ProFTPD < 1.3.5b / 1.3.6x < 1.3.6rc2 weak Diffie-Hellman key

#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(106755);
  script_version("1.2");
  script_cvs_date("Date: 2019/11/08");

  script_cve_id("CVE-2016-3125");
  script_bugtraq_id(84327);

  script_name(english:"ProFTPD < 1.3.5b / 1.3.6x < 1.3.6rc2 weak Diffie-Hellman key");
  script_summary(english:"Checks version of ProFTPD.");

  script_set_attribute(attribute:"synopsis", value:
"The remote FTP server is affected by a Denial of Service
vulnerability.");
  script_set_attribute(attribute:"description", value:
"The remote host is using ProFTPD, a free FTP server for Unix and
Linux.
According to its banner, the version of ProFTPD installed on the
remote host is prior to 1.3.5b or 1.3.6x prior to 1.3.6rc2 
and is affected by an issue in the mod_tls module, which 
might cause a weaker than intended Diffie-Hellman key
to be used.");
  script_set_attribute(attribute:"see_also", value:"http://bugs.proftpd.org/show_bug.cgi?id=4230");
  script_set_attribute(attribute:"solution", value:
"Upgrade to ProFTPD version 1.3.5b / 1.3.6rc2 or later.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:P/I:N/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"vuln_publication_date", value:"2016/03/08");
  script_set_attribute(attribute:"patch_publication_date", value:"2016/03/11");
  script_set_attribute(attribute:"plugin_publication_date", value:"2018/02/12");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:proftpd:proftpd");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"FTP");

  script_copyright(english:"This script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ftp_overflow.nasl", "ftpserver_detect_type_nd_version.nasl");
  script_require_keys("ftp/proftpd", "Settings/ParanoidReport");
  script_require_ports("Services/ftp", 21);

  exit(0);
}

include("audit.inc");
include("ftp_func.inc");
include("global_settings.inc");

if (report_paranoia < 2) audit(AUDIT_PARANOID);

port = get_ftp_port(default: 21, broken:TRUE);

app = "ProFTPD";
banner = get_ftp_banner(port:port);
if (!banner) audit(AUDIT_NO_BANNER, port);
if (app >!< banner) audit(AUDIT_NOT_DETECT, app, port);

matches = pregmatch(string:banner, pattern:"ProFTPD ([0-9a-z.]+) ");
if (isnull(matches)) audit(AUDIT_SERVICE_VER_FAIL, app, port);
version = matches[1];

if (version =~ '^1(\\.3)?$') audit(AUDIT_VER_NOT_GRANULAR, app, version);

if (
  version =~ "^0($|\.)" ||
  version =~ "^1\.[0-2]($|\.)" ||
  version =~ "^1\.3\.[1234]($|[^0-9])" ||
  version =~ "^1\.3\.5(rc[1-9]|a)?($|[^0-9b-z])" ||
  version =~ "^1\.3\.6(rc1)?($|[^0-9a-z])"
)
{
  report =
    '\n  Version source    : ' + chomp(banner) +
    '\n  Installed version : ' + version +
    '\n  Fixed version     : 1.3.5b / 1.3.6rc2\n';
  security_report_v4(severity:SECURITY_WARNING, port:port, extra:report);
  exit(0);
}
else audit(AUDIT_LISTEN_NOT_VULN, app, port, version);