Ergänzend zu den Änderungen von @Wufoo verwendet die folgende Version InputStreams anstelle von Dateien, um die Arbeit mit einer Vielzahl von Dateien zu erleichtern. Außerdem werden IV und Salt am Anfang der Datei gespeichert, so dass nur das Kennwort nachverfolgt werden muss. Da IV und Salt nicht geheim sein müssen, macht dies das Leben ein wenig einfacher.
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.AlgorithmParameters;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.InvalidParameterSpecException;
import java.security.spec.KeySpec;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.SecretKeySpec;
public class AES {
public final static int SALT_LEN = 8;
static final String HEXES = "0123456789ABCDEF";
String mPassword = null;
byte[] mInitVec = null;
byte[] mSalt = new byte[SALT_LEN];
Cipher mEcipher = null;
Cipher mDecipher = null;
private final int KEYLEN_BITS = 128; // see notes below where this is used.
private final int ITERATIONS = 65536;
private final int MAX_FILE_BUF = 1024;
/**
* create an object with just the passphrase from the user. Don't do anything else yet
* @param password
*/
public AES(String password) {
mPassword = password;
}
public static String byteToHex(byte[] raw) {
if (raw == null) {
return null;
}
final StringBuilder hex = new StringBuilder(2 * raw.length);
for (final byte b : raw) {
hex.append(HEXES.charAt((b & 0xF0) >> 4)).append(HEXES.charAt((b & 0x0F)));
}
return hex.toString();
}
public static byte[] hexToByte(String hexString) {
int len = hexString.length();
byte[] ba = new byte[len / 2];
for (int i = 0; i < len; i += 2) {
ba[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4)
+ Character.digit(hexString.charAt(i + 1), 16));
}
return ba;
}
/**
* debug/print messages
* @param msg
*/
private void Db(String msg) {
System.out.println("** Crypt ** " + msg);
}
/**
* This is where we write out the actual encrypted data to disk using the Cipher created in setupEncrypt().
* Pass two file objects representing the actual input (cleartext) and output file to be encrypted.
*
* there may be a way to write a cleartext header to the encrypted file containing the salt, but I ran
* into uncertain problems with that.
*
* @param input - the cleartext file to be encrypted
* @param output - the encrypted data file
* @throws IOException
* @throws IllegalBlockSizeException
* @throws BadPaddingException
*/
public void WriteEncryptedFile(InputStream inputStream, OutputStream outputStream)
throws IOException, IllegalBlockSizeException, BadPaddingException {
try {
long totalread = 0;
int nread = 0;
byte[] inbuf = new byte[MAX_FILE_BUF];
SecretKeyFactory factory = null;
SecretKey tmp = null;
// crate secureRandom salt and store as member var for later use
mSalt = new byte[SALT_LEN];
SecureRandom rnd = new SecureRandom();
rnd.nextBytes(mSalt);
Db("generated salt :" + byteToHex(mSalt));
factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
/*
* Derive the key, given password and salt.
*
* in order to do 256 bit crypto, you have to muck with the files for Java's "unlimted security"
* The end user must also install them (not compiled in) so beware.
* see here: http://www.javamex.com/tutorials/cryptography/unrestricted_policy_files.shtml
*/
KeySpec spec = new PBEKeySpec(mPassword.toCharArray(), mSalt, ITERATIONS, KEYLEN_BITS);
tmp = factory.generateSecret(spec);
SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");
/*
* Create the Encryption cipher object and store as a member variable
*/
mEcipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
mEcipher.init(Cipher.ENCRYPT_MODE, secret);
AlgorithmParameters params = mEcipher.getParameters();
// get the initialization vectory and store as member var
mInitVec = params.getParameterSpec(IvParameterSpec.class).getIV();
Db("mInitVec is :" + byteToHex(mInitVec));
outputStream.write(mSalt);
outputStream.write(mInitVec);
while ((nread = inputStream.read(inbuf)) > 0) {
Db("read " + nread + " bytes");
totalread += nread;
// create a buffer to write with the exact number of bytes read. Otherwise a short read fills inbuf with 0x0
// and results in full blocks of MAX_FILE_BUF being written.
byte[] trimbuf = new byte[nread];
for (int i = 0; i < nread; i++) {
trimbuf[i] = inbuf[i];
}
// encrypt the buffer using the cipher obtained previosly
byte[] tmpBuf = mEcipher.update(trimbuf);
// I don't think this should happen, but just in case..
if (tmpBuf != null) {
outputStream.write(tmpBuf);
}
}
// finalize the encryption since we've done it in blocks of MAX_FILE_BUF
byte[] finalbuf = mEcipher.doFinal();
if (finalbuf != null) {
outputStream.write(finalbuf);
}
outputStream.flush();
inputStream.close();
outputStream.close();
outputStream.close();
Db("wrote " + totalread + " encrypted bytes");
} catch (InvalidKeyException ex) {
Logger.getLogger(AES.class.getName()).log(Level.SEVERE, null, ex);
} catch (InvalidParameterSpecException ex) {
Logger.getLogger(AES.class.getName()).log(Level.SEVERE, null, ex);
} catch (NoSuchAlgorithmException ex) {
Logger.getLogger(AES.class.getName()).log(Level.SEVERE, null, ex);
} catch (NoSuchPaddingException ex) {
Logger.getLogger(AES.class.getName()).log(Level.SEVERE, null, ex);
} catch (InvalidKeySpecException ex) {
Logger.getLogger(AES.class.getName()).log(Level.SEVERE, null, ex);
}
}
/**
* Read from the encrypted file (input) and turn the cipher back into cleartext. Write the cleartext buffer back out
* to disk as (output) File.
*
* I left CipherInputStream in here as a test to see if I could mix it with the update() and final() methods of encrypting
* and still have a correctly decrypted file in the end. Seems to work so left it in.
*
* @param input - File object representing encrypted data on disk
* @param output - File object of cleartext data to write out after decrypting
* @throws IllegalBlockSizeException
* @throws BadPaddingException
* @throws IOException
*/
public void ReadEncryptedFile(InputStream inputStream, OutputStream outputStream)
throws IllegalBlockSizeException, BadPaddingException, IOException {
try {
CipherInputStream cin;
long totalread = 0;
int nread = 0;
byte[] inbuf = new byte[MAX_FILE_BUF];
// Read the Salt
inputStream.read(this.mSalt);
Db("generated salt :" + byteToHex(mSalt));
SecretKeyFactory factory = null;
SecretKey tmp = null;
SecretKey secret = null;
factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
KeySpec spec = new PBEKeySpec(mPassword.toCharArray(), mSalt, ITERATIONS, KEYLEN_BITS);
tmp = factory.generateSecret(spec);
secret = new SecretKeySpec(tmp.getEncoded(), "AES");
/* Decrypt the message, given derived key and initialization vector. */
mDecipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
// Set the appropriate size for mInitVec by Generating a New One
AlgorithmParameters params = mDecipher.getParameters();
mInitVec = params.getParameterSpec(IvParameterSpec.class).getIV();
// Read the old IV from the file to mInitVec now that size is set.
inputStream.read(this.mInitVec);
Db("mInitVec is :" + byteToHex(mInitVec));
mDecipher.init(Cipher.DECRYPT_MODE, secret, new IvParameterSpec(mInitVec));
// creating a decoding stream from the FileInputStream above using the cipher created from setupDecrypt()
cin = new CipherInputStream(inputStream, mDecipher);
while ((nread = cin.read(inbuf)) > 0) {
Db("read " + nread + " bytes");
totalread += nread;
// create a buffer to write with the exact number of bytes read. Otherwise a short read fills inbuf with 0x0
byte[] trimbuf = new byte[nread];
for (int i = 0; i < nread; i++) {
trimbuf[i] = inbuf[i];
}
// write out the size-adjusted buffer
outputStream.write(trimbuf);
}
outputStream.flush();
cin.close();
inputStream.close();
outputStream.close();
Db("wrote " + totalread + " encrypted bytes");
} catch (Exception ex) {
Logger.getLogger(AES.class.getName()).log(Level.SEVERE, null, ex);
}
}
/**
* adding main() for usage demonstration. With member vars, some of the locals would not be needed
*/
public static void main(String[] args) {
// create the input.txt file in the current directory before continuing
File input = new File("input.txt");
File eoutput = new File("encrypted.aes");
File doutput = new File("decrypted.txt");
String iv = null;
String salt = null;
AES en = new AES("mypassword");
/*
* write out encrypted file
*/
try {
en.WriteEncryptedFile(new FileInputStream(input), new FileOutputStream(eoutput));
System.out.printf("File encrypted to " + eoutput.getName() + "\niv:" + iv + "\nsalt:" + salt + "\n\n");
} catch (IllegalBlockSizeException | BadPaddingException | IOException e) {
e.printStackTrace();
}
/*
* decrypt file
*/
AES dc = new AES("mypassword");
/*
* write out decrypted file
*/
try {
dc.ReadEncryptedFile(new FileInputStream(eoutput), new FileOutputStream(doutput));
System.out.println("decryption finished to " + doutput.getName());
} catch (IllegalBlockSizeException | BadPaddingException | IOException e) {
e.printStackTrace();
}
}
}
