- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- SEE ALSO
- HISTORY
- COPYRIGHT

# NAME

EVP_MD_meth_new, EVP_MD_meth_dup, 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 legacy 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. These EVP_MD structures are reference counted.

`EVP_MD_meth_dup()` creates a copy of md.

`EVP_MD_meth_free()` decrements the reference count for the EVP_MD structure. If the reference count drops to 0 then the structure is freed.

`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_XOF

  This digest method is an extensible-output function (XOF) and supports the EVP_MD_CTRL_XOF_LEN control.

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()`, `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_Digest()`, `EVP_DigestUpdate()` and `EVP_SignUpdate()`.

`EVP_MD_meth_set_final()` sets the digest final function for md. The digest final function is called by `EVP_Digest()`, `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. See EVP_MD_CTX_ctrl(3) for the available controls.

`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. The EVP_MD structure created with these functions became reference counted in OpenSSL 3.0.

# COPYRIGHT

Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (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.