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PROVIDER-KDF(7ossl)                 OpenSSL                PROVIDER-KDF(7ossl)



NAME

       provider-kdf - The KDF library <-> provider functions


SYNOPSIS

        #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_kdf_newctx(void *provctx);
        void OSSL_FUNC_kdf_freectx(void *kctx);
        void *OSSL_FUNC_kdf_dupctx(void *src);

        /* Encryption/decryption */
        int OSSL_FUNC_kdf_reset(void *kctx);
        int OSSL_FUNC_kdf_derive(void *kctx, unsigned char *key, size_t keylen,
                                 const OSSL_PARAM params[]);

        /* KDF parameter descriptors */
        const OSSL_PARAM *OSSL_FUNC_kdf_gettable_params(void *provctx);
        const OSSL_PARAM *OSSL_FUNC_kdf_gettable_ctx_params(void *kcxt, void *provctx);
        const OSSL_PARAM *OSSL_FUNC_kdf_settable_ctx_params(void *kcxt, void *provctx);

        /* KDF parameters */
        int OSSL_FUNC_kdf_get_params(OSSL_PARAM params[]);
        int OSSL_FUNC_kdf_get_ctx_params(void *kctx, OSSL_PARAM params[]);
        int OSSL_FUNC_kdf_set_ctx_params(void *kctx, const OSSL_PARAM params[]);


DESCRIPTION

       This documentation is primarily aimed at provider authors. See
       provider(7) for further information.

       The KDF operation enables providers to implement KDF algorithms and
       make them available to applications via the API functions
       EVP_KDF_CTX_reset(3), and EVP_KDF_derive(3).

       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_kdf_newctx()
       has these:

        typedef void *(OSSL_FUNC_kdf_newctx_fn)(void *provctx);
        static ossl_inline OSSL_FUNC_kdf_newctx_fn
            OSSL_FUNC_kdf_newctx(const OSSL_DISPATCH *opf);

       OSSL_DISPATCH(3) array entries are identified by numbers that are
       provided as macros in openssl-core_dispatch.h(7), as follows:

        OSSL_FUNC_kdf_newctx               OSSL_FUNC_KDF_NEWCTX
        OSSL_FUNC_kdf_freectx              OSSL_FUNC_KDF_FREECTX
        OSSL_FUNC_kdf_dupctx               OSSL_FUNC_KDF_DUPCTX

        OSSL_FUNC_kdf_reset                OSSL_FUNC_KDF_RESET
        OSSL_FUNC_kdf_derive               OSSL_FUNC_KDF_DERIVE

        OSSL_FUNC_kdf_get_params           OSSL_FUNC_KDF_GET_PARAMS
        OSSL_FUNC_kdf_get_ctx_params       OSSL_FUNC_KDF_GET_CTX_PARAMS
        OSSL_FUNC_kdf_set_ctx_params       OSSL_FUNC_KDF_SET_CTX_PARAMS

        OSSL_FUNC_kdf_gettable_params      OSSL_FUNC_KDF_GETTABLE_PARAMS
        OSSL_FUNC_kdf_gettable_ctx_params  OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS
        OSSL_FUNC_kdf_settable_ctx_params  OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS

       A KDF algorithm implementation may not implement all of these
       functions.  In order to be a consistent set of functions, at least the
       following functions must be implemented: OSSL_FUNC_kdf_newctx(),
       OSSL_FUNC_kdf_freectx(), OSSL_FUNC_kdf_set_ctx_params(),
       OSSL_FUNC_kdf_derive().  All other functions are optional.

   Context Management Functions
       OSSL_FUNC_kdf_newctx() should create and return a pointer to a provider
       side structure for holding context information during a KDF operation.
       A pointer to this context will be passed back in a number of the other
       KDF operation function calls.  The parameter provctx is the provider
       context generated during provider initialisation (see provider(7)).

       OSSL_FUNC_kdf_freectx() is passed a pointer to the provider side KDF
       context in the kctx parameter.  If it receives NULL as kctx value, it
       should not do anything other than return.  This function should free
       any resources associated with that context.

       OSSL_FUNC_kdf_dupctx() should duplicate the provider side KDF context
       in the kctx parameter and return the duplicate copy.

   Encryption/Decryption Functions
       OSSL_FUNC_kdf_reset() initialises a KDF operation given a provider side
       KDF context in the kctx parameter.

       OSSL_FUNC_kdf_derive() performs the KDF operation after processing the
       params as per OSSL_FUNC_kdf_set_ctx_params().  The kctx parameter
       contains a pointer to the provider side context.  The resulting key of
       the desired keylen should be written to key.  If the algorithm does not
       support the requested keylen the function must return error.

   KDF Parameters
       See OSSL_PARAM(3) for further details on the parameters structure used
       by these functions.

       OSSL_FUNC_kdf_get_params() gets details of parameter values associated
       with the provider algorithm and stores them in params.

       OSSL_FUNC_kdf_set_ctx_params() sets KDF parameters associated with the
       given provider side KDF context kctx to params.  Any parameter settings
       are additional to any that were previously set.  Passing NULL for
       params should return true.

       OSSL_FUNC_kdf_get_ctx_params() retrieves gettable parameter values
       associated with the given provider side KDF context kctx and stores
       them in params.  Passing NULL for params should return true.

       OSSL_FUNC_kdf_gettable_params(), OSSL_FUNC_kdf_gettable_ctx_params(),
       and OSSL_FUNC_kdf_settable_ctx_params() all return constant
       OSSL_PARAM(3) arrays as descriptors of the parameters that
       OSSL_FUNC_kdf_get_params(), OSSL_FUNC_kdf_get_ctx_params(), and
       OSSL_FUNC_kdf_set_ctx_params() can handle, respectively.
       OSSL_FUNC_kdf_gettable_ctx_params() and
       OSSL_FUNC_kdf_settable_ctx_params() will return the parameters
       associated with the provider side context kctx in its current state if
       it is not NULL.  Otherwise, they return the parameters associated with
       the provider side algorithm provctx.

       Parameters currently recognised by built-in KDFs are as follows. Not
       all parameters are relevant to, or are understood by all KDFs:

       "size" (OSSL_KDF_PARAM_SIZE) <unsigned integer>
           Gets the output size from the associated KDF ctx.  If the algorithm
           produces a variable amount of output, SIZE_MAX should be returned.
           If the input parameters required to calculate the fixed output size
           have not yet been supplied, 0 should be returned indicating an
           error.

       "key" (OSSL_KDF_PARAM_KEY) <octet string>
           Sets the key in the associated KDF ctx.

       "secret" (OSSL_KDF_PARAM_SECRET) <octet string>
           Sets the secret in the associated KDF ctx.

       "pass" (OSSL_KDF_PARAM_PASSWORD) <octet string>
           Sets the password in the associated KDF ctx.

       "cipher" (OSSL_KDF_PARAM_CIPHER) <UTF8 string>
       "digest" (OSSL_KDF_PARAM_DIGEST) <UTF8 string>
       "mac" (OSSL_KDF_PARAM_MAC) <UTF8 string>
           Sets the name of the underlying cipher, digest or MAC to be used.
           It must name a suitable algorithm for the KDF that's being used.

       "maclen" (OSSL_KDF_PARAM_MAC_SIZE) <octet string>
           Sets the length of the MAC in the associated KDF ctx.

       "properties" (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>
           Sets the properties to be queried when trying to fetch the
           underlying algorithm.  This must be given together with the
           algorithm naming parameter to be considered valid.

       "iter" (OSSL_KDF_PARAM_ITER) <unsigned integer>
           Sets the number of iterations in the associated KDF ctx.

       "mode" (OSSL_KDF_PARAM_MODE) <UTF8 string>
           Sets the mode in the associated KDF ctx.

       "pkcs5" (OSSL_KDF_PARAM_PKCS5) <integer>
           Enables or disables the SP800-132 compliance checks.  A mode of 0
           enables the compliance checks.

           The checks performed are:

           - the iteration count is at least 1000.
           - the salt length is at least 128 bits.
           - the derived key length is at least 112 bits.

       "ukm" (OSSL_KDF_PARAM_UKM) <octet string>
           Sets an optional random string that is provided by the sender
           called "partyAInfo".  In CMS this is the user keying material.

       "cekalg" (OSSL_KDF_PARAM_CEK_ALG) <UTF8 string>
           Sets the CEK wrapping algorithm name in the associated KDF ctx.

       "n" (OSSL_KDF_PARAM_SCRYPT_N) <unsigned integer>
           Sets the scrypt work factor parameter N in the associated KDF ctx.

       "r" (OSSL_KDF_PARAM_SCRYPT_R) <unsigned integer>
           Sets the scrypt work factor parameter r in the associated KDF ctx.

       "p" (OSSL_KDF_PARAM_SCRYPT_P) <unsigned integer>
           Sets the scrypt work factor parameter p in the associated KDF ctx.

       "maxmem_bytes" (OSSL_KDF_PARAM_SCRYPT_MAXMEM) <unsigned integer>
           Sets the scrypt work factor parameter maxmem in the associated KDF
           ctx.

       "prefix" (OSSL_KDF_PARAM_PREFIX) <octet string>
           Sets the prefix string using by the TLS 1.3 version of HKDF in the
           associated KDF ctx.

       "label" (OSSL_KDF_PARAM_LABEL) <octet string>
           Sets the label string using by the TLS 1.3 version of HKDF in the
           associated KDF ctx.

       "data" (OSSL_KDF_PARAM_DATA) <octet string>
           Sets the context string using by the TLS 1.3 version of HKDF in the
           associated KDF ctx.

       "info" (OSSL_KDF_PARAM_INFO) <octet string>
           Sets the optional shared info in the associated KDF ctx.

       "seed" (OSSL_KDF_PARAM_SEED) <octet string>
           Sets the IV in the associated KDF ctx.

       "xcghash" (OSSL_KDF_PARAM_SSHKDF_XCGHASH) <octet string>
           Sets the xcghash in the associated KDF ctx.

       "session_id" (OSSL_KDF_PARAM_SSHKDF_SESSION_ID) <octet string>
           Sets the session ID in the associated KDF ctx.

       "type" (OSSL_KDF_PARAM_SSHKDF_TYPE) <UTF8 string>
           Sets the SSH KDF type parameter in the associated KDF ctx.  There
           are six supported types:

           EVP_KDF_SSHKDF_TYPE_INITIAL_IV_CLI_TO_SRV
               The Initial IV from client to server.  A single char of value
               65 (ASCII char 'A').

           EVP_KDF_SSHKDF_TYPE_INITIAL_IV_SRV_TO_CLI
               The Initial IV from server to client A single char of value 66
               (ASCII char 'B').

           EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_CLI_TO_SRV
               The Encryption Key from client to server A single char of value
               67 (ASCII char 'C').

           EVP_KDF_SSHKDF_TYPE_ENCRYPTION_KEY_SRV_TO_CLI
               The Encryption Key from server to client A single char of value
               68 (ASCII char 'D').

           EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_CLI_TO_SRV
               The Integrity Key from client to server A single char of value
               69 (ASCII char 'E').

           EVP_KDF_SSHKDF_TYPE_INTEGRITY_KEY_SRV_TO_CLI
               The Integrity Key from client to server A single char of value
               70 (ASCII char 'F').

       "constant" (OSSL_KDF_PARAM_CONSTANT) <octet string>
           Sets the constant value in the associated KDF ctx.

       "id" (OSSL_KDF_PARAM_PKCS12_ID) <integer>
           Sets the intended usage of the output bits in the associated KDF
           ctx.  It is defined as per RFC 7292 section B.3.


RETURN VALUES

       OSSL_FUNC_kdf_newctx() and OSSL_FUNC_kdf_dupctx() should return the
       newly created provider side KDF context, or NULL on failure.

       OSSL_FUNC_kdf_derive(), OSSL_FUNC_kdf_get_params(),
       OSSL_FUNC_kdf_get_ctx_params() and OSSL_FUNC_kdf_set_ctx_params()
       should return 1 for success or 0 on error.

       OSSL_FUNC_kdf_gettable_params(), OSSL_FUNC_kdf_gettable_ctx_params()
       and OSSL_FUNC_kdf_settable_ctx_params() should return a constant
       OSSL_PARAM(3) array, or NULL if none is offered.


NOTES

       The KDF life-cycle is described in life_cycle-kdf(7).  Providers should
       ensure that the various transitions listed there are supported.  At
       some point the EVP layer will begin enforcing the listed transitions.


SEE ALSO

       provider(7), life_cycle-kdf(7), EVP_KDF(3).


HISTORY

       The provider KDF interface was introduced in OpenSSL 3.0.


COPYRIGHT

       Copyright 2020-2022 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>.

3.3.2                             2024-09-04               PROVIDER-KDF(7ossl)

openssl 3.3.2 - Generated Tue Oct 1 18:06:09 CDT 2024
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