Error reading file

Newbie & Debugging Questions
#1

I have a file called privatekey.der in the same directory as a static class called KeyReader.

I’m having issues with reading the file. It’s giving me invalid stream header. I was wondering how you can go about reading the file.

This is my code:

package server.encryption;

import java.io.*;
import java.math.BigInteger;
import java.security.*;
import java.security.spec.*;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

public class KeyReader {

	public static PrivateKey getPrivateKey(InputStream in) throws Exception {
//		System.err.println(filename);
//		File f = new File(filename);
		//DataInputStream dis = new DataInputStream(is);
		ObjectInputStream oin = new ObjectInputStream(new BufferedInputStream(in));
		BigInteger m = (BigInteger) oin.readObject();
		BigInteger e = (BigInteger) oin.readObject();
		RSAPrivateKeySpec keySpec = new RSAPrivateKeySpec(m, e);
	    KeyFactory fact = KeyFactory.getInstance("RSA");
	    PrivateKey privateKey = fact.generatePrivate(keySpec);
	    oin.close();
	    return privateKey;
//		PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(keyBytes);
//		KeyFactory kf = KeyFactory.getInstance("RSA");
//		return kf.generatePrivate(spec);
	}
	
	public static byte[] rsaDecrypt(byte[] data) throws Exception {
		System.err.println(KeyReader.class.getResourceAsStream("privatekey.der").toString());
		PrivateKey privateKey = getPrivateKey(KeyReader.class.getResourceAsStream("privatekey.der"));
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, privateKey);
		byte[] cipherData = cipher.doFinal(data);
		return cipherData;
	}
	
	public static byte[] aesDecrypt(byte[]data, byte[]key) throws Exception {
		SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, cipher.getParameters());
		byte[] cipherData = cipher.doFinal(data);
		return cipherData;
	}
	
}
#2

Nevermind me, didn’t see that you mentioned the error

~Shazer2 :slight_smile:

#3

If it didn’t find the file, getResourceAsStream(…) would return null, which would cause the constructor for ObjectInputStream to throw an IOException.

This error could only happen if you didn’t previously write to the file using a ObjectOutputStream.

#4

Maybe error caused by opening stream twice:

public static byte[] rsaDecrypt(byte[] data) throws Exception {
		System.err.println(KeyReader.class.getResourceAsStream("privatekey.der").toString());
		PrivateKey privateKey = getPrivateKey(KeyReader.class.getResourceAsStream("privatekey.der"));
		...
	}
#5

Oh come on! Can’t you guys read?[quote]It’s giving me invalid stream header.
[/quote]
This means that it has opened the stream without any problem. It’s just that the data in the ‘header’ (first N bytes) is not what the ObjectInputStream was expecting.

I mean, reading a DER file and expecting it to return BigIntegers upon calling ObjectInputStream.readObject() is silly.

#6

Which is why I pointed out he didn’t write to the file previously with an ObjectOutputStream since the first 4 bytes of the stream have to be 0xAECD (I do believe that’s correct).

I don’t know what a DER file is :slight_smile: