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.\" ========================================================================
.\"
.IX Title "PROVIDER-DIGEST 7"
.TH PROVIDER-DIGEST 7 "2023-05-31" "3.0.9" "OpenSSL"
.\" For nroff, turn off justification. Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
provider\-digest \- The digest library <\-> provider functions
.SH "LIBRARY"
libcrypto, -lcrypto
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 2
\& #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[]);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This documentation is primarily aimed at provider authors. See \fBprovider\fR\|(7)
for further information.
.PP
The \s-1DIGEST\s0 operation enables providers to implement digest algorithms and make
them available to applications via the \s-1API\s0 functions \fBEVP_DigestInit_ex\fR\|(3),
\&\fBEVP_DigestUpdate\fR\|(3) and \fBEVP_DigestFinal\fR\|(3) (and other related functions).
.PP
All \*(L"functions\*(R" mentioned here are passed as function pointers between
\&\fIlibcrypto\fR and the provider in \s-1\fBOSSL_DISPATCH\s0\fR\|(3) arrays via
\&\s-1\fBOSSL_ALGORITHM\s0\fR\|(3) arrays that are returned by the provider's
\&\fBprovider_query_operation()\fR function
(see \*(L"Provider Functions\*(R" in \fBprovider\-base\fR\|(7)).
.PP
All these \*(L"functions\*(R" have a corresponding function type definition
named \fBOSSL_FUNC_{name}_fn\fR, and a helper function to retrieve the
function pointer from an \s-1\fBOSSL_DISPATCH\s0\fR\|(3) element named
\&\fBOSSL_FUNC_{name}\fR.
For example, the \*(L"function\*(R" \fBOSSL_FUNC_digest_newctx()\fR has these:
.PP
.Vb 3
\& typedef void *(OSSL_FUNC_digest_newctx_fn)(void *provctx);
\& static ossl_inline OSSL_FUNC_digest_newctx_fn
\& OSSL_FUNC_digest_newctx(const OSSL_DISPATCH *opf);
.Ve
.PP
\&\s-1\fBOSSL_DISPATCH\s0\fR\|(3) arrays are indexed by numbers that are provided as
macros in \fBopenssl\-core_dispatch.h\fR\|(7), as follows:
.PP
.Vb 3
\& 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
.Ve
.PP
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.
.SS "Context Management Functions"
.IX Subsection "Context Management Functions"
\&\fBOSSL_FUNC_digest_newctx()\fR 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 \fIprovctx\fR is the provider context generated during provider
initialisation (see \fBprovider\fR\|(7)).
.PP
\&\fBOSSL_FUNC_digest_freectx()\fR is passed a pointer to the provider side digest context in
the \fIdctx\fR parameter.
This function should free any resources associated with that context.
.PP
\&\fBOSSL_FUNC_digest_dupctx()\fR should duplicate the provider side digest context in the
\&\fIdctx\fR parameter and return the duplicate copy.
.SS "Digest Generation Functions"
.IX Subsection "Digest Generation Functions"
\&\fBOSSL_FUNC_digest_init()\fR initialises a digest operation given a newly created
provider side digest context in the \fIdctx\fR parameter.
The \fIparams\fR, if not \s-1NULL,\s0 should be set on the context in a manner similar to
using \fBOSSL_FUNC_digest_set_ctx_params()\fR.
.PP
\&\fBOSSL_FUNC_digest_update()\fR is called to supply data to be digested as part of a
previously initialised digest operation.
The \fIdctx\fR parameter contains a pointer to a previously initialised provider
side context.
\&\fBOSSL_FUNC_digest_update()\fR should digest \fIinl\fR bytes of data at the location pointed to
by \fIin\fR.
\&\fBOSSL_FUNC_digest_update()\fR may be called multiple times for a single digest operation.
.PP
\&\fBOSSL_FUNC_digest_final()\fR generates a digest started through previous \fBOSSL_FUNC_digest_init()\fR
and \fBOSSL_FUNC_digest_update()\fR calls.
The \fIdctx\fR parameter contains a pointer to the provider side context.
The digest should be written to \fI*out\fR and the length of the digest to
\&\fI*outl\fR.
The digest should not exceed \fIoutsz\fR bytes.
.PP
\&\fBOSSL_FUNC_digest_digest()\fR is a \*(L"oneshot\*(R" digest function.
No provider side digest context is used.
Instead the provider context that was created during provider initialisation is
passed in the \fIprovctx\fR parameter (see \fBprovider\fR\|(7)).
\&\fIinl\fR bytes at \fIin\fR should be digested and the result should be stored at
\&\fIout\fR. The length of the digest should be stored in \fI*outl\fR which should not
exceed \fIoutsz\fR bytes.
.SS "Digest Parameters"
.IX Subsection "Digest Parameters"
See \s-1\fBOSSL_PARAM\s0\fR\|(3) for further details on the parameters structure used by
these functions.
.PP
\&\fBOSSL_FUNC_digest_get_params()\fR gets details of the algorithm implementation
and stores them in \fIparams\fR.
.PP
\&\fBOSSL_FUNC_digest_set_ctx_params()\fR sets digest operation parameters for the
provider side digest context \fIdctx\fR to \fIparams\fR.
Any parameter settings are additional to any that were previously set.
Passing \s-1NULL\s0 for \fIparams\fR should return true.
.PP
\&\fBOSSL_FUNC_digest_get_ctx_params()\fR gets digest operation details details from
the given provider side digest context \fIdctx\fR and stores them in \fIparams\fR.
Passing \s-1NULL\s0 for \fIparams\fR should return true.
.PP
\&\fBOSSL_FUNC_digest_gettable_params()\fR returns a constant \s-1\fBOSSL_PARAM\s0\fR\|(3) array
containing descriptors of the parameters that \fBOSSL_FUNC_digest_get_params()\fR
can handle.
.PP
\&\fBOSSL_FUNC_digest_gettable_ctx_params()\fR and
\&\fBOSSL_FUNC_digest_settable_ctx_params()\fR both return constant
\&\s-1\fBOSSL_PARAM\s0\fR\|(3) arrays as descriptors of the parameters that
\&\fBOSSL_FUNC_digest_get_ctx_params()\fR and \fBOSSL_FUNC_digest_set_ctx_params()\fR
can handle, respectively. The array is based on the current state of
the provider side context if \fIdctx\fR is not \s-1NULL\s0 and on the provider
side algorithm \fIprovctx\fR otherwise.
.PP
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:
.ie n .IP """blocksize"" (\fB\s-1OSSL_DIGEST_PARAM_BLOCK_SIZE\s0\fR) <unsigned integer>" 4
.el .IP "``blocksize'' (\fB\s-1OSSL_DIGEST_PARAM_BLOCK_SIZE\s0\fR) <unsigned integer>" 4
.IX Item "blocksize (OSSL_DIGEST_PARAM_BLOCK_SIZE) <unsigned integer>"
The digest block size.
The length of the \*(L"blocksize\*(R" parameter should not exceed that of a \fBsize_t\fR.
.ie n .IP """size"" (\fB\s-1OSSL_DIGEST_PARAM_SIZE\s0\fR) <unsigned integer>" 4
.el .IP "``size'' (\fB\s-1OSSL_DIGEST_PARAM_SIZE\s0\fR) <unsigned integer>" 4
.IX Item "size (OSSL_DIGEST_PARAM_SIZE) <unsigned integer>"
The digest output size.
The length of the \*(L"size\*(R" parameter should not exceed that of a \fBsize_t\fR.
.ie n .IP """flags"" (\fB\s-1OSSL_DIGEST_PARAM_FLAGS\s0\fR) <unsigned integer>" 4
.el .IP "``flags'' (\fB\s-1OSSL_DIGEST_PARAM_FLAGS\s0\fR) <unsigned integer>" 4
.IX Item "flags (OSSL_DIGEST_PARAM_FLAGS) <unsigned integer>"
Diverse flags that describe exceptional behaviour for the digest:
.RS 4
.IP "\fB\s-1EVP_MD_FLAG_ONESHOT\s0\fR" 4
.IX Item "EVP_MD_FLAG_ONESHOT"
This digest method can only handle one block of input.
.IP "\fB\s-1EVP_MD_FLAG_XOF\s0\fR" 4
.IX Item "EVP_MD_FLAG_XOF"
This digest method is an extensible-output function (\s-1XOF\s0) and supports
setting the \fB\s-1OSSL_DIGEST_PARAM_XOFLEN\s0\fR parameter.
.IP "\fB\s-1EVP_MD_FLAG_DIGALGID_NULL\s0\fR" 4
.IX Item "EVP_MD_FLAG_DIGALGID_NULL"
When setting up a DigestAlgorithmIdentifier, this flag will have the
parameter set to \s-1NULL\s0 by default. Use this for PKCS#1. \fINote: if
combined with \s-1EVP_MD_FLAG_DIGALGID_ABSENT,\s0 the latter will override.\fR
.IP "\fB\s-1EVP_MD_FLAG_DIGALGID_ABSENT\s0\fR" 4
.IX Item "EVP_MD_FLAG_DIGALGID_ABSENT"
When setting up a DigestAlgorithmIdentifier, this flag will have the
parameter be left absent by default. \fINote: if combined with
\&\s-1EVP_MD_FLAG_DIGALGID_NULL,\s0 the latter will be overridden.\fR
.IP "\fB\s-1EVP_MD_FLAG_DIGALGID_CUSTOM\s0\fR" 4
.IX Item "EVP_MD_FLAG_DIGALGID_CUSTOM"
Custom DigestAlgorithmIdentifier handling via ctrl, with
\&\fB\s-1EVP_MD_FLAG_DIGALGID_ABSENT\s0\fR as default. \fINote: if combined with
\&\s-1EVP_MD_FLAG_DIGALGID_NULL,\s0 the latter will be overridden.\fR
Currently unused.
.RE
.RS 4
.Sp
The length of the \*(L"flags\*(R" parameter should equal that of an
\&\fBunsigned long int\fR.
.RE
.SS "Digest Context Parameters"
.IX Subsection "Digest Context Parameters"
\&\fBOSSL_FUNC_digest_set_ctx_params()\fR sets digest parameters associated with the
given provider side digest context \fIdctx\fR to \fIparams\fR.
Any parameter settings are additional to any that were previously set.
See \s-1\fBOSSL_PARAM\s0\fR\|(3) for further details on the parameters structure.
.PP
\&\fBOSSL_FUNC_digest_get_ctx_params()\fR gets details of currently set parameters
values associated with the give provider side digest context \fIdctx\fR
and stores them in \fIparams\fR.
See \s-1\fBOSSL_PARAM\s0\fR\|(3) for further details on the parameters structure.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBOSSL_FUNC_digest_newctx()\fR and \fBOSSL_FUNC_digest_dupctx()\fR should return the newly created
provider side digest context, or \s-1NULL\s0 on failure.
.PP
\&\fBOSSL_FUNC_digest_init()\fR, \fBOSSL_FUNC_digest_update()\fR, \fBOSSL_FUNC_digest_final()\fR, \fBOSSL_FUNC_digest_digest()\fR,
\&\fBOSSL_FUNC_digest_set_params()\fR and \fBOSSL_FUNC_digest_get_params()\fR should return 1 for success or
0 on error.
.PP
\&\fBOSSL_FUNC_digest_size()\fR should return the digest size.
.PP
\&\fBOSSL_FUNC_digest_block_size()\fR should return the block size of the underlying digest
algorithm.
.SH "BUGS"
.IX Header "BUGS"
The \fBEVP_Q_digest()\fR, \fBEVP_Digest()\fR and \fBEVP_DigestFinal_ex()\fR \s-1API\s0 calls do not
expect the digest size to be larger than \s-1EVP_MAX_MD_SIZE.\s0 Any algorithm which
produces larger digests is unusable with those \s-1API\s0 calls.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBprovider\fR\|(7), \s-1\fBOSSL_PROVIDER\-FIPS\s0\fR\|(7), \fBOSSL_PROVIDER\-default\fR\|(7),
\&\fBOSSL_PROVIDER\-legacy\fR\|(7),
\&\fBEVP_MD\-common\fR\|(7), \s-1\fBEVP_MD\-BLAKE2\s0\fR\|(7), \s-1\fBEVP_MD\-MD2\s0\fR\|(7),
\&\s-1\fBEVP_MD\-MD4\s0\fR\|(7), \s-1\fBEVP_MD\-MD5\s0\fR\|(7), \s-1\fBEVP_MD\-MD5\-SHA1\s0\fR\|(7),
\&\s-1\fBEVP_MD\-MDC2\s0\fR\|(7), \s-1\fBEVP_MD\-RIPEMD160\s0\fR\|(7), \s-1\fBEVP_MD\-SHA1\s0\fR\|(7),
\&\s-1\fBEVP_MD\-SHA2\s0\fR\|(7), \s-1\fBEVP_MD\-SHA3\s0\fR\|(7), \s-1\fBEVP_MD\-SHAKE\s0\fR\|(7),
\&\s-1\fBEVP_MD\-SM3\s0\fR\|(7), \s-1\fBEVP_MD\-WHIRLPOOL\s0\fR\|(7),
\&\s-1\fBEVP_MD\-NULL\s0\fR\|(7),
\&\fBlife_cycle\-digest\fR\|(7), \fBEVP_DigestInit\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
The provider \s-1DIGEST\s0 interface was introduced in OpenSSL 3.0.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2019\-2023 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.