net.java.truevfs.comp.zipdriver

Class KeyManagerZipCryptoParameters

java.lang.Object

net.java.truevfs.comp.zipdriver.KeyManagerZipCryptoParameters

All Implemented Interfaces:

ZipCryptoParameters, ZipParameters, ZipParametersProvider

@ThreadSafe
public class KeyManagerZipCryptoParameters
extends Object
implements ZipParametersProvider, ZipCryptoParameters

An adapter which provides ZipCryptoParameters by using a KeyManagerMap.

The current implementation supports only WinZipAesParameters.

Author:

Christian Schlichtherle

Field Summary

Fields

Modifier and Type	Field and Description
protected Charset	charset The character set which has been provided to the constructor and is used for encoding entry names and the file comment in the ZIP file .

Constructor Summary

Constructors

Constructor and Description
KeyManagerZipCryptoParameters(AbstractZipDriver<?> driver, FsModel model, Charset charset) Constructs new ZIP crypto parameters.

Method Summary

Modifier and Type	Method and Description
<P extends ZipParameters> P	get(Class<P> type) Returns ZipParameters of the given type or null if not available.
protected byte[]	password(char[] characters, String name) A template method to derive password bytes from the given password characters and the given entry name.

Methods inherited from class java.lang.Object

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

Field Detail

charset

protected final Charset charset

The character set which has been provided to the constructor and is used for encoding entry names and the file comment in the ZIP file .

Constructor Detail

KeyManagerZipCryptoParameters

public KeyManagerZipCryptoParameters(AbstractZipDriver<?> driver,
                                     FsModel model,
                                     Charset charset)

Constructs new ZIP crypto parameters.

Parameters:

driver - the ZIP driver.

model - the file system model.

charset - the character set which is used for encoding entry names and the file comment in the ZIP file.

Method Detail

get

public <P extends ZipParameters> P get(Class<P> type)

Returns ZipParameters of the given type or null if not available.

If type is assignable from WinZipAesParameters, then a KeyManager for AesPbeParameters will getKeyManager used which is obtained from the driver which has been provided to the constructor.

Otherwise, null gets returned.

Specified by:

get in interface ZipParametersProvider

Type Parameters:

P - the type of the ZIP parameters.

Parameters:

type - the ZipParameters interface class which's implementation is required.

Returns:

ZipParameters of the given type or null if not available.

password

protected byte[] password(char[] characters,
                          String name)

A template method to derive password bytes from the given password characters and the given entry name. Typically, only the given password characters should getKeyManager encoded to form the result. Optionally, the given entry name can be mixed into the result for authentication. Note that this would then form a part of the password used for writing or reading encrypted entries, however. A third party which is expected to successfully read or write encrypted entries would have to agree on the same password bytes derivation scheme.

The implementation in the class KeyManagerZipCryptoParameters ignores the given entry name and just encodes the given password characters using PBEParametersGenerator.PKCS5PasswordToBytes(char[]).

A reasonable alternative implementation could encode the given password characters using the value of the field charset, which is the character set actually used to encode entry names and comments in the ZIP file, e.g. UTF-8 or CP437.

Parameters:

characters - the password characters to encode.

name - the entry name for optional mixing into the result.

Returns:

The derived password bytes.

See Also:

Discussion Of Alternative Character Set Encodings, RFC 2898: PKCS #5: Password-Based Cryptography Specification Version 2.0 (IETF et al.)