doc/man7/provider-signature.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 provider-signature - The signature library E<lt>-E<gt> provider functions

 =head1 SYNOPSIS

 =for openssl multiple includes

  #include <openssl/core_dispatch.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 *OSSL_FUNC_signature_newctx(void *provctx, const char *propq);
  void OSSL_FUNC_signature_freectx(void *ctx);
  void *OSSL_FUNC_signature_dupctx(void *ctx);

  /* Signing */
  int OSSL_FUNC_signature_sign_init(void *ctx, void *provkey,
                                    const OSSL_PARAM params[]);
  int OSSL_FUNC_signature_sign(void *ctx, unsigned char *sig, size_t *siglen,
                               size_t sigsize, const unsigned char *tbs, size_t tbslen);

  /* Verifying */
  int OSSL_FUNC_signature_verify_init(void *ctx, void *provkey,
                                      const OSSL_PARAM params[]);
  int OSSL_FUNC_signature_verify(void *ctx, const unsigned char *sig, size_t siglen,
                                 const unsigned char *tbs, size_t tbslen);

  /* Verify Recover */
  int OSSL_FUNC_signature_verify_recover_init(void *ctx, void *provkey,
                                              const OSSL_PARAM params[]);
  int OSSL_FUNC_signature_verify_recover(void *ctx, unsigned char *rout,
                                         size_t *routlen, size_t routsize,
                                         const unsigned char *sig, size_t siglen);

  /* Digest Sign */
  int OSSL_FUNC_signature_digest_sign_init(void *ctx, const char *mdname,
                                           void *provkey,
                                           const OSSL_PARAM params[]);
  int OSSL_FUNC_signature_digest_sign_update(void *ctx, const unsigned char *data,
                                      size_t datalen);
  int OSSL_FUNC_signature_digest_sign_final(void *ctx, unsigned char *sig,
                                            size_t *siglen, size_t sigsize);
  int OSSL_FUNC_signature_digest_sign(void *ctx,
                               unsigned char *sigret, size_t *siglen,
                               size_t sigsize, const unsigned char *tbs,
                               size_t tbslen);

  /* Digest Verify */
  int OSSL_FUNC_signature_digest_verify_init(void *ctx, const char *mdname,
                                             void *provkey,
                                             const OSSL_PARAM params[]);
  int OSSL_FUNC_signature_digest_verify_update(void *ctx,
                                               const unsigned char *data,
                                               size_t datalen);
  int OSSL_FUNC_signature_digest_verify_final(void *ctx, const unsigned char *sig,
                                       size_t siglen);
  int OSSL_FUNC_signature_digest_verify(void *ctx, const unsigned char *sig,
                                 size_t siglen, const unsigned char *tbs,
                                 size_t tbslen);

  /* Signature parameters */
  int OSSL_FUNC_signature_get_ctx_params(void *ctx, OSSL_PARAM params[]);
  const OSSL_PARAM *OSSL_FUNC_signature_gettable_ctx_params(void *ctx,
                                                            void *provctx);
  int OSSL_FUNC_signature_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
  const OSSL_PARAM *OSSL_FUNC_signature_settable_ctx_params(void *ctx,
                                                            void *provctx);
  /* MD parameters */
  int OSSL_FUNC_signature_get_ctx_md_params(void *ctx, OSSL_PARAM params[]);
  const OSSL_PARAM * OSSL_FUNC_signature_gettable_ctx_md_params(void *ctx);
  int OSSL_FUNC_signature_set_ctx_md_params(void *ctx, const OSSL_PARAM params[]);
  const OSSL_PARAM * OSSL_FUNC_signature_settable_ctx_md_params(void *ctx);

 =head1 DESCRIPTION

 This documentation is primarily aimed at provider authors. See L<provider(7)>
 for further information.

 The signature (OSSL_OP_SIGNATURE) operation enables providers to implement
 signature algorithms and make them available to applications via the API
 functions L<EVP_PKEY_sign(3)>,
 L<EVP_PKEY_verify(3)>,
 and L<EVP_PKEY_verify_recover(3)> (as well
 as 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_FUNC_{name}_fn>, and a helper function to retrieve the
 function pointer from an B<OSSL_DISPATCH> element named
 B<OSSL_FUNC_{name}>.
 For example, the "function" OSSL_FUNC_signature_newctx() has these:

  typedef void *(OSSL_FUNC_signature_newctx_fn)(void *provctx, const char *propq);
  static ossl_inline OSSL_FUNC_signature_newctx_fn
      OSSL_FUNC_signature_newctx(const OSSL_DISPATCH *opf);

 B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
 macros in L<openssl-core_dispatch.h(7)>, as follows:

  OSSL_FUNC_signature_newctx                 OSSL_FUNC_SIGNATURE_NEWCTX
  OSSL_FUNC_signature_freectx                OSSL_FUNC_SIGNATURE_FREECTX
  OSSL_FUNC_signature_dupctx                 OSSL_FUNC_SIGNATURE_DUPCTX

  OSSL_FUNC_signature_sign_init              OSSL_FUNC_SIGNATURE_SIGN_INIT
  OSSL_FUNC_signature_sign                   OSSL_FUNC_SIGNATURE_SIGN

  OSSL_FUNC_signature_verify_init            OSSL_FUNC_SIGNATURE_VERIFY_INIT
  OSSL_FUNC_signature_verify                 OSSL_FUNC_SIGNATURE_VERIFY

  OSSL_FUNC_signature_verify_recover_init    OSSL_FUNC_SIGNATURE_VERIFY_RECOVER_INIT
  OSSL_FUNC_signature_verify_recover         OSSL_FUNC_SIGNATURE_VERIFY_RECOVER

  OSSL_FUNC_signature_digest_sign_init       OSSL_FUNC_SIGNATURE_DIGEST_SIGN_INIT
  OSSL_FUNC_signature_digest_sign_update     OSSL_FUNC_SIGNATURE_DIGEST_SIGN_UPDATE
  OSSL_FUNC_signature_digest_sign_final      OSSL_FUNC_SIGNATURE_DIGEST_SIGN_FINAL
  OSSL_FUNC_signature_digest_sign            OSSL_FUNC_SIGNATURE_DIGEST_SIGN

  OSSL_FUNC_signature_digest_verify_init     OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_INIT
  OSSL_FUNC_signature_digest_verify_update   OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_UPDATE
  OSSL_FUNC_signature_digest_verify_final    OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_FINAL
  OSSL_FUNC_signature_digest_verify          OSSL_FUNC_SIGNATURE_DIGEST_VERIFY

  OSSL_FUNC_signature_get_ctx_params         OSSL_FUNC_SIGNATURE_GET_CTX_PARAMS
  OSSL_FUNC_signature_gettable_ctx_params    OSSL_FUNC_SIGNATURE_GETTABLE_CTX_PARAMS
  OSSL_FUNC_signature_set_ctx_params         OSSL_FUNC_SIGNATURE_SET_CTX_PARAMS
  OSSL_FUNC_signature_settable_ctx_params    OSSL_FUNC_SIGNATURE_SETTABLE_CTX_PARAMS

  OSSL_FUNC_signature_get_ctx_md_params      OSSL_FUNC_SIGNATURE_GET_CTX_MD_PARAMS
  OSSL_FUNC_signature_gettable_ctx_md_params OSSL_FUNC_SIGNATURE_GETTABLE_CTX_MD_PARAMS
  OSSL_FUNC_signature_set_ctx_md_params      OSSL_FUNC_SIGNATURE_SET_CTX_MD_PARAMS
  OSSL_FUNC_signature_settable_ctx_md_params OSSL_FUNC_SIGNATURE_SETTABLE_CTX_MD_PARAMS

 A signature algorithm implementation may not implement all of these functions.
 In order to be a consistent set of functions we must have at least a set of
 context functions (OSSL_FUNC_signature_newctx and OSSL_FUNC_signature_freectx) as well as a
 set of "signature" functions, i.e. at least one of:

 =over 4

 =item OSSL_FUNC_signature_sign_init and OSSL_FUNC_signature_sign

 =item OSSL_FUNC_signature_verify_init and OSSL_FUNC_signature_verify

 =item OSSL_FUNC_signature_verify_recover_init and OSSL_FUNC_signature_verify_init

 =item OSSL_FUNC_signature_digest_sign_init, OSSL_FUNC_signature_digest_sign_update and OSSL_FUNC_signature_digest_sign_final

 =item OSSL_FUNC_signature_digest_verify_init, OSSL_FUNC_signature_digest_verify_update and OSSL_FUNC_signature_digest_verify_final

 =item OSSL_FUNC_signature_digest_sign_init and OSSL_FUNC_signature_digest_sign

 =item OSSL_FUNC_signature_digest_verify_init and OSSL_FUNC_signature_digest_verify

 =back

 OSSL_FUNC_signature_set_ctx_params and OSSL_FUNC_signature_settable_ctx_params are optional,
 but if one of them is present then the other one must also be present. The same
 applies to OSSL_FUNC_signature_get_ctx_params and OSSL_FUNC_signature_gettable_ctx_params, as
 well as the "md_params" functions. The OSSL_FUNC_signature_dupctx function is optional.

 A signature algorithm must also implement some mechanism for generating,
 loading or importing keys via the key management (OSSL_OP_KEYMGMT) operation.
 See L<provider-keymgmt(7)> for further details.

 =head2 Context Management Functions

 OSSL_FUNC_signature_newctx() should create and return a pointer to a provider side
 structure for holding context information during a signature operation.
 A pointer to this context will be passed back in a number of the other signature
 operation function calls.
 The parameter I<provctx> is the provider context generated during provider
 initialisation (see L<provider(7)>). The I<propq> parameter is a property query
 string that may be (optionally) used by the provider during any "fetches" that
 it may perform (if it performs any).

 OSSL_FUNC_signature_freectx() is passed a pointer to the provider side signature
 context in the I<ctx> parameter.
 This function should free any resources associated with that context.

 OSSL_FUNC_signature_dupctx() should duplicate the provider side signature context in
 the I<ctx> parameter and return the duplicate copy.

 =head2 Signing Functions

 OSSL_FUNC_signature_sign_init() initialises a context for signing given a provider side
 signature context in the I<ctx> parameter, and a pointer to a provider key object
 in the I<provkey> parameter.
 The I<params>, if not NULL, should be set on the context in a manner similar to
 using OSSL_FUNC_signature_set_ctx_params().
 The key object should have been previously generated, loaded or imported into
 the provider using the key management (OSSL_OP_KEYMGMT) operation (see
 provider-keymgmt(7)>.

 OSSL_FUNC_signature_sign() performs the actual signing itself.
 A previously initialised signature context is passed in the I<ctx>
 parameter.
 The data to be signed is pointed to be the I<tbs> parameter which is I<tbslen>
 bytes long.
 Unless I<sig> is NULL, the signature should be written to the location pointed
 to by the I<sig> parameter and it should not exceed I<sigsize> bytes in length.
 The length of the signature should be written to I<*siglen>.
 If I<sig> is NULL then the maximum length of the signature should be written to
 I<*siglen>.

 =head2 Verify Functions

 OSSL_FUNC_signature_verify_init() initialises a context for verifying a signature given
 a provider side signature context in the I<ctx> parameter, and a pointer to a
 provider key object in the I<provkey> parameter.
 The I<params>, if not NULL, should be set on the context in a manner similar to
 using OSSL_FUNC_signature_set_ctx_params().
 The key object should have been previously generated, loaded or imported into
 the provider using the key management (OSSL_OP_KEYMGMT) operation (see
 provider-keymgmt(7)>.

 OSSL_FUNC_signature_verify() performs the actual verification itself.
 A previously initialised signature context is passed in the I<ctx> parameter.
 The data that the signature covers is pointed to be the I<tbs> parameter which
 is I<tbslen> bytes long.
 The signature is pointed to by the I<sig> parameter which is I<siglen> bytes
 long.

 =head2 Verify Recover Functions

 OSSL_FUNC_signature_verify_recover_init() initialises a context for recovering the
 signed data given a provider side signature context in the I<ctx> parameter, and
 a pointer to a provider key object in the I<provkey> parameter.
 The I<params>, if not NULL, should be set on the context in a manner similar to
 using OSSL_FUNC_signature_set_ctx_params().
 The key object should have been previously generated, loaded or imported into
 the provider using the key management (OSSL_OP_KEYMGMT) operation (see
 provider-keymgmt(7)>.

 OSSL_FUNC_signature_verify_recover() performs the actual verify recover itself.
 A previously initialised signature context is passed in the I<ctx> parameter.
 The signature is pointed to by the I<sig> parameter which is I<siglen> bytes
 long.
 Unless I<rout> is NULL, the recovered data should be written to the location
 pointed to by I<rout> which should not exceed I<routsize> bytes in length.
 The length of the recovered data should be written to I<*routlen>.
 If I<rout> is NULL then the maximum size of the output buffer is written to
 the I<routlen> parameter.

 =head2 Digest Sign Functions

 OSSL_FUNC_signature_digeset_sign_init() initialises a context for signing given a
 provider side signature context in the I<ctx> parameter, and a pointer to a
 provider key object in the I<provkey> parameter.
 The I<params>, if not NULL, should be set on the context in a manner similar to
 using OSSL_FUNC_signature_set_ctx_params() and
 OSSL_FUNC_signature_set_ctx_md_params().
 The key object should have been
 previously generated, loaded or imported into the provider using the
 key management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.
 The name of the digest to be used will be in the I<mdname> parameter.

 OSSL_FUNC_signature_digest_sign_update() provides data to be signed in the I<data>
 parameter which should be of length I<datalen>. A previously initialised
 signature context is passed in the I<ctx> parameter. This function may be called
 multiple times to cumulatively add data to be signed.

 OSSL_FUNC_signature_digest_sign_final() finalises a signature operation previously
 started through OSSL_FUNC_signature_digest_sign_init() and
 OSSL_FUNC_signature_digest_sign_update() calls. Once finalised no more data will be
 added through OSSL_FUNC_signature_digest_sign_update(). A previously initialised
 signature context is passed in the I<ctx> parameter. Unless I<sig> is NULL, the
 signature should be written to the location pointed to by the I<sig> parameter
 and it should not exceed I<sigsize> bytes in length. The length of the signature
 should be written to I<*siglen>. If I<sig> is NULL then the maximum length of
 the signature should be written to I<*siglen>.

 OSSL_FUNC_signature_digest_sign() implements a "one shot" digest sign operation
 previously started through OSSL_FUNC_signature_digeset_sign_init(). A previously
 initialised signature context is passed in the I<ctx> parameter. The data to be
 signed is in I<tbs> which should be I<tbslen> bytes long. Unless I<sig> is NULL,
 the signature should be written to the location pointed to by the I<sig>
 parameter and it should not exceed I<sigsize> bytes in length. The length of the
 signature should be written to I<*siglen>. If I<sig> is NULL then the maximum
 length of the signature should be written to I<*siglen>.

 =head2 Digest Verify Functions

 OSSL_FUNC_signature_digeset_verify_init() initialises a context for verifying given a
 provider side verification context in the I<ctx> parameter, and a pointer to a
 provider key object in the I<provkey> parameter.
 The I<params>, if not NULL, should be set on the context in a manner similar to
 OSSL_FUNC_signature_set_ctx_params() and
 OSSL_FUNC_signature_set_ctx_md_params().
 The key object should have been
 previously generated, loaded or imported into the provider using the
 key management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.
 The name of the digest to be used will be in the I<mdname> parameter.

 OSSL_FUNC_signature_digest_verify_update() provides data to be verified in the I<data>
 parameter which should be of length I<datalen>. A previously initialised
 verification context is passed in the I<ctx> parameter. This function may be
 called multiple times to cumulatively add data to be verified.

 OSSL_FUNC_signature_digest_verify_final() finalises a verification operation previously
 started through OSSL_FUNC_signature_digest_verify_init() and
 OSSL_FUNC_signature_digest_verify_update() calls. Once finalised no more data will be
 added through OSSL_FUNC_signature_digest_verify_update(). A previously initialised
 verification context is passed in the I<ctx> parameter. The signature to be
 verified is in I<sig> which is I<siglen> bytes long.

 OSSL_FUNC_signature_digest_verify() implements a "one shot" digest verify operation
 previously started through OSSL_FUNC_signature_digeset_verify_init(). A previously
 initialised verification context is passed in the I<ctx> parameter. The data to be
 verified is in I<tbs> which should be I<tbslen> bytes long. The signature to be
 verified is in I<sig> which is I<siglen> bytes long.

 =head2 Signature parameters

 See L<OSSL_PARAM(3)> for further details on the parameters structure used by
 the OSSL_FUNC_signature_get_ctx_params() and OSSL_FUNC_signature_set_ctx_params() functions.

 OSSL_FUNC_signature_get_ctx_params() gets signature parameters associated with the
 given provider side signature context I<ctx> and stored them in I<params>.
 Passing NULL for I<params> should return true.

 OSSL_FUNC_signature_set_ctx_params() sets the signature parameters associated with the
 given provider side signature context I<ctx> to I<params>.
 Any parameter settings are additional to any that were previously set.
 Passing NULL for I<params> should return true.

 Common parameters currently recognised by built-in signature algorithms are as
 follows.

 =over 4

 =item "digest" (B<OSSL_SIGNATURE_PARAM_DIGEST>) <UTF8 string>

 Get or sets the name of the digest algorithm used for the input to the
 signature functions. It is required in order to calculate the "algorithm-id".

 =item "properties" (B<OSSL_SIGNATURE_PARAM_PROPERTIES>) <UTF8 string>

 Sets the name of the property query associated with the "digest" algorithm.
 NULL is used if this optional value is not set.

 =item "digest-size" (B<OSSL_SIGNATURE_PARAM_DIGEST_SIZE>) <unsigned integer>

 Gets or sets the output size of the digest algorithm used for the input to the
 signature functions.
 The length of the "digest-size" parameter should not exceed that of a B<size_t>.

 =item "algorithm-id" (B<OSSL_SIGNATURE_PARAM_ALGORITHM_ID>) <octet string>

 Gets the DER encoded AlgorithmIdentifier that corresponds to the combination of
 signature algorithm and digest algorithm for the signature operation.

 =item "kat" (B<OSSL_SIGNATURE_PARAM_KAT>) <unsigned integer>

 Sets a flag to modify the sign operation to return an error if the initial
 calculated signature is invalid.
 In the normal mode of operation - new random values are chosen until the
 signature operation succeeds.
 By default it retries until a signature is calculated.
 Setting the value to 0 causes the sign operation to retry,
 otherwise the sign operation is only tried once and returns whether or not it
 was successful.
 Known answer tests can be performed if the random generator is overridden to
 supply known values that either pass or fail.

 =back

 OSSL_FUNC_signature_gettable_ctx_params() and OSSL_FUNC_signature_settable_ctx_params() get a
 constant B<OSSL_PARAM> array that describes the gettable and settable parameters,
 i.e. parameters that can be used with OSSL_FUNC_signature_get_ctx_params() and
 OSSL_FUNC_signature_set_ctx_params() respectively.
 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.

 =head2 MD parameters

 See L<OSSL_PARAM(3)> for further details on the parameters structure used by
 the OSSL_FUNC_signature_get_md_ctx_params() and OSSL_FUNC_signature_set_md_ctx_params()
 functions.

 OSSL_FUNC_signature_get_md_ctx_params() gets digest parameters associated with the
 given provider side digest signature context I<ctx> and stores them in I<params>.
 Passing NULL for I<params> should return true.

 OSSL_FUNC_signature_set_ms_ctx_params() sets the digest parameters associated with the
 given provider side digest signature context I<ctx> to I<params>.
 Any parameter settings are additional to any that were previously set.
 Passing NULL for I<params> should return true.

 Parameters currently recognised by built-in signature algorithms are the same
 as those for built-in digest algorithms. See
 L<provider-digest(7)/Digest Parameters> for further information.

 OSSL_FUNC_signature_gettable_md_ctx_params() and OSSL_FUNC_signature_settable_md_ctx_params()
 get a constant B<OSSL_PARAM> array that describes the gettable and settable
 digest parameters, i.e. parameters that can be used with
 OSSL_FUNC_signature_get_md_ctx_params() and OSSL_FUNC_signature_set_md_ctx_params()
 respectively. See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter
 descriptor.

 =head1 RETURN VALUES

 OSSL_FUNC_signature_newctx() and OSSL_FUNC_signature_dupctx() should return the newly created
 provider side signature, or NULL on failure.

 OSSL_FUNC_signature_gettable_ctx_params(), OSSL_FUNC_signature_settable_ctx_params(),
 OSSL_FUNC_signature_gettable_md_ctx_params() and OSSL_FUNC_signature_settable_md_ctx_params(),
 return the gettable or settable parameters in a constant B<OSSL_PARAM> array.

 All other functions should return 1 for success or 0 on error.

 =head1 SEE ALSO

 L<provider(7)>

 =head1 HISTORY

 The provider SIGNATURE interface was introduced in OpenSSL 3.0.

 =head1 COPYRIGHT

 Copyright 2019-2022 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
	=pod

	=head1 NAME

	provider-signature - The signature library E<lt>-E<gt> provider functions

	=head1 SYNOPSIS

	=for openssl multiple includes

	#include <openssl/core_dispatch.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 OSSL_FUNC_signature_newctx(void provctx, const char *propq);
	void OSSL_FUNC_signature_freectx(void *ctx);
	void OSSL_FUNC_signature_dupctx(void ctx);

	/* Signing */
	int OSSL_FUNC_signature_sign_init(void ctx, void provkey,
	const OSSL_PARAM params[]);
	int OSSL_FUNC_signature_sign(void ctx, unsigned char sig, size_t *siglen,
	size_t sigsize, const unsigned char *tbs, size_t tbslen);

	/* Verifying */
	int OSSL_FUNC_signature_verify_init(void ctx, void provkey,
	const OSSL_PARAM params[]);
	int OSSL_FUNC_signature_verify(void ctx, const unsigned char sig, size_t siglen,
	const unsigned char *tbs, size_t tbslen);

	/* Verify Recover */
	int OSSL_FUNC_signature_verify_recover_init(void ctx, void provkey,
	const OSSL_PARAM params[]);
	int OSSL_FUNC_signature_verify_recover(void ctx, unsigned char rout,
	size_t *routlen, size_t routsize,
	const unsigned char *sig, size_t siglen);

	/* Digest Sign */
	int OSSL_FUNC_signature_digest_sign_init(void ctx, const char mdname,
	void *provkey,
	const OSSL_PARAM params[]);
	int OSSL_FUNC_signature_digest_sign_update(void ctx, const unsigned char data,
	size_t datalen);
	int OSSL_FUNC_signature_digest_sign_final(void ctx, unsigned char sig,
	size_t *siglen, size_t sigsize);
	int OSSL_FUNC_signature_digest_sign(void *ctx,
	unsigned char sigret, size_t siglen,
	size_t sigsize, const unsigned char *tbs,
	size_t tbslen);

	/* Digest Verify */
	int OSSL_FUNC_signature_digest_verify_init(void ctx, const char mdname,
	void *provkey,
	const OSSL_PARAM params[]);
	int OSSL_FUNC_signature_digest_verify_update(void *ctx,
	const unsigned char *data,
	size_t datalen);
	int OSSL_FUNC_signature_digest_verify_final(void ctx, const unsigned char sig,
	size_t siglen);
	int OSSL_FUNC_signature_digest_verify(void ctx, const unsigned char sig,
	size_t siglen, const unsigned char *tbs,
	size_t tbslen);

	/* Signature parameters */
	int OSSL_FUNC_signature_get_ctx_params(void *ctx, OSSL_PARAM params[]);
	const OSSL_PARAM OSSL_FUNC_signature_gettable_ctx_params(void ctx,
	void *provctx);
	int OSSL_FUNC_signature_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
	const OSSL_PARAM OSSL_FUNC_signature_settable_ctx_params(void ctx,
	void *provctx);
	/* MD parameters */
	int OSSL_FUNC_signature_get_ctx_md_params(void *ctx, OSSL_PARAM params[]);
	const OSSL_PARAM * OSSL_FUNC_signature_gettable_ctx_md_params(void *ctx);
	int OSSL_FUNC_signature_set_ctx_md_params(void *ctx, const OSSL_PARAM params[]);
	const OSSL_PARAM * OSSL_FUNC_signature_settable_ctx_md_params(void *ctx);

	=head1 DESCRIPTION

	This documentation is primarily aimed at provider authors. See L<provider(7)>
	for further information.

	The signature (OSSL_OP_SIGNATURE) operation enables providers to implement
	signature algorithms and make them available to applications via the API
	functions L<EVP_PKEY_sign(3)>,
	L<EVP_PKEY_verify(3)>,
	and L<EVP_PKEY_verify_recover(3)> (as well
	as 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_FUNC_{name}_fn>, and a helper function to retrieve the
	function pointer from an B<OSSL_DISPATCH> element named
	B<OSSL_FUNC_{name}>.
	For example, the "function" OSSL_FUNC_signature_newctx() has these:

	typedef void (OSSL_FUNC_signature_newctx_fn)(void provctx, const char *propq);
	static ossl_inline OSSL_FUNC_signature_newctx_fn
	OSSL_FUNC_signature_newctx(const OSSL_DISPATCH *opf);

	B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
	macros in L<openssl-core_dispatch.h(7)>, as follows:

	OSSL_FUNC_signature_newctx OSSL_FUNC_SIGNATURE_NEWCTX
	OSSL_FUNC_signature_freectx OSSL_FUNC_SIGNATURE_FREECTX
	OSSL_FUNC_signature_dupctx OSSL_FUNC_SIGNATURE_DUPCTX

	OSSL_FUNC_signature_sign_init OSSL_FUNC_SIGNATURE_SIGN_INIT
	OSSL_FUNC_signature_sign OSSL_FUNC_SIGNATURE_SIGN

	OSSL_FUNC_signature_verify_init OSSL_FUNC_SIGNATURE_VERIFY_INIT
	OSSL_FUNC_signature_verify OSSL_FUNC_SIGNATURE_VERIFY

	OSSL_FUNC_signature_verify_recover_init OSSL_FUNC_SIGNATURE_VERIFY_RECOVER_INIT
	OSSL_FUNC_signature_verify_recover OSSL_FUNC_SIGNATURE_VERIFY_RECOVER

	OSSL_FUNC_signature_digest_sign_init OSSL_FUNC_SIGNATURE_DIGEST_SIGN_INIT
	OSSL_FUNC_signature_digest_sign_update OSSL_FUNC_SIGNATURE_DIGEST_SIGN_UPDATE
	OSSL_FUNC_signature_digest_sign_final OSSL_FUNC_SIGNATURE_DIGEST_SIGN_FINAL
	OSSL_FUNC_signature_digest_sign OSSL_FUNC_SIGNATURE_DIGEST_SIGN

	OSSL_FUNC_signature_digest_verify_init OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_INIT
	OSSL_FUNC_signature_digest_verify_update OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_UPDATE
	OSSL_FUNC_signature_digest_verify_final OSSL_FUNC_SIGNATURE_DIGEST_VERIFY_FINAL
	OSSL_FUNC_signature_digest_verify OSSL_FUNC_SIGNATURE_DIGEST_VERIFY

	OSSL_FUNC_signature_get_ctx_params OSSL_FUNC_SIGNATURE_GET_CTX_PARAMS
	OSSL_FUNC_signature_gettable_ctx_params OSSL_FUNC_SIGNATURE_GETTABLE_CTX_PARAMS
	OSSL_FUNC_signature_set_ctx_params OSSL_FUNC_SIGNATURE_SET_CTX_PARAMS
	OSSL_FUNC_signature_settable_ctx_params OSSL_FUNC_SIGNATURE_SETTABLE_CTX_PARAMS

	OSSL_FUNC_signature_get_ctx_md_params OSSL_FUNC_SIGNATURE_GET_CTX_MD_PARAMS
	OSSL_FUNC_signature_gettable_ctx_md_params OSSL_FUNC_SIGNATURE_GETTABLE_CTX_MD_PARAMS
	OSSL_FUNC_signature_set_ctx_md_params OSSL_FUNC_SIGNATURE_SET_CTX_MD_PARAMS
	OSSL_FUNC_signature_settable_ctx_md_params OSSL_FUNC_SIGNATURE_SETTABLE_CTX_MD_PARAMS

	A signature algorithm implementation may not implement all of these functions.
	In order to be a consistent set of functions we must have at least a set of
	context functions (OSSL_FUNC_signature_newctx and OSSL_FUNC_signature_freectx) as well as a
	set of "signature" functions, i.e. at least one of:

	=over 4

	=item OSSL_FUNC_signature_sign_init and OSSL_FUNC_signature_sign

	=item OSSL_FUNC_signature_verify_init and OSSL_FUNC_signature_verify

	=item OSSL_FUNC_signature_verify_recover_init and OSSL_FUNC_signature_verify_init

	=item OSSL_FUNC_signature_digest_sign_init, OSSL_FUNC_signature_digest_sign_update and OSSL_FUNC_signature_digest_sign_final

	=item OSSL_FUNC_signature_digest_verify_init, OSSL_FUNC_signature_digest_verify_update and OSSL_FUNC_signature_digest_verify_final

	=item OSSL_FUNC_signature_digest_sign_init and OSSL_FUNC_signature_digest_sign

	=item OSSL_FUNC_signature_digest_verify_init and OSSL_FUNC_signature_digest_verify

	=back

	OSSL_FUNC_signature_set_ctx_params and OSSL_FUNC_signature_settable_ctx_params are optional,
	but if one of them is present then the other one must also be present. The same
	applies to OSSL_FUNC_signature_get_ctx_params and OSSL_FUNC_signature_gettable_ctx_params, as
	well as the "md_params" functions. The OSSL_FUNC_signature_dupctx function is optional.

	A signature algorithm must also implement some mechanism for generating,
	loading or importing keys via the key management (OSSL_OP_KEYMGMT) operation.
	See L<provider-keymgmt(7)> for further details.

	=head2 Context Management Functions

	OSSL_FUNC_signature_newctx() should create and return a pointer to a provider side
	structure for holding context information during a signature operation.
	A pointer to this context will be passed back in a number of the other signature
	operation function calls.
	The parameter I<provctx> is the provider context generated during provider
	initialisation (see L<provider(7)>). The I<propq> parameter is a property query
	string that may be (optionally) used by the provider during any "fetches" that
	it may perform (if it performs any).

	OSSL_FUNC_signature_freectx() is passed a pointer to the provider side signature
	context in the I<ctx> parameter.
	This function should free any resources associated with that context.

	OSSL_FUNC_signature_dupctx() should duplicate the provider side signature context in
	the I<ctx> parameter and return the duplicate copy.

	=head2 Signing Functions

	OSSL_FUNC_signature_sign_init() initialises a context for signing given a provider side
	signature context in the I<ctx> parameter, and a pointer to a provider key object
	in the I<provkey> parameter.
	The I<params>, if not NULL, should be set on the context in a manner similar to
	using OSSL_FUNC_signature_set_ctx_params().
	The key object should have been previously generated, loaded or imported into
	the provider using the key management (OSSL_OP_KEYMGMT) operation (see
	provider-keymgmt(7)>.

	OSSL_FUNC_signature_sign() performs the actual signing itself.
	A previously initialised signature context is passed in the I<ctx>
	parameter.
	The data to be signed is pointed to be the I<tbs> parameter which is I<tbslen>
	bytes long.
	Unless I<sig> is NULL, the signature should be written to the location pointed
	to by the I<sig> parameter and it should not exceed I<sigsize> bytes in length.
	The length of the signature should be written to I<*siglen>.
	If I<sig> is NULL then the maximum length of the signature should be written to
	I<*siglen>.

	=head2 Verify Functions

	OSSL_FUNC_signature_verify_init() initialises a context for verifying a signature given
	a provider side signature context in the I<ctx> parameter, and a pointer to a
	provider key object in the I<provkey> parameter.
	The I<params>, if not NULL, should be set on the context in a manner similar to
	using OSSL_FUNC_signature_set_ctx_params().
	The key object should have been previously generated, loaded or imported into
	the provider using the key management (OSSL_OP_KEYMGMT) operation (see
	provider-keymgmt(7)>.

	OSSL_FUNC_signature_verify() performs the actual verification itself.
	A previously initialised signature context is passed in the I<ctx> parameter.
	The data that the signature covers is pointed to be the I<tbs> parameter which
	is I<tbslen> bytes long.
	The signature is pointed to by the I<sig> parameter which is I<siglen> bytes
	long.

	=head2 Verify Recover Functions

	OSSL_FUNC_signature_verify_recover_init() initialises a context for recovering the
	signed data given a provider side signature context in the I<ctx> parameter, and
	a pointer to a provider key object in the I<provkey> parameter.
	The I<params>, if not NULL, should be set on the context in a manner similar to
	using OSSL_FUNC_signature_set_ctx_params().
	The key object should have been previously generated, loaded or imported into
	the provider using the key management (OSSL_OP_KEYMGMT) operation (see
	provider-keymgmt(7)>.

	OSSL_FUNC_signature_verify_recover() performs the actual verify recover itself.
	A previously initialised signature context is passed in the I<ctx> parameter.
	The signature is pointed to by the I<sig> parameter which is I<siglen> bytes
	long.
	Unless I<rout> is NULL, the recovered data should be written to the location
	pointed to by I<rout> which should not exceed I<routsize> bytes in length.
	The length of the recovered data should be written to I<*routlen>.
	If I<rout> is NULL then the maximum size of the output buffer is written to
	the I<routlen> parameter.

	=head2 Digest Sign Functions

	OSSL_FUNC_signature_digeset_sign_init() initialises a context for signing given a
	provider side signature context in the I<ctx> parameter, and a pointer to a
	provider key object in the I<provkey> parameter.
	The I<params>, if not NULL, should be set on the context in a manner similar to
	using OSSL_FUNC_signature_set_ctx_params() and
	OSSL_FUNC_signature_set_ctx_md_params().
	The key object should have been
	previously generated, loaded or imported into the provider using the
	key management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.
	The name of the digest to be used will be in the I<mdname> parameter.

	OSSL_FUNC_signature_digest_sign_update() provides data to be signed in the I<data>
	parameter which should be of length I<datalen>. A previously initialised
	signature context is passed in the I<ctx> parameter. This function may be called
	multiple times to cumulatively add data to be signed.

	OSSL_FUNC_signature_digest_sign_final() finalises a signature operation previously
	started through OSSL_FUNC_signature_digest_sign_init() and
	OSSL_FUNC_signature_digest_sign_update() calls. Once finalised no more data will be
	added through OSSL_FUNC_signature_digest_sign_update(). A previously initialised
	signature context is passed in the I<ctx> parameter. Unless I<sig> is NULL, the
	signature should be written to the location pointed to by the I<sig> parameter
	and it should not exceed I<sigsize> bytes in length. The length of the signature
	should be written to I<*siglen>. If I<sig> is NULL then the maximum length of
	the signature should be written to I<*siglen>.

	OSSL_FUNC_signature_digest_sign() implements a "one shot" digest sign operation
	previously started through OSSL_FUNC_signature_digeset_sign_init(). A previously
	initialised signature context is passed in the I<ctx> parameter. The data to be
	signed is in I<tbs> which should be I<tbslen> bytes long. Unless I<sig> is NULL,
	the signature should be written to the location pointed to by the I<sig>
	parameter and it should not exceed I<sigsize> bytes in length. The length of the
	signature should be written to I<*siglen>. If I<sig> is NULL then the maximum
	length of the signature should be written to I<*siglen>.

	=head2 Digest Verify Functions

	OSSL_FUNC_signature_digeset_verify_init() initialises a context for verifying given a
	provider side verification context in the I<ctx> parameter, and a pointer to a
	provider key object in the I<provkey> parameter.
	The I<params>, if not NULL, should be set on the context in a manner similar to
	OSSL_FUNC_signature_set_ctx_params() and
	OSSL_FUNC_signature_set_ctx_md_params().
	The key object should have been
	previously generated, loaded or imported into the provider using the
	key management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.
	The name of the digest to be used will be in the I<mdname> parameter.

	OSSL_FUNC_signature_digest_verify_update() provides data to be verified in the I<data>
	parameter which should be of length I<datalen>. A previously initialised
	verification context is passed in the I<ctx> parameter. This function may be
	called multiple times to cumulatively add data to be verified.

	OSSL_FUNC_signature_digest_verify_final() finalises a verification operation previously
	started through OSSL_FUNC_signature_digest_verify_init() and
	OSSL_FUNC_signature_digest_verify_update() calls. Once finalised no more data will be
	added through OSSL_FUNC_signature_digest_verify_update(). A previously initialised
	verification context is passed in the I<ctx> parameter. The signature to be
	verified is in I<sig> which is I<siglen> bytes long.

	OSSL_FUNC_signature_digest_verify() implements a "one shot" digest verify operation
	previously started through OSSL_FUNC_signature_digeset_verify_init(). A previously
	initialised verification context is passed in the I<ctx> parameter. The data to be
	verified is in I<tbs> which should be I<tbslen> bytes long. The signature to be
	verified is in I<sig> which is I<siglen> bytes long.

	=head2 Signature parameters

	See L<OSSL_PARAM(3)> for further details on the parameters structure used by
	the OSSL_FUNC_signature_get_ctx_params() and OSSL_FUNC_signature_set_ctx_params() functions.

	OSSL_FUNC_signature_get_ctx_params() gets signature parameters associated with the
	given provider side signature context I<ctx> and stored them in I<params>.
	Passing NULL for I<params> should return true.

	OSSL_FUNC_signature_set_ctx_params() sets the signature parameters associated with the
	given provider side signature context I<ctx> to I<params>.
	Any parameter settings are additional to any that were previously set.
	Passing NULL for I<params> should return true.

	Common parameters currently recognised by built-in signature algorithms are as
	follows.

	=over 4

	=item "digest" (B<OSSL_SIGNATURE_PARAM_DIGEST>) <UTF8 string>

	Get or sets the name of the digest algorithm used for the input to the
	signature functions. It is required in order to calculate the "algorithm-id".

	=item "properties" (B<OSSL_SIGNATURE_PARAM_PROPERTIES>) <UTF8 string>

	Sets the name of the property query associated with the "digest" algorithm.
	NULL is used if this optional value is not set.

	=item "digest-size" (B<OSSL_SIGNATURE_PARAM_DIGEST_SIZE>) <unsigned integer>

	Gets or sets the output size of the digest algorithm used for the input to the
	signature functions.
	The length of the "digest-size" parameter should not exceed that of a B<size_t>.

	=item "algorithm-id" (B<OSSL_SIGNATURE_PARAM_ALGORITHM_ID>) <octet string>

	Gets the DER encoded AlgorithmIdentifier that corresponds to the combination of
	signature algorithm and digest algorithm for the signature operation.

	=item "kat" (B<OSSL_SIGNATURE_PARAM_KAT>) <unsigned integer>

	Sets a flag to modify the sign operation to return an error if the initial
	calculated signature is invalid.
	In the normal mode of operation - new random values are chosen until the
	signature operation succeeds.
	By default it retries until a signature is calculated.
	Setting the value to 0 causes the sign operation to retry,
	otherwise the sign operation is only tried once and returns whether or not it
	was successful.
	Known answer tests can be performed if the random generator is overridden to
	supply known values that either pass or fail.

	=back

	OSSL_FUNC_signature_gettable_ctx_params() and OSSL_FUNC_signature_settable_ctx_params() get a
	constant B<OSSL_PARAM> array that describes the gettable and settable parameters,
	i.e. parameters that can be used with OSSL_FUNC_signature_get_ctx_params() and
	OSSL_FUNC_signature_set_ctx_params() respectively.
	See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.

	=head2 MD parameters

	See L<OSSL_PARAM(3)> for further details on the parameters structure used by
	the OSSL_FUNC_signature_get_md_ctx_params() and OSSL_FUNC_signature_set_md_ctx_params()
	functions.

	OSSL_FUNC_signature_get_md_ctx_params() gets digest parameters associated with the
	given provider side digest signature context I<ctx> and stores them in I<params>.
	Passing NULL for I<params> should return true.

	OSSL_FUNC_signature_set_ms_ctx_params() sets the digest parameters associated with the
	given provider side digest signature context I<ctx> to I<params>.
	Any parameter settings are additional to any that were previously set.
	Passing NULL for I<params> should return true.

	Parameters currently recognised by built-in signature algorithms are the same
	as those for built-in digest algorithms. See
	L<provider-digest(7)/Digest Parameters> for further information.

	OSSL_FUNC_signature_gettable_md_ctx_params() and OSSL_FUNC_signature_settable_md_ctx_params()
	get a constant B<OSSL_PARAM> array that describes the gettable and settable
	digest parameters, i.e. parameters that can be used with
	OSSL_FUNC_signature_get_md_ctx_params() and OSSL_FUNC_signature_set_md_ctx_params()
	respectively. See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter
	descriptor.

	=head1 RETURN VALUES

	OSSL_FUNC_signature_newctx() and OSSL_FUNC_signature_dupctx() should return the newly created
	provider side signature, or NULL on failure.

	OSSL_FUNC_signature_gettable_ctx_params(), OSSL_FUNC_signature_settable_ctx_params(),
	OSSL_FUNC_signature_gettable_md_ctx_params() and OSSL_FUNC_signature_settable_md_ctx_params(),
	return the gettable or settable parameters in a constant B<OSSL_PARAM> array.

	All other functions should return 1 for success or 0 on error.

	=head1 SEE ALSO

	L<provider(7)>

	=head1 HISTORY

	The provider SIGNATURE interface was introduced in OpenSSL 3.0.

	=head1 COPYRIGHT

	Copyright 2019-2022 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