Sudo Heap-Based Buffer Overflow Vulnerability (Baron Samedit) - Active Check

# Copyright (C) 2021 Greenbone Networks GmbH
# 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-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:sudo_project:sudo";

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.117187");
  script_version("2022-08-09T10:11:17+0000");
  script_xref(name:"CISA", value:"Known Exploited Vulnerability (KEV) catalog");
  script_xref(name:"URL", value:"https://www.cisa.gov/known-exploited-vulnerabilities-catalog");
  script_cve_id("CVE-2021-3156");
  script_tag(name:"cvss_base", value:"7.2");
  script_tag(name:"cvss_base_vector", value:"AV:L/AC:L/Au:N/C:C/I:C/A:C");
  script_tag(name:"last_modification", value:"2022-08-09 10:11:17 +0000 (Tue, 09 Aug 2022)");
  script_tag(name:"severity_vector", value:"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2021-07-20 23:15:00 +0000 (Tue, 20 Jul 2021)");
  script_tag(name:"creation_date", value:"2021-01-27 06:47:49 +0000 (Wed, 27 Jan 2021)");
  script_name("Sudo Heap-Based Buffer Overflow Vulnerability (Baron Samedit) - Active Check");
  script_category(ACT_ATTACK);
  script_copyright("Copyright (C) 2021 Greenbone Networks GmbH");
  script_family("Buffer overflow");
  script_dependencies("gb_sudo_ssh_login_detect.nasl", "gb_perl_ssh_login_detect.nasl");
  script_mandatory_keys("sudo/ssh-login/detected", "perl/ssh-login/detected"); # nb: PoC below requires perl to be installed on the target.

  script_xref(name:"URL", value:"https://www.sudo.ws/stable.html#1.9.5p2");
  script_xref(name:"URL", value:"https://blog.qualys.com/vulnerabilities-research/2021/01/26/cve-2021-3156-heap-based-buffer-overflow-in-sudo-baron-samedit");

  script_tag(name:"summary", value:"Sudo is prone to a heap-based buffer overflow dubbed
  'Baron Samedit'.");

  script_tag(name:"vuldetect", value:"Runs a specific SSH command after the login to the target
  which is known to trigger an error message on affected versions of Sudo.");

  script_tag(name:"insight", value:"Sudo is allowing privilege escalation to root via 'sudoedit -s'
  and a command-line argument that ends with a single backslash character.");

  script_tag(name:"affected", value:"All legacy versions from 1.8.2 to 1.8.31p2 and all stable
  versions from 1.9.0 to 1.9.5p1 in their default configuration.");

  script_tag(name:"solution", value:"Update to version 1.9.5p2 or later.");

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

  exit(0);
}

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

if( ! get_app_location( cpe:CPE, port:0, nofork:TRUE ) )
  exit( 0 );

sock = ssh_login_or_reuse_connection();
if( ! sock )
  exit( 0 );

# nb: We're only testing the "sudoedit" within the path as others might be not
# allowing to e.g. get root.

# just exit if we don't have access to the binary...
cmd = "sudoedit --help";
res = ssh_cmd( socket:sock, cmd:cmd, nosu:TRUE );
if( ! res || "usage: sudoedit" >!< res )
  exit( 0 );

# or avoid any false positives if the binary itself is throwing a segmentation fault..
pattern = "(malloc\(\): corrupted top size|Segmentation fault)";
if( egrep( string:res, pattern:pattern, icase:FALSE ) )
  exit( 0 );

# sudoedit -s '\' `perl -e 'print "A" x 65536'`
cmd = "sudoedit -s '\' `perl -e 'print " + '"A"' + " x 65536'`";
res = ssh_cmd( socket:sock, cmd:cmd, nosh:TRUE, nosu:TRUE, return_errors:TRUE, return_linux_errors_only:TRUE, pty:TRUE, clear_buffer:TRUE );
close( sock );

if( egrep( string:res, pattern:pattern, icase:FALSE ) ) {
  report = "Used command: " + cmd + '\n\nResult: ' + res;
  security_message( port:0, data:report );
  exit( 0 );
}

exit( 99 );