/*
* Copyright 2008 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.keyczar;
import com.google.gson.annotations.Expose;
import org.keyczar.exceptions.KeyczarException;
import org.keyczar.interfaces.KeyType;
import org.keyczar.interfaces.Stream;
import org.keyczar.interfaces.VerifyingStream;
import org.keyczar.util.Base64Coder;
import org.keyczar.util.Util;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.interfaces.DSAParams;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.DSAPublicKey;
import java.security.spec.DSAPublicKeySpec;
/**
* Wrapping class for DSA Public Keys. These must be exported from existing DSA
* private key sets.
*
* @author steveweis@gmail.com (Steve Weis)
*/
public class DsaPublicKey extends KeyczarPublicKey {
private static final String KEY_GEN_ALGORITHM = "DSA";
private static final String SIG_ALGORITHM = "SHA1withDSA";
private static final int DSA_DIGEST_SIZE = 48;
private DSAPublicKey jcePublicKey;
private final byte[] hash = new byte[Keyczar.KEY_HASH_SIZE];
@Expose final String y;
@Expose final String p;
@Expose final String q;
@Expose final String g;
static DsaPublicKey read(String input) throws KeyczarException {
DsaPublicKey key = Util.gson().fromJson(input, DsaPublicKey.class);
key.initFromJson();
return key;
}
/**
* Constructs a new {@link DsaPublicKey} from the provided JCE {@link DSAPublicKey}.
*/
DsaPublicKey(DSAPublicKey jcePublicKey) throws KeyczarException {
this(jcePublicKey.getY(), jcePublicKey.getParams());
}
/**
* Constructs a new {@link DsaPublicKey} from the provided JCE {@link DSAPrivateKey}.
*/
DsaPublicKey(DSAPrivateKey jcePrivateKey) throws KeyczarException {
this(computeY(jcePrivateKey), jcePrivateKey.getParams());
}
// Used by GSON, which will overwrite the values set here.
private DsaPublicKey() {
super(0);
jcePublicKey = null;
y = p = q = g = null;
}
private DsaPublicKey(BigInteger yVal, DSAParams params) throws KeyczarException {
super(params.getP().bitLength());
BigInteger pVal = params.getP();
BigInteger qVal = params.getQ();
BigInteger gVal = params.getG();
y = Base64Coder.encodeWebSafe(yVal.toByteArray());
p = Base64Coder.encodeWebSafe(pVal.toByteArray());
q = Base64Coder.encodeWebSafe(qVal.toByteArray());
g = Base64Coder.encodeWebSafe(gVal.toByteArray());
initializeJceKey(yVal, pVal, qVal, gVal);
initializeHash();
}
private static BigInteger computeY(DSAPrivateKey jcePrivateKey) {
final BigInteger p = jcePrivateKey.getParams().getP();
final BigInteger g = jcePrivateKey.getParams().getG();
final BigInteger x = jcePrivateKey.getX();
return g.modPow(x, p);
}
@Override
protected Stream getStream() throws KeyczarException {
return new DsaVerifyingStream();
}
@Override
public KeyType getType() {
return DefaultKeyType.DSA_PUB;
}
@Override
public byte[] hash() {
return hash;
}
/**
* Initialize JCE key from JSON data. Must be called after an instance is read from JSON.
* In default scope so {@link DsaPrivateKey} can call it when a private key string (which
* contains a public key string) is deserialized.
*/
void initFromJson() throws KeyczarException {
BigInteger yVal = new BigInteger(Base64Coder.decodeWebSafe(y));
BigInteger pVal = new BigInteger(Base64Coder.decodeWebSafe(p));
BigInteger qVal = new BigInteger(Base64Coder.decodeWebSafe(q));
BigInteger gVal = new BigInteger(Base64Coder.decodeWebSafe(g));
initializeJceKey(yVal, pVal, qVal, gVal);
initializeHash();
}
private void initializeJceKey(BigInteger yVal, BigInteger pVal, BigInteger qVal,
BigInteger gVal) throws KeyczarException {
try {
KeyFactory kf = KeyFactory.getInstance(KEY_GEN_ALGORITHM);
jcePublicKey = (DSAPublicKey) kf.generatePublic(new DSAPublicKeySpec(yVal, pVal, qVal, gVal));
} catch (GeneralSecurityException e) {
throw new KeyczarException(e);
}
}
private void initializeHash() throws KeyczarException {
final DSAParams dsaParams = jcePublicKey.getParams();
final byte[] fullHash = Util.prefixHash(
Util.stripLeadingZeros(dsaParams.getP().toByteArray()),
Util.stripLeadingZeros(dsaParams.getQ().toByteArray()),
Util.stripLeadingZeros(dsaParams.getG().toByteArray()),
Util.stripLeadingZeros(jcePublicKey.getY().toByteArray()));
System.arraycopy(fullHash, 0, hash, 0, hash.length);
}
@Override
protected PublicKey getJceKey() {
return jcePublicKey;
}
@Override
protected boolean isSecret() {
return false;
}
private class DsaVerifyingStream implements VerifyingStream {
private Signature signature;
public DsaVerifyingStream() throws KeyczarException {
try {
signature = Signature.getInstance(SIG_ALGORITHM);
} catch (GeneralSecurityException e) {
throw new KeyczarException(e);
}
}
@Override
public int digestSize() {
return DSA_DIGEST_SIZE;
}
@Override
public void initVerify() throws KeyczarException {
try {
signature.initVerify(jcePublicKey);
} catch (GeneralSecurityException e) {
throw new KeyczarException(e);
}
}
@Override
public void updateVerify(ByteBuffer input) throws KeyczarException {
try {
signature.update(input);
} catch (SignatureException e) {
throw new KeyczarException(e);
}
}
@Override
public boolean verify(ByteBuffer sig) throws KeyczarException {
try {
return signature.verify(sig.array(), sig.position(), sig.limit()
- sig.position());
} catch (GeneralSecurityException e) {
throw new KeyczarException(e);
}
}
}
}