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Sourcecode: jenkins-trilead-ssh2 version File versions  Download package

PEMDecoder.java

package com.trilead.ssh2.crypto;

import java.io.BufferedReader;
import java.io.CharArrayReader;
import java.io.IOException;
import java.math.BigInteger;

import com.trilead.ssh2.crypto.cipher.AES;
import com.trilead.ssh2.crypto.cipher.BlockCipher;
import com.trilead.ssh2.crypto.cipher.CBCMode;
import com.trilead.ssh2.crypto.cipher.DES;
import com.trilead.ssh2.crypto.cipher.DESede;
import com.trilead.ssh2.crypto.digest.MD5;
import com.trilead.ssh2.signature.DSAPrivateKey;
import com.trilead.ssh2.signature.RSAPrivateKey;


/**
 * PEM Support.
 * 
 * @author Christian Plattner, plattner@trilead.com
 * @version $Id: PEMDecoder.java,v 1.1 2007/10/15 12:49:56 cplattne Exp $
 */
00025 public class PEMDecoder
{
      private static final int PEM_RSA_PRIVATE_KEY = 1;
      private static final int PEM_DSA_PRIVATE_KEY = 2;

      private static final int hexToInt(char c)
      {
            if ((c >= 'a') && (c <= 'f'))
            {
                  return (c - 'a') + 10;
            }

            if ((c >= 'A') && (c <= 'F'))
            {
                  return (c - 'A') + 10;
            }

            if ((c >= '0') && (c <= '9'))
            {
                  return (c - '0');
            }

            throw new IllegalArgumentException("Need hex char");
      }

      private static byte[] hexToByteArray(String hex)
      {
            if (hex == null)
                  throw new IllegalArgumentException("null argument");

            if ((hex.length() % 2) != 0)
                  throw new IllegalArgumentException("Uneven string length in hex encoding.");

            byte decoded[] = new byte[hex.length() / 2];

            for (int i = 0; i < decoded.length; i++)
            {
                  int hi = hexToInt(hex.charAt(i * 2));
                  int lo = hexToInt(hex.charAt((i * 2) + 1));

                  decoded[i] = (byte) (hi * 16 + lo);
            }

            return decoded;
      }

      private static byte[] generateKeyFromPasswordSaltWithMD5(byte[] password, byte[] salt, int keyLen)
                  throws IOException
      {
            if (salt.length < 8)
                  throw new IllegalArgumentException("Salt needs to be at least 8 bytes for key generation.");

            MD5 md5 = new MD5();

            byte[] key = new byte[keyLen];
            byte[] tmp = new byte[md5.getDigestLength()];

            while (true)
            {
                  md5.update(password, 0, password.length);
                  md5.update(salt, 0, 8); // ARGH we only use the first 8 bytes of the salt in this step.
                  // This took me two hours until I got AES-xxx running.

                  int copy = (keyLen < tmp.length) ? keyLen : tmp.length;

                  md5.digest(tmp, 0);

                  System.arraycopy(tmp, 0, key, key.length - keyLen, copy);

                  keyLen -= copy;

                  if (keyLen == 0)
                        return key;

                  md5.update(tmp, 0, tmp.length);
            }
      }

      private static byte[] removePadding(byte[] buff, int blockSize) throws IOException
      {
            /* Removes RFC 1423/PKCS #7 padding */

            int rfc_1423_padding = buff[buff.length - 1] & 0xff;

            if ((rfc_1423_padding < 1) || (rfc_1423_padding > blockSize))
                  throw new IOException("Decrypted PEM has wrong padding, did you specify the correct password?");

            for (int i = 2; i <= rfc_1423_padding; i++)
            {
                  if (buff[buff.length - i] != rfc_1423_padding)
                        throw new IOException("Decrypted PEM has wrong padding, did you specify the correct password?");
            }

            byte[] tmp = new byte[buff.length - rfc_1423_padding];
            System.arraycopy(buff, 0, tmp, 0, buff.length - rfc_1423_padding);
            return tmp;
      }

      private static final PEMStructure parsePEM(char[] pem) throws IOException
      {
            PEMStructure ps = new PEMStructure();

            String line = null;

            BufferedReader br = new BufferedReader(new CharArrayReader(pem));

            String endLine = null;

            while (true)
            {
                  line = br.readLine();

                  if (line == null)
                        throw new IOException("Invalid PEM structure, '-----BEGIN...' missing");

                  line = line.trim();

                  if (line.startsWith("-----BEGIN DSA PRIVATE KEY-----"))
                  {
                        endLine = "-----END DSA PRIVATE KEY-----";
                        ps.pemType = PEM_DSA_PRIVATE_KEY;
                        break;
                  }

                  if (line.startsWith("-----BEGIN RSA PRIVATE KEY-----"))
                  {
                        endLine = "-----END RSA PRIVATE KEY-----";
                        ps.pemType = PEM_RSA_PRIVATE_KEY;
                        break;
                  }
            }

            while (true)
            {
                  line = br.readLine();

                  if (line == null)
                        throw new IOException("Invalid PEM structure, " + endLine + " missing");

                  line = line.trim();

                  int sem_idx = line.indexOf(':');

                  if (sem_idx == -1)
                        break;

                  String name = line.substring(0, sem_idx + 1);
                  String value = line.substring(sem_idx + 1);

                  String values[] = value.split(",");

                  for (int i = 0; i < values.length; i++)
                        values[i] = values[i].trim();

                  // Proc-Type: 4,ENCRYPTED
                  // DEK-Info: DES-EDE3-CBC,579B6BE3E5C60483

                  if ("Proc-Type:".equals(name))
                  {
                        ps.procType = values;
                        continue;
                  }

                  if ("DEK-Info:".equals(name))
                  {
                        ps.dekInfo = values;
                        continue;
                  }
                  /* Ignore line */
            }

            StringBuffer keyData = new StringBuffer();

            while (true)
            {
                  if (line == null)
                        throw new IOException("Invalid PEM structure, " + endLine + " missing");

                  line = line.trim();

                  if (line.startsWith(endLine))
                        break;

                  keyData.append(line);

                  line = br.readLine();
            }

            char[] pem_chars = new char[keyData.length()];
            keyData.getChars(0, pem_chars.length, pem_chars, 0);

            ps.data = Base64.decode(pem_chars);

            if (ps.data.length == 0)
                  throw new IOException("Invalid PEM structure, no data available");

            return ps;
      }

      private static final void decryptPEM(PEMStructure ps, byte[] pw) throws IOException
      {
            if (ps.dekInfo == null)
                  throw new IOException("Broken PEM, no mode and salt given, but encryption enabled");

            if (ps.dekInfo.length != 2)
                  throw new IOException("Broken PEM, DEK-Info is incomplete!");

            String algo = ps.dekInfo[0];
            byte[] salt = hexToByteArray(ps.dekInfo[1]);

            BlockCipher bc = null;

            if (algo.equals("DES-EDE3-CBC"))
            {
                  DESede des3 = new DESede();
                  des3.init(false, generateKeyFromPasswordSaltWithMD5(pw, salt, 24));
                  bc = new CBCMode(des3, salt, false);
            }
            else if (algo.equals("DES-CBC"))
            {
                  DES des = new DES();
                  des.init(false, generateKeyFromPasswordSaltWithMD5(pw, salt, 8));
                  bc = new CBCMode(des, salt, false);
            }
            else if (algo.equals("AES-128-CBC"))
            {
                  AES aes = new AES();
                  aes.init(false, generateKeyFromPasswordSaltWithMD5(pw, salt, 16));
                  bc = new CBCMode(aes, salt, false);
            }
            else if (algo.equals("AES-192-CBC"))
            {
                  AES aes = new AES();
                  aes.init(false, generateKeyFromPasswordSaltWithMD5(pw, salt, 24));
                  bc = new CBCMode(aes, salt, false);
            }
            else if (algo.equals("AES-256-CBC"))
            {
                  AES aes = new AES();
                  aes.init(false, generateKeyFromPasswordSaltWithMD5(pw, salt, 32));
                  bc = new CBCMode(aes, salt, false);
            }
            else
            {
                  throw new IOException("Cannot decrypt PEM structure, unknown cipher " + algo);
            }

            if ((ps.data.length % bc.getBlockSize()) != 0)
                  throw new IOException("Invalid PEM structure, size of encrypted block is not a multiple of "
                              + bc.getBlockSize());

            /* Now decrypt the content */

            byte[] dz = new byte[ps.data.length];

            for (int i = 0; i < ps.data.length / bc.getBlockSize(); i++)
            {
                  bc.transformBlock(ps.data, i * bc.getBlockSize(), dz, i * bc.getBlockSize());
            }

            /* Now check and remove RFC 1423/PKCS #7 padding */

            dz = removePadding(dz, bc.getBlockSize());

            ps.data = dz;
            ps.dekInfo = null;
            ps.procType = null;
      }

      public static final boolean isPEMEncrypted(PEMStructure ps) throws IOException
      {
            if (ps.procType == null)
                  return false;

            if (ps.procType.length != 2)
                  throw new IOException("Unknown Proc-Type field.");

            if ("4".equals(ps.procType[0]) == false)
                  throw new IOException("Unknown Proc-Type field (" + ps.procType[0] + ")");

            if ("ENCRYPTED".equals(ps.procType[1]))
                  return true;

            return false;
      }

      public static Object decode(char[] pem, String password) throws IOException
      {
            PEMStructure ps = parsePEM(pem);

            if (isPEMEncrypted(ps))
            {
                  if (password == null)
                        throw new IOException("PEM is encrypted, but no password was specified");

                  decryptPEM(ps, password.getBytes());
            }

            if (ps.pemType == PEM_DSA_PRIVATE_KEY)
            {
                  SimpleDERReader dr = new SimpleDERReader(ps.data);

                  byte[] seq = dr.readSequenceAsByteArray();

                  if (dr.available() != 0)
                        throw new IOException("Padding in DSA PRIVATE KEY DER stream.");

                  dr.resetInput(seq);

                  BigInteger version = dr.readInt();

                  if (version.compareTo(BigInteger.ZERO) != 0)
                        throw new IOException("Wrong version (" + version + ") in DSA PRIVATE KEY DER stream.");

                  BigInteger p = dr.readInt();
                  BigInteger q = dr.readInt();
                  BigInteger g = dr.readInt();
                  BigInteger y = dr.readInt();
                  BigInteger x = dr.readInt();

                  if (dr.available() != 0)
                        throw new IOException("Padding in DSA PRIVATE KEY DER stream.");

                  return new DSAPrivateKey(p, q, g, y, x);
            }

            if (ps.pemType == PEM_RSA_PRIVATE_KEY)
            {
                  SimpleDERReader dr = new SimpleDERReader(ps.data);

                  byte[] seq = dr.readSequenceAsByteArray();

                  if (dr.available() != 0)
                        throw new IOException("Padding in RSA PRIVATE KEY DER stream.");

                  dr.resetInput(seq);

                  BigInteger version = dr.readInt();

                  if ((version.compareTo(BigInteger.ZERO) != 0) && (version.compareTo(BigInteger.ONE) != 0))
                        throw new IOException("Wrong version (" + version + ") in RSA PRIVATE KEY DER stream.");

                  BigInteger n = dr.readInt();
                  BigInteger e = dr.readInt();
                  BigInteger d = dr.readInt();

                  return new RSAPrivateKey(d, e, n);
            }

            throw new IOException("PEM problem: it is of unknown type");
      }

}

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