diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 141c40a4e..abf33a634 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -809,6 +809,14 @@ struct mbedtls_ssl_handshake_params
size_t digest_len;
} finished_in;
+#if defined(MBEDTLS_SSL_SRV_C)
+ /* Server, outgoing ClientKeyExchange */
+ struct
+ {
+ uint8_t preparation_done;
+ } encrypted_extensions_out;
+#endif /* MBEDTLS_SSL_SRV_C */
+
} state_local;
/* End of state-local variables. */
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index d06b9a88e..72ac8ad50 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -22,10 +22,186 @@
#if defined(MBEDTLS_SSL_SRV_C) && defined(MBEDTLS_SSL_PROTO_TLS1_3)
#include "mbedtls/debug.h"
+#include "mbedtls/error.h"
+#include "mbedtls/platform.h"
+#include <string.h>
#include "ssl_misc.h"
#include "ssl_tls13_keys.h"
#include "ssl_debug_helpers.h"
+#include "ecdh_misc.h"
+#include "ssl_tls13_keys.h"
+
+#if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
+/*
+ * struct {
+ * ExtensionType extension_type;
+ * opaque extension_data<0..2^16-1>;
+ * } Extension;
+ */
+static int ssl_tls13_write_sni_server_ext( mbedtls_ssl_context *ssl,
+ unsigned char *buf,
+ unsigned char *end,
+ size_t *out_len )
+{
+ unsigned char *p = buf;
+ *out_len = 0;
+
+ if( ( ssl->handshake->extensions_present &
+ MBEDTLS_SSL_EXT_SERVERNAME ) == 0 )
+ {
+ return( 0 );
+ }
+
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "adding server_name extension" ) );
+
+ /* Check if we have enough space:
+ * - ExtensionType (2 bytes)
+ * - extensions length (2 bytes)
+ */
+ MBEDTLS_SSL_CHK_BUF_PTR( p, end, 4);
+
+ /* Write extension type */
+ MBEDTLS_PUT_UINT16_BE( MBEDTLS_TLS_EXT_SERVERNAME, p, 0 );
+
+ /* Write extension length */
+ MBEDTLS_PUT_UINT16_BE( 0, p, 2 );
+
+ *out_len = 4;
+
+ return( 0 );
+}
+#endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
+
+
+static int ssl_tls13_prepare_encrypted_extensions( mbedtls_ssl_context *ssl )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ mbedtls_ssl_key_set traffic_keys;
+ mbedtls_ssl_transform *transform_handshake = NULL;
+
+ /* Compute handshake secret */
+ ret = mbedtls_ssl_tls13_key_schedule_stage_handshake( ssl );
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_key_schedule_stage_handshake", ret );
+ return( ret );
+ }
+
+ /* Derive handshake key material */
+ ret = mbedtls_ssl_tls13_generate_handshake_keys( ssl, &traffic_keys );
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1,
+ "mbedtls_ssl_tls13_generate_handshake_keys", ret );
+ return( ret );
+ }
+
+ transform_handshake = mbedtls_calloc( 1, sizeof( mbedtls_ssl_transform ) );
+ if( transform_handshake == NULL )
+ return( MBEDTLS_ERR_SSL_ALLOC_FAILED );
+
+ /* Setup transform from handshake key material */
+ ret = mbedtls_ssl_tls13_populate_transform(
+ transform_handshake,
+ ssl->conf->endpoint,
+ ssl->session_negotiate->ciphersuite,
+ &traffic_keys,
+ ssl );
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_tls13_populate_transform", ret );
+ mbedtls_free( transform_handshake );
+ return( ret );
+ }
+
+ ssl->handshake->transform_handshake = transform_handshake;
+ mbedtls_ssl_set_outbound_transform( ssl, ssl->handshake->transform_handshake );
+
+ /*
+ * Switch to our negotiated transform and session parameters for outbound
+ * data.
+ */
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "switching to new transform spec for outbound data" ) );
+ memset( ssl->out_ctr, 0, 8 );
+
+ return( 0 );
+}
+
+/*
+ * struct {
+ * Extension extensions<0..2 ^ 16 - 1>;
+ * } EncryptedExtensions;
+ *
+ */
+static int ssl_tls13_write_encrypted_extensions( mbedtls_ssl_context *ssl,
+ unsigned char *buf,
+ unsigned char *end,
+ size_t *out_len )
+{
+ unsigned char *p = buf;
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ size_t extensions_len = 0;
+ unsigned char *p_extensions_len;
+ size_t length = 0; // length of this extension
+ *out_len = 0;
+
+ /* Skip extension length; first write extensions, then update length */
+ p_extensions_len = p;
+ p += 2;
+
+#if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
+ ret = ssl_tls13_write_sni_server_ext( ssl, p, end, &length );
+ if( ret != 0 )
+ return( ret );
+ p += length;
+#endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
+
+ *out_len = (size_t)( p - buf );
+
+ /* write extensions length */
+ extensions_len = ( p - p_extensions_len ) - 2;
+ MBEDTLS_PUT_UINT16_BE( extensions_len, p_extensions_len, 0);
+
+ return( 0 );
+}
+
+static int ssl_tls13_process_encrypted_extensions( mbedtls_ssl_context *ssl )
+{
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ unsigned char *buf;
+ size_t buf_len = 0;
+ size_t msg_len = 0;
+
+ MBEDTLS_SSL_DEBUG_MSG( 2, ( "=> write encrypted extension" ) );
+
+ if( ssl->handshake->state_local.encrypted_extensions_out.preparation_done == 0 )
+ {
+ MBEDTLS_SSL_PROC_CHK( ssl_tls13_prepare_encrypted_extensions( ssl ) );
+ ssl->handshake->state_local.encrypted_extensions_out.preparation_done = 1;
+ }
+
+ MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_start_handshake_msg( ssl,
+ MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS, &buf, &buf_len ) );
+
+ MBEDTLS_SSL_PROC_CHK( ssl_tls13_write_encrypted_extensions(
+ ssl, buf, buf + buf_len, &msg_len ) );
+
+ mbedtls_ssl_add_hs_msg_to_checksum(
+ ssl, MBEDTLS_SSL_HS_ENCRYPTED_EXTENSIONS, buf, msg_len );
+
+ /* Update state */
+ mbedtls_ssl_handshake_set_state( ssl, MBEDTLS_SSL_CERTIFICATE_REQUEST );
+
+ MBEDTLS_SSL_PROC_CHK( mbedtls_ssl_finish_handshake_msg(
+ ssl, buf_len, msg_len ) );
+
+cleanup:
+
+ MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= write encrypted extension" ) );
+ return( ret );
+}
+
#if defined(MBEDTLS_ECP_C)
#include "mbedtls/ecp.h"
@@ -1089,6 +1265,14 @@ int mbedtls_ssl_tls13_handshake_server_step( mbedtls_ssl_context *ssl )
ret = ssl_tls13_write_server_hello( ssl );
break;
+ case MBEDTLS_SSL_ENCRYPTED_EXTENSIONS:
+ ret = ssl_tls13_process_encrypted_extensions( ssl );
+ if( ret != 0 )
+ {
+ MBEDTLS_SSL_DEBUG_RET( 1, "ssl_tls13_process_encrypted_extensions", ret );
+ }
+ break;
+
default:
MBEDTLS_SSL_DEBUG_MSG( 1, ( "invalid state %d", ssl->state ) );
return( MBEDTLS_ERR_SSL_FEATURE_UNAVAILABLE );