SSL_COMP_add_compression_method 3 2004-03-19 0.9.9-dev OpenSSL

NAME

SSL_COMP_add_compression_method - handle SSL/TLS integrated compression methods

LIBRARY

libcrypto, -lcrypto

SYNOPSIS


 #include 


 int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);

DESCRIPTION

_S_S_L___C_O_M_P___a_d_d___c_o_m_p_r_e_s_s_i_o_n___m_e_t_h_o_d_(_) adds the compression method ccmm with the identifier iidd 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

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 _S_S_L___C_O_M_P___a_d_d___c_o_m_p_r_e_s_s_i_o_n___m_e_t_h_o_d_(_) 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 _CC_OO_MM_PP____rr_ll_ee_((_)) and (when especially enabled during compilation) _CC_OO_MM_PP____zz_ll_ii_bb_((_)) 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

_S_S_L___C_O_M_P___a_d_d___c_o_m_p_r_e_s_s_i_o_n___m_e_t_h_o_d_(_) may return the following values:
0 The operation succeeded.
1 The operation failed. Check the error queue to find out the reason.

SEE ALSO

_s_s_l(3)