Add support for FFDH in TLS 1.3
Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index e347853..8f14349 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -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 @@
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 @@
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 @@
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 @@
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 @@
* 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 @@
*/
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 @@
/* 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 @@
* 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;
+ }
}
-
- /* We found a match */
- found = 1;
- break;
+ if (mbedtls_ssl_tls13_named_group_is_dhe(*group_list)) {
+ found = 1;
+ break;
+ }
}
/* Client MUST verify that the selected_group field does not
@@ -482,24 +506,34 @@
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 {
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index a00785b..a7fddf9 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -1571,6 +1571,68 @@
}
#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
diff --git a/library/ssl_tls13_keys.c b/library/ssl_tls13_keys.c
index 46caa45..c69078d 100644
--- a/library/ssl_tls13_keys.c
+++ b/library/ssl_tls13_keys.c
@@ -1484,8 +1484,15 @@
* 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 @@
}
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 @@
}
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;
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index dc3c2f0..31c6b17 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -836,7 +836,7 @@
#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 @@
}
/*
- * 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 @@
}
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 @@
}
} 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);