Provided by: openssl_3.0.5-2ubuntu1_amd64 
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 arrays via OSSL_ALGORITHM 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 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 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 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 diables 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 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>.