SSL/TLS: HTTP Strict Transport Security (HSTS) Missing

# 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

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.105879");
  script_version("2025-03-21T15:40:43+0000");
  script_tag(name:"cvss_base", value:"0.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:N");
  script_tag(name:"last_modification", value:"2025-03-21 15:40:43 +0000 (Fri, 21 Mar 2025)");
  script_tag(name:"creation_date", value:"2016-08-22 13:07:41 +0200 (Mon, 22 Aug 2016)");
  script_name("SSL/TLS: HTTP Strict Transport Security (HSTS) Missing");
  script_category(ACT_GATHER_INFO);
  script_family("SSL and TLS");
  script_copyright("Copyright (C) 2016 Greenbone AG");
  script_dependencies("gb_hsts_http_detect.nasl");
  script_mandatory_keys("hsts/missing/port");

  script_xref(name:"URL", value:"https://owasp.org/www-project-secure-headers/");
  script_xref(name:"URL", value:"https://owasp.org/www-project-cheat-sheets/cheatsheets/HTTP_Strict_Transport_Security_Cheat_Sheet.html");
  script_xref(name:"URL", value:"https://owasp.org/www-project-secure-headers/#http-strict-transport-security-hsts");
  script_xref(name:"URL", value:"https://tools.ietf.org/html/rfc6797");
  script_xref(name:"URL", value:"https://securityheaders.io/");
  script_xref(name:"URL", value:"https://httpd.apache.org/docs/current/mod/mod_headers.html#header");
  script_xref(name:"URL", value:"https://nginx.org/en/docs/http/ngx_http_headers_module.html#add_header");

  script_tag(name:"summary", value:"The remote web server is not enforcing HTTP Strict Transport
  Security (HSTS).");

  script_tag(name:"solution", value:"Enable HSTS or add / configure the required directives
  correctly following the guides linked in the references.

  Note: Some web servers are not sending headers on specific status codes by default. Please review
  your web server or application configuration to always send these headers on every response
  independently from the status code.

  - Apache: Use 'Header always set' instead of 'Header set'.

  - nginx: Append the 'always' keyword to each 'add_header' directive.

  For different applications or web severs please refer to the related documentation for a similar
  configuration possibility.");

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

  exit(0);
}

if( ! port = get_kb_item( "hsts/missing/port" ) )
  exit( 0 );

max_age_missing = get_kb_item( "hsts/max_age/missing/" + port );
max_age_zero    = get_kb_item( "hsts/max_age/zero/" + port );
sts_banner      = get_kb_item( "hsts/" + port + "/banner" );

if( max_age_missing ) {
  report = "The remote web server is sending a HSTS header but is missing the required 'max-age=' directive.";
  report += '\n\nHSTS-Header:\n\n' + sts_banner;
} else if( max_age_zero ) {
  report = "The remote web server is sending a HSTS header but is defining a 'max-age=0' directive which disables HSTS for this host.";
  report += '\n\nHSTS-Header:\n\n' + sts_banner;
} else {
  banner = get_kb_item( "www/banner/" + port + "/" );

  # Clean-up banner from dynamic data so we don't report differences on the delta report
  pattern = '([Dd]ate\\s*:\\s*|[Ee]xpires=|[Ee]xpires\\s*:\\s*|PHPSESSID=|[Ll]ast-[Mm]odified\\s*:\\s*|[Cc]ontent-[Ll]ength\\s*:\\s*|[Ss]et-[Cc]ookie\\s*:\\s*|[Ee][Tt]ag\\s*:\\s*(W/"|")?|[Ss]ession[Ii]d=)([0-9a-zA-Z :,-;=_%]+)';
  if( eregmatch( pattern:pattern, string:banner ) )
    banner = ereg_replace( string:banner, pattern:pattern, replace:"\1***replaced***" );

  # Content-Security-Policy might have something like this:
  #
  # *snip* default-src 'self'; script-src 'self' 'nonce-<redacted>='; *snip*
  #
  # or just:
  #
  # Content-Security-Policy: object-src 'self'; script-src 'self' 'nonce-<redacted>'
  #
  # Clean-up the banner from this dynamic data as well
  if( banner =~ "Content-Security-Policy\s*:" )
    banner = ereg_replace( string:banner, pattern:"([Cc]ontent-[Ss]ecurity-[Pp]olicy\s*:.+'nonce-)([^']+)(';?)", replace:"\1***replaced***\3" );

  report = "The remote web server is not enforcing HSTS.";
  report += '\n\nHTTP-Banner:\n\n' + chomp( banner );
}

log_message( port:port, data:report );
exit( 0 );