provider-kem - The kem library <-> provider functions
#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_kem_newctx(void *provctx);
void OSSL_FUNC_kem_freectx(void *ctx);
void *OSSL_FUNC_kem_dupctx(void *ctx);
/* Encapsulation */
int OSSL_FUNC_kem_encapsulate_init(void *ctx, void *provkey, const char *name,
const OSSL_PARAM params[]);
int OSSL_FUNC_kem_encapsulate(void *ctx, unsigned char *out, size_t *outlen,
unsigned char *secret, size_t *secretlen);
/* Decapsulation */
int OSSL_FUNC_kem_decapsulate_init(void *ctx, void *provkey, const char *name);
int OSSL_FUNC_kem_decapsulate(void *ctx, unsigned char *out, size_t *outlen,
const unsigned char *in, size_t inlen);
/* KEM parameters */
int OSSL_FUNC_kem_get_ctx_params(void *ctx, OSSL_PARAM params[]);
const OSSL_PARAM *OSSL_FUNC_kem_gettable_ctx_params(void *ctx, void *provctx);
int OSSL_FUNC_kem_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
const OSSL_PARAM *OSSL_FUNC_kem_settable_ctx_params(void *ctx, void *provctx);
This documentation is primarily aimed at provider authors. See
provider(7) for further information.
The asymmetric kem (OSSL_OP_KEM) operation enables providers to implement
asymmetric kem algorithms and make them available to applications via the API
functions
EVP_PKEY_encapsulate(3),
EVP_PKEY_decapsulate(3) and
other related functions.
All "functions" mentioned here are passed as function pointers between
libcrypto and the provider in
OSSL_DISPATCH(3) arrays via
OSSL_ALGORITHM(3) arrays that are returned by the provider's
provider_query_operation() function (see "Provider Functions"
in
provider-base(7)).
All these "functions" have a corresponding function type definition
named
OSSL_FUNC_{name}_fn, and a helper function to retrieve the
function pointer from an
OSSL_DISPATCH(3) element named
OSSL_FUNC_{name}. For example, the "function"
OSSL_FUNC_kem_newctx() has these:
typedef void *(OSSL_FUNC_kem_newctx_fn)(void *provctx);
static ossl_inline OSSL_FUNC_kem_newctx_fn
OSSL_FUNC_kem_newctx(const OSSL_DISPATCH *opf);
OSSL_DISPATCH(3) arrays are indexed by numbers that are provided as
macros in
openssl-core_dispatch.h(7), as follows:
OSSL_FUNC_kem_newctx OSSL_FUNC_KEM_NEWCTX
OSSL_FUNC_kem_freectx OSSL_FUNC_KEM_FREECTX
OSSL_FUNC_kem_dupctx OSSL_FUNC_KEM_DUPCTX
OSSL_FUNC_kem_encapsulate_init OSSL_FUNC_KEM_ENCAPSULATE_INIT
OSSL_FUNC_kem_encapsulate OSSL_FUNC_KEM_ENCAPSULATE
OSSL_FUNC_kem_decapsulate_init OSSL_FUNC_KEM_DECAPSULATE_INIT
OSSL_FUNC_kem_decapsulate OSSL_FUNC_KEM_DECAPSULATE
OSSL_FUNC_kem_get_ctx_params OSSL_FUNC_KEM_GET_CTX_PARAMS
OSSL_FUNC_kem_gettable_ctx_params OSSL_FUNC_KEM_GETTABLE_CTX_PARAMS
OSSL_FUNC_kem_set_ctx_params OSSL_FUNC_KEM_SET_CTX_PARAMS
OSSL_FUNC_kem_settable_ctx_params OSSL_FUNC_KEM_SETTABLE_CTX_PARAMS
An asymmetric kem algorithm implementation may not implement all of these
functions. In order to be a consistent set of functions a provider must
implement OSSL_FUNC_kem_newctx and OSSL_FUNC_kem_freectx. It must also
implement both of OSSL_FUNC_kem_encapsulate_init and
OSSL_FUNC_kem_encapsulate, or both of OSSL_FUNC_kem_decapsulate_init and
OSSL_FUNC_kem_decapsulate. OSSL_FUNC_kem_get_ctx_params is optional but if it
is present then so must OSSL_FUNC_kem_gettable_ctx_params. Similarly,
OSSL_FUNC_kem_set_ctx_params is optional but if it is present then so must
OSSL_FUNC_kem_settable_ctx_params.
An asymmetric kem algorithm must also implement some mechanism for generating,
loading or importing keys via the key management (OSSL_OP_KEYMGMT) operation.
See
provider-keymgmt(7) for further details.
OSSL_FUNC_kem_newctx() should create and return a pointer to a provider
side structure for holding context information during an asymmetric kem
operation. A pointer to this context will be passed back in a number of the
other asymmetric kem operation function calls. The parameter
provctx is
the provider context generated during provider initialisation (see
provider(7)).
OSSL_FUNC_kem_freectx() is passed a pointer to the provider side
asymmetric kem context in the
ctx parameter. This function should free
any resources associated with that context.
OSSL_FUNC_kem_dupctx() should duplicate the provider side asymmetric kem
context in the
ctx parameter and return the duplicate copy.
OSSL_FUNC_kem_encapsulate_init() initialises a context for an asymmetric
encapsulation given a provider side asymmetric kem context in the
ctx
parameter, a pointer to a provider key object in the
provkey parameter
and the
name of the algorithm. The
params, if not NULL, should
be set on the context in a manner similar to using
OSSL_FUNC_kem_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_kem_encapsulate() performs the actual encapsulation itself. A
previously initialised asymmetric kem context is passed in the
ctx
parameter. Unless
out is NULL, the data to be encapsulated is
internally generated, and returned into the buffer pointed to by the
secret parameter and the encapsulated data should also be written to
the location pointed to by the
out parameter. The length of the
encapsulated data should be written to
*outlen and the length of the
generated secret should be written to
*secretlen.
If
out is NULL then the maximum length of the encapsulated data should be
written to
*outlen, and the maximum length of the generated secret
should be written to
*secretlen.
OSSL_FUNC_kem_decapsulate_init() initialises a context for an asymmetric
decapsulation given a provider side asymmetric kem context in the
ctx
parameter, a pointer to a provider key object in the
provkey parameter,
and a
name of the algorithm. 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_kem_decapsulate() performs the actual decapsulation itself. A
previously initialised asymmetric kem context is passed in the
ctx
parameter. The data to be decapsulated is pointed to by the
in
parameter which is
inlen bytes long. Unless
out is NULL, the
decapsulated data should be written to the location pointed to by the
out parameter. The length of the decapsulated data should be written to
*outlen. If
out is NULL then the maximum length of the
decapsulated data should be written to
*outlen.
See
OSSL_PARAM(3) for further details on the parameters structure used by
the
OSSL_FUNC_kem_get_ctx_params() and
OSSL_FUNC_kem_set_ctx_params() functions.
OSSL_FUNC_kem_get_ctx_params() gets asymmetric kem parameters associated
with the given provider side asymmetric kem context
ctx and stores them
in
params. Passing NULL for
params should return true.
OSSL_FUNC_kem_set_ctx_params() sets the asymmetric kem parameters
associated with the given provider side asymmetric kem context
ctx to
params. Any parameter settings are additional to any that were
previously set. Passing NULL for
params should return true.
No parameters are currently recognised by built-in asymmetric kem algorithms.
OSSL_FUNC_kem_gettable_ctx_params() and
OSSL_FUNC_kem_settable_ctx_params() get a constant
OSSL_PARAM(3)
array that describes the gettable and settable parameters, i.e. parameters
that can be used with
OSSL_FUNC_kem_get_ctx_params() and
OSSL_FUNC_kem_set_ctx_params() respectively.
OSSL_FUNC_kem_newctx() and
OSSL_FUNC_kem_dupctx() should return
the newly created provider side asymmetric kem context, or NULL on failure.
All other functions should return 1 for success or 0 on error.
provider(7)
The provider KEM interface was introduced in OpenSSL 3.0.
Copyright 2020-2021 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
<
https://www.openssl.org/source/license.html>.