Disable IP Forwarding

# SPDX-FileCopyrightText: 2025 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

# ------------------------------------------------------------------
# METADATA
# ------------------------------------------------------------------

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.130335");
  script_version("2025-11-21T05:40:28+0000");
  script_tag(name:"last_modification", value:"2025-11-21 05:40:28 +0000 (Fri, 21 Nov 2025)");
  script_tag(name:"creation_date", value:"2025-05-07 11:44:20 +0000 (Wed, 07 May 2025)");
  script_tag(name:"cvss_base", value:"0.0");
  script_tag(name:"cvss_base_vector", value:"AV:L/AC:H/Au:S/C:N/I:N/A:N");
  script_tag(name:"qod", value:"97");

  script_name("Disable IP Forwarding");

  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2025 Greenbone AG");
  script_family("Policy");
  script_dependencies("compliance_tests.nasl", "compliance_os_check.nasl");

  script_mandatory_keys("Compliance/Launch", "policy/ssh/login/euleros_eulerosvirtual_openeuler_hce");

  script_xref(name:"Policy", value:"EulerOS Baseline: openEuler Security Configuration Baseline (v1.0.0): 3. Running and Services: 3.5 Kernel: 3.5.12 Disable IP Forwarding (Requirement)");
  script_xref(name:"Policy", value:"EulerOS Virtual: openEuler Security Configuration Baseline (v1.0.0): 3. Running and Services: 3.5 Kernel: 3.5.12 Disable IP Forwarding (Requirement)");
  script_xref(name:"Policy", value:"HCE Linux (Huawei Cloud EulerOS): openEuler Security Configuration Baseline (v1.0.0): 3. Running and Services: 3.5 Kernel: 3.5.12 Disable IP Forwarding (Requirement)");
  script_xref(name:"Policy", value:"openEuler Baseline: openEuler Security Configuration Baseline (v1.0.0): 3. Running and Services: 3.5 Kernel: 3.5.12 Disable IP Forwarding (Requirement)");

  script_tag(name:"summary", value:"If a node does not function as a gateway server, disable the IP
forwarding function. Otherwise, attackers can use the node as a router.

In the container scenario, if network packets need to be forwarded through the host, IP forwarding
is allowed.");

  exit(0);
}

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

title = "Disable IP Forwarding";

solution = "Run the following commands to disable IP forwarding and modify the configuration files:

# grep -Els <quote>^\\s*net\\.ipv4\\.ip_forward\\s*=\\s*1<quote> /etc/sysctl.conf /etc/sysctl.d/*.conf
/usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf <pipe> while read filename<semicolon> do sed -ri
<quote>s/^\\s*(net\\.ipv4\\.ip_forward\\s*)(=)(\\s*\\S+\\b).*$/# *REMOVED* \\1/<quote> $filename<semicolon>
done<semicolon> sysctl -w net.ipv4.ip_forward=0<semicolon> sysctl -w net.ipv4.route.flush=1

# grep -Els <quote>^\\s*net\\.ipv6\\.conf\\.all\\.forwarding\\s*=\\s*1<quote> /etc/sysctl.conf /etc/sysctl.d/*.conf
/usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf <pipe> while read filename<semicolon> do sed -ri
<quote>s/^\\s*(net\\.ipv6\\.conf\\.all\\.forwarding\\s*)(=)(\\s*\\S+\\b).*$/# *REMOVED* \\1/<quote> $filename<semicolon>
done<semicolon> sysctl -w net.ipv6.conf.all.forwarding=0<semicolon> sysctl -w net.ipv6.route.flush=1";

check_type = "SSH_Cmd";

action = '1. Run the command in the terminal:
# sysctl net.ipv4.ip_forward

2. Run the command in the terminal:
# grep -E -s "^\\s*net\\.ipv4\\.ip_forward\\s*=\\s*1" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf

3. Run the command in the terminal:
# sysctl net.ipv6.conf.all.forwarding

4. Run the command in the terminal:
# grep -E -s "^\\s*net\\.ipv6\\.conf\\.all\\.forwarding\\s*=\\s*1" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf';

expected_value = '1. The output should contain "net.ipv4.ip_forward = 0"
2. The output should be empty
3. The output should contain "net.ipv6.conf.all.forwarding = 0"
4. The output should be empty';

# ------------------------------------------------------------------
# CONNECTION CHECK
# ------------------------------------------------------------------

if(!get_kb_item("login/SSH/success") || !sock = ssh_login_or_reuse_connection()){

  report_ssh_error(title: title,
                   solution: solution,
                   action: action,
                   expected_value: expected_value,
                   check_type: check_type);
  exit(0);
}

overall_pass = FALSE;
actual_value = "";

# ------------------------------------------------------------------
# CHECK 1 :  Verify command `sysctl net.ipv4.ip_forward`
# ------------------------------------------------------------------

step_cmd_check_1 = 'sysctl net.ipv4.ip_forward';
step_res_check_1 = ssh_cmd(socket:sock, cmd:step_cmd_check_1, return_errors:TRUE, return_linux_errors_only:TRUE);
actual_value += '1. ' + step_res_check_1 + '\n';
check_result_1 = FALSE;

if(strstr(step_res_check_1, 'net.ipv4.ip_forward = 0')){
  check_result_1 = TRUE;
}

# ------------------------------------------------------------------
# CHECK 2 :  Verify command `grep -E -s "^\\s*net\\.ipv4\\.ip_forward\\s*=\\s*1" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf`
# ------------------------------------------------------------------

step_cmd_check_2 = 'grep -E -s "^\\s*net\\.ipv4\\.ip_forward\\s*=\\s*1" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf';
step_res_check_2 = ssh_cmd(socket:sock, cmd:step_cmd_check_2, return_errors:TRUE, return_linux_errors_only:TRUE);
actual_value += '2. ' + step_res_check_2 + '\n';
check_result_2 = FALSE;

if(!step_res_check_2){
  check_result_2 = TRUE;
}

# ------------------------------------------------------------------
# CHECK 3 :  Verify command `sysctl net.ipv6.conf.all.forwarding`
# ------------------------------------------------------------------

step_cmd_check_3 = 'sysctl net.ipv6.conf.all.forwarding';
step_res_check_3 = ssh_cmd(socket:sock, cmd:step_cmd_check_3, return_errors:TRUE, return_linux_errors_only:TRUE);
actual_value += '3. ' + step_res_check_3 + '\n';
check_result_3 = FALSE;

if(strstr(step_res_check_3, 'net.ipv6.conf.all.forwarding = 0')){
  check_result_3 = TRUE;
}

# ------------------------------------------------------------------
# CHECK 4 :  Verify command `grep -E -s "^\\s*net\\.ipv6\\.conf\\.all\\.forwarding\\s*=\\s*1" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf`
# ------------------------------------------------------------------

step_cmd_check_4 = 'grep -E -s "^\\s*net\\.ipv6\\.conf\\.all\\.forwarding\\s*=\\s*1" /etc/sysctl.conf /etc/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /run/sysctl.d/*.conf';
step_res_check_4 = ssh_cmd(socket:sock, cmd:step_cmd_check_4, return_errors:TRUE, return_linux_errors_only:TRUE);
actual_value += '4. ' + step_res_check_4 + '\n';
check_result_4 = FALSE;

if(!step_res_check_4){
  check_result_4 = TRUE;
}

# ------------------------------------------------------------------
# FINAL RESULT
# ------------------------------------------------------------------

if(eregmatch(string: actual_value, pattern:"(No such file or directory|Permission denied|Command not found|Segmentation fault|service not found|is not running|syntax error near unexpected token|syntax error: unexpected end of file)", icase: TRUE)){
  compliant = "incomplete";
  comment = "Something went wrong during the some audit check. Please try again.";
}
else if(check_result_1 && check_result_2 && check_result_3 && check_result_4){
  compliant = "yes";
  comment = "All checks passed";
}else{
  compliant = "no";
  comment = "One or more checks failed";
}

# ------------------------------------------------------------------
# REPORT
# ------------------------------------------------------------------

target = get_kb_item("policy/ssh/login/os-release");
comment = "Target: " + target + "\n" + comment;

report_audit(action: action,
             actual_value: actual_value,
             expected_value: expected_value,
             is_compliant: compliant,
             solution: solution,
             check_type: check_type,
             title: title,
             comment: comment);

exit(0);