=pod
=head1 NAME
EVP_MD_meth_dup,
EVP_MD_meth_new, EVP_MD_meth_free, EVP_MD_meth_set_input_blocksize,
EVP_MD_meth_set_result_size, EVP_MD_meth_set_app_datasize,
EVP_MD_meth_set_flags, EVP_MD_meth_set_init, EVP_MD_meth_set_update,
EVP_MD_meth_set_final, EVP_MD_meth_set_copy, EVP_MD_meth_set_cleanup,
EVP_MD_meth_set_ctrl, EVP_MD_meth_get_input_blocksize,
EVP_MD_meth_get_result_size, EVP_MD_meth_get_app_datasize,
EVP_MD_meth_get_flags, EVP_MD_meth_get_init, EVP_MD_meth_get_update,
EVP_MD_meth_get_final, EVP_MD_meth_get_copy, EVP_MD_meth_get_cleanup,
EVP_MD_meth_get_ctrl
- Routines to build up EVP_MD methods
=head1 SYNOPSIS
#include <openssl/evp.h>
EVP_MD *EVP_MD_meth_new(int md_type, int pkey_type);
void EVP_MD_meth_free(EVP_MD *md);
EVP_MD *EVP_MD_meth_dup(const EVP_MD *md);
int EVP_MD_meth_set_input_blocksize(EVP_MD *md, int blocksize);
int EVP_MD_meth_set_result_size(EVP_MD *md, int resultsize);
int EVP_MD_meth_set_app_datasize(EVP_MD *md, int datasize);
int EVP_MD_meth_set_flags(EVP_MD *md, unsigned long flags);
int EVP_MD_meth_set_init(EVP_MD *md, int (*init)(EVP_MD_CTX *ctx));
int EVP_MD_meth_set_update(EVP_MD *md, int (*update)(EVP_MD_CTX *ctx,
const void *data,
size_t count));
int EVP_MD_meth_set_final(EVP_MD *md, int (*final)(EVP_MD_CTX *ctx,
unsigned char *md));
int EVP_MD_meth_set_copy(EVP_MD *md, int (*copy)(EVP_MD_CTX *to,
const EVP_MD_CTX *from));
int EVP_MD_meth_set_cleanup(EVP_MD *md, int (*cleanup)(EVP_MD_CTX *ctx));
int EVP_MD_meth_set_ctrl(EVP_MD *md, int (*ctrl)(EVP_MD_CTX *ctx, int cmd,
int p1, void *p2));
int EVP_MD_meth_get_input_blocksize(const EVP_MD *md);
int EVP_MD_meth_get_result_size(const EVP_MD *md);
int EVP_MD_meth_get_app_datasize(const EVP_MD *md);
unsigned long EVP_MD_meth_get_flags(const EVP_MD *md);
int (*EVP_MD_meth_get_init(const EVP_MD *md))(EVP_MD_CTX *ctx);
int (*EVP_MD_meth_get_update(const EVP_MD *md))(EVP_MD_CTX *ctx,
const void *data,
size_t count);
int (*EVP_MD_meth_get_final(const EVP_MD *md))(EVP_MD_CTX *ctx,
unsigned char *md);
int (*EVP_MD_meth_get_copy(const EVP_MD *md))(EVP_MD_CTX *to,
const EVP_MD_CTX *from);
int (*EVP_MD_meth_get_cleanup(const EVP_MD *md))(EVP_MD_CTX *ctx);
int (*EVP_MD_meth_get_ctrl(const EVP_MD *md))(EVP_MD_CTX *ctx, int cmd,
int p1, void *p2);
=head1 DESCRIPTION
The B<EVP_MD> type is a structure for digest method implementation.
It can also have associated public/private key signing and verifying
routines.
EVP_MD_meth_new() creates a new B<EVP_MD> structure.
EVP_MD_meth_dup() creates a copy of B<md>.
EVP_MD_meth_free() destroys a B<EVP_MD> structure.
EVP_MD_meth_set_input_blocksize() sets the internal input block size
for the method B<md> to B<blocksize> bytes.
EVP_MD_meth_set_result_size() sets the size of the result that the
digest method in B<md> is expected to produce to B<resultsize> bytes.
The digest method may have its own private data, which OpenSSL will
allocate for it. EVP_MD_meth_set_app_datasize() should be used to
set the size for it to B<datasize>.
EVP_MD_meth_set_flags() sets the flags to describe optional
behaviours in the particular B<md>. Several flags can be or'd
together. The available flags are:
=over 4
=item EVP_MD_FLAG_ONESHOT
This digest method can only handles one block of input.
=item EVP_MD_FLAG_DIGALGID_NULL
When setting up a DigestAlgorithmIdentifier, this flag will have the
parameter set to NULL by default. Use this for PKCS#1. I<Note: if
combined with EVP_MD_FLAG_DIGALGID_ABSENT, the latter will override.>
=item EVP_MD_FLAG_DIGALGID_ABSENT
When setting up a DigestAlgorithmIdentifier, this flag will have the
parameter be left absent by default. I<Note: if combined with
EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
=item EVP_MD_FLAG_DIGALGID_CUSTOM
Custom DigestAlgorithmIdentifier handling via ctrl, with
B<EVP_MD_FLAG_DIGALGID_ABSENT> as default. I<Note: if combined with
EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
Currently unused.
=back
EVP_MD_meth_set_init() sets the digest init function for B<md>.
The digest init function is called by EVP_DigestInit(),
EVP_DigestInit_ex(), EVP_SignInit, EVP_SignInit_ex(), EVP_VerifyInit()
and EVP_VerifyInit_ex().
EVP_MD_meth_set_update() sets the digest update function for B<md>.
The digest update function is called by EVP_DigestUpdate(),
EVP_SignUpdate().
EVP_MD_meth_set_final() sets the digest final function for B<md>.
The digest final function is called by EVP_DigestFinal(),
EVP_DigestFinal_ex(), EVP_SignFinal() and EVP_VerifyFinal().
EVP_MD_meth_set_copy() sets the function for B<md> to do extra
computations after the method's private data structure has been copied
from one B<EVP_MD_CTX> to another. If all that's needed is to copy
the data, there is no need for this copy function.
Note that the copy function is passed two B<EVP_MD_CTX *>, the private
data structure is then available with EVP_MD_CTX_md_data().
This copy function is called by EVP_MD_CTX_copy() and
EVP_MD_CTX_copy_ex().
EVP_MD_meth_set_cleanup() sets the function for B<md> to do extra
cleanup before the method's private data structure is cleaned out and
freed.
Note that the cleanup function is passed a B<EVP_MD_CTX *>, the
private data structure is then available with EVP_MD_CTX_md_data().
This cleanup function is called by EVP_MD_CTX_reset() and
EVP_MD_CTX_free().
EVP_MD_meth_set_ctrl() sets the control function for B<md>.
EVP_MD_meth_get_input_blocksize(), EVP_MD_meth_get_result_size(),
EVP_MD_meth_get_app_datasize(), EVP_MD_meth_get_flags(),
EVP_MD_meth_get_init(), EVP_MD_meth_get_update(),
EVP_MD_meth_get_final(), EVP_MD_meth_get_copy(),
EVP_MD_meth_get_cleanup() and EVP_MD_meth_get_ctrl() are all used
to retrieve the method data given with the EVP_MD_meth_set_*()
functions above.
=head1 RETURN VALUES
EVP_MD_meth_new() and EVP_MD_meth_dup() return a pointer to a newly
created B<EVP_MD>, or NULL on failure.
All EVP_MD_meth_set_*() functions return 1.
EVP_MD_get_input_blocksize(), EVP_MD_meth_get_result_size(),
EVP_MD_meth_get_app_datasize() and EVP_MD_meth_get_flags() return the
indicated sizes or flags.
All other EVP_CIPHER_meth_get_*() functions return pointers to their
respective B<md> function.
=head1 SEE ALSO
L<EVP_DigestInit(3)>, L<EVP_SignInit(3)>, L<EVP_VerifyInit(3)>
=head1 HISTORY
The B<EVP_MD> structure was openly available in OpenSSL before version
1.1.0. The functions described here were added in OpenSSL 1.1.0.
=head1 COPYRIGHT
Copyright 2015-2017 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
