基於長密碼的PHP函數驗證漏洞學習（Long Password Denial of Service (DoS)）

啥都不說，乾貨直接上源碼。

<?php

/*
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 */

//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";
    }   
    

//關鍵區域注意hasher定義類這塊代碼

$hashed_pass = $pass_hash->HashPassword($pass);//注意此處函數，由於沒有限制密碼長度，導致系統運行耗時。

輸出結果測試：

"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.