TLSv1_2_method, TLSv1_2_server_method, TLSv1_2_client_method, SSL_CTX_new,
SSL_CTX_up_ref, SSLv3_method, SSLv3_server_method, SSLv3_client_method,
TLSv1_method, TLSv1_server_method, TLSv1_client_method, TLSv1_1_method,
TLSv1_1_server_method, TLSv1_1_client_method, TLS_method, TLS_server_method,
TLS_client_method, SSLv23_method, SSLv23_server_method, SSLv23_client_method,
DTLS_method, DTLS_server_method, DTLS_client_method, DTLSv1_method,
DTLSv1_server_method, DTLSv1_client_method, DTLSv1_2_method,
DTLSv1_2_server_method, DTLSv1_2_client_method - create a new SSL_CTX object
as framework for TLS/SSL or DTLS enabled functions
#include <openssl/ssl.h>
SSL_CTX *SSL_CTX_new(const SSL_METHOD *method);
int SSL_CTX_up_ref(SSL_CTX *ctx);
const SSL_METHOD *TLS_method(void);
const SSL_METHOD *TLS_server_method(void);
const SSL_METHOD *TLS_client_method(void);
const SSL_METHOD *SSLv23_method(void);
const SSL_METHOD *SSLv23_server_method(void);
const SSL_METHOD *SSLv23_client_method(void);
#ifndef OPENSSL_NO_SSL3_METHOD
const SSL_METHOD *SSLv3_method(void);
const SSL_METHOD *SSLv3_server_method(void);
const SSL_METHOD *SSLv3_client_method(void);
#endif
#ifndef OPENSSL_NO_TLS1_METHOD
const SSL_METHOD *TLSv1_method(void);
const SSL_METHOD *TLSv1_server_method(void);
const SSL_METHOD *TLSv1_client_method(void);
#endif
#ifndef OPENSSL_NO_TLS1_1_METHOD
const SSL_METHOD *TLSv1_1_method(void);
const SSL_METHOD *TLSv1_1_server_method(void);
const SSL_METHOD *TLSv1_1_client_method(void);
#endif
#ifndef OPENSSL_NO_TLS1_2_METHOD
const SSL_METHOD *TLSv1_2_method(void);
const SSL_METHOD *TLSv1_2_server_method(void);
const SSL_METHOD *TLSv1_2_client_method(void);
#endif
const SSL_METHOD *DTLS_method(void);
const SSL_METHOD *DTLS_server_method(void);
const SSL_METHOD *DTLS_client_method(void);
#ifndef OPENSSL_NO_DTLS1_METHOD
const SSL_METHOD *DTLSv1_method(void);
const SSL_METHOD *DTLSv1_server_method(void);
const SSL_METHOD *DTLSv1_client_method(void);
#endif
#ifndef OPENSSL_NO_DTLS1_2_METHOD
const SSL_METHOD *DTLSv1_2_method(void);
const SSL_METHOD *DTLSv1_2_server_method(void);
const SSL_METHOD *DTLSv1_2_client_method(void);
#endif
SSL_CTX_new() creates a new SSL_CTX object as framework to
establish TLS/SSL or DTLS enabled connections. An SSL_CTX object is
reference counted. Creating an SSL_CTX object for the first time
increments the reference count. Freeing it (using SSL_CTX_free) decrements it.
When the reference count drops to zero, any memory or resources allocated to
the SSL_CTX object are freed. SSL_CTX_up_ref() increments the
reference count for an existing SSL_CTX structure.
The SSL_CTX object uses method as connection method. The methods exist in
a generic type (for client and server use), a server only type, and a client
only type. method can be of the following types:
- TLS_method(), TLS_server_method(),
TLS_client_method()
- These are the general-purpose version-flexible SSL/TLS methods. The
actual protocol version used will be negotiated to the highest version
mutually supported by the client and the server. The supported protocols
are SSLv3, TLSv1, TLSv1.1, TLSv1.2 and TLSv1.3. Applications should use
these methods, and avoid the version-specific methods described below,
which are deprecated.
- SSLv23_method(), SSLv23_server_method(),
SSLv23_client_method()
- These functions do not exist anymore, they have been renamed to
TLS_method(), TLS_server_method() and
TLS_client_method() respectively. Currently, the old function calls
are renamed to the corresponding new ones by preprocessor macros, to
ensure that existing code which uses the old function names still
compiles. However, using the old function names is deprecated and new code
should call the new functions instead.
- TLSv1_2_method(), TLSv1_2_server_method(),
TLSv1_2_client_method()
- A TLS/SSL connection established with these methods will only understand
the TLSv1.2 protocol. These methods are deprecated.
- TLSv1_1_method(), TLSv1_1_server_method(),
TLSv1_1_client_method()
- A TLS/SSL connection established with these methods will only understand
the TLSv1.1 protocol. These methods are deprecated.
- TLSv1_method(), TLSv1_server_method(),
TLSv1_client_method()
- A TLS/SSL connection established with these methods will only understand
the TLSv1 protocol. These methods are deprecated.
- SSLv3_method(), SSLv3_server_method(),
SSLv3_client_method()
- A TLS/SSL connection established with these methods will only understand
the SSLv3 protocol. The SSLv3 protocol is deprecated and should not be
used.
- DTLS_method(), DTLS_server_method(),
DTLS_client_method()
- These are the version-flexible DTLS methods. Currently supported protocols
are DTLS 1.0 and DTLS 1.2.
- DTLSv1_2_method(), DTLSv1_2_server_method(),
DTLSv1_2_client_method()
- These are the version-specific methods for DTLSv1.2. These methods are
deprecated.
- DTLSv1_method(), DTLSv1_server_method(),
DTLSv1_client_method()
- These are the version-specific methods for DTLSv1. These methods are
deprecated.
SSL_CTX_new() initializes the list of ciphers, the session
cache setting, the callbacks, the keys and certificates and the options to
their default values.
TLS_method(), TLS_server_method(),
TLS_client_method(), DTLS_method(),
DTLS_server_method() and DTLS_client_method() are the
version-flexible methods. All other methods only support one specific
protocol version. Use the version-flexible methods instead of the
version specific methods.
If you want to limit the supported protocols for the version
flexible methods you can use SSL_CTX_set_min_proto_version(3),
SSL_set_min_proto_version(3), SSL_CTX_set_max_proto_version(3)
and SSL_set_max_proto_version(3) functions. Using these functions it
is possible to choose e.g. TLS_server_method() and be able to
negotiate with all possible clients, but to only allow newer protocols like
TLS 1.0, TLS 1.1, TLS 1.2 or TLS 1.3.
The list of protocols available can also be limited using the
SSL_OP_NO_SSLv3, SSL_OP_NO_TLSv1, SSL_OP_NO_TLSv1_1,
SSL_OP_NO_TLSv1_3, SSL_OP_NO_TLSv1_2 and
SSL_OP_NO_TLSv1_3 options of the SSL_CTX_set_options(3) or
SSL_set_options(3) functions, but this approach is not recommended.
Clients should avoid creating "holes" in the set of protocols they
support. When disabling a protocol, make sure that you also disable either
all previous or all subsequent protocol versions. In clients, when a
protocol version is disabled without disabling all previous protocol
versions, the effect is to also disable all subsequent protocol
versions.
The SSLv3 protocol is deprecated and should generally not be used.
Applications should typically use SSL_CTX_set_min_proto_version(3) to
set the minimum protocol to at least TLS1_VERSION.
The following return values can occur:
- NULL
- The creation of a new SSL_CTX object failed. Check the error stack to find
out the reason.
- Pointer to an SSL_CTX object
- The return value points to an allocated SSL_CTX object.
SSL_CTX_up_ref() returns 1 for success and 0 for
failure.
SSL_CTX_set_options(3), SSL_CTX_free(3), SSL_accept(3),
SSL_CTX_set_min_proto_version(3), ssl(7),
SSL_set_connect_state(3)
Support for SSLv2 and the corresponding SSLv2_method(),
SSLv2_server_method() and SSLv2_client_method() functions where
removed in OpenSSL 1.1.0.
SSLv23_method(), SSLv23_server_method() and
SSLv23_client_method() were deprecated and the preferred
TLS_method(), TLS_server_method() and
TLS_client_method() functions were added in OpenSSL 1.1.0.
All version-specific methods were deprecated in OpenSSL 1.1.0.
Copyright 2000-2019 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
<https://www.openssl.org/source/license.html>.