SSL_COMP_add_compression_method - handle SSL/TLS integrated compression methods
#include <openssl/ssl.h> int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm); +void SSL_COMP_free_compression_methods(void);
OpenSSL SSL_COMP_add_compression_method(3openssl)
NAME
SSL_COMP_add_compression_method, SSL_COMP_free_compression_methods -
handle SSL/TLS integrated compression methods
SYNOPSIS
#include <openssl/ssl.h>
int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);
+void SSL_COMP_free_compression_methods(void);
DESCRIPTION
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.
SSL_COMP_free_compression_methods() frees the internal table of
compression methods that were built internally, and possibly augmented
by adding SSL_COMP_add_compression_method().
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | library/security/openssl |
+---------------+--------------------------+
|Stability | Pass-through uncommitted |
+---------------+--------------------------+
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.
If enabled during compilation, the OpenSSL library will have the
COMP_zlib() compression method available.
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from
https://www.openssl.org/source/openssl-1.0.2ze.tar.gz.
Further information about this software can be found on the open source
community website at https://www.openssl.org/.
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 following values:
0 The operation succeeded.
1 The operation failed. Check the error queue to find out the reason.
SEE ALSO
ssl(3)
1.0.2ze 2022-05-03
SSL_COMP_add_compression_method(3openssl)