org.apache.poi.poifs.crypt.cryptoapi

Class CryptoAPIDecryptor

java.lang.Object

org.apache.poi.poifs.crypt.Decryptor

org.apache.poi.poifs.crypt.cryptoapi.CryptoAPIDecryptor

All Implemented Interfaces:

Cloneable

public class CryptoAPIDecryptor
extends Decryptor
implements Cloneable

Field Summary

Fields inherited from class org.apache.poi.poifs.crypt.Decryptor

DEFAULT_PASSWORD, DEFAULT_POIFS_ENTRY

Method Summary

Modifier and Type	Method and Description
CryptoAPIDecryptor	clone()
ChunkedCipherInputStream	getDataStream(DirectoryNode dir) Return a stream with decrypted data.
ChunkedCipherInputStream	getDataStream(InputStream stream, int size, int initialPos) Wraps a stream for decryption
long	getLength() Returns the length of the encrypted data that can be safely read with Decryptor.getDataStream(org.apache.poi.poifs.filesystem.DirectoryNode).
POIFSFileSystem	getSummaryEntries(DirectoryNode root, String encryptedStream) Decrypt the Document-/SummaryInformation and other optionally streams.
Cipher	initCipherForBlock(Cipher cipher, int block) Initializes a cipher object for a given block index for encryption
void	setChunkSize(int chunkSize) Sets the chunk size of the data stream.
boolean	verifyPassword(String password)

Methods inherited from class org.apache.poi.poifs.crypt.Decryptor

getDataStream, getEncryptionInfo, getInstance, getIntegrityHmacKey, getIntegrityHmacValue, getSecretKey, getVerifier, setEncryptionInfo

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

verifyPassword

public boolean verifyPassword(String password)

Specified by:

verifyPassword in class Decryptor

initCipherForBlock

public Cipher initCipherForBlock(Cipher cipher,
                                 int block)
                          throws GeneralSecurityException

Description copied from class: Decryptor

Initializes a cipher object for a given block index for encryption

Overrides:

initCipherForBlock in class Decryptor

Parameters:

cipher - may be null, otherwise the given instance is reset to the new block index

block - the block index, e.g. the persist/slide id (hslf)

Returns:

a new cipher object, if cipher was null, otherwise the reinitialized cipher

Throws:

GeneralSecurityException - if the cipher can't be initialized

getDataStream

public ChunkedCipherInputStream getDataStream(DirectoryNode dir)
                                       throws IOException,
                                              GeneralSecurityException

Description copied from class: Decryptor

Return a stream with decrypted data.

Use Decryptor.getLength() to get the size of that data that can be safely read from the stream. Just reading to the end of the input stream is not sufficient because there are normally padding bytes that must be discarded

Specified by:

getDataStream in class Decryptor

Parameters:

dir - the node to read from

Returns:

decrypted stream

Throws:

IOException

GeneralSecurityException

getDataStream

public ChunkedCipherInputStream getDataStream(InputStream stream,
                                              int size,
                                              int initialPos)
                                       throws IOException,
                                              GeneralSecurityException

Description copied from class: Decryptor

Wraps a stream for decryption

As we are handling streams and don't know the total length beforehand, it's the callers duty to care for the length of the entries.

Overrides:

getDataStream in class Decryptor

Parameters:

stream - the stream to be wrapped

initialPos - initial/current byte position within the stream

Returns:

decrypted stream

Throws:

IOException

GeneralSecurityException

getSummaryEntries

public POIFSFileSystem getSummaryEntries(DirectoryNode root,
                                         String encryptedStream)
                                  throws IOException,
                                         GeneralSecurityException

Decrypt the Document-/SummaryInformation and other optionally streams. Opposed to other crypto modes, cryptoapi is record based and can't be used to stream-decrypt a whole file.

Summary entries are only encrypted within cryptoapi encrypted files. Binary RC4 encrypted files use non-encrypted/default property sets

Parameters:

root - root directory node of the OLE file containing the encrypted properties

encryptedStream - name of the encrypted stream - "encryption" for HSSF/HWPF, "encryptedStream" (or encryptedSummary?) for HSLF

Throws:

IOException

GeneralSecurityException

See Also:

2.3.5.4 RC4 CryptoAPI Encrypted Summary Stream

getLength

public long getLength()

Description copied from class: Decryptor

Returns the length of the encrypted data that can be safely read with Decryptor.getDataStream(org.apache.poi.poifs.filesystem.DirectoryNode). Just reading to the end of the input stream is not sufficient because there are normally padding bytes that must be discarded

The length variable is initialized in Decryptor.getDataStream(org.apache.poi.poifs.filesystem.DirectoryNode), an attempt to call getLength() prior to getDataStream() will result in IllegalStateException.

Specified by:

getLength in class Decryptor

Returns:

the length of the stream returned by getDataStream(DirectoryNode)

setChunkSize

public void setChunkSize(int chunkSize)

Description copied from class: Decryptor

Sets the chunk size of the data stream. Needs to be set before the data stream is requested. When not set, the implementation uses method specific default values

Overrides:

setChunkSize in class Decryptor

Parameters:

chunkSize - the chunk size, i.e. the block size with the same encryption key

clone

public CryptoAPIDecryptor clone()
                         throws CloneNotSupportedException

Overrides:

clone in class Decryptor

Throws:

CloneNotSupportedException