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<?php
/**
* Common String Functions
*
* PHP version 5
*
* @category Common
* @package Functions\Strings
* @author Jim Wigginton <terrafrost@php.net>
* @copyright 2016 Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @link http://phpseclib.sourceforge.net
*/
namespace phpseclib3\Common\Functions;
use phpseclib3\Math\BigInteger;
use phpseclib3\Math\Common\FiniteField;
/**
* Common String Functions
*
* @package Functions\Strings
* @author Jim Wigginton <terrafrost@php.net>
*/
abstract class Strings
{
/**
* String Shift
*
* Inspired by array_shift
*
* @param string $string
* @param int $index
* @access public
* @return string
*/
public static function shift(&$string, $index = 1)
{
$substr = substr($string, 0, $index);
$string = substr($string, $index);
return $substr;
}
/**
* String Pop
*
* Inspired by array_pop
*
* @param string $string
* @param int $index
* @access public
* @return string
*/
public static function pop(&$string, $index = 1)
{
$substr = substr($string, -$index);
$string = substr($string, 0, -$index);
return $substr;
}
/**
* Parse SSH2-style string
*
* Returns either an array or a boolean if $data is malformed.
*
* Valid characters for $format are as follows:
*
* C = byte
* b = boolean (true/false)
* N = uint32
* s = string
* i = mpint
* L = name-list
*
* uint64 is not supported.
*
* @param string $format
* @param string $data
* @return mixed
*/
public static function unpackSSH2($format, &$data)
{
$format = self::formatPack($format);
$result = [];
for ($i = 0; $i < strlen($format); $i++) {
switch ($format[$i]) {
case 'C':
case 'b':
if (!strlen($data)) {
throw new \LengthException('At least one byte needs to be present for successful C / b decodes');
}
break;
case 'N':
case 'i':
case 's':
case 'L':
if (strlen($data) < 4) {
throw new \LengthException('At least four byte needs to be present for successful N / i / s / L decodes');
}
break;
default:
throw new \InvalidArgumentException('$format contains an invalid character');
}
switch ($format[$i]) {
case 'C':
$result[] = ord(self::shift($data));
continue 2;
case 'b':
$result[] = ord(self::shift($data)) != 0;
continue 2;
case 'N':
list(, $temp) = unpack('N', self::shift($data, 4));
$result[] = $temp;
continue 2;
}
list(, $length) = unpack('N', self::shift($data, 4));
if (strlen($data) < $length) {
throw new \LengthException("$length bytes needed; " . strlen($data) . ' bytes available');
}
$temp = self::shift($data, $length);
switch ($format[$i]) {
case 'i':
$result[] = new BigInteger($temp, -256);
break;
case 's':
$result[] = $temp;
break;
case 'L':
$result[] = explode(',', $temp);
}
}
return $result;
}
/**
* Create SSH2-style string
*
* @param string[] ...$elements
* @access public
* @return mixed
*/
public static function packSSH2(...$elements)
{
$format = self::formatPack($elements[0]);
array_shift($elements);
if (strlen($format) != count($elements)) {
throw new \InvalidArgumentException('There must be as many arguments as there are characters in the $format string');
}
$result = '';
for ($i = 0; $i < strlen($format); $i++) {
$element = $elements[$i];
switch ($format[$i]) {
case 'C':
if (!is_int($element)) {
throw new \InvalidArgumentException('Bytes must be represented as an integer between 0 and 255, inclusive.');
}
$result.= pack('C', $element);
break;
case 'b':
if (!is_bool($element)) {
throw new \InvalidArgumentException('A boolean parameter was expected.');
}
$result.= $element ? "\1" : "\0";
break;
case 'N':
if (is_float($element)) {
$element = (int) $element;
}
if (!is_int($element)) {
throw new \InvalidArgumentException('An integer was expected.');
}
$result.= pack('N', $element);
break;
case 's':
if (!self::is_stringable($element)) {
throw new \InvalidArgumentException('A string was expected.');
}
$result.= pack('Na*', strlen($element), $element);
break;
case 'i':
if (!$element instanceof BigInteger && !$element instanceof FiniteField\Integer) {
throw new \InvalidArgumentException('A phpseclib3\Math\BigInteger or phpseclib3\Math\Common\FiniteField\Integer object was expected.');
}
$element = $element->toBytes(true);
$result.= pack('Na*', strlen($element), $element);
break;
case 'L':
if (!is_array($element)) {
throw new \InvalidArgumentException('An array was expected.');
}
$element = implode(',', $element);
$result.= pack('Na*', strlen($element), $element);
break;
default:
throw new \InvalidArgumentException('$format contains an invalid character');
}
}
return $result;
}
/**
* Expand a pack string
*
* Converts C5 to CCCCC, for example.
*
* @access private
* @param string $format
* @return string
*/
private static function formatPack($format)
{
$parts = preg_split('#(\d+)#', $format, -1, PREG_SPLIT_DELIM_CAPTURE);
$format = '';
for ($i = 1; $i < count($parts); $i+=2) {
$format.= substr($parts[$i - 1], 0, -1) . str_repeat(substr($parts[$i - 1], -1), $parts[$i]);
}
$format.= $parts[$i - 1];
return $format;
}
/**
* Convert binary data into bits
*
* bin2hex / hex2bin refer to base-256 encoded data as binary, whilst
* decbin / bindec refer to base-2 encoded data as binary. For the purposes
* of this function, bin refers to base-256 encoded data whilst bits refers
* to base-2 encoded data
*
* @access public
* @param string $x
* @return string
*/
public static function bits2bin($x)
{
/*
// the pure-PHP approach is faster than the GMP approach
if (function_exists('gmp_export')) {
return strlen($x) ? gmp_export(gmp_init($x, 2)) : gmp_init(0);
}
*/
if (preg_match('#[^01]#', $x)) {
throw new \RuntimeException('The only valid characters are 0 and 1');
}
if (!defined('PHP_INT_MIN')) {
define('PHP_INT_MIN', ~PHP_INT_MAX);
}
$length = strlen($x);
if (!$length) {
return '';
}
$block_size = PHP_INT_SIZE << 3;
$pad = $block_size - ($length % $block_size);
if ($pad != $block_size) {
$x = str_repeat('0', $pad) . $x;
}
$parts = str_split($x, $block_size);
$str = '';
foreach ($parts as $part) {
$xor = $part[0] == '1' ? PHP_INT_MIN : 0;
$part[0] = '0';
$str.= pack(
PHP_INT_SIZE == 4 ? 'N' : 'J',
$xor ^ eval('return 0b' . $part . ';')
);
}
return ltrim($str, "\0");
}
/**
* Convert bits to binary data
*
* @access public
* @param string $x
* @return string
*/
public static function bin2bits($x)
{
/*
// the pure-PHP approach is slower than the GMP approach BUT
// i want to the pure-PHP version to be easily unit tested as well
if (function_exists('gmp_import')) {
return gmp_strval(gmp_import($x), 2);
}
*/
$len = strlen($x);
$mod = $len % PHP_INT_SIZE;
if ($mod) {
$x = str_pad($x, $len + PHP_INT_SIZE - $mod, "\0", STR_PAD_LEFT);
}
$bits = '';
if (PHP_INT_SIZE == 4) {
$digits = unpack('N*', $x);
foreach ($digits as $digit) {
$bits.= sprintf('%032b', $digit);
}
} else {
$digits = unpack('J*', $x);
foreach ($digits as $digit) {
$bits.= sprintf('%064b', $digit);
}
}
return ltrim($bits, '0');
}
/**
* Switch Endianness Bit Order
*
* @access public
* @param string $x
* @return string
*/
public static function switchEndianness($x)
{
$r = '';
// from http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith32Bits
for ($i = strlen($x) - 1; $i >= 0; $i--) {
$b = ord($x[$i]);
$p1 = ($b * 0x0802) & 0x22110;
$p2 = ($b * 0x8020) & 0x88440;
$r.= chr(
(($p1 | $p2) * 0x10101) >> 16
);
}
return $r;
}
/**
* Increment the current string
*
* @param string $var
* @return string
* @access public
*/
public static function increment_str(&$var)
{
for ($i = 4; $i <= strlen($var); $i+= 4) {
$temp = substr($var, -$i, 4);
switch ($temp) {
case "\xFF\xFF\xFF\xFF":
$var = substr_replace($var, "\x00\x00\x00\x00", -$i, 4);
break;
case "\x7F\xFF\xFF\xFF":
$var = substr_replace($var, "\x80\x00\x00\x00", -$i, 4);
return $var;
default:
$temp = unpack('Nnum', $temp);
$var = substr_replace($var, pack('N', $temp['num'] + 1), -$i, 4);
return $var;
}
}
$remainder = strlen($var) % 4;
if ($remainder == 0) {
return $var;
}
$temp = unpack('Nnum', str_pad(substr($var, 0, $remainder), 4, "\0", STR_PAD_LEFT));
$temp = substr(pack('N', $temp['num'] + 1), -$remainder);
$var = substr_replace($var, $temp, 0, $remainder);
return $var;
}
/**
* Find whether the type of a variable is string (or could be converted to one)
*
* @param string|object $var
* @return boolean
* @access public
*/
public static function is_stringable($var)
{
return is_string($var) || (is_object($var) && method_exists($var, '__toString'));
}
}
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