DecryptData

NAME

CSSM_DecryptData, CSP_DecryptData — Decrypt buffer data (CDSA)

SYNOPSIS

# include <cssm.h>

API:
CSSM_RETURN CSSMAPI CSSM_DecryptData
(CSSM_CC_HANDLE CCHandle,
const CSSM_DATA *CipherBufs,
uint32 CipherBufCount,
CSSM_DATA_PTR ClearBufs,
uint32 ClearBufCount,
uint32 *bytesDecrypted,
CSSM_DATA_PTR RemData)
SPI:
CSSM_RETURN CSSMCSPI CSP_DecryptData
(CSSM_CSP_HANDLE CSPHandle,
CSSM_CC_HANDLE CCHandle,
const CSSM_CONTEXT *Context,
const CSSM_DATA *CipherBufs,
uint32 CipherBufCount,
CSSM_DATA_PTR ClearBufs,
uint32 ClearBufCount,
uint32 *bytesDecrypted,
CSSM_DATA_PTR RemData,
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 used to link to the CSP-managed information.
`CipherBufs` (`input`)
		A pointer to a vector of CSSM_DATA structures that contain the data to be decrypted.
`CipherBufCount` (`input`)
		The number of `CipherBufs`.
`ClearBufs` (`output`)
		A pointer to a vector of CSSM_DATA structures that contain the decrypted data resulting from the decryption operation.
`ClearBufCount` (`input`)
		The number of `ClearBufs`.
`bytesDecrypted` (`output`)
		A pointer to `uint32` for the size of the decrypted data in bytes.
`RemData` (`output`)		A pointer to the CSSM_DATA structure for the remaining plain text if there is not enough buffer space available in the output data structures.

SPI PARAMETERS

`CSPHandle` (`input`)
		The handle that describes the add-in Cryptographic Service Provider module used to perform calls to CSSM for the memory functions managed by CSSM.
`Context` (`input`)		A 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 decrypts all data contained in the set of input buffers using information in the context. The CSSM_QuerySize() (CSSM API), or CSP_QuerySize() (CSP SPI), function can be used to estimate the output buffer size required. The minimum number of buffers required to contain the resulting plain text is produced as output. If the plain text result does not fit within the set of output buffers, the remaining plain text is returned in the single output buffer RemData.

The CSP can require that the cryptographic context include access credentials for authentication and authorization checks when using a private key or a secret key.

NOTES FOR API

The output is returned to the caller either by filling the caller-specified buffer or by using the application's declared memory allocation functions to allocate buffer space. To specify a specific, pre-allocated output buffer, the caller must provide an array of one or more CSSM_DATA structures, each containing a Length field value greater than zero and a non-NULL data pointer field value. To specify automatic output buffer allocation by the CSP, the caller must provide an array of one or more CSSM_DATA structures, each containing a Length field value equal to zero and a NULL data pointer field value. The application is always responsible for deallocating the memory when it is no longer needed. In-place decryption can be done by supplying the same input and output buffers.

NOTES FOR SPI

The output is returned to the caller as specified in Buffer Management for Cryptographic Services.

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.

CSSMERR_CSP_BLOCK_SIZE_MISMATCH
CSSMERR_CSP_OUTPUT_LENGTH_ERROR

DecryptData

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