# Arcline OS — kernel hardening (sysctl)
# Applies to every edition via the base overlay. Conservative defaults;
# the workstation edition relaxes a couple of entries (see overlays/workstation).

# ── memory ──────────────────────────────────────────────────────────────────
vm.swappiness=10
vm.overcommit_memory=2
vm.dirty_ratio=5
vm.dirty_background_ratio=2

# ── networking ──────────────────────────────────────────────────────────────
# strict reverse-path filtering
net.ipv4.conf.all.rp_filter=1
net.ipv4.conf.default.rp_filter=1
# no ICMP redirects
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.send_redirects=0
net.ipv4.conf.default.send_redirects=0
net.ipv6.conf.all.accept_redirects=0
net.ipv6.conf.default.accept_redirects=0
# ICMP hardening
net.ipv4.icmp_echo_ignore_broadcasts=1
net.ipv4.icmp_ignore_bogus_error_responses=1
# TCP hardening
net.ipv4.tcp_syncookies=1
net.ipv4.tcp_rfc1337=1
net.ipv4.tcp_timestamps=0
net.ipv4.conf.all.log_martians=1
net.ipv4.conf.default.log_martians=1
# IPv6: don't auto-accept router advertisements
net.ipv6.conf.all.accept_ra=0
net.ipv6.conf.default.accept_ra=0

# ── kernel / visibility ─────────────────────────────────────────────────────
kernel.dmesg_restrict=1
kernel.kptr_restrict=2
kernel.perf_event_paranoid=3
kernel.yama.ptrace_scope=1
kernel.core_uses_pid=1
kernel.unprivileged_bpf_disabled=1
kernel.randomize_va_space=2
kernel.sysrq=4

# ── filesystem hardening ────────────────────────────────────────────────────
fs.protected_hardlinks=1
fs.protected_symlinks=1
fs.protected_fifos=2
fs.protected_regular=2
fs.suid_dumpable=0