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       provider-base - The basic OpenSSL library <-> provider functions

	#include <openssl/core_dispatch.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.

	/* Functions offered by	libcrypto to the providers */
	const OSSL_ITEM	*core_gettable_params(const OSSL_CORE_HANDLE *handle);
	int core_get_params(const OSSL_CORE_HANDLE *handle, OSSL_PARAM params[]);
	int core_thread_start(const OSSL_CORE_HANDLE *handle,
			      OSSL_thread_stop_handler_fn handfn);
	OPENSSL_CORE_CTX *core_get_library_context(const OSSL_CORE_HANDLE *handle);
	void core_new_error(const OSSL_CORE_HANDLE *handle);
	void core_set_error_debug(const	OSSL_CORE_HANDLE *handle,
				  const	char *file, int	line, const char *func);
	void core_vset_error(const OSSL_CORE_HANDLE *handle,
			     uint32_t reason, const char *fmt, va_list args);

	 * Some	OpenSSL	functionality is directly offered to providers via
	 * dispatch
	void *CRYPTO_malloc(size_t num,	const char *file, int line);
	void *CRYPTO_zalloc(size_t num,	const char *file, int line);
	void *CRYPTO_memdup(const void *str, size_t siz,
			    const char *file, int line);
	char *CRYPTO_strdup(const char *str, const char	*file, int line);
	char *CRYPTO_strndup(const char	*str, size_t s,
			     const char	*file, int line);
	void CRYPTO_free(void *ptr, const char *file, int line);
	void CRYPTO_clear_free(void *ptr, size_t num,
			       const char *file, int line);
	void *CRYPTO_realloc(void *addr, size_t	num,
			     const char	*file, int line);
	void *CRYPTO_clear_realloc(void	*addr, size_t old_num, size_t num,
				   const char *file, int line);
	void *CRYPTO_secure_malloc(size_t num, const char *file, int line);
	void *CRYPTO_secure_zalloc(size_t num, const char *file, int line);
	void CRYPTO_secure_free(void *ptr, const char *file, int line);
	void CRYPTO_secure_clear_free(void *ptr, size_t	num,
				      const char *file,	int line);
	int CRYPTO_secure_allocated(const void *ptr);
	void OPENSSL_cleanse(void *ptr,	size_t len);

	OSSL_CORE_BIO *	BIO_new_file(const char	*filename, const char *mode)
	OSSL_CORE_BIO *	BIO_new_membuf(const void *buf,	int len)
	int BIO_read_ex(OSSL_CORE_BIO *bio, void *data,	size_t data_len,
			size_t *bytes_read))
	int BIO_write_ex(OSSL_CORE_BIO *bio, const void	*data, size_t data_len,
			 size_t	*written)
	int BIO_free(OSSL_CORE_BIO *bio))
	int BIO_vprintf(OSSL_CORE_BIO *bio, const char *format,	va_list	args)
	int BIO_vsnprintf(char *buf, size_t n, const char *fmt,	va_list	args)

	void self_test_cb(OPENSSL_CORE_CTX *ctx, OSSL_CALLBACK **cb, void **cbarg)

	/* Functions offered by	the provider to	libcrypto */
	void provider_teardown(void *provctx);
	const OSSL_ITEM	*provider_gettable_params(void *provctx);
	int provider_get_params(void *provctx, OSSL_PARAM params[]);
	const OSSL_ALGORITHM *provider_query_operation(void *provctx,
						       int operation_id,
						       const int *no_store);
	const OSSL_ITEM	*provider_get_reason_strings(void *provctx);
	int provider_get_capabilities(void *provctx, const char	*capability,
				      OSSL_CALLBACK *cb, void *arg);

       All "functions" mentioned here are passed as function pointers between
       libcrypto and the provider in OSSL_DISPATCH arrays, in the call of the
       provider	initialization function.  See "Provider" in provider(7)	for a
       description of the initialization function.

       All these "functions" have a corresponding function type	definition
       named OSSL_{name}_fn, and a helper function to retrieve the function
       pointer from a OSSL_DISPATCH element named OSSL_FUNC_{name}.  For
       example,	the "function" core_gettable_params() has these:

	typedef	OSSL_PARAM *
	    (OSSL_FUNC_core_gettable_params_fn)(const OSSL_CORE_HANDLE *handle);
	static ossl_inline OSSL_NAME_core_gettable_params_fn
	    OSSL_FUNC_core_gettable_params(const OSSL_DISPATCH *opf);

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

       For in (the OSSL_DISPATCH array passed from libcrypto to	the provider):

	core_gettable_params	       OSSL_FUNC_CORE_GETTABLE_PARAMS
	core_get_params		       OSSL_FUNC_CORE_GET_PARAMS
	core_thread_start	       OSSL_FUNC_CORE_THREAD_START
	core_get_library_context       OSSL_FUNC_CORE_GET_LIBRARY_CONTEXT
	core_new_error		       OSSL_FUNC_CORE_NEW_ERROR
	core_set_error_debug	       OSSL_FUNC_CORE_SET_ERROR_DEBUG
	core_set_error		       OSSL_FUNC_CORE_SET_ERROR
	BIO_new_file		       OSSL_FUNC_BIO_NEW_FILE
	BIO_new_mem_buf		       OSSL_FUNC_BIO_NEW_MEMBUF
	BIO_read_ex		       OSSL_FUNC_BIO_READ_EX
	BIO_free		       OSSL_FUNC_BIO_FREE
	BIO_vprintf		       OSSL_FUNC_BIO_VPRINTF

       For *out	(the OSSL_DISPATCH array passed	from the provider to

	provider_teardown	       OSSL_FUNC_PROVIDER_TEARDOWN
	provider_gettable_params       OSSL_FUNC_PROVIDER_GETTABLE_PARAMS
	provider_get_params	       OSSL_FUNC_PROVIDER_GET_PARAMS
	provider_query_operation       OSSL_FUNC_PROVIDER_QUERY_OPERATION
	provider_get_reason_strings    OSSL_FUNC_PROVIDER_GET_REASON_STRINGS
	provider_get_capabilities      OSSL_FUNC_PROVIDER_GET_CAPABILITIES

   Core	functions
       core_gettable_params() returns a	constant array of descriptor
       OSSL_PARAM, for parameters that core_get_params() can handle.

       core_get_params() retrieves parameters from the core for	the given
       handle.	See "Core parameters" below for	a description of currently
       known parameters.

       core_get_library_context() retrieves the	library	context	in which the
       library object for the current provider is stored, accessible through
       the handle.  This may sometimes be useful if the	provider wishes	to
       store a reference to its	context	in the same library context.

       core_new_error(), core_set_error_debug()	and core_set_error() are
       building	blocks for reporting an	error back to the core,	with reference
       to the handle.

	   allocates a new thread specific error record.

	   This	corresponds to the OpenSSL function ERR_new(3).

	   sets	debugging information in the current thread specific error
	   record.  The	debugging information includes the name	of the file
	   file, the line line and the function	name func where	the error

	   This	corresponds to the OpenSSL function ERR_set_debug(3).

	   sets	the reason for the error, along	with any addition data.	 The
	   reason is a number defined by the provider and used to index	the
	   reason strings table	that's returned	by
	   provider_get_reason_strings().  The additional data is given	as a
	   format string fmt and a set of arguments args, which	are treated in
	   the same manner as with BIO_vsnprintf().  file and line may also be
	   passed to indicate exactly where the	error occurred or was

	   This	corresponds to the OpenSSL function ERR_vset_error(3).

       CRYPTO_malloc(),	CRYPTO_zalloc(), CRYPTO_memdup(), CRYPTO_strdup(),
       CRYPTO_strndup(), CRYPTO_free(),	CRYPTO_clear_free(), CRYPTO_realloc(),
       CRYPTO_clear_realloc(), CRYPTO_secure_malloc(), CRYPTO_secure_zalloc(),
       CRYPTO_secure_free(), CRYPTO_secure_clear_free(),
       CRYPTO_secure_allocated(), BIO_new_file(), BIO_new_mem_buf(),
       BIO_read_ex(), BIO_free(), BIO_vprintf(), OPENSSL_cleanse(), and
       OPENSSL_hexstr2buf() correspond exactly to the public functions with
       the same	name.  As a matter of fact, the	pointers in the	OSSL_DISPATCH
       array are direct	pointers to those public functions. Note that the BIO
       functions take an OSSL_CORE_BIO type rather than	the standard BIO type.
       This is to ensure that a	provider does not mix BIOs from	the core with
       BIOs used on the	provider side (the two are not compatible).
       OSSL_SELF_TEST_set_callback() is	used to	set an optional	callback that
       can be passed into a provider. This may be ignored by a provider.

   Provider functions
       provider_teardown() is called when a provider is	shut down and removed
       from the	core's provider	store.	It must	free the passed	provctx.

       provider_gettable_params() should return	a constant array of descriptor
       OSSL_PARAM, for parameters that provider_get_params() can handle.

       provider_get_params() should process the	OSSL_PARAM array params,
       setting the values of the parameters it understands.

       provider_query_operation() should return	a constant OSSL_ALGORITHM that
       corresponds to the given	operation_id.  It should indicate if the core
       may store a reference to	this array by setting *no_store	to 0 (core may
       store a reference) or 1 (core may not store a reference).

       provider_get_reason_strings() should return a constant OSSL_ITEM	array
       that provides reason strings for	reason codes the provider may use when
       reporting errors	using core_put_error().

       The provider_get_capabilities() function	should call the	callback cb
       passing it a set	of OSSL_PARAMs and the caller supplied argument	arg.
       The OSSL_PARAMs should provide details about the	capability with	the
       name given in the capability argument relevant for the provider context
       provctx.	If a provider supports multiple	capabilities with the given
       name then it may	call the callback multiple times (one for each
       capability). Capabilities can be	useful for describing the services
       that a provider can offer. For further details see the "CAPABILITIES"
       section below. It should	return 1 on success or 0 on error.

       None of these functions are mandatory, but a provider is	fairly useless
       without at least	provider_query_operation(), and
       provider_gettable_params() is fairly useless if not accompanied by

   Provider parameters
       provider_get_params() can return	the following provider parameters to
       the core:

       "name" (OSSL_PROV_PARAM_NAME) <UTF8_ptr>
	   This	points to a string that	should give a unique name for the

       "version" (OSSL_PROV_PARAM_VERSION) <UTF8_ptr>
	   This	points to a string that	is a version number associated with
	   this	provider.  OpenSSL in-built providers use OPENSSL_VERSION_STR,
	   but this may	be different for any third party provider. This	string
	   is for informational	purposes only.

       "buildinfo" (OSSL_PROV_PARAM_BUILDINFO) <UTF8_ptr>
	   This	points to a string that	is a build information associated with
	   this	provider.  OpenSSL in-built providers use
	   OPENSSL_FULL_VERSION_STR, but this may be different for any third
	   party provider.

       provider_gettable_params() should return	the above parameters.

   Core	parameters
       core_get_params() can retrieve the following core parameters for	each

       "openssl-version" (OSSL_PROV_PARAM_CORE_VERSION)	<UTF8_ptr>
	   This	points to the OpenSSL libraries' full version string, i.e. the
	   string expanded from	the macro OPENSSL_VERSION_STR.

       "provider-name" (OSSL_PROV_PARAM_CORE_PROV_NAME)	<UTF8_ptr>
	   This	points to the OpenSSL libraries' idea of what the calling
	   provider is named.

       "module-filename" (OSSL_PROV_PARAM_CORE_MODULE_FILENAME)	<UTF8_ptr>
	   This	points to a string containing the full filename	of the
	   providers module file.

       Additionally, provider specific configuration parameters	from the
       config file are available, in dotted name form.	The dotted name	form
       is a concatenation of section names and final config command name
       separated by periods.

       For example, let's say we have the following config example:

	openssl_conf = openssl_init

	providers = providers_sect

	foo = foo_sect

	activate = 1
	data1 =	2
	data2 =	str
	more = foo_more

	data3 =	foo,bar

       The provider will have these additional parameters available:

	   pointing at the string "1"

	   pointing at the string "2"

	   pointing at the string "str"

	   pointing at the string "foo,bar"

       For more	information on handling	parameters, see	OSSL_PARAM(3) as

       Capabilities describe some of the services that a provider can offer.
       Applications can	query the capabilities to discover those services.

       "TLS-GROUP" Capability

       The "TLS-GROUP" capability can be queried by libssl to discover the
       list of TLS groups that a provider can support. Each group supported
       can be used for key exchange during a TLS handshake. TLS	clients	can
       advertise the list of TLS groups	they support in	the supported_groups
       extension, and TLS servers can select a group from the offered list
       that they also support. In this way a provider can add to the list of
       groups that libssl already supports with	additional ones.

       Each TLS	group that a provider supports should be described via the
       callback	passed in through the provider_get_capabilities	function. Each
       group should have the following details supplied	(all are mandatory):

       "tls-group-name"	(OSSL_CAPABILITY_TLS_GROUP_NAME) <utf8 string>
	   The name of the group as given in the IANA TLS Supported Groups

       "tls-group-name-internal" (OSSL_CAPABILITY_TLS_GROUP_NAME_INTERNAL)
       <utf8 string>
	   The name of the group as known by the provider. This	could be the
	   same	as the "tls-group-name", but does not have to be.

       "tls-group-id" (OSSL_CAPABILITY_TLS_GROUP_ID) <unsigned integer>
	   The TLS group id value as given in the IANA TLS Supported Groups

       "tls-group-alg" (OSSL_CAPABILITY_TLS_GROUP_ALG) <utf8 string>
	   The name of a Key Management	algorithm that the provider offers and
	   that	should be used with this group.	Keys created should be able to
	   support key exchange.  The algorithm	must support key and parameter
	   generation as well as the key/parameter generation parameter,
	   OSSL_PKEY_PARAM_GROUP_NAME. The group name given via	"tls-group-
	   name-internal" above	will be	passed via OSSL_PKEY_PARAM_GROUP_NAME
	   when	libssl wishes to generate keys/parameters.

       "tls-group-sec-bits" (OSSL_CAPABILITY_TLS_GROUP_SECURITY_BITS)
       <unsigned integer>
	   The number of bits of security offered by keys in this group. The
	   number of bits should be comparable with the	ones given in table 2
	   and 3 of the	NIST SP800-57 document.

       "tls-min-tls" (OSSL_CAPABILITY_TLS_GROUP_MIN_TLS) <integer>
       "tls-max-tls" (OSSL_CAPABILITY_TLS_GROUP_MAX_TLS) <integer>
       "tls-min-dtls" (OSSL_CAPABILITY_TLS_GROUP_MIN_DTLS) <integer>
       "tls-max-dtls" (OSSL_CAPABILITY_TLS_GROUP_MAX_DTLS) <integer>
	   These parameters can	be used	to describe the	minimum	and maximum
	   TLS and DTLS	versions supported by the group. The values equate to
	   the on-the-wire encoding of the various TLS versions. For example
	   TLSv1.3 is 0x0304 (772 decimal), and	TLSv1.2	is 0x0303 (771
	   decimal). A 0 indicates that	there is no defined minimum or
	   maximum. A -1 indicates that	the group should not be	used in	that

       This is an example of a simple provider made available as a dynamically
       loadable	module.	 It implements the fictitious algorithm	"FOO" for the
       fictitious operation "BAR".

	#include <malloc.h>
	#include <openssl/core.h>
	#include <openssl/core_dispatch.h>

	/* Errors used in this provider	*/
	#define	E_MALLOC       1

	static const OSSL_ITEM reasons[] = {
	    { E_MALLOC,	"memory	allocation failure" }.
	    { 0, NULL }	/* Termination */

	 * To ensure we	get the	function signature right, forward declare
	 * them	using function types provided by openssl/core_dispatch.h
	OSSL_FUNC_bar_newctx_fn	foo_newctx;
	OSSL_FUNC_bar_freectx_fn foo_freectx;
	OSSL_FUNC_bar_init_fn foo_init;
	OSSL_FUNC_bar_update_fn	foo_update;
	OSSL_FUNC_bar_final_fn foo_final;

	OSSL_FUNC_provider_query_operation_fn p_query;
	OSSL_FUNC_provider_get_reason_strings_fn p_reasons;
	OSSL_FUNC_provider_teardown_fn p_teardown;

	OSSL_provider_init_fn OSSL_provider_init;

	OSSL_FUNC_core_put_error *c_put_error =	NULL;

	/* Provider context */
	struct prov_ctx_st {
	    OSSL_CORE_HANDLE *handle;

	/* operation context for the algorithm FOO */
	struct foo_ctx_st {
	    struct prov_ctx_st *provctx;
	    int	b;

	static void *foo_newctx(void *provctx)
	    struct foo_ctx_st *fooctx =	malloc(sizeof(*fooctx));

	    if (fooctx != NULL)
		fooctx->provctx	= provctx;
		c_put_error(provctx->handle, E_MALLOC, __FILE__, __LINE__);
	    return fooctx;

	static void foo_freectx(void *fooctx)

	static int foo_init(void *vfooctx)
	    struct foo_ctx_st *fooctx =	vfooctx;

	    fooctx->b =	0x33;

	static int foo_update(void *vfooctx, unsigned char *in,	size_t inl)
	    struct foo_ctx_st *fooctx =	vfooctx;

	    /* did you expect something	serious? */
	    if (inl == 0)
		return 1;
	    for	(; inl-- > 0; in++)
		*in ^= fooctx->b;
	    return 1;

	static int foo_final(void *vfooctx)
	    struct foo_ctx_st *fooctx =	vfooctx;

	    fooctx->b =	0x66;

	static const OSSL_DISPATCH foo_fns[] = {
	    { OSSL_FUNC_BAR_NEWCTX, (void (*)(void))foo_newctx },
	    { OSSL_FUNC_BAR_FREECTX, (void (*)(void))foo_freectx },
	    { OSSL_FUNC_BAR_INIT, (void	(*)(void))foo_init },
	    { OSSL_FUNC_BAR_UPDATE, (void (*)(void))foo_update },
	    { OSSL_FUNC_BAR_FINAL, (void (*)(void))foo_final },
	    { 0, NULL }

	static const OSSL_ALGORITHM bars[] = {
	    { "FOO", "provider=chumbawamba", foo_fns },
	    { NULL, NULL, NULL }

	static const OSSL_ALGORITHM *p_query(void *provctx, int	operation_id,
					     int *no_store)
	    switch (operation_id) {
	    case OSSL_OP_BAR:
		return bars;
	    return NULL;

	static const OSSL_ITEM *p_reasons(void *provctx)
	    return reasons;

	static void p_teardown(void *provctx)

	static const OSSL_DISPATCH prov_fns[] =	{
	    { OSSL_FUNC_PROVIDER_TEARDOWN, (void (*)(void))p_teardown },
	    { OSSL_FUNC_PROVIDER_QUERY_OPERATION, (void	(*)(void))p_query },
	    { OSSL_FUNC_PROVIDER_GET_REASON_STRINGS, (void (*)(void))p_reasons },
	    { 0, NULL }

	int OSSL_provider_init(const OSSL_CORE_HANDLE *handle,
			       const OSSL_DISPATCH *in,
			       const OSSL_DISPATCH **out,
			       void **provctx)
	    struct prov_ctx_st *pctx = NULL;

	    for	(; in->function_id != 0; in++)
		switch (in->function_id) {
		    c_put_error	= OSSL_FUNC_core_put_error(in);

	    *out = prov_fns;

	    if ((pctx =	malloc(sizeof(*pctx))) == NULL)	{
		 * ALEA	IACTA EST, if the core retrieves the reason table
		 * regardless, that string will	be displayed, otherwise	not.
		c_put_error(handle, E_MALLOC, __FILE__,	__LINE__);
		return 0;
	    pctx->handle = handle;
	    return 1;

       This relies on a	few things existing in openssl/core_dispatch.h:

	#define	OSSL_OP_BAR	       4711

	typedef	void *(OSSL_FUNC_bar_newctx_fn)(void *provctx);
	static ossl_inline OSSL_FUNC_bar_newctx(const OSSL_DISPATCH *opf)
	{ return (OSSL_FUNC_bar_newctx_fn *)opf->function; }

	typedef	void (OSSL_FUNC_bar_freectx_fn)(void *ctx);
	static ossl_inline OSSL_FUNC_bar_newctx(const OSSL_DISPATCH *opf)
	{ return (OSSL_FUNC_bar_freectx_fn *)opf->function; }

	#define	OSSL_FUNC_BAR_INIT	  3
	typedef	void *(OSSL_FUNC_bar_init_fn)(void *ctx);
	static ossl_inline OSSL_FUNC_bar_init(const OSSL_DISPATCH *opf)
	{ return (OSSL_FUNC_bar_init_fn	*)opf->function; }

	typedef	void *(OSSL_FUNC_bar_update_fn)(void *ctx,
					      unsigned char *in, size_t	inl);
	static ossl_inline OSSL_FUNC_bar_update(const OSSL_DISPATCH *opf)
	{ return (OSSL_FUNC_bar_update_fn *)opf->function; }

	#define	OSSL_FUNC_BAR_FINAL	  5
	typedef	void *(OSSL_FUNC_bar_final_fn)(void *ctx);
	static ossl_inline OSSL_FUNC_bar_final(const OSSL_DISPATCH *opf)
	{ return (OSSL_FUNC_bar_final_fn *)opf->function; }


       The concept of providers	and everything surrounding them	was introduced
       in OpenSSL 3.0.

       Copyright 2019-2020 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

3.0.0-alpha6			  2020-08-06		      PROVIDER-BASE(7)


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