crypto/provider/KeyProtector.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * particular file as subject to the "Classpath" exception as provided
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package com.sun.crypto.provider;

import java.io.IOException;
import java.io.Serializable;
import java.security.Security;
import java.security.Key;
import java.security.PrivateKey;
import java.security.Provider;
import java.security.KeyFactory;
import java.security.MessageDigest;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.UnrecoverableKeyException;
import java.security.AlgorithmParameters;
import java.security.spec.PKCS8EncodedKeySpec;

import javax.crypto.Cipher;
import javax.crypto.CipherSpi;
import javax.crypto.SecretKey;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.SealedObject;
import javax.crypto.spec.*;
import sun.security.x509.AlgorithmId;
import sun.security.util.ObjectIdentifier;

/**
 * This class implements a protection mechanism for private keys. In JCE, we
 * use a stronger protection mechanism than in the JDK, because we can use
 * the <code>Cipher</code> class.
 * Private keys are protected using the JCE mechanism, and are recovered using
 * either the JDK or JCE mechanism, depending on how the key has been
 * protected. This allows us to parse Sun's keystore implementation that ships
 * with JDK 1.2.
 *
 * @author Jan Luehe
 *
 *
 * @see JceKeyStore
 */

final class KeyProtector {

    // defined by SunSoft (SKI project)
    private static final String PBE_WITH_MD5_AND_DES3_CBC_OID
            = "1.3.6.1.4.1.42.2.19.1";

    // JavaSoft proprietary key-protection algorithm (used to protect private
    // keys in the keystore implementation that comes with JDK 1.2)
    private static final String KEY_PROTECTOR_OID = "1.3.6.1.4.1.42.2.17.1.1";

    private static final int SALT_LEN = 20; // the salt length
    private static final int DIGEST_LEN = 20;

    // the password used for protecting/recovering keys passed through this
    // key protector
    private char[] password;

    KeyProtector(char[] password) {
        if (password == null) {
           throw new IllegalArgumentException("password can't be null");
        }
        this.password = password;
    }

    /**
     * Protects the given cleartext private key, using the password provided at
     * construction time.
     */
    byte[] protect(PrivateKey key)
        throws Exception
    {
        // create a random salt (8 bytes)
        byte[] salt = new byte[8];
        SunJCE.getRandom().nextBytes(salt);

        // create PBE parameters from salt and iteration count
        PBEParameterSpec pbeSpec = new PBEParameterSpec(salt, 20);

        // create PBE key from password
        PBEKeySpec pbeKeySpec = new PBEKeySpec(this.password);
        SecretKey sKey = new PBEKey(pbeKeySpec, "PBEWithMD5AndTripleDES");
        pbeKeySpec.clearPassword();

        // encrypt private key
        PBEWithMD5AndTripleDESCipher cipher;
        cipher = new PBEWithMD5AndTripleDESCipher();
        cipher.engineInit(Cipher.ENCRYPT_MODE, sKey, pbeSpec, null);
        byte[] plain = key.getEncoded();
        byte[] encrKey = cipher.engineDoFinal(plain, 0, plain.length);

        // wrap encrypted private key in EncryptedPrivateKeyInfo
        // (as defined in PKCS#8)
        AlgorithmParameters pbeParams =
            AlgorithmParameters.getInstance("PBE", SunJCE.getInstance());
        pbeParams.init(pbeSpec);

        AlgorithmId encrAlg = new AlgorithmId
            (new ObjectIdentifier(PBE_WITH_MD5_AND_DES3_CBC_OID), pbeParams);
        return new EncryptedPrivateKeyInfo(encrAlg,encrKey).getEncoded();
    }

    /*
     * Recovers the cleartext version of the given key (in protected format),
     * using the password provided at construction time.
     */
    Key recover(EncryptedPrivateKeyInfo encrInfo)
        throws UnrecoverableKeyException, NoSuchAlgorithmException
    {
        byte[] plain;

        try {
            String encrAlg = encrInfo.getAlgorithm().getOID().toString();
            if (!encrAlg.equals(PBE_WITH_MD5_AND_DES3_CBC_OID)
                && !encrAlg.equals(KEY_PROTECTOR_OID)) {
                throw new UnrecoverableKeyException("Unsupported encryption "
                                                    + "algorithm");
            }

            if (encrAlg.equals(KEY_PROTECTOR_OID)) {
                // JDK 1.2 style recovery
                plain = recover(encrInfo.getEncryptedData());
            } else {
                byte[] encodedParams =
                    encrInfo.getAlgorithm().getEncodedParams();

                // parse the PBE parameters into the corresponding spec
                AlgorithmParameters pbeParams =
                    AlgorithmParameters.getInstance("PBE");
                pbeParams.init(encodedParams);
                PBEParameterSpec pbeSpec =
                        pbeParams.getParameterSpec(PBEParameterSpec.class);

                // create PBE key from password
                PBEKeySpec pbeKeySpec = new PBEKeySpec(this.password);
                SecretKey sKey =
                    new PBEKey(pbeKeySpec, "PBEWithMD5AndTripleDES");
                pbeKeySpec.clearPassword();

                // decrypt private key
                PBEWithMD5AndTripleDESCipher cipher;
                cipher = new PBEWithMD5AndTripleDESCipher();
                cipher.engineInit(Cipher.DECRYPT_MODE, sKey, pbeSpec, null);
                plain=cipher.engineDoFinal(encrInfo.getEncryptedData(), 0,
                                           encrInfo.getEncryptedData().length);
            }

            // determine the private-key algorithm, and parse private key
            // using the appropriate key factory
            String oidName = new AlgorithmId
                (new PrivateKeyInfo(plain).getAlgorithm().getOID()).getName();
            KeyFactory kFac = KeyFactory.getInstance(oidName);
            return kFac.generatePrivate(new PKCS8EncodedKeySpec(plain));

        } catch (NoSuchAlgorithmException ex) {
            // Note: this catch needed to be here because of the
            // later catch of GeneralSecurityException
            throw ex;
        } catch (IOException ioe) {
            throw new UnrecoverableKeyException(ioe.getMessage());
        } catch (GeneralSecurityException gse) {
            throw new UnrecoverableKeyException(gse.getMessage());
        }
    }

    /*
     * Recovers the cleartext version of the given key (in protected format),
     * using the password provided at construction time. This method implements
     * the recovery algorithm used by Sun's keystore implementation in
     * JDK 1.2.
     */
    private byte[] recover(byte[] protectedKey)
        throws UnrecoverableKeyException, NoSuchAlgorithmException
    {
        int i, j;
        byte[] digest;
        int numRounds;
        int xorOffset; // offset in xorKey where next digest will be stored
        int encrKeyLen; // the length of the encrpyted key

        MessageDigest md = MessageDigest.getInstance("SHA");

        // Get the salt associated with this key (the first SALT_LEN bytes of
        // <code>protectedKey</code>)
        byte[] salt = new byte[SALT_LEN];
        System.arraycopy(protectedKey, 0, salt, 0, SALT_LEN);

        // Determine the number of digest rounds
        encrKeyLen = protectedKey.length - SALT_LEN - DIGEST_LEN;
        numRounds = encrKeyLen / DIGEST_LEN;
        if ((encrKeyLen % DIGEST_LEN) != 0)
            numRounds++;

        // Get the encrypted key portion and store it in "encrKey"
        byte[] encrKey = new byte[encrKeyLen];
        System.arraycopy(protectedKey, SALT_LEN, encrKey, 0, encrKeyLen);

        // Set up the byte array which will be XORed with "encrKey"
        byte[] xorKey = new byte[encrKey.length];

        // Convert password to byte array, so that it can be digested
        byte[] passwdBytes = new byte[password.length * 2];
        for (i=0, j=0; i<password.length; i++) {
            passwdBytes[j++] = (byte)(password[i] >> 8);
            passwdBytes[j++] = (byte)password[i];
        }

        // Compute the digests, and store them in "xorKey"
        for (i = 0, xorOffset = 0, digest = salt;
             i < numRounds;
             i++, xorOffset += DIGEST_LEN) {
            md.update(passwdBytes);
            md.update(digest);
            digest = md.digest();
            md.reset();
            // Copy the digest into "xorKey"
            if (i < numRounds - 1) {
                System.arraycopy(digest, 0, xorKey, xorOffset,
                                 digest.length);
            } else {
                System.arraycopy(digest, 0, xorKey, xorOffset,
                                 xorKey.length - xorOffset);
            }
        }

        // XOR "encrKey" with "xorKey", and store the result in "plainKey"
        byte[] plainKey = new byte[encrKey.length];
        for (i = 0; i < plainKey.length; i++) {
            plainKey[i] = (byte)(encrKey[i] ^ xorKey[i]);
        }

        // Check the integrity of the recovered key by concatenating it with
        // the password, digesting the concatenation, and comparing the
        // result of the digest operation with the digest provided at the end
        // of <code>protectedKey</code>. If the two digest values are
        // different, throw an exception.
        md.update(passwdBytes);
        java.util.Arrays.fill(passwdBytes, (byte)0x00);
        passwdBytes = null;
        md.update(plainKey);
        digest = md.digest();
        md.reset();
        for (i = 0; i < digest.length; i++) {
            if (digest[i] != protectedKey[SALT_LEN + encrKeyLen + i]) {
                throw new UnrecoverableKeyException("Cannot recover key");
            }
        }
        return plainKey;
    }

    /**
     * Seals the given cleartext key, using the password provided at
     * construction time
     */
    SealedObject seal(Key key)
        throws Exception
    {
        // create a random salt (8 bytes)
        byte[] salt = new byte[8];
        SunJCE.getRandom().nextBytes(salt);

        // create PBE parameters from salt and iteration count
        PBEParameterSpec pbeSpec = new PBEParameterSpec(salt, 20);

        // create PBE key from password
        PBEKeySpec pbeKeySpec = new PBEKeySpec(this.password);
        SecretKey sKey = new PBEKey(pbeKeySpec, "PBEWithMD5AndTripleDES");
        pbeKeySpec.clearPassword();

        // seal key
        Cipher cipher;

        PBEWithMD5AndTripleDESCipher cipherSpi;
        cipherSpi = new PBEWithMD5AndTripleDESCipher();
        cipher = new CipherForKeyProtector(cipherSpi, SunJCE.getInstance(),
                                           "PBEWithMD5AndTripleDES");
        cipher.init(Cipher.ENCRYPT_MODE, sKey, pbeSpec);
        return new SealedObjectForKeyProtector(key, cipher);
    }

    /**
     * Unseals the sealed key.
     */
    Key unseal(SealedObject so)
        throws NoSuchAlgorithmException, UnrecoverableKeyException
    {
        try {
            // create PBE key from password
            PBEKeySpec pbeKeySpec = new PBEKeySpec(this.password);
            SecretKey skey = new PBEKey(pbeKeySpec, "PBEWithMD5AndTripleDES");
            pbeKeySpec.clearPassword();

            SealedObjectForKeyProtector soForKeyProtector = null;
            if (!(so instanceof SealedObjectForKeyProtector)) {
                soForKeyProtector = new SealedObjectForKeyProtector(so);
            } else {
                soForKeyProtector = (SealedObjectForKeyProtector)so;
            }
            AlgorithmParameters params = soForKeyProtector.getParameters();
            if (params == null) {
                throw new UnrecoverableKeyException("Cannot get " +
                                                    "algorithm parameters");
            }
            PBEWithMD5AndTripleDESCipher cipherSpi;
            cipherSpi = new PBEWithMD5AndTripleDESCipher();
            Cipher cipher = new CipherForKeyProtector(cipherSpi,
                                                      SunJCE.getInstance(),
                                                      "PBEWithMD5AndTripleDES");
            cipher.init(Cipher.DECRYPT_MODE, skey, params);
            return (Key)soForKeyProtector.getObject(cipher);
        } catch (NoSuchAlgorithmException ex) {
            // Note: this catch needed to be here because of the
            // later catch of GeneralSecurityException
            throw ex;
        } catch (IOException ioe) {
            throw new UnrecoverableKeyException(ioe.getMessage());
        } catch (ClassNotFoundException cnfe) {
            throw new UnrecoverableKeyException(cnfe.getMessage());
        } catch (GeneralSecurityException gse) {
            throw new UnrecoverableKeyException(gse.getMessage());
        }
    }
}


final class CipherForKeyProtector extends javax.crypto.Cipher {
    /**
     * Creates a Cipher object.
     *
     * @param cipherSpi the delegate
     * @param provider the provider
     * @param transformation the transformation
     */
    protected CipherForKeyProtector(CipherSpi cipherSpi,
                                    Provider provider,
                                    String transformation) {
        super(cipherSpi, provider, transformation);
    }
}