Class CtrCryptoInputStream

java.lang.Object

java.io.InputStream

org.apache.commons.crypto.stream.CryptoInputStream

org.apache.commons.crypto.stream.CtrCryptoInputStream

All Implemented Interfaces:

Closeable, AutoCloseable, Channel, ReadableByteChannel

Direct Known Subclasses:

PositionedCryptoInputStream

public class CtrCryptoInputStream
extends CryptoInputStream

CtrCryptoInputStream decrypts data. AES CTR mode is required in order to ensure that the plain text and cipher text have a 1:1 mapping. CTR crypto stream has stream characteristic which is useful for implement features like random seek. The decryption is buffer based. The key points of the decryption are (1) calculating the counter and (2) padding through stream position:

counter = base + pos/(algorithm blocksize); padding = pos%(algorithm blocksize);

The underlying stream offset is maintained as state. It is not thread-safe.

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	cipherReset	Flag to mark whether the cipher has been reset
private final byte[]	initIV	The initial IV.
private final byte[]	iv	Initialization vector for the cipher.
private byte	padding	Padding = pos%(algorithm blocksize); Padding is put into CryptoInputStream.inBuffer before any other data goes in.
private long	streamOffset	Underlying stream offset

Fields inherited from class CryptoInputStream

cipher, EOS, inBuffer, input, key, outBuffer, STREAM_BUFFER_SIZE_KEY

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	CtrCryptoInputStream(InputStream inputStream, CryptoCipher cipher, int bufferSize, byte[] key, byte[] iv)	Constructs a CtrCryptoInputStream.
protected	CtrCryptoInputStream(InputStream inputStream, CryptoCipher cipher, int bufferSize, byte[] key, byte[] iv, long streamOffset)	Constructs a CtrCryptoInputStream.
protected	CtrCryptoInputStream(ReadableByteChannel channel, CryptoCipher cipher, int bufferSize, byte[] key, byte[] iv)	Constructs a CtrCryptoInputStream.
protected	CtrCryptoInputStream(ReadableByteChannel channel, CryptoCipher cipher, int bufferSize, byte[] key, byte[] iv, long streamOffset)	Constructs a CtrCryptoInputStream.
	CtrCryptoInputStream(Properties properties, InputStream inputStream, byte[] key, byte[] iv)	Constructs a CtrCryptoInputStream.
	CtrCryptoInputStream(Properties properties, InputStream inputStream, byte[] key, byte[] iv, long streamOffset)	Constructs a CtrCryptoInputStream.
	CtrCryptoInputStream(Properties properties, ReadableByteChannel channel, byte[] key, byte[] iv)	Constructs a CtrCryptoInputStream.
	CtrCryptoInputStream(Properties properties, ReadableByteChannel in, byte[] key, byte[] iv, long streamOffset)	Constructs a CtrCryptoInputStream.
protected	CtrCryptoInputStream(Input input, CryptoCipher cipher, int bufferSize, byte[] key, byte[] iv)	Constructs a CtrCryptoInputStream.
protected	CtrCryptoInputStream(Input input, CryptoCipher cipher, int bufferSize, byte[] key, byte[] iv, long streamOffset)	Constructs a CtrCryptoInputStream.

Method Summary

Modifier and Type	Method	Description
(package private) static void	calculateIV(byte[] initIV, long counter, byte[] IV)	This method is only for Counter (CTR) mode.
protected void	decrypt()	Does the decryption using inBuffer as input and outBuffer as output.
protected void	decrypt(ByteBuffer buf, int offset, int len)	Decrypts all data in buf: total n bytes from given start position.
protected void	decryptBuffer(ByteBuffer out)	Does the decryption using out as output.
protected void	decryptInPlace(ByteBuffer buf)	Does the decryption using inBuffer as input and buf as output.
protected int	decryptMore()	Decrypts more data by reading the under layer stream.
protected long	getCounter(long position)	Gets the counter for input stream position.
protected byte[]	getInitIV()	Gets the initialization vector.
protected byte	getPadding(long position)	Gets the padding for input stream position.
protected long	getStreamOffset()	Gets the offset of the stream.
protected long	getStreamPosition()	Gets the position of the stream.
protected void	initCipher()	Overrides the initCipher().
protected byte	postDecryption(long position)	This method is executed immediately after decryption.
int	read(ByteBuffer buf)	Overrides the read(ByteBuffer).
protected void	resetCipher(long position)	Calculates the counter and iv, resets the cipher.
protected void	resetStreamOffset(long offset)	Resets the underlying stream offset; clear CryptoInputStream.inBuffer and CryptoInputStream.outBuffer.
void	seek(long position)	Seeks the stream to a specific position relative to start of the under layer stream.
protected void	setStreamOffset(long streamOffset)	Sets the offset of stream.
long	skip(long n)	Overrides the CryptoInputStream.skip(long).

Methods inherited from class CryptoInputStream

available, checkBufferSize, checkStream, checkStreamCipher, close, decryptFinal, freeBuffers, freeDirectBuffer, getBufferSize, getBufferSize, getCipher, getInput, getKey, getParams, isOpen, markSupported, read, read

Methods inherited from class InputStream

mark, read, reset

Methods inherited from class Object

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

Field Details

streamOffset

private long streamOffset

Underlying stream offset

initIV

private final byte[] initIV

The initial IV.

iv

private final byte[] iv

Initialization vector for the cipher.

padding

private byte padding

Padding = pos%(algorithm blocksize); Padding is put into CryptoInputStream.inBuffer before any other data goes in. The purpose of padding is to put the input data at proper position.

cipherReset

private boolean cipherReset

Flag to mark whether the cipher has been reset

Constructor Details

CtrCryptoInputStream

protected CtrCryptoInputStream(Input input,
 CryptoCipher cipher,
 int bufferSize,
 byte[] key,
 byte[] iv)
                        throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

input - the input data.

cipher - the CryptoCipher instance.

bufferSize - the bufferSize.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

protected CtrCryptoInputStream(Input input,
 CryptoCipher cipher,
 int bufferSize,
 byte[] key,
 byte[] iv,
 long streamOffset)
                        throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

input - the input data.

cipher - the CryptoCipher instance.

bufferSize - the bufferSize.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

streamOffset - the start offset in the stream.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

protected CtrCryptoInputStream(InputStream inputStream,
 CryptoCipher cipher,
 int bufferSize,
 byte[] key,
 byte[] iv)
                        throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

inputStream - the input stream.

cipher - the CryptoCipher instance.

bufferSize - the bufferSize.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

protected CtrCryptoInputStream(InputStream inputStream,
 CryptoCipher cipher,
 int bufferSize,
 byte[] key,
 byte[] iv,
 long streamOffset)
                        throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

inputStream - the InputStream instance.

cipher - the CryptoCipher instance.

bufferSize - the bufferSize.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

streamOffset - the start offset in the stream.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

public CtrCryptoInputStream(Properties properties,
 InputStream inputStream,
 byte[] key,
 byte[] iv)
                     throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

properties - The Properties class represents a set of properties.

inputStream - the input stream.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

public CtrCryptoInputStream(Properties properties,
 InputStream inputStream,
 byte[] key,
 byte[] iv,
 long streamOffset)
                     throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

properties - The Properties class represents a set of properties.

inputStream - the InputStream instance.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

streamOffset - the start offset in the stream.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

public CtrCryptoInputStream(Properties properties,
 ReadableByteChannel channel,
 byte[] key,
 byte[] iv)
                     throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

properties - The Properties class represents a set of properties.

channel - the ReadableByteChannel instance.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

public CtrCryptoInputStream(Properties properties,
 ReadableByteChannel in,
 byte[] key,
 byte[] iv,
 long streamOffset)
                     throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

properties - The Properties class represents a set of properties.

in - the ReadableByteChannel instance.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

streamOffset - the start offset in the stream.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

protected CtrCryptoInputStream(ReadableByteChannel channel,
 CryptoCipher cipher,
 int bufferSize,
 byte[] key,
 byte[] iv)
                        throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

channel - the ReadableByteChannel instance.

cipher - the cipher instance.

bufferSize - the bufferSize.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

Throws:

IOException - if an I/O error occurs.

CtrCryptoInputStream

protected CtrCryptoInputStream(ReadableByteChannel channel,
 CryptoCipher cipher,
 int bufferSize,
 byte[] key,
 byte[] iv,
 long streamOffset)
                        throws IOException

Constructs a CtrCryptoInputStream.

Parameters:

channel - the ReadableByteChannel instance.

cipher - the CryptoCipher instance.

bufferSize - the bufferSize.

key - crypto key for the cipher.

iv - Initialization vector for the cipher.

streamOffset - the start offset in the stream.

Throws:

IOException - if an I/O error occurs.

Method Details

calculateIV

static void calculateIV(byte[] initIV,
 long counter,
 byte[] IV)

This method is only for Counter (CTR) mode. Generally the CryptoCipher calculates the IV and maintain encryption context internally.For example a Cipher will maintain its encryption context internally when we do encryption/decryption using the CryptoCipher#update interface.

Encryption/Decryption is not always on the entire file. For example, in Hadoop, a node may only decrypt a portion of a file (i.e. a split). In these situations, the counter is derived from the file position.

The IV can be calculated by combining the initial IV and the counter with a lossless operation (concatenation, addition, or XOR).

Parameters:

initIV - initial IV

counter - counter for input stream position

IV - the IV for input stream position

See Also:

• http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Counter_.28CTR.29

decrypt

protected void decrypt()
                throws IOException

Does the decryption using inBuffer as input and outBuffer as output. Upon return, inBuffer is cleared; the decrypted data starts at outBuffer.position() and ends at outBuffer.limit().

Overrides:

decrypt in class CryptoInputStream

Throws:

IOException - if an I/O error occurs.

decrypt

protected void decrypt(ByteBuffer buf,
 int offset,
 int len)
                throws IOException

Decrypts all data in buf: total n bytes from given start position. Output is also buf and same start position. buf.position() and buf.limit() should be unchanged after decryption.

Parameters:

buf - The buffer into which bytes are to be transferred.

offset - the start offset in the data.

len - the maximum number of decrypted data bytes to read.

Throws:

IOException - if an I/O error occurs.

decryptBuffer

protected void decryptBuffer(ByteBuffer out)
                      throws IOException

Does the decryption using out as output.

Parameters:

out - the output ByteBuffer.

Throws:

IOException - if an I/O error occurs.

decryptInPlace

protected void decryptInPlace(ByteBuffer buf)
                       throws IOException

Does the decryption using inBuffer as input and buf as output. Upon return, inBuffer is cleared; the buf's position will be equal to p + n where p is the position before decryption, n is the number of bytes decrypted. The buf's limit will not have changed.

Parameters:

buf - The buffer into which bytes are to be transferred.

Throws:

IOException - if an I/O error occurs.

decryptMore

protected int decryptMore()
                   throws IOException

Decrypts more data by reading the under layer stream. The decrypted data will be put in the output buffer.

Overrides:

decryptMore in class CryptoInputStream

Returns:

The number of decrypted data. -1 if end of the decrypted stream.

Throws:

IOException - if an I/O error occurs.

getCounter

protected long getCounter(long position)

Gets the counter for input stream position.

Parameters:

position - the given position in the data.

Returns:

the counter for input stream position.

getInitIV

protected byte[] getInitIV()

Gets the initialization vector.

Returns:

the initIV.

getPadding

protected byte getPadding(long position)

Gets the padding for input stream position.

Parameters:

position - the given position in the data.

Returns:

the padding for input stream position.

getStreamOffset

protected long getStreamOffset()

Gets the offset of the stream.

Returns:

the stream offset.

getStreamPosition

protected long getStreamPosition()

Gets the position of the stream.

Returns:

the position of the stream.

initCipher

protected void initCipher()

Overrides the initCipher(). Initializes the cipher.

Overrides:

initCipher in class CryptoInputStream

postDecryption

protected byte postDecryption(long position)
                       throws IOException

This method is executed immediately after decryption. Checks whether cipher should be updated and recalculate padding if needed.

Parameters:

position - the given position in the data..

Returns:

the byte.

Throws:

IOException - if an I/O error occurs.

read

public int read(ByteBuffer buf)
         throws IOException

Overrides the read(ByteBuffer). Reads a sequence of bytes from this channel into the given buffer.

Specified by:

read in interface ReadableByteChannel

Overrides:

read in class CryptoInputStream

Parameters:

buf - The buffer into which bytes are to be transferred.

Returns:

The number of bytes read, possibly zero, or -1 if the channel has reached end-of-stream.

Throws:

IOException - if an I/O error occurs.

resetCipher

protected void resetCipher(long position)
                    throws IOException

Calculates the counter and iv, resets the cipher.

Parameters:

position - the given position in the data.

Throws:

IOException - if an I/O error occurs.

resetStreamOffset

protected void resetStreamOffset(long offset)
                          throws IOException

Resets the underlying stream offset; clear CryptoInputStream.inBuffer and CryptoInputStream.outBuffer. This Typically happens during skip(long).

Parameters:

offset - the offset of the stream.

Throws:

IOException - if an I/O error occurs.

seek

public void seek(long position)
          throws IOException

Seeks the stream to a specific position relative to start of the under layer stream.

Parameters:

position - the given position in the data.

Throws:

IOException - if an I/O error occurs.

setStreamOffset

protected void setStreamOffset(long streamOffset)

Sets the offset of stream.

Parameters:

streamOffset - the stream offset.

skip

public long skip(long n)
          throws IOException

Overrides the CryptoInputStream.skip(long). Skips over and discards n bytes of data from this input stream.

Overrides:

skip in class CryptoInputStream

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if an I/O error occurs.