[thirdparty/openssl.git] / doc / internal / man3 / evp_generic_fetch.pod

=pod

=head1 NAME

evp_generic_fetch, evp_generic_fetch_by_number, evp_generic_fetch_from_prov
- generic algorithm fetchers and method creators for EVP

=head1 SYNOPSIS

 /* Only for EVP source */
 #include "evp_local.h"

 void *evp_generic_fetch(OSSL_LIB_CTX *libctx, int operation_id,
                         const char *name, const char *properties,
                         void *(*new_method)(int name_id,
                                             const OSSL_DISPATCH *fns,
                                             OSSL_PROVIDER *prov,
                                             void *method_data),
                         void *method_data,
                         int (*up_ref_method)(void *),
                         void (*free_method)(void *));

 void *evp_generic_fetch_by_number(OSSL_LIB_CTX *ctx, int operation_id,
                                   int name_id, const char *properties,
                                   void *(*new_method)(int name_id,
                                                       const OSSL_DISPATCH *fns,
                                                       OSSL_PROVIDER *prov,
                                                       void *method_data),
                                   void *method_data,
                                   int (*up_ref_method)(void *),
                                   void (*free_method)(void *));
 void *evp_generic_fetch_from_prov(OSSL_PROVIDER *prov, int operation_id,
                                   int name_id, const char *properties,
                                   void *(*new_method)(int name_id,
                                                       const OSSL_DISPATCH *fns,
                                                       OSSL_PROVIDER *prov,
                                                       void *method_data),
                                   void *method_data,
                                   int (*up_ref_method)(void *),
                                   void (*free_method)(void *));

=head1 DESCRIPTION

evp_generic_fetch() calls ossl_method_construct() with the given
I<libctx>, I<operation_id>, I<name>, and I<properties> and uses
it to create an EVP method with the help of the functions
I<new_method>, I<up_ref_method>, and I<free_method>.

evp_generic_fetch_by_number() does the same thing as evp_generic_fetch(),
but takes a numeric I<name_id> instead of a name.
I<name_id> must always be nonzero; as a matter of fact, it being zero
is considered a programming error.
This is meant to be used when one method needs to fetch an associated
method, and is typically called from inside the given function
I<new_method>.

evp_generic_fetch_from_prov() does the same thing as evp_generic_fetch(),
but limits the search of methods to the provider given with I<prov>.
This is meant to be used when one method needs to fetch an associated
method in the same provider.

The three functions I<new_method>, I<up_ref_method>, and
I<free_method> are supposed to:

=over 4

=item new_method()

creates an internal method from function pointers found in the
dispatch table I<fns>, with name identity I<name_id>.
The provider I<prov> and I<method_data> are also passed to be used as
new_method() sees fit.

=item up_ref_method()

increments the reference counter for the given method, if there is
one.

=item free_method()

frees the given method.

=back

=head1 RETURN VALUES

evp_generic_fetch() returns a method on success, or NULL on error.

=head1 EXAMPLES

This is a short example of the fictitious EVP API and operation called
B<EVP_FOO>.

To begin with, let's assume something like this in
F<include/openssl/core_dispatch.h>:

    #define OSSL_OP_FOO                           100

    #define OSSL_FUNC_FOO_NEWCTX_FUNC            2001
    #define OSSL_FUNC_FOO_INIT                   2002
    #define OSSL_FUNC_FOO_OPERATE                2003
    #define OSSL_FUNC_FOO_CLEANCTX_FUNC          2004
    #define OSSL_FUNC_FOO_FREECTX_FUNC           2005

    OSSL_CORE_MAKE_FUNC(void *, foo_newctx, (void))
    OSSL_CORE_MAKE_FUNC(int, foo_init, (void *vctx))
    OSSL_CORE_MAKE_FUNC(int, foo_operate, (void *vctx,
                                           unsigned char *out, size_t *out_l,
                                           unsigned char *in, size_t in_l))
    OSSL_CORE_MAKE_FUNC(void, foo_cleanctx, (void *vctx))
    OSSL_CORE_MAKE_FUNC(void, foo_freectx, (void *vctx))

And here's the implementation of the FOO method fetcher:

    /* typedef struct evp_foo_st EVP_FOO */
    struct evp_foo_st {
        OSSL_PROVIDER *prov;
        int name_id;
	CRYPTO_REF_COUNT refcnt;
        OSSL_FUNC_foo_newctx_fn *newctx;
        OSSL_FUNC_foo_init_fn *init;
        OSSL_FUNC_foo_operate_fn *operate;
        OSSL_FUNC_foo_cleanctx_fn *cleanctx;
        OSSL_FUNC_foo_freectx_fn *freectx;
    };

    /*
     * In this example, we have a public method creator and destructor.
     * It's not absolutely necessary, but is in the spirit of OpenSSL.
     */
    EVP_FOO *EVP_FOO_meth_from_algorithm(int name_id,
                                         const OSSL_DISPATCH *fns,
                                         OSSL_PROVIDER *prov,
                                         void *data)
    {
        EVP_FOO *foo = NULL;

        if ((foo = OPENSSL_zalloc(sizeof(*foo))) == NULL)
            return NULL;

        foo->name_id = name_id;

        for (; fns->function_id != 0; fns++) {
            switch (fns->function_id) {
            case OSSL_FUNC_FOO_NEWCTX:
                foo->newctx = OSSL_FUNC_foo_newctx(fns);
                break;
            case OSSL_FUNC_FOO_INIT:
                foo->init = OSSL_FUNC_foo_init(fns);
                break;
            case OSSL_FUNC_FOO_OPERATE:
                foo->operate = OSSL_FUNC_foo_operate(fns);
                break;
            case OSSL_FUNC_FOO_CLEANCTX:
                foo->cleanctx = OSSL_FUNC_foo_cleanctx(fns);
                break;
            case OSSL_FUNC_FOO_FREECTX:
                foo->freectx = OSSL_FUNC_foo_freectx(fns);
                break;
            }
        }
        foo->prov = prov;
        if (prov)
            ossl_provider_up_ref(prov);

        return foo;
    }

    EVP_FOO_meth_free(EVP_FOO *foo)
    {
        if (foo != NULL) {
            OSSL_PROVIDER *prov = foo->prov;

            OPENSSL_free(foo);
            ossl_provider_free(prov);
        }
    }

    static void *foo_from_algorithm(const OSSL_DISPATCH *fns,
                                    OSSL_PROVIDER *prov)
    {
        return EVP_FOO_meth_from_algorithm(fns, prov);
    }

    static int foo_up_ref(void *vfoo)
    {
        EVP_FOO *foo = vfoo;
        int ref = 0;

        CRYPTO_UP_REF(&foo->refcnt, &ref, foo_lock);
        return 1;
    }

    static void foo_free(void *vfoo)
    {
        EVP_FOO_meth_free(vfoo);
    }

    EVP_FOO *EVP_FOO_fetch(OSSL_LIB_CTX *ctx,
                           const char *name,
                           const char *properties)
    {
        EVP_FOO *foo =
            evp_generic_fetch(ctx, OSSL_OP_FOO, name, properties,
                              foo_from_algorithm, foo_up_ref, foo_free);

        /*
         * If this method exists in legacy form, with a constant NID for the
         * given |name|, this is the spot to find that NID and set it in
         * the newly constructed EVP_FOO instance.
         */

        return foo;

    }

And finally, the library functions:

    /* typedef struct evp_foo_st EVP_FOO_CTX */
    struct evp_foo_ctx_st {
        const EVP_FOO *foo;
        void *provctx;		/* corresponding provider context */
    };

    int EVP_FOO_CTX_reset(EVP_FOO_CTX *c)
    {
        if (c == NULL)
            return 1;
        if (c->foo != NULL && c->foo->cleanctx != NULL)
            c->foo->cleanctx(c->provctx);
        return 1;
    }

    EVP_FOO_CTX *EVP_FOO_CTX_new(void)
    {
        return OPENSSL_zalloc(sizeof(EVP_FOO_CTX));
    }

    void EVP_FOO_CTX_free(EVP_FOO_CTX *c)
    {
        EVP_FOO_CTX_reset(c);
        c->foo->freectx(c->provctx);
        OPENSSL_free(c);
    }

    int EVP_FooInit(EVP_FOO_CTX *c, const EVP_FOO *foo)
    {
        int ok = 1;

        c->foo = foo;
        if (c->provctx == NULL)
            c->provctx = c->foo->newctx();

        ok = c->foo->init(c->provctx);

        return ok;
    }

    int EVP_FooOperate(EVP_FOO_CTX *c, unsigned char *out, size_t *outl,
                       const unsigned char *in, size_t inl)
    {
        int ok = 1;

        ok = c->foo->update(c->provctx, out, inl, &outl, in, inl);
        return ok;
    }

=head1 SEE ALSO

L<ossl_method_construct(3)>

=head1 HISTORY

The functions described here were all added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019-2021 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
Commit	Line	Data
c13d2ab4 RL	1	=pod
	2
	3	=head1 NAME
	4
2fd3392c	5	evp_generic_fetch, evp_generic_fetch_by_number, evp_generic_fetch_from_prov
f7c16d48	6	- generic algorithm fetchers and method creators for EVP
c13d2ab4 RL	7
	8	=head1 SYNOPSIS
	9
	10	/* Only for EVP source */
706457b7	11	#include "evp_local.h"
c13d2ab4	12
b4250010	13	void evp_generic_fetch(OSSL_LIB_CTX libctx, int operation_id,
2e49c054	14	const char name, const char properties,
f7c16d48	15	void (new_method)(int name_id,
3ca9d210 RL	16	const OSSL_DISPATCH *fns,
	17	OSSL_PROVIDER *prov,
	18	void *method_data),
	19	void *method_data,
7c95390e	20	int (up_ref_method)(void ),
0211740f	21	void (free_method)(void ));
c13d2ab4	22
b4250010	23	void evp_generic_fetch_by_number(OSSL_LIB_CTX ctx, int operation_id,
f7c16d48 RL	24	int name_id, const char *properties,
	25	void (new_method)(int name_id,
	26	const OSSL_DISPATCH *fns,
	27	OSSL_PROVIDER *prov,
	28	void *method_data),
	29	void *method_data,
	30	int (up_ref_method)(void ),
	31	void (free_method)(void ));
2fd3392c RL	32	void evp_generic_fetch_from_prov(OSSL_PROVIDER prov, int operation_id,
	33	int name_id, const char *properties,
	34	void (new_method)(int name_id,
	35	const OSSL_DISPATCH *fns,
	36	OSSL_PROVIDER *prov,
	37	void *method_data),
	38	void *method_data,
	39	int (up_ref_method)(void ),
	40	void (free_method)(void ));
f7c16d48	41
c13d2ab4 RL	42	=head1 DESCRIPTION
	43
	44	evp_generic_fetch() calls ossl_method_construct() with the given
f7c16d48	45	I<libctx>, I<operation_id>, I<name>, and I<properties> and uses
c13d2ab4	46	it to create an EVP method with the help of the functions
f7c16d48 RL	47	I<new_method>, I<up_ref_method>, and I<free_method>.
f7c16d48 RL	48
57cd10dd	49	evp_generic_fetch_by_number() does the same thing as evp_generic_fetch(),
1b0f5b62	50	but takes a numeric I<name_id> instead of a name.
9c0586d5	51	I<name_id> must always be nonzero; as a matter of fact, it being zero
f7c16d48 RL	52	is considered a programming error.
f7c16d48 RL	53	This is meant to be used when one method needs to fetch an associated
2fd3392c	54	method, and is typically called from inside the given function
f7c16d48	55	I<new_method>.
c13d2ab4	56
2fd3392c RL	57	evp_generic_fetch_from_prov() does the same thing as evp_generic_fetch(),
	58	but limits the search of methods to the provider given with I<prov>.
	59	This is meant to be used when one method needs to fetch an associated
	60	method in the same provider.
	61
f7c16d48 RL	62	The three functions I<new_method>, I<up_ref_method>, and
f7c16d48 RL	63	I<free_method> are supposed to:
c13d2ab4 RL	64
	65	=over 4
	66
	67	=item new_method()
	68
	69	creates an internal method from function pointers found in the
f7c16d48 RL	70	dispatch table I<fns>, with name identity I<name_id>.
	71	The provider I<prov> and I<method_data> are also passed to be used as
	72	new_method() sees fit.
c13d2ab4	73
7c95390e	74	=item up_ref_method()
c13d2ab4 RL	75
	76	increments the reference counter for the given method, if there is
	77	one.
	78
	79	=item free_method()
	80
	81	frees the given method.
	82
	83	=back
	84
	85	=head1 RETURN VALUES
	86
dfabee82	87	evp_generic_fetch() returns a method on success, or NULL on error.
c13d2ab4 RL	88
	89	=head1 EXAMPLES
	90
	91	This is a short example of the fictitious EVP API and operation called
f7c16d48	92	B<EVP_FOO>.
c13d2ab4 RL	93
c13d2ab4 RL	94	To begin with, let's assume something like this in
23c48d94	95	F<include/openssl/core_dispatch.h>:
c13d2ab4	96
363b1e5d DMSP	97	#define OSSL_OP_FOO 100
	98
	99	#define OSSL_FUNC_FOO_NEWCTX_FUNC 2001
	100	#define OSSL_FUNC_FOO_INIT 2002
	101	#define OSSL_FUNC_FOO_OPERATE 2003
	102	#define OSSL_FUNC_FOO_CLEANCTX_FUNC 2004
	103	#define OSSL_FUNC_FOO_FREECTX_FUNC 2005
	104
	105	OSSL_CORE_MAKE_FUNC(void *, foo_newctx, (void))
	106	OSSL_CORE_MAKE_FUNC(int, foo_init, (void *vctx))
	107	OSSL_CORE_MAKE_FUNC(int, foo_operate, (void *vctx,
	108	unsigned char out, size_t out_l,
	109	unsigned char *in, size_t in_l))
	110	OSSL_CORE_MAKE_FUNC(void, foo_cleanctx, (void *vctx))
	111	OSSL_CORE_MAKE_FUNC(void, foo_freectx, (void *vctx))
c13d2ab4 RL	112
	113	And here's the implementation of the FOO method fetcher:
	114
	115	/* typedef struct evp_foo_st EVP_FOO */
	116	struct evp_foo_st {
	117	OSSL_PROVIDER *prov;
f7c16d48	118	int name_id;
c13d2ab4	119	CRYPTO_REF_COUNT refcnt;
363b1e5d DMSP	120	OSSL_FUNC_foo_newctx_fn *newctx;
	121	OSSL_FUNC_foo_init_fn *init;
	122	OSSL_FUNC_foo_operate_fn *operate;
	123	OSSL_FUNC_foo_cleanctx_fn *cleanctx;
	124	OSSL_FUNC_foo_freectx_fn *freectx;
c13d2ab4 RL	125	};
	126
	127	/*
	128	* In this example, we have a public method creator and destructor.
	129	* It's not absolutely necessary, but is in the spirit of OpenSSL.
	130	*/
309a78aa RL	131	EVP_FOO *EVP_FOO_meth_from_algorithm(int name_id,
	132	const OSSL_DISPATCH *fns,
	133	OSSL_PROVIDER *prov,
	134	void *data)
c13d2ab4 RL	135	{
	136	EVP_FOO *foo = NULL;
	137
	138	if ((foo = OPENSSL_zalloc(sizeof(*foo))) == NULL)
	139	return NULL;
	140
f7c16d48 RL	141	foo->name_id = name_id;
f7c16d48 RL	142
c13d2ab4 RL	143	for (; fns->function_id != 0; fns++) {
c13d2ab4 RL	144	switch (fns->function_id) {
363b1e5d DMSP	145	case OSSL_FUNC_FOO_NEWCTX:
363b1e5d DMSP	146	foo->newctx = OSSL_FUNC_foo_newctx(fns);
c13d2ab4	147	break;
363b1e5d DMSP	148	case OSSL_FUNC_FOO_INIT:
363b1e5d DMSP	149	foo->init = OSSL_FUNC_foo_init(fns);
c13d2ab4	150	break;
363b1e5d DMSP	151	case OSSL_FUNC_FOO_OPERATE:
363b1e5d DMSP	152	foo->operate = OSSL_FUNC_foo_operate(fns);
c13d2ab4	153	break;
363b1e5d DMSP	154	case OSSL_FUNC_FOO_CLEANCTX:
363b1e5d DMSP	155	foo->cleanctx = OSSL_FUNC_foo_cleanctx(fns);
c13d2ab4	156	break;
363b1e5d DMSP	157	case OSSL_FUNC_FOO_FREECTX:
363b1e5d DMSP	158	foo->freectx = OSSL_FUNC_foo_freectx(fns);
c13d2ab4 RL	159	break;
	160	}
	161	}
c13d2ab4 RL	162	foo->prov = prov;
c13d2ab4 RL	163	if (prov)
7c95390e	164	ossl_provider_up_ref(prov);
c13d2ab4 RL	165
	166	return foo;
	167	}
	168
	169	EVP_FOO_meth_free(EVP_FOO *foo)
	170	{
	171	if (foo != NULL) {
	172	OSSL_PROVIDER *prov = foo->prov;
	173
	174	OPENSSL_free(foo);
	175	ossl_provider_free(prov);
	176	}
	177	}
	178
309a78aa RL	179	static void foo_from_algorithm(const OSSL_DISPATCH fns,
309a78aa RL	180	OSSL_PROVIDER *prov)
c13d2ab4	181	{
309a78aa	182	return EVP_FOO_meth_from_algorithm(fns, prov);
c13d2ab4 RL	183	}
c13d2ab4 RL	184
7c95390e	185	static int foo_up_ref(void *vfoo)
c13d2ab4 RL	186	{
	187	EVP_FOO *foo = vfoo;
	188	int ref = 0;
	189
	190	CRYPTO_UP_REF(&foo->refcnt, &ref, foo_lock);
	191	return 1;
	192	}
	193
	194	static void foo_free(void *vfoo)
	195	{
	196	EVP_FOO_meth_free(vfoo);
	197	}
	198
b4250010	199	EVP_FOO EVP_FOO_fetch(OSSL_LIB_CTX ctx,
2e49c054	200	const char *name,
c13d2ab4 RL	201	const char *properties)
c13d2ab4 RL	202	{
0211740f RL	203	EVP_FOO *foo =
0211740f RL	204	evp_generic_fetch(ctx, OSSL_OP_FOO, name, properties,
309a78aa	205	foo_from_algorithm, foo_up_ref, foo_free);
0211740f RL	206
	207	/*
	208	* If this method exists in legacy form, with a constant NID for the
	209	* given \|name\|, this is the spot to find that NID and set it in
	210	* the newly constructed EVP_FOO instance.
	211	*/
	212
	213	return foo;
	214
c13d2ab4 RL	215	}
	216
	217	And finally, the library functions:
	218
	219	/* typedef struct evp_foo_st EVP_FOO_CTX */
	220	struct evp_foo_ctx_st {
	221	const EVP_FOO *foo;
	222	void provctx; / corresponding provider context */
	223	};
	224
	225	int EVP_FOO_CTX_reset(EVP_FOO_CTX *c)
	226	{
	227	if (c == NULL)
	228	return 1;
	229	if (c->foo != NULL && c->foo->cleanctx != NULL)
	230	c->foo->cleanctx(c->provctx);
	231	return 1;
	232	}
	233
	234	EVP_FOO_CTX *EVP_FOO_CTX_new(void)
	235	{
	236	return OPENSSL_zalloc(sizeof(EVP_FOO_CTX));
	237	}
	238
	239	void EVP_FOO_CTX_free(EVP_FOO_CTX *c)
	240	{
	241	EVP_FOO_CTX_reset(c);
	242	c->foo->freectx(c->provctx);
	243	OPENSSL_free(c);
	244	}
	245
	246	int EVP_FooInit(EVP_FOO_CTX c, const EVP_FOO foo)
	247	{
	248	int ok = 1;
	249
	250	c->foo = foo;
	251	if (c->provctx == NULL)
	252	c->provctx = c->foo->newctx();
	253
	254	ok = c->foo->init(c->provctx);
	255
	256	return ok;
	257	}
	258
	259	int EVP_FooOperate(EVP_FOO_CTX c, unsigned char out, size_t *outl,
	260	const unsigned char *in, size_t inl)
	261	{
	262	int ok = 1;
	263
	264	ok = c->foo->update(c->provctx, out, inl, &outl, in, inl);
	265	return ok;
	266	}
	267
	268	=head1 SEE ALSO
	269
6e4618a0	270	L<ossl_method_construct(3)>
c13d2ab4 RL	271
	272	=head1 HISTORY
	273
	274	The functions described here were all added in OpenSSL 3.0.
	275
	276	=head1 COPYRIGHT
	277
3c2bdd7d	278	Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
c13d2ab4 RL	279
	280	Licensed under the Apache License 2.0 (the "License"). You may not use
	281	this file except in compliance with the License. You can obtain a copy
	282	in the file LICENSE in the source distribution or at
	283	L<https://www.openssl.org/source/license.html>.
	284
	285	=cut