Thanakorn
73c680e844
- OTP attempt limits, constant-time compare, random reference codes - DB-backed rate limits (429) on sign-in, OTP, reset, register, onboarding - one generic sign-in failure message; reset request no longer reveals accounts - no password kept in the session; real status codes on failures
69 lines
2.8 KiB
PHP
69 lines
2.8 KiB
PHP
<?php
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/**
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* login_helpers.php — shared pieces of the 2-step login flow
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* (login_otp.php → login_confirm.php, with request_new_otp.php for resends).
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*
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* Pending-login session state (written by login_otp.php once the password has
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* been verified; the password itself is never kept in the session):
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* login_data['username'] — normalised username/email the user typed
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* login_user_id — resolved user id
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* password_verified_at — Unix time the password was checked
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* otp_attempts — wrong OTP entries for the current code
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* otp_resends — OTP resends for this pending login
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*/
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// One answer for unknown username, wrong password and locked account, so the
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// login form cannot be used to find out which accounts exist.
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const LOGIN_GENERIC_FAILURE = 'Incorrect username or password, or the account is temporarily locked.';
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// A verified password is good for this long before the user must type it again.
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const LOGIN_PENDING_SECONDS = 600;
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// Wrong OTP entries allowed per issued code; the next one ends the pending login.
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const LOGIN_OTP_MAX_ATTEMPTS = 5;
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// OTP resends allowed per pending login.
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const LOGIN_OTP_MAX_RESENDS = 3;
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/**
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* 6-digit TOTP (HMAC-SHA1, 3-minute step) keyed by the user's password hash, so
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* a password change invalidates it. Same algorithm db_auth.php re-derives on
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* every request.
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*/
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function login_generate_otp(string $secret_key, int $otp_time, int $time_step = 180, int $length = 6): string {
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$counter = floor($otp_time / $time_step);
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$data = pack("NN", 0, $counter);
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$hash = hash_hmac('sha1', $data, $secret_key, true);
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$offset = ord(substr($hash, -1)) & 0x0F;
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$value = unpack("N", substr($hash, $offset, 4));
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$otp = ($value[1] & 0x7FFFFFFF) % pow(10, $length);
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return str_pad(strval($otp), $length, '0', STR_PAD_LEFT);
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}
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/**
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* Random 6-letter reference shown on the OTP screen and in the email. It used to
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* be derived from the OTP, which let anyone who saw the reference recover the
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* OTP offline by trying all 10^6 codes; a random value carries no information.
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*/
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function login_random_reference(): string {
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$ref = '';
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for ($i = 0; $i < 6; $i++) {
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$ref .= chr(65 + random_int(0, 25));
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}
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return $ref;
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}
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/** Whether the session holds a pending login whose password check is still fresh. */
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function login_pending_valid(): bool {
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return !empty($_SESSION['login_user_id'])
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&& !empty($_SESSION['password_verified_at'])
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&& (time() - (int)$_SESSION['password_verified_at']) <= LOGIN_PENDING_SECONDS;
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}
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/** Answer with an HTTP status and a JSON message, then stop. */
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function login_fail(int $status, string $message, array $extra = []): void {
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http_response_code($status);
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exit(json_encode(array_merge(['success' => 0, 'message' => $message], $extra)));
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}
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