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>.