CertificateHelper.java

package helpers;

import java.math.BigInteger;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.regex.Pattern;

import org.bouncycastle.cert.X509CertificateHolder;
import org.bouncycastle.cert.jcajce.JcaX509CertificateConverter;

public final class CertificateHelper {

	public static String addHexColons(String input) {
		return input.replaceAll("..(?!$)", "$0:");
	}

	public static byte[] hexStringToByteArray(String s) {
		s = s.replaceAll(":", "");
		int len = s.length();
		byte[] data = new byte[len / 2];
		for (int i = 0; i < len; i += 2) {
			data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
		}
		return data;
	}

	public static String bigIntegerToHexString(BigInteger bigInteger) {
		return addHexColons(bigInteger.toString(16));
	}

	public static String bigIntegerToHexString(String bigInteger) {
		return bigIntegerToHexString(new BigInteger(bigInteger));
	}

	public static BigInteger hexStringToBigInteger(String hexString) {
		return new BigInteger(hexString.replaceAll(":", ""), 16);
	}

	/**
	 * Reads a Date as a String and returns a Date object.
	 * 
	 * @param date
	 *            Date as a String. Supported formats are
	 *            "MMM d HH:mm:ss yyy ZZZ" (Eg. Aug 15 10:56:49 2012 GMT) and
	 *            "EEE MMM d HH:mm:ss ZZZ yyy" (Eg. Thu Mar 26 01:00:00 CET
	 *            2015)
	 * @return Date object
	 * @throws ParseException
	 *             if input date cannot be parsed
	 * @throws IllegalArgumentException
	 *             If input date format is not supported
	 */
	public static Date stringToDate(String date) throws ParseException, IllegalArgumentException {
		SimpleDateFormat simpleDateFormat;
		Pattern pattern;
		
		Locale.setDefault(Locale.US); // The input date is in english

		// Format: MMM d HH:mm:ss yyy ZZZ (Eg. Aug 15 10:56:49 2012 GMT)
		pattern = Pattern.compile("[A-Z][a-z]{2} [0-9]{1,2} ([0-9]{2}:){1,2}[0-9]{2} [0-9]{4} [A-Z]{3}");
		if (pattern.matcher(date).matches()) {
			simpleDateFormat = new SimpleDateFormat("MMM d HH:mm:ss yyy ZZZ");
			return simpleDateFormat.parse(date);
		}
		// Format: EEE MMM d HH:mm:ss ZZZ yyy (Eg. Thu Mar 26 01:00:00 CET 2015)
		pattern = Pattern.compile("[A-Z][a-z]{2} [A-Z][a-z]{2} [0-9]{1,2} ([0-9]{2}:){1,2}[0-9]{2} [A-Z]{3,4} [0-9]{4}");
		if (pattern.matcher(date).matches()) {
			simpleDateFormat = new SimpleDateFormat("EEE MMM d HH:mm:ss ZZZ yyyy");
			return simpleDateFormat.parse(date);
		}

		throw new IllegalArgumentException("Unknown date format.");
	}

	/**
	 * Returns a hexadecimal representation of a byte array.
	 * 
	 * @param bytes
	 *            byte array to parse
	 * @return String with hex numbers of the byte array
	 */
	public static String byteArrayToHex(byte[] bytes) {
		// http://stackoverflow.com/questions/9655181/convert-from-byte-array-to-hex-string-in-java
		char[] hexArray = "0123456789ABCDEF".toCharArray();
		char[] hexChars = new char[bytes.length * 2];
		for (int j = 0; j < bytes.length; j++) {
			int v = bytes[j] & 0xFF;
			hexChars[j * 2] = hexArray[v >>> 4];
			hexChars[j * 2 + 1] = hexArray[v & 0x0F];
		}
		return new String(hexChars);
	}

	/**
	 * Converts the Object x509CertificateHolder to X509Certificate using the
	 * Bouncy Castle library.
	 * 
	 * @param x509CertificateHolder
	 *            Certificate to convert.
	 * @return Converted certificate
	 * @throws CertificateException
	 *             if the certifiate cannot be converted
	 */
	public static X509Certificate x509CertificateHolderToX509Certificate(X509CertificateHolder x509CertificateHolder) throws CertificateException {
		return new JcaX509CertificateConverter().setProvider("BC").getCertificate(x509CertificateHolder);

	}

	/**
	 * Returns the ASCII Values of a byte string.
	 * 
	 * @param hexString
	 *            to convert into an ASCII string
	 * @return ASCII representation of the input string
	 */
	public static String hexBytesToString(String hexString) {
		StringBuilder output = new StringBuilder();
		for (int i = 0; i < hexString.length(); i += 2) {
			String str = hexString.substring(i, i + 2);
			output.append((char) Integer.parseInt(str, 16));
		}
		return output.toString();
	}

	/**
	 * Returns the ASCII Values of a byte array.
	 * 
	 * @param bytes
	 *            to convert into an ASCII string.
	 * @return ASCII representation of the input byte array.
	 */
	public static String byteArrayToString(byte[] bytes) {
		return hexBytesToString(byteArrayToHex(bytes));
	}

}