[置顶] 基于长密码的PHP函数验证漏洞学习（Long Password Denial of Service (DoS)）

<?php

/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/

//demo 0x001

//require_once 'phpass.php';

set_time_limit(0);
ignore_user_abort(true);

class PasswordHash
{

var $itoa64;
var $iteration_count_log2;
var $portable_hashes;
var $random_state;

function PasswordHash($iteration_count_log2, $portable_hashes)
{
$this->itoa64 = './0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
if ($iteration_count_log2 < 4 || $iteration_count_log2 > 31)
$iteration_count_log2 = 8;
$this->iteration_count_log2 = $iteration_count_log2;

$this->portable_hashes = $portable_hashes;

$this->random_state = microtime();
if (function_exists('getmypid'))
$this->random_state .= getmypid();
}

function get_random_bytes($count)
{
$output = '';
if (is_readable('/dev/urandom') &&
($fh = @fopen('/dev/urandom', 'rb')))
{
$output = fread($fh, $count);
fclose($fh);
}

if (strlen($output) < $count)
{
$output = '';
for ($i = 0; $i < $count; $i += 16)
{
$this->random_state = md5(microtime() . $this->random_state);
$output .=
pack('H*', md5($this->random_state));
}
$output = substr($output, 0, $count);
}
return $output;
}

function encode64($input, $count)
{
$output = '';
$i = 0;
do
{
$value = ord($input[$i++]);
$output .= $this->itoa64[$value & 0x3f];
if ($i < $count)
$value |= ord($input[$i]) << 8;
$output .= $this->itoa64[($value >> 6) & 0x3f];
if ($i++ >= $count)
break;
if ($i < $count)
$value |= ord($input[$i]) << 16;
$output .= $this->itoa64[($value >> 12) & 0x3f];
if ($i++ >= $count)
break;
$output .= $this->itoa64[($value >> 18) & 0x3f];
} while ($i < $count);

return $output;
}

function gensalt_private($input)
{
$output = '$P$';
$output .= $this->itoa64[min($this->iteration_count_log2 +
((PHP_VERSION >= '5') ? 5 : 3), 30)];
$output .= $this->encode64($input, 6);

return $output;
}

function crypt_private($password, $setting)
{
$output = '*0';
if (substr($setting, 0, 2) == $output)
$output = '*1';

$id = substr($setting, 0, 3);
# We use "$P$", phpBB3 uses "$H$" for the same thing
if ($id != '$P$' && $id != '$H$')
return $output;

$count_log2 = strpos($this->itoa64, $setting[3]);
if ($count_log2 < 7 || $count_log2 > 30)
return $output;

$count = 1 << $count_log2;

$salt = substr($setting, 4, 8);
if (strlen($salt) != 8)
return $output;

# We're kind of forced to use MD5 here since it's the only
# cryptographic primitive available in all versions of PHP
# currently in use.  To implement our own low-level crypto
# in PHP would result in much worse performance and
# consequently in lower iteration counts and hashes that are
# quicker to crack (by non-PHP code).
if (PHP_VERSION >= '5')
{
$hash = md5($salt . $password, TRUE);
do
{
$hash = md5($hash . $password, TRUE);
} while (--$count);
} else
{
$hash = pack('H*', md5($salt . $password));
do
{
$hash = pack('H*', md5($hash . $password));
} while (--$count);
}

$output = substr($setting, 0, 12);
$output .= $this->encode64($hash, 16);

return $output;
}

function gensalt_extended($input)
{
$count_log2 = min($this->iteration_count_log2 + 8, 24);
# This should be odd to not reveal weak DES keys, and the
# maximum valid value is (2**24 - 1) which is odd anyway.
$count = (1 << $count_log2) - 1;

$output = '_';
$output .= $this->itoa64[$count & 0x3f];
$output .= $this->itoa64[($count >> 6) & 0x3f];
$output .= $this->itoa64[($count >> 12) & 0x3f];
$output .= $this->itoa64[($count >> 18) & 0x3f];

$output .= $this->encode64($input, 3);

return $output;
}

function gensalt_blowfish($input)
{
# This one needs to use a different order of characters and a
# different encoding scheme from the one in encode64() above.
# We care because the last character in our encoded string will
# only represent 2 bits.  While two known implementations of
# bcrypt will happily accept and correct a salt string which
# has the 4 unused bits set to non-zero, we do not want to take
# chances and we also do not want to waste an additional byte
# of entropy.
$itoa64 = './ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';

$output = '$2a$';
$output .= chr(ord('0') + $this->iteration_count_log2 / 10);
$output .= chr(ord('0') + $this->iteration_count_log2 % 10);
$output .= '$';

$i = 0;
do
{
$c1 = ord($input[$i++]);
$output .= $itoa64[$c1 >> 2];
$c1 = ($c1 & 0x03) << 4;
if ($i >= 16)
{
$output .= $itoa64[$c1];
break;
}

$c2 = ord($input[$i++]);
$c1 |= $c2 >> 4;
$output .= $itoa64[$c1];
$c1 = ($c2 & 0x0f) << 2;

$c2 = ord($input[$i++]);
$c1 |= $c2 >> 6;
$output .= $itoa64[$c1];
$output .= $itoa64[$c2 & 0x3f];
} while (1);

return $output;
}

function HashPassword($password)
{
$random = '';

if (CRYPT_BLOWFISH == 1 && !$this->portable_hashes)
{
$random = $this->get_random_bytes(16);
$hash = crypt($password, $this->gensalt_blowfish($random));
if (strlen($hash) == 60)
return $hash;
}

if (CRYPT_EXT_DES == 1 && !$this->portable_hashes)
{
if (strlen($random) < 3)
$random = $this->get_random_bytes(3);
$hash = crypt($password, $this->gensalt_extended($random));
if (strlen($hash) == 20)
return $hash;
}
if (strlen($random) < 6)
$random = $this->get_random_bytes(6);
$hash = $this->crypt_private($password, $this->gensalt_private($random));
if (strlen($hash) == 34)
return $hash;

# Returning '*' on error is safe here, but would _not_ be safe
# in a crypt(3)-like function used _both_ for generating new
# hashes and for validating passwords against existing hashes.
return '*';
}

function CheckPassword($password, $stored_hash)
{
$hash = $this->crypt_private($password, $stored_hash);
if ($hash[0] == '*')
$hash = crypt($password, $stored_hash);

return $hash == $stored_hash;
}

}

//Long Password Denial of Service (DoS)

//denial-of-service-responsible-disclosure
class hasher
{

function __construct($pass)
{

$pass_hash = new PasswordHash(8, TRUE);
$hashed_pass = $pass_hash->HashPassword($pass);
}

}

$length = array("1", "10", "50", "100", "500", "1000", "5000", "10000", "50000", "100000", "200000",
"300000", "400000", "500000", "600000", "700000", "800000", "900000", "1000000",
"2000000", "3000000","4000000", "5000000", "6000000", "7000000", "8000000", "9000000");

foreach ($length as $value)
{
$valor = str_repeat("A", $value);
$time_start = microtime(true);
$hashgen = new hasher($valor);//in this case the PHP script not control the input length:
echo 'Size in character(s): ' . $value;
echo ' Total execution time in seconds: ' . (microtime(true) - $time_start);
print "\n";
}

$hashed_pass = $pass_hash->HashPassword($pass);//注意此处函数，由于没有限制密码长度，导致系统运行耗时。

"php.exe" "TimingAttack.php"

Size in character(s): 1 Total execution time in seconds: 0.015599966049194
Size in character(s): 10 Total execution time in seconds: 0
Size in character(s): 50 Total execution time in seconds: 0.015599966049194
Size in character(s): 100 Total execution time in seconds: 0
Size in character(s): 500 Total execution time in seconds: 0.015599966049194
Size in character(s): 1000 Total execution time in seconds: 0.031200170516968
Size in character(s): 5000 Total execution time in seconds: 0.12480092048645
Size in character(s): 10000 Total execution time in seconds: 0.23399996757507
Size in character(s): 50000 Total execution time in seconds: 1.1700019836426
Size in character(s): 100000 Total execution time in seconds: 2.2776041030884
Size in character(s): 200000 Total execution time in seconds: 4.1808068752289
Size in character(s): 300000 Total execution time in seconds: 9.656417131424
Size in character(s): 400000 Total execution time in seconds: 14.149224996567
Size in character(s): 500000 Total execution time in seconds: 17.425230979919
Size in character(s): 600000 Total execution time in seconds: 19.094433069229
Size in character(s): 700000 Total execution time in seconds: 23.010040998459
Size in character(s): 800000 Total execution time in seconds: 24.070841789246
Size in character(s): 900000 Total execution time in seconds: 28.298449993134
Size in character(s): 1000000 Total execution time in seconds: 33.259258031845
Size in character(s): 2000000 Total execution time in seconds: 67.298518180847
Size in character(s): 3000000 Total execution time in seconds: 101.29097795486
Size in character(s): 4000000 Total execution time in seconds: 113.45899987221
Size in character(s): 5000000 Total execution time in seconds: 135.59543800354
Size in character(s): 6000000 Total execution time in seconds: 154.45587110519
Size in character(s): 7000000 Total execution time in seconds: 203.9391579628
Size in character(s): 8000000 Total execution time in seconds: 234.54641199112
Size in character(s): 9000000 Total execution time in seconds: 265.59046697617
Done.