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       1                 :            : /*
       2                 :            :  * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
       3                 :            :  *
       4                 :            :  * Licensed under the Apache License, Version 2.0 (the "License").
       5                 :            :  * You may not use this file except in compliance with the License.
       6                 :            :  * A copy of the License is located at
       7                 :            :  *
       8                 :            :  *  http://aws.amazon.com/apache2.0
       9                 :            :  *
      10                 :            :  * or in the "license" file accompanying this file. This file is distributed
      11                 :            :  * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
      12                 :            :  * express or implied. See the License for the specific language governing
      13                 :            :  * permissions and limitations under the License.
      14                 :            :  */
      15                 :            : 
      16                 :            : #include "tls/extensions/s2n_ec_point_format.h"
      17                 :            : 
      18                 :            : #include <stdint.h>
      19                 :            : 
      20                 :            : #include "tls/extensions/s2n_client_supported_groups.h"
      21                 :            : #include "tls/s2n_tls.h"
      22                 :            : #include "utils/s2n_safety.h"
      23                 :            : 
      24                 :            : static int s2n_ec_point_format_send(struct s2n_connection *conn, struct s2n_stuffer *out);
      25                 :            : static int s2n_ec_point_format_recv(struct s2n_connection *conn, struct s2n_stuffer *extension);
      26                 :            : 
      27                 :            : const s2n_extension_type s2n_client_ec_point_format_extension = {
      28                 :            :     .iana_value = TLS_EXTENSION_EC_POINT_FORMATS,
      29                 :            :     .is_response = false,
      30                 :            :     .send = s2n_ec_point_format_send,
      31                 :            :     .recv = s2n_ec_point_format_recv,
      32                 :            :     .should_send = s2n_extension_should_send_if_ecc_enabled,
      33                 :            :     .if_missing = s2n_extension_noop_if_missing,
      34                 :            : };
      35                 :            : 
      36                 :            : static bool s2n_server_ec_point_format_should_send(struct s2n_connection *conn);
      37                 :            : 
      38                 :            : const s2n_extension_type s2n_server_ec_point_format_extension = {
      39                 :            :     .iana_value = TLS_EXTENSION_EC_POINT_FORMATS,
      40                 :            :     .is_response = true,
      41                 :            :     .send = s2n_ec_point_format_send,
      42                 :            :     .recv = s2n_extension_recv_noop,
      43                 :            :     .should_send = s2n_server_ec_point_format_should_send,
      44                 :            :     .if_missing = s2n_extension_noop_if_missing,
      45                 :            : };
      46                 :            : 
      47                 :            : static bool s2n_server_ec_point_format_should_send(struct s2n_connection *conn)
      48                 :       1149 : {
      49 [ +  + ][ +  - ]:       1149 :     return conn && conn->secure && conn->secure->cipher_suite
                 [ +  + ]
      50         [ +  + ]:       1149 :             && s2n_kex_includes(conn->secure->cipher_suite->key_exchange_alg, &s2n_ecdhe);
      51                 :       1149 : }
      52                 :            : 
      53                 :            : static int s2n_ec_point_format_send(struct s2n_connection *conn, struct s2n_stuffer *out)
      54                 :       7366 : {
      55                 :            :     /* Point format list len. We only support one. */
      56         [ -  + ]:       7366 :     POSIX_GUARD(s2n_stuffer_write_uint8(out, 1));
      57                 :            : 
      58                 :            :     /* Only allow uncompressed format */
      59         [ -  + ]:       7366 :     POSIX_GUARD(s2n_stuffer_write_uint8(out, TLS_EC_POINT_FORMAT_UNCOMPRESSED));
      60                 :            : 
      61                 :       7366 :     return S2N_SUCCESS;
      62                 :       7366 : }
      63                 :            : 
      64                 :            : static int s2n_ec_point_format_recv(struct s2n_connection *conn, struct s2n_stuffer *extension)
      65                 :       6481 : {
      66                 :            :     /* Only uncompressed points are supported by the server and the client must include it in
      67                 :            :      * the extension. Just skip the extension.
      68                 :            :      *
      69                 :            :      *= https://www.rfc-editor.org/rfc/rfc8422#section-5.1.2
      70                 :            :      *= type=exception
      71                 :            :      *= reason=Incorrect implementations exist in the wild. Skipping validation.
      72                 :            :      *# If the client sends the extension and the extension does not contain
      73                 :            :      *# the uncompressed point format, and the client has used the Supported
      74                 :            :      *# Groups extension to indicate support for any of the curves defined in
      75                 :            :      *# this specification, then the server MUST abort the handshake and
      76                 :            :      *# return an illegal_parameter alert.
      77                 :            :      */
      78                 :       6481 :     conn->ec_point_formats = 1;
      79                 :       6481 :     return S2N_SUCCESS;
      80                 :       6481 : }