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336736ef LJ |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
e304d3e2 MC |
5 | SSL_COMP_add_compression_method, SSL_COMP_get_compression_methods, |
6 | SSL_COMP_get0_name, SSL_COMP_get_id, SSL_COMP_free_compression_methods | |
7 | - handle SSL/TLS integrated compression methods | |
336736ef LJ |
8 | |
9 | =head1 SYNOPSIS | |
10 | ||
11 | #include <openssl/ssl.h> | |
12 | ||
13 | int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm); | |
e304d3e2 MC |
14 | STACK_OF(SSL_COMP) *SSL_COMP_get_compression_methods(void); |
15 | const char *SSL_COMP_get0_name(const SSL_COMP *comp); | |
16 | int SSL_COMP_get_id(const SSL_COMP *comp); | |
336736ef | 17 | |
be80b21d RL |
18 | Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining |
19 | B<OPENSSL_API_COMPAT> with a suitable version value, see | |
20 | L<openssl_user_macros(7)>: | |
03b0e735 | 21 | |
1d5099de | 22 | void SSL_COMP_free_compression_methods(void) |
c490a551 | 23 | |
336736ef LJ |
24 | =head1 DESCRIPTION |
25 | ||
26 | SSL_COMP_add_compression_method() adds the compression method B<cm> with | |
27 | the identifier B<id> to the list of available compression methods. This | |
28 | list is globally maintained for all SSL operations within this application. | |
29 | It cannot be set for specific SSL_CTX or SSL objects. | |
30 | ||
e304d3e2 MC |
31 | SSL_COMP_get_compression_methods() returns a stack of all of the available |
32 | compression methods or NULL on error. | |
33 | ||
34 | SSL_COMP_get0_name() returns the name of the compression method B<comp>. | |
35 | ||
36 | SSL_COMP_get_id() returns the id of the compression method B<comp>. | |
37 | ||
b3696a55 RS |
38 | SSL_COMP_free_compression_methods() releases any resources acquired to |
39 | maintain the internal table of compression methods. | |
c490a551 | 40 | |
336736ef LJ |
41 | =head1 NOTES |
42 | ||
43 | The TLS standard (or SSLv3) allows the integration of compression methods | |
44 | into the communication. The TLS RFC does however not specify compression | |
45 | methods or their corresponding identifiers, so there is currently no compatible | |
46 | way to integrate compression with unknown peers. It is therefore currently not | |
47 | recommended to integrate compression into applications. Applications for | |
48 | non-public use may agree on certain compression methods. Using different | |
49 | compression methods with the same identifier will lead to connection failure. | |
50 | ||
51 | An OpenSSL client speaking a protocol that allows compression (SSLv3, TLSv1) | |
52 | will unconditionally send the list of all compression methods enabled with | |
53 | SSL_COMP_add_compression_method() to the server during the handshake. | |
54 | Unlike the mechanisms to set a cipher list, there is no method available to | |
55 | restrict the list of compression method on a per connection basis. | |
56 | ||
57 | An OpenSSL server will match the identifiers listed by a client against | |
58 | its own compression methods and will unconditionally activate compression | |
59 | when a matching identifier is found. There is no way to restrict the list | |
60 | of compression methods supported on a per connection basis. | |
61 | ||
c490a551 RS |
62 | If enabled during compilation, the OpenSSL library will have the |
63 | COMP_zlib() compression method available. | |
336736ef LJ |
64 | |
65 | =head1 RETURN VALUES | |
66 | ||
67 | SSL_COMP_add_compression_method() may return the following values: | |
68 | ||
69 | =over 4 | |
70 | ||
c8919dde | 71 | =item Z<>0 |
336736ef LJ |
72 | |
73 | The operation succeeded. | |
74 | ||
c8919dde | 75 | =item Z<>1 |
336736ef LJ |
76 | |
77 | The operation failed. Check the error queue to find out the reason. | |
78 | ||
79 | =back | |
80 | ||
e304d3e2 MC |
81 | SSL_COMP_get_compression_methods() returns the stack of compressions methods or |
82 | NULL on error. | |
83 | ||
84 | SSL_COMP_get0_name() returns the name of the compression method or NULL on error. | |
85 | ||
86 | SSL_COMP_get_id() returns the name of the compression method or -1 on error. | |
87 | ||
336736ef LJ |
88 | =head1 SEE ALSO |
89 | ||
b97fdb57 | 90 | L<ssl(7)> |
336736ef | 91 | |
03b0e735 MC |
92 | =head1 HISTORY |
93 | ||
fc5ecadd DMSP |
94 | The SSL_COMP_free_compression_methods() function was deprecated in OpenSSL 1.1.0. |
95 | The SSL_COMP_get0_name() and SSL_comp_get_id() functions were added in OpenSSL 1.1.0d. | |
03b0e735 | 96 | |
e2f92610 RS |
97 | =head1 COPYRIGHT |
98 | ||
99 | Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved. | |
100 | ||
4746f25a | 101 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
102 | this file except in compliance with the License. You can obtain a copy |
103 | in the file LICENSE in the source distribution or at | |
104 | L<https://www.openssl.org/source/license.html>. | |
105 | ||
106 | =cut |