private byte[] extractKeyData(PBESecretKeyDecryptor decryptorFactory) throws PGPException {
byte[] encData = secret.getSecretKeyData();
byte[] data = null;
if (secret.getEncAlgorithm() != SymmetricKeyAlgorithmTags.NULL) {
try {
if (secret.getPublicKeyPacket().getVersion() == 4) {
byte[] key =
decryptorFactory.makeKeyFromPassPhrase(secret.getEncAlgorithm(), secret.getS2K());
data =
decryptorFactory.recoverKeyData(
secret.getEncAlgorithm(), key, secret.getIV(), encData, 0, encData.length);
boolean useSHA1 = secret.getS2KUsage() == SecretKeyPacket.USAGE_SHA1;
byte[] check =
checksum(
useSHA1 ? decryptorFactory.getChecksumCalculator(HashAlgorithmTags.SHA1) : null,
data,
(useSHA1) ? data.length - 20 : data.length - 2);
for (int i = 0; i != check.length; i++) {
if (check[i] != data[data.length - check.length + i]) {
throw new PGPException("checksum mismatch at " + i + " of " + check.length);
}
}
} else // version 2 or 3, RSA only.
{
byte[] key =
decryptorFactory.makeKeyFromPassPhrase(secret.getEncAlgorithm(), secret.getS2K());
data = new byte[encData.length];
byte[] iv = new byte[secret.getIV().length];
System.arraycopy(secret.getIV(), 0, iv, 0, iv.length);
//
// read in the four numbers
//
int pos = 0;
for (int i = 0; i != 4; i++) {
int encLen = (((encData[pos] << 8) | (encData[pos + 1] & 0xff)) + 7) / 8;
data[pos] = encData[pos];
data[pos + 1] = encData[pos + 1];
byte[] tmp =
decryptorFactory.recoverKeyData(
secret.getEncAlgorithm(), key, iv, encData, pos + 2, encLen);
System.arraycopy(tmp, 0, data, pos + 2, tmp.length);
pos += 2 + encLen;
if (i != 3) {
System.arraycopy(encData, pos - iv.length, iv, 0, iv.length);
}
}
//
// verify and copy checksum
//
data[pos] = encData[pos];
data[pos + 1] = encData[pos + 1];
int cs = ((encData[pos] << 8) & 0xff00) | (encData[pos + 1] & 0xff);
int calcCs = 0;
for (int j = 0; j < data.length - 2; j++) {
calcCs += data[j] & 0xff;
}
calcCs &= 0xffff;
if (calcCs != cs) {
throw new PGPException(
"checksum mismatch: passphrase wrong, expected "
+ Integer.toHexString(cs)
+ " found "
+ Integer.toHexString(calcCs));
}
}
} catch (PGPException e) {
throw e;
} catch (Exception e) {
throw new PGPException("Exception decrypting key", e);
}
} else {
data = encData;
}
return data;
}
/**
* return the algorithm the key is encrypted with.
*
* @return the algorithm used to encrypt the secret key.
*/
public int getKeyEncryptionAlgorithm() {
return secret.getEncAlgorithm();
}