EVP_MD_METH_NEW(3)

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 - 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 (*control)(EVP_MD_CTX *ctx, int command, 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 handle 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_FLAG_FIPS
    This digest method is suitable for use in FIPS mode. Currently unused.

EVP_MD_meth_set_init() sets the digest init function for md. The digest init function is called by EVP_Digest(3), EVP_DigestInit(3), EVP_DigestInit_ex(3), EVP_SignInit, EVP_SignInit_ex(3), EVP_VerifyInit(3) and EVP_VerifyInit_ex(3).

EVP_MD_meth_set_update() sets the digest update function for md. The digest update function is called by EVP_Digest(3), EVP_DigestUpdate(3) and EVP_SignUpdate(3).

EVP_MD_meth_set_final() sets the digest final function for md. The digest final function is called by EVP_Digest(3), EVP_DigestFinal(3), EVP_DigestFinal_ex(3), EVP_SignFinal(3) and EVP_VerifyFinal(3).

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 object to another. If all that's needed is to copy the data, there is no need for this copy function. The copy function is passed two EVP_MD_CTX objects, the private data structure is then available with EVP_MD_CTX_md_data(3). This copy function is called by EVP_MD_CTX_copy(3) and EVP_MD_CTX_copy_ex(3).

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. The cleanup function is passed an EVP_MD_CTX object, the private data structure is then available with EVP_MD_CTX_md_data(3). This cleanup function is called by EVP_MD_CTX_reset(3) and EVP_MD_CTX_free(3).

EVP_MD_meth_set_ctrl() sets the control function for md. The control function supplied by the application program has to return 1 to indicate success, 0 to indicate failure, or -1 if the command is not supported for this digest method. See EVP_MD_CTX_ctrl(3) for the available command arguments.

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.

SEE ALSO
EVP_DigestInit(3), EVP_SignInit(3), EVP_VerifyInit(3)

HISTORY
All these functions first appeared in OpenSSL 1.1.0 and have been available since OpenBSD 7.1.