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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_client_server_name.h"
      17                 :            : 
      18                 :            : #include <stdint.h>
      19                 :            : #include <sys/param.h>
      20                 :            : 
      21                 :            : #include "tls/s2n_tls.h"
      22                 :            : #include "tls/s2n_tls_parameters.h"
      23                 :            : #include "utils/s2n_safety.h"
      24                 :            : 
      25                 :            : #define S2N_NAME_TYPE_HOST_NAME 0
      26                 :            : 
      27                 :            : static bool s2n_client_server_name_should_send(struct s2n_connection *conn);
      28                 :            : static int s2n_client_server_name_send(struct s2n_connection *conn, struct s2n_stuffer *out);
      29                 :            : static int s2n_client_server_name_recv(struct s2n_connection *conn, struct s2n_stuffer *extension);
      30                 :            : 
      31                 :            : const s2n_extension_type s2n_client_server_name_extension = {
      32                 :            :     .iana_value = TLS_EXTENSION_SERVER_NAME,
      33                 :            :     .is_response = false,
      34                 :            :     .send = s2n_client_server_name_send,
      35                 :            :     .recv = s2n_client_server_name_recv,
      36                 :            :     .should_send = s2n_client_server_name_should_send,
      37                 :            :     .if_missing = s2n_extension_noop_if_missing,
      38                 :            : };
      39                 :            : 
      40                 :            : static bool s2n_client_server_name_should_send(struct s2n_connection *conn)
      41                 :       7355 : {
      42 [ +  - ][ +  + ]:       7355 :     return conn && conn->server_name[0] != '\0';
      43                 :       7355 : }
      44                 :            : 
      45                 :            : static int s2n_client_server_name_send(struct s2n_connection *conn, struct s2n_stuffer *out)
      46                 :         79 : {
      47                 :         79 :     struct s2n_stuffer_reservation server_name_list_size = { 0 };
      48         [ -  + ]:         79 :     POSIX_GUARD(s2n_stuffer_reserve_uint16(out, &server_name_list_size));
      49                 :            : 
      50                 :            :     /* NameType, as described by RFC6066.
      51                 :            :      * host_name is currently the only possible NameType defined. */
      52         [ -  + ]:         79 :     POSIX_GUARD(s2n_stuffer_write_uint8(out, S2N_NAME_TYPE_HOST_NAME));
      53                 :            : 
      54         [ -  + ]:         79 :     POSIX_GUARD(s2n_stuffer_write_uint16(out, strlen(conn->server_name)));
      55         [ -  + ]:         79 :     POSIX_GUARD(s2n_stuffer_write_bytes(out, (const uint8_t *) conn->server_name, strlen(conn->server_name)));
      56                 :            : 
      57         [ -  + ]:         79 :     POSIX_GUARD(s2n_stuffer_write_vector_size(&server_name_list_size));
      58                 :         79 :     return S2N_SUCCESS;
      59                 :         79 : }
      60                 :            : 
      61                 :            : /* Read the extension up to the first item in ServerNameList. Instantiates the server_name blob to
      62                 :            :  * point to the first entry. For now s2n ignores all subsequent items in ServerNameList.
      63                 :            :  */
      64                 :            : S2N_RESULT s2n_client_server_name_parse(struct s2n_stuffer *extension, struct s2n_blob *server_name)
      65                 :        113 : {
      66                 :        113 :     uint16_t list_size = 0;
      67         [ -  + ]:        113 :     RESULT_GUARD_POSIX(s2n_stuffer_read_uint16(extension, &list_size));
      68 [ +  + ][ +  - ]:        113 :     RESULT_ENSURE_LTE(list_size, s2n_stuffer_data_available(extension));
      69                 :            : 
      70                 :        111 :     uint8_t server_name_type = 0;
      71         [ -  + ]:        111 :     RESULT_GUARD_POSIX(s2n_stuffer_read_uint8(extension, &server_name_type));
      72 [ +  - ][ +  + ]:        111 :     RESULT_ENSURE_EQ(server_name_type, S2N_NAME_TYPE_HOST_NAME);
      73                 :            : 
      74                 :        110 :     uint16_t length = 0;
      75         [ -  + ]:        110 :     RESULT_GUARD_POSIX(s2n_stuffer_read_uint16(extension, &length));
      76 [ +  + ][ +  - ]:        110 :     RESULT_ENSURE_LTE(length, s2n_stuffer_data_available(extension));
      77                 :            : 
      78                 :        108 :     uint8_t *data = s2n_stuffer_raw_read(extension, length);
      79 [ #  # ][ -  + ]:        108 :     RESULT_ENSURE_REF(data);
      80         [ -  + ]:        108 :     RESULT_GUARD_POSIX(s2n_blob_init(server_name, data, length));
      81                 :            : 
      82                 :        108 :     return S2N_RESULT_OK;
      83                 :        108 : }
      84                 :            : 
      85                 :            : static int s2n_client_server_name_recv(struct s2n_connection *conn, struct s2n_stuffer *extension)
      86                 :        114 : {
      87 [ #  # ][ -  + ]:        114 :     POSIX_ENSURE_REF(conn);
      88                 :            : 
      89                 :            :     /* Exit early if we've already parsed the server name */
      90         [ +  + ]:        114 :     if (conn->server_name[0]) {
      91                 :          4 :         return S2N_SUCCESS;
      92                 :          4 :     }
      93                 :            : 
      94                 :            :     /* Ignore if malformed or we don't have enough space to store it. We just won't use the server name. */
      95                 :        110 :     struct s2n_blob server_name = { 0 };
      96 [ +  + ][ -  + ]:        110 :     if (!s2n_result_is_ok(s2n_client_server_name_parse(extension, &server_name)) || server_name.size > S2N_MAX_SERVER_NAME) {
      97                 :          5 :         return S2N_SUCCESS;
      98                 :          5 :     }
      99                 :            : 
     100 [ -  + ][ #  # ]:        105 :     POSIX_CHECKED_MEMCPY(conn->server_name, server_name.data, server_name.size);
                 [ +  - ]
     101                 :            : 
     102                 :        105 :     return S2N_SUCCESS;
     103                 :        105 : }