Fortalecimento de Endpoints Linux com o CIS Benchmark

Quando Usar

Use esta habilidade quando:

• Estiver fortalecendo servidores Linux (Ubuntu, RHEL, CentOS, Debian) contra os benchmarks do CIS
• Estiver automatizando linhas de base de segurança Linux usando Ansible, OpenSCAP ou scripts shell
• Precisar atender a requisitos de conformidade (PCI DSS, HIPAA, SOC 2) para endpoints Linux
• Estiver remediando descobertas de varreduras de vulnerabilidade ou auditorias de segurança

Não use para fortalecimento de Windows (use hardening-windows-endpoint-with-cis-benchmark).

Pré-requisitos

• Acesso root ou sudo nos endpoints Linux de destino
• PDF do CIS Benchmark para a distribuição de destino (de cisecurity.org)
• OpenSCAP ou CIS-CAT para avaliação automatizada
• Ansible para remediação em escala empresarial (opcional)

Fluxo de Trabalho

Etapa 1: Configuração do Sistema de Arquivos (Seção 1)

# 1.1.1 Disable unused filesystems
cat >> /etc/modprobe.d/CIS.conf << 'EOF'
install cramfs /bin/true
install freevxfs /bin/true
install jffs2 /bin/true
install hfs /bin/true
install hfsplus /bin/true
install squashfs /bin/true
install udf /bin/true
EOF

# 1.1.2 Ensure /tmp is a separate partition with nodev,nosuid,noexec
# /etc/fstab entry:
# tmpfs /tmp tmpfs defaults,rw,nosuid,nodev,noexec,relatime 0 0
systemctl unmask tmp.mount
systemctl enable tmp.mount

# 1.1.8 Ensure nodev option on /dev/shm
mount -o remount,nodev,nosuid,noexec /dev/shm
echo "tmpfs /dev/shm tmpfs defaults,nodev,nosuid,noexec 0 0" >> /etc/fstab

# 1.4 Secure boot settings
chown root:root /boot/grub/grub.cfg
chmod 600 /boot/grub/grub.cfg
# Set GRUB password
grub-mkpasswd-pbkdf2  # Generate hash, add to /etc/grub.d/40_custom

Etapa 2: Serviços e Rede (Seções 2-3)

# 2.1 Disable unnecessary services
systemctl disable --now avahi-daemon
systemctl disable --now cups
systemctl disable --now rpcbind
systemctl disable --now xinetd

# 2.2 Ensure NTP is configured
apt install chrony -y  # or systemd-timesyncd
systemctl enable --now chrony

# 3.1 Network parameters (host only, not router)
cat >> /etc/sysctl.d/99-cis.conf << 'EOF'
net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
net.ipv4.conf.all.log_martians = 1
net.ipv4.conf.default.log_martians = 1
net.ipv4.icmp_echo_ignore_broadcasts = 1
net.ipv4.icmp_ignore_bogus_error_responses = 1
net.ipv4.conf.all.rp_filter = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.tcp_syncookies = 1
net.ipv6.conf.all.accept_ra = 0
net.ipv6.conf.default.accept_ra = 0
EOF
sysctl --system

# 3.4 Configure firewall (UFW or firewalld)
ufw enable
ufw default deny incoming
ufw default allow outgoing
ufw allow ssh

Etapa 3: Controle de Acesso (Seções 4-5)

# 5.2 SSH Server Configuration (/etc/ssh/sshd_config)
sed -i 's/#Protocol 2/Protocol 2/' /etc/ssh/sshd_config
cat >> /etc/ssh/sshd_config << 'EOF'
LogLevel VERBOSE
MaxAuthTries 4
PermitRootLogin no
PermitEmptyPasswords no
PasswordAuthentication no
X11Forwarding no
MaxStartups 10:30:60
LoginGraceTime 60
AllowTcpForwarding no
ClientAliveInterval 300
ClientAliveCountMax 3
EOF
systemctl restart sshd

# 5.3 Password policy (PAM)
# /etc/security/pwquality.conf
minlen = 14
dcredit = -1
ucredit = -1
ocredit = -1
lcredit = -1

# 5.4 User account settings
# /etc/login.defs
PASS_MAX_DAYS 365
PASS_MIN_DAYS 1
PASS_WARN_AGE 7

# Lock inactive accounts
useradd -D -f 30

Etapa 4: Auditoria e Logs (Seção 4)

# Instalar e configurar o auditd
apt install auditd audispd-plugins -y
systemctl enable --now auditd

# /etc/audit/rules.d/cis.rules
cat > /etc/audit/rules.d/cis.rules << 'EOF'
-w /etc/sudoers -p wa -k scope
-w /etc/sudoers.d/ -p wa -k scope
-w /var/log/sudo.log -p wa -k actions
-a always,exit -F arch=b64 -S adjtimex -S settimeofday -k time-change
-a always,exit -F arch=b64 -S sethostname -S setdomainname -k system-locale
-w /etc/group -p wa -k identity
-w /etc/passwd -p wa -k identity
-w /etc/shadow -p wa -k identity
-w /var/log/faillog -p wa -k logins
-w /var/log/lastlog -p wa -k logins
-a always,exit -F arch=b64 -S chmod -S fchmod -S fchmodat -k perm_mod
-a always,exit -F arch=b64 -S unlink -S rmdir -S rename -k delete
-w /sbin/insmod -p x -k modules
-w /sbin/modprobe -p x -k modules
-e 2
EOF
augenrules --load

# Configurar o rsyslog para logs remotos

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