| =pod |
| |
| =head1 NAME |
| |
| SSL_COMP_add_compression_method, SSL_COMP_get_compression_methods, |
| SSL_COMP_get0_name, SSL_COMP_get_id, SSL_COMP_free_compression_methods |
| - handle SSL/TLS integrated compression methods |
| |
| =head1 SYNOPSIS |
| |
| #include <openssl/ssl.h> |
| |
| int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm); |
| STACK_OF(SSL_COMP) *SSL_COMP_get_compression_methods(void); |
| const char *SSL_COMP_get0_name(const SSL_COMP *comp); |
| int SSL_COMP_get_id(const SSL_COMP *comp); |
| |
| Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining |
| B<OPENSSL_API_COMPAT> with a suitable version value, see |
| L<openssl_user_macros(7)>: |
| |
| void SSL_COMP_free_compression_methods(void); |
| |
| =head1 DESCRIPTION |
| |
| SSL_COMP_add_compression_method() adds the compression method B<cm> with |
| the identifier B<id> to the list of available compression methods. This |
| list is globally maintained for all SSL operations within this application. |
| It cannot be set for specific SSL_CTX or SSL objects. |
| |
| SSL_COMP_get_compression_methods() returns a stack of all of the available |
| compression methods or NULL on error. |
| |
| SSL_COMP_get0_name() returns the name of the compression method B<comp>. |
| |
| SSL_COMP_get_id() returns the id of the compression method B<comp>. |
| |
| SSL_COMP_free_compression_methods() releases any resources acquired to |
| maintain the internal table of compression methods. |
| |
| =head1 NOTES |
| |
| The TLS standard (or SSLv3) allows the integration of compression methods |
| into the communication. The TLS RFC does however not specify compression |
| methods or their corresponding identifiers, so there is currently no compatible |
| way to integrate compression with unknown peers. It is therefore currently not |
| recommended to integrate compression into applications. Applications for |
| non-public use may agree on certain compression methods. Using different |
| compression methods with the same identifier will lead to connection failure. |
| |
| An OpenSSL client speaking a protocol that allows compression (SSLv3, TLSv1) |
| will unconditionally send the list of all compression methods enabled with |
| SSL_COMP_add_compression_method() to the server during the handshake. |
| Unlike the mechanisms to set a cipher list, there is no method available to |
| restrict the list of compression method on a per connection basis. |
| |
| An OpenSSL server will match the identifiers listed by a client against |
| its own compression methods and will unconditionally activate compression |
| when a matching identifier is found. There is no way to restrict the list |
| of compression methods supported on a per connection basis. |
| |
| If enabled during compilation, the OpenSSL library will have the |
| COMP_zlib() compression method available. |
| |
| =head1 RETURN VALUES |
| |
| SSL_COMP_add_compression_method() may return the following values: |
| |
| =over 4 |
| |
| =item Z<>0 |
| |
| The operation succeeded. |
| |
| =item Z<>1 |
| |
| The operation failed. Check the error queue to find out the reason. |
| |
| =back |
| |
| SSL_COMP_get_compression_methods() returns the stack of compressions methods or |
| NULL on error. |
| |
| SSL_COMP_get0_name() returns the name of the compression method or NULL on error. |
| |
| SSL_COMP_get_id() returns the name of the compression method or -1 on error. |
| |
| =head1 SEE ALSO |
| |
| L<ssl(7)> |
| |
| =head1 HISTORY |
| |
| The SSL_COMP_free_compression_methods() function was deprecated in OpenSSL 1.1.0. |
| The SSL_COMP_get0_name() and SSL_comp_get_id() functions were added in OpenSSL 1.1.0d. |
| |
| =head1 COPYRIGHT |
| |
| Copyright 2001-2020 The OpenSSL Project Authors. All Rights Reserved. |
| |
| Licensed under the Apache License 2.0 (the "License"). You may not use |
| this file except in compliance with the License. You can obtain a copy |
| in the file LICENSE in the source distribution or at |
| L<https://www.openssl.org/source/license.html>. |
| |
| =cut |
