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

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);

DESCRIPTION

       The 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 EVP_MD structure.

       EVP_MD_meth_dup() creates a copy of md.

       EVP_MD_meth_free() destroys a EVP_MD structure.

       EVP_MD_meth_set_input_blocksize() sets the internal input block size for the method md to
       blocksize bytes.

       EVP_MD_meth_set_result_size() sets the size of the result that the digest method in md is
       expected to produce to 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 datasize.

       EVP_MD_meth_set_flags() sets the flags to describe optional behaviours in the particular
       md.  Several flags can be or'd together.  The available flags are:

       EVP_MD_FLAG_ONESHOT
           This digest method can only handles one block of input.

       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.  Note: if combined with
           EVP_MD_FLAG_DIGALGID_ABSENT, the latter will override.

       EVP_MD_FLAG_DIGALGID_ABSENT
           When setting up a DigestAlgorithmIdentifier, this flag will have the parameter be left
           absent by default.  Note: if combined with EVP_MD_FLAG_DIGALGID_NULL, the latter will
           be overridden.

       EVP_MD_FLAG_DIGALGID_CUSTOM
           Custom DigestAlgorithmIdentifier handling via ctrl, with EVP_MD_FLAG_DIGALGID_ABSENT
           as default.  Note: if combined with EVP_MD_FLAG_DIGALGID_NULL, the latter will be
           overridden.  Currently unused.

       EVP_MD_meth_set_init() sets the digest init function for 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 md.  The digest update
       function is called by EVP_DigestUpdate(), EVP_SignUpdate().

       EVP_MD_meth_set_final() sets the digest final function for 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 md to do extra computations after the
       method's private data structure has been copied from one 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 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 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 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 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.

RETURN VALUES

       EVP_MD_meth_new() and EVP_MD_meth_dup() return a pointer to a newly created 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 md
       function.

SEE ALSO

       EVP_DigestInit(3), EVP_SignInit(3), EVP_VerifyInit(3)

HISTORY

       The EVP_MD structure was openly available in OpenSSL before version 1.1.  The functions
       described here were added in OpenSSL 1.1.

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 <https://www.openssl.org/source/license.html>.