aes.php

<?php
if (!defined('IN_XSS_PLATFORM')) {
    exit('Access Denied');
}

/*Aes.php
 *Date 2009/09/04
 *Auth song_qilin
 *Copyright Copyright (c) 2009 Kylix
 */

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  AES implementation in PHP (c) Chris Veness 2005-2008. Right of free use is granted for all    */
/*    commercial or non-commercial use. No warranty of any form is offered.                       */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

/**
 * AES Cipher function: encrypt 'input' with Rijndael algorithm
 *
 * @param input message as byte-array (16 bytes)
 * @param w     key schedule as 2D byte-array (Nr+1 x Nb bytes) - 
 *              generated from the cipher key by KeyExpansion()
 * @return      ciphertext as byte-array (16 bytes)
 */
function Cipher($input, $w) {// main Cipher function [§5.1]
    $Nb = 4; // block size (in words): no of columns in state (fixed at 4 for AES)
    $Nr = count($w) / $Nb - 1; // no of rounds: 10/12/14 for 128/192/256-bit keys
    
    $state = array(); // initialise 4xNb byte-array 'state' with input [§3.4]
    for ($i = 0; $i < 4 * $Nb; $i++)
        $state[$i % 4][floor($i / 4)] = $input[$i];
    
    $state = AddRoundKey($state, $w, 0, $Nb);
    
    for ($round = 1; $round < $Nr; $round++) { // apply Nr rounds
        $state = SubBytes($state, $Nb);
        $state = ShiftRows($state, $Nb);
        $state = MixColumns($state, $Nb);
        $state = AddRoundKey($state, $w, $round, $Nb);
    }
    
    $state = SubBytes($state, $Nb);
    $state = ShiftRows($state, $Nb);
    $state = AddRoundKey($state, $w, $Nr, $Nb);
    
    $output = array(
        4 * $Nb
    ); // convert state to 1-d array before returning [§3.4]
    for ($i = 0; $i < 4 * $Nb; $i++)
        $output[$i] = $state[$i % 4][floor($i / 4)];
    return $output;
}


function AddRoundKey($state, $w, $rnd, $Nb) {// xor Round Key into state S [§5.1.4]
    for ($r = 0; $r < 4; $r++) {
        for ($c = 0; $c < $Nb; $c++)
            $state[$r][$c] ^= $w[$rnd * 4 + $c][$r];
    }
    return $state;
}

function SubBytes($s, $Nb) {// apply SBox to state S [§5.1.1]
    global $Sbox; // PHP needs explicit declaration to access global variables!
    for ($r = 0; $r < 4; $r++) {
        for ($c = 0; $c < $Nb; $c++)
            $s[$r][$c] = $Sbox[$s[$r][$c]];
    }
    return $s;
}

function ShiftRows($s, $Nb) {// shift row r of state S left by r bytes [§5.1.2]
    $t = array(
        4
    );
    for ($r = 1; $r < 4; $r++) {
        for ($c = 0; $c < 4; $c++)
            $t[$c] = $s[$r][($c + $r) % $Nb]; // shift into temp copy
        for ($c = 0; $c < 4; $c++)
            $s[$r][$c] = $t[$c]; // and copy back
    } // note that this will work for Nb=4,5,6, but not 7,8 (always 4 for AES):
    return $s; // see fp.gladman.plus.com/cryptography_technology/rijndael/aes.spec.311.pdf 
}

function MixColumns($s, $Nb) {// combine bytes of each col of state S [§5.1.3]
    for ($c = 0; $c < 4; $c++) {
        $a = array(
            4
        ); // 'a' is a copy of the current column from 's'
        $b = array(
            4
        ); // 'b' is a?{02} in GF(2^8)
        for ($i = 0; $i < 4; $i++) {
            $a[$i] = $s[$i][$c];
            $b[$i] = $s[$i][$c] & 0x80 ? $s[$i][$c] << 1 ^ 0x011b : $s[$i][$c] << 1;
        }
        // a[n] ^ b[n] is a?{03} in GF(2^8)
        $s[0][$c] = $b[0] ^ $a[1] ^ $b[1] ^ $a[2] ^ $a[3]; // 2*a0 + 3*a1 + a2 + a3
        $s[1][$c] = $a[0] ^ $b[1] ^ $a[2] ^ $b[2] ^ $a[3]; // a0 * 2*a1 + 3*a2 + a3
        $s[2][$c] = $a[0] ^ $a[1] ^ $b[2] ^ $a[3] ^ $b[3]; // a0 + a1 + 2*a2 + 3*a3
        $s[3][$c] = $a[0] ^ $b[0] ^ $a[1] ^ $a[2] ^ $b[3]; // 3*a0 + a1 + a2 + 2*a3
    }
    return $s;
}

/**
 * Key expansion for Rijndael Cipher(): performs key expansion on cipher key
 * to generate a key schedule
 *
 * @param key cipher key byte-array (16 bytes)
 * @return    key schedule as 2D byte-array (Nr+1 x Nb bytes)
 */
function KeyExpansion($key) {// generate Key Schedule from Cipher Key [§5.2]
    global $Rcon; // PHP needs explicit declaration to access global variables!
    $Nb = 4; // block size (in words): no of columns in state (fixed at 4 for AES)
    $Nk = count($key) / 4; // key length (in words): 4/6/8 for 128/192/256-bit keys
    $Nr = $Nk + 6; // no of rounds: 10/12/14 for 128/192/256-bit keys
    
    $w    = array();
    $temp = array();
    
    for ($i = 0; $i < $Nk; $i++) {
        $r     = array(
            $key[4 * $i],
            $key[4 * $i + 1],
            $key[4 * $i + 2],
            $key[4 * $i + 3]
        );
        $w[$i] = $r;
    }
    
    for ($i = $Nk; $i < ($Nb * ($Nr + 1)); $i++) {
        $w[$i] = array();
        for ($t = 0; $t < 4; $t++)
            $temp[$t] = $w[$i - 1][$t];
        if ($i % $Nk == 0) {
            $temp = SubWord(RotWord($temp));
            for ($t = 0; $t < 4; $t++)
                $temp[$t] ^= $Rcon[$i / $Nk][$t];
        } else if ($Nk > 6 && $i % $Nk == 4) {
            $temp = SubWord($temp);
        }
        for ($t = 0; $t < 4; $t++)
            $w[$i][$t] = $w[$i - $Nk][$t] ^ $temp[$t];
    }
    return $w;
}

function SubWord($w) {// apply SBox to 4-byte word w
    global $Sbox; // PHP needs explicit declaration to access global variables!
    for ($i = 0; $i < 4; $i++)
        $w[$i] = $Sbox[$w[$i]];
    return $w;
}

function RotWord($w) {// rotate 4-byte word w left by one byte
    $w[4] = $w[0];
    for ($i = 0; $i < 4; $i++)
        $w[$i] = $w[$i + 1];
    return $w;
}

// Sbox is pre-computed multiplicative inverse in GF(2^8) used in SubBytes and KeyExpansion [§5.1.1]
$Sbox = array(0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
              0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
              0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
              0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
              0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
              0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
              0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
              0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
              0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
              0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
              0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
              0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
              0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
              0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
              0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
              0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16);

// Rcon is Round Constant used for the Key Expansion [1st col is 2^(r-1) in GF(2^8)] [§5.2]
$Rcon = array( array(0x00, 0x00, 0x00, 0x00),
               array(0x01, 0x00, 0x00, 0x00),
               array(0x02, 0x00, 0x00, 0x00),
               array(0x04, 0x00, 0x00, 0x00),
               array(0x08, 0x00, 0x00, 0x00),
               array(0x10, 0x00, 0x00, 0x00),
               array(0x20, 0x00, 0x00, 0x00),
               array(0x40, 0x00, 0x00, 0x00),
               array(0x80, 0x00, 0x00, 0x00),
               array(0x1b, 0x00, 0x00, 0x00),
               array(0x36, 0x00, 0x00, 0x00) );


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

/** 
 * Encrypt a text using AES encryption in Counter mode of operation
 *  - see http://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf
 *
 * Unicode multi-byte character safe
 *
 * @param plaintext source text to be encrypted
 * @param password  the password to use to generate a key
 * @param nBits     number of bits to be used in the key (128, 192, or 256)
 * @return          encrypted text
 */
function AESEncryptCtr($plaintext, $password = "blue-lotus", $nBits = 128) {
    $blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
    if (!($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;
    $key = Cipher($pwBytes, KeyExpansion($pwBytes));
    $key = array_merge($key, array_slice($key, 0, $nBytes - 16)); // expand key to 16/24/32 bytes long 
    
    // initialise counter block (NIST SP800-38A §B.2): millisecond time-stamp for nonce in 
    // 1st 8 bytes, block counter in 2nd 8 bytes
    $counterBlock = array();
    $nonce        = floor(microtime(true) * 1000); // timestamp: milliseconds since 1-Jan-1970
    $nonceSec     = floor($nonce / 1000);
    $nonceMs      = $nonce % 1000;
    // encode nonce with seconds in 1st 4 bytes, and (repeated) ms part filling 2nd 4 bytes
    for ($i = 0; $i < 4; $i++)
        $counterBlock[$i] = urs($nonceSec, $i * 8) & 0xff;
    for ($i = 0; $i < 4; $i++)
        $counterBlock[$i + 4] = $nonceMs & 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
    $keySchedule = KeyExpansion($key);
    
    $blockCount = ceil(strlen($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 - $c] = urs($b, $c * 8) & 0xff;
        for ($c = 0; $c < 4; $c++)
            $counterBlock[15 - $c - 4] = urs($b / 0x100000000, $c * 8);
        
        $cipherCntr = Cipher($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);
    $ciphertext = base64_encode($ciphertext);
    return $ciphertext;
}


/** 
 * Decrypt a text encrypted by AES in counter mode of operation
 *
 * @param ciphertext source text to be decrypted
 * @param password   the password to use to generate a key
 * @param nBits      number of bits to be used in the key (128, 192, or 256)
 * @return           decrypted text
 */
function AESDecryptCtr($ciphertext, $password = "blue-lotus", $nBits = 128) {
    $blockSize = 16; // block size fixed at 16 bytes / 128 bits (Nb=4) for AES
    if (!($nBits == 128 || $nBits == 192 || $nBits == 256))
        return ''; // standard allows 128/192/256 bit keys
    $ciphertext = base64_decode($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;
    $key = Cipher($pwBytes, 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
    $keySchedule = KeyExpansion($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 - $c] = urs($b, $c * 8) & 0xff;
        for ($c = 0; $c < 4; $c++)
            $counterBlock[15 - $c - 4] = urs(($b + 1) / 0x100000000 - 1, $c * 8) & 0xff;
        
        $cipherCntr = Cipher($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 a  number to be shifted (32-bit integer)
 * @param b  number of bits to shift a to the right (0..31)
 * @return   a right-shifted and zero-filled by b bits
 */
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
        $a = $a >> ($b - 1); //   remaining right-shifts
    } else { // otherwise
        $a = ($a >> $b); //   use normal right-shift
    }
    return $a;
}