Document the provider DIGEST operation

Extends the existing provider documentation with information about the
DIGEST operation. This is primarily for provider authors.

Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/9453)

2 files changed, 215 insertions, 1 deletions

diff --git a/doc/man7/provider-digest.pod b/doc/man7/provider-digest.pod
new file mode 100644
index 0000000000..f6c3286528
--- /dev/null
+++ b/doc/man7/provider-digest.pod
@@ -0,0 +1,214 @@
+=pod
+
+=head1 NAME
+
+provider-digest - The digest library E<lt>-E<gt> provider functions
+
+=head1 SYNOPSIS
+
+=for comment multiple includes
+
+ #include <openssl/core_numbers.h>
+ #include <openssl/core_names.h>
+
+ /*
+  * None of these are actual functions, but are displayed like this for
+  * the function signatures for functions that are offered as function
+  * pointers in OSSL_DISPATCH arrays.
+  */
+
+ /* Context management */
+ void *OP_digest_newctx(void *provctx);
+ void OP_digest_freectx(void *dctx);
+ void *OP_digest_dupctx(void *dctx);
+
+ /* Digest generation */
+ int OP_digest_init(void *dctx);
+ int OP_digest_update(void *dctx, const unsigned char *in, size_t inl);
+ int OP_digest_final(void *dctx, unsigned char *out, size_t *outl,
+                     size_t outsz);
+ int OP_digest_digest(void *provctx, const unsigned char *in, size_t inl,
+                      unsigned char *out, size_t *outl, size_t outsz);
+
+ /* Digest parameters */
+ size_t OP_digest_size(void);
+ size_t OP_digest_block_size(void);
+ int OP_digest_set_params(void *dctx, const OSSL_PARAM params[]);
+ int OP_digest_get_params(void *dctx, OSSL_PARAM params[]);
+
+=head1 DESCRIPTION
+
+This documentation is primarily aimed at provider authors. See L<provider(7)>
+for further information.
+
+The DIGEST operation enables providers to implement digest algorithms and make
+them available to applications via the API functions L<EVP_DigestInit_ex(3)>,
+L<EVP_DigestUpdate(3)> and L<EVP_DigestFinal(3)> (and other related functions).
+
+All "functions" mentioned here are passed as function pointers between
+F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays via
+B<OSSL_ALGORITHM> arrays that are returned by the provider's
+provider_query_operation() function
+(see L<provider-base(7)/Provider Functions>).
+
+All these "functions" have a corresponding function type definition
+named B<OSSL_{name}_fn>, and a helper function to retrieve the
+function pointer from an B<OSSL_DISPATCH> element named
+B<OSSL_get_{name}>.
+For example, the "function" OP_digest_newctx() has these:
+
+ typedef void *(OSSL_OP_digest_newctx_fn)(void *provctx);
+ static ossl_inline OSSL_OP_digest_newctx_fn
+     OSSL_get_OP_digest_newctx(const OSSL_DISPATCH *opf);
+
+B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
+macros in L<openssl-core_numbers.h(7)>, as follows:
+
+ OP_digest_newctx        OSSL_FUNC_DIGEST_NEWCTX
+ OP_digest_freectx       OSSL_FUNC_DIGEST_FREECTX
+ OP_digest_dupctx        OSSL_FUNC_DIGEST_DUPCTX
+
+ OP_digest_init          OSSL_FUNC_DIGEST_INIT
+ OP_digest_update        OSSL_FUNC_DIGEST_UPDATE
+ OP_digest_final         OSSL_FUNC_DIGEST_FINAL
+ OP_digest_digest        OSSL_FUNC_DIGEST_DIGEST
+
+ OP_digest_size          OSSL_FUNC_DIGEST_SIZE
+ OP_digest_block_size    OSSL_FUNC_DIGEST_BLOCK_SIZE
+ OP_digest_set_params    OSSL_FUNC_DIGEST_SET_PARAMS
+ OP_digest_get_params    OSSL_FUNC_DIGEST_GET_PARAMS
+
+A digest algorithm implementation may not implement all of these functions.
+In order to be useable all or none of OP_digest_newctx, OP_digest_freectx,
+OP_digest_init, OP_digest_update and OP_digest_final should be implemented.
+All other functions are optional.
+
+=head2 Context Management Functions
+
+OP_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 paramater B<provctx> is the provider context generated during provider
+initialisation (see L<provider(3)>).
+
+OP_digest_freectx() is passed a pointer to the provider side digest context in
+the B<dctx> parameter.
+This function should free any resources associated with that context.
+
+OP_digest_dupctx() should duplicate the provider side digest context in the
+B<dctx> parameter and return the duplicate copy.
+
+=head2 Digest Generation Functions
+
+OP_digest_init() initialises a digest operation given a newly created
+provider side digest context in the B<dctx> paramter.
+
+OP_digest_update() is called to supply data to be digested as part of a
+previously initialised digest operation.
+The B<dctx> parameter contains a pointer to a previously initialised provider
+side context.
+OP_digest_update() should digest B<inl> bytes of data at the location pointed to
+by B<in>.
+OP_digest_update() may be called multiple times for a single digest operation.
+
+OP_digest_final() generates a digest started through previous OP_digest_init()
+and OP_digest_update() calls.
+The B<dctx> parameter contains a pointer to the provider side context.
+The digest should be written to B<*out> and the length of the digest to
+B<*outl>.
+The digest should not exceed B<outsz> bytes.
+
+OP_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 B<provctx> parameter (see L<provider(3)>).
+B<inl> bytes at B<in> should be digested and the result should be stored at
+B<out>. The length of the digest should be stored in B<*outl> which should not
+exceed B<outsz> bytes.
+
+=head2 Digest Parameters
+
+OP_digest_size() should return the size of the digest.
+
+OP_digest_block_size() should return the size of the block size of the
+underlying digest algorithm.
+
+OP_digest_set_params() set digest parameters associated with the given provider
+side digest context B<dctx> to B<params>.
+Any parameter settings are additional to any that were previously set.
+See L<OSSL_PARAM(3)> for further details on the parameters structure.
+
+OP_digest_get_params() gets details of currently set parameters values associated
+with the give provider side digest context B<dctx> and stores them in B<params>.
+See L<OSSL_PARAM(3)> for further details on the parameters structure.
+
+Parameters currently recognised by built-in digests are as follows. Not all
+parametes are relevant to, or are understood by all digests:
+
+=over 4
+
+=item B<OSSL_DIGEST_PARAM_XOFLEN> (size_t)
+
+Sets the digest length for extendable output functions.
+
+=item B<OSSL_DIGEST_PARAM_SSL3_MS> (octet string)
+
+This parameter is set by libssl in order to calculate a signature hash for an
+SSLv3 CertificateVerify message as per RFC6101.
+It is only set after all handshake messages have already been digested via
+OP_digest_update() calls.
+The parameter provides the master secret value to be added to the digest.
+The digest implementation should calculate the complete digest as per RFC6101
+section 5.6.8.
+The next call after setting this parameter will be OP_digest_final().
+This is only relevant for implementations of SHA1 or MD5_SHA1.
+
+=item B<OSSL_DIGEST_PARAM_PAD_TYPE> (int)
+
+Sets the pad type to be used.
+The only built-in digest that uses this is MDC2.
+Normally the final MDC2 block is padded with 0s.
+If the pad type is set to 2 then the final block is padded with 0x80 followed by
+0s.
+
+=item B<OSSL_DIGEST_PARAM_MICALG> (utf8 string)
+
+Gets the digest Message Integrity Check algorithm string.
+This is used when creating S/MIME multipart/signed messages, as specified in
+RFC 5751.
+
+=back
+
+=head1 RETURN VALUES
+
+OP_digest_newctx() and OP_digest_dupctx() should return the newly created
+provider side digest context, or NULL on failure.
+
+OP_digest_init(), OP_digest_update(), OP_digest_final(), OP_digest_digest(),
+OP_digest_set_params() and OP_digest_get_params() should return 1 for success or
+0 on error.
+
+OP_digest_size() should return the digest size.
+
+OP_digest_block_size() should return the block size of the underlying digest
+algorithm.
+
+=head1 SEE ALSO
+
+L<provider(7)>
+
+=head1 HISTORY
+
+The provider DIGEST interface was introduced in OpenSSL 3.0.
+
+=head1 COPYRIGHT
+
+Copyright 2019 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
+L<https://www.openssl.org/source/license.html>.
+
+=cut
diff --git a/doc/man7/provider-keymgmt.pod b/doc/man7/provider-keymgmt.pod
index ed3deaae7b..40f1ad6327 100644
--- a/doc/man7/provider-keymgmt.pod
+++ b/doc/man7/provider-keymgmt.pod
@@ -69,7 +69,7 @@ For example, the "function" OP_keymgmt_importdomparams() has these:
  typedef void *
      (OSSL_OP_keymgmt_importdomparams_fn)(void *provctx,
                                           const OSSL_PARAM params[]);
- static ossl_inline OSSL_NAME_keymgmt_importdomparams_fn
+ static ossl_inline OSSL_OP_keymgmt_importdomparams_fn
      OSSL_get_OP_keymgmt_importdomparams(const OSSL_DISPATCH *opf);
 
 B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as