JsUnpacker.java

import java.util.HashMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class JsUnpacker {
	private String packedJS = null;

	/**
	 * @param  packedJS javascript P.A.C.K.E.R. coded.
	 *
	 */
	public JsUnpacker(String packedJS) {
		this.packedJS = packedJS;
	}

	/**
	 * Detects whether the javascript is P.A.C.K.E.R. coded.
	 *
	 * @return true if it's P.A.C.K.E.R. coded.
	 *
	 */
	public boolean detect() {
		String js = packedJS.replace(" ", "");
		Pattern p = Pattern.compile("eval\\(function\\(p,a,c,k,e,(?:r|d)");
		Matcher m = p.matcher(js);
		return m.find();
	}

	/**
	 * Unpack the javascript
	 *
	 * @return the javascript unpacked or null.
	 *
	 */
	public String unpack() {
		String js = new String(packedJS);
		try {
			Pattern p = Pattern.compile("\\}\\s*\\('(.*)',\\s*(.*?),\\s*(\\d+),\\s*'(.*?)'\\.split\\('\\|'\\)", Pattern.DOTALL);
			Matcher m = p.matcher(js);
			if(m.find() && m.groupCount() == 4) {
				String payload = m.group(1).replace("\\'", "'");
				String radixStr = m.group(2);
				String countStr = m.group(3);
				String[] symtab = m.group(4).split("\\|");

				int radix = 36;
				int count = 0;
				try {
					radix = Integer.parseInt(radixStr);
				} catch(Exception e) {
				}
				try {
					count = Integer.parseInt(countStr);
				} catch(Exception e) {
				}

				if(symtab.length != count) {
					throw new Exception ("Unknown p.a.c.k.e.r. encoding");
				}

				Unbase unbase = new Unbase(radix);
				p = Pattern.compile("\\b\\w+\\b");
				m = p.matcher(payload);
				StringBuilder decoded = new StringBuilder(payload);
				int replaceOffset = 0;
				while(m.find()) {
					String word = m.group(0);

					int x = unbase.unbase(word);
					String value = null;
					if(x < symtab.length) {
						value = symtab[x];
					}

					if(value != null && value.length() > 0) {
						decoded.replace(m.start() + replaceOffset, m.end() + replaceOffset, value);
						replaceOffset += (value.length() - word.length());
					}
				}
				return decoded.toString();
			}

		} catch(Exception e) {
			e.printStackTrace();
		}
		return null;
	}

	private class Unbase {
		private final String ALPHABET_62 = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
		private final String ALPHABET_95 = " !\"#$%&\\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\\\]^_`abcdefghijklmnopqrstuvwxyz{|}~";
		private String alphabet = null;
		private HashMap<String, Integer> dictionnary = null;
		private int radix;

		Unbase(int radix) {
			this.radix = radix;

			if (radix > 36) {
				if (radix < 62) {
					alphabet = ALPHABET_62.substring(0, radix);
				} else if (radix > 62 && radix < 95) {
					alphabet = ALPHABET_95.substring(0, radix);
				} else if (radix == 62) {
					alphabet = ALPHABET_62;
				} else if (radix == 95) {
					alphabet = ALPHABET_95;
				}

				dictionnary = new HashMap<>(95);
				for (int i = 0; i < alphabet.length(); i++) {
					dictionnary.put(alphabet.substring(i, i + 1), i);
				}
			}
		}

		int unbase(String str) {
			int ret = 0;

			if (alphabet == null) {
				ret = Integer.parseInt(str, radix);
			} else {
				String tmp = new StringBuilder(str).reverse().toString();
				for (int i = 0; i < tmp.length(); i++) {
					ret += Math.pow(radix, i) * dictionnary.get(tmp.substring(i, i + 1));
				}
			}
			return ret;
		}
	}
}