HTML Parser Home Page

org.htmlparser.scanners
Class ScriptDecoder

java.lang.Object
  extended by org.htmlparser.scanners.ScriptDecoder

public class ScriptDecoder
extends Object

Decode script. Script obfuscated by the Windows Script Encoder provided by Microsoft, is converted to plaintext. This code is based loosely on example code provided by MrBrownstone with changes by Joe Steele, see scrdec14.c.


Field Summary
static int LAST_STATE
          The state to enter when decrypting is complete.
protected static int[] mDigits
          The base 64 decoding table.
protected static byte[] mEncodingIndex
          Table of lookup choice.
protected static char[] mEscaped
          The escaped characters corresponding to the each escape sequence.
protected static char[] mEscapes
          Escape sequence characters.
protected static char[] mLeader
          The leader.
protected static char[][] mLookupTable
          Two dimensional lookup table.
protected static char[] mPrefix
          The prefix.
protected static char[] mTrailer
          The trailer.
protected static int STATE_CHECKSUM
          State when reading the checksum.
protected static int STATE_DECODE
          State while decoding.
static int STATE_DONE
          Termination state.
protected static int STATE_ESCAPE
          State when reading an escape sequence.
protected static int STATE_FINAL
          State while exiting.
static int STATE_INITIAL
          State on entry.
protected static int STATE_LENGTH
          State while reading the encoded length.
protected static int STATE_PREFIX
          State when reading up to decoded text.
 
Constructor Summary
ScriptDecoder()
           
 
Method Summary
static String Decode(Page page, Cursor cursor)
          Decode script encoded by the Microsoft obfuscator.
protected static long decodeBase64(char[] p)
          Extract the base 64 encoded number.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

STATE_DONE

public static final int STATE_DONE
Termination state.

See Also:
Constant Field Values

STATE_INITIAL

public static final int STATE_INITIAL
State on entry.

See Also:
Constant Field Values

STATE_LENGTH

protected static final int STATE_LENGTH
State while reading the encoded length.

See Also:
Constant Field Values

STATE_PREFIX

protected static final int STATE_PREFIX
State when reading up to decoded text.

See Also:
Constant Field Values

STATE_DECODE

protected static final int STATE_DECODE
State while decoding.

See Also:
Constant Field Values

STATE_ESCAPE

protected static final int STATE_ESCAPE
State when reading an escape sequence.

See Also:
Constant Field Values

STATE_CHECKSUM

protected static final int STATE_CHECKSUM
State when reading the checksum.

See Also:
Constant Field Values

STATE_FINAL

protected static final int STATE_FINAL
State while exiting.

See Also:
Constant Field Values

LAST_STATE

public static int LAST_STATE
The state to enter when decrypting is complete. If this is STATE_DONE, the decryption will return with any characters following the encoded text still unconsumed. Otherwise, if this is STATE_INITIAL, the input will be exhausted and all following characters will be contained in the return value of the Decode() method.


mEncodingIndex

protected static byte[] mEncodingIndex
Table of lookup choice. The decoding cycles between three flavours determined by this sequence of 64 choices, corresponding to the first dimension of the lookup table.


mLookupTable

protected static char[][] mLookupTable
Two dimensional lookup table. The decoding uses this table to determine the plaintext for characters that aren't mEscaped.


mDigits

protected static int[] mDigits
The base 64 decoding table. This array determines the value of decoded base 64 elements.


mLeader

protected static char[] mLeader
The leader. The prefix to the encoded script is #@~^nnnnnn== where the n are the length digits in base64.


mPrefix

protected static char[] mPrefix
The prefix. The prfix separates the encoded text from the length.


mTrailer

protected static char[] mTrailer
The trailer. The suffix to the encoded script is nnnnnn==^#~@ where the n are the checksum digits in base64. These characters are the part after the checksum.


mEscapes

protected static char[] mEscapes
Escape sequence characters.


mEscaped

protected static char[] mEscaped
The escaped characters corresponding to the each escape sequence.

Constructor Detail

ScriptDecoder

public ScriptDecoder()
Method Detail

decodeBase64

protected static long decodeBase64(char[] p)
Extract the base 64 encoded number. This is a very limited subset of base 64 encoded characters. Six characters are expected. These are translated into a single long value. For a more complete base 64 codec see for example the base64 package of iHarder.net

Parameters:
p - Six base 64 encoded digits.
Returns:
The value of the decoded number.

Decode

public static String Decode(Page page,
                            Cursor cursor)
                     throws ParserException
Decode script encoded by the Microsoft obfuscator.

Parameters:
page - The source for encoded text.
cursor - The position at which to start decoding. This is advanced to the end of the encoded text.
Returns:
The plaintext.
Throws:
ParserException - If an error is discovered while decoding.

© 2006 Derrick Oswald
Sep 17, 2006

HTML Parser is an open source library released under Common Public License. SourceForge.net