michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.sync.crypto;
michael@0: 
michael@0: import java.io.UnsupportedEncodingException;
michael@0: import java.security.InvalidKeyException;
michael@0: import java.security.NoSuchAlgorithmException;
michael@0: import java.util.Arrays;
michael@0: 
michael@0: import javax.crypto.KeyGenerator;
michael@0: import javax.crypto.Mac;
michael@0: 
michael@0: import org.mozilla.apache.commons.codec.binary.Base64;
michael@0: import org.mozilla.gecko.sync.Utils;
michael@0: 
michael@0: public class KeyBundle {
michael@0:     private static final String KEY_ALGORITHM_SPEC = "AES";
michael@0:     private static final int    KEY_SIZE           = 256;
michael@0: 
michael@0:     private byte[] encryptionKey;
michael@0:     private byte[] hmacKey;
michael@0: 
michael@0:     // These are the same for every sync key bundle.
michael@0:     private static final byte[] EMPTY_BYTES      = {};
michael@0:     private static final byte[] ENCR_INPUT_BYTES = {1};
michael@0:     private static final byte[] HMAC_INPUT_BYTES = {2};
michael@0: 
michael@0:     /*
michael@0:      * Mozilla's use of HKDF for getting keys from the Sync Key string.
michael@0:      *
michael@0:      * We do exactly 2 HKDF iterations and make the first iteration the
michael@0:      * encryption key and the second iteration the HMAC key.
michael@0:      *
michael@0:      */
michael@0:     public KeyBundle(String username, String base32SyncKey) throws CryptoException {
michael@0:       if (base32SyncKey == null) {
michael@0:         throw new IllegalArgumentException("No sync key provided.");
michael@0:       }
michael@0:       if (username == null || username.equals("")) {
michael@0:         throw new IllegalArgumentException("No username provided.");
michael@0:       }
michael@0:       // Hash appropriately.
michael@0:       try {
michael@0:         username = Utils.usernameFromAccount(username);
michael@0:       } catch (NoSuchAlgorithmException e) {
michael@0:         throw new IllegalArgumentException("Invalid username.");
michael@0:       } catch (UnsupportedEncodingException e) {
michael@0:         throw new IllegalArgumentException("Invalid username.");
michael@0:       }
michael@0: 
michael@0:       byte[] syncKey = Utils.decodeFriendlyBase32(base32SyncKey);
michael@0:       byte[] user    = username.getBytes();
michael@0: 
michael@0:       Mac hmacHasher;
michael@0:       try {
michael@0:         hmacHasher = HKDF.makeHMACHasher(syncKey);
michael@0:       } catch (NoSuchAlgorithmException e) {
michael@0:         throw new CryptoException(e);
michael@0:       } catch (InvalidKeyException e) {
michael@0:         throw new CryptoException(e);
michael@0:       }
michael@0:       assert(hmacHasher != null); // If makeHMACHasher doesn't throw, then hmacHasher is non-null.
michael@0: 
michael@0:       byte[] encrBytes = Utils.concatAll(EMPTY_BYTES, HKDF.HMAC_INPUT, user, ENCR_INPUT_BYTES);
michael@0:       byte[] encrKey   = HKDF.digestBytes(encrBytes, hmacHasher);
michael@0:       byte[] hmacBytes = Utils.concatAll(encrKey, HKDF.HMAC_INPUT, user, HMAC_INPUT_BYTES);
michael@0: 
michael@0:       this.hmacKey       = HKDF.digestBytes(hmacBytes, hmacHasher);
michael@0:       this.encryptionKey = encrKey;
michael@0:     }
michael@0: 
michael@0:     public KeyBundle(byte[] encryptionKey, byte[] hmacKey) {
michael@0:        this.setEncryptionKey(encryptionKey);
michael@0:        this.setHMACKey(hmacKey);
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Make a KeyBundle with the specified base64-encoded keys.
michael@0:      *
michael@0:      * @return A KeyBundle with the specified keys.
michael@0:      */
michael@0:     public static KeyBundle fromBase64EncodedKeys(String base64EncryptionKey, String base64HmacKey) throws UnsupportedEncodingException {
michael@0:       return new KeyBundle(Base64.decodeBase64(base64EncryptionKey.getBytes("UTF-8")),
michael@0:                            Base64.decodeBase64(base64HmacKey.getBytes("UTF-8")));
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Make a KeyBundle with two random 256 bit keys (encryption and HMAC).
michael@0:      *
michael@0:      * @return A KeyBundle with random keys.
michael@0:      */
michael@0:     public static KeyBundle withRandomKeys() throws CryptoException {
michael@0:       KeyGenerator keygen;
michael@0:       try {
michael@0:         keygen = KeyGenerator.getInstance(KEY_ALGORITHM_SPEC);
michael@0:       } catch (NoSuchAlgorithmException e) {
michael@0:         throw new CryptoException(e);
michael@0:       }
michael@0: 
michael@0:       keygen.init(KEY_SIZE);
michael@0:       byte[] encryptionKey = keygen.generateKey().getEncoded();
michael@0:       byte[] hmacKey = keygen.generateKey().getEncoded();
michael@0: 
michael@0:       return new KeyBundle(encryptionKey, hmacKey);
michael@0:     }
michael@0: 
michael@0:     public byte[] getEncryptionKey() {
michael@0:         return encryptionKey;
michael@0:     }
michael@0: 
michael@0:     public void setEncryptionKey(byte[] encryptionKey) {
michael@0:         this.encryptionKey = encryptionKey;
michael@0:     }
michael@0: 
michael@0:     public byte[] getHMACKey() {
michael@0:         return hmacKey;
michael@0:     }
michael@0: 
michael@0:     public void setHMACKey(byte[] hmacKey) {
michael@0:         this.hmacKey = hmacKey;
michael@0:     }
michael@0: 
michael@0:     @Override
michael@0:     public boolean equals(Object o) {
michael@0:       if (!(o instanceof KeyBundle)) {
michael@0:         return false;
michael@0:       }
michael@0:       KeyBundle other = (KeyBundle) o;
michael@0:       return Arrays.equals(other.encryptionKey, this.encryptionKey) &&
michael@0:              Arrays.equals(other.hmacKey, this.hmacKey);
michael@0:     }
michael@0: 
michael@0:     @Override
michael@0:     public int hashCode() {
michael@0:       throw new UnsupportedOperationException("No hashCode for KeyBundle.");
michael@0:     }
michael@0: }