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| 1 | <?php declare(strict_types=1); |
| 2 | /** |
| 3 | * PrivateBin |
| 4 | * |
| 5 | * a zero-knowledge paste bin |
| 6 | * |
| 7 | * @link https://github.com/PrivateBin/PrivateBin |
| 8 | * @copyright 2012 Sébastien SAUVAGE (sebsauvage.net) |
| 9 | * @license https://www.opensource.org/licenses/zlib-license.php The zlib/libpng License |
| 10 | */ |
| 11 | |
| 12 | namespace PrivateBin; |
| 13 | |
| 14 | /** |
| 15 | * FormatV2 |
| 16 | * |
| 17 | * Provides validation function for version 2 format of pastes & comments. |
| 18 | */ |
| 19 | class FormatV2 |
| 20 | { |
| 21 | /** |
| 22 | * version 2 format validator |
| 23 | * |
| 24 | * Checks if the given array is a proper version 2 formatted, encrypted message. |
| 25 | * |
| 26 | * @access public |
| 27 | * @static |
| 28 | * @param array $message |
| 29 | * @param bool $isComment |
| 30 | * @return bool |
| 31 | */ |
| 32 | public static function isValid($message, $isComment = false) |
| 33 | { |
| 34 | $required_keys = array('adata', 'v', 'ct'); |
| 35 | if ($isComment) { |
| 36 | $required_keys[] = 'pasteid'; |
| 37 | $required_keys[] = 'parentid'; |
| 38 | } else { |
| 39 | $required_keys[] = 'meta'; |
| 40 | } |
| 41 | |
| 42 | // Make sure no additionnal keys were added. |
| 43 | if (count(array_keys($message)) != count($required_keys)) { |
| 44 | return false; |
| 45 | } |
| 46 | |
| 47 | // Make sure required fields are present. |
| 48 | foreach ($required_keys as $k) { |
| 49 | if (!array_key_exists($k, $message)) { |
| 50 | return false; |
| 51 | } |
| 52 | } |
| 53 | |
| 54 | // Make sure adata is an array. |
| 55 | if (!is_array($message['adata'])) { |
| 56 | return false; |
| 57 | } |
| 58 | |
| 59 | $cipherParams = $isComment ? $message['adata'] : $message['adata'][0]; |
| 60 | |
| 61 | // Make sure some fields are base64 data: |
| 62 | // - initialization vector |
| 63 | if (!base64_decode($cipherParams[0], true)) { |
| 64 | return false; |
| 65 | } |
| 66 | // - salt |
| 67 | if (!base64_decode($cipherParams[1], true)) { |
| 68 | return false; |
| 69 | } |
| 70 | // - cipher text |
| 71 | if (!($ct = base64_decode($message['ct'], true))) { |
| 72 | return false; |
| 73 | } |
| 74 | |
| 75 | // Make sure some fields have a reasonable size: |
| 76 | // - initialization vector |
| 77 | if (strlen($cipherParams[0]) > 24) { |
| 78 | return false; |
| 79 | } |
| 80 | // - salt |
| 81 | if (strlen($cipherParams[1]) > 14) { |
| 82 | return false; |
| 83 | } |
| 84 | |
| 85 | // Make sure some fields contain no unsupported values: |
| 86 | // - version |
| 87 | if (!(is_int($message['v']) || is_float($message['v'])) || (float) $message['v'] < 2) { |
| 88 | return false; |
| 89 | } |
| 90 | // - iterations, refuse less then 10000 iterations (minimum NIST recommendation) |
| 91 | if (!is_int($cipherParams[2]) || $cipherParams[2] <= 10000) { |
| 92 | return false; |
| 93 | } |
| 94 | // - key size |
| 95 | if (!in_array($cipherParams[3], array(128, 192, 256), true)) { |
| 96 | return false; |
| 97 | } |
| 98 | // - tag size |
| 99 | if (!in_array($cipherParams[4], array(64, 96, 128), true)) { |
| 100 | return false; |
| 101 | } |
| 102 | // - algorithm, must be AES |
| 103 | if ($cipherParams[5] !== 'aes') { |
| 104 | return false; |
| 105 | } |
| 106 | // - mode |
| 107 | if (!in_array($cipherParams[6], array('ctr', 'cbc', 'gcm'), true)) { |
| 108 | return false; |
| 109 | } |
| 110 | // - compression |
| 111 | if (!in_array($cipherParams[7], array('zlib', 'none'), true)) { |
| 112 | return false; |
| 113 | } |
| 114 | |
| 115 | // Reject data if entropy is too low |
| 116 | if (strlen($ct) > strlen(gzdeflate($ct))) { |
| 117 | return false; |
| 118 | } |
| 119 | |
| 120 | // require only the key 'expire' in the metadata of pastes |
| 121 | if (!$isComment && ( |
| 122 | count($message['meta']) === 0 || |
| 123 | !array_key_exists('expire', $message['meta']) || |
| 124 | count($message['meta']) > 1 |
| 125 | )) { |
| 126 | return false; |
| 127 | } |
| 128 | |
| 129 | return true; |
| 130 | } |
| 131 | } |