1 files changed, 115 insertions, 0 deletions
diff --git a/plugin/acl/acl.go b/plugin/acl/acl.go
new file mode 100644
index 000000000..b25138a30
--- /dev/null
+++ b/plugin/acl/acl.go
@@ -0,0 +1,115 @@
+package acl
+
+import (
+	"context"
+	"net"
+
+	"github.com/coredns/coredns/plugin"
+	"github.com/coredns/coredns/plugin/metrics"
+	clog "github.com/coredns/coredns/plugin/pkg/log"
+	"github.com/coredns/coredns/request"
+
+	"github.com/infobloxopen/go-trees/iptree"
+	"github.com/miekg/dns"
+)
+
+var log = clog.NewWithPlugin("acl")
+
+// ACL enforces access control policies on DNS queries.
+type ACL struct {
+	Next plugin.Handler
+
+	Rules []rule
+}
+
+// rule defines a list of Zones and some ACL policies which will be
+// enforced on them.
+type rule struct {
+	zones    []string
+	policies []policy
+}
+
+// action defines the action against queries.
+type action int
+
+// policy defines the ACL policy for DNS queries.
+// A policy performs the specified action (block/allow) on all DNS queries
+// matched by source IP or QTYPE.
+type policy struct {
+	action action
+	qtypes map[uint16]struct{}
+	filter *iptree.Tree
+}
+
+const (
+	// actionNone does nothing on the queries.
+	actionNone = iota
+	// actionAllow allows authorized queries to recurse.
+	actionAllow
+	// actionBlock blocks unauthorized queries towards protected DNS zones.
+	actionBlock
+)
+
+// ServeDNS implements the plugin.Handler interface.
+func (a ACL) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	state := request.Request{W: w, Req: r}
+
+RulesCheckLoop:
+	for _, rule := range a.Rules {
+		// check zone.
+		zone := plugin.Zones(rule.zones).Matches(state.Name())
+		if zone == "" {
+			continue
+		}
+
+		action := matchWithPolicies(rule.policies, w, r)
+		switch action {
+		case actionBlock:
+			{
+				m := new(dns.Msg)
+				m.SetRcode(r, dns.RcodeRefused)
+				w.WriteMsg(m)
+				RequestBlockCount.WithLabelValues(metrics.WithServer(ctx), zone).Inc()
+				return dns.RcodeSuccess, nil
+			}
+		case actionAllow:
+			{
+				break RulesCheckLoop
+			}
+		}
+	}
+
+	RequestAllowCount.WithLabelValues(metrics.WithServer(ctx)).Inc()
+	return plugin.NextOrFailure(state.Name(), a.Next, ctx, w, r)
+}
+
+// matchWithPolicies matches the DNS query with a list of ACL polices and returns suitable
+// action agains the query.
+func matchWithPolicies(policies []policy, w dns.ResponseWriter, r *dns.Msg) action {
+	state := request.Request{W: w, Req: r}
+
+	ip := net.ParseIP(state.IP())
+	qtype := state.QType()
+	for _, policy := range policies {
+		// dns.TypeNone matches all query types.
+		_, matchAll := policy.qtypes[dns.TypeNone]
+		_, match := policy.qtypes[qtype]
+		if !matchAll && !match {
+			continue
+		}
+
+		_, contained := policy.filter.GetByIP(ip)
+		if !contained {
+			continue
+		}
+
+		// matched.
+		return policy.action
+	}
+	return actionNone
+}
+
+// Name implements the plugin.Handler interface.
+func (a ACL) Name() string {
+	return "acl"
+}