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

#include <openssl/ssl.h>

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

SSL_new() creates a new SSL structure which is needed to hold the data for a TLS/SSL connection. The new structure inherits the settings of the underlying context ctx: connection method, options, verification settings, timeout settings. An SSL structure is reference counted. Creating an 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 SSL structure are freed.

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

The function SSL_dup() creates and returns a new SSL structure from the same SSL_CTX that was used to create s. It additionally duplicates a subset of the settings in s into the new 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 same handle. It may be possible to use SSL_clear(3) to recycle an SSL handle that is not in its initial state for re-use, 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 s that are duplicated are:

any session data if configured (including the session_id_context)
any tmp_dh settings set via SSL_set_tmp_dh(3), SSL_set_tmp_dh_callback(3), or SSL_set_dh_auto(3)
any configured certificates, private keys or certificate chains
any configured signature algorithms, or client signature algorithms
any DANE settings
any Options set via SSL_set_options(3)
any Mode set via SSL_set_mode(3)
any minimum or maximum protocol settings set via SSL_set_min_proto_version(3) or SSL_set_max_proto_version(3) (Note: Only from OpenSSL 1.1.1h and above)
any Verify mode, callback or depth set via SSL_set_verify(3) or SSL_set_verify_depth(3) or any configured X509 verification parameters
any msg callback or info callback set via SSL_set_msg_callback(3) or SSL_set_info_callback(3)
any default password callback set via SSL_set_default_passwd_cb(3)
any session id generation callback set via SSL_set_generate_session_id(3)
any configured Cipher List
initial accept (server) or connect (client) state
the max cert list value set via SSL_set_max_cert_list(3)
the read_ahead value set via SSL_set_read_ahead(3)
application specific data set via SSL_set_ex_data(3)
any CA list or client CA list set via SSL_set0_CA_list(3), SSL_set0_client_CA_list() or similar functions
any security level settings or callbacks
any configured serverinfo data
any configured PSK identity hint
any configured custom extensions
any client certificate types configured via SSL_set1_client_certificate_types

The following return values can occur:
The creation of a new SSL structure failed. Check the error stack to find out the reason.
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.

SSL_free(3), SSL_clear(3), SSL_CTX_set_options(3), SSL_get_SSL_CTX(3), ssl(7)

Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (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

2021-03-25 1.1.1k