124 lines
4.1 KiB
PHP
124 lines
4.1 KiB
PHP
<?php
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declare(strict_types=1);
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/*
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* Two-factor authentication for admins: TOTP (RFC 6238, SHA-1, 6 digits, 30 s),
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* compatible with Google/Microsoft Authenticator. The shared secret is stored
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* encrypted (AES-256-GCM) with security.app_key, which lives outside the
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* document root. Recovery codes are stored as HMACs keyed with the same key.
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*/
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const TOTP_PERIOD = 30;
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const TOTP_DIGITS = 6;
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const TOTP_WINDOW = 1; // accept one step before/after for clock drift
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const OTP_MAX_FAILS = 5; // wrong codes within LOGIN_WINDOW_MIN before the login is dropped
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const RECOVERY_CODE_COUNT = 10;
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const BASE32_ALPHABET = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ234567';
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function app_key(): string
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{
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$key = base64_decode((string)(security_config()['app_key'] ?? ''), true);
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if ($key === false || strlen($key) !== 32) {
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throw new RuntimeException('security.app_key belum diisi (32 byte base64); dibutuhkan untuk OTP.');
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}
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return $key;
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}
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function base32_encode(string $bin): string
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{
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$bits = '';
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foreach (str_split($bin) as $ch) {
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$bits .= str_pad(decbin(ord($ch)), 8, '0', STR_PAD_LEFT);
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}
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$out = '';
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foreach (str_split($bits, 5) as $chunk) {
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$out .= BASE32_ALPHABET[bindec(str_pad($chunk, 5, '0'))];
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}
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return $out;
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}
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function base32_decode(string $b32): string
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{
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$bits = '';
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foreach (str_split(strtoupper(preg_replace('/[^A-Za-z2-7]/', '', $b32))) as $ch) {
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$bits .= str_pad(decbin(strpos(BASE32_ALPHABET, $ch)), 5, '0', STR_PAD_LEFT);
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}
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$out = '';
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foreach (str_split($bits, 8) as $byte) {
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if (strlen($byte) === 8) {
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$out .= chr(bindec($byte));
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}
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}
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return $out;
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}
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function totp_new_secret(): string
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{
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return base32_encode(random_bytes(20)); // 160-bit, as recommended by RFC 4226
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}
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function totp_code(string $secret, int $step): string
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{
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$hash = hash_hmac('sha1', pack('J', $step), base32_decode($secret), true);
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$offset = ord($hash[19]) & 0x0f;
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$bin = ((ord($hash[$offset]) & 0x7f) << 24) | (ord($hash[$offset + 1]) << 16)
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| (ord($hash[$offset + 2]) << 8) | ord($hash[$offset + 3]);
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return str_pad((string)($bin % (10 ** TOTP_DIGITS)), TOTP_DIGITS, '0', STR_PAD_LEFT);
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}
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/** The matching time step, or null. Steps at or before $lastStep are refused (no replay). */
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function totp_verify(string $secret, string $code, ?int $lastStep): ?int
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{
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$code = preg_replace('/\D/', '', $code);
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if (strlen($code) !== TOTP_DIGITS) {
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return null;
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}
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$now = intdiv(time(), TOTP_PERIOD);
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for ($s = $now - TOTP_WINDOW; $s <= $now + TOTP_WINDOW; $s++) {
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if (($lastStep === null || $s > $lastStep) && hash_equals(totp_code($secret, $s), $code)) {
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return $s;
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}
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}
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return null;
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}
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function totp_uri(string $secret, string $username): string
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{
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$label = rawurlencode('SERUBI Bank Papua:' . $username);
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return "otpauth://totp/$label?secret=$secret&issuer=" . rawurlencode('SERUBI Bank Papua') . '&period=' . TOTP_PERIOD . '&digits=' . TOTP_DIGITS;
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}
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function secret_encrypt(string $plain): string
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{
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$iv = random_bytes(12);
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$tag = '';
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$ct = openssl_encrypt($plain, 'aes-256-gcm', app_key(), OPENSSL_RAW_DATA, $iv, $tag);
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return base64_encode($iv . $tag . $ct);
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}
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function secret_decrypt(string $stored): string
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{
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$raw = (string)base64_decode($stored, true);
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$plain = openssl_decrypt(substr($raw, 28), 'aes-256-gcm', app_key(), OPENSSL_RAW_DATA, substr($raw, 0, 12), substr($raw, 12, 16));
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if ($plain === false) {
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throw new RuntimeException('OTP secret tidak dapat dibuka (app_key berubah?).');
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}
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return $plain;
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}
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function recovery_hash(string $code): string
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{
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return hash_hmac('sha256', strtoupper(preg_replace('/[^A-Za-z0-9]/', '', $code)), app_key());
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}
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/** Fresh one-time codes like "K7QD-M2XP": [plain codes to show once, hashes to store]. */
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function recovery_codes_new(): array
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{
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$plain = [];
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for ($i = 0; $i < RECOVERY_CODE_COUNT; $i++) {
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$c = substr(base32_encode(random_bytes(5)), 0, 8);
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$plain[] = substr($c, 0, 4) . '-' . substr($c, 4);
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}
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return [$plain, array_map('recovery_hash', $plain)];
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}
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