updated decryption to generate cik and cek based off of key derivation

pull/105/head
Mike Derryberry 13 years ago
parent d86ee2329b
commit 26792d2fba

@ -1,5 +1,6 @@
package org.mitre.jwt.encryption;
import java.security.MessageDigest;
import java.security.PrivateKey;
import java.security.PublicKey;
@ -9,6 +10,8 @@ public abstract class AbstractJweDecrypter implements JwtDecrypter {
private PublicKey publicKey;
public MessageDigest md;
public PrivateKey getPrivateKey() {
return privateKey;
}
@ -24,4 +27,46 @@ public abstract class AbstractJweDecrypter implements JwtDecrypter {
public void setPublicKey(PublicKey publicKey) {
this.publicKey = publicKey;
}
public byte[] generateContentKey(byte[] cmk, int keyDataLen, byte[] type) {
long MAX_HASH_INPUTLEN = Long.MAX_VALUE;
long UNSIGNED_INT_MAX_VALUE = 4294967395L;
keyDataLen = keyDataLen / 8;
byte[] key = new byte[keyDataLen];
int hashLen = md.getDigestLength();
int reps = keyDataLen / hashLen;
if (reps > UNSIGNED_INT_MAX_VALUE) {
throw new IllegalArgumentException("Key derivation failed");
}
int counter = 1;
byte[] counterInBytes = intToFourBytes(counter);
if ((counterInBytes.length + cmk.length + type.length) * 8 > MAX_HASH_INPUTLEN) {
throw new IllegalArgumentException("Key derivation failed");
}
for (int i = 0; i <= reps; i++) {
md.reset();
md.update(intToFourBytes(i + 1));
md.update(cmk);
md.update(type);
byte[] hash = md.digest();
if (i < reps) {
System.arraycopy(hash, 0, key, hashLen * i, hashLen);
} else {
System.arraycopy(hash, 0, key, hashLen * i, keyDataLen % hashLen);
}
}
return key;
}
public byte[] intToFourBytes(int i) {
byte[] res = new byte[4];
res[0] = (byte) (i >>> 24);
res[1] = (byte) ((i >>> 16) & 0xFF);
res[2] = (byte) ((i >>> 8) & 0xFF);
res[3] = (byte) (i & 0xFF);
return res;
}
}

@ -6,15 +6,18 @@ public enum JwtAlgorithm {
//TODO:Fill in values for each standard name
// RSA
RSA1_5(""),
RSA_OAEP(""),
RSA1_5("RSA"),
RSA_OAEP("RSA"),
//EC
ECDH_ES(""),
ECDH_ES("EC"),
//AES
A128KW(""),
A256KW(""),
A128GCM(""),
A256GCM("");
A128KW("AES"),
A256KW("AES"),
A128CBC("AES"),
A256CBC("AES"),
A128GCM("AES"),
A256GCM("AES");
/**

@ -1,14 +1,12 @@
package org.mitre.jwt.encryption;
import java.security.Key;
import org.mitre.jwe.model.Jwe;
public interface JwtDecrypter {
public Jwe decrypt(String encryptedJwe);
public String decryptCipherText(Jwe jwe, Key cek);
public byte[] decryptCipherText(Jwe jwe, byte[] cek);
public byte[] decryptEncryptionKey(Jwe jwe);

@ -1,20 +1,17 @@
package org.mitre.jwt.encryption.impl;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;
import org.mitre.jwe.model.Jwe;
import org.mitre.jwt.encryption.AbstractJweDecrypter;
import org.mitre.jwt.encryption.AlgorithmLength;
import org.mitre.jwt.signer.impl.HmacSigner;
@ -31,29 +28,23 @@ public class RsaDecrypter extends AbstractJweDecrypter {
String alg = jwe.getHeader().getAlgorithm();
if(alg.equals("RS256") || alg.equals("RS384") || alg.equals("RS512")) {
PrivateKey contentEncryptionKey = null;
PublicKey contentIntegrityKey = null;
try {
KeyPairGenerator keyGen = KeyPairGenerator.getInstance(jwe.getHeader().getKeyDerivationFunction());
KeyPair keyPair = keyGen.genKeyPair();
contentEncryptionKey = keyPair.getPrivate();
contentIntegrityKey = keyPair.getPublic();
} catch (NoSuchAlgorithmException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
jwe.setCiphertext(decryptCipherText(jwe, contentEncryptionKey).getBytes());
//decrypt to get cmk to be used for cek and cik
jwe.setEncryptedKey(decryptEncryptionKey(jwe));
//generation of cek and cik
String algorithmLength = AlgorithmLength.getByName(jwe.getHeader().getEncryptionMethod()).getStandardName();
int keyLength = Integer.parseInt(algorithmLength);
byte[] contentEncryptionKey = generateContentKey(jwe.getEncryptedKey(), keyLength, new String("Encryption").getBytes());
byte[] contentIntegrityKey = generateContentKey(jwe.getEncryptedKey(), keyLength, new String("Integrity").getBytes());
//decrypt ciphertext to get claims
jwe.setCiphertext(decryptCipherText(jwe, contentEncryptionKey));
//generate signature for decrypted signature base in order to verify that decryption worked
String signature = null;
try {
HmacSigner hmacSigner = new HmacSigner(contentIntegrityKey.getEncoded());
HmacSigner hmacSigner = new HmacSigner(contentIntegrityKey);
signature = hmacSigner.generateSignature(jwe.getSignatureBase());
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
@ -76,15 +67,14 @@ public class RsaDecrypter extends AbstractJweDecrypter {
}
@Override
public String decryptCipherText(Jwe jwe, Key cek) {
public byte[] decryptCipherText(Jwe jwe, byte[] cek) {
Cipher cipher;
String clearTextString = null;
byte[] clearText = null;
try {
cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, cek);
byte[] clearText = cipher.doFinal(jwe.getCiphertext());
clearTextString = new String(clearText);
cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(cek, "RSA"));
clearText = cipher.doFinal(jwe.getCiphertext());
} catch (NoSuchAlgorithmException e) {
// TODO Auto-generated catch block
@ -103,7 +93,7 @@ public class RsaDecrypter extends AbstractJweDecrypter {
e.printStackTrace();
}
return clearTextString;
return clearText;
}

@ -115,9 +115,9 @@ public class RsaEncrypter extends AbstractJweEncrypter {
Cipher cipher;
try {
cipher = Cipher.getInstance(JwtAlgorithm.getByName(jwe.getHeader().getAlgorithm()).getStandardName());
cipher = Cipher.getInstance(JwtAlgorithm.getByName(jwe.getHeader().getEncryptionMethod()).getStandardName());
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(contentEncryptionKey, 0, contentEncryptionKey.length, "RSA"));
cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(contentEncryptionKey, "RSA"));
cipherText = cipher.doFinal(jwe.getClaims().toString().getBytes());
} catch (NoSuchAlgorithmException e) {

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