=pod

=head1 NAME

SSL_CTX_use_serverinfo_ex,
SSL_CTX_use_serverinfo,
SSL_CTX_use_serverinfo_file
- use serverinfo extension

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 int SSL_CTX_use_serverinfo_ex(SSL_CTX *ctx, unsigned int version,
                               const unsigned char *serverinfo,
                               size_t serverinfo_length);

 int SSL_CTX_use_serverinfo(SSL_CTX *ctx, const unsigned char *serverinfo,
                            size_t serverinfo_length);

 int SSL_CTX_use_serverinfo_file(SSL_CTX *ctx, const char *file);

=head1 DESCRIPTION

These functions load "serverinfo" TLS extensions into the SSL_CTX. A
"serverinfo" extension is returned in response to an empty ClientHello
Extension.

SSL_CTX_use_serverinfo_ex() loads one or more serverinfo extensions from
a byte array into B<ctx>. The B<version> parameter specifies the format of the
byte array provided in B<*serverinfo> which is of length B<serverinfo_length>.

If B<version> is B<SSL_SERVERINFOV2> then the extensions in the array must
consist of a 4-byte context, a 2-byte Extension Type, a 2-byte length, and then
length bytes of extension_data. The context and type values have the same
meaning as for L<SSL_CTX_add_custom_ext(3)>. If serverinfo is being loaded for
extensions to be added to a Certificate message, then the extension will only
be added for the first certificate in the message (which is always the
end-entity certificate).

If B<version> is B<SSL_SERVERINFOV1> then the extensions in the array must
consist of a 2-byte Extension Type, a 2-byte length, and then length bytes of
extension_data. The type value has the same meaning as for
L<SSL_CTX_add_custom_ext(3)>. The following default context value will be used
in this case:

 SSL_EXT_TLS1_2_AND_BELOW_ONLY | SSL_EXT_CLIENT_HELLO
 | SSL_EXT_TLS1_2_SERVER_HELLO | SSL_EXT_IGNORE_ON_RESUMPTION

SSL_CTX_use_serverinfo() does the same thing as SSL_CTX_use_serverinfo_ex()
except that there is no B<version> parameter so a default version of
SSL_SERVERINFOV1 is used instead.

SSL_CTX_use_serverinfo_file() loads one or more serverinfo extensions from
B<file> into B<ctx>.  The extensions must be in PEM format.  Each extension
must be in a format as described above for SSL_CTX_use_serverinfo_ex().  Each
PEM extension name must begin with the phrase "BEGIN SERVERINFOV2 FOR " for
SSL_SERVERINFOV2 data or "BEGIN SERVERINFO FOR " for SSL_SERVERINFOV1 data.

If more than one certificate (RSA/DSA) is installed using
SSL_CTX_use_certificate(), the serverinfo extension will be loaded into the
last certificate installed.  If e.g. the last item was a RSA certificate, the
loaded serverinfo extension data will be loaded for that certificate.  To
use the serverinfo extension for multiple certificates,
SSL_CTX_use_serverinfo() needs to be called multiple times, once B<after>
each time a certificate is loaded via a call to SSL_CTX_use_certificate().

=head1 RETURN VALUES

On success, the functions return 1.
On failure, the functions return 0.  Check out the error stack to find out
the reason.

=head1 COPYRIGHT

Copyright 2013-2017 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
L<https://www.openssl.org/source/license.html>.

=cut