| =pod |
| |
| =head1 NAME |
| |
| SSL_COMP_add_compression_method - handle SSL/TLS integrated compression methods |
| |
| =head1 SYNOPSIS |
| |
| #include <openssl/ssl.h> |
| |
| int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm); |
| |
| =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. |
| |
| =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. |
| |
| The OpenSSL library has the compression methods B<COMP_rle()> and (when |
| especially enabled during compilation) B<COMP_zlib()> available. |
| |
| =head1 WARNINGS |
| |
| Once the identities of the compression methods for the TLS protocol have |
| been standardized, the compression API will most likely be changed. Using |
| it in the current state is not recommended. |
| |
| =head1 RETURN VALUES |
| |
| SSL_COMP_add_compression_method() may return the following values: |
| |
| =over 4 |
| |
| =item C<0> |
| |
| The operation succeeded. |
| |
| =item C<1> |
| |
| The operation failed. Check the error queue to find out the reason. |
| |
| =back |
| |
| =head1 SEE ALSO |
| |
| L<ssl(3)|ssl(3)> |
| |
| =cut |
