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✏️ Editing: TLS_method.3

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.\" ========================================================================
.\"
.IX Title "SSL_CTX_NEW 3"
.TH SSL_CTX_NEW 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
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
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBSSL_CTX_new()\fR creates a new \fB\s-1SSL_CTX\s0\fR object as framework to
establish \s-1TLS/SSL\s0 or \s-1DTLS\s0 enabled connections. An \fB\s-1SSL_CTX\s0\fR object is
reference counted. Creating an \fB\s-1SSL_CTX\s0\fR 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
\&\fB\s-1SSL_CTX\s0\fR object are freed. \fBSSL_CTX_up_ref()\fR increments the reference count for
an existing \fB\s-1SSL_CTX\s0\fR structure.
.SH "NOTES"
.IX Header "NOTES"
The \s-1SSL_CTX\s0 object uses \fBmethod\fR as connection method.
The methods exist in a generic type (for client and server use), a server only
type, and a client only type.
\&\fBmethod\fR can be of the following types:
.IP "\fBTLS_method()\fR, \fBTLS_server_method()\fR, \fBTLS_client_method()\fR" 4
.IX Item "TLS_method(), TLS_server_method(), TLS_client_method()"
These are the general-purpose \fIversion-flexible\fR \s-1SSL/TLS\s0 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.
.IP "\fBSSLv23_method()\fR, \fBSSLv23_server_method()\fR, \fBSSLv23_client_method()\fR" 4
.IX Item "SSLv23_method(), SSLv23_server_method(), SSLv23_client_method()"
These functions do not exist anymore, they have been renamed to
\&\fBTLS_method()\fR, \fBTLS_server_method()\fR and \fBTLS_client_method()\fR 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.
.IP "\fBTLSv1_2_method()\fR, \fBTLSv1_2_server_method()\fR, \fBTLSv1_2_client_method()\fR" 4
.IX Item "TLSv1_2_method(), TLSv1_2_server_method(), TLSv1_2_client_method()"
A \s-1TLS/SSL\s0 connection established with these methods will only understand the
TLSv1.2 protocol. These methods are deprecated.
.IP "\fBTLSv1_1_method()\fR, \fBTLSv1_1_server_method()\fR, \fBTLSv1_1_client_method()\fR" 4
.IX Item "TLSv1_1_method(), TLSv1_1_server_method(), TLSv1_1_client_method()"
A \s-1TLS/SSL\s0 connection established with these methods will only understand the
TLSv1.1 protocol.  These methods are deprecated.
.IP "\fBTLSv1_method()\fR, \fBTLSv1_server_method()\fR, \fBTLSv1_client_method()\fR" 4
.IX Item "TLSv1_method(), TLSv1_server_method(), TLSv1_client_method()"
A \s-1TLS/SSL\s0 connection established with these methods will only understand the
TLSv1 protocol. These methods are deprecated.
.IP "\fBSSLv3_method()\fR, \fBSSLv3_server_method()\fR, \fBSSLv3_client_method()\fR" 4
.IX Item "SSLv3_method(), SSLv3_server_method(), SSLv3_client_method()"
A \s-1TLS/SSL\s0 connection established with these methods will only understand the
SSLv3 protocol.
The SSLv3 protocol is deprecated and should not be used.
.IP "\fBDTLS_method()\fR, \fBDTLS_server_method()\fR, \fBDTLS_client_method()\fR" 4
.IX Item "DTLS_method(), DTLS_server_method(), DTLS_client_method()"
These are the version-flexible \s-1DTLS\s0 methods.
Currently supported protocols are \s-1DTLS 1.0\s0 and \s-1DTLS 1.2.\s0
.IP "\fBDTLSv1_2_method()\fR, \fBDTLSv1_2_server_method()\fR, \fBDTLSv1_2_client_method()\fR" 4
.IX Item "DTLSv1_2_method(), DTLSv1_2_server_method(), DTLSv1_2_client_method()"
These are the version-specific methods for DTLSv1.2.
These methods are deprecated.
.IP "\fBDTLSv1_method()\fR, \fBDTLSv1_server_method()\fR, \fBDTLSv1_client_method()\fR" 4
.IX Item "DTLSv1_method(), DTLSv1_server_method(), DTLSv1_client_method()"
These are the version-specific methods for DTLSv1.
These methods are deprecated.
.PP
\&\fBSSL_CTX_new()\fR initializes the list of ciphers, the session cache setting, the
callbacks, the keys and certificates and the options to their default values.
.PP
\&\fBTLS_method()\fR, \fBTLS_server_method()\fR, \fBTLS_client_method()\fR, \fBDTLS_method()\fR,
\&\fBDTLS_server_method()\fR and \fBDTLS_client_method()\fR are the \fIversion-flexible\fR
methods.
All other methods only support one specific protocol version.
Use the \fIversion-flexible\fR methods instead of the version specific methods.
.PP
If you want to limit the supported protocols for the version flexible
methods you can use \fBSSL_CTX_set_min_proto_version\fR\|(3),
\&\fBSSL_set_min_proto_version\fR\|(3), \fBSSL_CTX_set_max_proto_version\fR\|(3) and
\&\fBSSL_set_max_proto_version\fR\|(3) functions.
Using these functions it is possible to choose e.g. \fBTLS_server_method()\fR
and be able to negotiate with all possible clients, but to only
allow newer protocols like \s-1TLS 1.0, TLS 1.1, TLS 1.2\s0 or \s-1TLS 1.3.\s0
.PP
The list of protocols available can also be limited using the
\&\fBSSL_OP_NO_SSLv3\fR, \fBSSL_OP_NO_TLSv1\fR, \fBSSL_OP_NO_TLSv1_1\fR,
\&\fBSSL_OP_NO_TLSv1_3\fR, \fBSSL_OP_NO_TLSv1_2\fR and \fBSSL_OP_NO_TLSv1_3\fR
options of the
\&\fBSSL_CTX_set_options\fR\|(3) or \fBSSL_set_options\fR\|(3) functions, but this approach
is not recommended. Clients should avoid creating \*(L"holes\*(R" 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 \fIall\fR
previous protocol versions, the effect is to also disable all subsequent
protocol versions.
.PP
The SSLv3 protocol is deprecated and should generally not be used.
Applications should typically use \fBSSL_CTX_set_min_proto_version\fR\|(3) to set
the minimum protocol to at least \fB\s-1TLS1_VERSION\s0\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
The following return values can occur:
.IP "\s-1NULL\s0" 4
.IX Item "NULL"
The creation of a new \s-1SSL_CTX\s0 object failed. Check the error stack to find out
the reason.
.IP "Pointer to an \s-1SSL_CTX\s0 object" 4
.IX Item "Pointer to an SSL_CTX object"
The return value points to an allocated \s-1SSL_CTX\s0 object.
.Sp
\&\fBSSL_CTX_up_ref()\fR returns 1 for success and 0 for failure.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBSSL_CTX_set_options\fR\|(3), \fBSSL_CTX_free\fR\|(3), \fBSSL_accept\fR\|(3),
\&\fBSSL_CTX_set_min_proto_version\fR\|(3), \fBssl\fR\|(7), \fBSSL_set_connect_state\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
Support for SSLv2 and the corresponding \fBSSLv2_method()\fR,
\&\fBSSLv2_server_method()\fR and \fBSSLv2_client_method()\fR functions where
removed in OpenSSL 1.1.0.
.PP
\&\fBSSLv23_method()\fR, \fBSSLv23_server_method()\fR and \fBSSLv23_client_method()\fR
were deprecated and the preferred \fBTLS_method()\fR, \fBTLS_server_method()\fR
and \fBTLS_client_method()\fR functions were added in OpenSSL 1.1.0.
.PP
All version-specific methods were deprecated in OpenSSL 1.1.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.

MR SKB