Add middleware/dnssec (#133)

This adds an online dnssec middleware. The middleware will sign
responses on the fly. Negative responses are signed with NSEC black
lies.

.gitignore

@@ -1,2 +1,4 @@
 query.log
 Corefile
+*.swp
+coredns

core/directives.go

@@ -60,6 +60,7 @@ var directiveOrder = []directive{
 	{"rewrite", setup.Rewrite},
 	{"loadbalance", setup.Loadbalance},
 	{"cache", setup.Cache},
+	{"dnssec", setup.Dnssec},
 	{"file", setup.File},
 	{"secondary", setup.Secondary},
 	{"etcd", setup.Etcd},

core/setup/cache.go

@@ -27,8 +27,7 @@ func cacheParse(c *Controller) (int, []string, error) {
 	for c.Next() {
 		if c.Val() == "cache" {
 			// cache [ttl] [zones..]
-
-			origins := []string{c.ServerBlockHosts[c.ServerBlockHostIndex]}
+			origins := c.ServerBlockHosts
 			args := c.RemainingArgs()
 			if len(args) > 0 {
 				origins = args
@@ -39,7 +38,7 @@ func cacheParse(c *Controller) (int, []string, error) {
 					origins = origins[1:]
 					if len(origins) == 0 {
 						// There was *only* the ttl, revert back to server block
-						origins = []string{c.ServerBlockHosts[c.ServerBlockHostIndex]}
+						origins = c.ServerBlockHosts
 					}
 				}
 			}

core/setup/chaos_test.go

@@ -10,7 +10,7 @@ func TestChaos(t *testing.T) {
 	tests := []struct {
 		input              string
 		shouldErr          bool
-		expectedVersion    string // expected veresion.
+		expectedVersion    string // expected version.
 		expectedAuthor     string // expected author (string, although we get a map).
 		expectedErrContent string // substring from the expected error. Empty for positive cases.
 	}{

core/setup/dnssec.go

@@ -0,0 +1,79 @@
+package setup
+
+import (
+	"path"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/dnssec"
+)
+
+// Dnssec sets up the dnssec middleware.
+func Dnssec(c *Controller) (middleware.Middleware, error) {
+	zones, keys, err := dnssecParse(c)
+	if err != nil {
+		return nil, err
+	}
+
+	return func(next middleware.Handler) middleware.Handler {
+		return dnssec.NewDnssec(zones, keys, next)
+	}, nil
+}
+
+func dnssecParse(c *Controller) ([]string, []*dnssec.DNSKEY, error) {
+	zones := []string{}
+
+	keys := []*dnssec.DNSKEY{}
+	for c.Next() {
+		if c.Val() == "dnssec" {
+			// dnssec [zones...]
+			zones = c.ServerBlockHosts
+			args := c.RemainingArgs()
+			if len(args) > 0 {
+				zones = args
+			}
+
+			for c.NextBlock() {
+				k, e := keyParse(c)
+				if e != nil {
+					// TODO(miek): Log and drop or something? stop startup?
+					continue
+				}
+				keys = append(keys, k...)
+			}
+		}
+	}
+	for i, _ := range zones {
+		zones[i] = middleware.Host(zones[i]).Normalize()
+	}
+	return zones, keys, nil
+}
+
+func keyParse(c *Controller) ([]*dnssec.DNSKEY, error) {
+	keys := []*dnssec.DNSKEY{}
+
+	what := c.Val()
+	if !c.NextArg() {
+		return nil, c.ArgErr()
+	}
+	value := c.Val()
+	switch what {
+	case "key":
+		if value == "file" {
+			ks := c.RemainingArgs()
+			for _, k := range ks {
+				// Kmiek.nl.+013+26205.key, handle .private or without extension: Kmiek.nl.+013+26205
+				ext := path.Ext(k) // TODO(miek): test things like .key
+				base := k
+				if len(ext) > 0 {
+					base = k[:len(k)-len(ext)]
+				}
+				k, err := dnssec.ParseKeyFile(base+".key", base+".private")
+				if err != nil {
+					return nil, err
+				}
+				keys = append(keys, k)
+			}
+		}
+	}
+	return keys, nil
+}

core/setup/dnssec_test.go

@@ -0,0 +1,54 @@
+package setup
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestDnssec(t *testing.T) {
+	tests := []struct {
+		input              string
+		shouldErr          bool
+		expectedZones      []string
+		expectedKeys       []string
+		expectedErrContent string
+	}{
+		{
+			`dnssec`, false, nil, nil, "",
+		},
+		{
+			`dnssec miek.nl`, false, []string{"miek.nl."}, nil, "",
+		},
+	}
+
+	for i, test := range tests {
+		c := NewTestController(test.input)
+		zones, keys, err := dnssecParse(c)
+
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error but found %s for input %s", i, err, test.input)
+		}
+
+		if err != nil {
+			if !test.shouldErr {
+				t.Errorf("Test %d: Expected no error but found one for input %s. Error was: %v", i, test.input, err)
+			}
+
+			if !strings.Contains(err.Error(), test.expectedErrContent) {
+				t.Errorf("Test %d: Expected error to contain: %v, found error: %v, input: %s", i, test.expectedErrContent, err, test.input)
+			}
+		}
+		if !test.shouldErr {
+			for i, z := range test.expectedZones {
+				if zones[i] != z {
+					t.Errorf("Dnssec not correctly set for input %s. Expected: %s, actual: %s", test.input, z, zones[i])
+				}
+			}
+			for i, k := range test.expectedKeys {
+				if k != keys[i].K.Header().Name {
+					t.Errorf("Dnssec not correctly set for input %s. Expected: '%s', actual: '%s'", test.input, k, keys[i].K.Header().Name)
+				}
+			}
+		}
+	}
+}

core/setup/etcd.go

@@ -10,8 +10,8 @@ import (
 
 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/etcd"
-	"github.com/miekg/coredns/middleware/etcd/singleflight"
 	"github.com/miekg/coredns/middleware/proxy"
+	"github.com/miekg/coredns/middleware/singleflight"
 
 	etcdc "github.com/coreos/etcd/client"
 	"golang.org/x/net/context"

core/setup/file.go

@@ -46,7 +46,7 @@ func fileParse(c *Controller) (file.Zones, error) {
 			}
 			fileName := c.Val()
 
-			origins := []string{c.ServerBlockHosts[c.ServerBlockHostIndex]}
+			origins := c.ServerBlockHosts
 			args := c.RemainingArgs()
 			if len(args) > 0 {
 				origins = args
@@ -54,7 +54,7 @@ func fileParse(c *Controller) (file.Zones, error) {
 
 			reader, err := os.Open(fileName)
 			if err != nil {
-				return file.Zones{}, err
+				continue
 			}
 
 			for i, _ := range origins {
@@ -68,7 +68,7 @@ func fileParse(c *Controller) (file.Zones, error) {
 
 			noReload := false
 			for c.NextBlock() {
-				t, _, e := parseTransfer(c)
+				t, _, e := transferParse(c)
 				if e != nil {
 					return file.Zones{}, e
 				}
@@ -89,8 +89,8 @@ func fileParse(c *Controller) (file.Zones, error) {
 	return file.Zones{Z: z, Names: names}, nil
 }
 
-// transfer to [address...]
-func parseTransfer(c *Controller) (tos, froms []string, err error) {
+// transferParse parses transfer statements: 'transfer to [address...]'.
+func transferParse(c *Controller) (tos, froms []string, err error) {
 	what := c.Val()
 	if !c.NextArg() {
 		return nil, nil, c.ArgErr()

core/setup/metrics.go

@@ -7,10 +7,7 @@ import (
 	"github.com/miekg/coredns/middleware/metrics"
 )
 
-const (
-	path = "/metrics"
-	addr = "localhost:9135" // 9153 is occupied by bind_exporter
-)
+const addr = "localhost:9135" // 9153 is occupied by bind_exporter
 
 var once sync.Once
 

core/setup/secondary.go

@@ -40,7 +40,7 @@ func secondaryParse(c *Controller) (file.Zones, error) {
 	for c.Next() {
 		if c.Val() == "secondary" {
 			// secondary [origin]
-			origins := []string{c.ServerBlockHosts[c.ServerBlockHostIndex]}
+			origins := c.ServerBlockHosts
 			args := c.RemainingArgs()
 			if len(args) > 0 {
 				origins = args
@@ -52,7 +52,7 @@ func secondaryParse(c *Controller) (file.Zones, error) {
 			}
 
 			for c.NextBlock() {
-				t, f, e := parseTransfer(c)
+				t, f, e := transferParse(c)
 				if e != nil {
 					return file.Zones{}, e
 				}

middleware/cache/cache.go

@@ -1,33 +1,5 @@
 package cache
 
-/*
-The idea behind this implementation is as follows. We have a cache that is index
-by a couple different keys, which allows use to have:
-
-- negative cache: qname only for NXDOMAIN responses
-- negative cache: qname + qtype for NODATA responses
-- positive cache: qname + qtype for succesful responses.
-
-We track DNSSEC responses separately, i.e. under a different cache key.
-Each Item stored contains the message split up in the different sections
-and a few bits of the msg header.
-
-For instance an NXDOMAIN for blaat.miek.nl will create the
-following negative cache entry (do signal state of DO (do off, DO on)).
-
-	ncache: do <blaat.miek.nl>
-	Item:
-		Ns: <miek.nl> SOA RR
-
-If found a return packet is assembled and returned to the client. Taking size and EDNS0
-constraints into account.
-
-We also need to track if the answer received was an authoritative answer, ad bit and other
-setting, for this we also store a few header bits.
-
-For the positive cache we use the same idea. Truncated responses are never stored.
-*/
-
 import (
 	"log"
 	"time"
@@ -50,41 +22,7 @@ func NewCache(ttl int, zones []string, next middleware.Handler) Cache {
 	return Cache{Next: next, Zones: zones, cache: gcache.New(defaultDuration, purgeDuration), cap: time.Duration(ttl) * time.Second}
 }
 
-type messageType int
-
-const (
-	success    messageType = iota
-	nameError              // NXDOMAIN in header, SOA in auth.
-	noData                 // NOERROR in header, SOA in auth.
-	otherError             // Don't cache these.
-)
-
-// classify classifies a message, it returns the MessageType.
-func classify(m *dns.Msg) (messageType, *dns.OPT) {
-	opt := m.IsEdns0()
-	soa := false
-	if m.Rcode == dns.RcodeSuccess {
-		return success, opt
-	}
-	for _, r := range m.Ns {
-		if r.Header().Rrtype == dns.TypeSOA {
-			soa = true
-			break
-		}
-	}
-
-	// Check length of different section, and drop stuff that is just to large.
-	if soa && m.Rcode == dns.RcodeSuccess {
-		return noData, opt
-	}
-	if soa && m.Rcode == dns.RcodeNameError {
-		return nameError, opt
-	}
-
-	return otherError, opt
-}
-
-func cacheKey(m *dns.Msg, t messageType, do bool) string {
+func cacheKey(m *dns.Msg, t middleware.MsgType, do bool) string {
 	if m.Truncated {
 		return ""
 	}
@@ -92,13 +30,15 @@ func cacheKey(m *dns.Msg, t messageType, do bool) string {
 	qtype := m.Question[0].Qtype
 	qname := middleware.Name(m.Question[0].Name).Normalize()
 	switch t {
-	case success:
+	case middleware.Success:
+		fallthrough
+	case middleware.Delegation:
 		return successKey(qname, qtype, do)
-	case nameError:
+	case middleware.NameError:
 		return nameErrorKey(qname, do)
-	case noData:
+	case middleware.NoData:
 		return noDataKey(qname, qtype, do)
-	case otherError:
+	case middleware.OtherError:
 		return ""
 	}
 	return ""
@@ -116,13 +56,13 @@ func NewCachingResponseWriter(w dns.ResponseWriter, cache *gcache.Cache, cap tim
 
 func (c *CachingResponseWriter) WriteMsg(res *dns.Msg) error {
 	do := false
-	mt, opt := classify(res)
+	mt, opt := middleware.Classify(res)
 	if opt != nil {
 		do = opt.Do()
 	}
 
 	key := cacheKey(res, mt, do)
-	c.Set(res, key, mt)
+	c.set(res, key, mt)
 
 	if c.cap != 0 {
 		setCap(res, uint32(c.cap.Seconds()))
@@ -131,7 +71,7 @@ func (c *CachingResponseWriter) WriteMsg(res *dns.Msg) error {
 	return c.ResponseWriter.WriteMsg(res)
 }
 
-func (c *CachingResponseWriter) Set(m *dns.Msg, key string, mt messageType) {
+func (c *CachingResponseWriter) set(m *dns.Msg, key string, mt middleware.MsgType) {
 	if key == "" {
 		// logger the log? TODO(miek)
 		return
@@ -139,14 +79,14 @@ func (c *CachingResponseWriter) Set(m *dns.Msg, key string, mt messageType) {
 
 	duration := c.cap
 	switch mt {
-	case success:
+	case middleware.Success, middleware.Delegation:
 		if c.cap == 0 {
 			duration = minTtl(m.Answer, mt)
 		}
 		i := newItem(m, duration)
 
 		c.cache.Set(key, i, duration)
-	case nameError, noData:
+	case middleware.NameError, middleware.NoData:
 		if c.cap == 0 {
 			duration = minTtl(m.Ns, mt)
 		}
@@ -167,19 +107,19 @@ func (c *CachingResponseWriter) Hijack() {
 	return
 }
 
-func minTtl(rrs []dns.RR, mt messageType) time.Duration {
-	if mt != success && mt != nameError && mt != noData {
+func minTtl(rrs []dns.RR, mt middleware.MsgType) time.Duration {
+	if mt != middleware.Success && mt != middleware.NameError && mt != middleware.NoData {
 		return 0
 	}
 
 	minTtl := maxTtl
 	for _, r := range rrs {
 		switch mt {
-		case nameError, noData:
+		case middleware.NameError, middleware.NoData:
 			if r.Header().Rrtype == dns.TypeSOA {
 				return time.Duration(r.(*dns.SOA).Minttl) * time.Second
 			}
-		case success:
+		case middleware.Success, middleware.Delegation:
 			if r.Header().Ttl < minTtl {
 				minTtl = r.Header().Ttl
 			}

middleware/cache/cache_test.go

@@ -78,13 +78,13 @@ func TestCache(t *testing.T) {
 		m = cacheMsg(m, tc)
 		do := tc.in.Do
 
-		mt, _ := classify(m)
+		mt, _ := middleware.Classify(m)
 		key := cacheKey(m, mt, do)
-		crr.Set(m, key, mt)
+		crr.set(m, key, mt)
 
 		name := middleware.Name(m.Question[0].Name).Normalize()
 		qtype := m.Question[0].Qtype
-		i, ok := c.Get(name, qtype, do)
+		i, ok := c.get(name, qtype, do)
 		if !ok && !m.Truncated {
 			t.Errorf("Truncated message should not have been cached")
 		}

middleware/cache/handler.go

@@ -21,7 +21,7 @@ func (c Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 
 	do := state.Do() // might need more from OPT record?
 
-	if i, ok := c.Get(qname, qtype, do); ok {
+	if i, ok := c.get(qname, qtype, do); ok {
 		resp := i.toMsg(r)
 		state.SizeAndDo(resp)
 		w.WriteMsg(resp)
@@ -35,12 +35,13 @@ func (c Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 	return c.Next.ServeDNS(ctx, crr, r)
 }
 
-func (c Cache) Get(qname string, qtype uint16, do bool) (*item, bool) {
+func (c Cache) get(qname string, qtype uint16, do bool) (*item, bool) {
 	nxdomain := nameErrorKey(qname, do)
 	if i, ok := c.cache.Get(nxdomain); ok {
 		return i.(*item), true
 	}
 
+	// TODO(miek): delegation was added double check
 	successOrNoData := successKey(qname, qtype, do)
 	if i, ok := c.cache.Get(successOrNoData); ok {
 		return i.(*item), true

middleware/classify.go

@@ -0,0 +1,52 @@
+package middleware
+
+import "github.com/miekg/dns"
+
+type MsgType int
+
+const (
+	Success    MsgType = iota
+	NameError          // NXDOMAIN in header, SOA in auth.
+	NoData             // NOERROR in header, SOA in auth.
+	Delegation         // NOERROR in header, NS in auth, optionally fluff in additional (not checked).
+	OtherError         // Don't cache these.
+)
+
+// Classify classifies a message, it returns the MessageType.
+func Classify(m *dns.Msg) (MsgType, *dns.OPT) {
+	opt := m.IsEdns0()
+
+	if len(m.Answer) > 0 && m.Rcode == dns.RcodeSuccess {
+		return Success, opt
+	}
+
+	soa := false
+	ns := 0
+	for _, r := range m.Ns {
+		if r.Header().Rrtype == dns.TypeSOA {
+			soa = true
+			continue
+		}
+		if r.Header().Rrtype == dns.TypeNS {
+			ns++
+		}
+	}
+
+	// Check length of different sections, and drop stuff that is just to large? TODO(miek).
+	if soa && m.Rcode == dns.RcodeSuccess {
+		return NoData, opt
+	}
+	if soa && m.Rcode == dns.RcodeNameError {
+		return NameError, opt
+	}
+
+	if ns > 0 && ns == len(m.Ns) && m.Rcode == dns.RcodeSuccess {
+		return Delegation, opt
+	}
+
+	if m.Rcode == dns.RcodeSuccess {
+		return Success, opt
+	}
+
+	return OtherError, opt
+}

middleware/classify_test.go

@@ -0,0 +1,31 @@
+package middleware
+
+import (
+	"testing"
+
+	"github.com/miekg/coredns/middleware/test"
+
+	"github.com/miekg/dns"
+)
+
+func TestClassifyDelegation(t *testing.T) {
+	m := delegationMsg()
+	mt, _ := Classify(m)
+	if mt != Delegation {
+		t.Errorf("message is wrongly classified, expected delegation, got %d", mt)
+	}
+}
+
+func delegationMsg() *dns.Msg {
+	return &dns.Msg{
+		Ns: []dns.RR{
+			test.NS("miek.nl.	3600	IN	NS	linode.atoom.net."),
+			test.NS("miek.nl.	3600	IN	NS	ns-ext.nlnetlabs.nl."),
+			test.NS("miek.nl.	3600	IN	NS	omval.tednet.nl."),
+		},
+		Extra: []dns.RR{
+			test.A("omval.tednet.nl.	3600	IN	A	185.49.141.42"),
+			test.AAAA("omval.tednet.nl.	3600	IN	AAAA	2a04:b900:0:100::42"),
+		},
+	}
+}

middleware/dnssec/README.md

@@ -0,0 +1,35 @@
+# dnssec
+
+`dnssec` enables on-the-fly DNSSEC signing of served data.
+
+## Syntax
+
+~~~
+dnssec [zones...]
+~~~
+
+* `zones` zones that should be signed. If empty the zones from the configuration block
+    are used.
+
+If keys are not specified (see below) a key is generated and used for all signing operations. The
+DNSSEC signing will treat this key a CSK (common signing key) forgoing the ZSK/KSK split. All
+signing operations are done online. Authenticated denial of existence is implemented with NSEC black
+lies. Using ECDSA as an algorithm is preferred as this leads to smaller signatures (compared to
+RSA).
+
+A signing key can be specified by using the `key` directive.
+
+TODO(miek): think about key rollovers.
+
+
+~~~
+dnssec [zones... ] {
+    key file [key...]
+}
+~~~
+
+* `key file` indicates key file(s) should be read from disk. When multiple keys are specified, RRset
+  will be signed with all keys. Generating a key can be done with `dnssec-keygen`: `dnssec-keygen -a
+  ECDSAP256SHA256 <zonename>`. A key created for zone *A* can be safely used for zone *B*.
+
+## Examples

middleware/dnssec/black_lies.go

@@ -0,0 +1,24 @@
+package dnssec
+
+import "github.com/miekg/dns"
+
+// nsec returns an NSEC useful for NXDOMAIN respsones.
+// See https://tools.ietf.org/html/draft-valsorda-dnsop-black-lies-00
+// For example, a request for the non-existing name a.example.com would
+// cause the following NSEC record to be generated:
+//	a.example.com. 3600 IN NSEC \000.a.example.com. ( RRSIG NSEC )
+// This inturn makes every NXDOMAIN answer a NODATA one, don't forget to flip
+// the header rcode to NOERROR.
+func (d Dnssec) nsec(name, zone string, ttl, incep, expir uint32) ([]dns.RR, error) {
+	nsec := &dns.NSEC{}
+	nsec.Hdr = dns.RR_Header{Name: name, Ttl: ttl, Class: dns.ClassINET, Rrtype: dns.TypeNSEC}
+	nsec.NextDomain = "\\000." + name
+	nsec.TypeBitMap = []uint16{dns.TypeRRSIG, dns.TypeNSEC}
+
+	sigs, err := d.sign([]dns.RR{nsec}, zone, ttl, incep, expir)
+	if err != nil {
+		return nil, err
+	}
+
+	return append(sigs, nsec), nil
+}

middleware/dnssec/black_lies_test.go

@@ -0,0 +1,50 @@
+package dnssec
+
+import (
+	"testing"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/test"
+
+	"github.com/miekg/dns"
+)
+
+func TestZoneSigningBlackLies(t *testing.T) {
+	d, rm1, rm2 := newDnssec(t, []string{"miek.nl."})
+	defer rm1()
+	defer rm2()
+
+	m := testNxdomainMsg()
+	state := middleware.State{Req: m}
+	m = d.Sign(state, "miek.nl.", time.Now().UTC())
+	if !section(m.Ns, 2) {
+		t.Errorf("authority section should have 2 sig")
+	}
+	var nsec *dns.NSEC
+	for _, r := range m.Ns {
+		if r.Header().Rrtype == dns.TypeNSEC {
+			nsec = r.(*dns.NSEC)
+		}
+	}
+	if m.Rcode != dns.RcodeSuccess {
+		t.Errorf("expected rcode %d, got %d", dns.RcodeSuccess, m.Rcode)
+	}
+	if nsec == nil {
+		t.Fatalf("expected NSEC, got none")
+	}
+	if nsec.Hdr.Name != "ww.miek.nl." {
+		t.Errorf("expected %s, got %s", "ww.miek.nl.", nsec.Hdr.Name)
+	}
+	if nsec.NextDomain != "\\000.ww.miek.nl." {
+		t.Errorf("expected %s, got %s", "\\000.ww.miek.nl.", nsec.NextDomain)
+	}
+	t.Logf("%+v\n", m)
+}
+
+func testNxdomainMsg() *dns.Msg {
+	return &dns.Msg{MsgHdr: dns.MsgHdr{Rcode: dns.RcodeNameError},
+		Question: []dns.Question{dns.Question{Name: "ww.miek.nl.", Qclass: dns.ClassINET, Qtype: dns.TypeTXT}},
+		Ns: []dns.RR{test.SOA("miek.nl.	1800	IN	SOA	linode.atoom.net. miek.miek.nl. 1461471181 14400 3600 604800 14400")},
+	}
+}

middleware/dnssec/cache.go

@@ -0,0 +1,23 @@
+package dnssec
+
+import (
+	"hash/fnv"
+	"strconv"
+
+	"github.com/miekg/dns"
+)
+
+// Key serializes the RRset and return a signature cache key.
+func key(rrs []dns.RR) string {
+	h := fnv.New64()
+	buf := make([]byte, 256)
+	for _, r := range rrs {
+		off, err := dns.PackRR(r, buf, 0, nil, false)
+		if err == nil {
+			h.Write(buf[:off])
+		}
+	}
+
+	i := h.Sum64()
+	return strconv.FormatUint(i, 10)
+}

middleware/dnssec/cache_test.go

@@ -0,0 +1,32 @@
+package dnssec
+
+import (
+	"testing"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/test"
+)
+
+func TestCacheSet(t *testing.T) {
+	fPriv, rmPriv, _ := test.TempFile(t, ".", privKey)
+	fPub, rmPub, _ := test.TempFile(t, ".", pubKey)
+	defer rmPriv()
+	defer rmPub()
+
+	dnskey, err := ParseKeyFile(fPub, fPriv)
+	if err != nil {
+		t.Fatalf("failed to parse key: %v\n", err)
+	}
+
+	m := testMsg()
+	state := middleware.State{Req: m}
+	k := key(m.Answer) // calculate *before* we add the sig
+	d := NewDnssec([]string{"miek.nl."}, []*DNSKEY{dnskey}, nil)
+	m = d.Sign(state, "miek.nl.", time.Now().UTC())
+
+	_, ok := d.get(k)
+	if !ok {
+		t.Errorf("signature was not added to the cache")
+	}
+}

middleware/dnssec/dnskey.go

@@ -0,0 +1,71 @@
+package dnssec
+
+import (
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/rsa"
+	"errors"
+	"os"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+
+	"github.com/miekg/dns"
+)
+
+type DNSKEY struct {
+	K      *dns.DNSKEY
+	s      crypto.Signer
+	keytag uint16
+}
+
+// ParseKeyFile read a DNSSEC keyfile as generated by dnssec-keygen or other
+// utilities. It adds ".key" for the public key and ".private" for the private key.
+func ParseKeyFile(pubFile, privFile string) (*DNSKEY, error) {
+	f, e := os.Open(pubFile)
+	if e != nil {
+		return nil, e
+	}
+	k, e := dns.ReadRR(f, pubFile)
+	if e != nil {
+		return nil, e
+	}
+
+	f, e = os.Open(privFile)
+	if e != nil {
+		return nil, e
+	}
+	p, e := k.(*dns.DNSKEY).ReadPrivateKey(f, privFile)
+	if e != nil {
+		return nil, e
+	}
+
+	if v, ok := p.(*rsa.PrivateKey); ok {
+		return &DNSKEY{k.(*dns.DNSKEY), v, k.(*dns.DNSKEY).KeyTag()}, nil
+	}
+	if v, ok := p.(*ecdsa.PrivateKey); ok {
+		return &DNSKEY{k.(*dns.DNSKEY), v, k.(*dns.DNSKEY).KeyTag()}, nil
+	}
+	return &DNSKEY{k.(*dns.DNSKEY), nil, 0}, errors.New("no known? private key found")
+}
+
+// getDNSKEY returns the correct DNSKEY to the client. Signatures are added when do is true.
+func (d Dnssec) getDNSKEY(state middleware.State, zone string, do bool) *dns.Msg {
+	keys := make([]dns.RR, len(d.keys))
+	for i, k := range d.keys {
+		keys[i] = dns.Copy(k.K)
+		keys[i].Header().Name = zone
+	}
+	m := new(dns.Msg)
+	m.SetReply(state.Req)
+	m.Answer = keys
+	if !do {
+		return m
+	}
+
+	incep, expir := incepExpir(time.Now().UTC())
+	if sigs, err := d.sign(keys, zone, 3600, incep, expir); err == nil {
+		m.Answer = append(m.Answer, sigs...)
+	}
+	return m
+}

middleware/dnssec/dnssec.go

@@ -0,0 +1,127 @@
+package dnssec
+
+import (
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/singleflight"
+
+	"github.com/miekg/dns"
+	gcache "github.com/patrickmn/go-cache"
+)
+
+type Dnssec struct {
+	Next     middleware.Handler
+	zones    []string
+	keys     []*DNSKEY
+	inflight *singleflight.Group
+	cache    *gcache.Cache
+}
+
+func NewDnssec(zones []string, keys []*DNSKEY, next middleware.Handler) Dnssec {
+	return Dnssec{Next: next,
+		zones:    zones,
+		keys:     keys,
+		cache:    gcache.New(defaultDuration, purgeDuration),
+		inflight: new(singleflight.Group),
+	}
+}
+
+// Sign signs the message m. it takes care of negative or nodata responses. It
+// uses NSEC black lies for authenticated denial of existence. Signatures
+// creates will be cached for a short while. By default we sign for 8 days,
+// starting 3 hours ago.
+func (d Dnssec) Sign(state middleware.State, zone string, now time.Time) *dns.Msg {
+	req := state.Req
+	mt, _ := middleware.Classify(req) // TODO(miek): need opt record here?
+	if mt == middleware.Delegation {
+		return req
+	}
+
+	incep, expir := incepExpir(now)
+
+	if mt == middleware.NameError {
+		if req.Ns[0].Header().Rrtype != dns.TypeSOA || len(req.Ns) > 1 {
+			return req
+		}
+
+		ttl := req.Ns[0].Header().Ttl
+
+		if sigs, err := d.sign(req.Ns, zone, ttl, incep, expir); err == nil {
+			req.Ns = append(req.Ns, sigs...)
+		}
+		if sigs, err := d.nsec(state.Name(), zone, ttl, incep, expir); err == nil {
+			req.Ns = append(req.Ns, sigs...)
+		}
+		if len(req.Ns) > 1 { // actually added nsec and sigs, reset the rcode
+			req.Rcode = dns.RcodeSuccess
+		}
+		return req
+	}
+
+	for _, r := range rrSets(req.Answer) {
+		ttl := r[0].Header().Ttl
+		if sigs, err := d.sign(r, zone, ttl, incep, expir); err == nil {
+			req.Answer = append(req.Answer, sigs...)
+		}
+	}
+	for _, r := range rrSets(req.Ns) {
+		ttl := r[0].Header().Ttl
+		if sigs, err := d.sign(r, zone, ttl, incep, expir); err == nil {
+			req.Ns = append(req.Ns, sigs...)
+		}
+	}
+	for _, r := range rrSets(req.Extra) {
+		ttl := r[0].Header().Ttl
+		if sigs, err := d.sign(r, zone, ttl, incep, expir); err == nil {
+			req.Extra = append(req.Extra, sigs...)
+		}
+	}
+	return req
+}
+
+func (d Dnssec) sign(rrs []dns.RR, signerName string, ttl, incep, expir uint32) ([]dns.RR, error) {
+	k := key(rrs)
+	sgs, ok := d.get(k)
+	if ok {
+		return sgs, nil
+	}
+
+	sigs, err := d.inflight.Do(k, func() (interface{}, error) {
+		sigs := make([]dns.RR, len(d.keys))
+		var e error
+		for i, k := range d.keys {
+			sig := k.NewRRSIG(signerName, ttl, incep, expir)
+			e = sig.Sign(k.s, rrs)
+			sigs[i] = sig
+		}
+		d.set(k, sigs)
+		return sigs, e
+	})
+	return sigs.([]dns.RR), err
+}
+
+func (d Dnssec) set(key string, sigs []dns.RR) {
+	// we insert the sigs with a duration that is 24 hours less then the expiration, as these
+	// sigs have *just* been made the duration is 7 days.
+	d.cache.Set(key, sigs, eightDays-24*time.Hour)
+}
+
+func (d Dnssec) get(key string) ([]dns.RR, bool) {
+	if s, ok := d.cache.Get(key); ok {
+		return s.([]dns.RR), true
+	}
+	return nil, false
+}
+
+func incepExpir(now time.Time) (uint32, uint32) {
+	incep := uint32(now.Add(-3 * time.Hour).Unix()) // -(2+1) hours, be sure to catch daylight saving time and such
+	expir := uint32(now.Add(eightDays).Unix())      // sign for 8 days
+	return incep, expir
+}
+
+const (
+	purgeDuration   = 3 * time.Hour
+	defaultDuration = 24 * time.Hour
+	eightDays       = 8 * 24 * time.Hour
+)

middleware/dnssec/dnssec_test.go

@@ -0,0 +1,193 @@
+package dnssec
+
+import (
+	"testing"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/test"
+
+	"github.com/miekg/dns"
+)
+
+func TestZoneSigning(t *testing.T) {
+	d, rm1, rm2 := newDnssec(t, []string{"miek.nl."})
+	defer rm1()
+	defer rm2()
+
+	m := testMsg()
+	state := middleware.State{Req: m}
+
+	m = d.Sign(state, "miek.nl.", time.Now().UTC())
+	if !section(m.Answer, 1) {
+		t.Errorf("answer section should have 1 sig")
+	}
+	if !section(m.Ns, 1) {
+		t.Errorf("authority section should have 1 sig")
+	}
+}
+
+func TestZoneSigningDouble(t *testing.T) {
+	d, rm1, rm2 := newDnssec(t, []string{"miek.nl."})
+	defer rm1()
+	defer rm2()
+
+	fPriv1, rmPriv1, _ := test.TempFile(t, ".", privKey1)
+	fPub1, rmPub1, _ := test.TempFile(t, ".", pubKey1)
+	defer rmPriv1()
+	defer rmPub1()
+
+	key1, err := ParseKeyFile(fPub1, fPriv1)
+	if err != nil {
+		t.Fatalf("failed to parse key: %v\n", err)
+	}
+	d.keys = append(d.keys, key1)
+
+	m := testMsg()
+	state := middleware.State{Req: m}
+	m = d.Sign(state, "miek.nl.", time.Now().UTC())
+	if !section(m.Answer, 2) {
+		t.Errorf("answer section should have 1 sig")
+	}
+	if !section(m.Ns, 2) {
+		t.Errorf("authority section should have 1 sig")
+	}
+	t.Logf("%+v\n", m)
+}
+
+// TestSigningDifferentZone tests if a key for miek.nl and be used for example.org.
+func TestSigningDifferentZone(t *testing.T) {
+	fPriv, rmPriv, _ := test.TempFile(t, ".", privKey)
+	fPub, rmPub, _ := test.TempFile(t, ".", pubKey)
+	defer rmPriv()
+	defer rmPub()
+
+	key, err := ParseKeyFile(fPub, fPriv)
+	if err != nil {
+		t.Fatalf("failed to parse key: %v\n", err)
+	}
+
+	m := testMsgEx()
+	state := middleware.State{Req: m}
+	d := NewDnssec([]string{"example.org."}, []*DNSKEY{key}, nil)
+	m = d.Sign(state, "example.org.", time.Now().UTC())
+	if !section(m.Answer, 1) {
+		t.Errorf("answer section should have 1 sig")
+	}
+	if !section(m.Ns, 1) {
+		t.Errorf("authority section should have 1 sig")
+	}
+	t.Logf("%+v\n", m)
+}
+
+func TestSigningCname(t *testing.T) {
+	d, rm1, rm2 := newDnssec(t, []string{"miek.nl."})
+	defer rm1()
+	defer rm2()
+
+	m := testMsgCname()
+	state := middleware.State{Req: m}
+	m = d.Sign(state, "miek.nl.", time.Now().UTC())
+	if !section(m.Answer, 1) {
+		t.Errorf("answer section should have 1 sig")
+	}
+	t.Logf("%+v\n", m)
+}
+
+func TestZoneSigningDelegation(t *testing.T) {
+	d, rm1, rm2 := newDnssec(t, []string{"miek.nl."})
+	defer rm1()
+	defer rm2()
+
+	m := testDelegationMsg()
+	state := middleware.State{Req: m}
+	m = d.Sign(state, "miek.nl.", time.Now().UTC())
+	if !section(m.Ns, 0) {
+		t.Errorf("authority section should have 0 sig")
+		t.Logf("%v\n", m)
+	}
+	if !section(m.Extra, 0) {
+		t.Errorf("answer section should have 0 sig")
+		t.Logf("%v\n", m)
+	}
+}
+
+func section(rss []dns.RR, nrSigs int) bool {
+	i := 0
+	for _, r := range rss {
+		if r.Header().Rrtype == dns.TypeRRSIG {
+			i++
+		}
+	}
+	return nrSigs == i
+}
+
+func testMsg() *dns.Msg {
+	// don't care about the message header
+	return &dns.Msg{
+		Answer: []dns.RR{test.MX("miek.nl.	1703	IN	MX	1 aspmx.l.google.com.")},
+		Ns: []dns.RR{test.NS("miek.nl.	1703	IN	NS	omval.tednet.nl.")},
+	}
+}
+func testMsgEx() *dns.Msg {
+	return &dns.Msg{
+		Answer: []dns.RR{test.MX("example.org.	1703	IN	MX	1 aspmx.l.google.com.")},
+		Ns: []dns.RR{test.NS("example.org.	1703	IN	NS	omval.tednet.nl.")},
+	}
+}
+
+func testMsgCname() *dns.Msg {
+	return &dns.Msg{
+		Answer: []dns.RR{test.CNAME("www.miek.nl.	1800	IN	CNAME	a.miek.nl.")},
+	}
+}
+
+func testDelegationMsg() *dns.Msg {
+	return &dns.Msg{
+		Ns: []dns.RR{
+			test.NS("miek.nl.	3600	IN	NS	linode.atoom.net."),
+			test.NS("miek.nl.	3600	IN	NS	ns-ext.nlnetlabs.nl."),
+			test.NS("miek.nl.	3600	IN	NS	omval.tednet.nl."),
+		},
+		Extra: []dns.RR{
+			test.A("omval.tednet.nl.	3600	IN	A	185.49.141.42"),
+			test.AAAA("omval.tednet.nl.	3600	IN	AAAA	2a04:b900:0:100::42"),
+		},
+	}
+}
+
+func newDnssec(t *testing.T, zones []string) (Dnssec, func(), func()) {
+	k, rm1, rm2 := newKey(t)
+	d := NewDnssec(zones, []*DNSKEY{k}, nil)
+	return d, rm1, rm2
+}
+
+func newKey(t *testing.T) (*DNSKEY, func(), func()) {
+	fPriv, rmPriv, _ := test.TempFile(t, ".", privKey)
+	fPub, rmPub, _ := test.TempFile(t, ".", pubKey)
+
+	key, err := ParseKeyFile(fPub, fPriv)
+	if err != nil {
+		t.Fatalf("failed to parse key: %v\n", err)
+	}
+	return key, rmPriv, rmPub
+}
+
+const (
+	pubKey  = `miek.nl. IN DNSKEY 257 3 13 0J8u0XJ9GNGFEBXuAmLu04taHG4BXPP3gwhetiOUMnGA+x09nqzgF5IY OyjWB7N3rXqQbnOSILhH1hnuyh7mmA==`
+	privKey = `Private-key-format: v1.3
+Algorithm: 13 (ECDSAP256SHA256)
+PrivateKey: /4BZk8AFvyW5hL3cOLSVxIp1RTqHSAEloWUxj86p3gs=
+Created: 20160423195532
+Publish: 20160423195532
+Activate: 20160423195532
+`
+	pubKey1  = `example.org. IN DNSKEY 257 3 13 tVRWNSGpHZbCi7Pr7OmbADVUO3MxJ0Lb8Lk3o/HBHqCxf5K/J50lFqRa 98lkdAIiFOVRy8LyMvjwmxZKwB5MNw==`
+	privKey1 = `Private-key-format: v1.3
+Algorithm: 13 (ECDSAP256SHA256)
+PrivateKey: i8j4OfDGT8CQt24SDwLz2hg9yx4qKOEOh1LvbAuSp1c=
+Created: 20160423211746
+Publish: 20160423211746
+Activate: 20160423211746
+`
+)

middleware/dnssec/handler.go

@@ -0,0 +1,61 @@
+package dnssec
+
+import (
+	"github.com/miekg/coredns/middleware"
+
+	"github.com/miekg/dns"
+	"github.com/prometheus/client_golang/prometheus"
+	"golang.org/x/net/context"
+)
+
+// ServeDNS implements the middleware.Handler interface.
+func (d Dnssec) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	state := middleware.State{W: w, Req: r}
+
+	do := state.Do()
+	qname := state.Name()
+	qtype := state.QType()
+	zone := middleware.Zones(d.zones).Matches(qname)
+	if zone == "" {
+		return d.Next.ServeDNS(ctx, w, r)
+	}
+
+	// Intercept queries for DNSKEY, but only if one of the zones matches the qname, otherwise we let
+	// the query through.
+	if qtype == dns.TypeDNSKEY {
+		for _, z := range d.zones {
+			if qname == z {
+				resp := d.getDNSKEY(state, z, do)
+				state.SizeAndDo(resp)
+				w.WriteMsg(resp)
+				return dns.RcodeSuccess, nil
+			}
+		}
+	}
+
+	drr := NewDnssecResponseWriter(w, d)
+	return d.Next.ServeDNS(ctx, drr, r)
+}
+
+var (
+	cacheHitCount = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: middleware.Namespace,
+		Subsystem: subsystem,
+		Name:      "hit_count_total",
+		Help:      "Counter of signatures that were found in the cache.",
+	}, []string{"zone"})
+
+	cacheMissCount = prometheus.NewCounterVec(prometheus.CounterOpts{
+		Namespace: middleware.Namespace,
+		Subsystem: subsystem,
+		Name:      "miss_count_total",
+		Help:      "Counter of signatures that were not found in the cache.",
+	}, []string{"zone"})
+)
+
+const subsystem = "dnssec"
+
+func init() {
+	prometheus.MustRegister(cacheHitCount)
+	prometheus.MustRegister(cacheMissCount)
+}

middleware/dnssec/handler_test.go

@@ -0,0 +1,170 @@
+package dnssec
+
+import (
+	"sort"
+	"strings"
+	"testing"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/coredns/middleware/file"
+	"github.com/miekg/coredns/middleware/test"
+
+	"github.com/miekg/dns"
+	"golang.org/x/net/context"
+)
+
+var dnssecTestCases = []test.Case{
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeDNSKEY,
+		Answer: []dns.RR{
+			test.DNSKEY("miek.nl.	3600	IN	DNSKEY	257 3 13 0J8u0XJ9GNGFEBXuAmLu04taHG4"),
+		},
+	},
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeDNSKEY, Do: true,
+		Answer: []dns.RR{
+			test.DNSKEY("miek.nl.	3600	IN	DNSKEY	257 3 13 0J8u0XJ9GNGFEBXuAmLu04taHG4"),
+			test.RRSIG("miek.nl.	3600	IN	RRSIG	DNSKEY 13 2 3600 20160503150844 20160425120844 18512 miek.nl. Iw/kNOyM"),
+		},
+		Extra: []dns.RR{test.OPT(4096, true)},
+	},
+}
+
+var dnsTestCases = []test.Case{
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeDNSKEY,
+		Answer: []dns.RR{
+			test.DNSKEY("miek.nl.	3600	IN	DNSKEY	257 3 13 0J8u0XJ9GNGFEBXuAmLu04taHG4"),
+		},
+	},
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeMX,
+		Answer: []dns.RR{
+			test.MX("miek.nl.	1800	IN	MX	1 aspmx.l.google.com."),
+		},
+	},
+	{
+		Qname: "miek.nl.", Qtype: dns.TypeMX, Do: true,
+		Answer: []dns.RR{
+			test.MX("miek.nl.	1800	IN	MX	1 aspmx.l.google.com."),
+			test.RRSIG("miek.nl.	1800	IN	RRSIG	MX 13 2 3600 20160503192428 20160425162428 18512 miek.nl. 4nxuGKitXjPVA9zP1JIUvA09"),
+		},
+		Extra: []dns.RR{test.OPT(4096, true)},
+	},
+	{
+		Qname: "www.miek.nl.", Qtype: dns.TypeAAAA, Do: true,
+		Answer: []dns.RR{
+			test.AAAA("a.miek.nl.	1800	IN	AAAA	2a01:7e00::f03c:91ff:fef1:6735"),
+			test.RRSIG("a.miek.nl.	1800	IN	RRSIG	AAAA 13 3 3600 20160503193047 20160425163047 18512 miek.nl. UAyMG+gcnoXW3"),
+			test.CNAME("www.miek.nl.	1800	IN	CNAME	a.miek.nl."),
+			test.RRSIG("www.miek.nl.	1800	IN	RRSIG	CNAME 13 3 3600 20160503193047 20160425163047 18512 miek.nl. E3qGZn"),
+		},
+		Extra: []dns.RR{test.OPT(4096, true)},
+	},
+	{
+		Qname: "www.example.org.", Qtype: dns.TypeAAAA, Do: true,
+		Rcode: dns.RcodeServerFailure,
+		// Extra: []dns.RR{test.OPT(4096, true)}, // test.ErrorHandler is a simple handler that does not do EDNS.
+	},
+}
+
+func TestLookupZone(t *testing.T) {
+	zone, err := file.Parse(strings.NewReader(dbMiekNL), "miek.nl.", "stdin")
+	if err != nil {
+		return
+	}
+	fm := file.File{Next: test.ErrorHandler(), Zones: file.Zones{Z: map[string]*file.Zone{"miek.nl.": zone}, Names: []string{"miek.nl."}}}
+	dnskey, rm1, rm2 := newKey(t)
+	defer rm1()
+	defer rm2()
+	dh := NewDnssec([]string{"miek.nl."}, []*DNSKEY{dnskey}, fm)
+	ctx := context.TODO()
+
+	for _, tc := range dnsTestCases {
+		m := tc.Msg()
+
+		rec := middleware.NewResponseRecorder(&test.ResponseWriter{})
+		_, err := dh.ServeDNS(ctx, rec, m)
+		if err != nil {
+			t.Errorf("expected no error, got %v\n", err)
+			return
+		}
+		resp := rec.Msg()
+
+		sort.Sort(test.RRSet(resp.Answer))
+		sort.Sort(test.RRSet(resp.Ns))
+		sort.Sort(test.RRSet(resp.Extra))
+
+		if !test.Header(t, tc, resp) {
+			t.Logf("%v\n", resp)
+			continue
+		}
+		if !test.Section(t, tc, test.Answer, resp.Answer) {
+			t.Logf("%v\n", resp)
+		}
+		if !test.Section(t, tc, test.Ns, resp.Ns) {
+			t.Logf("%v\n", resp)
+		}
+		if !test.Section(t, tc, test.Extra, resp.Extra) {
+			t.Logf("%v\n", resp)
+		}
+	}
+}
+
+func TestLookupDNSKEY(t *testing.T) {
+	dnskey, rm1, rm2 := newKey(t)
+	defer rm1()
+	defer rm2()
+	dh := NewDnssec([]string{"miek.nl."}, []*DNSKEY{dnskey}, test.ErrorHandler())
+	ctx := context.TODO()
+
+	for _, tc := range dnssecTestCases {
+		m := tc.Msg()
+
+		rec := middleware.NewResponseRecorder(&test.ResponseWriter{})
+		_, err := dh.ServeDNS(ctx, rec, m)
+		if err != nil {
+			t.Errorf("expected no error, got %v\n", err)
+			return
+		}
+		resp := rec.Msg()
+
+		sort.Sort(test.RRSet(resp.Answer))
+		sort.Sort(test.RRSet(resp.Ns))
+		sort.Sort(test.RRSet(resp.Extra))
+
+		if !test.Header(t, tc, resp) {
+			t.Logf("%v\n", resp)
+			continue
+		}
+		if !test.Section(t, tc, test.Answer, resp.Answer) {
+			t.Logf("%v\n", resp)
+		}
+		if !test.Section(t, tc, test.Ns, resp.Ns) {
+			t.Logf("%v\n", resp)
+		}
+		if !test.Section(t, tc, test.Extra, resp.Extra) {
+			t.Logf("%v\n", resp)
+		}
+	}
+}
+
+const dbMiekNL = `
+$TTL    30M
+$ORIGIN miek.nl.
+@       IN      SOA     linode.atoom.net. miek.miek.nl. (
+                             1282630057 ; Serial
+                             4H         ; Refresh
+                             1H         ; Retry
+                             7D         ; Expire
+                             4H )       ; Negative Cache TTL
+                IN      NS      linode.atoom.net.
+
+                IN      MX      1  aspmx.l.google.com.
+
+                IN      A       139.162.196.78
+                IN      AAAA    2a01:7e00::f03c:91ff:fef1:6735
+
+a               IN      A       139.162.196.78
+                IN      AAAA    2a01:7e00::f03c:91ff:fef1:6735
+www             IN      CNAME   a`

middleware/dnssec/responsewriter.go

@@ -0,0 +1,48 @@
+package dnssec
+
+import (
+	"log"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
+	"github.com/miekg/dns"
+)
+
+type DnssecResponseWriter struct {
+	dns.ResponseWriter
+	d Dnssec
+}
+
+func NewDnssecResponseWriter(w dns.ResponseWriter, d Dnssec) *DnssecResponseWriter {
+	return &DnssecResponseWriter{w, d}
+}
+
+func (d *DnssecResponseWriter) WriteMsg(res *dns.Msg) error {
+	// By definition we should sign anything that comes back, we should still figure out for
+	// which zone it should be.
+	state := middleware.State{W: d.ResponseWriter, Req: res}
+
+	qname := state.Name()
+	zone := middleware.Zones(d.d.zones).Matches(qname)
+	if zone == "" {
+		return d.ResponseWriter.WriteMsg(res)
+	}
+
+	if state.Do() {
+		res = d.d.Sign(state, zone, time.Now().UTC())
+	}
+	state.SizeAndDo(res)
+
+	return d.ResponseWriter.WriteMsg(res)
+}
+
+func (d *DnssecResponseWriter) Write(buf []byte) (int, error) {
+	log.Printf("[WARNING] Dnssec called with Write: not signing reply")
+	n, err := d.ResponseWriter.Write(buf)
+	return n, err
+}
+
+func (d *DnssecResponseWriter) Hijack() {
+	d.ResponseWriter.Hijack()
+	return
+}

middleware/dnssec/rrsig.go

@@ -0,0 +1,53 @@
+package dnssec
+
+import "github.com/miekg/dns"
+
+// newRRSIG return a new RRSIG, with all fields filled out, except the signed data.
+func (k *DNSKEY) NewRRSIG(signerName string, ttl, incep, expir uint32) *dns.RRSIG {
+	sig := new(dns.RRSIG)
+
+	sig.Hdr.Rrtype = dns.TypeRRSIG
+	sig.Algorithm = k.K.Algorithm
+	sig.KeyTag = k.keytag
+	sig.SignerName = signerName
+	sig.Hdr.Ttl = ttl
+	sig.OrigTtl = origTtl
+
+	sig.Inception = incep
+	sig.Expiration = expir
+
+	return sig
+}
+
+type rrset struct {
+	qname string
+	qtype uint16
+}
+
+// rrSets returns rrs as a map of RRsets. It skips RRSIG and OPT records as those don't need to be signed.
+func rrSets(rrs []dns.RR) map[rrset][]dns.RR {
+	m := make(map[rrset][]dns.RR)
+
+	for _, r := range rrs {
+		if r.Header().Rrtype == dns.TypeRRSIG || r.Header().Rrtype == dns.TypeOPT {
+			continue
+		}
+
+		if s, ok := m[rrset{r.Header().Name, r.Header().Rrtype}]; ok {
+			s = append(s, r)
+			m[rrset{r.Header().Name, r.Header().Rrtype}] = s
+			continue
+		}
+
+		s := make([]dns.RR, 1, 3)
+		s[0] = r
+		m[rrset{r.Header().Name, r.Header().Rrtype}] = s
+	}
+
+	if len(m) > 0 {
+		return m
+	}
+	return nil
+}
+
+const origTtl = 3600

middleware/etcd/etcd.go

@@ -8,8 +8,8 @@ import (
 
 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/etcd/msg"
-	"github.com/miekg/coredns/middleware/etcd/singleflight"
 	"github.com/miekg/coredns/middleware/proxy"
+	"github.com/miekg/coredns/middleware/singleflight"
 
 	etcdc "github.com/coreos/etcd/client"
 	"golang.org/x/net/context"

middleware/etcd/lookup.go

@@ -317,11 +317,14 @@ func (e Etcd) NS(zone string, state middleware.State) (records, extra []dns.RR,
 	// NS record for this zone live in a special place, ns.dns.<zone>. Fake our lookup.
 	// only a tad bit fishy...
 	old := state.QName()
+
+	state.Clear()
 	state.Req.Question[0].Name = "ns.dns." + zone
 	services, err := e.records(state, false)
 	if err != nil {
 		return nil, nil, err
 	}
+	// ... and reset
 	state.Req.Question[0].Name = old
 
 	for _, serv := range services {

middleware/etcd/setup_test.go

@@ -10,8 +10,8 @@ import (
 
 	"github.com/miekg/coredns/middleware"
 	"github.com/miekg/coredns/middleware/etcd/msg"
-	"github.com/miekg/coredns/middleware/etcd/singleflight"
 	"github.com/miekg/coredns/middleware/proxy"
+	"github.com/miekg/coredns/middleware/singleflight"
 	"github.com/miekg/coredns/middleware/test"
 	"github.com/miekg/dns"
 

middleware/file/closest.go

@@ -52,6 +52,10 @@ func (z *Zone) nameErrorProof(qname string, qtype uint16) []dns.RR {
 		}
 	}
 
+	if len(nsec) == 0 || len(nsec1) == 0 {
+		return nsec
+	}
+
 	// Check for duplicate NSEC.
 	if nsec[nsecIndex].Header().Name == nsec1[nsec1Index].Header().Name &&
 		nsec[nsecIndex].(*dns.NSEC).NextDomain == nsec1[nsec1Index].(*dns.NSEC).NextDomain {

middleware/file/file.go

@@ -1,7 +1,7 @@
 package file
 
 import (
-	"fmt"
+	"errors"
 	"io"
 	"log"
 
@@ -27,13 +27,16 @@ func (f File) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (i
 	state := middleware.State{W: w, Req: r}
 
 	if state.QClass() != dns.ClassINET {
-		return dns.RcodeServerFailure, fmt.Errorf("can only deal with ClassINET")
+		return dns.RcodeServerFailure, errors.New("can only deal with ClassINET")
 	}
 	qname := state.Name()
 	zone := middleware.Zones(f.Zones.Names).Matches(qname)
 	if zone == "" {
+		if f.Next != nil {
 			return f.Next.ServeDNS(ctx, w, r)
 		}
+		return dns.RcodeServerFailure, errors.New("no next middleware found")
+	}
 	z, ok := f.Zones.Z[zone]
 	if !ok {
 		return f.Next.ServeDNS(ctx, w, r)

middleware/file/reload_test.go

@@ -11,7 +11,7 @@ import (
 )
 
 func TestZoneReload(t *testing.T) {
-	fileName, rm, err := test.Zone(t, ".", reloadZoneTest)
+	fileName, rm, err := test.TempFile(t, ".", reloadZoneTest)
 	if err != nil {
 		t.Fatalf("failed to create zone: %s", err)
 	}

middleware/state.go

@@ -15,9 +15,13 @@ type State struct {
 	Req *dns.Msg
 	W   dns.ResponseWriter
 
-	// Cache size after first call to Size or Do
+	// Cache size after first call to Size or Do.
 	size int
 	do   int // 0: not, 1: true: 2: false
+	// TODO(miek): opt record itself as well.
+
+	// Cache name as (lowercase) well
+	name string
 }
 
 // Now returns the current timestamp in the specified format.
@@ -26,12 +30,6 @@ func (s *State) Now(format string) string { return time.Now().Format(format) }
 // NowDate returns the current date/time that can be used in other time functions.
 func (s *State) NowDate() time.Time { return time.Now() }
 
-// Header gets the heaser of the request in State.
-func (s *State) Header() *dns.RR_Header {
-	// TODO(miek)
-	return nil
-}
-
 // IP gets the (remote) IP address of the client making the request.
 func (s *State) IP() string {
 	ip, _, err := net.SplitHostPort(s.W.RemoteAddr().String())
@@ -191,7 +189,13 @@ func (s *State) QType() uint16 { return s.Req.Question[0].Qtype }
 
 // Name returns the name of the question in the request. Note
 // this name will always have a closing dot and will be lower cased.
-func (s *State) Name() string { return strings.ToLower(dns.Name(s.Req.Question[0].Name).String()) }
+func (s *State) Name() string {
+	if s.name != "" {
+		return s.name
+	}
+	s.name = strings.ToLower(dns.Name(s.Req.Question[0].Name).String())
+	return s.name
+}
 
 // QName returns the name of the question in the request.
 func (s *State) QName() string { return dns.Name(s.Req.Question[0].Name).String() }
@@ -210,6 +214,11 @@ func (s *State) ErrorMessage(rcode int) *dns.Msg {
 	return m
 }
 
+// Clear clears all caching from State s.
+func (s *State) Clear() {
+	s.name = ""
+}
+
 const (
 	doTrue  = 1
 	doFalse = 2

middleware/test/file.go

@@ -0,0 +1,20 @@
+package test
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+// TempFile will create a temporary file on disk and returns the name and a cleanup function to remove it later.
+func TempFile(t *testing.T, dir, content string) (string, func(), error) {
+	f, err := ioutil.TempFile(dir, "go-test-tmpfile")
+	if err != nil {
+		return "", nil, err
+	}
+	if err := ioutil.WriteFile(f.Name(), []byte(content), 0644); err != nil {
+		return "", nil, err
+	}
+	rmFunc := func() { os.Remove(f.Name()) }
+	return f.Name(), rmFunc, nil
+}

middleware/test/helpers.go

@@ -56,6 +56,7 @@ func TXT(rr string) *dns.TXT     { r, _ := dns.NewRR(rr); return r.(*dns.TXT) }
 func MX(rr string) *dns.MX         { r, _ := dns.NewRR(rr); return r.(*dns.MX) }
 func RRSIG(rr string) *dns.RRSIG   { r, _ := dns.NewRR(rr); return r.(*dns.RRSIG) }
 func NSEC(rr string) *dns.NSEC     { r, _ := dns.NewRR(rr); return r.(*dns.NSEC) }
+func DNSKEY(rr string) *dns.DNSKEY { r, _ := dns.NewRR(rr); return r.(*dns.DNSKEY) }
 
 func OPT(bufsize int, do bool) *dns.OPT {
 	o := new(dns.OPT)

middleware/test/zone.go

@@ -1,21 +0,0 @@
-package test
-
-import (
-	"io/ioutil"
-	"os"
-	"testing"
-)
-
-// Zone will create a temporary file on disk and returns the name and
-// cleanup function to remove it later.
-func Zone(t *testing.T, dir, zonefile string) (string, func(), error) {
-	f, err := ioutil.TempFile(dir, "go-test-zone")
-	if err != nil {
-		return "", nil, err
-	}
-	if err := ioutil.WriteFile(f.Name(), []byte(zonefile), 0644); err != nil {
-		return "", nil, err
-	}
-	rmFunc := func() { os.Remove(f.Name()) }
-	return f.Name(), rmFunc, nil
-}

test/proxy_test.go

@@ -21,7 +21,7 @@ example.org.		IN	A	127.0.0.1
 `
 
 func TestLookupProxy(t *testing.T) {
-	name, rm, err := test.Zone(t, ".", exampleOrg)
+	name, rm, err := test.TempFile(t, ".", exampleOrg)
 	if err != nil {
 		t.Fatalf("failed to created zone: %s", err)
 	}