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Add support for FFDH in TLS 1.3

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Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
This commit is contained in:
Przemek Stekiel 2023-05-18 15:45:53 +02:00
parent cceb933e30
commit c89f3ea9f2
4 changed files with 155 additions and 39 deletions
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94
library/ssl_tls13_client.c
View file

@ -33,6 +33,7 @@
#include "ssl_client.h"
#include "ssl_tls13_keys.h"
#include "ssl_debug_helpers.h"
#include "mbedtls/dhm.h"
#define PSA_TO_MBEDTLS_ERR(status) PSA_TO_MBEDTLS_ERR_LIST(status, \
psa_to_ssl_errors, \
@ -185,8 +186,9 @@ static int ssl_tls13_reset_key_share(mbedtls_ssl_context *ssl)
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
}
#if defined(PSA_WANT_ALG_ECDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group_id)) {
#if defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group_id) ||
mbedtls_ssl_tls13_named_group_is_dhe(group_id)) {
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
@ -201,7 +203,7 @@ static int ssl_tls13_reset_key_share(mbedtls_ssl_context *ssl)
ssl->handshake->ecdh_psa_privkey = MBEDTLS_SVC_KEY_ID_INIT;
return 0;
} else
#endif /* PSA_WANT_ALG_ECDH */
#endif /* PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH */
if (0 /* other KEMs? */) {
/* Do something */
}
@ -220,13 +222,20 @@ static int ssl_tls13_get_default_group_id(mbedtls_ssl_context *ssl,
int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
#if defined(PSA_WANT_ALG_ECDH)
#if defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)
const uint16_t *group_list = mbedtls_ssl_get_groups(ssl);
/* Pick first available ECDHE group compatible with TLS 1.3 */
if (group_list == NULL) {
return MBEDTLS_ERR_SSL_BAD_CONFIG;
}
#if defined(PSA_WANT_ALG_FFDH)
if (*group_list >= MBEDTLS_SSL_IANA_TLS_GROUP_FFDHE2048 &&
*group_list <= MBEDTLS_SSL_IANA_TLS_GROUP_FFDHE8192) {
*group_id = *group_list;
return 0;
}
#endif /* PSA_WANT_ALG_FFDH */
#if defined(PSA_WANT_ALG_ECDH)
for (; *group_list != 0; group_list++) {
if ((mbedtls_ssl_get_psa_curve_info_from_tls_id(
*group_list, NULL, NULL) == PSA_SUCCESS) &&
@ -235,10 +244,11 @@ static int ssl_tls13_get_default_group_id(mbedtls_ssl_context *ssl,
return 0;
}
}
#endif /* PSA_WANT_ALG_ECDH */
#else
((void) ssl);
((void) group_id);
#endif /* PSA_WANT_ALG_ECDH */
#endif /* PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH */
/*
* Add DHE named groups here.
@ -302,8 +312,9 @@ static int ssl_tls13_write_key_share_ext(mbedtls_ssl_context *ssl,
* only one key share entry is allowed.
*/
client_shares = p;
#if defined(PSA_WANT_ALG_ECDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group_id)) {
#if defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group_id) ||
mbedtls_ssl_tls13_named_group_is_dhe(group_id)) {
/* Pointer to group */
unsigned char *group = p;
/* Length of key_exchange */
@ -315,8 +326,18 @@ static int ssl_tls13_write_key_share_ext(mbedtls_ssl_context *ssl,
*/
MBEDTLS_SSL_CHK_BUF_PTR(p, end, 4);
p += 4;
ret = mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
ssl, group_id, p, end, &key_exchange_len);
#if defined(PSA_WANT_ALG_ECDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group_id)) {
ret = mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
ssl, group_id, p, end, &key_exchange_len);
}
#endif /* PSA_WANT_ALG_ECDH */
#if defined(PSA_WANT_ALG_FFDH)
if (mbedtls_ssl_tls13_named_group_is_dhe(group_id)) {
ret = mbedtls_ssl_tls13_generate_and_write_dhe_key_exchange(
ssl, group_id, p, end, &key_exchange_len);
}
#endif /* PSA_WANT_ALG_FFDH */
p += key_exchange_len;
if (ret != 0) {
return ret;
@ -327,7 +348,7 @@ static int ssl_tls13_write_key_share_ext(mbedtls_ssl_context *ssl,
/* Write key_exchange_length */
MBEDTLS_PUT_UINT16_BE(key_exchange_len, group, 2);
} else
#endif /* PSA_WANT_ALG_ECDH */
#endif /* PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH */
if (0 /* other KEMs? */) {
/* Do something */
} else {
@ -404,15 +425,18 @@ static int ssl_tls13_parse_hrr_key_share_ext(mbedtls_ssl_context *ssl,
* then the client MUST abort the handshake with an "illegal_parameter" alert.
*/
for (; *group_list != 0; group_list++) {
if ((mbedtls_ssl_get_psa_curve_info_from_tls_id(
*group_list, NULL, NULL) == PSA_ERROR_NOT_SUPPORTED) ||
*group_list != selected_group) {
continue;
if (mbedtls_ssl_tls13_named_group_is_ecdhe(*group_list)) {
if ((mbedtls_ssl_get_psa_curve_info_from_tls_id(
*group_list, NULL, NULL) == PSA_ERROR_NOT_SUPPORTED) ||
*group_list != selected_group) {
found = 1;
break;
}
}
if (mbedtls_ssl_tls13_named_group_is_dhe(*group_list)) {
found = 1;
break;
}
/* We found a match */
found = 1;
break;
}
/* Client MUST verify that the selected_group field does not
@ -482,24 +506,34 @@ static int ssl_tls13_parse_key_share_ext(mbedtls_ssl_context *ssl,
return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
}
#if defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group) ||
mbedtls_ssl_tls13_named_group_is_dhe(group)) {
#if defined(PSA_WANT_ALG_ECDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group)) {
if (mbedtls_ssl_get_psa_curve_info_from_tls_id(group, NULL, NULL)
== PSA_ERROR_NOT_SUPPORTED) {
MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid TLS curve group id"));
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group)) {
if (mbedtls_ssl_get_psa_curve_info_from_tls_id(group, NULL, NULL)
== PSA_ERROR_NOT_SUPPORTED) {
MBEDTLS_SSL_DEBUG_MSG(1, ("Invalid TLS curve group id"));
return MBEDTLS_ERR_SSL_INTERNAL_ERROR;
}
MBEDTLS_SSL_DEBUG_MSG(
2,
("ECDH curve: %s", mbedtls_ssl_get_curve_name_from_tls_id(group)));
}
MBEDTLS_SSL_DEBUG_MSG(
2,
("ECDH curve: %s", mbedtls_ssl_get_curve_name_from_tls_id(group)));
#endif /* PSA_WANT_ALG_ECDH */
#if defined(PSA_WANT_ALG_FFDH)
if (mbedtls_ssl_tls13_named_group_is_dhe(group)) {
MBEDTLS_SSL_DEBUG_MSG(2,
("DHE group name: %s", mbedtls_ssl_ffdh_name_from_group(group)));
}
#endif /* PSA_WANT_ALG_FFDH */
ret = mbedtls_ssl_tls13_read_public_ecdhe_share(ssl, p, end - p);
if (ret != 0) {
return ret;
}
} else
#endif /* PSA_WANT_ALG_ECDH */
#endif /* PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH */
if (0 /* other KEMs? */) {
/* Do something */
} else {

62
library/ssl_tls13_generic.c
View file

@ -1571,6 +1571,68 @@ int mbedtls_ssl_tls13_generate_and_write_ecdh_key_exchange(
}
#endif /* PSA_WANT_ALG_ECDH */
#if defined(PSA_WANT_ALG_FFDH)
int mbedtls_ssl_tls13_generate_and_write_dhe_key_exchange(
mbedtls_ssl_context *ssl,
uint16_t named_group,
unsigned char *buf,
unsigned char *end,
size_t *out_len)
{
psa_status_t status = PSA_ERROR_GENERIC_ERROR;
int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
psa_key_attributes_t key_attributes;
size_t own_pubkey_len;
mbedtls_ssl_handshake_params *handshake = ssl->handshake;
size_t ffdh_bits = 0;
MBEDTLS_SSL_DEBUG_MSG(1, ("Perform PSA-based DHE computation."));
/* Convert DHE group to PSA key type. */
if ((handshake->ecdh_psa_type =
mbedtls_psa_parse_tls_ffdh_group(named_group, &ffdh_bits)) == 0) {
return MBEDTLS_ERR_SSL_HANDSHAKE_FAILURE;
}
if ((size_t) (end - buf) < PSA_BITS_TO_BYTES(ffdh_bits)) {
ret = MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL;
return ret;
}
ssl->handshake->ecdh_bits = ffdh_bits;
key_attributes = psa_key_attributes_init();
psa_set_key_usage_flags(&key_attributes, PSA_KEY_USAGE_DERIVE);
psa_set_key_algorithm(&key_attributes, PSA_ALG_FFDH);
psa_set_key_type(&key_attributes, handshake->ecdh_psa_type);
psa_set_key_bits(&key_attributes, handshake->ecdh_bits);
/* Generate FFDH private key. */
status = psa_generate_key(&key_attributes,
&handshake->ecdh_psa_privkey);
if (status != PSA_SUCCESS) {
ret = psa_ssl_status_to_mbedtls(status);
MBEDTLS_SSL_DEBUG_RET(1, "psa_generate_key", ret);
return ret;
}
/* Export the public part of the FFDH private key from PSA. */
status = psa_export_public_key(handshake->ecdh_psa_privkey,
buf, PSA_BITS_TO_BYTES(ffdh_bits),
&own_pubkey_len);
if (status != PSA_SUCCESS) {
ret = psa_ssl_status_to_mbedtls(status);
MBEDTLS_SSL_DEBUG_RET(1, "psa_export_public_key", ret);
return ret;
}
*out_len = own_pubkey_len;
return 0;
}
#endif /* PSA_WANT_ALG_FFDH */
/* RFC 8446 section 4.2
*
* If an implementation receives an extension which it recognizes and which is

15
library/ssl_tls13_keys.c
View file

@ -1484,8 +1484,15 @@ static int ssl_tls13_key_schedule_stage_handshake(mbedtls_ssl_context *ssl)
* are derived in the handshake secret derivation stage.
*/
if (mbedtls_ssl_tls13_key_exchange_mode_with_ephemeral(ssl)) {
if (mbedtls_ssl_tls13_named_group_is_ecdhe(handshake->offered_group_id)) {
#if defined(PSA_WANT_ALG_ECDH)
if (mbedtls_ssl_tls13_named_group_is_ecdhe(handshake->offered_group_id) ||
mbedtls_ssl_tls13_named_group_is_dhe(handshake->offered_group_id)) {
#if defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)
psa_algorithm_t alg = 0;
if (mbedtls_ssl_tls13_named_group_is_ecdhe(handshake->offered_group_id)) {
alg = PSA_ALG_ECDH;
} else {
alg = PSA_ALG_FFDH;
}
/* Compute ECDH shared secret. */
psa_status_t status = PSA_ERROR_GENERIC_ERROR;
psa_key_attributes_t key_attributes = PSA_KEY_ATTRIBUTES_INIT;
@ -1504,7 +1511,7 @@ static int ssl_tls13_key_schedule_stage_handshake(mbedtls_ssl_context *ssl)
}
status = psa_raw_key_agreement(
PSA_ALG_ECDH, handshake->ecdh_psa_privkey,
alg, handshake->ecdh_psa_privkey,
handshake->ecdh_psa_peerkey, handshake->ecdh_psa_peerkey_len,
shared_secret, shared_secret_len, &shared_secret_len);
if (status != PSA_SUCCESS) {
@ -1521,7 +1528,7 @@ static int ssl_tls13_key_schedule_stage_handshake(mbedtls_ssl_context *ssl)
}
handshake->ecdh_psa_privkey = MBEDTLS_SVC_KEY_ID_INIT;
#endif /* PSA_WANT_ALG_ECDH */
#endif /* PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH */
} else {
MBEDTLS_SSL_DEBUG_MSG(1, ("Group not supported."));
return MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;

23
library/ssl_tls13_server.c
View file

@ -836,7 +836,7 @@ static int ssl_tls13_parse_supported_groups_ext(mbedtls_ssl_context *ssl,
#define SSL_TLS1_3_PARSE_KEY_SHARES_EXT_NO_MATCH 1
#if defined(PSA_WANT_ALG_ECDH)
#if defined(PSA_WANT_ALG_ECDH) || defined(PSA_WANT_ALG_FFDH)
/*
* ssl_tls13_parse_key_shares_ext() verifies whether the information in the
* extension is correct and stores the first acceptable key share and its
@ -910,10 +910,11 @@ static int ssl_tls13_parse_key_shares_ext(mbedtls_ssl_context *ssl,
}
/*
* For now, we only support ECDHE groups.
* ECDHE and FFDHE groups are supported
*/
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group)) {
MBEDTLS_SSL_DEBUG_MSG(2, ("ECDH group: %s (%04x)",
if (mbedtls_ssl_tls13_named_group_is_ecdhe(group) ||
mbedtls_ssl_tls13_named_group_is_dhe(group)) {
MBEDTLS_SSL_DEBUG_MSG(2, ("ECDH/FFDH group: %s (%04x)",
mbedtls_ssl_named_group_to_str(group),
group));
ret = mbedtls_ssl_tls13_read_public_ecdhe_share(
@ -938,7 +939,7 @@ static int ssl_tls13_parse_key_shares_ext(mbedtls_ssl_context *ssl,
}
return 0;
}
#endif /* PSA_WANT_ALG_ECDH */
#endif /* PSA_WANT_ALG_ECDH || PSA_WANT_ALG_FFDH */
MBEDTLS_CHECK_RETURN_CRITICAL
static int ssl_tls13_client_hello_has_exts(mbedtls_ssl_context *ssl,
@ -1923,6 +1924,18 @@ static int ssl_tls13_generate_and_write_key_share(mbedtls_ssl_context *ssl,
}
} else
#endif /* PSA_WANT_ALG_ECDH */
#if defined(MBEDTLS_DHM_C)
if (mbedtls_ssl_tls13_named_group_is_dhe(named_group)) {
ret = mbedtls_ssl_tls13_generate_and_write_dhe_key_exchange(
ssl, named_group, buf, end, out_len);
if (ret != 0) {
MBEDTLS_SSL_DEBUG_RET(
1, "mbedtls_ssl_tls13_generate_and_write_dhe_key_exchange",
ret);
return ret;
}
} else
#endif /* MBEDTLS_DHM_C */
if (0 /* Other kinds of KEMs */) {
} else {
((void) ssl);