Updated: 2022/Sep/29
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OSSL_DECODER_CTX(3) OpenSSL OSSL_DECODER_CTX(3)
NAME
OSSL_DECODER_CTX, OSSL_DECODER_CTX_new,
OSSL_DECODER_settable_ctx_params, OSSL_DECODER_CTX_set_params,
OSSL_DECODER_CTX_free, OSSL_DECODER_CTX_set_selection,
OSSL_DECODER_CTX_set_input_type, OSSL_DECODER_CTX_set_input_structure,
OSSL_DECODER_CTX_add_decoder, OSSL_DECODER_CTX_add_extra,
OSSL_DECODER_CTX_get_num_decoders, OSSL_DECODER_INSTANCE,
OSSL_DECODER_CONSTRUCT, OSSL_DECODER_CLEANUP,
OSSL_DECODER_CTX_set_construct, OSSL_DECODER_CTX_set_construct_data,
OSSL_DECODER_CTX_set_cleanup, OSSL_DECODER_CTX_get_construct,
OSSL_DECODER_CTX_get_construct_data, OSSL_DECODER_CTX_get_cleanup,
OSSL_DECODER_export, OSSL_DECODER_INSTANCE_get_decoder,
OSSL_DECODER_INSTANCE_get_decoder_ctx,
OSSL_DECODER_INSTANCE_get_input_type,
OSSL_DECODER_INSTANCE_get_input_structure - Decoder context routines
LIBRARY
libcrypto, -lcrypto
SYNOPSIS
#include <openssl/decoder.h>
typedef struct ossl_decoder_ctx_st OSSL_DECODER_CTX;
OSSL_DECODER_CTX *OSSL_DECODER_CTX_new(void);
const OSSL_PARAM *OSSL_DECODER_settable_ctx_params(OSSL_DECODER *decoder);
int OSSL_DECODER_CTX_set_params(OSSL_DECODER_CTX *ctx,
const OSSL_PARAM params[]);
void OSSL_DECODER_CTX_free(OSSL_DECODER_CTX *ctx);
int OSSL_DECODER_CTX_set_selection(OSSL_DECODER_CTX *ctx, int selection);
int OSSL_DECODER_CTX_set_input_type(OSSL_DECODER_CTX *ctx,
const char *input_type);
int OSSL_DECODER_CTX_set_input_structure(OSSL_DECODER_CTX *ctx,
const char *input_structure);
int OSSL_DECODER_CTX_add_decoder(OSSL_DECODER_CTX *ctx, OSSL_DECODER *decoder);
int OSSL_DECODER_CTX_add_extra(OSSL_DECODER_CTX *ctx,
OSSL_LIB_CTX *libctx,
const char *propq);
int OSSL_DECODER_CTX_get_num_decoders(OSSL_DECODER_CTX *ctx);
typedef struct ossl_decoder_instance_st OSSL_DECODER_INSTANCE;
OSSL_DECODER *
OSSL_DECODER_INSTANCE_get_decoder(OSSL_DECODER_INSTANCE *decoder_inst);
void *
OSSL_DECODER_INSTANCE_get_decoder_ctx(OSSL_DECODER_INSTANCE *decoder_inst);
const char *
OSSL_DECODER_INSTANCE_get_input_type(OSSL_DECODER_INSTANCE *decoder_inst);
OSSL_DECODER_INSTANCE_get_input_structure(OSSL_DECODER_INSTANCE *decoder_inst,
int *was_set);
typedef int OSSL_DECODER_CONSTRUCT(OSSL_DECODER_INSTANCE *decoder_inst,
const OSSL_PARAM *object,
void *construct_data);
typedef void OSSL_DECODER_CLEANUP(void *construct_data);
int OSSL_DECODER_CTX_set_construct(OSSL_DECODER_CTX *ctx,
OSSL_DECODER_CONSTRUCT *construct);
int OSSL_DECODER_CTX_set_construct_data(OSSL_DECODER_CTX *ctx,
void *construct_data);
int OSSL_DECODER_CTX_set_cleanup(OSSL_DECODER_CTX *ctx,
OSSL_DECODER_CLEANUP *cleanup);
OSSL_DECODER_CONSTRUCT *OSSL_DECODER_CTX_get_construct(OSSL_DECODER_CTX *ctx);
void *OSSL_DECODER_CTX_get_construct_data(OSSL_DECODER_CTX *ctx);
OSSL_DECODER_CLEANUP *OSSL_DECODER_CTX_get_cleanup(OSSL_DECODER_CTX *ctx);
int OSSL_DECODER_export(OSSL_DECODER_INSTANCE *decoder_inst,
void *reference, size_t reference_sz,
OSSL_CALLBACK *export_cb, void *export_cbarg);
DESCRIPTION
The OSSL_DECODER_CTX holds data about multiple decoders, as needed to
figure out what the input data is and to attempt to unpack it into one
of several possible related results. This also includes chaining
decoders, so the output from one can become the input for another.
This allows having generic format decoders such as PEM to DER, as well
as more specialized decoders like DER to RSA.
The chains may be limited by specifying an input type, which is
considered a starting point. This is both considered by
OSSL_DECODER_CTX_add_extra(), which will stop adding one more decoder
implementations when it has already added those that take the specified
input type, and functions like OSSL_DECODER_from_bio(3), which will
only start the decoding process with the decoder implementations that
take that input type. For example, if the input type is set to "DER",
a PEM to DER decoder will be ignored.
The input type can also be NULL, which means that the caller doesn't
know what type of input they have. In this case,
OSSL_DECODER_from_bio() will simply try with one decoder implementation
after the other, and thereby discover what kind of input the caller
gave it.
For every decoding done, even an intermediary one, a constructor
provided by the caller is called to attempt to construct an appropriate
type / structure that the caller knows how to handle from the current
decoding result. The constructor is set with
OSSL_DECODER_CTX_set_construct().
OSSL_DECODER_INSTANCE is an opaque structure that contains data about
the decoder that was just used, and that may be useful for the
constructor. There are some functions to extract data from this type,
described further down.
Functions
OSSL_DECODER_CTX_new() creates a new empty OSSL_DECODER_CTX.
OSSL_DECODER_settable_ctx_params() returns an OSSL_PARAM(3) array of
parameter descriptors.
OSSL_DECODER_CTX_set_params() attempts to set parameters specified with
an OSSL_PARAM(3) array params. These parameters are passed to all
decoders that have been added to the ctx so far. Parameters that an
implementation doesn't recognise should be ignored by it.
OSSL_DECODER_CTX_free() frees the given context ctx.
OSSL_DECODER_CTX_add_decoder() populates the OSSL_DECODER_CTX ctx with
a decoder, to be used to attempt to decode some encoded input.
OSSL_DECODER_CTX_add_extra() finds decoders that generate input for
already added decoders, and adds them as well. This is used to build
decoder chains.
OSSL_DECODER_CTX_set_input_type() sets the starting input type. This
limits the decoder chains to be considered, as explained in the general
description above.
OSSL_DECODER_CTX_set_input_structure() sets the name of the structure
that the input is expected to have. This may be used to determines
what decoder implementations may be used. NULL is a valid input
structure, when it's not relevant, or when the decoder implementations
are expected to figure it out.
OSSL_DECODER_CTX_get_num_decoders() gets the number of decoders
currently added to the context ctx.
OSSL_DECODER_CTX_set_construct() sets the constructor construct.
OSSL_DECODER_CTX_set_construct_data() sets the constructor data that is
passed to the constructor every time it's called.
OSSL_DECODER_CTX_set_cleanup() sets the constructor data cleanup
function. This is called by OSSL_DECODER_CTX_free(3).
OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data()
and OSSL_DECODER_CTX_get_cleanup() return the values that have been set
by OSSL_DECODER_CTX_set_construct(),
OSSL_DECODER_CTX_set_construct_data() and
OSSL_DECODER_CTX_set_cleanup() respectively.
OSSL_DECODER_export() is a fallback function for constructors that
cannot use the data they get directly for diverse reasons. It takes
the same decode instance decoder_inst that the constructor got and an
object reference, unpacks the object which it refers to, and exports it
by creating an OSSL_PARAM(3) array that it then passes to export_cb,
along with export_arg.
Constructor
A OSSL_DECODER_CONSTRUCT gets the following arguments:
decoder_inst
The OSSL_DECODER_INSTANCE for the decoder from which the
constructor gets its data.
object
A provider-native object abstraction produced by the decoder.
Further information on the provider-native object abstraction can
be found in provider-object(7).
construct_data
The pointer that was set with OSSL_DECODE_CTX_set_construct_data().
The constructor is expected to return 1 when the data it receives can
be constructed, otherwise 0.
These utility functions may be used by a constructor:
OSSL_DECODER_INSTANCE_get_decoder() can be used to get the decoder
implementation from a decoder instance decoder_inst.
OSSL_DECODER_INSTANCE_get_decoder_ctx() can be used to get the decoder
implementation's provider context from a decoder instance decoder_inst.
OSSL_DECODER_INSTANCE_get_input_type() can be used to get the decoder
implementation's input type from a decoder instance decoder_inst.
OSSL_DECODER_INSTANCE_get_input_structure() can be used to get the
input structure for the decoder implementation from a decoder instance
decoder_inst. This may be NULL.
RETURN VALUES
OSSL_DECODER_CTX_new() returns a pointer to a OSSL_DECODER_CTX, or NULL
if the context structure couldn't be allocated.
OSSL_DECODER_settable_ctx_params() returns an OSSL_PARAM(3) array, or
NULL if none is available.
OSSL_DECODER_CTX_set_params() returns 1 if all recognised parameters
were valid, or 0 if one of them was invalid or caused some other
failure in the implementation.
OSSL_DECODER_CTX_add_decoder(), OSSL_DECODER_CTX_add_extra(),
OSSL_DECODER_CTX_set_construct(), OSSL_DECODER_CTX_set_construct_data()
and OSSL_DECODER_CTX_set_cleanup() return 1 on success, or 0 on
failure.
OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data()
and OSSL_DECODER_CTX_get_cleanup() return the current pointers to the
constructor, the constructor data and the cleanup functions,
respectively.
OSSL_DECODER_CTX_num_decoders() returns the current number of decoders.
It returns 0 if ctx is NULL.
OSSL_DECODER_export() returns 1 on success, or 0 on failure.
OSSL_DECODER_INSTANCE_decoder() returns an OSSL_DECODER pointer on
success, or NULL on failure.
OSSL_DECODER_INSTANCE_decoder_ctx() returns a provider context pointer
on success, or NULL on failure.
SEE ALSO
provider(7), OSSL_DECODER(3), OSSL_DECODER_from_bio(3)
HISTORY
The functions described here were added in OpenSSL 3.0.
COPYRIGHT
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>.
3.0.12 2023-05-07 OSSL_DECODER_CTX(3)