/src/gnutls/lib/ext/dumbfw.c
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1 | | /* |
2 | | * Copyright (C) 2013-2018 Nikos Mavrogiannopoulos |
3 | | * Copyright (C) 2018 Red Hat, Inc. |
4 | | * |
5 | | * This file is part of GnuTLS. |
6 | | * |
7 | | * The GnuTLS is free software; you can redistribute it and/or |
8 | | * modify it under the terms of the GNU Lesser General Public License |
9 | | * as published by the Free Software Foundation; either version 2.1 of |
10 | | * the License, or (at your option) any later version. |
11 | | * |
12 | | * This library is distributed in the hope that it will be useful, but |
13 | | * WITHOUT ANY WARRANTY; without even the implied warranty of |
14 | | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
15 | | * Lesser General Public License for more details. |
16 | | * |
17 | | * You should have received a copy of the GNU Lesser General Public License |
18 | | * along with this program. If not, see <https://www.gnu.org/licenses/> |
19 | | * |
20 | | */ |
21 | | |
22 | | #include "gnutls_int.h" |
23 | | #include "auth.h" |
24 | | #include "errors.h" |
25 | | #include "num.h" |
26 | | #include "ext/dumbfw.h" |
27 | | |
28 | | /* This extension adds additional padding data in the TLS client hello. |
29 | | * There is an issue with some firewalls [0] rejecting TLS client hello |
30 | | * data that are between 256 and 511 bytes, and this extension will |
31 | | * make sure that client hello isn't in this range. |
32 | | * |
33 | | * [0]. https://www.ietf.org/mail-archive/web/tls/current/msg10423.html |
34 | | */ |
35 | | |
36 | | static int _gnutls_dumbfw_send_params(gnutls_session_t session, |
37 | | gnutls_buffer_st *extdata); |
38 | | |
39 | | const hello_ext_entry_st ext_mod_dumbfw = { |
40 | | .name = "ClientHello Padding", |
41 | | .tls_id = 21, |
42 | | .gid = GNUTLS_EXTENSION_DUMBFW, |
43 | | .client_parse_point = GNUTLS_EXT_APPLICATION, |
44 | | .server_parse_point = GNUTLS_EXT_APPLICATION, |
45 | | .validity = GNUTLS_EXT_FLAG_TLS | GNUTLS_EXT_FLAG_CLIENT_HELLO, |
46 | | .recv_func = NULL, |
47 | | .send_func = _gnutls_dumbfw_send_params, |
48 | | .pack_func = NULL, |
49 | | .unpack_func = NULL, |
50 | | .deinit_func = NULL, |
51 | | .cannot_be_overriden = 0 |
52 | | }; |
53 | | |
54 | | static int _gnutls_dumbfw_send_params(gnutls_session_t session, |
55 | | gnutls_buffer_st *extdata) |
56 | 0 | { |
57 | 0 | int total_size = 0, ret; |
58 | 0 | uint8_t pad[257]; |
59 | 0 | unsigned pad_size; |
60 | 0 | ssize_t len = extdata->length - sizeof(mbuffer_st); |
61 | |
|
62 | 0 | if (session->security_parameters.entity == GNUTLS_SERVER || |
63 | 0 | session->internals.dumbfw == 0 || IS_DTLS(session) != 0 || |
64 | 0 | (len < 256 || len >= 512)) { |
65 | 0 | return 0; |
66 | 0 | } else { |
67 | | /* 256 <= extdata->length < 512 */ |
68 | 0 | pad_size = 512 - len; |
69 | 0 | memset(pad, 0, pad_size); |
70 | |
|
71 | 0 | ret = gnutls_buffer_append_data(extdata, pad, pad_size); |
72 | 0 | if (ret < 0) |
73 | 0 | return gnutls_assert_val(ret); |
74 | | |
75 | 0 | total_size += pad_size; |
76 | 0 | } |
77 | | |
78 | 0 | return total_size; |
79 | 0 | } |