SSL_COMP_add_compression_method - Handle SSL/TLS integrated
COMP_METHOD *cm );
The SSL_COMP_add_compression_method() function 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.
The TLS standard (or SSLv3) allows the integration of compression
methods into the communication. However, the TLS
RFC does not specify compression methods or their corresponding
identifiers, so there is no compatible way to
integrate compression with unknown peers. We do not recommend
integrating 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 COMP_rle()
and (when especially enabled during compilation)
Once the identities of the compression methods for the TLS
protocol have been standardized, the compression API will
most likely be changed. We do not recommend using it in
its current state.
The following return values can occur: The operation
failed. Check the error queue to learn the reason. The
[ Back ]