Mail relaying (thorough test)

# SPDX-FileCopyrightText: 2003 Michel Arboi
# Some text descriptions might be excerpted from (a) referenced
# source(s), and are Copyright (C) by the respective right holder(s).
#
# SPDX-License-Identifier: GPL-2.0-only

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.11852");
  script_version("2023-11-03T16:10:08+0000");
  script_tag(name:"last_modification", value:"2023-11-03 16:10:08 +0000 (Fri, 03 Nov 2023)");
  script_tag(name:"creation_date", value:"2005-11-03 14:08:04 +0100 (Thu, 03 Nov 2005)");
  script_tag(name:"cvss_base", value:"10.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:C/I:C/A:C");
  script_tag(name:"severity_vector", value:"CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2019-07-30 20:58:00 +0000 (Tue, 30 Jul 2019)");
  script_cve_id("CVE-1999-0512", "CVE-2002-1278", "CVE-2003-0285", "CVE-2003-0316", "CVE-2005-0431",
                "CVE-2005-2857", "CVE-2006-0977", "CVE-2019-14403");
  script_name("Mail relaying (thorough test)");
  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2003 Michel Arboi");
  script_family("SMTP problems");
  script_dependencies("smtpserver_detect.nasl", "check_smtp_helo.nasl", "smtp_relay.nasl", "smtp_settings.nasl", "global_settings.nasl");
  script_require_ports("Services/smtp", 25, 465, 587);
  script_mandatory_keys("smtp/banner/available", "keys/is_public_addr");

  script_tag(name:"summary", value:"The remote SMTP server appears to be insufficiently protected
  against mail relaying.");

  script_tag(name:"vuldetect", value:"Sends multiple crafted SMTP requests and checks the responses.

  Note:

  This VT is only reporting a vulnerability if the target system / service is accessible from a
  public WAN (Internet) / public LAN.

  A configuration option 'Network type' to define if a scanned network should be seen as a public
  LAN can be found in the preferences of the following VT:

  Global variable settings (OID: 1.3.6.1.4.1.25623.1.0.12288)");

  script_tag(name:"impact", value:"This means that spammers might be able to use your mail server to
  send their mails to the world.");

  script_tag(name:"solution", value:"Upgrade your software or improve the configuration so that your
  SMTP server cannot be used as a relay any more.");

  script_tag(name:"qod_type", value:"remote_active");
  script_tag(name:"solution_type", value:"VendorFix");

  exit(0);
}

include("smtp_func.inc");
include("misc_func.inc");
include("port_service_func.inc");
include("network_func.inc");

if(!is_public_addr())
  exit(0);

port = smtp_get_port(default:25);

# No use to try "advanced" tests if it is a wide open relay
if(get_kb_item("smtp/" + port + "/spam"))
  exit(0);

if(get_kb_item("smtp/" + port + "/qmail/detected"))
  exit(0);

if(smtp_get_is_marked_wrapped(port:port))
  exit(0);

helo_name = smtp_get_helo_from_kb(port:port);
soc = smtp_open(port:port, data:helo_name, send_helo:TRUE, code:"250");
if(!soc)
  exit(0);

vtstrings = get_vt_strings();
domain = get_3rdparty_domain();
dest_name = get_host_name();
dest_ip = get_host_ip();

t1 = strcat('nobody@', domain);
f1 = strcat(vtstrings["lowercase"], '@', dest_name);
f2 = strcat(vtstrings["lowercase"], '@[', dest_ip, ']');

i = 0;
from_l[i] = strcat("nobody@", domain);
to_l[i] = t1;
i++;
from_l[i] = strcat(vtstrings["lowercase"], "@", rand_str(), ".", domain);
to_l[i] = t1;
i++;
from_l[i] = vtstrings["lowercase"] + "@localhost";
to_l[i] = t1;
i++;
from_l[i] = vtstrings["lowercase"];
to_l[i] = t1;
i++;
from_l[i] = "";
to_l[i] = t1;
i++;
from_l[i] = "";
to_l[i] = t1;
i++;
from_l[i] = strcat(vtstrings["lowercase"], "@", dest_name);
to_l[i] = t1;
i++;
from_l[i] = strcat(vtstrings["lowercase"], "@[", dest_ip, "]");
to_l[i] = t1;
i++;
from_l[i] = strcat(vtstrings["lowercase"], "@", dest_name);
to_l[i] = strcat("nobody%", domain, "@", dest_name);
i++;
from_l[i] = strcat(vtstrings["lowercase"], "@", dest_name);
to_l[i] = strcat("nobody%", domain, "@[", dest_ip, "]");
i++;
from_l[i] = strcat(vtstrings["lowercase"], "@", dest_name);
to_l[i] = strcat('nobody@', domain, '@', dest_name);
i++;
from_l[i] = strcat(vtstrings["lowercase"], "@", dest_name);
to_l[i] = strcat('"nobody@', domain, '"@[', dest_ip, ']');
i++;
from_l[i] = f1;
to_l[i] = strcat('nobody@', domain, '@[', dest_ip, ']');
i++;
from_l[i] = f2;
to_l[i] = strcat('@', dest_name, ':nobody@', domain);
i++;
from_l[i] = f1;
to_l[i] = strcat('@[', dest_ip, ']:nobody@', domain);
i++;
from_l[i] = f1;
to_l[i] = strcat(domain, '!nobody@[', dest_ip, ']');
i++;
from_l[i] = strcat('postmaster@', dest_name);
to_l[i] = t1;
i++;

for(i = 0; soc && (from_l[i] || to_l[i]); i++) {

  mf = strcat('MAIL FROM: <', from_l[i], '>\r\n');
  send(socket:soc, data:mf);
  l = smtp_recv_line(socket:soc);
  if(! l || l =~ '^5[0-9]{2}') {
    smtp_close(socket:soc, check_data:l);
    soc = smtp_open(port:port, data:helo_name, send_helo:TRUE, code:"250");
  } else {
    mfres = l;
    rt = strcat('RCPT TO: <', to_l[i], '>\r\n');
    send(socket:soc, data:rt);
    l = smtp_recv_line(socket:soc, code:"2[0-9]{2}");
    if(l) {
      rtres = l;
      data = string("data\r\n");
      send(socket:soc, data:data);
      l = smtp_recv_line(socket:soc, code:"3[0-9]{2}");
      if(l) {
        datares = l;
        dc = string(vtstrings["default"], "-Relay-Test\r\n.\r\n");
        send(socket:soc, data:dc);
        l = smtp_recv_line(socket:soc, code:"250");
        if(l) {
          rep  = 'Request: ' + chomp( mf );
          rep += '\nAnswer:  ' + chomp( mfres );
          rep += '\nRequest: ' + chomp( rt );
          rep += '\nAnswer:  ' + chomp( rtres );
          rep += '\nRequest: ' + chomp( data );
          rep += '\nAnswer:  ' + chomp( datares );
          rep += '\nRequest: ' + chomp( dc );
          rep += '\nAnswer:  ' + chomp( l );
          smtp_close(socket:soc, check_data:l);
          break;
        }
      }
    }

    smtp_close(socket:soc, check_data:l);
    soc = smtp_open(port:port, data:helo_name, send_helo:TRUE, code:"250");
  }
}

if(rep) {
  report = 'The scanner was able to relay mail by sending the following sequences:\n\n' + rep;
  security_message(port:port, data:report);
  exit(0);
}

exit(99);