I am finally starting to reverse engineering this client and it has been quite fun so far 🙂
As mentioned in the other thread b.o class handles the encryption/decryption and if you apply the string decryption method you get the following:
Class: b.o
z[0] = CB13370FDC5197B54FA4D269D5A80ACD
z[1] = AES/CBC/PKCS5Padding
z[2] = AES
z[3] = 747DA8F0024ABFE26AA49B6C3285CC47
z[4] = native
z[5] = file
z[6] = lib
z[7] = .classAs you can see it is using AES encryption and AES/CBC/PKCS5Padding for the cipher stream. The values in z[0] and z[3] is really what interests me so i started working on them and i got them figured out:
z[3] = IvParameterSpec after DatatypeConverter.parseHexBinary (so z[3] is the IV for the aes decryption and is encoded with HexBinary as well.)
z[0] = SecretKeySpec this is the key for AES after DatatypeConverter.parseHexBinary (So z[0] is the actual key for the aes decryption it is just encoded with HexBinary sequence)
Basically to reproduce the information:
Cipher.getInstance("AES/CBC/PKCS5Padding").init(Cipher.DECRYPT_MODE, new SecretKeySpec(DatatypeConverter.parseHexBinary("CB13370FDC5197B54FA4D269D5A80ACD"), "AES"), new IvParameterSpec(DatatypeConverter.parseHexBinary("747DA8F0024ABFE26AA49B6C3285CC47")));That is the Cipher stream you will use to decrypt the information.
Upon further inspection of the code i have learned that they are using Pack200 [java.util.jar packer] to unpack the jar file:
Pack200.newUnpacker().unpack(new GZipInputStream(data), JarOutputStream);private static byte[] b(String s, byte abyte0[])
{
byte abyte1[];
byte abyte2[];
s = new d(s.getBytes());
String s1;
abyte1 = DatatypeConverter.parseHexBinary(s1 = z[3]);
s.c(abyte1);
abyte2 = DatatypeConverter.parseHexBinary(s1 = z[0]);
s.c(abyte2);
(s = Cipher.getInstance(z[1])).init(2, new SecretKeySpec(abyte2, z[2]), new IvParameterSpec(abyte1));
return s.doFinal(abyte0);
JVM INSTR dup ;
s;
printStackTrace();
return null;
}This is the method in the b.o class that handles the decryption of information and where the information above comes from. Parameter abyte0[] is the encrypted information. abyte1 is the unencoded IV, abyte2 is the unencoded SecretKey.
I will keep working on this and see what else i can do. I will start working on dumping the actual jar from memory and hopefully i can find the method that will load the cache 🙂.