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fips_setup/scripts/06-configure-dns.sh
2026-04-11 20:40:01 -04:00

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#!/bin/bash
# ==============================================================================
# 06-configure-dns.sh
#
# Configure dnsmasq in sys-fips so .fips queries are forwarded to local
# FIPS DNS resolver on 127.0.0.1:5354, and all other DNS goes upstream.
#
# Also applies Qubes-specific nftables DNS interception so AppVM DNS queries
# are forced to local dnsmasq in sys-fips.
#
# Usage:
# sudo bash 06-configure-dns.sh
# ==============================================================================
set -euo pipefail
echo "=== sys-fips DNS Configuration ==="
echo ""
if [ "$(id -u)" -ne 0 ]; then
echo "✗ This script must be run as root (sudo)"
exit 1
fi
ensure_nft_rule() {
local table="$1"
local chain="$2"
local rule="$3"
if ! nft list chain "$table" "$chain" >/dev/null 2>&1; then
echo " WARN: nft chain $table $chain not found; skipping: $rule"
return 0
fi
if nft list chain "$table" "$chain" | grep -F -- "$rule" >/dev/null 2>&1; then
return 0
fi
nft add rule "$table" "$chain" $rule
}
systemctl stop dnsmasq 2>/dev/null || true
killall dnsmasq 2>/dev/null || true
UPSTREAM_DNS=$(grep '^nameserver' /etc/resolv.conf | awk '{print $2}' | head -1)
UPSTREAM_DNS="${UPSTREAM_DNS:-10.139.1.1}"
echo " Upstream DNS: $UPSTREAM_DNS"
mkdir -p /etc/dnsmasq.d
cat > /etc/dnsmasq.d/fips.conf << EOF
# sys-fips DNS resolution
port=53
listen-address=0.0.0.0
bind-interfaces
# .fips domains -> FIPS resolver
server=/fips/127.0.0.1#5354
# everything else -> upstream
server=$UPSTREAM_DNS
no-resolv
no-hosts
# log-queries
EOF
if [ ! -f /etc/dnsmasq.conf ]; then
touch /etc/dnsmasq.conf
fi
if ! grep -q 'conf-dir=/etc/dnsmasq.d/,*.conf' /etc/dnsmasq.conf; then
echo 'conf-dir=/etc/dnsmasq.d/,*.conf' >> /etc/dnsmasq.conf
fi
if ! dnsmasq --test >/dev/null 2>&1; then
echo "✗ dnsmasq config failed validation"
exit 1
fi
# Qubes AppVMs often use /32 point-to-point addressing.
# Debian's dnsmasq systemd-helper adds --local-service by default,
# which can reject DNS queries from downstream AppVMs in this topology.
DNSMASQ_HELPER="/usr/share/dnsmasq/systemd-helper"
if [ -f "$DNSMASQ_HELPER" ] && grep -q -- '--local-service' "$DNSMASQ_HELPER"; then
if [ ! -f "${DNSMASQ_HELPER}.bak" ]; then
cp "$DNSMASQ_HELPER" "${DNSMASQ_HELPER}.bak"
fi
sed -i 's/--local-service//g' "$DNSMASQ_HELPER"
echo " Patched dnsmasq helper: removed --local-service for Qubes /32 compatibility"
fi
if command -v systemctl >/dev/null 2>&1; then
systemctl restart dnsmasq || true
fi
if ! pgrep -x dnsmasq >/dev/null 2>&1; then
dnsmasq
fi
echo "Applying Qubes nftables DNS interception rules..."
ensure_nft_rule ip qubes dnat-dns 'iifname "vif*" udp dport 53 dnat to 10.139.1.1:53'
ensure_nft_rule ip qubes dnat-dns 'iifname "vif*" tcp dport 53 dnat to 10.139.1.1:53'
ensure_nft_rule ip qubes custom-input 'iifname "vif*" ip daddr 10.139.1.1 udp dport 53 accept'
ensure_nft_rule ip qubes custom-input 'iifname "vif*" ip daddr 10.139.1.1 tcp dport 53 accept'
echo " nftables DNS interception ensured"
RCLOCAL="/rw/config/rc.local"
MARK_START="# === SYS-FIPS DNS START ==="
MARK_END="# === SYS-FIPS DNS END ==="
if [ ! -f "$RCLOCAL" ]; then
mkdir -p /rw/config
cat > "$RCLOCAL" << 'EOF'
#!/bin/sh
EOF
fi
sed -i "/$MARK_START/,/$MARK_END/d" "$RCLOCAL"
cat >> "$RCLOCAL" << 'EOF'
# === SYS-FIPS DNS START ===
# Keep dnsmasq alive with .fips forwarding
if [ -f /usr/share/dnsmasq/systemd-helper ]; then
sed -i 's/--local-service//g' /usr/share/dnsmasq/systemd-helper
fi
systemctl restart dnsmasq >/dev/null 2>&1 || true
pgrep -x dnsmasq >/dev/null 2>&1 || dnsmasq >/dev/null 2>&1 || true
# Qubes DNS interception for downstream AppVMs
nft list chain ip qubes dnat-dns >/dev/null 2>&1 && \
nft list chain ip qubes dnat-dns | grep -F 'iifname "vif*" udp dport 53 dnat to 10.139.1.1:53' >/dev/null 2>&1 || \
nft add rule ip qubes dnat-dns iifname "vif*" udp dport 53 dnat to 10.139.1.1:53 >/dev/null 2>&1 || true
nft list chain ip qubes dnat-dns >/dev/null 2>&1 && \
nft list chain ip qubes dnat-dns | grep -F 'iifname "vif*" tcp dport 53 dnat to 10.139.1.1:53' >/dev/null 2>&1 || \
nft add rule ip qubes dnat-dns iifname "vif*" tcp dport 53 dnat to 10.139.1.1:53 >/dev/null 2>&1 || true
nft list chain ip qubes custom-input >/dev/null 2>&1 && \
nft list chain ip qubes custom-input | grep -F 'iifname "vif*" ip daddr 10.139.1.1 udp dport 53 accept' >/dev/null 2>&1 || \
nft add rule ip qubes custom-input iifname "vif*" ip daddr 10.139.1.1 udp dport 53 accept >/dev/null 2>&1 || true
nft list chain ip qubes custom-input >/dev/null 2>&1 && \
nft list chain ip qubes custom-input | grep -F 'iifname "vif*" ip daddr 10.139.1.1 tcp dport 53 accept' >/dev/null 2>&1 || \
nft add rule ip qubes custom-input iifname "vif*" ip daddr 10.139.1.1 tcp dport 53 accept >/dev/null 2>&1 || true
# === SYS-FIPS DNS END ===
EOF
chmod +x "$RCLOCAL"
echo ""
echo "Verifying DNS..."
if dig @127.0.0.1 google.com A +short +time=2 >/dev/null 2>&1; then
echo " Upstream DNS: OK"
else
echo " Upstream DNS: WARN (may be expected in isolated setup)"
fi
STATUS=$(dig @127.0.0.1 test.fips AAAA +time=2 2>&1 | grep 'status:' || true)
if echo "$STATUS" | grep -qE 'NXDOMAIN|SERVFAIL|NOERROR'; then
echo " .fips forwarding: OK"
else
echo " .fips forwarding: WARN"
fi
echo ""
echo "✓ DNS configured"