SSL_COMP_add_compression_metOSSL_COMP_add_compression_method(3)





NAME
       SSL_COMP_add_compression_method - handle SSL/TLS inte-
       grated compression methods

SYNOPSIS
        #include <openssl/ssl.h>

        int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);

DESCRIPTION
       SSL_COMP_add_compression_method() adds the compression
       method cm with the identifier id to the list of avail-
       able compression methods. This list is globally main-
       tained for all SSL operations within this application.
       It cannot be set for specific SSL_CTX or SSL objects.

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 com-
       patible way to integrate compression with unknown peers.
       It is therefore currently not recommended to integrate
       compression into applications. Applications for non-pub-
       lic 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 com-
       pression (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 connec-
       tion basis.

       The OpenSSL library has the compression methods
       COMP_rle() and (when especially enabled during compila-
       tion) COMP_zlib() available.

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.

RETURN VALUES
       SSL_COMP_add_compression_method() may return the follow-
       ing values:

       1   The operation succeeded.

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

SEE ALSO
       ssl(3)



