PROVIDER-KEYMGMT(7)

NAME
provider-keymgmt - The KEYMGMT library <-> provider functions

SYNOPSIS
 #include <openssl/core_numbers.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.
  */

 /* Key object (keydata) creation and destruction */
 void *OP_keymgmt_new(void *provctx);
 void OP_keymgmt_free(void *keydata);

 /* Key object information */
 int OP_keymgmt_get_params(void *keydata, OSSL_PARAM params[]);
 const OSSL_PARAM *OP_keymgmt_gettable_params(void);
 int OP_keymgmt_set_params(void *keydata, const OSSL_PARAM params[]);
 const OSSL_PARAM *OP_keymgmt_settable_params(void);

 /* Key object content checks */
 int OP_keymgmt_has(void *keydata, int selection);
 int OP_keymgmt_match(const void *keydata1, const void *keydata2,
                      int selection);

 /* Discovery of supported operations */
 const char *OP_keymgmt_query_operation_name(int operation_id);

 /* Key object import and export functions */
 int OP_keymgmt_import(int selection, void *keydata, const OSSL_PARAM params[]);
 const OSSL_PARAM *OP_keymgmt_import_types(int selection);
 int OP_keymgmt_export(int selection, void *keydata,
                       OSSL_CALLBACK *param_cb, void *cbarg);
 const OSSL_PARAM *OP_keymgmt_export_types(int selection);

 /* Key object copy */
 int OP_keymgmt_copy(void *keydata_to, const void *keydata_from, int selection);

 /* Key object validation */
 int OP_keymgmt_validate(void *keydata, int selection);

DESCRIPTION
The KEYMGMT operation doesn't have much public visibility in OpenSSL libraries, it's rather an internal operation that's designed to work in tandem with operations that use private/public key pairs.

Because the KEYMGMT operation shares knowledge with the operations it works with in tandem, they must belong to the same provider. The OpenSSL libraries will ensure that they do.

The primary responsibility of the KEYMGMT operation is to hold the provider side key data for the OpenSSL library EVP_PKEY structure.

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_{name}_fn, and a helper function to retrieve the function pointer from a OSSL_DISPATCH element named OSSL_get_{name}. For example, the "function" OP_keymgmt_new() has these:

 typedef void *(OSSL_OP_keymgmt_new_fn)(void *provctx);
 static ossl_inline OSSL_OP_keymgmt_new_fn
     OSSL_get_OP_keymgmt_new(const OSSL_DISPATCH *opf);

OSSL_DISPATCH arrays are indexed by numbers that are provided as macros in openssl-core_numbers.h(7), as follows:

 OP_keymgmt_new                  OSSL_FUNC_KEYMGMT_NEW
 OP_keymgmt_free                 OSSL_FUNC_KEYMGMT_FREE

 OP_keymgmt_get_params           OSSL_FUNC_KEYMGMT_GET_PARAMS
 OP_keymgmt_gettable_params      OSSL_FUNC_KEYMGMT_GETTABLE_PARAMS
 OP_keymgmt_set_params           OSSL_FUNC_KEYMGMT_SET_PARAMS
 OP_keymgmt_settable_params      OSSL_FUNC_KEYMGMT_SETTABLE_PARAMS

 OP_keymgmt_query_operation_name OSSL_FUNC_KEYMGMT_QUERY_OPERATION_NAME

 OP_keymgmt_has                  OSSL_FUNC_KEYMGMT_HAS
 OP_keymgmt_validate             OSSL_FUNC_KEYMGMT_VALIDATE
 OP_keymgmt_match                OSSL_FUNC_KEYMGMT_MATCH

 OP_keymgmt_import               OSSL_FUNC_KEYMGMT_IMPORT
 OP_keymgmt_import_types         OSSL_FUNC_KEYMGMT_IMPORT_TYPES
 OP_keymgmt_export               OSSL_FUNC_KEYMGMT_EXPORT
 OP_keymgmt_export_types         OSSL_FUNC_KEYMGMT_EXPORT_TYPES

 OP_keymgmt_copy                 OSSL_FUNC_KEYMGMT_COPY

  Key Objects
A key object is a collection of data for an asymmetric key, and is represented as keydata in this manual.

The exact contents of a key object are defined by the provider, and it is assumed that different operations in one and the same provider use the exact same structure to represent this collection of data, so that for example, a key object that has been created using the KEYMGMT interface that we document here can be passed as is to other provider operations, such as OP_signature_sign_init() (see provider-signature(7)).

With some of the KEYMGMT functions, it's possible to select a specific subset of data to handle, governed by the bits in a selection indicator. The bits are:

OSSL_KEYMGMT_SELECT_PRIVATE_KEY
    Indicating that the private key data in a key object should be considered.

OSSL_KEYMGMT_SELECT_PUBLIC_KEY
    Indicating that the public key data in a key object should be considered.

OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS
    Indicating that the domain parameters in a key object should be considered.

OSSL_KEYMGMT_SELECT_OTHER_PARAMETERS
    Indicating that other parameters in a key object should be considered.

    Other parameters are key parameters that don't fit any other classification. In other words, this particular selector bit works as a last resort bit bucket selector.

Some selector bits have also been combined for easier use:

OSSL_KEYMGMT_SELECT_ALL_PARAMETERS
    Indicating that all key object parameters should be considered, regardless of their more granular classification.

    This is a combination of OSSL_KEYMGMT_SELECT_DOMAIN_PARAMETERS and OSSL_KEYMGMT_SELECT_OTHER_PARAMETERS.

OSSL_KEYMGMT_SELECT_KEYPAIR
    Indicating that both the whole key pair in a key object should be considered, i.e. the combination of public and private key.

    This is a combination of OSSL_KEYMGMT_SELECT_PRIVATE_KEY and OSSL_KEYMGMT_SELECT_PUBLIC_KEY.

OSSL_KEYMGMT_SELECT_ALL
    Indicating that everything in a key object should be considered.

The exact interpretation of those bits or how they combine is left to each function where you can specify a selector.

  Constructing and Destructing Functions
OP_keymgmt_new() should create a provider side key object. The provider context provctx is passed and may be incorporated in the key object, but that is not mandatory.

OP_keymgmt_free() should free the passed keydata.

The constructor and destructor are mandatory, a KEYMGMT implementation without them will not be accepted.

  Key Object Information Functions
OP_keymgmt_get_params() should extract information data associated with the given keydata, see "Information Parameters".

OP_keymgmt_gettable_params() should return a constant array of descriptor OSSL_PARAM, for parameters that OP_keymgmt_get_params() can handle.

If OP_keymgmt_gettable_params() is present, OP_keymgmt_get_params() must also be present, and vice versa.

OP_keymgmt_set_params() should update information data associated with the given keydata, see "Information Parameters".

OP_keymgmt_settable_params() should return a constant array of descriptor OSSL_PARAM, for parameters that OP_keymgmt_set_params() can handle.

If OP_keymgmt_settable_params() is present, OP_keymgmt_set_params() must also be present, and vice versa.

  Key Object Checking Functions
OP_keymgmt_query_operation_name() should return the name of the supported algorithm for the operation operation_id. This is similar to provider_query_operation() (see provider-base(7)), but only works as an advisory. If this function is not present, or returns NULL, the caller is free to assume that there's an algorithm from the same provider, of the same name as the one used to fetch the keymgmt and try to use that.

OP_keymgmt_has() should check whether the given keydata contains the subsets of data indicated by the selector. A combination of several selector bits must consider all those subsets, not just one. An implementation is, however, free to consider an empty subset of data to still be a valid subset.

OP_keymgmt_validate() should check if the keydata contains valid data subsets indicated by selection. Some combined selections of data subsets may cause validation of the combined data. For example, the combination of OSSL_KEYMGMT_SELECT_PRIVATE_KEY and OSSL_KEYMGMT_SELECT_PUBLIC_KEY (or OSSL_KEYMGMT_SELECT_KEYPAIR for short) is expected to check that the pairwise consistency of keydata is valid.

OP_keymgmt_match() should check if the data subset indicated by selection in keydata1 and keydata2 match. It is assumed that the caller has ensured that keydata1 and keydata2 are both owned by the implementation of this function.

  Key Object Import, Export and Copy Functions
OP_keymgmt_import() should import data indicated by selection into keydata with values taken from the OSSL_PARAM array params.

OP_keymgmt_export() should extract values indicated by selection from keydata, create an OSSL_PARAM array with them and call param_cb with that array as well as the given cbarg.

OP_keymgmt_import_types() should return a constant array of descriptor OSSL_PARAM for data indicated by selection, for parameters that OP_keymgmt_import() can handle.

OP_keymgmt_export_types() should return a constant array of descriptor OSSL_PARAM for data indicated by selection, that the OP_keymgmt_export() callback can expect to receive.

OP_keymgmt_copy() should copy data subsets indicated by selection from keydata_from to keydata_to. It is assumed that the caller has ensured that keydata_to and keydata_from are both owned by the implementation of this function.

  Built-in RSA Import/Export Types
The following Import/Export types are available for the built-in RSA algorithm:

"n" (OSSL_PKEY_PARAM_RSA_N) <integer>
    The RSA "n" value.

"e" (OSSL_PKEY_PARAM_RSA_E) <integer>
    The RSA "e" value.

"d" (OSSL_PKEY_PARAM_RSA_D) <integer>
    The RSA "d" value.

"rsa-factor" (OSSL_PKEY_PARAM_RSA_FACTOR) <integer>
    An RSA factor. In 2 prime RSA these are often known as "p" or "q". This value may be repeated up to 10 times in a single key.

"rsa-exponent" (OSSL_PKEY_PARAM_RSA_EXPONENT) <integer>
    An RSA CRT (Chinese Remainder Theorem) exponent. This value may be repeated up to 10 times in a single key.

"rsa-coefficient" (OSSL_PKEY_PARAM_RSA_COEFFICIENT) <integer>
    An RSA CRT (Chinese Remainder Theorem) coefficient. This value may be repeated up to 9 times in a single key.

  Built-in DSA and Diffie-Hellman Import/Export Types
The following Import/Export types are available for the built-in DSA and Diffie-Hellman algorithms:

"pub" (OSSL_PKEY_PARAM_PUB_KEY) <integer> or <octet string>
    The public key value.

"priv" (OSSL_PKEY_PARAM_PRIV_KEY) <integer> or <octet string>
    The private key value.

"p" (OSSL_PKEY_PARAM_FFC_P) <integer>
    A DSA or Diffie-Hellman "p" value.

"q" (OSSL_PKEY_PARAM_FFC_Q) <integer>
    A DSA or Diffie-Hellman "q" value.

"g" (OSSL_PKEY_PARAM_FFC_G) <integer>
    A DSA or Diffie-Hellman "g" value.

  Built-in X25519, X448, ED25519 and ED448 Import/Export Types
The following Import/Export types are available for the built-in X25519, X448, ED25519 and X448 algorithms:

"pub" (OSSL_PKEY_PARAM_PUB_KEY) <octet string>
    The public key value.

"priv" (OSSL_PKEY_PARAM_PRIV_KEY) <octet string>
    The private key value.

  Information Parameters
See OSSL_PARAM(3) for further details on the parameters structure.

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

"bits" (OSSL_PKEY_PARAM_BITS) <integer>
    The value should be the cryptographic length of the cryptosystem to which the key belongs, in bits. The definition of cryptographic length is specific to the key cryptosystem.

"max-size" (OSSL_PKEY_PARAM_MAX_SIZE) <integer>
    The value should be the maximum size that a caller should allocate to safely store a signature (called sig in provider-signature(7)), the result of asymmmetric encryption / decryption (out in provider-asym_cipher(7), a derived secret (secret in provider-keyexch(7), and similar data).

    Because an EVP_KEYMGMT method is always tightly bound to another method (signature, asymmetric cipher, key exchange, ...) and must be of the same provider, this number only needs to be synchronised with the dimensions handled in the rest of the same provider.

"security-bits" (OSSL_PKEY_PARAM_SECURITY_BITS) <integer>
    The value should be the number of security bits of the given key. Bits of security is defined in SP800-57.

"use-cofactor-flag" (OSSL_PKEY_PARAM_USE_COFACTOR_FLAG, OSSL_PKEY_PARAM_USE_COFACTOR_ECDH) <integer>
    The value should be either 1 or 0, to respectively enable or disable use of the cofactor in operations using this key.

    In the context of a key that can be used to perform an Elliptic Curve Diffie-Hellman key exchange, this parameter can be used to mark a requirement for using the Cofactor Diffie-Hellman (CDH) variant of the key exchange algorithm.

    See also provider-keyexch(7) for the related OSSL_EXCHANGE_PARAM_EC_ECDH_COFACTOR_MODE parameter that can be set on a per-operation basis.

RETURN VALUES
OP_keymgmt_new() should return a valid reference to the newly created provider side key object, or NULL on failure.

OP_keymgmt_import(), OP_keymgmt_export(), OP_keymgmt_get_params() and OP_keymgmt_set_params() should return 1 for success or 0 on error.

OP_keymgmt_validate() should return 1 on successful validation, or 0 on failure.

OP_keymgmt_has() should return 1 if all the selected data subsets are contained in the given keydata or 0 otherwise.

OP_keymgmt_query_operation_name() should return a pointer to a string matching the requested operation, or NULL if the same name used to fetch the keymgmt applies.

OP_keymgmt_gettable_params() and OP_keymgmt_settable_params() OP_keymgmt_import_types(), OP_keymgmt_export_types() should always return a constant OSSL_PARAM array.

SEE ALSO
provider(7)

HISTORY
The KEYMGMT interface was introduced in OpenSSL 3.0.

COPYRIGHT
Copyright 2019-2020 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>.