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Under GNU General Public License
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PROVIDER-DIGEST(7SSL) OpenSSL PROVIDER-DIGEST(7SSL)
NAME
provider-digest - The digest library <-> provider functions
SYNOPSIS
#include <openssl/core_dispatch.h>
#include <openssl/core_names.h>
/*
* Digests support the following function signatures in OSSL_DISPATCH arrays.
* (The function signatures are not actual functions).
*/
/* Context management */
void *OSSL_FUNC_digest_newctx(void *provctx);
void OSSL_FUNC_digest_freectx(void *dctx);
void *OSSL_FUNC_digest_dupctx(void *dctx);
/* Digest generation */
int OSSL_FUNC_digest_init(void *dctx, const OSSL_PARAM params[]);
int OSSL_FUNC_digest_update(void *dctx, const unsigned char *in, size_t inl);
int OSSL_FUNC_digest_final(void *dctx, unsigned char *out, size_t *outl,
size_t outsz);
int OSSL_FUNC_digest_digest(void *provctx, const unsigned char *in, size_t inl,
unsigned char *out, size_t *outl, size_t outsz);
/* Digest parameter descriptors */
const OSSL_PARAM *OSSL_FUNC_digest_gettable_params(void *provctx);
/* Digest operation parameter descriptors */
const OSSL_PARAM *OSSL_FUNC_digest_gettable_ctx_params(void *dctx,
void *provctx);
const OSSL_PARAM *OSSL_FUNC_digest_settable_ctx_params(void *dctx,
void *provctx);
/* Digest parameters */
int OSSL_FUNC_digest_get_params(OSSL_PARAM params[]);
/* Digest operation parameters */
int OSSL_FUNC_digest_set_ctx_params(void *dctx, const OSSL_PARAM params[]);
int OSSL_FUNC_digest_get_ctx_params(void *dctx, OSSL_PARAM params[]);
DESCRIPTION
This documentation is primarily aimed at provider authors. See provider(7) for further
information.
The DIGEST operation enables providers to implement digest algorithms and make them
available to applications via the API functions EVP_DigestInit_ex(3), EVP_DigestUpdate(3)
and EVP_DigestFinal(3) (and other related functions).
All "functions" mentioned here are passed as function pointers between libcrypto and the
provider in OSSL_DISPATCH arrays via OSSL_ALGORITHM arrays that are returned by the
provider's provider_query_operation() function (see "Provider Functions" in
provider-base(7)).
All these "functions" have a corresponding function type definition named
OSSL_FUNC_{name}_fn, and a helper function to retrieve the function pointer from an
OSSL_DISPATCH element named OSSL_FUNC_{name}. For example, the "function"
OSSL_FUNC_digest_newctx() has these:
typedef void *(OSSL_OSSL_FUNC_digest_newctx_fn)(void *provctx);
static ossl_inline OSSL_OSSL_FUNC_digest_newctx_fn
OSSL_FUNC_digest_newctx(const OSSL_DISPATCH *opf);
OSSL_DISPATCH arrays are indexed by numbers that are provided as macros in
openssl-core_dispatch.h(7), as follows:
OSSL_FUNC_digest_newctx OSSL_FUNC_DIGEST_NEWCTX
OSSL_FUNC_digest_freectx OSSL_FUNC_DIGEST_FREECTX
OSSL_FUNC_digest_dupctx OSSL_FUNC_DIGEST_DUPCTX
OSSL_FUNC_digest_init OSSL_FUNC_DIGEST_INIT
OSSL_FUNC_digest_update OSSL_FUNC_DIGEST_UPDATE
OSSL_FUNC_digest_final OSSL_FUNC_DIGEST_FINAL
OSSL_FUNC_digest_digest OSSL_FUNC_DIGEST_DIGEST
OSSL_FUNC_digest_get_params OSSL_FUNC_DIGEST_GET_PARAMS
OSSL_FUNC_digest_get_ctx_params OSSL_FUNC_DIGEST_GET_CTX_PARAMS
OSSL_FUNC_digest_set_ctx_params OSSL_FUNC_DIGEST_SET_CTX_PARAMS
OSSL_FUNC_digest_gettable_params OSSL_FUNC_DIGEST_GETTABLE_PARAMS
OSSL_FUNC_digest_gettable_ctx_params OSSL_FUNC_DIGEST_GETTABLE_CTX_PARAMS
OSSL_FUNC_digest_settable_ctx_params OSSL_FUNC_DIGEST_SETTABLE_CTX_PARAMS
A digest algorithm implementation may not implement all of these functions. In order to
be usable all or none of OSSL_FUNC_digest_newctx, OSSL_FUNC_digest_freectx,
OSSL_FUNC_digest_init, OSSL_FUNC_digest_update and OSSL_FUNC_digest_final should be
implemented. All other functions are optional.
Context Management Functions
OSSL_FUNC_digest_newctx() should create and return a pointer to a provider side structure
for holding context information during a digest operation. A pointer to this context will
be passed back in a number of the other digest operation function calls. The parameter
provctx is the provider context generated during provider initialisation (see
provider(7)).
OSSL_FUNC_digest_freectx() is passed a pointer to the provider side digest context in the
dctx parameter. This function should free any resources associated with that context.
OSSL_FUNC_digest_dupctx() should duplicate the provider side digest context in the dctx
parameter and return the duplicate copy.
Digest Generation Functions
OSSL_FUNC_digest_init() initialises a digest operation given a newly created provider side
digest context in the dctx parameter. The params, if not NULL, should be set on the
context in a manner similar to using OSSL_FUNC_digest_set_ctx_params().
OSSL_FUNC_digest_update() is called to supply data to be digested as part of a previously
initialised digest operation. The dctx parameter contains a pointer to a previously
initialised provider side context. OSSL_FUNC_digest_update() should digest inl bytes of
data at the location pointed to by in. OSSL_FUNC_digest_update() may be called multiple
times for a single digest operation.
OSSL_FUNC_digest_final() generates a digest started through previous
OSSL_FUNC_digest_init() and OSSL_FUNC_digest_update() calls. The dctx parameter contains
a pointer to the provider side context. The digest should be written to *out and the
length of the digest to *outl. The digest should not exceed outsz bytes.
OSSL_FUNC_digest_digest() is a "oneshot" digest function. No provider side digest context
is used. Instead the provider context that was created during provider initialisation is
passed in the provctx parameter (see provider(7)). inl bytes at in should be digested and
the result should be stored at out. The length of the digest should be stored in *outl
which should not exceed outsz bytes.
Digest Parameters
See OSSL_PARAM(3) for further details on the parameters structure used by these functions.
OSSL_FUNC_digest_get_params() gets details of the algorithm implementation and stores them
in params.
OSSL_FUNC_digest_set_ctx_params() sets digest operation parameters for the provider side
digest context dctx to params. Any parameter settings are additional to any that were
previously set. Passing NULL for params should return true.
OSSL_FUNC_digest_get_ctx_params() gets digest operation details details from the given
provider side digest context dctx and stores them in params. Passing NULL for params
should return true.
OSSL_FUNC_digest_gettable_params() returns a constant OSSL_PARAM array containing
descriptors of the parameters that OSSL_FUNC_digest_get_params() can handle.
OSSL_FUNC_digest_gettable_ctx_params() and OSSL_FUNC_digest_settable_ctx_params() both
return constant OSSL_PARAM arrays as descriptors of the parameters that
OSSL_FUNC_digest_get_ctx_params() and OSSL_FUNC_digest_set_ctx_params() can handle,
respectively. The array is based on the current state of the provider side context if
dctx is not NULL and on the provider side algorithm provctx otherwise.
Parameters currently recognised by built-in digests with this function are as follows. Not
all parameters are relevant to, or are understood by all digests:
"blocksize" (OSSL_DIGEST_PARAM_BLOCK_SIZE) <unsigned integer>
The digest block size. The length of the "blocksize" parameter should not exceed that
of a size_t.
"size" (OSSL_DIGEST_PARAM_SIZE) <unsigned integer>
The digest output size. The length of the "size" parameter should not exceed that of
a size_t.
"flags" (OSSL_DIGEST_PARAM_FLAGS) <unsigned integer>
Diverse flags that describe exceptional behaviour for the digest:
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 setting the
OSSL_DIGEST_PARAM_XOFLEN parameter.
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.
The length of the "flags" parameter should equal that of an unsigned long int.
Digest Context Parameters
OSSL_FUNC_digest_set_ctx_params() sets digest parameters associated with the given
provider side digest context dctx to params. Any parameter settings are additional to any
that were previously set. See OSSL_PARAM(3) for further details on the parameters
structure.
OSSL_FUNC_digest_get_ctx_params() gets details of currently set parameters values
associated with the give provider side digest context dctx and stores them in params. See
OSSL_PARAM(3) for further details on the parameters structure.
RETURN VALUES
OSSL_FUNC_digest_newctx() and OSSL_FUNC_digest_dupctx() should return the newly created
provider side digest context, or NULL on failure.
OSSL_FUNC_digest_init(), OSSL_FUNC_digest_update(), OSSL_FUNC_digest_final(),
OSSL_FUNC_digest_digest(), OSSL_FUNC_digest_set_params() and OSSL_FUNC_digest_get_params()
should return 1 for success or 0 on error.
OSSL_FUNC_digest_size() should return the digest size.
OSSL_FUNC_digest_block_size() should return the block size of the underlying digest
algorithm.
BUGS
The EVP_Q_digest(), EVP_Digest() and EVP_DigestFinal_ex() API calls do not expect the
digest size to be larger than EVP_MAX_MD_SIZE. Any algorithm which produces larger digests
is unusable with those API calls.
SEE ALSO
provider(7), OSSL_PROVIDER-FIPS(7), OSSL_PROVIDER-default(7), OSSL_PROVIDER-legacy(7),
EVP_MD-common(7), EVP_MD-BLAKE2(7), EVP_MD-MD2(7), EVP_MD-MD4(7), EVP_MD-MD5(7),
EVP_MD-MD5-SHA1(7), EVP_MD-MDC2(7), EVP_MD-RIPEMD160(7), EVP_MD-SHA1(7), EVP_MD-SHA2(7),
EVP_MD-SHA3(7), EVP_MD-SHAKE(7), EVP_MD-SM3(7), EVP_MD-WHIRLPOOL(7), life_cycle-digest(7),
EVP_DigestInit(3)
HISTORY
The provider DIGEST interface was introduced in OpenSSL 3.0.
COPYRIGHT
Copyright 2019-2021 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>.
3.0.2 2025-09-18 PROVIDER-DIGEST(7SSL)
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Under GNU General Public License
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