.\"	$OpenBSD: SSL_set_tmp_ecdh.3,v 1.6 2021/11/30 15:58:08 jsing Exp $
.\"
.\" Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd $Mdocdate: November 30 2021 $
.Dt SSL_SET_TMP_ECDH 3
.Os
.Sh NAME
.Nm SSL_set_tmp_ecdh ,
.Nm SSL_CTX_set_tmp_ecdh ,
.Nm SSL_set_ecdh_auto ,
.Nm SSL_CTX_set_ecdh_auto ,
.Nm SSL_set_tmp_ecdh_callback ,
.Nm SSL_CTX_set_tmp_ecdh_callback
.Nd select a curve for ECDH ephemeral key exchange
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft long
.Fo SSL_set_tmp_ecdh
.Fa "SSL *ssl"
.Fa "EC_KEY *ecdh"
.Fc
.Ft long
.Fo SSL_CTX_set_tmp_ecdh
.Fa "SSL_CTX *ctx"
.Fa "EC_KEY *ecdh"
.Fc
.Ft long
.Fo SSL_set_ecdh_auto
.Fa "SSL *ssl"
.Fa "int state"
.Fc
.Ft long
.Fo SSL_CTX_set_ecdh_auto
.Fa "SSL_CTX *ctx"
.Fa "int state"
.Fc
.Ft void
.Fo SSL_set_tmp_ecdh_callback
.Fa "SSL *ssl"
.Fa "EC_KEY *(*ecdh)(SSL *ssl, int is_export, int keylength)"
.Fc
.Ft void
.Fo SSL_CTX_set_tmp_ecdh_callback
.Fa "SSL_CTX *ctx"
.Fa "EC_KEY *(*ecdh)(SSL *ssl, int is_export, int keylength)"
.Fc
.Sh DESCRIPTION
Automatic EC curve selection and generation is always enabled in
LibreSSL, and applications cannot manually provide EC keys for use
with ECDH key exchange.
.Pp
The only remaining effect of
.Fn SSL_set_tmp_ecdh
is that the curve of the given
.Fa ecdh
key becomes the only curve enabled for the
.Fa ssl
connection, so it is equivalent to calling
.Xr SSL_set1_groups_list 3
with the same single curve name.
.Pp
.Fn SSL_CTX_set_tmp_ecdh
has the same effect on all connections that will be created from
.Fa ctx
in the future.
.Pp
The functions
.Fn SSL_set_ecdh_auto ,
.Fn SSL_CTX_set_ecdh_auto ,
.Fn SSL_set_tmp_ecdh_callback ,
and
.Fn SSL_CTX_set_tmp_ecdh_callback
are deprecated and have no effect.
.Sh RETURN VALUES
.Fn SSL_set_tmp_ecdh
and
.Fn SSL_CTX_set_tmp_ecdh
return 1 on success or 0 on failure.
.Pp
.Fn SSL_set_ecdh_auto ,
.Fn SSL_CTX_set_ecdh_auto ,
.Fn SSL_set_tmp_ecdh_callback ,
and
.Fn SSL_CTX_set_tmp_ecdh_callback
always return 1.
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_CTX_set1_groups 3 ,
.Xr SSL_CTX_set_cipher_list 3 ,
.Xr SSL_CTX_set_options 3 ,
.Xr SSL_CTX_set_tmp_dh_callback 3 ,
.Xr SSL_new 3
.Sh HISTORY
.Fn SSL_set_tmp_ecdh ,
.Fn SSL_CTX_set_tmp_ecdh ,
.Fn SSL_set_tmp_ecdh_callback ,
and
.Fn SSL_CTX_set_tmp_ecdh_callback
first appeared in OpenSSL 0.9.8 and have been available since
.Ox 4.5 .
.Pp
.Fn SSL_CTX_set_ecdh_auto
and
.Fn SSL_set_ecdh_auto
first appeared in OpenSSL 1.0.2 and have been available since
.Ox 5.7 .