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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 | $required_keys = ['adata', 'v', 'ct']; |
| 35 | if ($isComment) { |
| 36 | $required_keys[] = 'pasteid'; |
| 37 | $required_keys[] = 'parentid'; |
| 38 | } else { |
| 39 | $required_keys[] = 'meta'; |
| 40 | } |
| 41 | |
| 42 | // Make sure no additional keys were added. |
| 43 | if (count(array_keys($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] ?? null); |
| 60 | |
| 61 | // Make sure the cipher parameters are a properly sized array. |
| 62 | if (!is_array($cipherParams) || count($cipherParams) < 8) { |
| 63 | return false; |
| 64 | } |
| 65 | |
| 66 | // Make sure the adata parameters of pastes are a properly sized array |
| 67 | $adataLength = count($message['adata']); |
| 68 | |
| 69 | // Comments may authenticate their document and parent IDs, by |
| 70 | // appending them to the cipher parameters. These must match the |
| 71 | // unencrypted IDs, which are validated by the comment model. |
| 72 | if ($isComment) { |
| 73 | if ($adataLength !== 8 && ( |
| 74 | count($cipherParams) !== 10 || |
| 75 | !is_string($cipherParams[8]) || |
| 76 | !is_string($cipherParams[9]) || |
| 77 | $cipherParams[8] !== $message['pasteid'] || |
| 78 | $cipherParams[9] !== $message['parentid'] |
| 79 | )) { |
| 80 | return false; |
| 81 | } |
| 82 | // For pastes: adata must have exactly 4 entries, |
| 83 | // and meta must contain only the 'expire' key. |
| 84 | } elseif ($adataLength !== 4 || |
| 85 | !is_array($message['meta']) || |
| 86 | count($message['meta']) !== 1 || |
| 87 | !array_key_exists('expire', $message['meta']) |
| 88 | ) { |
| 89 | return false; |
| 90 | } |
| 91 | |
| 92 | // Make sure the ciphertext and the cipher parameters used in the |
| 93 | // string operations below are actually strings, so that malformed |
| 94 | // input yields "Invalid data." instead of a fatal type error. |
| 95 | if (!is_string($message['ct']) || |
| 96 | !is_string($cipherParams[0] ?? null) || |
| 97 | !is_string($cipherParams[1] ?? null)) { |
| 98 | return false; |
| 99 | } |
| 100 | |
| 101 | // Make sure some fields are base64 data: |
| 102 | // - initialization vector |
| 103 | if (!base64_decode($cipherParams[0], true)) { |
| 104 | return false; |
| 105 | } |
| 106 | // - salt |
| 107 | if (!base64_decode($cipherParams[1], true)) { |
| 108 | return false; |
| 109 | } |
| 110 | // - cipher text |
| 111 | if (!($ct = base64_decode($message['ct'], true))) { |
| 112 | return false; |
| 113 | } |
| 114 | |
| 115 | // Make sure some fields have a reasonable size: |
| 116 | // - initialization vector |
| 117 | if (strlen($cipherParams[0]) > 24) { |
| 118 | return false; |
| 119 | } |
| 120 | // - salt |
| 121 | if (strlen($cipherParams[1]) > 14) { |
| 122 | return false; |
| 123 | } |
| 124 | |
| 125 | // Make sure some fields contain no unsupported values: |
| 126 | // - version |
| 127 | if (!(is_int($message['v']) || is_float($message['v'])) || (float) $message['v'] < 2) { |
| 128 | return false; |
| 129 | } |
| 130 | // - iterations, refuse less then 10000 iterations (minimum NIST recommendation) |
| 131 | if (!is_int($cipherParams[2]) || $cipherParams[2] <= 10000) { |
| 132 | return false; |
| 133 | } |
| 134 | // - key size |
| 135 | if (!in_array($cipherParams[3], [128, 192, 256], true)) { |
| 136 | return false; |
| 137 | } |
| 138 | // - tag size |
| 139 | if (!in_array($cipherParams[4], [64, 96, 128], true)) { |
| 140 | return false; |
| 141 | } |
| 142 | // - algorithm, must be AES |
| 143 | if ($cipherParams[5] !== 'aes') { |
| 144 | return false; |
| 145 | } |
| 146 | // - mode |
| 147 | if (!in_array($cipherParams[6], ['ctr', 'cbc', 'gcm'], true)) { |
| 148 | return false; |
| 149 | } |
| 150 | // - compression |
| 151 | if (!in_array($cipherParams[7], ['zlib', 'none'], true)) { |
| 152 | return false; |
| 153 | } |
| 154 | |
| 155 | // Reject data if entropy is too low |
| 156 | if (strlen($ct) > strlen(gzdeflate($ct))) { |
| 157 | return false; |
| 158 | } |
| 159 | |
| 160 | return true; |
| 161 | } |
| 162 | } |