 1 + DTLS_EC_KEY_SIZE + 1 + 1 + DTLS_EC_KEY_SIZE)
#define DTLS_FIN_LENGTH 12
#define HS_HDR_LENGTH DTLS_RH_LENGTH + DTLS_HS_LENGTH
#define HV_HDR_LENGTH HS_HDR_LENGTH + DTLS_HV_LENGTH
#define HIGH(V) (((V) >> 8) & 0xff)
#define LOW(V) ((V) & 0xff)
#define DTLS_RECORD_HEADER(M) ((dtls_record_header_t *)(M))
#define DTLS_HANDSHAKE_HEADER(M) ((dtls_handshake_header_t *)(M))
#define HANDSHAKE(M) ((dtls_handshake_header_t *)((M) + DTLS_RH_LENGTH))
#define CLIENTHELLO(M) ((dtls_client_hello_t *)((M) + HS_HDR_LENGTH))
/* The length check here should work because dtls_*_to_int() works on
* unsigned char. Otherwise, broken messages could cause severe
* trouble. Note that this macro jumps out of the current program flow
* when the message is too short. Beware!
*/
#define SKIP_VAR_FIELD(P,L,T) { \
if (L < dtls_ ## T ## _to_int(P) + sizeof(T)) \
goto error; \
L -= dtls_ ## T ## _to_int(P) + sizeof(T); \
P += dtls_ ## T ## _to_int(P) + sizeof(T); \
}
/* some constants for the PRF */
#define PRF_LABEL(Label) prf_label_##Label
#define PRF_LABEL_SIZE(Label) (sizeof(PRF_LABEL(Label)) - 1)
static const unsigned char prf_label_master[] = "master secret";
static const unsigned char prf_label_key[] = "key expansion";
static const unsigned char prf_label_client[] = "client";
static const unsigned char prf_label_server[] = "server";
static const unsigned char prf_label_finished[] = " finished";
/* first part of Raw public key, the is the start of the Subject Public Key */
static const unsigned char cert_asn1_header[] = {
0x30, 0x59, /* SEQUENCE, length 89 bytes */
0x30, 0x13, /* SEQUENCE, length 19 bytes */
0x06, 0x07, /* OBJECT IDENTIFIER ecPublicKey (1 2 840 10045 2 1) */
0x2A, 0x86, 0x48, 0xCE, 0x3D, 0x02, 0x01,
0x06, 0x08, /* OBJECT IDENTIFIER prime256v1 (1 2 840 10045 3 1 7) */
0x2A, 0x86, 0x48, 0xCE, 0x3D, 0x03, 0x01, 0x07,
0x03, 0x42, 0x00, /* BIT STRING, length 66 bytes, 0 bits unused */
0x04 /* uncompressed, followed by the r und s values of the public key */
};
static dtls_context_t the_dtls_context;
#ifndef WITH_CONTIKI
static inline dtls_peer_t *
dtls_malloc_peer() {
return (dtls_peer_t *)malloc(sizeof(dtls_peer_t));
}
static inline void
dtls_free_peer(dtls_peer_t *peer) {
free(peer);
}
#else /* WITH_CONTIKI */
PROCESS(dtls_retransmit_process, "DTLS retransmit process");
#include "memb.h"
MEMB(peer_storage, dtls_peer_t, DTLS_PEER_MAX);
static inline dtls_peer_t *
dtls_malloc_peer() {
return memb_alloc(&peer_storage);
}
static inline void
dtls_free_peer(dtls_peer_t *peer) {
memb_free(&peer_storage, peer);
}
#endif /* WITH_CONTIKI */
void
dtls_init() {
netq_init();
crypto_init();
#ifdef WITH_CONTIKI
memb_init(&peer_storage);
#endif /* WITH_CONTIKI */
}
/* Calls cb_alert() with given arguments if defined, otherwise an
* error message is logged and the result is -1. This is just an
* internal helper.
*/
#define CALL(Context, which, ...) \
((Context)->h && (Context)->h->which \
? (Context)->h->which((Context), ##__VA_ARGS__) \
: -1)
/**
* Sends the fragment of length \p buflen given in \p buf to the
* specified \p peer. The data will be MAC-protected and encrypted
* according to the selected cipher and split into one or more DTLS
* records of the specified \p type. This function returns the number
* of bytes that were sent, or \c -1 if an error occurred.
*
* \param ctx The DTLS context to use.
* \param peer The remote peer.
* \param type The content type of the record.
* \param buf The data to send.
* \param buflen The actual length of \p buf.
* \return Less than zero on error, the number of bytes written otherwise.
*/
static int dtls_send(dtls_context_t *ctx, dtls_peer_t *peer, unsigned char type,
uint8 *buf, size_t buflen);
/**
* Stops ongoing retransmissions of handshake messages for @p peer.
*/
static void dtls_stop_retransmission(dtls_context_t *context, dtls_peer_t *peer);
static dtls_peer_t *
dtls_get_peer(struct dtls_context_t *ctx, const session_t *session) {
dtls_peer_t *p = NULL;
#ifndef WITH_CONTIKI
HASH_FIND_PEER(ctx->peers, session, p);
#else /* WITH_CONTIKI */
for (p = list_head(ctx->peers); p; p = list_item_next(p))
if (dtls_session_equals(&p->session, session))
return p;
#endif /* WITH_CONTIKI */
return p;
}
int
dtls_write(struct dtls_context_t *ctx,
session_t *dst, uint8 *buf, size_t len) {
dtls_peer_t *peer = dtls_get_peer(ctx, dst);
/* Check if peer connection already exists */
if (!peer) { /* no ==> create one */
int res;
/* dtls_connect() returns a value greater than zero if a new
* connection attempt is made, 0 for session reuse. */
res = dtls_connect(ctx, dst);
return (res >= 0) ? 0 : res;
} else { /* a session exists, check if it is in state connected */
if (peer->state != DTLS_STATE_CONNECTED) {
return 0;
} else {
return dtls_send(ctx, peer, DTLS_CT_APPLICATION_DATA, buf, len);
}
}
}
static int
dtls_get_cookie(uint8 *msg, int msglen, uint8 **cookie) {
/* To access the cookie, we have to determine the session id's
* length and skip the whole thing. */
if (msglen < DTLS_HS_LENGTH + DTLS_CH_LENGTH + sizeof(uint8))
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
if (dtls_uint16_to_int(msg + DTLS_HS_LENGTH) != DTLS_VERSION)
return dtls_alert_fatal_create(DTLS_ALERT_PROTOCOL_VERSION);
msglen -= DTLS_HS_LENGTH + DTLS_CH_LENGTH;
msg += DTLS_HS_LENGTH + DTLS_CH_LENGTH;
SKIP_VAR_FIELD(msg, msglen, uint8); /* skip session id */
if (msglen < (*msg & 0xff) + sizeof(uint8))
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
*cookie = msg + sizeof(uint8);
return dtls_uint8_to_int(msg);
error:
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
static int
dtls_create_cookie(dtls_context_t *ctx,
session_t *session,
uint8 *msg, int msglen,
uint8 *cookie, int *clen) {
unsigned char buf[DTLS_HMAC_MAX];
size_t len, e;
/* create cookie with HMAC-SHA256 over:
* - SECRET
* - session parameters (only IP address?)
* - client version
* - random gmt and bytes
* - session id
* - cipher_suites
* - compression method
*/
/* We use our own buffer as hmac_context instead of a dynamic buffer
* created by dtls_hmac_new() to separate storage space for cookie
* creation from storage that is used in real sessions. Note that
* the buffer size must fit with the default hash algorithm (see
* implementation of dtls_hmac_context_new()). */
dtls_hmac_context_t hmac_context;
dtls_hmac_init(&hmac_context, ctx->cookie_secret, DTLS_COOKIE_SECRET_LENGTH);
dtls_hmac_update(&hmac_context,
(unsigned char *)&session->addr, session->size);
/* feed in the beginning of the Client Hello up to and including the
session id */
e = sizeof(dtls_client_hello_t);
e += (*(msg + DTLS_HS_LENGTH + e) & 0xff) + sizeof(uint8);
if (e + DTLS_HS_LENGTH > msglen)
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
dtls_hmac_update(&hmac_context, msg + DTLS_HS_LENGTH, e);
/* skip cookie bytes and length byte */
e += *(uint8 *)(msg + DTLS_HS_LENGTH + e) & 0xff;
e += sizeof(uint8);
if (e + DTLS_HS_LENGTH > msglen)
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
dtls_hmac_update(&hmac_context,
msg + DTLS_HS_LENGTH + e,
dtls_get_fragment_length(DTLS_HANDSHAKE_HEADER(msg)) - e);
len = dtls_hmac_finalize(&hmac_context, buf);
if (len < *clen) {
memset(cookie + len, 0, *clen - len);
*clen = len;
}
memcpy(cookie, buf, *clen);
return 0;
}
#ifdef DTLS_CHECK_CONTENTTYPE
/* used to check if a received datagram contains a DTLS message */
static char const content_types[] = {
DTLS_CT_CHANGE_CIPHER_SPEC,
DTLS_CT_ALERT,
DTLS_CT_HANDSHAKE,
DTLS_CT_APPLICATION_DATA,
0 /* end marker */
};
#endif
/**
* Checks if \p msg points to a valid DTLS record. If
*
*/
static unsigned int
is_record(uint8 *msg, int msglen) {
unsigned int rlen = 0;
if (msglen >= DTLS_RH_LENGTH /* FIXME allow empty records? */
#ifdef DTLS_CHECK_CONTENTTYPE
&& strchr(content_types, msg[0])
#endif
&& msg[1] == HIGH(DTLS_VERSION)
&& msg[2] == LOW(DTLS_VERSION))
{
rlen = DTLS_RH_LENGTH +
dtls_uint16_to_int(DTLS_RECORD_HEADER(msg)->length);
/* we do not accept wrong length field in record header */
if (rlen > msglen)
rlen = 0;
}
return rlen;
}
/**
* Initializes \p buf as record header. The caller must ensure that \p
* buf is capable of holding at least \c sizeof(dtls_record_header_t)
* bytes. Increments sequence number counter of \p peer.
* \return pointer to the next byte after the written header
*/
static inline uint8 *
dtls_set_record_header(uint8 type, dtls_peer_t *peer, uint8 *buf) {
dtls_int_to_uint8(buf, type);
buf += sizeof(uint8);
dtls_int_to_uint16(buf, DTLS_VERSION);
buf += sizeof(uint16);
if (peer) {
memcpy(buf, &peer->epoch, sizeof(uint16) + sizeof(uint48));
/* increment record sequence counter by 1 */
inc_uint(uint48, peer->rseq);
} else {
memset(buf, 0, sizeof(uint16) + sizeof(uint48));
}
buf += sizeof(uint16) + sizeof(uint48);
memset(buf, 0, sizeof(uint16));
return buf + sizeof(uint16);
}
/**
* Initializes \p buf as handshake header. The caller must ensure that \p
* buf is capable of holding at least \c sizeof(dtls_handshake_header_t)
* bytes. Increments message sequence number counter of \p peer.
* \return pointer to the next byte after \p buf
*/
static inline uint8 *
dtls_set_handshake_header(uint8 type, dtls_peer_t *peer,
int length,
int frag_offset, int frag_length,
uint8 *buf) {
dtls_int_to_uint8(buf, type);
buf += sizeof(uint8);
dtls_int_to_uint24(buf, length);
buf += sizeof(uint24);
if (peer) {
/* increment handshake message sequence counter by 1 */
inc_uint(uint16, peer->hs_state.mseq);
/* and copy the result to buf */
memcpy(buf, &peer->hs_state.mseq, sizeof(uint16));
} else {
memset(buf, 0, sizeof(uint16));
}
buf += sizeof(uint16);
dtls_int_to_uint24(buf, frag_offset);
buf += sizeof(uint24);
dtls_int_to_uint24(buf, frag_length);
buf += sizeof(uint24);
return buf;
}
/** only one compression method is currently defined */
static uint8 compression_methods[] = {
TLS_COMPRESSION_NULL
};
static inline int is_psk_supported(dtls_context_t *ctx){
return ctx && ctx->h && ctx->h->get_psk_key;
}
static inline int is_ecdsa_supported(dtls_context_t *ctx, int is_client){
return ctx && ctx->h && ((!is_client && ctx->h->get_ecdsa_key) ||
(is_client && ctx->h->verify_ecdsa_key));
}
/**
* Returns @c 1 if @p code is a cipher suite other than @c
* TLS_NULL_WITH_NULL_NULL that we recognize.
*
* @param ctx The current DTLS context
* @param code The cipher suite identifier to check
* @param is_client 1 for a dtls client, 0 for server
* @return @c 1 iff @p code is recognized,
*/
static int
known_cipher(dtls_context_t *ctx, dtls_cipher_t code, int is_client) {
int psk;
int ecdsa;
psk = is_psk_supported(ctx);
ecdsa = is_ecdsa_supported(ctx, is_client);
return (psk && code == TLS_PSK_WITH_AES_128_CCM_8) ||
(ecdsa && code == TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8);
}
static void dtls_debug_keyblock(dtls_security_parameters_t *config)
{
dsrv_log(LOG_DEBUG, "key_block (%d bytes):\n", dtls_kb_size(config, peer->role));
dtls_dsrv_hexdump_log(LOG_DEBUG, " client_MAC_secret",
dtls_kb_client_mac_secret(config, peer->role),
dtls_kb_mac_secret_size(config, peer->role), 0);
dtls_dsrv_hexdump_log(LOG_DEBUG, " server_MAC_secret",
dtls_kb_server_mac_secret(config, peer->role),
dtls_kb_mac_secret_size(config, peer->role), 0);
dtls_dsrv_hexdump_log(LOG_DEBUG, " client_write_key",
dtls_kb_client_write_key(config, peer->role),
dtls_kb_key_size(config, peer->role), 0);
dtls_dsrv_hexdump_log(LOG_DEBUG, " server_write_key",
dtls_kb_server_write_key(config, peer->role),
dtls_kb_key_size(config, peer->role), 0);
dtls_dsrv_hexdump_log(LOG_DEBUG, " client_IV",
dtls_kb_client_iv(config, peer->role),
dtls_kb_iv_size(config, peer->role), 0);
dtls_dsrv_hexdump_log(LOG_DEBUG, " server_IV",
dtls_kb_server_iv(config, peer->role),
dtls_kb_iv_size(config, peer->role), 0);
}
static int
calculate_key_block(dtls_context_t *ctx,
dtls_handshake_parameters_t *handshake,
dtls_security_parameters_t *security,
session_t *session) {
unsigned char *pre_master_secret;
size_t pre_master_len = 0;
pre_master_secret = security->key_block;
uint8 master_secret[DTLS_MASTER_SECRET_LENGTH];
int err;
switch (handshake->cipher) {
case TLS_PSK_WITH_AES_128_CCM_8: {
const dtls_psk_key_t *psk;
err = CALL(ctx, get_psk_key, session, handshake->psk.identity, handshake->psk.id_length, &psk);
if (err < 0) {
dsrv_log(LOG_CRIT, "no psk key for session available\n");
return err;
}
/* Temporarily use the key_block storage space for the pre master secret. */
pre_master_len = dtls_psk_pre_master_secret(psk->key, psk->key_length,
pre_master_secret);
dtls_dsrv_hexdump_log(LOG_DEBUG, "psk", psk->key, psk->key_length, 1);
break;
}
case TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8: {
pre_master_len = dtls_ecdh_pre_master_secret(handshake->ecdsa.own_eph_priv,
handshake->ecdsa.other_eph_pub_x,
handshake->ecdsa.other_eph_pub_y,
sizeof(handshake->ecdsa.own_eph_priv),
pre_master_secret);
break;
}
default:
dsrv_log(LOG_CRIT, "calculate_key_block: unknown cipher\n");
return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
}
dtls_dsrv_hexdump_log(LOG_DEBUG, "client_random", handshake->tmp.random.client,
DTLS_RANDOM_LENGTH, 0);
dtls_dsrv_hexdump_log(LOG_DEBUG, "server_random", handshake->tmp.random.server,
DTLS_RANDOM_LENGTH, 0);
dtls_dsrv_hexdump_log(LOG_DEBUG, "pre_master_secret", pre_master_secret,
pre_master_len, 0);
dtls_prf(pre_master_secret, pre_master_len,
PRF_LABEL(master), PRF_LABEL_SIZE(master),
handshake->tmp.random.client, DTLS_RANDOM_LENGTH,
handshake->tmp.random.server, DTLS_RANDOM_LENGTH,
master_secret,
DTLS_MASTER_SECRET_LENGTH);
dtls_dsrv_hexdump_log(LOG_DEBUG, "master_secret", master_secret,
DTLS_MASTER_SECRET_LENGTH, 0);
/* create key_block from master_secret
* key_block = PRF(master_secret,
"key expansion" + tmp.random.server + tmp.random.client) */
dtls_prf(master_secret,
DTLS_MASTER_SECRET_LENGTH,
PRF_LABEL(key), PRF_LABEL_SIZE(key),
handshake->tmp.random.server, DTLS_RANDOM_LENGTH,
handshake->tmp.random.client, DTLS_RANDOM_LENGTH,
security->key_block,
dtls_kb_size(security, peer->role));
memcpy(handshake->tmp.master_secret, master_secret, DTLS_MASTER_SECRET_LENGTH);
dtls_debug_keyblock(security);
return 0;
}
static int
init_cipher(dtls_handshake_parameters_t *handshake, dtls_security_parameters_t *config, dtls_peer_type role)
{
/* set crypto context for TLS_PSK_WITH_AES_128_CCM_8 */
dtls_cipher_free(config->read_cipher);
assert(handshake->cipher != TLS_NULL_WITH_NULL_NULL);
config->read_cipher = dtls_cipher_new(handshake->cipher,
dtls_kb_remote_write_key(config, role),
dtls_kb_key_size(config, role));
if (!config->read_cipher) {
warn("cannot create read cipher\n");
return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
}
dtls_cipher_free(config->write_cipher);
config->write_cipher = dtls_cipher_new(handshake->cipher,
dtls_kb_local_write_key(config, role),
dtls_kb_key_size(config, role));
if (!config->write_cipher) {
dtls_cipher_free(config->read_cipher);
warn("cannot create write cipher\n");
return dtls_alert_fatal_create(DTLS_ALERT_INTERNAL_ERROR);
}
config->cipher = handshake->cipher;
config->compression = handshake->compression;
return 0;
}
/* TODO: add a generic method which iterates over a list and searches for a specific key */
static int verify_ext_eliptic_curves(uint8 *data, size_t data_length) {
int i, curve_name;
/* length of curve list */
i = dtls_uint16_to_int(data);
data += sizeof(uint16);
if (i + sizeof(uint16) != data_length) {
warn("the list of the supported elliptic curves should be tls extension length - 2\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
for (i = data_length - sizeof(uint16); i > 0; i -= sizeof(uint16)) {
/* check if this curve is supported */
curve_name = dtls_uint16_to_int(data);
data += sizeof(uint16);
if (curve_name == TLS_EXT_ELLIPTIC_CURVES_SECP256R1)
return 0;
}
warn("no supported elliptic curve found\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
static int verify_ext_cert_type(uint8 *data, size_t data_length) {
int i, cert_type;
/* length of cert type list */
i = dtls_uint8_to_int(data);
data += sizeof(uint8);
if (i + sizeof(uint8) != data_length) {
warn("the list of the supported certificate types should be tls extension length - 1\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
for (i = data_length - sizeof(uint8); i > 0; i -= sizeof(uint8)) {
/* check if this cert type is supported */
cert_type = dtls_uint8_to_int(data);
data += sizeof(uint8);
if (cert_type == TLS_CERT_TYPE_OOB)
return 0;
}
warn("no supported certificate type found\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
/**
* Updates the security parameters of given \p peer. As this must be
* done before the new configuration is activated, it changes the
* OTHER_CONFIG only. When the ClientHello handshake message in \p
* data does not contain a cipher suite or compression method, it is
* copied from the CURRENT_CONFIG.
*
* \param ctx The current DTLS context.
* \param peer The remote peer whose security parameters are about to change.
* \param data The handshake message with a ClientHello.
* \param data_length The actual size of \p data.
* \return \c 0 if an error occurred, \c 1 otherwise.
*/
static int
dtls_update_parameters(dtls_context_t *ctx,
dtls_peer_t *peer,
uint8 *data, size_t data_length) {
int i, j;
int ok;
int ext_elliptic_curve;
int ext_client_cert_type;
int ext_server_cert_type;
dtls_handshake_parameters_t *config = &peer->handshake_params;
dtls_security_parameters_t *security = &peer->security_params;
assert(config);
assert(data_length > DTLS_HS_LENGTH + DTLS_CH_LENGTH);
/* debug("dtls_update_parameters: msglen is %d\n", data_length); */
/* skip the handshake header and client version information */
data += DTLS_HS_LENGTH + sizeof(uint16);
data_length -= DTLS_HS_LENGTH + sizeof(uint16);
/* store client random in config
* FIXME: if we send the ServerHello here, we do not need to store
* the client's random bytes */
memcpy(config->tmp.random.client, data, DTLS_RANDOM_LENGTH);
data += DTLS_RANDOM_LENGTH;
data_length -= DTLS_RANDOM_LENGTH;
/* Caution: SKIP_VAR_FIELD may jump to error: */
SKIP_VAR_FIELD(data, data_length, uint8); /* skip session id */
SKIP_VAR_FIELD(data, data_length, uint8); /* skip cookie */
i = dtls_uint16_to_int(data);
if (data_length < i + sizeof(uint16)) {
/* Looks like we do not have a cipher nor compression. This is ok
* for renegotiation, but not for the initial handshake. */
if (security->cipher == TLS_NULL_WITH_NULL_NULL)
goto error;
config->cipher = security->cipher;
config->compression = security->compression;
return 0;
}
data += sizeof(uint16);
data_length -= sizeof(uint16) + i;
ok = 0;
while (i && !ok) {
config->cipher = dtls_uint16_to_int(data);
ok = known_cipher(ctx, config->cipher, 0);
i -= sizeof(uint16);
data += sizeof(uint16);
}
/* skip remaining ciphers */
data += i;
if (!ok) {
/* reset config cipher to a well-defined value */
config->cipher = TLS_NULL_WITH_NULL_NULL;
goto error;
}
if (data_length < sizeof(uint8)) {
/* no compression specified, take the current compression method */
config->compression = security->compression;
goto error;
}
i = dtls_uint8_to_int(data);
if (data_length < i + sizeof(uint8))
goto error;
data += sizeof(uint8);
data_length -= sizeof(uint8) + i;
ok = 0;
while (i && !ok) {
for (j = 0; j < sizeof(compression_methods) / sizeof(uint8); ++j)
if (dtls_uint8_to_int(data) == compression_methods[j]) {
config->compression = compression_methods[j];
ok = 1;
}
i -= sizeof(uint8);
data += sizeof(uint8);
}
if (!ok) {
/* reset config cipher to a well-defined value */
goto error;
}
if (data_length < sizeof(uint16)) {
/* no tls extensions specified */
if (config->cipher == TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8) {
goto error;
}
return 0;
}
/* get the length of the tls extension list */
j = dtls_uint16_to_int(data);
data += sizeof(uint16);
data_length -= sizeof(uint16);
if (data_length < j)
goto error;
ext_elliptic_curve = 0;
ext_client_cert_type = 0;
ext_server_cert_type = 0;
/* check for TLS extensions needed for this cipher */
while (data_length) {
if (data_length < sizeof(uint16) * 2)
goto error;
/* get the tls extension type */
i = dtls_uint16_to_int(data);
data += sizeof(uint16);
data_length -= sizeof(uint16);
/* get the length of the tls extension */
j = dtls_uint16_to_int(data);
data += sizeof(uint16);
data_length -= sizeof(uint16);
if (data_length < j)
goto error;
switch (i) {
case TLS_EXT_ELLIPTIC_CURVES:
ext_elliptic_curve = 1;
if (verify_ext_eliptic_curves(data, j))
goto error;
break;
case TLS_EXT_CLIENT_CERIFICATE_TYPE:
ext_client_cert_type = 1;
if (verify_ext_cert_type(data, j))
goto error;
break;
case TLS_EXT_SERVER_CERIFICATE_TYPE:
ext_server_cert_type = 1;
if (verify_ext_cert_type(data, j))
goto error;
break;
default:
warn("unsupported tls extension: %i\n", i);
break;
}
data += j;
data_length -= j;
}
if (config->cipher == TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8) {
if (!ext_elliptic_curve && !ext_client_cert_type && !ext_server_cert_type) {
warn("not all required tls extensions found in client hello\n");
goto error;
}
}
return 0;
error:
warn("ClientHello too short (%d bytes)\n", data_length);
if (peer->state == DTLS_STATE_CONNECTED) {
return dtls_alert_create(DTLS_ALERT_LEVEL_WARNING, DTLS_ALERT_NO_RENEGOTIATION);
} else {
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
}
static inline int
check_client_keyexchange(dtls_context_t *ctx,
dtls_handshake_parameters_t *handshake,
uint8 *data, size_t length) {
if (handshake->cipher == TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8) {
if (length < DTLS_HS_LENGTH + DTLS_CKXEC_LENGTH) {
debug("The client key exchange is too short\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
data += DTLS_HS_LENGTH;
if (dtls_uint8_to_int(data) != 65) {
dsrv_log(LOG_ALERT, "expected 65 bytes long public point\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
data += sizeof(uint8);
if (dtls_uint8_to_int(data) != 4) {
dsrv_log(LOG_ALERT, "expected uncompressed public point\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
data += sizeof(uint8);
memcpy(handshake->ecdsa.other_eph_pub_x, data,
sizeof(handshake->ecdsa.other_eph_pub_x));
data += sizeof(handshake->ecdsa.other_eph_pub_x);
memcpy(handshake->ecdsa.other_eph_pub_y, data,
sizeof(handshake->ecdsa.other_eph_pub_y));
data += sizeof(handshake->ecdsa.other_eph_pub_y);
} else {
int id_length;
if (length < DTLS_HS_LENGTH + DTLS_CKXPSK_LENGTH_MIN) {
debug("The client key exchange is too short\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
data += DTLS_HS_LENGTH;
id_length = dtls_uint16_to_int(data);
data += sizeof(uint16);
if (DTLS_HS_LENGTH + DTLS_CKXPSK_LENGTH_MIN + id_length != length) {
debug("The identity has a wrong length\n");
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}
handshake->psk.id_length = min(id_length, 32);
memcpy(handshake->psk.identity, data, min(id_length, 32));
}
return 0;
}
static dtls_peer_t *
dtls_new_peer(dtls_context_t *ctx,
const session_t *session) {
dtls_peer_t *peer;
peer = dtls_malloc_peer();
if (peer) {
memset(peer, 0, sizeof(dtls_peer_t));
memcpy(&peer->session, session, sizeof(session_t));
dtls_dsrv_log_addr(LOG_DEBUG, "dtls_new_peer", session);
/* initially allow the NULL cipher */
peer->security_params.cipher = TLS_NULL_WITH_NULL_NULL;
peer->security_params.compression = TLS_COMPRESSION_NULL;
/* initialize the handshake hash wrt. the hard-coded DTLS version */
debug("DTLSv12: initialize HASH_SHA256\n");
/* TLS 1.2: PRF(secret, label, seed) = P_<hash>(secret, label + seed) */
/* FIXME: we use the default SHA256 here, might need to support other
hash functions as well */
dtls_hash_init(&peer->hs_state.hs_hash);
}
return peer;
}
static inline void
update_hs_hash(dtls_peer_t *peer, uint8 *data, size_t length) {
dtls_dsrv_hexdump_log(LOG_DEBUG, "add MAC data", data, length, 0);
dtls_hash_update(&peer->hs_state.hs_hash, data, length);
}
static void
copy_hs_hash(dtls_peer_t *peer, dtls_hash_ctx *hs_hash) {
memcpy(hs_hash, &peer->hs_state.hs_hash, sizeof(peer->hs_state.hs_hash));
}
static inline size_t
finalize_hs_hash(dtls_peer_t *peer, uint8 *buf) {
return dtls_hash_finalize(buf, &peer->hs_state.hs_hash);
}
static inline void
clear_hs_hash(dtls_peer_t *peer) {
assert(peer);
debug("clear MAC\n");
dtls_hash_init(&peer->hs_state.hs_hash);
}
/**
*Checks if \p record + \p data contain a Finished message with valid
* verify_data.
*
* \param ctx The current DTLS context.
* \param peer The remote peer of the security association.
* \param record The message record header.
* \param rlen The actual length of \p record.
* \param data The cleartext payload of the message.
* \param data_length Actual length of \p data.
* \return \c 1 if the Finished message is valid, \c 0 otherwise.
*/
static int
check_finished(dtls_context_t *ctx, dtls_peer_t *peer,
uint8 *record, uint8 *data, size_t data_length) {
size_t digest_length, label_size;
const unsigned char *label;
unsigned char buf[DTLS_HMAC_MAX];
if (data_length < DTLS_HS_LENGTH + DTLS_FIN_LENGTH)
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
/* Use a union here to ensure that sufficient stack space is
* reserved. As statebuf and verify_data are not used at the same
* time, we can re-use the storage safely.
*/
union {
unsigned char statebuf[DTLS_HASH_CTX_SIZE];
unsigned char verify_data[DTLS_FIN_LENGTH];
} b;
/* temporarily store hash status for roll-back after finalize */
memcpy(b.statebuf, &peer->hs_state.hs_hash, DTLS_HASH_CTX_SIZE);
digest_length = finalize_hs_hash(peer, buf);
/* clear_hash(); */
/* restore hash status */
memcpy(&peer->hs_state.hs_hash, b.statebuf, DTLS_HASH_CTX_SIZE);
if (peer->role == DTLS_CLIENT) {
label = PRF_LABEL(server);
label_size = PRF_LABEL_SIZE(server);
} else { /* client */
label = PRF_LABEL(client);
label_size = PRF_LABEL_SIZE(client);
}
dtls_prf(peer->handshake_params.tmp.master_secret,
DTLS_MASTER_SECRET_LENGTH,
label, label_size,
PRF_LABEL(finished), PRF_LABEL_SIZE(finished),
buf, digest_length,
b.verify_data, sizeof(b.verify_data));