Asterisk Authentication Bypass Vulnerability (AST-2016-009)

# SPDX-FileCopyrightText: 2016 Greenbone AG
# 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

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

if (description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.106462");
  script_version("2023-12-20T12:22:41+0000");
  script_cve_id("CVE-2016-9938");
  script_tag(name:"last_modification", value:"2023-12-20 12:22:41 +0000 (Wed, 20 Dec 2023)");
  script_tag(name:"creation_date", value:"2016-12-09 14:10:48 +0700 (Fri, 09 Dec 2016)");
  script_tag(name:"cvss_base", value:"5.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:P/A:N");
  script_tag(name:"severity_vector", value:"CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2017-07-27 01:29:00 +0000 (Thu, 27 Jul 2017)");

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

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

  script_name("Asterisk Authentication Bypass Vulnerability (AST-2016-009)");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2016 Greenbone AG");
  script_family("General");
  script_dependencies("gb_digium_asterisk_sip_detect.nasl");
  script_mandatory_keys("digium/asterisk/detected");

  script_tag(name:"summary", value:"Asterisk is prone to an authentication bypass vulnerability.");

  script_tag(name:"vuldetect", value:"Checks if a vulnerable version is present on the target host.");

  script_tag(name:"insight", value:"The chan_sip channel driver has a liberal definition for
  whitespace when attempting to strip the content between a SIP header name and a colon character.
  Headers such as 'Contact\x01:' will be seen as a valid Contact header.

  This mostly does not pose a problem until Asterisk is placed in tandem with an authenticating SIP
  proxy. In such a case, a crafty combination of valid and invalid To headers can cause a proxy to
  allow an INVITE request into Asterisk without authentication since it believes the request is an
  in-dialog request. However, because of the bug described above, the request will look like an
  out-of-dialog request to Asterisk. Asterisk will then process the request as a new call. The result
  is that Asterisk can process calls from unvetted sources without any authentication.

  If you do not use a proxy for authentication, or if your proxy is dialog-aware, or if you use
  chan_pjsip instead of chan_sip, then this issue does not affect you.");

  script_tag(name:"impact", value:"An authenticated remote attacker may make calls without any
  authentication.");

  script_tag(name:"affected", value:"Asterisk Open Source versions 11.x, 13.x, 14.x and Certified
  Asterisk versions 11.6 and 13.8.");

  script_tag(name:"solution", value:"Update to version 11.25.1, 13.13.1, 14.2.1, 11.6-cert16,
  13.8-cert4 or later.");

  script_xref(name:"URL", value:"http://downloads.asterisk.org/pub/security/AST-2016-009.html");
  script_xref(name:"URL", value:"http://www.securityfocus.com/bid/94789");

  exit(0);
}

include("host_details.inc");
include("revisions-lib.inc");
include("version_func.inc");

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

if (!version = get_app_version(cpe: CPE, port: port))
  exit(0);

if (version =~ "^11\.") {
  if (version =~ "^11\.6cert") {
    if (revcomp(a: version, b: "11.6cert16") < 0) {
      report = report_fixed_ver(installed_version: version, fixed_version: "11.6-cert16");
      security_message(port: port, data: report, proto: "udp");
      exit(0);
    }
  }
  else {
    if (version_is_less(version: version, test_version: "11.25.1")) {
      report = report_fixed_ver(installed_version: version, fixed_version: "11.25.1");
      security_message(port: port, data: report, proto: "udp");
      exit(0);
    }
  }
}

if (version =~ "^13\.") {
  if (version =~ "^13\.8cert") {
    if (revcomp(a: version, b: "13.8cert4") < 0) {
      report = report_fixed_ver(installed_version: version, fixed_version: "13.8-cert4");
      security_message(port: port, data: report, proto: "udp");
      exit(0);
    }
  }
  else {
    if (version_is_less(version: version, test_version: "13.13.1")) {
      report = report_fixed_ver(installed_version: version, fixed_version: "13.13.1");
      security_message(port: port, data: report, proto: "udp");
      exit(0);
    }
  }
}

if (version =~ "^14\.") {
  if (version_is_less(version: version, test_version: "14.2.1")) {
    report = report_fixed_ver(installed_version: version, fixed_version: "14.2.1");
    security_message(port: port, data: report, proto: "udp");
    exit(0);
  }
}

exit(0);