package org.jboss.resteasy.jose.jwe.crypto;
import org.jboss.resteasy.jose.Base64Url;
import org.jboss.resteasy.jose.jwe.Algorithm;
import org.jboss.resteasy.jose.jwe.EncryptionMethod;
import org.jboss.resteasy.jose.jwe.JWEHeader;
import javax.crypto.SecretKey;
import java.nio.charset.Charset;
/**
* Direct decrypter with a
* shared symmetric key. This class is thread-safe.
* <p/>
* <p>Supports the following JWE algorithms:
* <p/>
* <ul>
* <li>DIR
* </ul>
* <p/>
* <p>Supports the following encryption methods:
* <p/>
* <ul>
* <li>A128CBC_HS256
* <li>A256CBC_HS512
* <li>A128GCM
* <li>A256GCM
* </ul>
*
* @author Vladimir Dzhuvinov
* @version $version$ (2013-05-29)
*/
public class DirectDecrypter
{
public static byte[] decrypt(final SecretKey key,
final JWEHeader readOnlyJWEHeader,
final String encodedHeader,
final String encryptedKey,
final String encodedIv,
final String encodedCipherText,
final String encodedAuthTag
)
{
// Validate required JWE parts
if (encryptedKey != null)
{
throw new RuntimeException("Unexpected encrypted key, must be omitted");
}
if (encodedIv == null)
{
throw new RuntimeException("The initialization vector (IV) must not be null");
}
if (encodedAuthTag == null)
{
throw new RuntimeException("The authentication tag must not be null");
}
Algorithm alg = readOnlyJWEHeader.getAlgorithm();
if (!alg.equals(Algorithm.dir))
{
throw new RuntimeException("Unsupported algorithm, must be \"dir\"");
}
// Compose the AAD
byte[] aad = encodedHeader.getBytes(Charset.forName("UTF-8"));
byte[] iv = Base64Url.decode(encodedIv);
byte[] cipherText = Base64Url.decode(encodedCipherText);
byte[] authTag = Base64Url.decode(encodedAuthTag);
// Decrypt the cipher text according to the JWE enc
EncryptionMethod enc = readOnlyJWEHeader.getEncryptionMethod();
byte[] plainText;
if (enc.equals(EncryptionMethod.A128CBC_HS256) || enc.equals(EncryptionMethod.A256CBC_HS512))
{
plainText = AESCBC.decryptAuthenticated(key, iv, cipherText, aad, authTag);
}
else if (enc.equals(EncryptionMethod.A128GCM) || enc.equals(EncryptionMethod.A256GCM))
{
plainText = AESGCM.decrypt(key, iv, cipherText, aad, authTag);
}
else
{
throw new RuntimeException("Unsupported encryption method, must be A128CBC_HS256, A256CBC_HS512, A128GCM or A128GCM");
}
// Apply decompression if requested
return DeflateHelper.applyDecompression(readOnlyJWEHeader.getCompressionAlgorithm(), plainText);
}
}