net.oauth.jsontoken.crypto.MagicRsaPublicKey Maven / Gradle / Ivy
/**
* Copyright 2010 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 net.oauth.jsontoken.crypto;
import org.apache.commons.codec.binary.Base64;
import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.RSAPublicKeySpec;
import java.util.regex.Pattern;
/**
* Class that can parse "magic key" RSA public key representations, which are of the form
* RSA...
*/
public class MagicRsaPublicKey {
private final PublicKey publicKey;
/**
* Public constructor.
* @param magicKey the serialized key (of the form RSA.modulus.exponent).
*/
public MagicRsaPublicKey(String magicKey) {
this.publicKey = parseKey(magicKey);
}
/**
* Returns the public key represented by the "magic" serialized key.
*/
public PublicKey getKey() {
return publicKey;
}
private static PublicKey parseKey(String magicKey) {
String[] pieces = magicKey.split(Pattern.quote("."));
if (pieces.length != 3) {
throw new IllegalStateException("not a valid magic key: " + magicKey);
}
if (!pieces[0].equals("RSA")) {
throw new IllegalStateException("unkown key type for magic key: " + pieces[0]);
}
String modulusString = pieces[1];
String exponentString = pieces[2];
byte[] modulusBytes = Base64.decodeBase64(modulusString);
byte[] exponentBytes = Base64.decodeBase64(exponentString);
BigInteger modulus = new BigInteger(modulusBytes);
BigInteger exponent = new BigInteger(exponentBytes);
RSAPublicKeySpec spec = new RSAPublicKeySpec(modulus, exponent);
KeyFactory fac;
try {
fac = KeyFactory.getInstance("RSA");
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException("RSA key factory missing on platform", e);
}
try {
return fac.generatePublic(spec);
} catch (InvalidKeySpecException e) {
throw new IllegalStateException("bad key in descripor doc: " + magicKey, e);
}
}
}