openssl/doc/man3/SSL_COMP_add_compression_method.pod
Dr. Matthias St. Pierre fc5ecaddd0 man: harmonize the various formulations in the HISTORY sections
While stereotyped repetitions are frowned upon in literature, they
serve a useful purpose in manual pages, because it is easier for
the user to find certain information if it is always presented in
the same way. For that reason, this commit harmonizes the varying
formulations in the HISTORY section about which functions, flags,
etc. were added in which OpenSSL version.

It also attempts to make the pod files more grep friendly by
avoiding to insert line breaks between the symbol names and the
corresponding version number in which they were introduced
(wherever possible). Some punctuation and typographical errors
were fixed on the way.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7854)
2018-12-15 22:27:26 +01:00

106 lines
3.6 KiB
Text

=pod
=head1 NAME
SSL_COMP_add_compression_method, SSL_COMP_get_compression_methods,
SSL_COMP_get0_name, SSL_COMP_get_id, SSL_COMP_free_compression_methods
- handle SSL/TLS integrated compression methods
=head1 SYNOPSIS
#include <openssl/ssl.h>
int SSL_COMP_add_compression_method(int id, COMP_METHOD *cm);
STACK_OF(SSL_COMP) *SSL_COMP_get_compression_methods(void);
const char *SSL_COMP_get0_name(const SSL_COMP *comp);
int SSL_COMP_get_id(const SSL_COMP *comp);
Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining
B<OPENSSL_API_COMPAT> with a suitable version value, see
L<openssl_user_macros(7)>:
void SSL_COMP_free_compression_methods(void)
=head1 DESCRIPTION
SSL_COMP_add_compression_method() adds the compression method B<cm> with
the identifier B<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_get_compression_methods() returns a stack of all of the available
compression methods or NULL on error.
SSL_COMP_get0_name() returns the name of the compression method B<comp>.
SSL_COMP_get_id() returns the id of the compression method B<comp>.
SSL_COMP_free_compression_methods() releases any resources acquired to
maintain the internal table of compression methods.
=head1 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.
=head1 RETURN VALUES
SSL_COMP_add_compression_method() may return the following values:
=over 4
=item Z<>0
The operation succeeded.
=item Z<>1
The operation failed. Check the error queue to find out the reason.
=back
SSL_COMP_get_compression_methods() returns the stack of compressions methods or
NULL on error.
SSL_COMP_get0_name() returns the name of the compression method or NULL on error.
SSL_COMP_get_id() returns the name of the compression method or -1 on error.
=head1 SEE ALSO
L<ssl(7)>
=head1 HISTORY
The SSL_COMP_free_compression_methods() function was deprecated in OpenSSL 1.1.0.
The SSL_COMP_get0_name() and SSL_comp_get_id() functions were added in OpenSSL 1.1.0d.
=head1 COPYRIGHT
Copyright 2001-2016 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
L<https://www.openssl.org/source/license.html>.
=cut