[thirdparty/openssl.git] / doc / man3 / SSL_extension_supported.pod

=pod

=head1 NAME

SSL_extension_supported,
SSL_CTX_add_custom_ext,
SSL_CTX_add_client_custom_ext, SSL_CTX_add_server_custom_ext,
custom_ext_add_cb, custom_ext_free_cb, custom_ext_parse_cb
- custom TLS extension handling

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 typedef int (*SSL_custom_ext_add_cb_ex) (SSL *s, unsigned int ext_type,
                                          unsigned int context,
                                          const unsigned char **out,
                                          size_t *outlen, X509 *x,
                                          size_t chainidx, int *al,
                                          void *add_arg);

 typedef void (*SSL_custom_ext_free_cb_ex) (SSL *s, unsigned int ext_type,
                                            unsigned int context,
                                            const unsigned char *out,
                                            void *add_arg);

 typedef int (*SSL_custom_ext_parse_cb_ex) (SSL *s, unsigned int ext_type,
                                            unsigned int context,
                                            const unsigned char *in,
                                            size_t inlen, X509 *x,
                                            size_t chainidx, int *al,
                                            void *parse_arg);

 int SSL_CTX_add_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
                            unsigned int context,
                            SSL_custom_ext_add_cb_ex add_cb,
                            SSL_custom_ext_free_cb_ex free_cb,
                            void *add_arg,
                            SSL_custom_ext_parse_cb_ex parse_cb,
                            void *parse_arg);

 typedef int (*custom_ext_add_cb)(SSL *s, unsigned int ext_type,
                                  const unsigned char **out,
                                  size_t *outlen, int *al,
                                  void *add_arg);

 typedef void (*custom_ext_free_cb)(SSL *s, unsigned int ext_type,
                                    const unsigned char *out,
                                    void *add_arg);

 typedef int (*custom_ext_parse_cb)(SSL *s, unsigned int ext_type,
                                    const unsigned char *in,
                                    size_t inlen, int *al,
                                    void *parse_arg);

 int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
                                   custom_ext_add_cb add_cb,
                                   custom_ext_free_cb free_cb, void *add_arg,
                                   custom_ext_parse_cb parse_cb,
                                   void *parse_arg);

 int SSL_CTX_add_server_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
                                   custom_ext_add_cb add_cb,
                                   custom_ext_free_cb free_cb, void *add_arg,
                                   custom_ext_parse_cb parse_cb,
                                   void *parse_arg);

 int SSL_extension_supported(unsigned int ext_type);

=head1 DESCRIPTION

SSL_CTX_add_custom_ext() adds a custom extension for a TLS/DTLS client or server
for all supported protocol versions with extension type B<ext_type> and
callbacks B<add_cb>, B<free_cb> and B<parse_cb> (see the
L</EXTENSION CALLBACKS> section below). The B<context> value determines
which messages and under what conditions the extension will be added/parsed (see
the L</EXTENSION CONTEXTS> section below).

SSL_CTX_add_client_custom_ext() adds a custom extension for a TLS/DTLS client
with extension type B<ext_type> and callbacks B<add_cb>, B<free_cb> and
B<parse_cb>. This function is similar to SSL_CTX_add_custom_ext() except it only
applies to clients, uses the older style of callbacks, and implicitly sets the
B<context> value to:

 SSL_EXT_TLS1_2_AND_BELOW_ONLY | SSL_EXT_CLIENT_HELLO
 | SSL_EXT_TLS1_2_SERVER_HELLO | SSL_EXT_IGNORE_ON_RESUMPTION

SSL_CTX_add_server_custom_ext() adds a custom extension for a TLS/DTLS server
with extension type B<ext_type> and callbacks B<add_cb>, B<free_cb> and
B<parse_cb>. This function is similar to SSL_CTX_add_custom_ext() except it
only applies to servers, uses the older style of callbacks, and implicitly sets
the B<context> value to the same as for SSL_CTX_add_client_custom_ext() above.

The B<ext_type> parameter corresponds to the B<extension_type> field of
RFC5246 et al. It is B<not> a NID. In all cases the extension type must not be
handled by OpenSSL internally or an error occurs.

SSL_extension_supported() returns 1 if the extension B<ext_type> is handled
internally by OpenSSL and 0 otherwise.

=head1 EXTENSION CALLBACKS

The callback B<add_cb> is called to send custom extension data to be
included in various TLS messages. The B<ext_type> parameter is set to the
extension type which will be added and B<add_arg> to the value set when the
extension handler was added. When using the new style callbacks the B<context>
parameter will indicate which message is currently being constructed e.g. for
the ClientHello it will be set to B<SSL_EXT_CLIENT_HELLO>.

If the application wishes to include the extension B<ext_type> it should
set B<*out> to the extension data, set B<*outlen> to the length of the
extension data and return 1.

If the B<add_cb> does not wish to include the extension it must return 0.

If B<add_cb> returns -1 a fatal handshake error occurs using the TLS
alert value specified in B<*al>.

When constructing the ClientHello, if B<add_cb> is set to NULL a zero length
extension is added for B<ext_type>. For all other messages if B<add_cb> is set
to NULL then no extension is added.

When constructing a Certificate message the callback will be called for each
certificate in the message. The B<x> parameter will indicate the
current certificate and the B<chainidx> parameter will indicate the position
of the certificate in the message. The first certificate is always the end
entity certificate and has a B<chainidx> value of 0. The certificates are in the
order that they were received in the Certificate message.

For all messages except the ServerHello and EncryptedExtensions every
registered B<add_cb> is always called to see if the application wishes to add an
extension (as long as all requirements of the specified B<context> are met).

For the ServerHello and EncryptedExtension messages every registered B<add_cb>
is called once if and only if the requirements of the specified B<context> are
met and the corresponding extension was received in the ClientHello. That is, if
no corresponding extension was received in the ClientHello then B<add_cb> will
not be called.

If an extension is added (that is B<add_cb> returns 1) B<free_cb> is called
(if it is set) with the value of B<out> set by the add callback. It can be
used to free up any dynamic extension data set by B<add_cb>. Since B<out> is
constant (to permit use of constant data in B<add_cb>) applications may need to
cast away const to free the data.

The callback B<parse_cb> receives data for TLS extensions. The callback is only
called if the extension is present and relevant for the context (see
L</EXTENSION CONTEXTS> below).

The extension data consists of B<inlen> bytes in the buffer B<in> for the
extension B<ext_type>.

If the message being parsed is a TLSv1.3 compatible Certificate message then
B<parse_cb> will be called for each certificate contained within the message.
The B<x> parameter will indicate the current certificate and the B<chainidx>
parameter will indicate the position of the certificate in the message. The
first certificate is always the end entity certificate and has a B<chainidx>
value of 0.

If the B<parse_cb> considers the extension data acceptable it must return
1. If it returns 0 or a negative value a fatal handshake error occurs
using the TLS alert value specified in B<*al>.

The buffer B<in> is a temporary internal buffer which will not be valid after
the callback returns.

=head1 EXTENSION CONTEXTS

An extension context defines which messages and under which conditions an
extension should be added or expected. The context is built up by performing
a bitwise OR of multiple pre-defined values together. The valid context values
are:

=over 4

=item SSL_EXT_TLS_ONLY

The extension is only allowed in TLS

=item SSL_EXT_DTLS_ONLY

The extension is only allowed in DTLS

=item SSL_EXT_TLS_IMPLEMENTATION_ONLY

The extension is allowed in DTLS, but there is only a TLS implementation
available (so it is ignored in DTLS).

=item SSL_EXT_SSL3_ALLOWED

Extensions are not typically defined for SSLv3. Setting this value will allow
the extension in SSLv3. Applications will not typically need to use this.

=item SSL_EXT_TLS1_2_AND_BELOW_ONLY

The extension is only defined for TLSv1.2/DTLSv1.2 and below. Servers will
ignore this extension if it is present in the ClientHello and TLSv1.3 is
negotiated.

=item SSL_EXT_TLS1_3_ONLY

The extension is only defined for TLS1.3 and above. Servers will ignore this
extension if it is present in the ClientHello and TLSv1.2 or below is
negotiated.

=item SSL_EXT_IGNORE_ON_RESUMPTION

The extension will be ignored during parsing if a previous session is being
successfully resumed.

=item SSL_EXT_CLIENT_HELLO

The extension may be present in the ClientHello message.

=item SSL_EXT_TLS1_2_SERVER_HELLO

The extension may be present in a TLSv1.2 or below compatible ServerHello
message.

=item SSL_EXT_TLS1_3_SERVER_HELLO

The extension may be present in a TLSv1.3 compatible ServerHello message.

=item SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS

The extension may be present in an EncryptedExtensions message.

=item SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST

The extension may be present in a HelloRetryRequest message.

=item SSL_EXT_TLS1_3_CERTIFICATE

The extension may be present in a TLSv1.3 compatible Certificate message.

=item SSL_EXT_TLS1_3_NEW_SESSION_TICKET

The extension may be present in a TLSv1.3 compatible NewSessionTicket message.

=item SSL_EXT_TLS1_3_CERTIFICATE_REQUEST

The extension may be present in a TLSv1.3 compatible CertificateRequest message.

=back

The context must include at least one message value (otherwise the extension
will never be used).

=head1 NOTES

The B<add_arg> and B<parse_arg> parameters can be set to arbitrary values
which will be passed to the corresponding callbacks. They can, for example,
be used to store the extension data received in a convenient structure or
pass the extension data to be added or freed when adding extensions.

If the same custom extension type is received multiple times a fatal
B<decode_error> alert is sent and the handshake aborts. If a custom extension
is received in a ServerHello/EncryptedExtensions message which was not sent in
the ClientHello a fatal B<unsupported_extension> alert is sent and the
handshake is aborted. The ServerHello/EncryptedExtensions B<add_cb> callback is
only called if the corresponding extension was received in the ClientHello. This
is compliant with the TLS specifications. This behaviour ensures that each
callback is called at most once and that an application can never send
unsolicited extensions.

=head1 RETURN VALUES

SSL_CTX_add_custom_ext(), SSL_CTX_add_client_custom_ext() and
SSL_CTX_add_server_custom_ext() return 1 for success and 0 for failure. A
failure can occur if an attempt is made to add the same B<ext_type> more than
once, if an attempt is made to use an extension type handled internally by
OpenSSL or if an internal error occurs (for example a memory allocation
failure).

SSL_extension_supported() returns 1 if the extension B<ext_type> is handled
internally by OpenSSL and 0 otherwise.

=head1 HISTORY

The SSL_CTX_add_custom_ext() function was added in OpenSSL 1.1.1.

=head1 COPYRIGHT

Copyright 2014-2017 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
Commit	Line	Data
f3f56c2a DSH	1	=pod
	2
	3	=head1 NAME
	4
c952780c	5	SSL_extension_supported,
314aec07	6	SSL_CTX_add_custom_ext,
121677b4 RS	7	SSL_CTX_add_client_custom_ext, SSL_CTX_add_server_custom_ext,
121677b4 RS	8	custom_ext_add_cb, custom_ext_free_cb, custom_ext_parse_cb
c952780c	9	- custom TLS extension handling
f3f56c2a DSH	10
	11	=head1 SYNOPSIS
	12
	13	#include <openssl/ssl.h>
	14
cd17bb19 MC	15	typedef int (SSL_custom_ext_add_cb_ex) (SSL s, unsigned int ext_type,
	16	unsigned int context,
	17	const unsigned char **out,
	18	size_t outlen, X509 x,
	19	size_t chainidx, int *al,
	20	void *add_arg);
	21
	22	typedef void (SSL_custom_ext_free_cb_ex) (SSL s, unsigned int ext_type,
	23	unsigned int context,
	24	const unsigned char *out,
	25	void *add_arg);
	26
	27	typedef int (SSL_custom_ext_parse_cb_ex) (SSL s, unsigned int ext_type,
	28	unsigned int context,
	29	const unsigned char *in,
	30	size_t inlen, X509 *x,
	31	size_t chainidx, int *al,
	32	void *parse_arg);
314aec07 MC	33
	34	int SSL_CTX_add_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
	35	unsigned int context,
cd17bb19 MC	36	SSL_custom_ext_add_cb_ex add_cb,
cd17bb19 MC	37	SSL_custom_ext_free_cb_ex free_cb,
314aec07	38	void *add_arg,
cd17bb19 MC	39	SSL_custom_ext_parse_cb_ex parse_cb,
cd17bb19 MC	40	void *parse_arg);
f3f56c2a DSH	41
f3f56c2a DSH	42	typedef int (custom_ext_add_cb)(SSL s, unsigned int ext_type,
1bc74519 RS	43	const unsigned char **out,
	44	size_t outlen, int al,
	45	void *add_arg);
f3f56c2a DSH	46
f3f56c2a DSH	47	typedef void (custom_ext_free_cb)(SSL s, unsigned int ext_type,
1bc74519 RS	48	const unsigned char *out,
1bc74519 RS	49	void *add_arg);
f3f56c2a DSH	50
f3f56c2a DSH	51	typedef int (custom_ext_parse_cb)(SSL s, unsigned int ext_type,
1bc74519 RS	52	const unsigned char *in,
	53	size_t inlen, int *al,
	54	void *parse_arg);
f3f56c2a	55
314aec07 MC	56	int SSL_CTX_add_client_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
	57	custom_ext_add_cb add_cb,
	58	custom_ext_free_cb free_cb, void *add_arg,
	59	custom_ext_parse_cb parse_cb,
	60	void *parse_arg);
f3f56c2a	61
314aec07 MC	62	int SSL_CTX_add_server_custom_ext(SSL_CTX *ctx, unsigned int ext_type,
	63	custom_ext_add_cb add_cb,
	64	custom_ext_free_cb free_cb, void *add_arg,
	65	custom_ext_parse_cb parse_cb,
	66	void *parse_arg);
f3f56c2a	67
314aec07	68	int SSL_extension_supported(unsigned int ext_type);
f3f56c2a	69
314aec07	70	=head1 DESCRIPTION
f3f56c2a	71
64350ab5	72	SSL_CTX_add_custom_ext() adds a custom extension for a TLS/DTLS client or server
314aec07 MC	73	for all supported protocol versions with extension type B<ext_type> and
	74	callbacks B<add_cb>, B<free_cb> and B<parse_cb> (see the
	75	L</EXTENSION CALLBACKS> section below). The B<context> value determines
	76	which messages and under what conditions the extension will be added/parsed (see
	77	the L</EXTENSION CONTEXTS> section below).
	78
64350ab5 MC	79	SSL_CTX_add_client_custom_ext() adds a custom extension for a TLS/DTLS client
	80	with extension type B<ext_type> and callbacks B<add_cb>, B<free_cb> and
	81	B<parse_cb>. This function is similar to SSL_CTX_add_custom_ext() except it only
	82	applies to clients, uses the older style of callbacks, and implicitly sets the
314aec07 MC	83	B<context> value to:
	84
	85	SSL_EXT_TLS1_2_AND_BELOW_ONLY \| SSL_EXT_CLIENT_HELLO
	86	\| SSL_EXT_TLS1_2_SERVER_HELLO \| SSL_EXT_IGNORE_ON_RESUMPTION
	87
64350ab5 MC	88	SSL_CTX_add_server_custom_ext() adds a custom extension for a TLS/DTLS server
64350ab5 MC	89	with extension type B<ext_type> and callbacks B<add_cb>, B<free_cb> and
314aec07 MC	90	B<parse_cb>. This function is similar to SSL_CTX_add_custom_ext() except it
	91	only applies to servers, uses the older style of callbacks, and implicitly sets
	92	the B<context> value to the same as for SSL_CTX_add_client_custom_ext() above.
	93
64350ab5 MC	94	The B<ext_type> parameter corresponds to the B<extension_type> field of
	95	RFC5246 et al. It is B<not> a NID. In all cases the extension type must not be
	96	handled by OpenSSL internally or an error occurs.
f3f56c2a DSH	97
	98	SSL_extension_supported() returns 1 if the extension B<ext_type> is handled
	99	internally by OpenSSL and 0 otherwise.
	100
	101	=head1 EXTENSION CALLBACKS
	102
1bc74519	103	The callback B<add_cb> is called to send custom extension data to be
314aec07 MC	104	included in various TLS messages. The B<ext_type> parameter is set to the
	105	extension type which will be added and B<add_arg> to the value set when the
	106	extension handler was added. When using the new style callbacks the B<context>
	107	parameter will indicate which message is currently being constructed e.g. for
	108	the ClientHello it will be set to B<SSL_EXT_CLIENT_HELLO>.
f3f56c2a DSH	109
	110	If the application wishes to include the extension B<ext_type> it should
	111	set B<out> to the extension data, set B<outlen> to the length of the
	112	extension data and return 1.
	113
	114	If the B<add_cb> does not wish to include the extension it must return 0.
	115
	116	If B<add_cb> returns -1 a fatal handshake error occurs using the TLS
	117	alert value specified in B<*al>.
	118
64350ab5	119	When constructing the ClientHello, if B<add_cb> is set to NULL a zero length
314aec07 MC	120	extension is added for B<ext_type>. For all other messages if B<add_cb> is set
	121	to NULL then no extension is added.
	122
	123	When constructing a Certificate message the callback will be called for each
	124	certificate in the message. The B<x> parameter will indicate the
	125	current certificate and the B<chainidx> parameter will indicate the position
	126	of the certificate in the message. The first certificate is always the end
64350ab5 MC	127	entity certificate and has a B<chainidx> value of 0. The certificates are in the
64350ab5 MC	128	order that they were received in the Certificate message.
f3f56c2a	129
314aec07 MC	130	For all messages except the ServerHello and EncryptedExtensions every
	131	registered B<add_cb> is always called to see if the application wishes to add an
	132	extension (as long as all requirements of the specified B<context> are met).
f3f56c2a	133
314aec07 MC	134	For the ServerHello and EncryptedExtension messages every registered B<add_cb>
	135	is called once if and only if the requirements of the specified B<context> are
	136	met and the corresponding extension was received in the ClientHello. That is, if
	137	no corresponding extension was received in the ClientHello then B<add_cb> will
	138	not be called.
f3f56c2a DSH	139
	140	If an extension is added (that is B<add_cb> returns 1) B<free_cb> is called
	141	(if it is set) with the value of B<out> set by the add callback. It can be
	142	used to free up any dynamic extension data set by B<add_cb>. Since B<out> is
	143	constant (to permit use of constant data in B<add_cb>) applications may need to
	144	cast away const to free the data.
	145
314aec07 MC	146	The callback B<parse_cb> receives data for TLS extensions. The callback is only
	147	called if the extension is present and relevant for the context (see
	148	L</EXTENSION CONTEXTS> below).
f3f56c2a DSH	149
f3f56c2a DSH	150	The extension data consists of B<inlen> bytes in the buffer B<in> for the
314aec07 MC	151	extension B<ext_type>.
	152
	153	If the message being parsed is a TLSv1.3 compatible Certificate message then
	154	B<parse_cb> will be called for each certificate contained within the message.
	155	The B<x> parameter will indicate the current certificate and the B<chainidx>
	156	parameter will indicate the position of the certificate in the message. The
	157	first certificate is always the end entity certificate and has a B<chainidx>
	158	value of 0.
f3f56c2a DSH	159
	160	If the B<parse_cb> considers the extension data acceptable it must return
	161	1. If it returns 0 or a negative value a fatal handshake error occurs
	162	using the TLS alert value specified in B<*al>.
	163
	164	The buffer B<in> is a temporary internal buffer which will not be valid after
	165	the callback returns.
	166
314aec07 MC	167	=head1 EXTENSION CONTEXTS
	168
	169	An extension context defines which messages and under which conditions an
	170	extension should be added or expected. The context is built up by performing
	171	a bitwise OR of multiple pre-defined values together. The valid context values
	172	are:
	173
	174	=over 4
	175
	176	=item SSL_EXT_TLS_ONLY
	177
	178	The extension is only allowed in TLS
	179
	180	=item SSL_EXT_DTLS_ONLY
	181
	182	The extension is only allowed in DTLS
	183
	184	=item SSL_EXT_TLS_IMPLEMENTATION_ONLY
	185
	186	The extension is allowed in DTLS, but there is only a TLS implementation
	187	available (so it is ignored in DTLS).
	188
	189	=item SSL_EXT_SSL3_ALLOWED
	190
	191	Extensions are not typically defined for SSLv3. Setting this value will allow
	192	the extension in SSLv3. Applications will not typically need to use this.
	193
	194	=item SSL_EXT_TLS1_2_AND_BELOW_ONLY
	195
64350ab5 MC	196	The extension is only defined for TLSv1.2/DTLSv1.2 and below. Servers will
	197	ignore this extension if it is present in the ClientHello and TLSv1.3 is
	198	negotiated.
314aec07 MC	199
	200	=item SSL_EXT_TLS1_3_ONLY
	201
	202	The extension is only defined for TLS1.3 and above. Servers will ignore this
	203	extension if it is present in the ClientHello and TLSv1.2 or below is
	204	negotiated.
	205
	206	=item SSL_EXT_IGNORE_ON_RESUMPTION
	207
	208	The extension will be ignored during parsing if a previous session is being
	209	successfully resumed.
	210
	211	=item SSL_EXT_CLIENT_HELLO
	212
	213	The extension may be present in the ClientHello message.
	214
	215	=item SSL_EXT_TLS1_2_SERVER_HELLO
	216
	217	The extension may be present in a TLSv1.2 or below compatible ServerHello
	218	message.
	219
	220	=item SSL_EXT_TLS1_3_SERVER_HELLO
	221
	222	The extension may be present in a TLSv1.3 compatible ServerHello message.
	223
	224	=item SSL_EXT_TLS1_3_ENCRYPTED_EXTENSIONS
	225
	226	The extension may be present in an EncryptedExtensions message.
	227
	228	=item SSL_EXT_TLS1_3_HELLO_RETRY_REQUEST
	229
	230	The extension may be present in a HelloRetryRequest message.
	231
	232	=item SSL_EXT_TLS1_3_CERTIFICATE
	233
	234	The extension may be present in a TLSv1.3 compatible Certificate message.
	235
	236	=item SSL_EXT_TLS1_3_NEW_SESSION_TICKET
	237
	238	The extension may be present in a TLSv1.3 compatible NewSessionTicket message.
	239
	240	=item SSL_EXT_TLS1_3_CERTIFICATE_REQUEST
	241
	242	The extension may be present in a TLSv1.3 compatible CertificateRequest message.
	243
	244	=back
	245
	246	The context must include at least one message value (otherwise the extension
	247	will never be used).
	248
f3f56c2a DSH	249	=head1 NOTES
	250
	251	The B<add_arg> and B<parse_arg> parameters can be set to arbitrary values
	252	which will be passed to the corresponding callbacks. They can, for example,
	253	be used to store the extension data received in a convenient structure or
	254	pass the extension data to be added or freed when adding extensions.
	255
f3f56c2a DSH	256	If the same custom extension type is received multiple times a fatal
f3f56c2a DSH	257	B<decode_error> alert is sent and the handshake aborts. If a custom extension
314aec07 MC	258	is received in a ServerHello/EncryptedExtensions message which was not sent in
	259	the ClientHello a fatal B<unsupported_extension> alert is sent and the
	260	handshake is aborted. The ServerHello/EncryptedExtensions B<add_cb> callback is
	261	only called if the corresponding extension was received in the ClientHello. This
	262	is compliant with the TLS specifications. This behaviour ensures that each
	263	callback is called at most once and that an application can never send
	264	unsolicited extensions.
f3f56c2a DSH	265
	266	=head1 RETURN VALUES
	267
314aec07 MC	268	SSL_CTX_add_custom_ext(), SSL_CTX_add_client_custom_ext() and
	269	SSL_CTX_add_server_custom_ext() return 1 for success and 0 for failure. A
	270	failure can occur if an attempt is made to add the same B<ext_type> more than
	271	once, if an attempt is made to use an extension type handled internally by
	272	OpenSSL or if an internal error occurs (for example a memory allocation
	273	failure).
f3f56c2a DSH	274
	275	SSL_extension_supported() returns 1 if the extension B<ext_type> is handled
	276	internally by OpenSSL and 0 otherwise.
	277
314aec07 MC	278	=head1 HISTORY
314aec07 MC	279
fc5ecadd	280	The SSL_CTX_add_custom_ext() function was added in OpenSSL 1.1.1.
314aec07	281
e2f92610 RS	282	=head1 COPYRIGHT
e2f92610 RS	283
314aec07	284	Copyright 2014-2017 The OpenSSL Project Authors. All Rights Reserved.
e2f92610	285
4746f25a	286	Licensed under the Apache License 2.0 (the "License"). You may not use
e2f92610 RS	287	this file except in compliance with the License. You can obtain a copy
	288	in the file LICENSE in the source distribution or at
	289	L<https://www.openssl.org/source/license.html>.
	290
	291	=cut