InvalidKeySpecExeption when loadding the RSA private key from file

Question

I'm trying to load a private key from file in java. This key is generated by ssh-agent. I'm actually using the code below:

     public PrivateKey getPrivateKeyFromFile() {
    try {
        //String privateKey = readFileAsString(System.getProperty("user.dir")+"/clefs/"+privateKeyName);
        //byte[] encodePrivateKey = privateKey.getBytes();
        File filePrivateKey = new File(System.getProperty("user.dir")+"/clefs/"+privateKeyName);
        FileInputStream fis = new FileInputStream(System.getProperty("user.dir")+"/clefs/"+privateKeyName);
        byte[] encodePrivateKey = new byte[(int) filePrivateKey.length()];
        fis.read(encodePrivateKey);
        fis.close();

        java.security.KeyFactory keyFactory = java.security.KeyFactory.getInstance("RSA");
        PKCS8EncodedKeySpec privatekeySpec = new PKCS8EncodedKeySpec(encodePrivateKey);
        PrivateKey prikey = (PrivateKey) keyFactory.generatePrivate(privatekeySpec);
        return prikey;

    } catch (NoSuchAlgorithmException ne) {
        ne.printStackTrace();
    } catch (InvalidKeySpecException is) {
        is.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }

    return null;

}

But it generated this exception:

 java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: invalid key format
at sun.security.rsa.RSAKeyFactory.engineGeneratePrivate(RSAKeyFactory.java:217)
at java.security.KeyFactory.generatePrivate(KeyFactory.java:372)
at com.nguyenkim.cea.signature.SignChallenge.getPrivateKeyFromFile(SignChallenge.java:53)
at com.nguyenkim.cea.signature.SignChallenge.main(SignChallenge.java:128)
 Caused by: java.security.InvalidKeyException: invalid key format
at sun.security.pkcs.PKCS8Key.decode(PKCS8Key.java:341)
at sun.security.pkcs.PKCS8Key.decode(PKCS8Key.java:367)
at sun.security.rsa.RSAPrivateCrtKeyImpl.<init>(RSAPrivateCrtKeyImpl.java:91)
at sun.security.rsa.RSAPrivateCrtKeyImpl.newKey(RSAPrivateCrtKeyImpl.java:75)
at sun.security.rsa.RSAKeyFactory.generatePrivate(RSAKeyFactory.java:316)
at sun.security.rsa.RSAKeyFactory.engineGeneratePrivate(RSAKeyFactory.java:213)
... 3 more

Here is the private key:

   -----BEGIN RSA PRIVATE KEY-----
  MIIEowIBAAKCAQEAszReSzBumVb9GR/f3ClgykWE4UsONan1Ywk/H4+Wbi4HpcwB
  8Lm9B+zJ94WdRtD8iQYmbUZFoHwFqTjRPtmQfFXcmxfuI7v64bg0csIw8hz1Af2r
  xo7HBUoVcrTG5k3YrIkjeni/vD9uK6OZ1/lb+/TIvoEp9za577GJxv1omQ6GX7kv
  baMe2GkfpJmrXnA706OEdyi3Ibdcng/V4lbJ9cm+TIBU2jLBqwEukwpL5VNghuQi
  3YfpGhnPDBEnh4h5euFs4DGs4FnCgb+00yCuEgJSPvO5HsTnGbwTtEUnkxjtg8vD
  plD7WenPsyiZqib/rLkNcpfEHKVC6G3QjEuO8QIDAQABAoIBAGliRoFY/fFW4og/
  .............................
  -----END RSA PRIVATE KEY-----

Any suggestions? Thanks.

Answer 1

Are you sure its RSA ? also are you sure that the key is in the right format?

If the answer is yes to both questions you can try using bouncycastle lib

EDIT : Try removing these rows from the key:

-----BEGIN RSA PRIVATE KEY-----
.............................
-----END RSA PRIVATE KEY-----

UPDATE : make sure that you private key is in PKCS8 format if not you need to convert it like here

Answer 2

Intstead of removing header and footers from private key file you can use BouncyCastle's Pemreader.

 private PrivateKey getPrivateKeyFromFile(String keyFile) throws IOException, NoSuchAlgorithmException, InvalidKeySpecException {
    final InputStream inputStream = getClass().getClassLoader().getResourceAsStream(keyFile);
    String privateKeySTr = IOUtils.toString(inputStream, String.valueOf(StandardCharsets.UTF_8));

    PemObject pem = new PemReader(new StringReader(privateKeySTr)).readPemObject();
    byte[] der = pem.getContent();
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PKCS8EncodedKeySpec ks = new PKCS8EncodedKeySpec(der);
    RSAPrivateKey privKey = (RSAPrivateKey) keyFactory.generatePrivate(ks);
    return privKey;
}