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=head1 NAME

SSL_dup, SSL_new, SSL_up_ref - create an SSL structure for a connection

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 SSL *SSL_dup(SSL *s);
 SSL *SSL_new(SSL_CTX *ctx);
 int SSL_up_ref(SSL *s);

=head1 DESCRIPTION

SSL_new() creates a new B<SSL> structure which is needed to hold the
data for a TLS/SSL connection. The new structure inherits the settings
of the underlying context B<ctx>: connection method,
options, verification settings, timeout settings. An B<SSL> structure is
reference counted. Creating an B<SSL> structure for the first time increments
the reference count. Freeing it (using SSL_free) decrements it. When the
reference count drops to zero, any memory or resources allocated to the B<SSL>
structure are freed.

SSL_up_ref() increments the reference count for an
existing B<SSL> structure.

The function SSL_dup() creates and returns a new B<SSL> structure from the same
B<SSL_CTX> that was used to create I<s>. It additionally duplicates a subset of
the settings in I<s> into the new B<SSL> object.

For SSL_dup() to work, the connection MUST be in its initial state and
MUST NOT have yet started the SSL handshake.  For connections that are not in
their initial state SSL_dup() just increments an internal
reference count and returns the I<same> handle.  It may be possible to
use L<SSL_clear(3)> to recycle an SSL handle that is not in its initial
state for reuse, but this is best avoided.  Instead, save and restore
the session, if desired, and construct a fresh handle for each connection.

The subset of settings in I<s> that are duplicated are:

=over 4

=item any session data if configured (including the session_id_context)

=item any tmp_dh settings set via L<SSL_set_tmp_dh(3)>,
L<SSL_set_tmp_dh_callback(3)>, or L<SSL_set_dh_auto(3)>

=item any configured certificates, private keys or certificate chains

=item any configured signature algorithms, or client signature algorithms

=item any DANE settings

=item any Options set via L<SSL_set_options(3)>

=item any Mode set via L<SSL_set_mode(3)>

=item any minimum or maximum protocol settings set via
L<SSL_set_min_proto_version(3)> or L<SSL_set_max_proto_version(3)> (Note: Only
from OpenSSL 1.1.1h and above)

=item any verify mode, callback or depth set via L<SSL_set_verify(3)> or
L<SSL_set_verify_depth(3)> or any configured X509 verification parameters

=item any msg callback or info callback set via L<SSL_set_msg_callback(3)> or
L<SSL_set_info_callback(3)>

=item any default password callback set via L<SSL_set_default_passwd_cb(3)>

=item any session id generation callback set via L<SSL_set_generate_session_id(3)>

=item any configured Cipher List

=item initial accept (server) or connect (client) state

=item the max cert list value set via L<SSL_set_max_cert_list(3)>

=item the read_ahead value set via L<SSL_set_read_ahead(3)>

=item application specific data set via L<SSL_set_ex_data(3)>

=item any CA list or client CA list set via L<SSL_set0_CA_list(3)>,
SSL_set0_client_CA_list() or similar functions

=item any security level settings or callbacks

=item any configured serverinfo data

=item any configured PSK identity hint

=item any configured custom extensions

=item any client certificate types configured via SSL_set1_client_certificate_types

=back

=head1 RETURN VALUES

The following return values can occur:

=over 4

=item NULL

The creation of a new SSL structure failed. Check the error stack to
find out the reason.

=item Pointer to an SSL structure

The return value points to an allocated SSL structure.

SSL_up_ref() returns 1 for success and 0 for failure.

=back

=head1 SEE ALSO

L<SSL_free(3)>, L<SSL_clear(3)>,
L<SSL_CTX_set_options(3)>,
L<SSL_get_SSL_CTX(3)>,
L<ssl(7)>

=head1 COPYRIGHT

Copyright 2000-2023 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>.

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