org.htmlparser.scanners
Class ScriptDecoder

java.lang.Object
  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.

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Constant Field Values

STATE_INITIAL

public static final int STATE_INITIAL

State on entry.

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Constant Field Values

STATE_LENGTH

protected static final int STATE_LENGTH

State while reading the encoded length.

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Constant Field Values

STATE_PREFIX

protected static final int STATE_PREFIX

State when reading up to decoded text.

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Constant Field Values

STATE_DECODE

protected static final int STATE_DECODE

State while decoding.

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Constant Field Values

STATE_ESCAPE

protected static final int STATE_ESCAPE

State when reading an escape sequence.

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Constant Field Values

STATE_CHECKSUM

protected static final int STATE_CHECKSUM

State when reading the checksum.

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Constant Field Values

STATE_FINAL

protected static final int STATE_FINAL

State while exiting.

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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.