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

=pod

=head1 NAME

evp_generic_fetch, 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_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_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;

        if (!CRYPTO_NEW_REF(&foo->refcnt, 1))
            goto err;

        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;
            }
        }
        if (prov != NULL && !ossl_provider_up_ref(prov))
            goto err;

        foo->prov = prov;

        return foo;

    err:
        if (foo != NULL)
            CRYPTO_FREE_REF(&foo->refcnt);
        OPENSSL_free(foo);
        return NULL
    }

    EVP_FOO_meth_free(EVP_FOO *foo)
    {
        int i;

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

            CRYPTO_DOWN_REF(&foo->refcnt, &i);
            if (i > 0)
                return;

            CRYPTO_FREE_REF(&foo->refcnt);
            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);
        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 2019-2025 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
16ff70a5	5	evp_generic_fetch, 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
2fd3392c RL	23	void evp_generic_fetch_from_prov(OSSL_PROVIDER prov, int operation_id,
	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 ));
f7c16d48	32
c13d2ab4 RL	33	=head1 DESCRIPTION
	34
	35	evp_generic_fetch() calls ossl_method_construct() with the given
f7c16d48	36	I<libctx>, I<operation_id>, I<name>, and I<properties> and uses
c13d2ab4	37	it to create an EVP method with the help of the functions
f7c16d48 RL	38	I<new_method>, I<up_ref_method>, and I<free_method>.
f7c16d48 RL	39
2fd3392c RL	40	evp_generic_fetch_from_prov() does the same thing as evp_generic_fetch(),
	41	but limits the search of methods to the provider given with I<prov>.
	42	This is meant to be used when one method needs to fetch an associated
	43	method in the same provider.
	44
f7c16d48 RL	45	The three functions I<new_method>, I<up_ref_method>, and
f7c16d48 RL	46	I<free_method> are supposed to:
c13d2ab4 RL	47
	48	=over 4
	49
	50	=item new_method()
	51
	52	creates an internal method from function pointers found in the
f7c16d48 RL	53	dispatch table I<fns>, with name identity I<name_id>.
	54	The provider I<prov> and I<method_data> are also passed to be used as
	55	new_method() sees fit.
c13d2ab4	56
7c95390e	57	=item up_ref_method()
c13d2ab4 RL	58
	59	increments the reference counter for the given method, if there is
	60	one.
	61
	62	=item free_method()
	63
	64	frees the given method.
	65
	66	=back
	67
	68	=head1 RETURN VALUES
	69
dfabee82	70	evp_generic_fetch() returns a method on success, or NULL on error.
c13d2ab4 RL	71
	72	=head1 EXAMPLES
	73
	74	This is a short example of the fictitious EVP API and operation called
f7c16d48	75	B<EVP_FOO>.
c13d2ab4 RL	76
c13d2ab4 RL	77	To begin with, let's assume something like this in
23c48d94	78	F<include/openssl/core_dispatch.h>:
c13d2ab4	79
363b1e5d DMSP	80	#define OSSL_OP_FOO 100
	81
	82	#define OSSL_FUNC_FOO_NEWCTX_FUNC 2001
	83	#define OSSL_FUNC_FOO_INIT 2002
	84	#define OSSL_FUNC_FOO_OPERATE 2003
	85	#define OSSL_FUNC_FOO_CLEANCTX_FUNC 2004
	86	#define OSSL_FUNC_FOO_FREECTX_FUNC 2005
	87
	88	OSSL_CORE_MAKE_FUNC(void *, foo_newctx, (void))
	89	OSSL_CORE_MAKE_FUNC(int, foo_init, (void *vctx))
	90	OSSL_CORE_MAKE_FUNC(int, foo_operate, (void *vctx,
	91	unsigned char out, size_t out_l,
	92	unsigned char *in, size_t in_l))
	93	OSSL_CORE_MAKE_FUNC(void, foo_cleanctx, (void *vctx))
	94	OSSL_CORE_MAKE_FUNC(void, foo_freectx, (void *vctx))
c13d2ab4 RL	95
	96	And here's the implementation of the FOO method fetcher:
	97
	98	/* typedef struct evp_foo_st EVP_FOO */
	99	struct evp_foo_st {
	100	OSSL_PROVIDER *prov;
f7c16d48	101	int name_id;
c13d2ab4	102	CRYPTO_REF_COUNT refcnt;
363b1e5d DMSP	103	OSSL_FUNC_foo_newctx_fn *newctx;
	104	OSSL_FUNC_foo_init_fn *init;
	105	OSSL_FUNC_foo_operate_fn *operate;
	106	OSSL_FUNC_foo_cleanctx_fn *cleanctx;
	107	OSSL_FUNC_foo_freectx_fn *freectx;
c13d2ab4 RL	108	};
	109
	110	/*
	111	* In this example, we have a public method creator and destructor.
	112	* It's not absolutely necessary, but is in the spirit of OpenSSL.
	113	*/
309a78aa RL	114	EVP_FOO *EVP_FOO_meth_from_algorithm(int name_id,
	115	const OSSL_DISPATCH *fns,
	116	OSSL_PROVIDER *prov,
	117	void *data)
c13d2ab4 RL	118	{
	119	EVP_FOO *foo = NULL;
	120
	121	if ((foo = OPENSSL_zalloc(sizeof(*foo))) == NULL)
	122	return NULL;
	123
00fbc969 FWH	124	if (!CRYPTO_NEW_REF(&foo->refcnt, 1))
00fbc969 FWH	125	goto err;
52c362b3	126
f7c16d48 RL	127	foo->name_id = name_id;
f7c16d48 RL	128
c13d2ab4 RL	129	for (; fns->function_id != 0; fns++) {
c13d2ab4 RL	130	switch (fns->function_id) {
363b1e5d DMSP	131	case OSSL_FUNC_FOO_NEWCTX:
363b1e5d DMSP	132	foo->newctx = OSSL_FUNC_foo_newctx(fns);
c13d2ab4	133	break;
363b1e5d DMSP	134	case OSSL_FUNC_FOO_INIT:
363b1e5d DMSP	135	foo->init = OSSL_FUNC_foo_init(fns);
c13d2ab4	136	break;
363b1e5d DMSP	137	case OSSL_FUNC_FOO_OPERATE:
363b1e5d DMSP	138	foo->operate = OSSL_FUNC_foo_operate(fns);
c13d2ab4	139	break;
363b1e5d DMSP	140	case OSSL_FUNC_FOO_CLEANCTX:
363b1e5d DMSP	141	foo->cleanctx = OSSL_FUNC_foo_cleanctx(fns);
c13d2ab4	142	break;
363b1e5d DMSP	143	case OSSL_FUNC_FOO_FREECTX:
363b1e5d DMSP	144	foo->freectx = OSSL_FUNC_foo_freectx(fns);
c13d2ab4 RL	145	break;
	146	}
	147	}
00fbc969 FWH	148	if (prov != NULL && !ossl_provider_up_ref(prov))
	149	goto err;
	150
c13d2ab4	151	foo->prov = prov;
c13d2ab4 RL	152
c13d2ab4 RL	153	return foo;
00fbc969 FWH	154
	155	err:
	156	if (foo != NULL)
	157	CRYPTO_FREE_REF(&foo->refcnt);
	158	OPENSSL_free(foo);
	159	return NULL
c13d2ab4 RL	160	}
	161
	162	EVP_FOO_meth_free(EVP_FOO *foo)
	163	{
52c362b3 P	164	int i;
52c362b3 P	165
c13d2ab4 RL	166	if (foo != NULL) {
	167	OSSL_PROVIDER *prov = foo->prov;
	168
52c362b3 P	169	CRYPTO_DOWN_REF(&foo->refcnt, &i);
	170	if (i > 0)
	171	return;
	172
	173	CRYPTO_FREE_REF(&foo->refcnt);
c13d2ab4 RL	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
52c362b3	190	CRYPTO_UP_REF(&foo->refcnt, &ref);
c13d2ab4 RL	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
0c679f55	278	Copyright 2019-2025 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