package org.bouncycastle.openssl;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.Reader;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.MessageDigest;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.spec.DSAPrivateKeySpec;
import java.security.spec.DSAPublicKeySpec;
import java.security.spec.KeySpec;
import java.security.spec.RSAPrivateCrtKeySpec;
import java.security.spec.RSAPublicKeySpec;
import java.util.StringTokenizer;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;

import org.bouncycastle.asn1.ASN1Sequence;
import org.bouncycastle.asn1.DERInputStream;
import org.bouncycastle.asn1.DERInteger;
import org.bouncycastle.util.encoders.Base64;
import org.bouncycastle.util.encoders.Hex;

/**
 * Class for reading OpenSSL PEM encoded streams containing 
 * X509 certificates and PKCS8 encoded keys 
 */
public class PEMReader extends BufferedReader
{
    private PasswordFinder  pFinder;
    private String          provider;

    /**
     * Create a new PEMReader
     *
     * @param reader the Reader
     */
    public PEMReader(
        Reader reader)
    {
        super(reader);
    }

    /**
     * Create a new PEMReader with a password finder
     *
     * @param reader the Reader
     * @param pFinder the password finder
     */
    public PEMReader(
        Reader          reader,
        PasswordFinder  pFinder)
    {
        this(reader, pFinder, "BC");
    }

    /**
     * Create a new PEMReader with a password finder
     *
     * @param reader the Reader
     * @param pFinder the password finder
     * @param provider the cryptography provider to use
     */
    public PEMReader(
        Reader          reader,
        PasswordFinder  pFinder,
        String          provider)
    {
        super(reader);

        this.pFinder = pFinder;
        this.provider = provider;
    }

    public Object readObject()
        throws IOException
    {
        String  line;

        while ((line = readLine()) != null)
        {
            if (line.indexOf("-----BEGIN CERTIFICATE") != -1)
            {
                return readCertificate("-----END CERTIFICATE");
            }
            if (line.indexOf("-----BEGIN X509 CERTIFICATE") != -1)
            {
                return readCertificate("-----END X509 CERTIFICATE");
            }
            else if (line.indexOf("-----BEGIN RSA PRIVATE KEY") != -1)
            {
                try
                {
                    return readKeyPair("RSA", "-----END RSA PRIVATE KEY");
                }
                catch (Exception e)
                {
                    throw new IOException(
                        "problem creating RSA private key: " + e.toString());
                }
            }
            else if (line.indexOf("-----BEGIN DSA PRIVATE KEY") != -1)
            {
                try
                {
                    return readKeyPair("DSA", "-----END DSA PRIVATE KEY");
                }
                catch (Exception e)
                {
                    e.printStackTrace();
                    throw new IOException(
                        "problem creating RSA private key: " + e.toString());
                }
            }
        }

        return null;
    }

    /**
     * Reads in a X509Certificate.
     *
     * @return the X509Certificate
     * @throws IOException if an I/O error occured
     */
    private X509Certificate readCertificate(
        String  endMarker)
        throws IOException
    {
        String          line;
        StringBuffer    buf = new StringBuffer();
  
        while ((line = readLine()) != null)
        {
            if (line.indexOf(endMarker) != -1)
            {
                break;
            }
            buf.append(line.trim());
        }

        if (line == null)
        {
            throw new IOException(endMarker + " not found");
        }

        ByteArrayInputStream    bIn = new ByteArrayInputStream(
                                                Base64.decode(buf.toString()));

        try
        {
            CertificateFactory certFact
                    = CertificateFactory.getInstance("X.509", provider);

            return (X509Certificate)certFact.generateCertificate(bIn);
        }
        catch (Exception e)
        {
            throw new IOException("problem parsing cert: " + e.toString());
        }
    }

    /**
     * create the secret key needed for this object, fetching the password
     */
    private SecretKey getKey(
        String  algorithm,
        int     keyLength,
        byte[]  salt)
        throws IOException
    {
        byte[]      key = new byte[keyLength];
        int         offset = 0;
        int         bytesNeeded = keyLength;

        if (pFinder == null)
        {
            throw new IOException("No password finder specified, but a password is required");
        }

        char[]      password = pFinder.getPassword();

        if (password == null)
        {
            throw new IOException("Password is null, but a password is required");
        }

        MessageDigest md5;
        
        try
        {
            md5 = MessageDigest.getInstance("MD5");
        }
        catch (Exception e)
        {
            throw new IOException("can't create digest: " + e.toString());
        }

        for (;;)
        {
            for (int i = 0; i != password.length; i++)
            {
                md5.update((byte)password[i]);
            }
            md5.update(salt);

            byte[] b = md5.digest();
            int len = (bytesNeeded > b.length) ? b.length : bytesNeeded;
            System.arraycopy(b, 0, key, offset, len);
            offset += len;

            // check if we need any more
            bytesNeeded = key.length - offset;
            if (bytesNeeded == 0)
            {
                break;
            }

            // do another round
            md5.reset();
            md5.update(b);
        }

        return new javax.crypto.spec.SecretKeySpec(key, algorithm);
    }

    /**
     * Read a Key Pair
     */
    private KeyPair readKeyPair(
        String  type,
        String  endMarker)
        throws Exception
    {
        boolean         isEncrypted = false;
        String          line = null;
        String          dekInfo = null;
        StringBuffer    buf = new StringBuffer();

        while ((line = readLine()) != null)
        {
            if (line.startsWith("Proc-Type: 4,ENCRYPTED"))
            {
                isEncrypted = true;
            }
            else if (line.startsWith("DEK-Info:"))
            {
                dekInfo = line.substring(10);
            }
            else if (line.indexOf(endMarker) != -1)
            {
                break;
            }
            else
            {
                buf.append(line.trim());
            }
	    }

        //
        // extract the key
        //
        byte[]  keyBytes = null;

        if (isEncrypted)
        {
            StringTokenizer tknz = new StringTokenizer(dekInfo, ",");
            String          encoding = tknz.nextToken();

            if (encoding.equals("DES-EDE3-CBC"))
            {
                String  alg = "DESede";
                byte[]  iv = Hex.decode(tknz.nextToken());
                Key     sKey = getKey(alg, 24, iv);
                Cipher  c = Cipher.getInstance(
                                "DESede/CBC/PKCS5Padding", provider);

                c.init(Cipher.DECRYPT_MODE, sKey, new IvParameterSpec(iv));
                keyBytes = c.doFinal(Base64.decode(buf.toString()));
            }
            else if (encoding.equals("DES-CBC"))
            {
                String  alg = "DES";
                byte[]  iv = Hex.decode(tknz.nextToken());
                Key     sKey = getKey(alg, 8, iv);
                Cipher  c = Cipher.getInstance(
                                "DES/CBC/PKCS5Padding", provider);

                c.init(Cipher.DECRYPT_MODE, sKey, new IvParameterSpec(iv));
                keyBytes = c.doFinal(Base64.decode(buf.toString()));
            }
            else
            {
                throw new IOException("unknown encryption with private key");
            }
	    }
        else
        {
            keyBytes = Base64.decode(buf.toString());
        }

        KeySpec                 pubSpec, privSpec;
        ByteArrayInputStream    bIn = new ByteArrayInputStream(keyBytes);
        DERInputStream          dIn = new DERInputStream(bIn);
        ASN1Sequence            seq = (ASN1Sequence)dIn.readObject();

        if (type.equals("RSA"))
        {
            DERInteger              v = (DERInteger)seq.getObjectAt(0);
            DERInteger              mod = (DERInteger)seq.getObjectAt(1);
            DERInteger              pubExp = (DERInteger)seq.getObjectAt(2);
            DERInteger              privExp = (DERInteger)seq.getObjectAt(3);
            DERInteger              p1 = (DERInteger)seq.getObjectAt(4);
            DERInteger              p2 = (DERInteger)seq.getObjectAt(5);
            DERInteger              exp1 = (DERInteger)seq.getObjectAt(6);
            DERInteger              exp2 = (DERInteger)seq.getObjectAt(7);
            DERInteger              crtCoef = (DERInteger)seq.getObjectAt(8);

            pubSpec = new RSAPublicKeySpec(
                        mod.getValue(), pubExp.getValue());
            privSpec = new RSAPrivateCrtKeySpec(
                    mod.getValue(), pubExp.getValue(), privExp.getValue(),
                    p1.getValue(), p2.getValue(),
                    exp1.getValue(), exp2.getValue(),
                    crtCoef.getValue());
        }
        else    // "DSA"
        {
            DERInteger              v = (DERInteger)seq.getObjectAt(0);
            DERInteger              p = (DERInteger)seq.getObjectAt(1);
            DERInteger              q = (DERInteger)seq.getObjectAt(2);
            DERInteger              g = (DERInteger)seq.getObjectAt(3);
            DERInteger              y = (DERInteger)seq.getObjectAt(4);
            DERInteger              x = (DERInteger)seq.getObjectAt(5);

            privSpec = new DSAPrivateKeySpec(
                        x.getValue(), p.getValue(),
                            q.getValue(), g.getValue());
            pubSpec = new DSAPublicKeySpec(
                        y.getValue(), p.getValue(),
                            q.getValue(), g.getValue());
        }

        KeyFactory          fact = KeyFactory.getInstance(type, provider);

        return new KeyPair(
                    fact.generatePublic(pubSpec),
                    fact.generatePrivate(privSpec));
    }
}
