SSL_COMP_add_compression_methOpeSnSSL_COMP_add_compression_method(3)

NAME    [Toc]    [Back]

       SSL_COMP_add_compression_method - handle SSL/TLS integrated
 compression methods

LIBRARY    [Toc]    [Back]

       libcrypto, -lcrypto

SYNOPSIS    [Toc]    [Back]

        #include <openssl/ssl.h>

        int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);

DESCRIPTION    [Toc]    [Back]

       SSL_COMP_add_compression_method() adds the compression
       method cm with the identifier 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.

NOTES    [Toc]    [Back]

       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_compres-
       sion_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 COMP_rle()
       and (when especially enabled during compilation)
       COMP_zlib() available.

WARNINGS    [Toc]    [Back]

       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.

RETURN VALUES    [Toc]    [Back]

       SSL_COMP_add_compression_method() may return the following
       values:

       1   The operation succeeded.


       0   The operation failed. Check the error queue to find
           out the reason.

SEE ALSO    [Toc]    [Back]

       ssl(3)



2002-08-05                    0SSL_COMP_add_compression_method(3)