provider-kdf - The KDF library <-> provider functions
#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[]);
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.
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.
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.
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.
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.
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.
provider(7),
life_cycle-kdf(7),
EVP_KDF(3).
The provider KDF interface was introduced in OpenSSL 3.0.
Copyright 2020-2023 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>.