195 lines
5.4 KiB
Groff
195 lines
5.4 KiB
Groff
.\" $OpenBSD: DH_set_method.3,v 1.9 2023/11/19 10:34:26 tb Exp $
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.\" OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.\"
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.\" This file was written by Ulf Moeller <ulf@openssl.org>.
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.\" Copyright (c) 2000, 2002, 2007 The OpenSSL Project. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: November 19 2023 $
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.Dt DH_SET_METHOD 3
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.Os
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.Sh NAME
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.Nm DH_set_default_method ,
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.Nm DH_get_default_method ,
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.Nm DH_set_method ,
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.Nm DH_new_method ,
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.Nm DH_OpenSSL
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.Nd select DH method
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.Sh SYNOPSIS
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.In openssl/dh.h
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.Ft void
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.Fo DH_set_default_method
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.Fa "const DH_METHOD *meth"
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.Fc
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.Ft const DH_METHOD *
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.Fo DH_get_default_method
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.Fa void
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.Fc
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.Ft int
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.Fo DH_set_method
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.Fa "DH *dh"
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.Fa "const DH_METHOD *meth"
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.Fc
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.Ft DH *
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.Fo DH_new_method
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.Fa "ENGINE *engine"
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.Fc
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.Ft const DH_METHOD *
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.Fo DH_OpenSSL
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.Fa void
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.Fc
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.Sh DESCRIPTION
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A
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.Vt DH_METHOD
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object contains pointers to the functions
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used for Diffie-Hellman operations.
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By default, the internal implementation returned by
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.Fn DH_OpenSSL
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is used.
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By selecting another method, alternative implementations
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such as hardware accelerators may be used.
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.Pp
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.Fn DH_set_default_method
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selects
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.Fa meth
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as the default method for all
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.Vt DH
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structures created later.
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.Pp
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.Fn DH_get_default_method
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returns a pointer to the current default method.
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.Pp
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.Fn DH_set_method
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selects
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.Fa meth
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to perform all operations using the key
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.Fa dh .
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This replaces the
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.Vt DH_METHOD
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used by the
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.Fa dh
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key.
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It is possible to have
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.Vt DH
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keys that only work with certain
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.Vt DH_METHOD
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implementations,
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and in such cases attempting to change the
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.Vt DH_METHOD
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for the key can have unexpected results.
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.Pp
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.Fn DH_new_method
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allocates and initializes a
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.Vt DH
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structure.
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The
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.Fa engine
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argument is ignored and
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the default method controlled by
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.Fn DH_set_default_method
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is used.
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.Pp
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The
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.Vt DH_METHOD
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structure is defined as follows:
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.Bd -literal
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typedef struct dh_meth_st
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{
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/* name of the implementation */
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const char *name;
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/* generate private and public DH values for key agreement */
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int (*generate_key)(DH *dh);
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/* compute shared secret */
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int (*compute_key)(unsigned char *key, BIGNUM *pub_key, DH *dh);
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/* compute r = a ^ p mod m (May be NULL for some implementations) */
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int (*bn_mod_exp)(DH *dh, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
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const BIGNUM *m, BN_CTX *ctx,
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BN_MONT_CTX *m_ctx);
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/* called at DH_new */
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int (*init)(DH *dh);
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/* called at DH_free */
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int (*finish)(DH *dh);
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int flags;
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char *app_data; /* ?? */
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} DH_METHOD;
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.Ed
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.Sh RETURN VALUES
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.Fn DH_OpenSSL
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and
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.Fn DH_get_default_method
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return pointers to the respective
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.Vt DH_METHOD .
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.Pp
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.Fn DH_set_method
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returns 1 on success or 0 on failure.
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Currently, it cannot fail.
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.Pp
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.Fn DH_new_method
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returns
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.Dv NULL
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and sets an error code that can be obtained by
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.Xr ERR_get_error 3
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if the allocation fails.
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Otherwise it returns a pointer to the newly allocated structure.
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.Sh SEE ALSO
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.Xr DH_new 3
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.Sh HISTORY
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.Fn DH_set_default_method ,
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.Fn DH_get_default_method ,
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.Fn DH_set_method ,
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.Fn DH_new_method
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and
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.Fn DH_OpenSSL
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first appeared in OpenSSL 0.9.5 and have been available since
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.Ox 2.7 .
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