AVM FRITZ!Box Firmware Signature Bypass

# SPDX-FileCopyrightText: 2018 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:/o:avm:fritz%21_os";

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.108462");
  script_version("2023-07-20T05:05:17+0000");
  script_cve_id("CVE-2014-8872");
  script_name("AVM FRITZ!Box Firmware Signature Bypass");
  script_tag(name:"cvss_base", value:"9.3");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:M/Au:N/C:C/I:C/A:C");
  script_tag(name:"last_modification", value:"2023-07-20 05:05:17 +0000 (Thu, 20 Jul 2023)");
  script_tag(name:"severity_vector", value:"CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2018-10-09 19:54:00 +0000 (Tue, 09 Oct 2018)");
  script_tag(name:"creation_date", value:"2018-09-16 13:38:48 +0200 (Sun, 16 Sep 2018)");
  script_category(ACT_GATHER_INFO);
  script_family("General");
  script_copyright("Copyright (C) 2018 Greenbone AG");
  script_dependencies("gb_avm_fritz_box_detect.nasl");
  script_mandatory_keys("avm/fritz/model", "avm/fritz/firmware_version");

  script_xref(name:"URL", value:"http://seclists.org/fulldisclosure/2015/Jan/86");
  script_xref(name:"URL", value:"http://packetstormsecurity.com/files/130040/AVM-FRITZ-Box-Firmware-Signature-Bypass.html");

  script_tag(name:"summary", value:"Multiple AVM FRITZ!Box devices are using an improper verification of cryptographic signatures.");

  script_tag(name:"insight", value:"The signature check of FRITZ!Box firmware images is flawed. Malicious
  code can be injected into firmware images without breaking the RSA signature.");

  script_tag(name:"impact", value:"The code will be executed either if a manipulated firmware
  image is uploaded by the victim or if the victim confirms an update on the webinterface during
  a MITM attack.");

  script_tag(name:"vuldetect", value:"Check the AVM FRITZ!OS version.");

  script_tag(name:"solution", value:"Updates are available. Please see the references or the script output
  on the available updates for the matching model.");

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

  exit(0);
}

include("version_func.inc");
include("host_details.inc");

if( ! fw_version = get_app_version( cpe:CPE, nofork:TRUE ) ) exit( 0 );
if( ! model = get_kb_item( "avm/fritz/model" ) ) exit( 0 );

# nb: https://seclists.org/fulldisclosure/2015/Jan/86 has a list
# of affected / fixed versions. The list is a bit messy but the
# array above should map the list as good as possible based on
# the provided info.
fixes = make_array("7490", "5.50#-#6.19#-#6.20",
                   "7390", "5.50#-#6.19#-#6.20",
                   "7270 v3", "5.50#-#6.04#-#6.05",
                   "7270 v2", "5.50#-#6.04#-#6.05",
                   "7270 v1","5.50#-#6.04#-#6.05",
                   "7240", "5.50#-#6.04#-#6.05",
                   "6810 LTE", "5.22#-#6.19#-#6.20",
                   "6840 LTE", "5.23#-#6.19#-#6.20");

if( ! fixes[model] ) exit( 99 );
range = fixes[model];
range = split( range, sep:"#-#", keep:FALSE );
if( max_index( range ) != 3 ) exit( 0 );
start = range[0];
end   = range[1];
patch = range[2];

if( version_in_range( version:fw_version, test_version:start, test_version2:end ) ) {
  report  = 'Model:              ' + model + '\n';
  report += 'Installed Firmware: ' + fw_version + '\n';
  report += 'Fixed Firmware:     ' + patch;
  security_message( port:0, data:report );
  exit( 0 );
}

exit( 99 );