Martin Slachta
50 lines
1.8 KiB
PHP
50 lines
1.8 KiB
PHP
<?php
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if ( ! defined( 'ABSPATH' ) ) {
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exit; // Exit if accessed directly.
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}
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/**
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* Symmetric encryption for secrets kept in wp_options (Google OAuth access /
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* refresh tokens and the client secret).
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*
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* Uses libsodium's secretbox with a 32-byte key derived from the site's
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* AUTH_KEY / AUTH_SALT. Ciphertext is prefixed with "rsvenc:" so decrypt() can
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* transparently pass through values that were written as plaintext before this
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* was introduced — existing installs migrate to encrypted storage on the next
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* write (e.g. the next token refresh).
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*/
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final class RsvCrypto {
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private const PREFIX = 'rsvenc:';
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public static function encrypt(string $plaintext): string {
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$nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
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$cipher = sodium_crypto_secretbox($plaintext, $nonce, self::key());
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return self::PREFIX . base64_encode($nonce . $cipher);
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}
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/** Returns the plaintext, or null if a ciphertext can't be decrypted. */
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public static function decrypt(string $stored): ?string {
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if (!str_starts_with($stored, self::PREFIX)) {
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return $stored; // legacy plaintext — pass through for migration
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}
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$raw = base64_decode(substr($stored, strlen(self::PREFIX)), true);
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if ($raw === false || strlen($raw) <= SODIUM_CRYPTO_SECRETBOX_NONCEBYTES) {
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return null;
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}
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$nonce = substr($raw, 0, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
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$cipher = substr($raw, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
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$plain = sodium_crypto_secretbox_open($cipher, $nonce, self::key());
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return $plain === false ? null : $plain;
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}
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/** 32-byte key derived from the site's auth salts. */
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private static function key(): string {
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$material = (defined('AUTH_KEY') ? AUTH_KEY : '') . '|' . (defined('AUTH_SALT') ? AUTH_SALT : '');
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return hash('sha256', $material, true);
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}
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}
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