1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 <?php
/**
* Abandoned Cart Pro for WooCommerce
*
* AES counter (CTR) mode implementation in PHP
*
* @author Tyche Softwares
* @package Abandoned-Cart-Pro-for-WooCommerce/Encrypt-Decrypt-Data
* @since 3.0
*/
Class Wcap_Aes_Ctr extends Wcap_Aes
{
/**
* Encrypt a text using AES encryption in Counter mode of operation. Unicode multi-byte character safe
*
* @param plaintext $plaintext source text to be encrypted
* @param password $password the password to use to generate a key
* @param nBits $nBits number of bits to be used in the key (128, 192, or 256)
* @return text $ciphertext encrypted text
* @since 3.0
*/
public static function encrypt($plaintext, $password, $nBits)
{
$blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
if (!($nBits == 128 || $nBits == 192 || $nBits == 256)) return ''; // standard allows 128/192/256 bit keys
// note PHP (5) gives us plaintext and password in UTF8 encoding!
// use AES itself to encrypt password to get cipher key (using plain password as source for
// key expansion) - gives us well encrypted key
$nBytes = $nBits / 8; // no bytes in key
$pwBytes = array();
for ($i = 0; $i < $nBytes; $i++) $pwBytes[$i] = ord(substr($password, $i, 1)) & 0xff;
$key = Wcap_Aes::cipher($pwBytes, Wcap_Aes::keyExpansion($pwBytes));
$key = array_merge($key, array_slice($key, 0, $nBytes - 16)); // expand key to 16/24/32 bytes long
// initialise 1st 8 bytes of counter block with nonce (NIST SP800-38A B.2): [0-1] = millisec,
// [2-3] = random, [4-7] = seconds, giving guaranteed sub-ms uniqueness up to Feb 2106
$counterBlock = array();
$nonce = floor(microtime(true) * 1000); // timestamp: milliseconds since 1-Jan-1970
$nonceMs = $nonce % 1000;
$nonceSec = floor($nonce / 1000);
$nonceRnd = floor(rand(0, 0xffff));
for ($i = 0; $i < 2; $i++) $counterBlock[$i] = self::urs($nonceMs, $i * 8) & 0xff;
for ($i = 0; $i < 2; $i++) $counterBlock[$i + 2] = self::urs($nonceRnd, $i * 8) & 0xff;
for ($i = 0; $i < 4; $i++) $counterBlock[$i + 4] = self::urs($nonceSec, $i * 8) & 0xff;
// and convert it to a string to go on the front of the ciphertext
$ctrTxt = '';
for ($i = 0; $i < 8; $i++) $ctrTxt .= chr($counterBlock[$i]);
// generate key schedule - an expansion of the key into distinct Key Rounds for each round
$keySchedule = Wcap_Aes::keyExpansion($key);
//print_r($keySchedule);
$blockCount = ceil(strlen($plaintext) / $blockSize);
$ciphertxt = array(); // ciphertext as array of strings
for ($b = 0; $b < $blockCount; $b++) {
// set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
// done in two stages for 32-bit ops: using two words allows us to go past 2^32 blocks (68GB)
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c] = self::urs($b, $c * 8) & 0xff;
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c - 4] = self::urs($b / 0x100000000, $c * 8);
$cipherCntr = Wcap_Aes::cipher($counterBlock, $keySchedule); // -- encrypt counter block --
// block size is reduced on final block
$blockLength = $b < $blockCount - 1 ? $blockSize : (strlen($plaintext) - 1) % $blockSize + 1;
$cipherByte = array();
for ($i = 0; $i < $blockLength; $i++) { // -- xor plaintext with ciphered counter byte-by-byte --
$cipherByte[$i] = $cipherCntr[$i] ^ ord(substr($plaintext, $b * $blockSize + $i, 1));
$cipherByte[$i] = chr($cipherByte[$i]);
}
$ciphertxt[$b] = implode('', $cipherByte); // escape troublesome characters in ciphertext
}
// implode is more efficient than repeated string concatenation
$ciphertext = $ctrTxt . implode('', $ciphertxt);
$ciphertext = self::base64url_encode($ciphertext);
return $ciphertext;
}
/**
* Decrypt a text encrypted by AES in counter mode of operation
*
* @param ciphertext $ciphertext source text to be decrypted
* @param password $password the password to use to generate a key
* @param nBits $nBits number of bits to be used in the key (128, 192, or 256)
* @return text $plaintext decrypted text
* @since 3.0
*/
public static function decrypt($ciphertext, $password, $nBits)
{
$blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
if (!($nBits == 128 || $nBits == 192 || $nBits == 256)) return ''; // standard allows 128/192/256 bit keys
$ciphertext = self::base64url_decode($ciphertext);
// use AES to encrypt password (mirroring encrypt routine)
$nBytes = $nBits / 8; // no bytes in key
$pwBytes = array();
for ($i = 0; $i < $nBytes; $i++) $pwBytes[$i] = ord(substr($password, $i, 1)) & 0xff;
$key = Wcap_Aes::cipher($pwBytes, Wcap_Aes::keyExpansion($pwBytes));
$key = array_merge($key, array_slice($key, 0, $nBytes - 16)); // expand key to 16/24/32 bytes long
// recover nonce from 1st element of ciphertext
$counterBlock = array();
$ctrTxt = substr($ciphertext, 0, 8);
for ($i = 0; $i < 8; $i++) $counterBlock[$i] = ord(substr($ctrTxt, $i, 1));
// generate key schedule
$keySchedule = Wcap_Aes::keyExpansion($key);
// separate ciphertext into blocks (skipping past initial 8 bytes)
$nBlocks = ceil((strlen($ciphertext) - 8) / $blockSize);
$ct = array();
for ($b = 0; $b < $nBlocks; $b++) $ct[$b] = substr($ciphertext, 8 + $b * $blockSize, 16);
$ciphertext = $ct; // ciphertext is now array of block-length strings
// plaintext will get generated block-by-block into array of block-length strings
$plaintxt = array();
for ($b = 0; $b < $nBlocks; $b++) {
// set counter (block #) in last 8 bytes of counter block (leaving nonce in 1st 8 bytes)
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c] = self::urs($b, $c * 8) & 0xff;
for ($c = 0; $c < 4; $c++) $counterBlock[15 - $c - 4] = self::urs(($b + 1) / 0x100000000 - 1, $c * 8) & 0xff;
$cipherCntr = Wcap_Aes::cipher($counterBlock, $keySchedule); // encrypt counter block
$plaintxtByte = array();
for ($i = 0; $i < strlen($ciphertext[$b]); $i++) {
// -- xor plaintext with ciphered counter byte-by-byte --
$plaintxtByte[$i] = $cipherCntr[$i] ^ ord(substr($ciphertext[$b], $i, 1));
$plaintxtByte[$i] = chr($plaintxtByte[$i]);
}
$plaintxt[$b] = implode('', $plaintxtByte);
}
// join array of blocks into single plaintext string
$plaintext = implode('', $plaintxt);
return $plaintext;
}
/**
* Unsigned right shift function, since PHP has neither >>> operator nor unsigned ints
*
* @param number $a a number to be shifted (32-bit integer)
* @param number $b b number of bits to shift a to the right (0..31)
* @return number $a a right-shifted and zero-filled by b bits
* @since 3.0
*/
private static function urs($a, $b)
{
$a &= 0xffffffff;
$b &= 0x1f; // (bounds check)
if ($a & 0x80000000 && $b > 0) { // if left-most bit set
$a = ($a >> 1) & 0x7fffffff; // right-shift one bit & clear left-most bit
$check = $b - 1;
$a = $a >> ($check); // remaining right-shifts
} else { // otherwise
$a = ($a >> $b); // use normal right-shift
}
return $a;
}
/**
* Encoding for base64 encoded strings
*
* @param string $data base64 encoded string
*
* @return string URL Friendly string
*/
public static function base64url_encode($data) {
return rtrim(strtr(base64_encode($data), '+/', '-_'), '=');
}
/**
* Encoding for base64 encoded strings
*
* @param string $data URL Friendly string
*
* @return string base64 encoded string
*/
public static function base64url_decode($data) {
return base64_decode(str_pad(strtr($data, '-_', '+/'), strlen($data) % 4, '=', STR_PAD_RIGHT));
}
}