com.cloudant.sync.datastore.encryption

Class EncryptedAttachmentOutputStream

java.lang.Object

java.io.OutputStream

java.io.FilterOutputStream

com.cloudant.sync.datastore.encryption.EncryptedAttachmentOutputStream

All Implemented Interfaces:

java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable

public class EncryptedAttachmentOutputStream
extends java.io.FilterOutputStream

An EncryptedAttachmentOutputStream handles writing AES encrypted data to disk, combining the encrypted data with a header specifying the IV used during encryption. A CipherOutputStream is used to encrypt the data sent via write() methods.

This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.io.OutputStream and java.io.FilterOutputStream. 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.

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 the underlying CipherOutputStream.

The data format written by this class is read by EncryptedAttachmentInputStream, 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
EncryptedAttachmentOutputStream(java.io.OutputStream out, byte[] key, byte[] iv) Creates an output stream with a key and IV.

Method Summary

Modifier and Type	Method and Description
void	close()
void	flush()
void	write(byte[] b)
void	write(byte[] b, int off, int len)
void	write(int b)

Methods inherited from class java.lang.Object

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

Constructor Detail

EncryptedAttachmentOutputStream

public EncryptedAttachmentOutputStream(java.io.OutputStream out,
                                       byte[] key,
                                       byte[] iv)
                                throws java.security.InvalidAlgorithmParameterException,
                                       java.security.InvalidKeyException,
                                       java.io.IOException

Creates an output stream with a key and IV.

This constructor writes bytes to the out parameter in order to write the header.

Note: if the specified output stream is null, a NullPointerException is thrown as the constructor tries to write to the passed output stream.

Parameters:

out - the output stream object.

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

iv - the initialisation vector to use.

Throws:

java.security.InvalidAlgorithmParameterException - if IV is wrong size

java.security.InvalidKeyException - if key is wrong size

java.io.IOException - on I/O exceptions

Method Detail

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.FilterOutputStream

Throws:

java.io.IOException

flush

public void flush()
           throws java.io.IOException

Specified by:

flush in interface java.io.Flushable

Overrides:

flush in class java.io.FilterOutputStream

Throws:

java.io.IOException

write

public void write(byte[] b)
           throws java.io.IOException

Overrides:

write in class java.io.FilterOutputStream

Throws:

java.io.IOException

write

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

Overrides:

write in class java.io.FilterOutputStream

Throws:

java.io.IOException

write

public void write(int b)
           throws java.io.IOException

Overrides:

write in class java.io.FilterOutputStream

Throws:

java.io.IOException