Add identifiers and API for configuration of TLS 1.3 key exchanges
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index f49bf2d..029fa42 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -170,6 +170,30 @@
#define MBEDTLS_ERR_SSL_BAD_CONFIG -0x5E80
/*
+ * TLS 1.3 Key Exchange Modes
+ *
+ * Mbed TLS internal identifiers for use with the SSL configuration API
+ * mbedtls_ssl_conf_tls13_key_exchange_modes().
+ */
+
+#define MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_NONE 0
+#define MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK ( 1u << 0 )
+#define MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_EPHEMERAL ( 1u << 1 )
+#define MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL ( 1u << 2 )
+
+/* Convenience macros for sets of key exchanges. */
+#define MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_ALL \
+ ( MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK | \
+ MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_EPHEMERAL | \
+ MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL )
+#define MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_ALL \
+ ( MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK | \
+ MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_EPHEMERAL )
+#define MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL_ALL \
+ ( MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL | \
+ MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_EPHEMERAL )
+
+/*
* Various constants
*/
@@ -1069,6 +1093,11 @@
/** Allowed ciphersuites for (D)TLS 1.2 (0-terminated) */
const int *MBEDTLS_PRIVATE(ciphersuite_list);
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+ /** Allowed TLS 1.3 key exchange modes. */
+ int MBEDTLS_PRIVATE(tls13_kex_modes);
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
+
/** Callback for printing debug output */
void (*MBEDTLS_PRIVATE(f_dbg))(void *, int, const char *, int, const char *);
void *MBEDTLS_PRIVATE(p_dbg); /*!< context for the debug function */
@@ -2561,6 +2590,53 @@
void mbedtls_ssl_conf_ciphersuites( mbedtls_ssl_config *conf,
const int *ciphersuites );
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+/**
+ * \brief Set the supported key exchange modes for TLS 1.3 connections.
+ *
+ * In contrast to TLS 1.2, the ciphersuite concept in TLS 1.3 does not
+ * include the choice of key exchange mechanism. It is therefore not
+ * covered by the API mbedtls_ssl_conf_ciphersuites(). See the
+ * documentation of mbedtls_ssl_conf_ciphersuites() for more
+ * information on the ciphersuite concept in TLS 1.2 and TLS 1.3.
+ *
+ * The present function is specific to TLS 1.3 and allows users to
+ * configure the set of supported key exchange mechanisms in TLS 1.3.
+ *
+ * \param conf The SSL configuration the change should apply to.
+ * \param kex_modes A bitwise combination of one or more of the following:
+ * - MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK
+ * This flag enables pure-PSK key exchanges.
+ * - MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_EPHEMERAL
+ * This flag enables combined PSK-ephemeral key exchanges.
+ * - MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL
+ * This flag enables pure-ephemeral key exchanges.
+ * For convenience, the following pre-defined macros are
+ * available for combinations of the above:
+ * - MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_ALL
+ * Includes all of pure-PSK, PSK-ephemeral and pure-ephemeral.
+ * - MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_PSK_ALL
+ * Includes both pure-PSK and combined PSK-ephemeral
+ * key exchanges, but excludes pure-ephemeral key exchanges.
+ * - MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_EPHEMERAL_ALL
+ * Includes both pure-ephemeral and combined PSK-ephemeral
+ * key exchanges.
+ *
+ * \note If a PSK-based key exchange mode shall be supported, applications
+ * must also use the APIs mbedtls_ssl_conf_psk() or
+ * mbedtls_ssl_conf_psk_cb() or mbedtls_ssl_conf_psk_opaque()
+ * to configure the PSKs to be used.
+ *
+ * \note If an ECDHE-based key exchange mode shall be supported,
+ * server-side applications must also provide a certificate via
+ * mbedtls_ssl_conf_own_cert().
+ *
+ */
+
+void mbedtls_ssl_conf_tls13_key_exchange_modes( mbedtls_ssl_config* conf,
+ const int kex_modes );
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
+
#if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
#define MBEDTLS_SSL_UNEXPECTED_CID_IGNORE 0
#define MBEDTLS_SSL_UNEXPECTED_CID_FAIL 1
diff --git a/library/ssl_tls.c b/library/ssl_tls.c
index 97bb7b6..4933980 100644
--- a/library/ssl_tls.c
+++ b/library/ssl_tls.c
@@ -3548,6 +3548,14 @@
conf->ciphersuite_list = ciphersuites;
}
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+void mbedtls_ssl_conf_tls13_key_exchange_modes( mbedtls_ssl_config* conf,
+ const int kex_modes )
+{
+ conf->tls13_kex_modes = kex_modes;
+}
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
+
#if defined(MBEDTLS_X509_CRT_PARSE_C)
void mbedtls_ssl_conf_cert_profile( mbedtls_ssl_config *conf,
const mbedtls_x509_crt_profile *profile )
@@ -6353,6 +6361,13 @@
}
#endif
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+ /*
+ * Allow all TLS 1.3 key exchange modes by default.
+ */
+ conf->tls13_kex_modes = MBEDTLS_SSL_TLS13_KEY_EXCHANGE_MODE_ALL;
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
+
/*
* Preset-specific defaults
*/
