Ubuntu Manpage: OSSL_ENCODER_CTX, OSSL_ENCODER_CTX_new, OSSL_ENCODER_settable_ctx

Provided by: libssl-doc_3.0.5-2ubuntu1_all

NAME

       OSSL_ENCODER_CTX, OSSL_ENCODER_CTX_new, OSSL_ENCODER_settable_ctx_params,
       OSSL_ENCODER_CTX_set_params, OSSL_ENCODER_CTX_free, OSSL_ENCODER_CTX_set_selection,
       OSSL_ENCODER_CTX_set_output_type, OSSL_ENCODER_CTX_set_output_structure,
       OSSL_ENCODER_CTX_add_encoder, OSSL_ENCODER_CTX_add_extra,
       OSSL_ENCODER_CTX_get_num_encoders, OSSL_ENCODER_INSTANCE,
       OSSL_ENCODER_INSTANCE_get_encoder, OSSL_ENCODER_INSTANCE_get_encoder_ctx,
       OSSL_ENCODER_INSTANCE_get_output_type, OSSL_ENCODER_INSTANCE_get_output_structure,
       OSSL_ENCODER_CONSTRUCT, OSSL_ENCODER_CLEANUP, OSSL_ENCODER_CTX_set_construct,
       OSSL_ENCODER_CTX_set_construct_data, OSSL_ENCODER_CTX_set_cleanup - Encoder context
       routines

SYNOPSIS

        #include <openssl/encoder.h>

        typedef struct ossl_encoder_ctx_st OSSL_ENCODER_CTX;

        OSSL_ENCODER_CTX *OSSL_ENCODER_CTX_new();
        const OSSL_PARAM *OSSL_ENCODER_settable_ctx_params(OSSL_ENCODER *encoder);
        int OSSL_ENCODER_CTX_set_params(OSSL_ENCODER_CTX *ctx,
                                        const OSSL_PARAM params[]);
        void OSSL_ENCODER_CTX_free(OSSL_ENCODER_CTX *ctx);

        int OSSL_ENCODER_CTX_set_selection(OSSL_ENCODER_CTX *ctx, int selection);
        int OSSL_ENCODER_CTX_set_output_type(OSSL_ENCODER_CTX *ctx,
                                             const char *output_type);
        int OSSL_ENCODER_CTX_set_output_structure(OSSL_ENCODER_CTX *ctx,
                                                  const char *output_structure);

        int OSSL_ENCODER_CTX_add_encoder(OSSL_ENCODER_CTX *ctx, OSSL_ENCODER *encoder);
        int OSSL_ENCODER_CTX_add_extra(OSSL_ENCODER_CTX *ctx,
                                       OSSL_LIB_CTX *libctx, const char *propq);
        int OSSL_ENCODER_CTX_get_num_encoders(OSSL_ENCODER_CTX *ctx);

        typedef struct ossl_encoder_instance_st OSSL_ENCODER_INSTANCE;
        OSSL_ENCODER *
        OSSL_ENCODER_INSTANCE_get_encoder(OSSL_ENCODER_INSTANCE *encoder_inst);
        void *
        OSSL_ENCODER_INSTANCE_get_encoder_ctx(OSSL_ENCODER_INSTANCE *encoder_inst);
        const char *
        OSSL_ENCODER_INSTANCE_get_output_type(OSSL_ENCODER_INSTANCE *encoder_inst);
        const char *
        OSSL_ENCODER_INSTANCE_get_output_structure(OSSL_ENCODER_INSTANCE *encoder_inst);

        typedef const void *OSSL_ENCODER_CONSTRUCT(OSSL_ENCODER_INSTANCE *encoder_inst,
                                                   void *construct_data);
        typedef void OSSL_ENCODER_CLEANUP(void *construct_data);

        int OSSL_ENCODER_CTX_set_construct(OSSL_ENCODER_CTX *ctx,
                                           OSSL_ENCODER_CONSTRUCT *construct);
        int OSSL_ENCODER_CTX_set_construct_data(OSSL_ENCODER_CTX *ctx,
                                                void *construct_data);
        int OSSL_ENCODER_CTX_set_cleanup(OSSL_ENCODER_CTX *ctx,
                                         OSSL_ENCODER_CLEANUP *cleanup);

DESCRIPTION

Encoding an input object to the desired encoding may be done with a chain of encoder
implementations, which means that the output from one encoder may be the input for the
next in the chain. The OSSL_ENCODER_CTX holds all the data about these encoders. This
allows having generic format encoders such as DER to PEM, as well as more specialized
encoders like RSA to DER.

The final output type must be given, and a chain of encoders must end with an
implementation that produces that output type.

At the beginning of the encoding process, a contructor provided by the caller is called to
ensure that there is an appropriate provider-side object to start with. The constructor
is set with OSSL_ENCODER_CTX_set_construct().

OSSL_ENCODER_INSTANCE is an opaque structure that contains data about the encoder that is
going to be used, and that may be useful for the constructor. There are some functions to
extract data from this type, described in "Constructor" below.

Functions
OSSL_ENCODER_CTX_new() creates a OSSL_ENCODER_CTX.

OSSL_ENCODER_settable_ctx_params() returns an OSSL_PARAM(3) array of parameter
descriptors.

OSSL_ENCODER_CTX_set_params() attempts to set parameters specified with an OSSL_PARAM(3)
array params. Parameters that the implementation doesn't recognise should be ignored.

OSSL_ENCODER_CTX_free() frees the given context ctx.

OSSL_ENCODER_CTX_add_encoder() populates the OSSL_ENCODER_CTX ctx with a encoder, to be
used to encode an input object.

OSSL_ENCODER_CTX_add_extra() finds encoders that further encodes output from already added
encoders, and adds them as well. This is used to build encoder chains.

OSSL_ENCODER_CTX_set_output_type() sets the ending output type. This must be specified,
and determines if a complete encoder chain is available.

OSSL_ENCODER_CTX_set_output_structure() sets the desired output structure. This may be
used to determines what encoder implementations may be used. Depending on the type of
object being encoded, the output structure may not be relevant.

OSSL_ENCODER_CTX_get_num_encoders() gets the number of encoders currently added to the
context ctx.

OSSL_ENCODER_CTX_set_construct() sets the constructor construct.

OSSL_ENCODER_CTX_set_construct_data() sets the constructor data that is passed to the
constructor every time it's called.

OSSL_ENCODER_CTX_set_cleanup() sets the constructor data cleanup function. This is called
by OSSL_ENCODER_CTX_free(3).

Constructor
A OSSL_ENCODER_CONSTRUCT gets the following arguments:

encoder_inst
The OSSL_ENCODER_INSTANCE for the encoder from which the constructor gets its data.

construct_data
The pointer that was set with OSSL_ENCODE_CTX_set_construct_data().

The constructor is expected to return a valid (non-NULL) pointer to a provider-native
object that can be used as first input of an encoding chain, or NULL to indicate that an
error has occured.

These utility functions may be used by a constructor:

OSSL_ENCODER_INSTANCE_get_encoder() can be used to get the encoder implementation of the
encoder instance encoder_inst.

OSSL_ENCODER_INSTANCE_get_encoder_ctx() can be used to get the encoder implementation's
provider context of the encoder instance encoder_inst.

OSSL_ENCODER_INSTANCE_get_output_type() can be used to get the output type for the encoder
implementation of the encoder instance encoder_inst. This will never be NULL.

OSSL_ENCODER_INSTANCE_get_output_structure() can be used to get the output structure for
the encoder implementation of the encoder instance encoder_inst. This may be NULL.

RETURN VALUES

       OSSL_ENCODER_CTX_new() returns a pointer to a OSSL_ENCODER_CTX, or NULL if the context
       structure couldn't be allocated.

       OSSL_ENCODER_settable_ctx_params() returns an OSSL_PARAM(3) array, or NULL if none is
       available.

       OSSL_ENCODER_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_ENCODER_CTX_add_encoder(), OSSL_ENCODER_CTX_add_extra(),
       OSSL_ENCODER_CTX_set_construct(), OSSL_ENCODER_CTX_set_construct_data() and
       OSSL_ENCODER_CTX_set_cleanup() return 1 on success, or 0 on failure.

       OSSL_ENCODER_CTX_get_num_encoders() returns the current number of encoders.  It returns 0
       if ctx is NULL.

       OSSL_ENCODER_INSTANCE_get_encoder() returns an OSSL_ENCODER pointer on success, or NULL on
       failure.

       OSSL_ENCODER_INSTANCE_get_encoder_ctx() returns a provider context pointer on success, or
       NULL on failure.

       OSSL_ENCODER_INSTANCE_get_output_type() returns a string with the name of the input type,
       if relevant.  NULL is a valid returned value.

       OSSL_ENCODER_INSTANCE_get_output_type() returns a string with the name of the output type.

       OSSL_ENCODER_INSTANCE_get_output_structure() returns a string with the name of the output
       structure.

HISTORY

       The functions described here were added in OpenSSL 3.0.

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