mirror of
https://github.com/lgcosta/pf-linux-port.git
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51 lines
2.4 KiB
Bash
Executable File
51 lines
2.4 KiB
Bash
Executable File
#!/usr/bin/env bash
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# M2 gate 4: anchors + evaluation order (OpenBSD semantics)
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#
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# OpenBSD evaluates the IN ruleset in ip_input() for every arriving packet and
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# the OUT ruleset in ip_forward() for forwarded packets. A `block in ... icmp`
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# rule therefore also sees the *reply* of a transit flow - a state created by
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# an anchor rule does NOT rescue the reply at input time. This gate keeps the
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# ruleset OpenBSD-correct and isolates the anchor semantics:
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#
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# anchor "restricted" -> child: pass in quick ... from <client> keep state
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# block drop in quick proto icmp from any to <server> (would drop the request)
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# pass in quick / pass out quick
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#
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# The request must be passed by the ANCHOR child rule (the later block rule
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# would drop it), and a state must exist. After flushing the anchor the very
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# same request must be dropped - proving the anchor is what allowed it.
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set -uo pipefail; cd "$(dirname "$0")"; . ./lib.sh
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pf0 'insmod /opt/pf/pf.ko 2>/dev/null || insmod /tmp/pf.ko; true'
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pf0 '/opt/pf/pfctl -e; /opt/pf/pfctl -f /dev/null' >/dev/null
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cat > /tmp/g4main.conf <<C
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anchor "restricted"
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block drop in quick proto icmp from any to $SRV_IP
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pass in quick
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pass out quick
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C
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cat > /tmp/g4anc.conf <<C
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pass in quick proto icmp from $CLI_IP to any keep state
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C
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pfload /tmp/g4main.conf || { bad "main ruleset load"; finish; }
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ANC=$(pfput /tmp/g4anc.conf) || { bad "anchor conf upload"; finish; }
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pf0 "/opt/pf/pfctl -a restricted -f $ANC" || { bad "anchor ruleset load"; finish; }
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pf0 '/opt/pf/pfctl -sr' | grep -q 'anchor "restricted"' && ok "anchor rule in main ruleset" || bad "anchor rule missing"
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pf0 '/opt/pf/pfctl -a restricted -sr' | grep -q 'proto icmp from' && ok "anchor rules listed" || bad "anchor rules missing"
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# the request must pass through the anchor (the block rule would drop it)
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cli "ping -c2 -W2 $SRV_IP >/dev/null 2>&1" && ok "anchor pass honoured (request allowed)" \
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|| bad "anchor pass not honored"
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pf0 '/opt/pf/pfctl -ss' | grep -q "$SRV_IP" && ok "state created by anchor rule" || bad "no state from anchor"
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# without the anchor rule the request hits the block rule -> dropped
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pf0 "/opt/pf/pfctl -a restricted -F all" >/dev/null 2>&1
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cli "ping -c1 -W2 $SRV_IP >/dev/null 2>&1" && bad "request passed without anchor rule" \
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|| ok "request dropped without anchor rule (block applies)"
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pf0 '/opt/pf/pfctl -d; /opt/pf/pfctl -f /dev/null' >/dev/null
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finish
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