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/*
* mygram-droid: Android TV client for Foldergram.
* Copyright (C) 2026 Danilo M. <danix@danix.xyz>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published
* by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*/
package mygram.droid;
import android.content.Context;
import android.content.SharedPreferences;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
/** Settings stored on the device. */
final class Prefs {
private static SharedPreferences prefs;
private Prefs() {
}
static void init(Context c) {
prefs = c.getSharedPreferences("mygram", Context.MODE_PRIVATE);
}
/** Base URL like "http://192.0.2.10:4141", or null before setup. */
static String server() {
return prefs.getString("server", null);
}
/** Viewer password; empty for a public instance. */
static String password() {
return prefs.getString("password", "");
}
static int photoSeconds() {
return prefs.getInt("photo", 8);
}
static int backgroundSeconds() {
return prefs.getInt("background", 15);
}
static void setServer(String base, String password) {
prefs.edit().putString("server", base).putString("password", password).apply();
}
static void setPassword(String password) {
prefs.edit().putString("password", password).apply();
}
static void setTimes(int photo, int background) {
prefs.edit().putInt("photo", photo).putInt("background", background).apply();
}
static boolean validPin(String pin) {
return pin.matches("[0-9]{4,8}");
}
static boolean hasPin() {
return !prefs.getString("pin", "").isEmpty();
}
/** Stores "salt:sha256(salt + pin)", never the PIN; null removes it. */
static void setPin(String pin) {
if (pin == null) {
prefs.edit().remove("pin").apply();
return;
}
byte[] b = new byte[16];
new SecureRandom().nextBytes(b);
String salt = hex(b);
prefs.edit().putString("pin", salt + ":" + hash(salt, pin)).apply();
}
static boolean checkPin(String pin) {
String[] stored = prefs.getString("pin", "").split(":");
return stored.length == 2 && MessageDigest.isEqual(stored[1].getBytes(StandardCharsets.UTF_8),
hash(stored[0], pin).getBytes(StandardCharsets.UTF_8));
}
// ponytail: one SHA-256 round; a 4-8 digit PIN is a privacy screen, not a secret against someone with the device storage.
static String hash(String salt, String pin) {
try {
return hex(MessageDigest.getInstance("SHA-256").digest((salt + pin).getBytes(StandardCharsets.UTF_8)));
} catch (NoSuchAlgorithmException e) {
throw new IllegalStateException(e); // every Java platform ships SHA-256
}
}
private static String hex(byte[] b) {
StringBuilder s = new StringBuilder();
for (byte x : b)
s.append(String.format("%02x", x));
return s.toString();
}
}
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