Fake FTP server accepts a bad sequence of commands

# OpenVAS Vulnerability Test
# $Id: ftpd_bad_sequence.nasl 4218 2016-10-05 14:20:48Z teissa $
# Description: Fake FTP server accepts a bad sequence of commands
#
# Authors:
# Michel Arboi <[email protected]>
#
# Copyright:
# Copyright (C) 2008 Michel Arboi
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2,
# as published by the Free Software Foundation
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
#

tag_insight = "The remote server advertises itself as being a a FTP server, but it 
accepts commands sent in bad order, which indicates that it may be a 
backdoor or a proxy. 

Further FTP tests on this port will be disabled to avoid false alerts.";
tag_summary = "The remote FTP service accepts commands in any order.";

if(description)
{
 script_id(80063);;
 script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:N");
 script_tag(name:"qod_type", value:"remote_banner_unreliable");
 script_version("$Revision: 4218 $");
 script_tag(name:"last_modification", value:"$Date: 2016-10-05 16:20:48 +0200 (Wed, 05 Oct 2016) $");
 script_tag(name:"creation_date", value:"2008-10-24 23:33:44 +0200 (Fri, 24 Oct 2008)");
 script_tag(name:"cvss_base", value:"0.0");
 
 script_name( "Fake FTP server accepts a bad sequence of commands");
 script_category(ACT_GATHER_INFO);
 script_family( "FTP");
 script_copyright("This script is Copyright (C) 2008 Michel Arboi");

 script_dependencies("find_service_3digits.nasl", "logins.nasl", "ftpd_no_cmd.nasl");
 script_require_ports("Services/ftp", 21);
 script_tag(name : "insight" , value : tag_insight);
 script_tag(name : "summary" , value : tag_summary);
 exit(0);
}

#
include('global_settings.inc');
include('misc_func.inc');
include('ftp_func.inc');

function test(soc)
{
 local_var	r, score;
 score = 0;
 r = ftp_recv_line(socket: soc, retry: 2);
 if (! r)
 {
  debug_print('No FTP welcome banner on port ', port, '\n');
## set_kb_item(name: 'ftp/'+port+'/broken', value: TRUE);
  set_kb_item(name: 'ftp/'+port+'/no_banner', value: TRUE);
  return NULL;
 }
 debug_print(level: 2, 'Banner = ', r);

 if (r =~ '^[45][0-9][0-9] ' || 
     match(string: r, pattern: 'Access denied*', icase: 1))
 {
   debug_print('FTP server on port ', port, ' is closed\n');
   set_kb_item(name: 'ftp/'+port+'/denied', value: TRUE);
   return NULL;
  }

 send(socket: soc, data: 'PASS '+rand_str()+'\r\n');
 r = ftp_recv_line(socket: soc, retry: 2);
 if (r =~ '^230[ -]') # USER logged in
 {
  debug_print('PASS accepted without USER\n');
  set_kb_item(name: 'ftp/'+port+'/broken', value: TRUE);
  score ++;
 }

 send(socket: soc, data: 'USER '+rand_str()+'\r\n');
 r = ftp_recv_line(socket: soc, retry: 2);
 if (r !~ '^331[ -]') return score;

 send(socket: soc, data: 'QUIT\r\n');
 r = ftp_recv_line(socket: soc, retry: 2);
 if (! r) return score;
 send(socket: soc, data: 'QUIT\r\n');
 r2 = ftp_recv_line(socket: soc, retry: 2);
 if (r =~ '^221[ -]' && r2 =~ '^221[ -]')
 {
  debug_print('QUIT accepted twice\n');
  score ++;
 }
 return score;
}

port = get_kb_item("Services/ftp");
if (! port) port = 21; 

if (! get_port_state(port)) exit(0);


soc = open_sock_tcp(port);
if (! soc) exit(0);

score = test(soc: soc);

if ( score >= 1 )
{
 log_message(port: port);
 set_kb_item(name: 'ftp/'+port+'/broken', value: TRUE);
}

ftp_close(socket: soc);