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.\" $OpenBSD: SSL_CTX_set_tlsext_servername_callback.3,v 1.1 2017/04/10 13:05:06 schwarze Exp $
.\" OpenSSL 8c55c461 Mar 29 08:34:37 2017 +1000
.\"
.\" This file was written by Jon Spillett <jon.spillett@oracle.com>
.\" Copyright (c) 2000 The OpenSSL Project. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in
.\" the documentation and/or other materials provided with the
.\" distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\" software must display the following acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\" endorse or promote products derived from this software without
.\" prior written permission. For written permission, please contact
.\" openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\" nor may "OpenSSL" appear in their names without prior written
.\" permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\" acknowledgment:
.\" "This product includes software developed by the OpenSSL Project
.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: April 10 2017 $
.Dt SSL_CTX_SET_TLSEXT_SERVERNAME_CALLBACK 3
.Os
.Sh NAME
.Nm SSL_CTX_set_tlsext_servername_callback ,
.Nm SSL_CTX_set_tlsext_servername_arg ,
.Nm SSL_get_servername_type ,
.Nm SSL_get_servername
.Nd handle server name indication (SNI)
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft long
.Fo SSL_CTX_set_tlsext_servername_callback
.Fa "SSL_CTX *ctx"
.Fa "int (*cb)(SSL_CTX *, int *, void *)"
.Fc
.Ft long
.Fo SSL_CTX_set_tlsext_servername_arg
.Fa "SSL_CTX *ctx"
.Fa "void *arg"
.Fc
.Ft const char *
.Fo SSL_get_servername
.Fa "const SSL *s"
.Fa "const int type"
.Fc
.Ft int
.Fo SSL_get_servername_type
.Fa "const SSL *s"
.Fc
.Sh DESCRIPTION
.Fn SSL_CTX_set_tlsext_servername_callback
sets the application callback
.Fa cb
used by a server to perform any actions or configuration required based
on the servername extension received in the incoming connection.
When
.Fa cb
is
.Dv NULL ,
SNI is not used.
The
.Fa arg
value is a pointer which is passed to the application callback.
.Pp
.Fn SSL_CTX_set_tlsext_servername_arg
sets a context-specific argument to be passed into the callback for
.Fa ctx .
.Pp
Both functions are implemented as macros.
.Pp
The ALPN and SNI callbacks are both executed during Client Hello
processing.
The servername callback is executed first, followed by the ALPN
callback.
.Sh RETURN VALUES
.Fn SSL_CTX_set_tlsext_servername_callback
and
.Fn SSL_CTX_set_tlsext_servername_arg
always return 1 indicating success.
.Pp
.Fn SSL_get_servername
returns a servername extension value of the specified type if provided
in the Client Hello, or
.Dv NULL
otherwise.
.Pp
.Fn SSL_get_servername_type
returns the servername type or -1 if no servername is present.
Currently the only supported type (defined in RFC 3546) is
.Dv TLSEXT_NAMETYPE_host_name .
.Sh SEE ALSO
.Xr SSL_CTX_callback_ctrl 3 ,
.Xr SSL_CTX_set_alpn_select_cb 3
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