Copyright Digital Equipment Corp. All rights reserved.
UnwrapKey
NAME
UnwrapKey,
CSSM_UnwrapKey,
CSP_UnwrapKey - Unwrap the wrapped key (CDSA)
SYNOPSIS
# include <cssm.h>
API:
CSSM_RETURN CSSMAPI CSSM_UnwrapKey
(CSSM_CC_HANDLE CCHandle,
const CSSM_KEY *PublicKey,
const CSSM_WRAP_KEY *WrappedKey,
uint32 KeyUsage,
uint32 KeyAttr,
const CSSM_DATA *KeyLabel,
const CSSM_RESOURCE_CONTROL_CONTEXT *CredAndAclEntry,
CSSM_KEY_PTR UnwrappedKey,
CSSM_DATA_PTR DescriptiveData)
SPI:
CSSM_RETURN CSSMCSPI CSP_UnwrapKey
(CSSM_CSP_HANDLE CSPHandle,
CSSM_CC_HANDLE CCHandle,
const CSSM_CONTEXT *Context,
const CSSM_KEY *PublicKey,
const CSSM_WRAP_KEY *WrappedKey,
uint32 KeyUsage,
uint32 KeyAttr,
const CSSM_DATA *KeyLabel,
const CSSM_RESOURCE_CONTROL_CONTEXT *CredAndAclEntry,
CSSM_KEY_PTR UnwrappedKey,
CSSM_DATA_PTR DescriptiveData,
CSSM_PRIVILEGE Privilege)
LIBRARY
Common Security Services Manager library (CDSA$INCSSM300_SHR.EXE)
API PARAMETERS
CCHandle (input)
The handle that describes the context of this cryptographic
operation.
PublicKey (input/optional)
The public key corresponding to the private key being
unwrapped. If a symmetric key is being unwrapped, then
this parameter must be NULL.
WrappedKey (input)
A pointer to the wrapped key. The wrapped key may be a
symmetric key or the private key of a public/private key
pair. The unwrapping method is specified as meta data
within the wrapped key and is not specified outside of the
wrapped key.
KeyUsage (input)
A bit mask indicating all permitted uses for the unwrapped
key. If no value is specified, the CSP defines the usage
mask for the unwrapped key.
KeyAttr (input)
A bit mask defining other attribute values to be associated
with the unwrapped key.
KeyLabel (input/optional)
Pointer to a byte string that will be used as the label for
the unwrapped key.
CredAndAclEntry (input/optional)
A structure containing one or more credentials authorized
for creating a key and the prototype ACL entry that will
control future use of the newly created key. The credentials
and ACL entry prototype can be presented as immediate values
or callback functions can be provided for use by the CSP to
acquire the credentials and/or the ACL entry interactively.
If the CSP provides public access for creating a key, then
the credentials can be NULL. If the CSP defines a default
initial ACL entry for the new key, then the ACL entry
prototype can be an empty list.
UnwrappedKey (output)
A pointer to a CSSM_KEY structure that returns the unwrapped
key.
DescriptiveData (output)
A pointer to a CSSM_DATA structure that returns any
additional descriptive data that was associated with the
key during the wrapping operation. It is assumed that the
caller incorporated knowledge of the structure of this
data. If no additional data is associated with the imported
key, this output value is NULL.
SPI PARAMETERS
CSPHandle (input)
The handle that describes the add-in cryptographic service
provider module used to perform up calls to CSSM for the
memory functions managed by CSSM.
CCHandle (input)
The handle that describes the context of this cryptographic
operation.
Context (input)
Pointer to CSSM_CONTEXT structure that describes the
attributes with this context.
Privilege (input)
The export privilege to be applied during the cryptographic
operation. This parameter is forwarded to the CSP after
CSSM verifies the caller and service provider privilege set
includes the specified PRIVILEGE.
DESCRIPTION
This function unwraps the wrapped key using the context. The wrapped
key can be a symmetric key or a private key. If the unwrapping
algorithm is a symmetric algorithm, then a symmetric context must be
provided. If the unwrapping algorithm is an asymmetric algorithm,
then an asymmetric context must be provided. If the key is a private
key, then an asymmetric context must be provide describing the
unwrapping algorithm. The CSP can require the caller to provide
credentials authorizing the caller to store the unwrapped key within
the CSP. The CSP can also require that the caller provide an initial
ACL entry to control future access to the newly stored key. These
credentials and the initial ACL entry value are provided in
CredAndAclEntry parameter. If the unwrapping algorithm is
CSSM_ALGID_NONE and the wrapped key is actually a raw key (as
indicated by its key attributes), then the key is imported into
the CSP. Support for a CSSM_ALGID_NONE unwrapping algorithm is at
the option of the CSP. The unwrapped key is restored to its
original pre-wrap state based on the key attributes recorded by the
wrapped key during the wrap operation. These attributes must not
be modified by the caller.
Authorization policy can restrict the set of callers who can create
a new resource. In this case, the caller must present a set of access
credentials for authorization. Upon successfully authenticating the
credentials, the template that verified the presented samples
identifies the ACL entry that will be used in the authorization
computation. If the caller is authorized, the new resource is created.
The caller must provide an initial ACL entry to be associated with
the newly created resource. This entry is used to control future
access to the new resource and (since the subject is deemed to be
the "Owner") exercise control over its associated ACL. The caller
can specify the following items for initializing an ACL entry:
Subject A CSSM_LIST structure, containing the type of the subject
and a template value that can be used to verify samples
that are presented in credentials when resource access is
requested.
Delegation flag
A value indicating whether the Subject can delegate the
permissions recorded in the AuthorizationTag. (This item
only applies to public key subjects).
Authorization tag
The set of permissions that are granted to the Subject.
Validity period
The start time and the stop time for which the ACL entry is
valid.
ACL entry tag
A user-defined string value associated with the ACL entry.
The service provider can modify the caller-provided initial
ACL entry to conform to any innate resource-access policy
that the service provider may be required to enforce. If the
initial ACL entry provided by the caller contains values or
permissions that are not supported by the service provider,
then the service provider can modify the initial ACL
appropriately or can fail the request to create the new
resource. Service providers list their supported
AuthorizationTag values in their Module Directory Services
primary record.
NOTES
The KeyData field of the CSSM_KEY structure is allocated by the
CSP. The application is required to free this memory using the
CSSM_FreeKey() (CSSM API), or CSP_FreeKey() (CSP SPI), function
or with the memory functions registered for the CSPHandle.
RETURN VALUE
A CSSM_RETURN value indicating success or specifying a particular
error condition. The value CSSM_OK indicates success. All other
values represent an error condition.
ERRORS
Errors are described in the CDSA technical standard. See CDSA.
CSSMERR_CSP_KEY_LABEL_ALREADY_EXISTS
CSSMERR_CSP_PUBLIC_KEY_INCONSISTENT
CSSMERR_CSP_PRIVATE_KEY_ALREADY_EXIST
SEE ALSO
Books
Intel CDSA Application Developer's Guide (see CDSA)
Other Help Topics
Functions for the CSSM API:
CSSM_WrapKey
Functions for the CSP SPI:
CSP_WrapKey