TFTP File Detection (Cisco IOS CA) - Active Check

# SPDX-FileCopyrightText: 2005 Corsaire Limited
# 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("1.3.6.1.4.1.25623.1.0.17341");
  script_version("2026-03-17T05:57:28+0000");
  script_tag(name:"last_modification", value:"2026-03-17 05:57:28 +0000 (Tue, 17 Mar 2026)");
  script_tag(name:"creation_date", value:"2005-11-03 14:08:04 +0100 (Thu, 03 Nov 2005)");
  script_tag(name:"cvss_base", value:"5.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:P/I:N/A:N");
  script_name("TFTP File Detection (Cisco IOS CA) - Active Check");
  script_category(ACT_ATTACK);
  script_copyright("Copyright (C) 2005 Corsaire Limited");
  script_family("Remote file access");
  script_dependencies("tftpd_detect.nasl", "tftpd_backdoor.nasl", "global_settings.nasl",
                      "os_detection.nasl");
  script_require_udp_ports("Services/udp/tftp", 69);
  script_mandatory_keys("tftp/detected", "Host/runs_unixoide");
  script_exclude_keys("keys/TARGET_IS_IPV6");

  script_tag(name:"summary", value:"The remote host has a TFTP server installed that is serving one or more
  sensitive Cisco IOS Certificate Authority (CA) files.");

  script_tag(name:"insight", value:"These files potentially include the private key for the CA so should be considered
  extremely sensitive and should not be exposed to unnecessary scrutiny.");

  script_tag(name:"solution", value:"If it is not required, disable the TFTP server. Otherwise restrict access to
  trusted sources only.");

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

  exit(0);
}

if(TARGET_IS_IPV6())
  exit(0);

include("tftp.inc");
include("port_service_func.inc");

port = service_get_port(default:69, proto:"tftp", ipproto:"udp");

if(!tftp_has_reliable_get(port:port))
  exit(0);

postfix_list = make_list(".pub", ".crl", ".prv", ".ser", "#6101CA.cer", ".p12");

for( i = 1; i < 10; i++) {

  file_name = raw_string(ord(i), '.cnm');

  if(request_data = tftp_get(port:port, path:file_name)) {

    ca_name = eregmatch(string:request_data, pattern:'subjectname_str = cn=(.+),ou=');
    if(ca_name[1]) {
      detected_files = raw_string(detected_files, file_name, "\n");
      foreach file_postfix(postfix_list) {
        file_name = raw_string(ca_name[1], file_postfix);
        if(tftp_get(port:port, path:file_name)) {
          detected_files += file_name + '\n';
        }
      }
      break;
    }
  }
}

if(detected_files) {
  report = 'The filenames detected are:\n\n' + detected_files;
  security_message(port:port, data:report, proto:"udp");
  exit(0);
}

exit(99);