wip

Author: qdm12

pkg/dnssec/chain.go

@@ -0,0 +1,235 @@
+package dnssec
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/miekg/dns"
+	"github.com/qdm12/dns/v2/internal/server"
+)
+
+// delegationChain is the DNSSEC chain of trust from the
+// queried zone to the root (.) zone.
+// See https://www.ietf.org/rfc/rfc4033.txt
+type delegationChain []*signedZone
+
+// newDelegationChain queries the RRs required for the zone validation.
+// It begins the queries at the desired zone and then go
+// up the delegation tree until it reaches the root zone.
+// It returns a new delegation chain of signed zones where the
+// first signed zone (index 0) is the child zone and the last signed
+// zone is the root zone.
+func newDelegationChain(ctx context.Context, exchange server.Exchange,
+	zone string, qClass uint16) (chain delegationChain, err error) {
+	zoneParts := strings.Split(zone, ".")
+	chain = make(delegationChain, len(zoneParts))
+
+	type result struct {
+		i          int
+		signedZone *signedZone
+		err        error
+	}
+	results := make(chan result)
+
+	for i := range zoneParts {
+		// 'example.com.', 'com.', '.'
+		go func(i int, results chan<- result) {
+			result := result{i: i}
+			zoneName := dns.Fqdn(strings.Join(zoneParts[i:], "."))
+			result.signedZone, result.err = queryDelegation(ctx, exchange, zoneName, qClass)
+			if result.err != nil {
+				result.err = fmt.Errorf("querying delegation for %s: %w", zoneName, result.err)
+			}
+			results <- result
+		}(i, results)
+	}
+
+	for range chain {
+		result := <-results
+		if result.err != nil && err == nil {
+			err = result.err
+			continue
+		}
+		chain[result.i] = result.signedZone
+	}
+	close(results)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return chain, nil
+}
+
+// queryDelegation obtains the DNSKEY records and the DS
+// records for a given zone. It does not query the
+// (non existent) DS record for the root zone.
+func queryDelegation(ctx context.Context, exchange server.Exchange,
+	zone string, qClass uint16) (sz *signedZone, err error) {
+	if zone == "." {
+		// Only query DNSKEY since root zone has no DS record.
+		rrsig, rrset, err := queryDNSKey(ctx, exchange, zone, qClass)
+		if err != nil {
+			return nil, fmt.Errorf("querying DNSKEY records: %w", err)
+		}
+		return &signedZone{
+			zone:           zone,
+			dnsKeyRRSig:    rrsig,
+			dnsKeyRRSet:    rrset,
+			keyTagToDNSKey: dnsKeyRRSetToMap(rrset),
+		}, nil
+	}
+
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	type result struct {
+		t     uint16
+		rrsig *dns.RRSIG
+		rrset []dns.RR
+		err   error
+	}
+	results := make(chan result)
+
+	go func(ctx context.Context, exchange server.Exchange, zone string, results chan<- result) {
+		result := result{t: dns.TypeDNSKEY}
+		result.rrsig, result.rrset, result.err = queryDNSKey(ctx, exchange, zone, qClass)
+		if result.err != nil {
+			result.err = fmt.Errorf("querying DNSKEY records: %w", result.err)
+		}
+		results <- result
+	}(ctx, exchange, zone, results)
+
+	go func(ctx context.Context, exchange server.Exchange, zone string, results chan<- result) {
+		result := result{t: dns.TypeDS}
+		result.rrsig, result.rrset, result.err = queryDS(ctx, exchange, zone, qClass)
+		if result.err != nil {
+			result.err = fmt.Errorf("querying DS records: %w", result.err)
+		}
+		results <- result
+	}(ctx, exchange, zone, results)
+
+	sz = &signedZone{
+		zone: zone,
+	}
+	for i := 0; i < 2; i++ {
+		result := <-results
+		if result.err != nil {
+			if err == nil { // first error encountered
+				err = result.err
+				cancel()
+			}
+			continue
+		}
+		if result.t == dns.TypeDS {
+			sz.dsRRSig, sz.dsRRSet = result.rrsig, result.rrset
+		} else {
+			sz.dnsKeyRRSig, sz.dnsKeyRRSet = result.rrsig, result.rrset
+			sz.keyTagToDNSKey = dnsKeyRRSetToMap(result.rrset)
+		}
+	}
+	close(results)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return sz, nil
+}
+
+var (
+	ErrRecordNotFound = errors.New("record not found")
+	ErrRRSigNotFound  = errors.New("RRSIG not found")
+)
+
+func queryDNSKey(ctx context.Context, exchange server.Exchange,
+	zone string, qClass uint16) (rrsig *dns.RRSIG,
+	rrset []dns.RR, err error) {
+	rrsig, rrset, err = fetchRRSetWithRRSig(ctx, exchange, zone, qClass, dns.TypeDNSKEY)
+	switch {
+	case err != nil:
+		return nil, nil, err
+	case len(rrset) == 0:
+		return nil, nil, fmt.Errorf("%w", ErrRecordNotFound)
+	case rrsig == nil:
+		return nil, nil, fmt.Errorf("%w", ErrRRSigNotFound)
+	}
+	return rrsig, rrset, nil
+}
+
+func queryDS(ctx context.Context, exchange server.Exchange,
+	zone string, qClass uint16) (rrsig *dns.RRSIG,
+	rrset []dns.RR, err error) {
+	rrsig, rrset, err = fetchRRSetWithRRSig(ctx, exchange, zone, qClass, dns.TypeDS)
+	switch {
+	case err != nil:
+		return nil, nil, err
+	case len(rrset) == 0:
+		return nil, nil, fmt.Errorf("%w", ErrRecordNotFound)
+	case rrsig == nil:
+		return nil, nil, fmt.Errorf("%w", ErrRRSigNotFound)
+	}
+	return rrsig, rrset, nil
+}
+
+var (
+	ErrRRSetValidation = errors.New("RRSet validation failed")
+)
+
+// verify uses the zone data in the signed zone and its parent signed zones
+// to validate the DNSSEC chain of trust.
+// It starts the verification in the RRSet supplied as parameter (verifies
+// the RRSIG on the answer RRs), and, assuming a signature is correct and
+// valid, it walks through the linked list of signed zones checking the RRSIGs on
+// the DNSKEY and DS resource record sets, as well as correctness of each
+// delegation using the lower level methods in signedZone.
+func (dc delegationChain) verify(rrsig *dns.RRSIG, rrset []dns.RR) error {
+	if rrsig == nil {
+		return ErrRRSigNotFound
+	}
+
+	signedZone := dc[0] // child desired zone
+
+	// Verify desired RRSet
+	err := signedZone.verifyRRSIG(rrsig, rrset)
+	if err != nil {
+		return fmt.Errorf("for zone %s and RRSIG key tag %d: %w",
+			signedZone.zone, rrsig.KeyTag, err)
+	}
+
+	for i, signedZone := range dc {
+		// Verify DNSKEY signature
+		err := signedZone.verifyRRSIG(signedZone.dnsKeyRRSig, signedZone.dnsKeyRRSet)
+		if err != nil {
+			return fmt.Errorf("for zone %s and RRSIG key tag %d: %w",
+				signedZone.zone, signedZone.dsRRSig.KeyTag, err)
+		}
+
+		if signedZone.zone == "." { // last element in chain
+			err = verifyRootSignedZone(signedZone)
+			if err != nil {
+				return fmt.Errorf("failed validating root zone: %w", err)
+			}
+
+			break
+		}
+
+		// Verify DS signature with parent zone DNSKEY
+		parentSignedZone := dc[i+1]
+		err = parentSignedZone.verifyRRSIG(signedZone.dsRRSig, signedZone.dsRRSet)
+		if err != nil {
+			return fmt.Errorf("for zone %s and RRSIG key tag %d: %w",
+				signedZone.zone, signedZone.dsRRSig.KeyTag, ErrRRSetValidation)
+		}
+
+		// Verify DS hash
+		err = signedZone.verifyDSRRSet()
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

pkg/dnssec/ds.go

@@ -0,0 +1,30 @@
+package dnssec
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/miekg/dns"
+)
+
+var (
+	ErrInvalidDS           = errors.New("DS RR record does not match DNS key")
+	ErrUnknownDsDigestType = errors.New("unknown DS digest type")
+)
+
+func verifyDS(receivedDS *dns.DS, dnsKey *dns.DNSKEY) error {
+	calculatedDS := dnsKey.ToDS(receivedDS.DigestType)
+	if calculatedDS == nil {
+		return fmt.Errorf("%w: %s", ErrUnknownDsDigestType,
+			dns.HashToString[receivedDS.DigestType])
+	}
+
+	if !strings.EqualFold(receivedDS.Digest, calculatedDS.Digest) {
+		return fmt.Errorf("%w: DS record has digest %s "+
+			"but calculated digest is %s", ErrInvalidDS,
+			receivedDS.Digest, calculatedDS.Digest)
+	}
+
+	return nil
+}

pkg/dnssec/integration_test.go

@@ -0,0 +1,132 @@
+//go:build integration
+// +build integration
+
+package dnssec
+
+import (
+	"context"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/miekg/dns"
+	"github.com/qdm12/dns/v2/internal/server"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func getRRSetWithoutValidation(t *testing.T, zone string,
+	qType, qClass uint16) (rrset []dns.RR) {
+	t.Helper()
+
+	request := new(dns.Msg)
+	request.SetQuestion(zone, qType)
+	request.Question[0].Qclass = qClass
+
+	response, _, err := new(dns.Client).Exchange(request, "1.1.1.1:53")
+	require.NoError(t, err)
+
+	// Clear TTL since they are not predicatable
+	for _, rr := range response.Answer {
+		rr.Header().Ttl = 0
+	}
+
+	return response.Answer
+}
+
+func testExchange() server.Exchange {
+	client := &dns.Client{}
+	dialer := &net.Dialer{}
+	return func(ctx context.Context, request *dns.Msg) (response *dns.Msg, err error) {
+		netConn, err := dialer.DialContext(ctx, "udp", "1.1.1.1:53")
+		if err != nil {
+			return nil, err
+		}
+
+		dnsConn := &dns.Conn{Conn: netConn}
+		response, _, err = client.ExchangeWithConn(request, dnsConn)
+
+		_ = dnsConn.Close()
+
+		return response, err
+	}
+}
+
+func Test_fetchAndValidateZone(t *testing.T) {
+	t.Parallel()
+
+	testCases := map[string]struct {
+		zone       string
+		dnsType    uint16
+		exchange   server.Exchange
+		rrset      []dns.RR
+		errWrapped error
+		errMessage string
+	}{
+		"valid DNSSEC": {
+			zone:     "qqq.ninja.",
+			dnsType:  dns.TypeA,
+			rrset:    getRRSetWithoutValidation(t, "qqq.ninja.", dns.TypeA, dns.ClassINET),
+			exchange: testExchange(),
+		},
+		"www.iana.org.": {
+			zone:     "vip.icann.org.",
+			dnsType:  dns.TypeA,
+			exchange: testExchange(),
+		},
+		"no DNSSEC": {
+			zone:     "github.com.",
+			dnsType:  dns.TypeA,
+			rrset:    getRRSetWithoutValidation(t, "github.com.", dns.TypeA, dns.ClassINET),
+			exchange: testExchange(),
+		},
+		"bad DNSSEC already failed by upstream": {
+			zone:       "dnssec-failed.org.",
+			dnsType:    dns.TypeA,
+			exchange:   testExchange(),
+			errWrapped: ErrValidationFailedUpstream,
+			errMessage: "cannot fetch desired RRSet and RRSig: " +
+				"for dnssec-failed.org. IN A: " +
+				"DNSSEC validation might had failed upstream",
+		},
+	}
+	for name, testCase := range testCases {
+		testCase := testCase
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			deadline, ok := t.Deadline()
+			if !ok {
+				deadline = time.Now().Add(5 * time.Second)
+			}
+
+			ctx, cancel := context.WithDeadline(context.Background(), deadline)
+			defer cancel()
+
+			rrset, err := fetchAndValidateZone(ctx, testCase.exchange,
+				testCase.zone, dns.ClassINET, testCase.dnsType)
+
+			// Remove TTL fields from rrset
+			for i := range rrset {
+				rrset[i].Header().Ttl = 0
+			}
+
+			assert.Equal(t, testCase.rrset, rrset)
+			require.ErrorIs(t, err, testCase.errWrapped)
+			if testCase.errWrapped != nil {
+				assert.EqualError(t, err, testCase.errMessage)
+			}
+		})
+	}
+}
+
+func Benchmark_fetchAndValidateZone(b *testing.B) {
+	ctx := context.Background()
+	const zone = "qqq.ninja."
+	const dnsType = dns.TypeA
+	exchange := testExchange()
+
+	for i := 0; i < b.N; i++ {
+		_, _ = fetchAndValidateZone(ctx, exchange, zone, dns.ClassINET, dnsType)
+	}
+}