Asterisk PBX SIP Service Guest Access Enabled

# Copyright (C) 2008 Ferdy Riphagen
# 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-or-later
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# 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.

CPE = "cpe:/a:digium:asterisk";

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.9999993");
  script_version("2023-12-19T05:05:25+0000");
  script_tag(name:"last_modification", value:"2023-12-19 05:05:25 +0000 (Tue, 19 Dec 2023)");
  script_tag(name:"creation_date", value:"2008-08-22 16:09:14 +0200 (Fri, 22 Aug 2008)");
  script_tag(name:"cvss_base", value:"3.5");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:M/Au:S/C:N/I:P/A:N");

  script_tag(name:"qod_type", value:"remote_vul");

  script_tag(name:"solution_type", value:"Mitigation");

  script_name("Asterisk PBX SIP Service Guest Access Enabled");

  script_category(ACT_GATHER_INFO);

  script_copyright("Copyright (C) 2008 Ferdy Riphagen");
  script_family("General");
  script_dependencies("gb_digium_asterisk_sip_detect.nasl", "global_settings.nasl");
  script_mandatory_keys("digium/asterisk/detected");
  script_exclude_keys("keys/islocalhost");

  script_tag(name:"summary", value:"Asterisk PBX SIP service guest access is enabled.");

  script_tag(name:"vuldetect", value:"Sends a crafted SIP request and checks the response.");

  script_tag(name:"insight", value:"The SIP service is accepting SIP peers to use the proxy server
  as guest users. Unauthenticated users can use the proxy without supplying the required
  'more secure' authentication.

  Guest access is enabled by default if 'allowguest=no' is not set in 'sip.conf'. Guest peers use
  the context defined under the general section and the restrictions set in the Asterisk config
  files.");

  script_tag(name:"solution", value:"If guest access is not needed, disable it by setting
  'allowguest=no' in the sip.conf file.");

  script_xref(name:"URL", value:"http://www.voip-info.org/wiki/index.php?page=Asterisk+sip+allowguest");

  exit(0);
}

include("host_details.inc");
include("misc_func.inc");
include("sip.inc");

if( islocalhost() )
  exit( 0 );

if( ! port = get_app_port( cpe:CPE ) )
  exit( 0 );

if( ! infos = get_app_location_and_proto( cpe:CPE, port:port ) )
  exit( 0 );

proto = infos["proto"];

vt_strings = get_vt_strings();

rpeer = string( "NotExistingPeer", rand() %900 +100, "@" );
lpeer = string( vt_strings["default"], rand() %900 +100, "@" );

invite = string(
  "INVITE sip:", rpeer, get_host_name(), " SIP/2.0", "\r\n",
  "Via: SIP/2.0/", toupper( proto ), " ", this_host(), ":", port, "\r\n",
  "To: <sip:", rpeer, get_host_name(), ":", port, ">\r\n",
  "From: <sip:", lpeer, this_host(), ":", port, ">\r\n",
  "Call-ID: ", rand(), "\r\n",
  "CSeq: ", rand(), " INVITE\r\n",
  "Contact: <sip:", lpeer, this_host(), ">\r\n",
  "Content-Length: 0\r\n\r\n");
res = sip_send_recv( port:port, data:invite, proto:proto );
if( ! res )
  exit( 0 );

if( "SIP/2.0 404 Not Found" >< res || "SIP/2.0 100 Trying" >< res ) {
  set_kb_item( name:"sip/guest_access/" + port + "/" + proto, value:TRUE );
  security_message( port:port, proto:proto );
  exit( 0 );
}

exit( 99 );