I'm looking for best practices for writing secure session managers.

I'm making a table for the authorization token (UUID OR GUIDv4) with autoincrement, user_id, token, status (enum) then update status onPause() onResume() so when I update a token I get a new autoincrement to store with the token in shared preference. Then on token update I just insert the old token with the user_id in another table for history.

The problems that I'm having:

  1. it's good for a single device but when I want to update like password and update token I will have to end all user sessions and only the one I'm using will be updated.

  2. should I add timestamp and keep the autoincrement inserted for a certain time of token updates or days or should I let it insert new autoincerment?

Is it good practice or there is a better way?

I already read about:

  1. shared preference exploit on root. Is Shared Preferences safe for private datas?

  2. shared preference not secured even if I encrypt data. Android SharedPreference security

  3. ANDROID_ID can be null and can change upon factory reset.

  4. data will be not safe if sensitive data is exploited I came across this but could not find any other articles that approve the method he used SQL injection

I already use a prepared statement:


$db_name = "mysql:host=localhost;dbname=DATABSE;charset=utf8";
$db_username = "root";
$db_password = "";
try {
    $PDO = new PDO($db_name, $db_username, $db_password);
    //echo "connection success";
} catch (PDOException $error) {
    //echo "Error: " . $error->getMessage();
    //echo "connection error";
$user_id = $_POST['user_id'];
$stmt = $PDO->prepare("
                  tableA.name AS name,
                  TABLEB.logo AS logo 
                  FROM tableA
                  LEFT JOIN TABLEB ON TABLEB.id = tableA.id 
                  WHERE tableA.id = :USERID ;
$stmt->bindParam(':USERID', $user_id);

$row = $stmt->fetchAll(PDO::FETCH_ASSOC);

if (!empty($user_id)) {
    $returnApp = new stdClass();
    $returnApp->LOAD_SUCCESSFUL = $row;
    echo json_encode($returnApp);
} else {
    $returnApp = array('LOADPROFILE' => 'LOAD_FAILED');
    echo json_encode($returnApp);

1 Answer 1


I don't see code for some of your items of concern, so I'll focus on reviewing the provided code.

  • Your code should consistently respond with the same general formatted json string so that the receiving code can remain simple and elegant. I think your business logic indicates that an empty array as a response is somehow a failure. A non-empty array will be success.
  • You are not validating the submitted value. If the submission is anything other than a positive integer, then you can safely give the failure response -- even before bothering with a database connection.
  • I recommend eliminating single-use variables in any script unless they provide a valuable benefit.
  • Unconditionally return the empty array or array of associative arrays that is provided by fetchAll().

New code:

if (empty($_POST['user_id']) || !ctype_digit($_POST['user_id'])) {
$pdo = new PDO(
$stmt = $pdo->prepare(
    "SELECT tableA.name AS name,
            TABLEB.logo AS logo 
     FROM tableA
     LEFT JOIN TABLEB ON TABLEB.id = tableA.id 
     WHERE tableA.id = ?"
echo json_encode($stmt->fetchAll(PDO::FETCH_ASSOC));

In terms of security, I am concerned about the fact that anyone can anonymously/trivially fire a bunch of integers at this code and get a direct feed of result set data. Maybe this is why you mentioned UUIDs -- you might think that obscuring the identifier may improve security -- but it won't, it will only potentially slow down a persistent attacker.

  • \$\begingroup\$ I'm sorry i didn't explain it well . i only provided a sample of how i usually get data because shared preference nothing i can do about it except I store a token(UUID) that changes instead of constant user_id . i miss typed the execution and fetch outside if condition and i only do this when i try to insert something and dont want the generate a row with empty variable so i choose random from all available .. thank you so much for updating my php.. if you can update with how often should i update token and if i should let it insert new autoincrement with each update ill be very grateful \$\endgroup\$
    – Taa Lee
    Jan 29, 2022 at 11:25
  • 1
    \$\begingroup\$ Perhaps you should ask a new question and show new, working code to be reviewed. If you want behavior to be changed, we don't do this on CodeReview. \$\endgroup\$ Jan 29, 2022 at 11:35
  • \$\begingroup\$ well that was my two problems and my only question was if doing that is a good practice to secure session manager you already gave an answer that UUID will slow attacker but that wasnt the main problem \$\endgroup\$
    – Taa Lee
    Jan 29, 2022 at 11:44
  • 3
    \$\begingroup\$ Please take the tour and read the Help pages on asking a question. \$\endgroup\$ Jan 29, 2022 at 22:41
  • 3
    \$\begingroup\$ Just to be clear, on CodeReview, we are only permitted to review posted code. I reviewed the only code posted. I am confident that this does not make me a bad reviewer. \$\endgroup\$ Jan 30, 2022 at 5:51

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