Disable the Function of Forwarding ICMP Redirect Messages

# 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("1.3.6.1.4.1.25623.1.0.130346");
  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 the Function of Forwarding ICMP Redirect Messages");

  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: 3.5.8 Disable the Function of Forwarding ICMP Redirect Messages (Requirement)");
  script_xref(name:"Policy", value:"EulerOS Virtual: openEuler Security Configuration Baseline (v1.0.0): 3. Running and Services: 3.5 Kernel: 3.5.8 Disable the Function of Forwarding ICMP Redirect Messages (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: 3.5.8 Disable the Function of Forwarding ICMP Redirect Messages (Requirement)");
  script_xref(name:"Policy", value:"openEuler Baseline: openEuler Security Configuration Baseline (v1.0.0): 3. Running and Services: 3.5 Kernel: 3.5.8 Disable the Function of Forwarding ICMP Redirect Messages (Requirement)");

  script_tag(name:"summary", value:"ICMP redirects can be used to send routing information to other
hosts. As a host itself does not act as a router, it is unnecessary for the host to forward ICMP
redirect messages.

Attackers can exploit the compromised host to send invalid ICMP redirect messages to other routers,
attempting to damage routes and mislead users to access other systems.");

  exit(0);
}

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

title = "Disable the Function of Forwarding ICMP Redirect Messages";

solution = "Run the following commands to disable the function of forwarding ICMP redirect
messages:

# sysctl -w net.ipv4.conf.all.send_redirects=0
# sysctl -w net.ipv4.conf.default.send_redirects=0
# sysctl -w net.ipv4.route.flush=1

Open the /etc/sysctl.conf file and add or modify the following configurations:

net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.default.send_redirects=0";

check_type = "SSH_Cmd";

action = '1. Run the command in the terminal:
# sysctl net.ipv4.conf.all.send_redirects && sysctl net.ipv4.conf.default.send_redirects

2. Run the command in the terminal:
# grep -Eh \'net.ipv4.conf.all.send_redirects\' /etc/sysctl.conf /etc/sysctl.d/*

3. Run the command in the terminal:
# grep -Eh \'net.ipv4.conf.default.send_redirects\' /etc/sysctl.conf /etc/sysctl.d/*';

expected_value = '1. The output should match the pattern "net.ipv4.conf.all.send_redirects = 0\\s*net.ipv4.conf.default.send_redirects = 0"
2. The output should match the pattern "net.ipv4.conf.all.send_redirects=0"
3. The output should match the pattern "net.ipv4.conf.default.send_redirects=0"';

# ------------------------------------------------------------------
# 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.conf.all.send_redirects && sysctl net.ipv4.conf.default.send_redirects`
# ------------------------------------------------------------------

step_cmd_check_1 = 'sysctl net.ipv4.conf.all.send_redirects && sysctl net.ipv4.conf.default.send_redirects';
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(step_res_check_1 =~ 'net.ipv4.conf.all.send_redirects = 0\\s*net.ipv4.conf.default.send_redirects = 0'){
  check_result_1 = TRUE;
}

# ------------------------------------------------------------------
# CHECK 2 :  Verify command `grep -Eh \'net.ipv4.conf.all.send_redirects\' /etc/sysctl.conf /etc/sysctl.d/*`
# ------------------------------------------------------------------

step_cmd_check_2 = 'grep -Eh \'net.ipv4.conf.all.send_redirects\' /etc/sysctl.conf /etc/sysctl.d/*';
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 =~ 'net.ipv4.conf.all.send_redirects=0'){
  check_result_2 = TRUE;
}

# ------------------------------------------------------------------
# CHECK 3 :  Verify command `grep -Eh \'net.ipv4.conf.default.send_redirects\' /etc/sysctl.conf /etc/sysctl.d/*`
# ------------------------------------------------------------------

step_cmd_check_3 = 'grep -Eh \'net.ipv4.conf.default.send_redirects\' /etc/sysctl.conf /etc/sysctl.d/*';
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(step_res_check_3 =~ 'net.ipv4.conf.default.send_redirects=0'){
  check_result_3 = 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){
  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);