mirror of
https://github.com/openssl/openssl.git
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1c3ace6898
Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/9699)
294 lines
10 KiB
Plaintext
294 lines
10 KiB
Plaintext
=pod
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=head1 NAME
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provider-digest - The digest library E<lt>-E<gt> provider functions
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=head1 SYNOPSIS
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=for comment multiple includes
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#include <openssl/core_numbers.h>
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#include <openssl/core_names.h>
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/*
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* Digests support the following function signatures in OSSL_DISPATCH arrays.
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* (The function signatures are not actual functions).
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*/
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/* Context management */
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void *OP_digest_newctx(void *provctx);
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void OP_digest_freectx(void *dctx);
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void *OP_digest_dupctx(void *dctx);
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/* Digest generation */
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int OP_digest_init(void *dctx);
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int OP_digest_update(void *dctx, const unsigned char *in, size_t inl);
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int OP_digest_final(void *dctx, unsigned char *out, size_t *outl,
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size_t outsz);
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int OP_digest_digest(void *provctx, const unsigned char *in, size_t inl,
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unsigned char *out, size_t *outl, size_t outsz);
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/* Digest parameter descriptors */
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const OSSL_PARAM *OP_cipher_gettable_params(void);
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/* Digest operation parameter descriptors */
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const OSSL_PARAM *OP_cipher_gettable_ctx_params(void);
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const OSSL_PARAM *OP_cipher_settable_ctx_params(void);
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/* Digest parameters */
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int OP_digest_get_params(OSSL_PARAM params[]);
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/* Digest operation parameters */
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int OP_digest_set_ctx_params(void *dctx, const OSSL_PARAM params[]);
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int OP_digest_get_ctx_params(void *dctx, OSSL_PARAM params[]);
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=head1 DESCRIPTION
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This documentation is primarily aimed at provider authors. See L<provider(7)>
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for further information.
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The DIGEST operation enables providers to implement digest algorithms and make
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them available to applications via the API functions L<EVP_DigestInit_ex(3)>,
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L<EVP_DigestUpdate(3)> and L<EVP_DigestFinal(3)> (and other related functions).
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All "functions" mentioned here are passed as function pointers between
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F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays via
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B<OSSL_ALGORITHM> arrays that are returned by the provider's
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provider_query_operation() function
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(see L<provider-base(7)/Provider Functions>).
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All these "functions" have a corresponding function type definition
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named B<OSSL_{name}_fn>, and a helper function to retrieve the
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function pointer from an B<OSSL_DISPATCH> element named
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B<OSSL_get_{name}>.
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For example, the "function" OP_digest_newctx() has these:
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typedef void *(OSSL_OP_digest_newctx_fn)(void *provctx);
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static ossl_inline OSSL_OP_digest_newctx_fn
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OSSL_get_OP_digest_newctx(const OSSL_DISPATCH *opf);
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B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
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macros in L<openssl-core_numbers.h(7)>, as follows:
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OP_digest_newctx OSSL_FUNC_DIGEST_NEWCTX
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OP_digest_freectx OSSL_FUNC_DIGEST_FREECTX
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OP_digest_dupctx OSSL_FUNC_DIGEST_DUPCTX
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OP_digest_init OSSL_FUNC_DIGEST_INIT
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OP_digest_update OSSL_FUNC_DIGEST_UPDATE
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OP_digest_final OSSL_FUNC_DIGEST_FINAL
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OP_digest_digest OSSL_FUNC_DIGEST_DIGEST
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OP_digest_get_params OSSL_FUNC_DIGEST_GET_PARAMS
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OP_digest_get_ctx_params OSSL_FUNC_DIGEST_GET_CTX_PARAMS
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OP_digest_set_ctx_params OSSL_FUNC_DIGEST_SET_CTX_PARAMS
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OP_digest_gettable_params OSSL_FUNC_DIGEST_GETTABLE_PARAMS
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OP_digest_gettable_ctx_params OSSL_FUNC_DIGEST_GETTABLE_CTX_PARAMS
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OP_digest_settable_ctx_params OSSL_FUNC_DIGEST_SETTABLE_CTX_PARAMS
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A digest algorithm implementation may not implement all of these functions.
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In order to be usable all or none of OP_digest_newctx, OP_digest_freectx,
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OP_digest_init, OP_digest_update and OP_digest_final should be implemented.
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All other functions are optional.
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=head2 Context Management Functions
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OP_digest_newctx() should create and return a pointer to a provider side
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structure for holding context information during a digest operation.
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A pointer to this context will be passed back in a number of the other digest
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operation function calls.
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The parameter B<provctx> is the provider context generated during provider
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initialisation (see L<provider(3)>).
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OP_digest_freectx() is passed a pointer to the provider side digest context in
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the B<dctx> parameter.
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This function should free any resources associated with that context.
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OP_digest_dupctx() should duplicate the provider side digest context in the
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B<dctx> parameter and return the duplicate copy.
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=head2 Digest Generation Functions
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OP_digest_init() initialises a digest operation given a newly created
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provider side digest context in the B<dctx> parameter.
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OP_digest_update() is called to supply data to be digested as part of a
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previously initialised digest operation.
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The B<dctx> parameter contains a pointer to a previously initialised provider
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side context.
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OP_digest_update() should digest B<inl> bytes of data at the location pointed to
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by B<in>.
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OP_digest_update() may be called multiple times for a single digest operation.
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OP_digest_final() generates a digest started through previous OP_digest_init()
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and OP_digest_update() calls.
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The B<dctx> parameter contains a pointer to the provider side context.
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The digest should be written to B<*out> and the length of the digest to
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B<*outl>.
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The digest should not exceed B<outsz> bytes.
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OP_digest_digest() is a "oneshot" digest function.
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No provider side digest context is used.
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Instead the provider context that was created during provider initialisation is
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passed in the B<provctx> parameter (see L<provider(3)>).
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B<inl> bytes at B<in> should be digested and the result should be stored at
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B<out>. The length of the digest should be stored in B<*outl> which should not
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exceed B<outsz> bytes.
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=head2 Digest Parameters
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See L<OSSL_PARAM(3)> for further details on the parameters structure used by
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these functions.
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OP_digest_get_params() gets details of the algorithm implementation
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and stores them in B<params>.
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OP_digest_set_ctx_params() sets digest operation parameters for the
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provider side digest context B<dctx> to B<params>.
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Any parameter settings are additional to any that were previously set.
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OP_digest_get_ctx_params() gets digest operation details details from
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the given provider side digest context B<dctx> and stores them in B<params>.
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OP_digest_gettable_params(), OP_digest_gettable_ctx_params(), and
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OP_digest_settable_ctx_params() all return constant B<OSSL_PARAM> arrays
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as descriptors of the parameters that OP_digest_get_params(),
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OP_digest_get_ctx_params(), and OP_digest_set_ctx_params() can handle,
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respectively.
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Parameters currently recognised by built-in digests with this function
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are as follows. Not all parameters are relevant to, or are understood
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by all digests:
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=over 4
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=item B<OSSL_DIGEST_PARAM_BLOCK_SIZE> (size_t)
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The digest block size.
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=item B<OSSL_DIGEST_PARAM_SIZE> (size_t)
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The digest output size.
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=item B<OSSL_DIGEST_PARAM_FLAGS> (unsigned long)
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Diverse flags that describe exceptional behaviour for the digest:
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=over 4
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=item B<EVP_MD_FLAG_ONESHOT>
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This digest method can only handle one block of input.
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=item B<EVP_MD_FLAG_XOF>
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This digest method is an extensible-output function (XOF) and supports
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setting the B<OSSL_DIGEST_PARAM_XOFLEN> parameter.
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=item B<EVP_MD_FLAG_DIGALGID_NULL>
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When setting up a DigestAlgorithmIdentifier, this flag will have the
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parameter set to NULL by default. Use this for PKCS#1. I<Note: if
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combined with EVP_MD_FLAG_DIGALGID_ABSENT, the latter will override.>
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=item B<EVP_MD_FLAG_DIGALGID_ABSENT>
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When setting up a DigestAlgorithmIdentifier, this flag will have the
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parameter be left absent by default. I<Note: if combined with
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EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
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=item B<EVP_MD_FLAG_DIGALGID_CUSTOM>
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Custom DigestAlgorithmIdentifier handling via ctrl, with
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B<EVP_MD_FLAG_DIGALGID_ABSENT> as default. I<Note: if combined with
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EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
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Currently unused.
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=back
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=back
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=head2 Digest Context Parameters
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OP_digest_set_ctx_params() sets digest parameters associated with the
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given provider side digest context B<dctx> to B<params>.
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Any parameter settings are additional to any that were previously set.
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See L<OSSL_PARAM(3)> for further details on the parameters structure.
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OP_digest_get_ctx_params() gets details of currently set parameters
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values associated with the give provider side digest context B<dctx>
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and stores them in B<params>.
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See L<OSSL_PARAM(3)> for further details on the parameters structure.
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Parameters currently recognised by built-in digests are as follows. Not all
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parameters are relevant to, or are understood by all digests:
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=over 4
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=item B<OSSL_DIGEST_PARAM_XOFLEN> (size_t)
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Sets the digest length for extendable output functions.
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=item B<OSSL_DIGEST_PARAM_SSL3_MS> (octet string)
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This parameter is set by libssl in order to calculate a signature hash for an
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SSLv3 CertificateVerify message as per RFC6101.
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It is only set after all handshake messages have already been digested via
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OP_digest_update() calls.
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The parameter provides the master secret value to be added to the digest.
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The digest implementation should calculate the complete digest as per RFC6101
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section 5.6.8.
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The next call after setting this parameter will be OP_digest_final().
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This is only relevant for implementations of SHA1 or MD5_SHA1.
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=item B<OSSL_DIGEST_PARAM_PAD_TYPE> (uint)
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Sets the pad type to be used.
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The only built-in digest that uses this is MDC2.
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Normally the final MDC2 block is padded with 0s.
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If the pad type is set to 2 then the final block is padded with 0x80 followed by
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0s.
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=item B<OSSL_DIGEST_PARAM_MICALG> (utf8 string)
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Gets the digest Message Integrity Check algorithm string.
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This is used when creating S/MIME multipart/signed messages, as specified in
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RFC 5751.
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=back
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=head1 RETURN VALUES
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OP_digest_newctx() and OP_digest_dupctx() should return the newly created
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provider side digest context, or NULL on failure.
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OP_digest_init(), OP_digest_update(), OP_digest_final(), OP_digest_digest(),
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OP_digest_set_params() and OP_digest_get_params() should return 1 for success or
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0 on error.
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OP_digest_size() should return the digest size.
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OP_digest_block_size() should return the block size of the underlying digest
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algorithm.
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=head1 SEE ALSO
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L<provider(7)>
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=head1 HISTORY
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The provider DIGEST interface was introduced in OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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