132 lines
3.6 KiB
PHP
132 lines
3.6 KiB
PHP
<?php
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/**
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* PrivateBin
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*
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* a zero-knowledge paste bin
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*
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* @link https://github.com/PrivateBin/PrivateBin
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* @copyright 2012 Sébastien SAUVAGE (sebsauvage.net)
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* @license https://www.opensource.org/licenses/zlib-license.php The zlib/libpng License
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* @version 1.7.0
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*/
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namespace PrivateBin;
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/**
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* FormatV2
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*
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* Provides validation function for version 2 format of pastes & comments.
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*/
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class FormatV2
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{
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/**
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* version 2 format validator
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*
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* Checks if the given array is a proper version 2 formatted, encrypted message.
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*
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* @access public
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* @static
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* @param array $message
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* @param bool $isComment
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* @return bool
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*/
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public static function isValid($message, $isComment = false)
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{
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$required_keys = array('adata', 'v', 'ct');
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if ($isComment) {
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$required_keys[] = 'pasteid';
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$required_keys[] = 'parentid';
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} else {
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$required_keys[] = 'meta';
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}
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// Make sure no additionnal keys were added.
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if (count(array_keys($message)) != count($required_keys)) {
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return false;
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}
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// Make sure required fields are present.
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foreach ($required_keys as $k) {
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if (!array_key_exists($k, $message)) {
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return false;
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}
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}
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// Make sure adata is an array.
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if (!is_array($message['adata'])) {
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return false;
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}
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$cipherParams = $isComment ? $message['adata'] : $message['adata'][0];
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// Make sure some fields are base64 data:
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// - initialization vector
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if (!base64_decode($cipherParams[0], true)) {
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return false;
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}
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// - salt
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if (!base64_decode($cipherParams[1], true)) {
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return false;
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}
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// - cipher text
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if (!($ct = base64_decode($message['ct'], true))) {
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return false;
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}
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// Make sure some fields have a reasonable size:
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// - initialization vector
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if (strlen($cipherParams[0]) > 24) {
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return false;
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}
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// - salt
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if (strlen($cipherParams[1]) > 14) {
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return false;
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}
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// Make sure some fields contain no unsupported values:
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// - version
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if (!(is_int($message['v']) || is_float($message['v'])) || (float) $message['v'] < 2) {
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return false;
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}
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// - iterations, refuse less then 10000 iterations (minimum NIST recommendation)
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if (!is_int($cipherParams[2]) || $cipherParams[2] <= 10000) {
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return false;
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}
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// - key size
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if (!in_array($cipherParams[3], array(128, 192, 256), true)) {
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return false;
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}
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// - tag size
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if (!in_array($cipherParams[4], array(64, 96, 128), true)) {
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return false;
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}
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// - algorithm, must be AES
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if ($cipherParams[5] !== 'aes') {
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return false;
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}
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// - mode
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if (!in_array($cipherParams[6], array('ctr', 'cbc', 'gcm'), true)) {
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return false;
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}
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// - compression
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if (!in_array($cipherParams[7], array('zlib', 'none'), true)) {
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return false;
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}
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// Reject data if entropy is too low
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if (strlen($ct) > strlen(gzdeflate($ct))) {
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return false;
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}
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// require only the key 'expire' in the metadata of pastes
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if (!$isComment && (
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count($message['meta']) === 0 ||
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!array_key_exists('expire', $message['meta']) ||
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count($message['meta']) > 1
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)) {
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return false;
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}
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return true;
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}
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}
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