add key_share extension
Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ecdh.c b/library/ecdh.c
index 9dfa868..ac60165 100644
--- a/library/ecdh.c
+++ b/library/ecdh.c
@@ -31,6 +31,7 @@
#include "mbedtls/ecdh.h"
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
+#include "ssl_misc.h"
#include <string.h>
@@ -726,4 +727,88 @@
#endif
}
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+
+static int ecdh_tls13_make_params_internal( mbedtls_ecdh_context_mbed *ctx,
+ size_t *olen, int point_format,
+ unsigned char *buf, size_t blen,
+ int ( *f_rng )( void *,
+ unsigned char *,
+ size_t),
+ void *p_rng, int restart_enabled )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+#if defined(MBEDTLS_ECP_RESTARTABLE)
+ mbedtls_ecp_restart_ctx *rs_ctx = NULL;
+#endif
+
+ if( ctx->grp.pbits == 0 )
+ return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
+
+#if defined(MBEDTLS_ECP_RESTARTABLE)
+ if( restart_enabled )
+ rs_ctx = &ctx->rs;
+#else
+ (void) restart_enabled;
+#endif
+
+#if defined(MBEDTLS_ECP_RESTARTABLE)
+ if( ( ret = ecdh_gen_public_restartable( &ctx->grp, &ctx->d, &ctx->Q,
+ f_rng, p_rng, rs_ctx ) ) != 0 )
+ return( ret );
+#else
+ if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q,
+ f_rng, p_rng ) ) != 0 )
+ return( ret );
+#endif /* MBEDTLS_ECP_RESTARTABLE */
+
+ ret = mbedtls_ecp_point_write_binary( &ctx->grp, &ctx->Q, point_format,
+ olen, buf, blen );
+ if( ret != 0 )
+ return( ret );
+
+ return( 0 );
+}
+
+int mbedtls_ecdh_tls13_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
+ unsigned char *buf, size_t blen,
+ int ( *f_rng )( void *, unsigned char *, size_t ),
+ void *p_rng )
+{
+ int restart_enabled = 0;
+ ECDH_VALIDATE_RET( ctx != NULL );
+ ECDH_VALIDATE_RET( olen != NULL );
+ ECDH_VALIDATE_RET( buf != NULL );
+ ECDH_VALIDATE_RET( f_rng != NULL );
+
+#if defined(MBEDTLS_ECP_RESTARTABLE)
+ restart_enabled = ctx->restart_enabled;
+#else
+ (void) restart_enabled;
+#endif
+
+#if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
+ return( ecdh_tls13_make_params_internal( ctx, olen, ctx->point_format, buf, blen,
+ f_rng, p_rng, restart_enabled ) );
+#else
+ switch( ctx->var )
+ {
+#if defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED)
+ case MBEDTLS_ECDH_VARIANT_EVEREST:
+ return( mbedtls_everest_make_params( &ctx->ctx.everest_ecdh, olen,
+ buf, blen, f_rng, p_rng ) );
+#endif
+ case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
+ return( ecdh_tls13_make_params_internal( &ctx->ctx.mbed_ecdh, olen,
+ ctx->point_format, buf, blen,
+ f_rng, p_rng,
+ restart_enabled ) );
+ default:
+ return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
+ }
+#endif
+}
+
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
+
#endif /* MBEDTLS_ECDH_C */
diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index d9c8296..f8f5fe6 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -649,6 +649,16 @@
void (*calc_finished)(mbedtls_ssl_context *, unsigned char *, int);
mbedtls_ssl_tls_prf_cb *tls_prf;
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
+ uint16_t offered_group_id; /* The NamedGroup value for the group
+ * that is being used for ephemeral
+ * key exchange.
+ *
+ * On the client: Defaults to the first
+ * entry in the client's group list,
+ * but can be overwritten by the HRR. */
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
+
mbedtls_ssl_ciphersuite_t const *ciphersuite_info;
size_t pmslen; /*!< premaster length */
@@ -1491,6 +1501,16 @@
unsigned char *buf,
unsigned char *end,
size_t *olen);
+#if defined(MBEDTLS_ECDH_C)
+/*
+ * TLS 1.3 version of mbedtls_ecdh_make_params in ecdh.h
+ */
+int mbedtls_ecdh_tls13_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
+ unsigned char *buf, size_t blen,
+ int ( *f_rng )( void *, unsigned char *, size_t ),
+ void *p_rng );
+#endif /* MBEDTLS_ECDH_C */
+
#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
#endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
diff --git a/library/ssl_tls13_client.c b/library/ssl_tls13_client.c
index df2f9eb..8323b67 100644
--- a/library/ssl_tls13_client.c
+++ b/library/ssl_tls13_client.c
@@ -28,7 +28,8 @@
#include <string.h>
#include "ssl_misc.h"
-#include <mbedtls/debug.h>
+#include "mbedtls/debug.h"
+#include "mbedtls/error.h"
#define CLIENT_HELLO_RANDOM_LEN 32
@@ -257,24 +258,212 @@
return( ret );
}
-static int ssl_tls13_write_key_shares_ext( mbedtls_ssl_context *ssl,
- unsigned char *buf,
- unsigned char *end,
- size_t *olen )
+/*
+ * Functions for writing key_share extension.
+ */
+#if defined(MBEDTLS_ECDH_C)
+static int ssl_key_share_gen_and_write_ecdhe( mbedtls_ssl_context *ssl,
+ uint16_t named_group,
+ unsigned char *buf,
+ unsigned char *end,
+ size_t *olen )
{
- ((void) ssl);
- ((void) buf);
- ((void) end);
- *olen = 0;
- MBEDTLS_SSL_DEBUG_MSG( 3, ( "key share extension is not available" ) );
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+ const mbedtls_ecp_curve_info *curve_info =
+ mbedtls_ecp_curve_info_from_tls_id( named_group );
+
+ if( curve_info == NULL )
+ return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "offer curve %s", curve_info->name ) );
+
+ if( ( ret = mbedtls_ecdh_setup( &ssl->handshake->ecdh_ctx,
+ curve_info->grp_id ) ) != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecp_group_load", ret );
+ return( ret );
+ }
+
+ ret = mbedtls_ecdh_tls13_make_params( &ssl->handshake->ecdh_ctx, olen,
+ buf, end - buf,
+ ssl->conf->f_rng, ssl->conf->p_rng );
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ecdh_tls13_make_params", ret );
+ return( ret );
+ }
+
+ MBEDTLS_SSL_DEBUG_ECDH( 3, &ssl->handshake->ecdh_ctx,
+ MBEDTLS_DEBUG_ECDH_Q );
return( 0 );
}
+#endif /* MBEDTLS_ECDH_C */
+
+static int ssl_named_group_get_default_id( mbedtls_ssl_context *ssl,
+ uint16_t *named_group_id )
+{
+ int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
+
+ /* Pick first entry of curve list.
+ *
+ * TODO: When we introduce PQC KEMs, we'll have a NamedGroup
+ * list instead, and can just return its first element.
+ */
+
+ /* Check if ecdhe named groups are available and pick first entry */
+#if defined(MBEDTLS_ECDH_C)
+#if !defined(MBEDTLS_ECP_C)
+ ((void) ssl);
+#endif
+#if defined(MBEDTLS_ECP_C)
+ for ( const mbedtls_ecp_group_id * grp_id = ssl->conf->curve_list;
+ *grp_id != MBEDTLS_ECP_DP_NONE;
+ grp_id++ )
+ {
+ const mbedtls_ecp_curve_info *info;
+ info = mbedtls_ecp_curve_info_from_grp_id( *grp_id );
+#else
+ for ( const mbedtls_ecp_curve_info *info = mbedtls_ecp_curve_list();
+ info->grp_id != MBEDTLS_ECP_DP_NONE;
+ info++ )
+ {
+#endif
+ if( info != NULL && mbedtls_ssl_named_group_is_ecdhe( info->tls_id ) )
+ {
+ *named_group_id = info->tls_id;
+ return( 0 );
+ }
+ }
+#else
+ ((void) ssl);
+ ((void) named_group_id);
+#endif /* MBEDTLS_ECDH_C */
+
+ /*
+ * Add DHE named groups here.
+ * Check if ecdhe named groups are available and pick first entry
+ */
+
+ return( ret );
+}
+
+/*
+ * ssl_tls13_write_key_share_ext
+ *
+ * Structure of key_share extension in ClientHelo:
+ *
+ * struct {
+ * NamedGroup group;
+ * opaque key_exchange<1..2^16-1>;
+ * } KeyShareEntry;
+ * struct {
+ * KeyShareEntry client_shares<0..2^16-1>;
+ * } KeyShareClientHello;
+ */
+static int ssl_tls13_write_key_share_ext( mbedtls_ssl_context *ssl,
+ unsigned char *buf,
+ unsigned char *end,
+ size_t *olen )
+{
+ unsigned char *p = buf;
+ unsigned char *client_shares_ptr; /* Start of client_shares */
+ uint16_t group_id;
+
+ int ret = MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE;
+
+ *olen = 0;
+
+ if( !mbedtls_ssl_conf_tls13_some_ephemeral_enabled( ssl ) )
+ return( 0 );
+
+ /* Check if we have space for headers and length fields:
+ * - extension_type (2 bytes)
+ * - extension_data_length (2 bytes)
+ * - client_shares_length (2 bytes)
+ */
+ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 6 );
+ p += 6;
+
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello: adding key share extension" ) );
+
+ /* HRR could already have requested something else. */
+ group_id = ssl->handshake->offered_group_id;
+ if( !mbedtls_ssl_named_group_is_ecdhe( group_id ) &&
+ !mbedtls_ssl_named_group_is_dhe( group_id ) )
+ {
+ MBEDTLS_SSL_PROC_CHK( ssl_named_group_get_default_id( ssl,
+ &group_id ) );
+ }
+
+ /*
+ * Dispatch to type-specific key generation function.
+ *
+ * So far, we're only supporting ECDHE. With the introduction
+ * of PQC KEMs, we'll want to have multiple branches, one per
+ * type of KEM, and dispatch to the corresponding crypto. And
+ * only one key share entry is allowed.
+ */
+ client_shares_ptr = p;
+#if defined(MBEDTLS_ECDH_C)
+ if( mbedtls_ssl_named_group_is_ecdhe( group_id ) )
+ {
+ /* Pointer of group */
+ unsigned char *group_id_ptr = p;
+ /* Length of key_exchange */
+ size_t key_exchange_len;
+
+ /* Check there is space for header of KeyShareEntry
+ * - group (2 bytes)
+ * - key_exchange_length (2 bytes)
+ */
+ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 4 );
+ p += 4;
+ ret = ssl_key_share_gen_and_write_ecdhe( ssl, group_id,
+ p, end,
+ &key_exchange_len );
+ p += key_exchange_len;
+ if( ret != 0 )
+ return( ret );
+
+ /* Write group */
+ MBEDTLS_PUT_UINT16_BE( group_id, group_id_ptr, 0 );
+ /* Write key_exchange_length */
+ MBEDTLS_PUT_UINT16_BE( key_exchange_len, group_id_ptr, 2 );
+ }
+ else
+#endif /* MBEDTLS_ECDH_C */
+ if( 0 /* other KEMs? */ )
+ {
+ /* Do something */
+ }
+ else
+ return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
+
+ /* Write extension_type */
+ MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_KEY_SHARE, buf, 0 );
+ /* Write extension_data_length */
+ MBEDTLS_PUT_UINT16_BE( p - client_shares_ptr + 2, buf, 2 );
+ /* Write client_shares_length */
+ MBEDTLS_PUT_UINT16_BE( p - client_shares_ptr, buf, 4 );
+
+ /* Update offered_group_id field */
+ ssl->handshake->offered_group_id = group_id;
+
+ /* Output the total length of key_share extension. */
+ *olen = p - buf;
+
+ MBEDTLS_SSL_DEBUG_BUF( 3, "client hello, key_share extension", buf, *olen );
+
+ ssl->handshake->extensions_present |= MBEDTLS_SSL_EXT_KEY_SHARE;
+
+cleanup:
+
+ return( ret );
+}
#endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
-/*
- * Functions for writing ClientHello message.
- */
/* Write cipher_suites
* CipherSuite cipher_suites<2..2^16-2>;
*/
@@ -464,7 +653,7 @@
* 3) Or, in case all ciphers are supported ( which includes #1 and #2
* from above )
*/
- ret = ssl_tls13_write_key_shares_ext( ssl, p, end, &output_len );
+ ret = ssl_tls13_write_key_share_ext( ssl, p, end, &output_len );
if( ret != 0 )
return( ret );
p += output_len;