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PROVIDER-ENCODER(7ossl)              OpenSSL             PROVIDER-ENCODER(7ossl)


       provider-encoder - The OSSL_ENCODER library <-> provider functions


        #include <openssl/core_dispatch.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.

        /* Encoder parameter accessor and descriptor */
        const OSSL_PARAM *OSSL_FUNC_encoder_gettable_params(void *provctx);
        int OSSL_FUNC_encoder_get_params(OSSL_PARAM params[]);

        /* Functions to construct / destruct / manipulate the encoder context */
        void *OSSL_FUNC_encoder_newctx(void *provctx);
        void OSSL_FUNC_encoder_freectx(void *ctx);
        int OSSL_FUNC_encoder_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
        const OSSL_PARAM *OSSL_FUNC_encoder_settable_ctx_params(void *provctx);

        /* Functions to check selection support */
        int OSSL_FUNC_encoder_does_selection(void *provctx, int selection);

        /* Functions to encode object data */
        int OSSL_FUNC_encoder_encode(void *ctx, OSSL_CORE_BIO *out,
                                     const void *obj_raw,
                                     const OSSL_PARAM obj_abstract[],
                                     int selection,
                                     OSSL_PASSPHRASE_CALLBACK *cb,
                                     void *cbarg);

        /* Functions to import and free a temporary object to be encoded */
        void *OSSL_FUNC_encoder_import_object(void *ctx, int selection,
                                              const OSSL_PARAM params[]);
        void OSSL_FUNC_encoder_free_object(void *obj);


       We use the wide term "encode" in this manual.  This includes but is not
       limited to serialization.

       The ENCODER operation is a generic method to encode a provider-native
       object (obj_raw) or an object abstraction (object_abstract, see
       provider-object(7)) into an encoded form, and write the result to the
       given OSSL_CORE_BIO.  If the caller wants to get the encoded stream to
       memory, it should provide a BIO_s_mem(3) BIO.

       The encoder doesn't need to know more about the OSSL_CORE_BIO pointer
       than being able to pass it to the appropriate BIO upcalls (see "Core
       functions" in provider-base(7)).

       The ENCODER implementation may be part of a chain, where data is passed
       from one to the next.  For example, there may be an implementation to
       encode an object to DER (that object is assumed to be provider-native and
       thereby passed via obj_raw), and another one that encodes DER to PEM
       (that one would receive the DER encoding via obj_abstract).

       The encoding using the OSSL_PARAM(3) array form allows a encoder to be
       used for data that's been exported from another provider, and thereby
       allow them to exist independently of each other.

       The encoding using a provider side object can only be safely used with
       provider data coming from the same provider, for example keys with the
       KEYMGMT provider.

       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

       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_encoder_encode() has these:

        typedef int
            (OSSL_FUNC_encoder_encode_fn)(void *ctx, OSSL_CORE_BIO *out,
                                          const void *obj_raw,
                                          const OSSL_PARAM obj_abstract[],
                                          int selection,
                                          OSSL_PASSPHRASE_CALLBACK *cb, void *cbarg);
        static ossl_inline OSSL_FUNC_encoder_encode_fn
            OSSL_FUNC_encoder_encode(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_encoder_get_params          OSSL_FUNC_ENCODER_GET_PARAMS
        OSSL_FUNC_encoder_gettable_params     OSSL_FUNC_ENCODER_GETTABLE_PARAMS

        OSSL_FUNC_encoder_newctx              OSSL_FUNC_ENCODER_NEWCTX
        OSSL_FUNC_encoder_freectx             OSSL_FUNC_ENCODER_FREECTX
        OSSL_FUNC_encoder_set_ctx_params      OSSL_FUNC_ENCODER_SET_CTX_PARAMS
        OSSL_FUNC_encoder_settable_ctx_params OSSL_FUNC_ENCODER_SETTABLE_CTX_PARAMS

        OSSL_FUNC_encoder_does_selection      OSSL_FUNC_ENCODER_DOES_SELECTION

        OSSL_FUNC_encoder_encode              OSSL_FUNC_ENCODER_ENCODE

        OSSL_FUNC_encoder_import_object       OSSL_FUNC_ENCODER_IMPORT_OBJECT
        OSSL_FUNC_encoder_free_object         OSSL_FUNC_ENCODER_FREE_OBJECT

   Names and properties
       The name of an implementation should match the type of object it handles.
       For example, an implementation that encodes an RSA key should be named
       "RSA". Likewise, an implementation that further encodes DER should be
       named "DER".

       Properties can be used to further specify details about an

           This property is used to specify what type of output the
           implementation produces.

           This property is mandatory.

           OpenSSL providers recognize the following output types:

               An implementation with that output type outputs human readable
               text, making that implementation suitable for "-text" output in
               diverse openssl(1) commands.

           pem An implementation with that output type outputs PEM formatted

           der An implementation with that output type outputs DER formatted

               An implementation with that output type outputs MSBLOB formatted

           pvk An implementation with that output type outputs PVK formatted

           This property is used to specify the structure that is used for the
           encoded object.  An example could be "pkcs8", to specify explicitly
           that an object (presumably an asymmetric key pair, in this case) will
           be wrapped in a PKCS#8 structure as part of the encoding.

           This property is optional.

       The possible values of both these properties is open ended.  A provider
       may very well specify output types and structures that libcrypto doesn't
       know anything about.

   Subset selections
       Sometimes, an object has more than one subset of data that is interesting
       to treat separately or together.  It's possible to specify what subsets
       are to be encoded, with a set of bits selection that are passed in an

       This set of bits depend entirely on what kind of provider-side object is
       passed.  For example, those bits are assumed to be the same as those used
       with provider-keymgmt(7) (see "Key Objects" in provider-keymgmt(7)) when
       the object is an asymmetric keypair.

       ENCODER implementations are free to regard the selection as a set of
       hints, but must do so with care.  In the end, the output must make sense,
       and if there's a corresponding decoder, the resulting decoded object must
       match the original object that was encoded.

       OSSL_FUNC_encoder_does_selection() should tell if a particular
       implementation supports any of the combinations given by selection.

   Context functions
       OSSL_FUNC_encoder_newctx() returns a context to be used with the rest of
       the functions.

       OSSL_FUNC_encoder_freectx() frees the given ctx, if it was created by

       OSSL_FUNC_encoder_set_ctx_params() sets context data according to
       parameters from params that it recognises.  Unrecognised parameters
       should be ignored.  Passing NULL for params should return true.

       OSSL_FUNC_encoder_settable_ctx_params() returns a constant OSSL_PARAM(3)
       array describing the parameters that OSSL_FUNC_encoder_set_ctx_params()
       can handle.

       See OSSL_PARAM(3) for further details on the parameters structure used by
       OSSL_FUNC_encoder_set_ctx_params() and

   Import functions
       A provider-native object may be associated with a foreign provider, and
       may therefore be unsuitable for direct use with a given ENCODER
       implementation.  Provided that the foreign provider's implementation to
       handle the object has a function to export that object in OSSL_PARAM(3)
       array form, the ENCODER implementation should be able to import that
       array and create a suitable object to be passed to
       OSSL_FUNC_encoder_encode()'s obj_raw.

       OSSL_FUNC_encoder_import_object() should import the subset of params
       given with selection to create a provider-native object that can be
       passed as obj_raw to OSSL_FUNC_encoder_encode().

       OSSL_FUNC_encoder_free_object() should free the object that was created
       with OSSL_FUNC_encoder_import_object().

   Encoding functions
       OSSL_FUNC_encoder_encode() should take a provider-native object (in
       obj_raw) or an object abstraction (in obj_abstract), and should output
       the object in encoded form to the OSSL_CORE_BIO.  The selection bits, if
       relevant, should determine in greater detail what will be output.  The
       encoding functions also take an OSSL_PASSPHRASE_CALLBACK(3) function
       pointer along with a pointer to application data cbarg, which should be
       used when a pass phrase prompt is needed.

   Encoder operation parameters
       Operation parameters currently recognised by built-in encoders are as

       "cipher" (OSSL_ENCODER_PARAM_CIPHER) <UTF8 string>
           The name of the encryption cipher to be used when generating
           encrypted encoding.  This is used when encoding private keys, as well
           as other objects that need protection.

           If this name is invalid for the encoding implementation, the
           implementation should refuse to perform the encoding, i.e.
           OSSL_FUNC_encoder_encode_data() and OSSL_FUNC_encoder_encode_object()
           should return an error.

       "properties" (OSSL_ENCODER_PARAM_PROPERTIES) <UTF8 string>
           The properties to be queried when trying to fetch the algorithm given
           with the "cipher" parameter.  This must be given together with the
           "cipher" parameter to be considered valid.

           The encoding implementation isn't obligated to use this value.
           However, it is recommended that implementations that do not handle
           property strings return an error on receiving this parameter unless
           its value NULL or the empty string.

       "save-parameters" (OSSL_ENCODER_PARAM_SAVE_PARAMETERS) <integer>
           If set to 0 disables saving of key domain parameters. Default is 1.
           It currently has an effect only on DSA keys.

       Parameters currently recognised by the built-in pass phrase callback:

       "info" (OSSL_PASSPHRASE_PARAM_INFO) <UTF8 string>
           A string of information that will become part of the pass phrase
           prompt.  This could be used to give the user information on what kind
           of object it's being prompted for.


       OSSL_FUNC_encoder_newctx() returns a pointer to a context, or NULL on

       OSSL_FUNC_encoder_set_ctx_params() returns 1, unless a recognised
       parameter was invalid or caused an error, for which 0 is returned.

       OSSL_FUNC_encoder_settable_ctx_params() returns a pointer to an array of
       constant OSSL_PARAM(3) elements.

       OSSL_FUNC_encoder_does_selection() returns 1 if the encoder
       implementation supports any of the selection bits, otherwise 0.

       OSSL_FUNC_encoder_encode() returns 1 on success, or 0 on failure.




       The ENCODER interface was introduced in OpenSSL 3.0.


       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

3.0.8                              2023-02-07            PROVIDER-ENCODER(7ossl)

openssl 3.0.8 - Generated Wed Feb 8 16:01:43 CST 2023
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