Add Telegram Login auth params checking. Closes #167

library/src/main/java/com/pengrad/telegrambot/login/CheckTelegramAuth.java

@@ -0,0 +1,86 @@
+package com.pengrad.telegrambot.login;
+
+import javax.crypto.Mac;
+import javax.crypto.spec.SecretKeySpec;
+import java.math.BigInteger;
+import java.net.URI;
+import java.security.InvalidKeyException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.util.Date;
+import java.util.Iterator;
+import java.util.TreeSet;
+
+/**
+ * Stas Parshin
+ * 18 June 2019
+ */
+public class CheckTelegramAuth {
+
+    private final String botToken, dataCheck, hash;
+    private final long authDate;
+
+    public static CheckTelegramAuth fromUrl(String botToken, String authUrl) {
+        return new CheckTelegramAuth(botToken, URI.create(authUrl).getQuery());
+    }
+
+    private CheckTelegramAuth(String botToken, String authQueryParams) {
+        String hash = null;
+        long authDate = 0;
+        String[] params = authQueryParams.split("&");
+        TreeSet<String> set = new TreeSet<String>();
+        for (String p : params) {
+            if (p.startsWith("hash=")) {
+                hash = p.substring(5);
+            } else {
+                set.add(p);
+            }
+            if (p.startsWith("auth_date=")) {
+                authDate = Long.parseLong(p.substring(10));
+            }
+        }
+        this.hash = hash;
+        this.authDate = authDate;
+        this.dataCheck = join(set, "\n");
+        this.botToken = botToken;
+    }
+
+    public Date authDate() {
+        return new Date(authDate * 1000L);
+    }
+
+    public boolean isFromTelegram() throws Exception {
+        byte[] secret = sha256(botToken.getBytes());
+        String result = hmacSha256(secret, dataCheck);
+        return result.equals(hash);
+    }
+
+    private static byte[] sha256(byte[] string) throws NoSuchAlgorithmException {
+        MessageDigest md = MessageDigest.getInstance("SHA-256");
+        return md.digest(string);
+    }
+
+    private static String hmacSha256(byte[] key, String data) throws NoSuchAlgorithmException, InvalidKeyException {
+        Mac hmacSha256 = Mac.getInstance("HmacSHA256");
+        SecretKeySpec secret_key = new SecretKeySpec(key, "HmacSHA256");
+        hmacSha256.init(secret_key);
+        byte[] result = hmacSha256.doFinal(data.getBytes());
+        return hex(result);
+    }
+
+    private static String hex(byte[] str) {
+        return String.format("%040x", new BigInteger(1, str));
+    }
+
+    private static String join(Iterable<String> elements, CharSequence separator) {
+        StringBuilder builder = new StringBuilder();
+        Iterator<String> it = elements.iterator();
+        if (it.hasNext()) {
+            builder.append(it.next());
+            while (it.hasNext()) {
+                builder.append(separator).append(it.next());
+            }
+        }
+        return builder.toString();
+    }
+}

library/src/test/java/com/pengrad/telegrambot/UpdatesListenerTest.java

@@ -24,7 +24,7 @@
  */
 public class UpdatesListenerTest {
 
-    private static String token() {
+    public static String token() {
         String token;
         try {
             Properties properties = new Properties();

library/src/test/java/com/pengrad/telegrambot/login/CheckTelegramAuthTest.java

@@ -0,0 +1,25 @@
+package com.pengrad.telegrambot.login;
+
+import org.junit.Test;
+
+import java.util.Date;
+
+import static com.pengrad.telegrambot.UpdatesListenerTest.token;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Stas Parshin
+ * 18 June 2019
+ */
+public class CheckTelegramAuthTest {
+
+    @Test
+    public void login() throws Exception {
+        String data = "google.com/?id=51314083&first_name=Stas&last_name=Parshin&username=pengrad&photo_url=https://t.me/i/userpic/320/pengrad.jpg&auth_date=1560837746&hash=b00e1b82fdea0718efc02ee645286fbb0c986526dba9b4bb4d51753960feda04";
+        CheckTelegramAuth checkTelegramAuth = CheckTelegramAuth.fromUrl(token(), data);
+        assertTrue(checkTelegramAuth.isFromTelegram());
+        assertEquals(new Date(1560837746000L), checkTelegramAuth.authDate());
+    }
+
+}