michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.browserid;
michael@0: 
michael@0: 
michael@0: /**
michael@0:  * Java produces signature in ASN.1 format. Here's some hard-coded encoding and decoding
michael@0:  * code, courtesy of a comment in
michael@0:  * <a href="http://stackoverflow.com/questions/10921733/how-sign-method-of-the-digital-signature-combines-the-r-s-values-in-to-array">http://stackoverflow.com/questions/10921733/how-sign-method-of-the-digital-signature-combines-the-r-s-values-in-to-array</a>.
michael@0:  */
michael@0: public class ASNUtils {
michael@0:   /**
michael@0:    * Decode two short arrays from ASN.1 bytes.
michael@0:    * @param input to extract.
michael@0:    * @return length 2 array of byte arrays.
michael@0:    */
michael@0:   public static byte[][] decodeTwoArraysFromASN1(byte[] input) throws IllegalArgumentException {
michael@0:     if (input == null) {
michael@0:       throw new IllegalArgumentException("input must not be null");
michael@0:     }
michael@0:     if (input.length <= 3)
michael@0:       throw new IllegalArgumentException("bad length");
michael@0:     if (input[0] != 0x30)
michael@0:       throw new IllegalArgumentException("bad encoding");
michael@0:     if ((input[1] & ((byte) 0x80)) != 0)
michael@0:       throw new IllegalArgumentException("bad length encoding");
michael@0:     if (input[2] != 0x02)
michael@0:       throw new IllegalArgumentException("bad encoding");
michael@0:     if ((input[3] & ((byte) 0x80)) != 0)
michael@0:       throw new IllegalArgumentException("bad length encoding");
michael@0:     byte rLength = input[3];
michael@0:     if (input.length <= 5 + rLength)
michael@0:       throw new IllegalArgumentException("bad length");
michael@0:     if (input[4 + rLength] != 0x02)
michael@0:       throw new IllegalArgumentException("bad encoding");
michael@0:     if ((input[5 + rLength] & (byte) 0x80) !=0)
michael@0:       throw new IllegalArgumentException("bad length encoding");
michael@0:     byte sLength = input[5 + rLength];
michael@0:     if (input.length != 6 + sLength + rLength)
michael@0:       throw new IllegalArgumentException("bad length");
michael@0:     byte[] rArr = new byte[rLength];
michael@0:     byte[] sArr = new byte[sLength];
michael@0:     System.arraycopy(input, 4, rArr, 0, rLength);
michael@0:     System.arraycopy(input, 6 + rLength, sArr, 0, sLength);
michael@0:     return new byte[][] { rArr, sArr };
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Encode two short arrays into ASN.1 bytes.
michael@0:    * @param first array to encode.
michael@0:    * @param second array to encode.
michael@0:    * @return array.
michael@0:    */
michael@0:   public static byte[] encodeTwoArraysToASN1(byte[] first, byte[] second) throws IllegalArgumentException {
michael@0:     if (first == null) {
michael@0:       throw new IllegalArgumentException("first must not be null");
michael@0:     }
michael@0:     if (second == null) {
michael@0:       throw new IllegalArgumentException("second must not be null");
michael@0:     }
michael@0:     byte[] output = new byte[6 + first.length + second.length];
michael@0:     output[0] = 0x30;
michael@0:     if (4 + first.length + second.length > 255)
michael@0:       throw new IllegalArgumentException("bad length");
michael@0:     output[1] = (byte) (4 + first.length + second.length);
michael@0:     if ((output[1] & ((byte) 0x80)) != 0)
michael@0:       throw new IllegalArgumentException("bad length encoding");
michael@0:     output[2] = 0x02;
michael@0:     output[3] = (byte) first.length;
michael@0:     if ((output[3] & ((byte) 0x80)) != 0)
michael@0:       throw new IllegalArgumentException("bad length encoding");
michael@0:     System.arraycopy(first, 0, output, 4, first.length);
michael@0:     output[4 + first.length] = 0x02;
michael@0:     output[5 + first.length] = (byte) second.length;
michael@0:     if ((output[5 + first.length] & ((byte) 0x80)) != 0)
michael@0:       throw new IllegalArgumentException("bad length encoding");
michael@0:     System.arraycopy(second, 0, output, 6 + first.length, second.length);
michael@0:     return output;
michael@0:   }
michael@0: }