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      1 /*
      2  * Copyright (C) 2009 Google Inc.  All rights reserved.
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.google.polo.pairing;
     18 
     19 import com.google.polo.exception.PoloException;
     20 
     21 import java.math.BigInteger;
     22 import java.security.cert.Certificate;
     23 
     24 import javax.net.ssl.SSLPeerUnverifiedException;
     25 import javax.net.ssl.SSLSession;
     26 
     27 /**
     28  * Utility methods of general usefulness to the Polo library.
     29  */
     30 public class PoloUtil {
     31 
     32   /**
     33    * Returns the peer {@link Certificate} for an {@link SSLSession}.
     34    *
     35    * @throws PoloException  if the peer certificate could not be obtained
     36    *                        from the {@link SSLSession}.
     37    * @return                the {@link Certificate} of the peer
     38    */
     39   public static Certificate getPeerCert(SSLSession session)
     40       throws PoloException {
     41     try {
     42       // Peer certificate
     43       Certificate[] certs = session.getPeerCertificates();
     44       if (certs == null || certs.length < 1) {
     45         throw new PoloException("No peer certificate.");
     46       }
     47       return certs[0];
     48     } catch (SSLPeerUnverifiedException e) {
     49       throw new PoloException(e);
     50     }
     51   }
     52 
     53   /**
     54    * Return the local {@link Certificate} for an {@link SSLSession}.
     55    *
     56    * @throws PoloException  if the local certificate could not be obtained
     57    *                        from the {@link SSLSession}
     58    * @return                the {@link Certificate} of the peer
     59    */
     60   public static Certificate getLocalCert(SSLSession session)
     61       throws PoloException {
     62     Certificate[] certs = session.getLocalCertificates();
     63     if (certs == null || certs.length < 1) {
     64       throw new PoloException("No local certificate.");
     65     }
     66     return certs[0];
     67   }
     68 
     69   /**
     70    * Converts an array of bytes to a string of hexadecimal characters.
     71    * Leading null bytes are preserved in the output.
     72    * <p>
     73    * The input byte stream is assumed to be a positive, two's complement
     74    * representation of an integer.  The return value is the hexadecimal string
     75    * representation of this value.
     76    *
     77    * @param bytes  the bytes to convert
     78    * @return       the string representation
     79    */
     80   public static String bytesToHexString(byte[] bytes) {
     81     if (bytes == null || bytes.length == 0) {
     82       return "";
     83     }
     84     BigInteger bigint = new BigInteger(1, bytes);
     85     int formatLen = bytes.length * 2;
     86     return String.format("%0" + formatLen + "x", bigint);
     87   }
     88 
     89   /**
     90    * Converts a string of hex characters to a byte array.
     91    *
     92    * @param hexstr  the string of hex characters
     93    * @return        a byte array representation
     94    */
     95   public static byte[] hexStringToBytes(String hexstr) {
     96     if (hexstr == null || hexstr.length() == 0 || (hexstr.length() % 2) != 0) {
     97       throw new IllegalArgumentException("Bad input string.");
     98     }
     99 
    100     byte[] result = new byte[hexstr.length() / 2];
    101     for (int i=0; i < result.length; i++) {
    102       result[i] = (byte) Integer.parseInt(hexstr.substring(2 * i, 2 * (i + 1)),
    103           16);
    104     }
    105     return result;
    106   }
    107 
    108   /**
    109    * Converts an integer value to the big endian 4-byte representation.
    110    */
    111   public static final byte[] intToBigEndianIntBytes(int intVal) {
    112     byte[] outBuf = new byte[4];
    113     outBuf[0] = (byte)((intVal >> 24) & 0xff);
    114     outBuf[1] = (byte)((intVal >> 16) & 0xff);
    115     outBuf[2] = (byte)((intVal >> 8) & 0xff);
    116     outBuf[3] = (byte)(intVal & 0xff);
    117     return outBuf;
    118   }
    119 
    120   /**
    121    * Converts a 4-byte array of bytes to an unsigned long value.
    122    */
    123   public static final long intBigEndianBytesToLong(byte[] input) {
    124     assert (input.length == 4);
    125     long ret = (long)(input[0]) & 0xff;
    126     ret <<= 8;
    127     ret |= (long)(input[1]) & 0xff;
    128     ret <<= 8;
    129     ret |= (long)(input[2]) & 0xff;
    130     ret <<= 8;
    131     ret |= (long)(input[3]) & 0xff;
    132     return ret;
    133   }
    134 
    135 }
    136