org.linguafranca.pwdb.hashedblock

Class HmacBlockOutputStream

java.lang.Object

java.io.OutputStream

java.io.FilterOutputStream

org.linguafranca.pwdb.hashedblock.HmacBlockOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public class HmacBlockOutputStream
extends FilterOutputStream

Takes a stream of (encrypted GZIPped) data and formats it as HMAC Hashed Blocks to the underlying output stream.

An HMac block consists of

1. a 32 byte HMac checksum
2. a 4 byte block size
3. {blockSize} bytes of data

The Class is initialized with an initial key digest. For each block this key is transformed using the (implied, starting from 0) block number and used as the key for the block verification process. That process consists of digesting the block number, its length, and its content.

Streams in Keepass are Little Endian.

Field Summary

Fields inherited from class java.io.FilterOutputStream

out

Constructor Summary

Constructors

Constructor and Description
HmacBlockOutputStream(byte[] key, OutputStream outputStream) Create a BigEndian HmacBlockOutputStream
HmacBlockOutputStream(byte[] key, OutputStream outputStream, boolean littleEndian) Create a HmacBlockOutputStream with choice of endian encoding

Method Summary

Modifier and Type	Method and Description
void	close()
void	flush()
protected void	put(byte[] b, int offset, int length) Writes to the internal buffer, and writes to the underlying output stream as necessary as BLOCK_SIZE blocks
protected void	save() Save the internal buffer to the underlying stream as a Hmac block
void	write(byte[] b, int offset, int count)
void	write(int i)

Methods inherited from class java.io.FilterOutputStream

write

Methods inherited from class java.lang.Object

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

Constructor Detail

HmacBlockOutputStream

public HmacBlockOutputStream(byte[] key,
                             OutputStream outputStream)
                      throws IOException

Create a BigEndian HmacBlockOutputStream

Parameters:

key - credentials for this database

outputStream - the output stream to receive the hash blocks

Throws:

IOException

HmacBlockOutputStream

public HmacBlockOutputStream(byte[] key,
                             OutputStream outputStream,
                             boolean littleEndian)
                      throws IOException

Create a HmacBlockOutputStream with choice of endian encoding

Parameters:

key - credentials for this database

outputStream - the output stream to receive the hash blocks

littleEndian - true to encode in a little endian way

Throws:

IOException

Method Detail

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class FilterOutputStream

Throws:

IOException

put

protected void put(byte[] b,
                   int offset,
                   int length)
            throws IOException

Writes to the internal buffer, and writes to the underlying output stream as necessary as BLOCK_SIZE blocks

Parameters:

b - the byte array to write

offset - offset in the byte array

length - number of bytes to write

Throws:

IOException

save

protected void save()
             throws IOException

Save the internal buffer to the underlying stream as a Hmac block

Throws:

IOException

write

public void write(int i)
           throws IOException

Overrides:

write in class FilterOutputStream

Throws:

IOException

write

public void write(byte[] b,
                  int offset,
                  int count)
           throws IOException

Overrides:

write in class FilterOutputStream

Throws:

IOException

flush

public void flush()
           throws IOException

Specified by:

flush in interface Flushable

Overrides:

flush in class FilterOutputStream

Throws:

IOException