// Copyright 2010 Google Inc. All Rights Reserved.
package com.example.dungeons;
import com.example.dungeons.Consts.PurchaseState;
import com.example.dungeons.util.Base64;
import com.example.dungeons.util.Base64DecoderException;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.text.TextUtils;
import android.util.Log;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.SignatureException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.X509EncodedKeySpec;
import java.util.ArrayList;
import java.util.HashSet;
/**
* Security-related methods. For a secure implementation, all of this code
* should be implemented on a server that communicates with the
* application on the device. For the sake of simplicity and clarity of this
* example, this code is included here and is executed on the device. If you
* must verify the purchases on the phone, you should obfuscate this code to
* make it harder for an attacker to replace the code with stubs that treat all
* purchases as verified.
*/
public class Security {
private static final String TAG = "Security";
private static final String KEY_FACTORY_ALGORITHM = "RSA";
private static final String SIGNATURE_ALGORITHM = "SHA1withRSA";
private static final SecureRandom RANDOM = new SecureRandom();
/**
* This keeps track of the nonces that we generated and sent to the
* server. We need to keep track of these until we get back the purchase
* state and send a confirmation message back to Android Market. If we are
* killed and lose this list of nonces, it is not fatal. Android Market will
* send us a new "notify" message and we will re-generate a new nonce.
* This has to be "static" so that the {@link BillingReceiver} can
* check if a nonce exists.
*/
private static HashSet<Long> sKnownNonces = new HashSet<Long>();
/**
* A class to hold the verified purchase information.
*/
public static class VerifiedPurchase {
public PurchaseState purchaseState;
public String notificationId;
public String productId;
public String orderId;
public long purchaseTime;
public String developerPayload;
public VerifiedPurchase(PurchaseState purchaseState, String notificationId,
String productId, String orderId, long purchaseTime, String developerPayload) {
this.purchaseState = purchaseState;
this.notificationId = notificationId;
this.productId = productId;
this.orderId = orderId;
this.purchaseTime = purchaseTime;
this.developerPayload = developerPayload;
}
}
/** Generates a nonce (a random number used once). */
public static long generateNonce() {
long nonce = RANDOM.nextLong();
sKnownNonces.add(nonce);
return nonce;
}
public static void removeNonce(long nonce) {
sKnownNonces.remove(nonce);
}
public static boolean isNonceKnown(long nonce) {
return sKnownNonces.contains(nonce);
}
/**
* Verifies that the data was signed with the given signature, and returns
* the list of verified purchases. The data is in JSON format and contains
* a nonce (number used once) that we generated and that was signed
* (as part of the whole data string) with a private key. The data also
* contains the {@link PurchaseState} and product ID of the purchase.
* In the general case, there can be an array of purchase transactions
* because there may be delays in processing the purchase on the backend
* and then several purchases can be batched together.
* @param signedData the signed JSON string (signed, not encrypted)
* @param signature the signature for the data, signed with the private key
*/
public static ArrayList<VerifiedPurchase> verifyPurchase(String signedData, String signature) {
if (signedData == null) {
Log.e(TAG, "data is null");
return null;
}
if (Consts.DEBUG) {
Log.i(TAG, "signedData: " + signedData);
}
boolean verified = false;
if (!TextUtils.isEmpty(signature)) {
// Some random RSA key, not actually suitable for the Google Play store.
// Replace this with the public key from your Google Play profile.
// We'll let DexGuard encrypt it.
String base64EncodedPublicKey = "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC+T3PmaVTzJZYt75vi4+EQKDp6wgtFTzAwTRENX0Tw0EIT+55zNfMaI4LfgSjF6jCl7zxl7hH7u8NG9/MmrdNMsR5w9Tob9qsH0kPoK0TXh7wFY00umEKEj+v+7gxsLqzyAS1OPka7KZXTFU8QWcbcTf2FOmk2v/tn/p212gwlcQIDAQAB";
PublicKey key = Security.generatePublicKey(base64EncodedPublicKey);
verified = Security.verify(key, signedData, signature);
if (!verified) {
Log.w(TAG, "signature does not match data.");
return null;
}
}
JSONObject jObject;
JSONArray jTransactionsArray = null;
int numTransactions = 0;
long nonce = 0L;
try {
jObject = new JSONObject(signedData);
// The nonce might be null if the user backed out of the buy page.
nonce = jObject.optLong("nonce");
jTransactionsArray = jObject.optJSONArray("orders");
if (jTransactionsArray != null) {
numTransactions = jTransactionsArray.length();
}
} catch (JSONException e) {
return null;
}
if (!Security.isNonceKnown(nonce)) {
Log.w(TAG, "Nonce not found: " + nonce);
return null;
}
ArrayList<VerifiedPurchase> purchases = new ArrayList<VerifiedPurchase>();
try {
for (int i = 0; i < numTransactions; i++) {
JSONObject jElement = jTransactionsArray.getJSONObject(i);
int response = jElement.getInt("purchaseState");
PurchaseState purchaseState = PurchaseState.valueOf(response);
String productId = jElement.getString("productId");
String packageName = jElement.getString("packageName");
long purchaseTime = jElement.getLong("purchaseTime");
String orderId = jElement.optString("orderId", "");
String notifyId = null;
if (jElement.has("notificationId")) {
notifyId = jElement.getString("notificationId");
}
String developerPayload = jElement.optString("developerPayload", null);
// If the purchase state is PURCHASED, then we require a
// verified nonce.
if (purchaseState == PurchaseState.PURCHASED && !verified) {
continue;
}
purchases.add(new VerifiedPurchase(purchaseState, notifyId, productId,
orderId, purchaseTime, developerPayload));
}
} catch (JSONException e) {
Log.e(TAG, "JSON exception: ", e);
return null;
}
removeNonce(nonce);
return purchases;
}
/**
* Generates a PublicKey instance from a string containing the
* Base64-encoded public key.
*
* @param encodedPublicKey Base64-encoded public key
* @throws IllegalArgumentException if encodedPublicKey is invalid
*/
public static PublicKey generatePublicKey(String encodedPublicKey) {
try {
byte[] decodedKey = Base64.decode(encodedPublicKey);
KeyFactory keyFactory = KeyFactory.getInstance(KEY_FACTORY_ALGORITHM);
return keyFactory.generatePublic(new X509EncodedKeySpec(decodedKey));
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException(e);
} catch (InvalidKeySpecException e) {
Log.e(TAG, "Invalid key specification.");
throw new IllegalArgumentException(e);
} catch (Base64DecoderException e) {
Log.e(TAG, "Base64 decoding failed.");
throw new IllegalArgumentException(e);
}
}
/**
* Verifies that the signature from the server matches the computed
* signature on the data. Returns true if the data is correctly signed.
*
* @param publicKey public key associated with the developer account
* @param signedData signed data from server
* @param signature server signature
* @return true if the data and signature match
*/
public static boolean verify(PublicKey publicKey, String signedData, String signature) {
if (Consts.DEBUG) {
Log.i(TAG, "signature: " + signature);
}
Signature sig;
try {
sig = Signature.getInstance(SIGNATURE_ALGORITHM);
sig.initVerify(publicKey);
sig.update(signedData.getBytes());
if (!sig.verify(Base64.decode(signature))) {
Log.e(TAG, "Signature verification failed.");
return false;
}
return true;
} catch (NoSuchAlgorithmException e) {
Log.e(TAG, "NoSuchAlgorithmException.");
} catch (InvalidKeyException e) {
Log.e(TAG, "Invalid key specification.");
} catch (SignatureException e) {
Log.e(TAG, "Signature exception.");
} catch (Base64DecoderException e) {
Log.e(TAG, "Base64 decoding failed.");
}
return false;
}
}