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Add client dtls connection ID.
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Simple client side implementation indicates support and uses the cid of
the server, when negotiated by that.

Signed-off-by: Achim Kraus <achim.kraus@bosch.io>
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Achim Kraus committed Dec 23, 2021
1 parent 68f6045 commit d3d242b
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Showing 4 changed files with 204 additions and 18 deletions.
20 changes: 19 additions & 1 deletion crypto.h
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Original file line number Diff line number Diff line change
Expand Up @@ -96,6 +96,11 @@ typedef struct {
uint64_t bitfield;
} seqnum_t;

/* Maximum CID length. */
#ifndef DTLS_MAX_CID_LENGTH
#define DTLS_MAX_CID_LENGTH 16
#endif

typedef struct {
dtls_compression_t compression; /**< compression method */

Expand All @@ -110,7 +115,12 @@ typedef struct {
* access the components of the key block.
*/
uint8 key_block[MAX_KEYBLOCK_LENGTH];


#if (DTLS_MAX_CID_LENGTH > 0)
uint8_t write_cid[DTLS_MAX_CID_LENGTH];
uint8_t write_cid_length;
#endif /* DTLS_MAX_CID_LENGTH > 0 */

seqnum_t cseq; /**<sequence number of last record received*/
} dtls_security_parameters_t;

Expand All @@ -130,6 +140,14 @@ typedef struct {

dtls_compression_t compression; /**< compression method */
dtls_cipher_t cipher; /**< cipher type */

#if (DTLS_MAX_CID_LENGTH > 0)
uint8_t write_cid[DTLS_MAX_CID_LENGTH];
uint8_t write_cid_length;

unsigned int use_connection_id:1;
#endif /* DTLS_MAX_CID_LENGTH > 0 */

unsigned int do_client_auth:1;
unsigned int extended_master_secret:1;
union {
Expand Down
181 changes: 164 additions & 17 deletions dtls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -112,7 +112,7 @@ memarray_t dtlscontext_storage;
#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 + 26 + 12
#define DTLS_CH_LENGTH_MAX sizeof(dtls_client_hello_t) + DTLS_COOKIE_LENGTH_MAX + 12 + 43
#define DTLS_HV_LENGTH sizeof(dtls_hello_verify_t)
#define DTLS_SH_LENGTH (2 + DTLS_RANDOM_LENGTH + 1 + 2 + 1)
#define DTLS_SKEXEC_LENGTH (1 + 2 + 1 + 1 + DTLS_EC_KEY_SIZE + DTLS_EC_KEY_SIZE + 1 + 1 + 2 + 70)
Expand Down Expand Up @@ -841,6 +841,10 @@ calculate_key_block(dtls_context_t *ctx,
security->cipher = handshake->cipher;
security->compression = handshake->compression;
security->rseq = 0;
#if (DTLS_MAX_CID_LENGTH > 0)
security->write_cid_length = handshake->write_cid_length;
memcpy(security->write_cid, handshake->write_cid, handshake->write_cid_length);
#endif /* DTLS_MAX_CID_LENGTH > 0 */

return 0;
}
Expand Down Expand Up @@ -945,6 +949,37 @@ static int verify_ext_sig_hash_algo(uint8 *data, size_t data_length) {
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}

#if (DTLS_MAX_CID_LENGTH > 0)

static int get_ext_connection_id(dtls_handshake_parameters_t *handshake, uint8 *data, size_t data_length) {
uint8_t i;

if (sizeof(uint8) > data_length) {
dtls_warn("invalid length (%ld) for extension connection id\n", data_length);
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}

/* length of the connection id */
i = dtls_uint8_to_int(data);
data += sizeof(uint8);
if (i + sizeof(uint8) != data_length) {
dtls_warn("invalid connection id length (%d)\n", i);
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}

if (DTLS_MAX_CID_LENGTH < i) {
dtls_warn("connection id length (%d) exceeds maximum (%d)!\n", i, DTLS_MAX_CID_LENGTH);
return dtls_alert_fatal_create(DTLS_ALERT_HANDSHAKE_FAILURE);
}

handshake->write_cid_length = i;
memcpy(handshake->write_cid, data, i);

return 0;
}

#endif /* DTLS_MAX_CID_LENGTH > 0*/

/*
* Check for some TLS Extensions used by the ECDHE_ECDSA cipher.
*/
Expand Down Expand Up @@ -1037,6 +1072,16 @@ dtls_check_tls_extension(dtls_peer_t *peer,
if (verify_ext_sig_hash_algo(data, j))
goto error;
break;
#if (DTLS_MAX_CID_LENGTH > 0)
case TLS_EXT_CONNECTION_ID:
if (!client_hello && !handshake->use_connection_id) {
dtls_warn("connection id was not sent by client!\n");
goto error;
}
if (get_ext_connection_id(handshake, data, j))
goto error;
break;
#endif /* DTLS_MAX_CID_LENGTH */
default:
dtls_warn("unsupported tls extension: %i\n", i);
break;
Expand Down Expand Up @@ -1383,9 +1428,10 @@ dtls_prepare_record(dtls_peer_t *peer, dtls_security_parameters_t *security,
uint8 *data_array[], size_t data_len_array[],
size_t data_array_len,
uint8 *sendbuf, size_t *rlen) {
uint8 *p, *start;
uint8 *p;
int res;
unsigned int i;
uint8_t cid_length = 0;

if (*rlen < DTLS_RH_LENGTH) {
dtls_alert("The sendbuf (%zu bytes) is too small\n", *rlen);
Expand All @@ -1398,7 +1444,6 @@ dtls_prepare_record(dtls_peer_t *peer, dtls_security_parameters_t *security,
}

p = dtls_set_record_header(type, security->epoch, &(security->rseq), sendbuf);
start = p;

if (security->cipher == TLS_NULL_WITH_NULL_NULL) {
/* no cipher suite */
Expand All @@ -1417,12 +1462,28 @@ dtls_prepare_record(dtls_peer_t *peer, dtls_security_parameters_t *security,
}
} else { /* TLS_PSK_WITH_AES_128_CCM_8 or TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 */
/**
* RFC6347
* length of additional_data for the AEAD cipher which consists of
* seq_num(2+6) + type(1) + version(2) + length(2)
*/
#define A_DATA_LEN 13

#if (DTLS_MAX_CID_LENGTH > 0)
/**
* RFC9146
* length of extra additional_data for the AEAD cipher which consists of
* seq_num_placeholder(8) + type(1) + cid_length(1)
*/
#define A_DATA_CID_EXTRA_LEN 10
#define A_DATA_MAX_LEN (A_DATA_LEN + A_DATA_CID_EXTRA_LEN + DTLS_MAX_CID_LENGTH)
#else
#define A_DATA_MAX_LEN A_DATA_LEN
#endif

uint8 *start = p;
unsigned char nonce[DTLS_CCM_BLOCKSIZE];
unsigned char A_DATA[A_DATA_LEN];
unsigned char A_DATA[A_DATA_MAX_LEN];
uint8_t a_data_len = A_DATA_LEN;
/* For backwards-compatibility, dtls_encrypt_params is called with
* M=<macLen> and L=3. */
const dtls_ccm_params_t params = { nonce, 8, 3 };
Expand All @@ -1435,6 +1496,16 @@ dtls_prepare_record(dtls_peer_t *peer, dtls_security_parameters_t *security,
dtls_debug("dtls_prepare_record(): encrypt using unknown cipher\n");
}

#if (DTLS_MAX_CID_LENGTH > 0)
cid_length = security->write_cid_length;
if (cid_length > 0) {
/* add cid to record header */
memcpy(p - sizeof(uint16_t), security->write_cid, cid_length);
p += cid_length;
start = p;
}
#endif /* DTLS_MAX_CID_LENGTH > 0 */

/* set nonce
from RFC 6655:
The "nonce" input to the AEAD algorithm is exactly that of [RFC5288]:
Expand Down Expand Up @@ -1500,31 +1571,62 @@ dtls_prepare_record(dtls_peer_t *peer, dtls_security_parameters_t *security,
dtls_debug_dump("key:", dtls_kb_local_write_key(security, peer->role),
dtls_kb_key_size(security, peer->role));

/* re-use N to create additional data according to RFC 5246, Section 6.2.3.3:
*
* additional_data = seq_num + TLSCompressed.type +
* TLSCompressed.version + TLSCompressed.length;
*/
memcpy(A_DATA, &DTLS_RECORD_HEADER(sendbuf)->epoch, 8); /* epoch and seq_num */
memcpy(A_DATA + 8, &DTLS_RECORD_HEADER(sendbuf)->content_type, 3); /* type and version */
dtls_int_to_uint16(A_DATA + 11, res - 8); /* length */
#if (DTLS_MAX_CID_LENGTH > 0)
if (cid_length > 0) {
/* RFC 9146 */

/* inner content type */
*p = *sendbuf;
*sendbuf = DTLS_CT_TLS12_CID;
p += sizeof(uint8_t);
res += sizeof(uint8_t);

/* seq_num_placeholder: 8x 0xff */
memset(A_DATA, 0xff, 8);
/* tls_cid: 25 */
A_DATA[8] = DTLS_CT_TLS12_CID;
/* cid length */
A_DATA[9] = cid_length;
/* copy record header */
memcpy(A_DATA + A_DATA_CID_EXTRA_LEN, sendbuf, A_DATA_LEN + cid_length);
dtls_int_to_uint16(A_DATA + A_DATA_CID_EXTRA_LEN + 11 + cid_length, res - 8); /* length */
a_data_len = A_DATA_LEN + A_DATA_CID_EXTRA_LEN + cid_length;

} else {
#endif /* DTLS_MAX_CID_LENGTH > 0 */
/* RFC 6347 */
/* re-use N to create additional data according to RFC 5246, Section 6.2.3.3:
*
* additional_data = seq_num + TLSCompressed.type +
* TLSCompressed.version + TLSCompressed.length;
*/
memcpy(A_DATA, &DTLS_RECORD_HEADER(sendbuf)->epoch, 8); /* epoch and seq_num */
memcpy(A_DATA + 8, &DTLS_RECORD_HEADER(sendbuf)->content_type, 3); /* type and version */
dtls_int_to_uint16(A_DATA + 11, res - 8); /* length */
a_data_len = A_DATA_LEN;
#if (DTLS_MAX_CID_LENGTH > 0)
}
#endif /* DTLS_MAX_CID_LENGTH > 0 */

dtls_debug_dump("adata:", A_DATA, a_data_len);
dtls_debug_dump("message:", start, res);

res = dtls_encrypt_params(&params, start + 8, res - 8, start + 8,
dtls_kb_local_write_key(security, peer->role),
dtls_kb_key_size(security, peer->role),
A_DATA, A_DATA_LEN);
A_DATA, a_data_len);

if (res < 0)
return res;

res += 8; /* increment res by size of nonce_explicit */
dtls_debug_dump("message:", start, res);
dtls_debug_dump("encrypted-message:", start, res);
}

/* fix length of fragment in sendbuf */
dtls_int_to_uint16(sendbuf + 11, res);
dtls_int_to_uint16(sendbuf + 11 + cid_length, res);

*rlen = DTLS_RH_LENGTH + res;
*rlen = DTLS_RH_LENGTH + res + cid_length;
return 0;
}

Expand Down Expand Up @@ -2728,7 +2830,35 @@ dtls_send_client_hello(dtls_context_t *ctx, dtls_peer_t *peer,
ecdsa = is_ecdsa_supported(ctx, 1);

cipher_size = 2 + ((ecdsa) ? 2 : 0) + ((psk) ? 2 : 0);
extension_size = 4 + ((ecdsa) ? 6 + 6 + 8 + 6 + 8: 0);
/*
* session_length := 1 byte
* session := 0 bytes
* cookie_length := 1 byte
* cookie := n bytes
* cipher suites (max) := 6 bytes
* compression := 2 bytes
* extensions_length := 2 bytes => 12
*
* client_cert_type := 6 bytes
* server_cert_type := 6 bytes
* ec curves := 8 bytes
* ec point format := 6 bytes => 26
* sign. and hash algos := 8 bytes
* extended master secret := 4 bytes => 12
* connection id, empty := 5 bytes
* => 26 + 12 + 5 := 43
*/
extension_size = ((ecdsa) ? 6 + 6 + 8 + 6 + 8 : 0) + 4;

#if (DTLS_MAX_CID_LENGTH > 0)
handshake->use_connection_id = DTLS_USE_CID_DEFAULT;
if (ctx && ctx->h && ctx->h->use_cid) {
handshake->use_connection_id = ctx->h->use_cid(ctx, &peer->session);
}
if (handshake->use_connection_id) {
extension_size += 5;
}
#endif /* DTLS_MAX_CID_LENGTH > 0 */

if (cipher_size == 0) {
dtls_crit("no cipher callbacks implemented\n");
Expand Down Expand Up @@ -2879,8 +3009,25 @@ dtls_send_client_hello(dtls_context_t *ctx, dtls_peer_t *peer,
/* length of this extension type */
dtls_int_to_uint16(p, 0);
p += sizeof(uint16);

handshake->extended_master_secret = 1;

#if (DTLS_MAX_CID_LENGTH > 0)
if (handshake->use_connection_id) {
/* connection id, empty to indicate support */
dtls_int_to_uint16(p, TLS_EXT_CONNECTION_ID);
p += sizeof(uint16);

/* length of this extension type */
dtls_int_to_uint16(p, sizeof(uint8));
p += sizeof(uint16);

/* empty cid, indicating support for cid extension */
dtls_int_to_uint8(p, 0);
p += sizeof(uint8);
}
#endif /* DTLS_MAX_CID_LENGTH > 0 */

handshake->hs_state.read_epoch = dtls_security_params(peer)->epoch;
assert((buf <= p) && ((unsigned int)(p - buf) <= sizeof(buf)));

Expand Down
19 changes: 19 additions & 0 deletions dtls.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,12 @@
#define DTLS_VERSION 0xfefd /* DTLS v1.2 */
#endif

#if (DTLS_MAX_CID_LENGTH > 0)
#ifndef DTLS_USE_CID_DEFAULT
#define DTLS_USE_CID_DEFAULT 1
#endif /* DTLS_USE_CID_DEFAULT */
#endif /* DTLS_MAX_CID_LENGTH > 0 */

typedef enum dtls_credentials_type_t {
DTLS_PSK_HINT, DTLS_PSK_IDENTITY, DTLS_PSK_KEY
} dtls_credentials_type_t;
Expand Down Expand Up @@ -119,6 +125,18 @@ typedef struct {
int (*event)(struct dtls_context_t *ctx, session_t *session,
dtls_alert_level_t level, unsigned short code);

#if (DTLS_MAX_CID_LENGTH > 0)
/**
* Called during handshake to check, if cid is to be used.
* If callback is NULL, DTLS_USE_CID_DEFAULT is used instead
*
* @param ctx The current dtls context.
* @param session The session where cid will be used.
* @return 0, cid not used, 1 cid used.
*/
int (*use_cid)(struct dtls_context_t *ctx, session_t *session);
#endif /* DTLS_MAX_CID_LENGTH > 0 */

#ifdef DTLS_PSK
/**
* Called during handshake to get information related to the
Expand Down Expand Up @@ -323,6 +341,7 @@ void dtls_check_retransmit(dtls_context_t *context, clock_time_t *next);
#define DTLS_CT_ALERT 21
#define DTLS_CT_HANDSHAKE 22
#define DTLS_CT_APPLICATION_DATA 23
#define DTLS_CT_TLS12_CID 25

/** Generic header structure of the DTLS record layer. */
typedef struct __attribute__((__packed__)) {
Expand Down
2 changes: 2 additions & 0 deletions global.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -81,6 +81,8 @@ typedef enum {
#define TLS_EXT_SERVER_CERTIFICATE_TYPE 20 /* see RFC 7250 */
#define TLS_EXT_ENCRYPT_THEN_MAC 22 /* see RFC 7366 */
#define TLS_EXT_EXTENDED_MASTER_SECRET 23 /* see RFC 7627 */
#define TLS_EXT_CONNECTION_ID 54 /* see RFC 9146 */


#define TLS_CERT_TYPE_RAW_PUBLIC_KEY 2 /* see RFC 7250 */

Expand Down

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