EVP_MD_METH_NEW(3ossl)

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version 15.1 · 2 versions

15.1 · freebsd 15.1 (latest)
14.5 · freebsd 14.5

💅 EVP_MD_METH_NEW(3ossl) — bestie's guide to legacy digest-method building 🧚

okay so this is a page from the OpenSSL manual, section 3ossl, and it's literally all about the legacy EVP_MD method-building routines. ngl, this whole thing is deprecated, so consider this a museum tour with me as your very excited docent 🎀

✨ 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 — the routines to build up legacy EVP_MD methods 🫶

🌸 SYNOPSIS 🌸

#include <openssl/evp.h>

okay so heads up bestie: the following functions have been deprecated since OpenSSL 3.0, and can be hidden entirely by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

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 🦋

okay first thing's first, and I need you to hear me: all of the functions described on this page are deprecated. like, every single one. Applications should instead use the OSSL_PROVIDER APIs. that's the assignment, bestie 💅

so. the EVP_MD type is a structure for digest method implementation. it can also have associated public/private key signing and verifying routines. versatile icon behavior ✨

EVP_MD_meth_new() creates a new EVP_MD structure. and plot twist: 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. and if the argument is NULL, nothing is done — no drama, no crash, we love a chill function 🙈

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_get0_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_get0_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. the getters said "we're matching the setters' energy" and honestly? iconic 🌈

🍓 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 (slay, always succeeds 💖). 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.

👑 HISTORY 👑

all of these functions were deprecated in OpenSSL 3.0. periodt.

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. a whole glow-up timeline fr fr ✨

🎀 COPYRIGHT 🎀

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>.

okay that's the whole page, bestie, you ate 💅 stay hydrated, don't build new legacy EVP_MD methods, and remember: this was OpenSSL 3.5.6, dated 2026-04-07 🦋 love u, bye! 🫶

📦 where this page comes from

freebsd 15.1: base 15.1
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms