com.cloudant.sync.datastore.encryption

Class EncryptedAttachmentInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

com.cloudant.sync.datastore.encryption.EncryptedAttachmentInputStream

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public class EncryptedAttachmentInputStream
extends java.io.FilterInputStream

An EncryptedAttachmentInputStream handles reading AES encrypted data from disk, first reading the attachment file's header to determine the IV and checking the on-disk version is readable. A CipherInputStream is used to decrypt the data read via read() methods.

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.

It is crucial for a programmer using this class not to use methods that are not defined or overriden 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.

The data format read by this class is written by EncryptedAttachmentOutputStream, and is:

 Header:
 1-byte : version number, 1
 16-byte: initialisation vector

 Body:
 AES CBC Encrypted file content.
 

API Status: Private - API users are discouraged from using this class as fields, method signatures, and implementation details may be subject to change

Constructor Summary

Constructors

Constructor and Description
EncryptedAttachmentInputStream(java.io.InputStream in, byte[] key) Creates an input stream with a key.

Method Summary

Modifier and Type	Method and Description
int	available()
void	close()
boolean	markSupported()
int	read()
int	read(byte[] b)
int	read(byte[] b, int off, int len)
long	skip(long n)

Methods inherited from class java.io.FilterInputStream

mark, reset

Methods inherited from class java.lang.Object

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

Constructor Detail

EncryptedAttachmentInputStream

public EncryptedAttachmentInputStream(java.io.InputStream in,
                                      byte[] key)
                               throws java.security.InvalidKeyException,
                                      java.io.IOException

Creates an input stream with a key.

An IV is not required as the on-disk format contains this.

This constructor reads bytes from the in parameter in order to read the header.

Note: if the specified input stream is null, a NullPointerException is thrown as the constructor tries to read from the passed input stream.

Parameters:

in - the input stream object.

key - the encryption key to use. Length must be supported by underlying JCE implementation.

Throws:

java.security.InvalidKeyException - if key is wrong size

java.io.IOException - on I/O exceptions

Method Detail

read

public int read()
         throws java.io.IOException

Overrides:

read in class java.io.FilterInputStream

Throws:

java.io.IOException

read

public int read(byte[] b)
         throws java.io.IOException

Overrides:

read in class java.io.FilterInputStream

Throws:

java.io.IOException

read

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

Overrides:

read in class java.io.FilterInputStream

Throws:

java.io.IOException

skip

public long skip(long n)
          throws java.io.IOException

Overrides:

skip in class java.io.FilterInputStream

Throws:

java.io.IOException

available

public int available()
              throws java.io.IOException

Overrides:

available in class java.io.FilterInputStream

Throws:

java.io.IOException

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Overrides:

close in class java.io.FilterInputStream

Throws:

java.io.IOException

markSupported

public boolean markSupported()

Overrides:

markSupported in class java.io.FilterInputStream