Class CipherInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

javax.crypto.CipherInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class CipherInputStream
extends FilterInputStream

A CipherInputStream is composed of an InputStream and a Cipher object so that read() methods return data that are read in from the underlying InputStream but have been additionally processed by the Cipher object. The Cipher object must be fully initialized before being used by a CipherInputStream.

For example, if the Cipher object is initialized for decryption, the CipherInputStream will attempt to read in data and decrypt them, before returning the decrypted data.

This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.io.FilterInputStream and java.io.InputStream. This class has exactly those methods specified in its ancestor classes, and overrides them all. Moreover, this class catches all exceptions that are not thrown by its ancestor classes. In particular, the skip method skips, and the available method counts only data that have been processed by the encapsulated Cipher object. This class may catch BadPaddingException and other exceptions thrown by failed integrity checks during decryption. These exceptions are not re-thrown, so the client may not be informed that integrity checks failed. Because of this behavior, this class may not be suitable for use with decryption in an authenticated mode of operation (e.g. GCM). Applications that require authenticated encryption can use the Cipher API directly as an alternative to using this class.

It is crucial for a programmer using this class not to use methods that are not defined or overridden in this class (such as a new method or constructor that is later added to one of the super classes), because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherInputStream.

Since:

1.4

See Also:

• InputStream
• FilterInputStream
• Cipher
• CipherOutputStream

Field Summary

Fields declared in class FilterInputStream

in

Modifier and Type	Field	Description
protected InputStream	in	The input stream to be filtered.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	CipherInputStream(InputStream is)	Constructs a CipherInputStream from an InputStream without specifying a Cipher object.
	CipherInputStream(InputStream is, Cipher c)	Constructs a CipherInputStream from an InputStream and a Cipher object.

Method Summary

Modifier and Type	Method	Description
int	available()	Returns the number of bytes that can be read from this input stream without blocking.
void	close()	Closes this input stream and releases any system resources associated with the stream.
boolean	markSupported()	Tests if this input stream supports the mark and reset methods, which it does not.
int	read()	Reads the next byte of data from this input stream.
int	read(byte[] b)	Reads up to b.length bytes of data from this input stream into an array of bytes.
int	read(byte[] b, int off, int len)	Reads up to len bytes of data from this input stream into an array of bytes.
long	skip(long n)	Skips n bytes of input from the bytes that can be read from this input stream without blocking.

Methods declared in class FilterInputStream

mark, reset

Modifier and Type	Method	Description
void	mark(int readlimit)	Marks the current position in this input stream.
void	reset()	Repositions this stream to the position at the time the mark method was last called on this input stream.

Methods declared in class InputStream

nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Modifier and Type	Method	Description
static InputStream	nullInputStream()	Returns a new InputStream that reads no bytes.
byte[]	readAllBytes()	Reads all remaining bytes from the input stream.
int	readNBytes(byte[] b, int off, int len)	Reads the requested number of bytes from the input stream into the given byte array.
byte[]	readNBytes(int len)	Reads up to a specified number of bytes from the input stream.
void	skipNBytes(long n)	Skips over and discards exactly n bytes of data from this input stream.
long	transferTo(OutputStream out)	Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read.

Methods declared in class Object

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

Modifier and Type	Method	Description
protected Object	clone()	Creates and returns a copy of this object.
boolean	equals(Object obj)	Indicates whether some other object is "equal to" this one.
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
int	hashCode()	Returns a hash code value for this object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
String	toString()	Returns a string representation of the object.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details

CipherInputStream

public CipherInputStream(InputStream is,
 Cipher c)

Constructs a CipherInputStream from an InputStream and a Cipher object.
Note: if the specified input stream or cipher is null, a NullPointerException may be thrown later when they are used.

Parameters:

is - the to-be-processed input stream

c - an initialized Cipher object

CipherInputStream

protected CipherInputStream(InputStream is)

Constructs a CipherInputStream from an InputStream without specifying a Cipher object. This has the effect of constructing a CipherInputStream using a NullCipher.
Note: if the specified input stream is null, a NullPointerException may be thrown later when it is used.

Parameters:

is - the to-be-processed input stream

Method Details

read

public int read()
         throws IOException

Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

Overrides:

read in class FilterInputStream

Returns:

the next byte of data, or -1 if the end of the stream is reached.

Throws:

IOException - if an I/O error occurs.

See Also:

• FilterInputStream.in

read

public int read(byte[] b)
         throws IOException

Reads up to b.length bytes of data from this input stream into an array of bytes.

The read method of InputStream calls the read method of three arguments with the arguments b, 0, and b.length.

Overrides:

read in class FilterInputStream

Parameters:

b - the buffer into which the data is read.

Returns:

the total number of bytes read into the buffer, or -1 is there is no more data because the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

See Also:

• InputStream.read(byte[], int, int)

read

public int read(byte[] b,
 int off,
 int len)
         throws IOException

Reads up to len bytes of data from this input stream into an array of bytes. This method blocks until some input is available. If the first argument is null, up to len bytes are read and discarded.

Overrides:

read in class FilterInputStream

Parameters:

b - the buffer into which the data is read.

off - the start offset in the destination array buf

len - the maximum number of bytes read.

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

See Also:

• InputStream.read()

skip

public long skip(long n)
          throws IOException

Skips n bytes of input from the bytes that can be read from this input stream without blocking.

Fewer bytes than requested might be skipped. The actual number of bytes skipped is equal to n or the result of a call to available, whichever is smaller. If n is less than zero, no bytes are skipped.

The actual number of bytes skipped is returned.

Overrides:

skip in class FilterInputStream

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if an I/O error occurs.

See Also:

• InputStream.skipNBytes(long)

available

public int available()
              throws IOException

Returns the number of bytes that can be read from this input stream without blocking. The available method of InputStream returns 0. This method should be overridden by subclasses.

Overrides:

available in class FilterInputStream

Returns:

the number of bytes that can be read from this input stream without blocking.

Throws:

IOException - if an I/O error occurs.

close

public void close()
           throws IOException

Closes this input stream and releases any system resources associated with the stream.

The close method of CipherInputStream calls the close method of its underlying input stream.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class FilterInputStream

Throws:

IOException - if an I/O error occurs.

See Also:

• FilterInputStream.in

markSupported

public boolean markSupported()

Tests if this input stream supports the mark and reset methods, which it does not.

Overrides:

markSupported in class FilterInputStream

Returns:

false, since this class does not support the mark and reset methods.

See Also:

• InputStream.mark(int)
• InputStream.reset()