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.\" ========================================================================
.\"
.IX Title "DH_METH_NEW 3"
.TH DH_METH_NEW 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
DH_meth_new, DH_meth_free, DH_meth_dup, DH_meth_get0_name, DH_meth_set1_name, DH_meth_get_flags, DH_meth_set_flags, DH_meth_get0_app_data, DH_meth_set0_app_data, DH_meth_get_generate_key, DH_meth_set_generate_key, DH_meth_get_compute_key, DH_meth_set_compute_key, DH_meth_get_bn_mod_exp, DH_meth_set_bn_mod_exp, DH_meth_get_init, DH_meth_set_init, DH_meth_get_finish, DH_meth_set_finish, DH_meth_get_generate_params, DH_meth_set_generate_params \- Routines to build up DH methods
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/dh.h>
\&
\& DH_METHOD *DH_meth_new(const char *name, int flags);
\&
\& void DH_meth_free(DH_METHOD *dhm);
\&
\& DH_METHOD *DH_meth_dup(const DH_METHOD *dhm);
\&
\& const char *DH_meth_get0_name(const DH_METHOD *dhm);
\& int DH_meth_set1_name(DH_METHOD *dhm, const char *name);
\&
\& int DH_meth_get_flags(const DH_METHOD *dhm);
\& int DH_meth_set_flags(DH_METHOD *dhm, int flags);
\&
\& void *DH_meth_get0_app_data(const DH_METHOD *dhm);
\& int DH_meth_set0_app_data(DH_METHOD *dhm, void *app_data);
\&
\& int (*DH_meth_get_generate_key(const DH_METHOD *dhm))(DH *);
\& int DH_meth_set_generate_key(DH_METHOD *dhm, int (*generate_key)(DH *));
\&
\& int (*DH_meth_get_compute_key(const DH_METHOD *dhm))
\&     (unsigned char *key, const BIGNUM *pub_key, DH *dh);
\& int DH_meth_set_compute_key(DH_METHOD *dhm,
\&     int (*compute_key)(unsigned char *key, const BIGNUM *pub_key, DH *dh));
\&
\& int (*DH_meth_get_bn_mod_exp(const DH_METHOD *dhm))
\&     (const DH *dh, BIGNUM *r, const BIGNUM *a, const BIGNUM *p,
\&      const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
\& int DH_meth_set_bn_mod_exp(DH_METHOD *dhm,
\&     int (*bn_mod_exp)(const DH *dh, BIGNUM *r, const BIGNUM *a,
\&                       const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx,
\&                       BN_MONT_CTX *m_ctx));
\&
\& int (*DH_meth_get_init(const DH_METHOD *dhm))(DH *);
\& int DH_meth_set_init(DH_METHOD *dhm, int (*init)(DH *));
\&
\& int (*DH_meth_get_finish(const DH_METHOD *dhm))(DH *);
\& int DH_meth_set_finish(DH_METHOD *dhm, int (*finish)(DH *));
\&
\& int (*DH_meth_get_generate_params(const DH_METHOD *dhm))
\&     (DH *, int, int, BN_GENCB *);
\& int DH_meth_set_generate_params(DH_METHOD *dhm,
\&     int (*generate_params)(DH *, int, int, BN_GENCB *));
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fB\s-1DH_METHOD\s0\fR type is a structure used for the provision of custom \s-1DH\s0
implementations. It provides a set of functions used by OpenSSL for the
implementation of the various \s-1DH\s0 capabilities.
.PP
\&\fBDH_meth_new()\fR creates a new \fB\s-1DH_METHOD\s0\fR structure. It should be given a
unique \fBname\fR and a set of \fBflags\fR. The \fBname\fR should be a \s-1NULL\s0 terminated
string, which will be duplicated and stored in the \fB\s-1DH_METHOD\s0\fR object. It is
the callers responsibility to free the original string. The flags will be used
during the construction of a new \fB\s-1DH\s0\fR object based on this \fB\s-1DH_METHOD\s0\fR. Any
new \fB\s-1DH\s0\fR object will have those flags set by default.
.PP
\&\fBDH_meth_dup()\fR creates a duplicate copy of the \fB\s-1DH_METHOD\s0\fR object passed as a
parameter. This might be useful for creating a new \fB\s-1DH_METHOD\s0\fR based on an
existing one, but with some differences.
.PP
\&\fBDH_meth_free()\fR destroys a \fB\s-1DH_METHOD\s0\fR structure and frees up any memory
associated with it.
.PP
\&\fBDH_meth_get0_name()\fR will return a pointer to the name of this \s-1DH_METHOD.\s0 This
is a pointer to the internal name string and so should not be freed by the
caller. \fBDH_meth_set1_name()\fR sets the name of the \s-1DH_METHOD\s0 to \fBname\fR. The
string is duplicated and the copy is stored in the \s-1DH_METHOD\s0 structure, so the
caller remains responsible for freeing the memory associated with the name.
.PP
\&\fBDH_meth_get_flags()\fR returns the current value of the flags associated with this
\&\s-1DH_METHOD.\s0 \fBDH_meth_set_flags()\fR provides the ability to set these flags.
.PP
The functions \fBDH_meth_get0_app_data()\fR and \fBDH_meth_set0_app_data()\fR provide the
ability to associate implementation specific data with the \s-1DH_METHOD.\s0 It is
the application's responsibility to free this data before the \s-1DH_METHOD\s0 is
freed via a call to \fBDH_meth_free()\fR.
.PP
\&\fBDH_meth_get_generate_key()\fR and \fBDH_meth_set_generate_key()\fR get and set the
function used for generating a new \s-1DH\s0 key pair respectively. This function will
be called in response to the application calling \fBDH_generate_key()\fR. The
parameter for the function has the same meaning as for \fBDH_generate_key()\fR.
.PP
\&\fBDH_meth_get_compute_key()\fR and \fBDH_meth_set_compute_key()\fR get and set the
function used for computing a new \s-1DH\s0 shared secret respectively. This function
will be called in response to the application calling \fBDH_compute_key()\fR. The
parameters for the function have the same meaning as for \fBDH_compute_key()\fR.
.PP
\&\fBDH_meth_get_bn_mod_exp()\fR and \fBDH_meth_set_bn_mod_exp()\fR get and set the function
used for computing the following value:
.PP
.Vb 1
\& r = a ^ p mod m
.Ve
.PP
This function will be called by the default OpenSSL function for
\&\fBDH_generate_key()\fR. The result is stored in the \fBr\fR parameter. This function
may be \s-1NULL\s0 unless using the default generate key function, in which case it
must be present.
.PP
\&\fBDH_meth_get_init()\fR and \fBDH_meth_set_init()\fR get and set the function used
for creating a new \s-1DH\s0 instance respectively. This function will be
called in response to the application calling \fBDH_new()\fR (if the current default
\&\s-1DH_METHOD\s0 is this one) or \fBDH_new_method()\fR. The \fBDH_new()\fR and \fBDH_new_method()\fR
functions will allocate the memory for the new \s-1DH\s0 object, and a pointer to this
newly allocated structure will be passed as a parameter to the function. This
function may be \s-1NULL.\s0
.PP
\&\fBDH_meth_get_finish()\fR and \fBDH_meth_set_finish()\fR get and set the function used
for destroying an instance of a \s-1DH\s0 object respectively. This function will be
called in response to the application calling \fBDH_free()\fR. A pointer to the \s-1DH\s0
to be destroyed is passed as a parameter. The destroy function should be used
for \s-1DH\s0 implementation specific clean up. The memory for the \s-1DH\s0 itself should
not be freed by this function. This function may be \s-1NULL.\s0
.PP
\&\fBDH_meth_get_generate_params()\fR and \fBDH_meth_set_generate_params()\fR get and set the
function used for generating \s-1DH\s0 parameters respectively. This function will be
called in response to the application calling \fBDH_generate_parameters_ex()\fR (or
\&\fBDH_generate_parameters()\fR). The parameters for the function have the same
meaning as for \fBDH_generate_parameters_ex()\fR. This function may be \s-1NULL.\s0
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBDH_meth_new()\fR and \fBDH_meth_dup()\fR return the newly allocated \s-1DH_METHOD\s0 object
or \s-1NULL\s0 on failure.
.PP
\&\fBDH_meth_get0_name()\fR and \fBDH_meth_get_flags()\fR return the name and flags
associated with the \s-1DH_METHOD\s0 respectively.
.PP
All other DH_meth_get_*() functions return the appropriate function pointer
that has been set in the \s-1DH_METHOD,\s0 or \s-1NULL\s0 if no such pointer has yet been
set.
.PP
\&\fBDH_meth_set1_name()\fR and all DH_meth_set_*() functions return 1 on success or
0 on failure.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBDH_new\fR\|(3), \fBDH_new\fR\|(3), \fBDH_generate_parameters\fR\|(3), \fBDH_generate_key\fR\|(3),
\&\fBDH_set_method\fR\|(3), \fBDH_size\fR\|(3), \fBDH_get0_pqg\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
The functions described here were added in OpenSSL 1.1.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2016\-2018 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.