Created
February 18, 2019 09:41
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Android Signature generator for SMS code verification
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package com.google.samples.smartlock.sms_verify; | |
import android.content.Context; | |
import android.content.ContextWrapper; | |
import android.content.pm.PackageManager; | |
import android.content.pm.Signature; | |
import android.util.Base64; | |
import android.util.Log; | |
import java.nio.charset.StandardCharsets; | |
import java.security.MessageDigest; | |
import java.security.NoSuchAlgorithmException; | |
import java.util.ArrayList; | |
import java.util.Arrays; | |
/** | |
* Notes: | |
* Class is From: https://github.com/googlesamples/android-credentials/blob/master/sms-verification/android/app/src/main/java/com/google/samples/smartlock/sms_verify/AppSignatureHelper.java | |
* Guide: https://developers.google.com/identity/sms-retriever/verify | |
* | |
* | |
* This is a helper class to generate your message hash to be included in your SMS message. | |
* | |
* Without the correct hash, your app won't recieve the message callback. This only needs to be | |
* generated once per app and stored. Then you can remove this helper class from your code. | |
*/ | |
public class AppSignatureHelper extends ContextWrapper { | |
public static final String TAG = AppSignatureHelper.class.getSimpleName(); | |
private static final String HASH_TYPE = "SHA-256"; | |
public static final int NUM_HASHED_BYTES = 9; | |
public static final int NUM_BASE64_CHAR = 11; | |
public AppSignatureHelper(Context context) { | |
super(context); | |
} | |
/** | |
* Get all the app signatures for the current package | |
* @return | |
*/ | |
public ArrayList<String> getAppSignatures() { | |
ArrayList<String> appCodes = new ArrayList<>(); | |
try { | |
// Get all package signatures for the current package | |
String packageName = getPackageName(); | |
PackageManager packageManager = getPackageManager(); | |
Signature[] signatures = packageManager.getPackageInfo(packageName, | |
PackageManager.GET_SIGNATURES).signatures; | |
// For each signature create a compatible hash | |
for (Signature signature : signatures) { | |
String hash = hash(packageName, signature.toCharsString()); | |
if (hash != null) { | |
appCodes.add(String.format("%s", hash)); | |
} | |
} | |
} catch (PackageManager.NameNotFoundException e) { | |
Log.e(TAG, "Unable to find package to obtain hash.", e); | |
} | |
return appCodes; | |
} | |
private static String hash(String packageName, String signature) { | |
String appInfo = packageName + " " + signature; | |
try { | |
MessageDigest messageDigest = MessageDigest.getInstance(HASH_TYPE); | |
messageDigest.update(appInfo.getBytes(StandardCharsets.UTF_8)); | |
byte[] hashSignature = messageDigest.digest(); | |
// truncated into NUM_HASHED_BYTES | |
hashSignature = Arrays.copyOfRange(hashSignature, 0, NUM_HASHED_BYTES); | |
// encode into Base64 | |
String base64Hash = Base64.encodeToString(hashSignature, Base64.NO_PADDING | Base64.NO_WRAP); | |
base64Hash = base64Hash.substring(0, NUM_BASE64_CHAR); | |
Log.d(TAG, String.format("pkg: %s -- hash: %s", packageName, base64Hash)); | |
return base64Hash; | |
} catch (NoSuchAlgorithmException e) { | |
Log.e(TAG, "hash:NoSuchAlgorithm", e); | |
} | |
return null; | |
} | |
} |
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